JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
Patterning vascular networks in vivo for tissue engineering applications.
Tissue Eng Part C Methods
PUBLISHED: 11-13-2014
Show Abstract
Hide Abstract
The ultimate design of functionally therapeutic engineered tissues and organs will rely on our ability to engineer vasculature that can meet tissue specific metabolic needs. We recently introduced an approach for patterning the formation of functional, spatially organized vascular architectures within engineered tissues in vivo. Here, we now explore the design parameters of this approach and how they impact the vascularization of an engineered tissue construct after implantation. We used micropatterning techniques to organize endothelial cells (ECs) into geometrically defined "cords," which in turn acted as a template after implantation for the guided formation of patterned capillaries integrated with the host tissue. We demonstrated that the diameter of the cords prior to implantation impacts the location and density of the resultant capillary network. Inclusion of mural cells to the vascularization response appears primarily to impact the dynamics of vascularization. We established that clinically relevant endothelial sources such as induced pluripotent stem cell derived ECs (iPS ECs) and human microvascular endothelial cells (HMVECs) can drive vascularization within this system. Finally, we demonstrated the ability to control the juxtaposition of parenchyma with perfused vasculature by implanting cords containing a mixture of both a parenchymal cell type (hepatocytes) and ECs. These findings define important characteristics that will ultimately impact the design of vasculature structures that meet tissue specific needs.
Related JoVE Video
Retinal microvasculature in Alzheimer's disease.
J. Alzheimers Dis.
PUBLISHED: 10-30-2014
Show Abstract
Hide Abstract
Although cerebral small vessel disease has been implicated in the development of Alzheimer's disease (AD), the cerebral microcirculation is difficult to visualize directly in vivo. As the retina and the brain share similar embryological origin, anatomical features and physiological properties with the cerebral small vessels, the retinal vessels thus offer a unique and easily accessible "window" to study the correlates and consequences of cerebral small vessel diseases in vivo. Retinal microvasculature can now be visualized, quantified and monitored non-invasively using state-of-the-art retinal imaging technology. Recent clinic- and population-based studies have demonstrated a link between retinal vascular changes and dementia, in particular AD, and cerebral small vessel disease. In this review, we summarize the current findings on retinal vascular changes such as retinopathy signs and changes in novel retinal vascular network parameters and retinal vascular caliber with dementia, cognitive dysfunction and cerebral small vessel disease, and discuss possible future research to further evaluate whether retinal vascular imaging might help to elucidate vascular mechanisms contributing to the development of AD and provide additional value in predicting who may be at risk of developing AD.
Related JoVE Video
Differential Alterations of Neocortical GluN Receptor Subunits in Patients with Mixed Subcortical Ischemic Vascular Dementia and Alzheimer's Disease.
J. Alzheimers Dis.
PUBLISHED: 09-28-2014
Show Abstract
Hide Abstract
Background: Glutamatergic deficits are well-established neurochemical findings in Alzheimer's disease (AD) and are thought to underlie both cognitive and behavioral symptoms of the disease. However, it is unclear whether subcortical ischemic vascular dementia (SIVD) and mixed SIVD/AD (MixD) manifest similar changes in the glutamatergic system. Objective: To measure the immunoreactivities of NMDA receptor GluN1, GluN2A, and GluN2B subunits in SIVD and MixD. Methods: Postmortem neocortical tissues from a cohort of well-characterized, longitudinally followed-up patients with SIVD and MixD, together with age-matched controls, were processed for immunoblotting with GluN subunit-specific antibodies. Results: There was a significant reduction of GluN1 only in MixD, while significant increases of GluN2A and GluN2B were found only in SIVD. Furthermore, GluN1 loss and GluN2A/2B upregulation was associated respectively with higher Braak stages and lacunar infarct scores. Conclusions: Our data suggest that the differential alterations of GluN subunits in SIVD and MixD may result from separate, interacting disease processes, and point to the potential utility of glutamatergic approaches for pharmacotherapy.
Related JoVE Video
Mechanically-Stimulated Contraction of Engineered Cardiac Constructs Using a Microcantilever.
IEEE Trans Biomed Eng
PUBLISHED: 09-24-2014
Show Abstract
Hide Abstract
The beating heart undergoes cyclic mechanical and electrical activity during systole and diastole. The interaction between mechanical stimulation and propagation of the depolarization wavefront is important for understanding not just normal sinus rhythm, but also mechanically-induced cardiac arrhythmia. The present study presents a new platform to study mechanoelectrical coupling in a three-dimensional in vitro model of the myocardium. Cardiomyocytes and cardiac fibroblasts are seeded within extracellular matrix proteins and form constructs constrained by microfabricated tissue gauges that provide in situ measurement of contractile function. The microcantilever of an atomic force microscope is indented into the construct at varying magnitudes and frequencies to cause a coordinated contraction. The results indicate that changes in indentation depth and frequency do not significantly affect the magnitude of contraction, but increasing indentation frequency significantly increases the contractile velocity. Overall, the present study demonstrates the validity of this platform as a means to study mechanoelectrical coupling in a three-dimensional setting, and to investigate the mechanism underlying mechanically-stimulated contraction.
Related JoVE Video
iTRAQ Quantitative Clinical Proteomics Revealed Role of Na(+)K(+)-ATPase and Its Correlation with Deamidation in Vascular Dementia.
J. Proteome Res.
PUBLISHED: 09-02-2014
Show Abstract
Hide Abstract
Dementia is a major public health burden characterized by impaired cognition and loss of function. There are limited treatment options due to inadequate understanding of its pathophysiology and underlying causative mechanisms. Discovery-driven iTRAQ-based quantitative proteomics techniques were applied on frozen brain samples to profile the proteome from vascular dementia (VaD) and age-matched nondementia controls to elucidate the perturbed pathways contributing to pathophysiology of VaD. The iTRAQ quantitative data revealed significant up-regulation of protein-l-isoaspartate O-methyltransferase and sodium-potassium transporting ATPase, while post-translational modification analysis suggested deamidation of catalytic and regulatory subunits of sodium-potassium transporting ATPase. Spontaneous protein deamidation of labile asparagines, generating abnormal l-isoaspartyl residues, is associated with cell aging and dementia due to Alzheimer's disease and may be a cause of neurodegeneration. As ion channel proteins play important roles in cellular signaling processes, alterations in their function by deamidation may lead to perturbations in membrane excitability and neuronal function. Structural modeling of sodium-potassium transporting ATPase revealed the close proximity of these deamidated residues to the catalytic site during E2P confirmation. The deamidated residues may disrupt electrostatic interaction during E1 phosphorylation, which may affect ion transport and signal transduction. Our findings suggest impaired regulation and compromised activity of ion channel proteins contribute to the pathophysiology of VaD.
Related JoVE Video
Short latency cerebellar modulation of the basal ganglia.
Nat. Neurosci.
PUBLISHED: 08-14-2014
Show Abstract
Hide Abstract
The graceful, purposeful motion of our body is an engineering feat that remains unparalleled in robotic devices using advanced artificial intelligence. Much of the information required for complex movements is generated by the cerebellum and the basal ganglia in conjunction with the cortex. Cerebellum and basal ganglia have been thought to communicate with each other only through slow, multi-synaptic cortical loops, begging the question as to how they coordinate their outputs in real time. We found that the cerebellum rapidly modulates the activity of the striatum via a disynaptic pathway in mice. Under physiological conditions, this short latency pathway was capable of facilitating optimal motor control by allowing the basal ganglia to incorporate time-sensitive cerebellar information and by guiding the sign of cortico-striatal plasticity. Conversely, under pathological condition, this pathway relayed aberrant cerebellar activity to the basal ganglia to cause dystonia.
Related JoVE Video
Regional Multiple Pathology Scores Are Associated with Cognitive Decline in Lewy Body Dementias.
Brain Pathol.
PUBLISHED: 08-08-2014
Show Abstract
Hide Abstract
Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are characterized by the presence of ?-synuclein-containing Lewy bodies and Lewy neurites. However, both dementias also show variable degrees of Alzheimer's disease (AD) pathology (senile plaques and neurofibrillary tangles), particularly in areas of the cortex associated with higher cognitive functions. This study investigates the contribution of the individual and combined pathologies in determining the rate of cognitive decline. Cortical ?-synuclein, phosphorylated tau (phosphotau) and A? plaque pathology in 34 PDD and 55 DLB patients was assessed semi-quantitatively in four regions of the neocortex. The decline in cognition, assessed by Mini Mental State Examination, correlated positively with the cortical ?-synuclein load. Patients also had varying degrees of senile A? plaque and phosphotau pathology. Regression analyses pointed to a combined pathology (A? plaque plus phosphotau plus ?-synuclein-positive features), particularly in the prefrontal cortex (BA9) and temporal lobe neocortex with the superior and middle temporal gyrus (BA21, 22), being a major determining factor in the development of dementia. Thus, cognitive decline in Lewy body dementias is not a consequence of ?-synuclein-induced neurodegeneration alone but senile plaque and phosphorylated tau pathology also contribute to the overall deficits.
Related JoVE Video
Modeling and simulations to confirm a controlled hypoglycemic stress test in healthy subjects is not associated with clinically significant QT prolongations.
Int J Clin Pharmacol Ther
PUBLISHED: 08-06-2014
Show Abstract
Hide Abstract
A modified insulin tolerance test (ITT) can be used to simulate a physiological stress state through the induction of controlled hypoglycemia in healthy volunteers. This allows for evaluation of hypothalamic-pituitary-adrenocortical axis response to stress via a surge in cortical release. However, a consequence of severe, prolonged hypoglycemia is QT interval prolongation. The aim of this analysis was to confirm that blood glucose lowering to 60 mg/dL (previously identified as adequate for inducing stress) has low risk of inducing clinically significant QT prolongation.
Related JoVE Video
Forms, forces, and stem cell fate.
Curr. Opin. Cell Biol.
PUBLISHED: 07-29-2014
Show Abstract
Hide Abstract
Cells change their shape and mechanics dramatically during development and tissue healing in response to morphogens, cell-cell contact, adhesion to extracellular matrix, and more. Several regulatory links have been described between cell shape, cytoskeletal tension, matrix adhesiveness and stiffness, and recent studies have begun to uncover how these mechanotransduction pathways can impact transcriptional signaling and cell fate decision. The integrated mechanisms linking cell forces, form and fate are likely critical for driving normal morphogenesis, tissue development, and healing. Dysregulation of these mechanisms may also tip the scale from normal to diseased states. Here, we highlight mechanisms that alter cell shape and mechanics, and the pathways affected by these changes.
Related JoVE Video
Autoantibodies to GM1 and GQ1b? are not Biological Markers of Alzheimer's Disease.
J. Alzheimers Dis.
PUBLISHED: 07-16-2014
Show Abstract
Hide Abstract
A few studies have reported the association of autoantibodies to GM1 or GQ1b? with Alzheimer's disease (AD) or vascular dementia. Here we investigated whether patients with AD or vascular dementia had high titers of the anti-ganglioside antibodies. Sera were obtained from patients with AD (n = 22), vascular dementia (n = 14), Guillain-Barré syndrome, and multifocal motor neuropathy as well as normal controls. Enzyme-linked immunosorbent assay showed titers of IgG and IgM anti-GM1, anti-GQ1b?, and anti-GT1a? antibodies did not differ among AD, vascular dementia, and normal controls, and being remarkably lower than those in Guillain-Barré syndrome and multifocal motor neuropathy. The anti-ganglioside antibodies are not biological markers of AD.
Related JoVE Video
PPAR? signaling mediates the cytotoxicity of DHA in H9c2 cells.
Toxicol. Lett.
PUBLISHED: 07-04-2014
Show Abstract
Hide Abstract
Docosahexaenoic acid (22:6n3, DHA) is an n-3 polyunsaturated fatty acid (PUFA) known to affect numerous biological functions. While DHA possesses many properties that impact cell survival such as suppressing cell growth and inducing apoptosis, the exact molecular and cellular mechanism(s) remain unknown. Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors that regulate many cell pathways including cell death. As DHA acts as a ligand to PPARs the aim of this study was to examine the involvement of PPAR? in DHA-mediated cytotoxicity toward H9c2 cells. Treatment with DHA (100?M) resulted in a significant decline in cell viability, cellular metabolic activity and total antioxidant capacity coinciding with increased total proteasome activities and activity of released lactate dehydrogenase (LDH). No changes in reactive oxygen species (ROS) production or accumulation of lipid peroxidation products were observed but DHA promoted apoptotic cell death as detected by flow cytometry, increased caspase-3 activity and decreased phosphorylation of Akt. Importantly, DHA enhanced PPAR? DNA binding activity in H9c2 cells strongly signifying that the cytotoxic effect of DHA might be mediated via PPAR? signaling. Co-treatment with the selective PPAR? antagonist GSK 3787(1?M) abolished the cytotoxic effects of DHA in H9c2 cells. Cytotoxic effects of DHA were attenuated by co-treatment with myriocin, a selective inhibitor of serine palmitoyl transferase (SPT), preventing de novo ceramide biosynthesis. LC/MS analysis revealed that treatment with DHA resulted in the accumulation of ceramide, which was blocked by GSK 3787. Interestingly, inhibition of cytochrome P450 (CYP) oxidase with MS-PPOH (50?M) abolished DHA-mediated cytotoxicity suggesting downstream metabolites as the active mediators. We further demonstrate that CYP oxidase metabolites of DHA, methyl epoxydocosapentaenoate (EDP methyl esters, 1?M) (mix 1:1:1:1:1:1; 4,5-, 7,8-, 10,11-, 13,14-, 16,17- and 19,20-EDP methyl esters) and 19,20-EDP cause cytotoxicity via activation of PPAR? signaling leading to increased levels of intracellular ceramide. These results illustrate novel pathways for DHA-induced cytotoxicity that suggest an important role for CYP-derived metabolites, EDPs.
Related JoVE Video
An EMMPRIN-?-catenin-Nm23 complex drives ATP production and actomyosin contractility at endothelial junctions.
J. Cell. Sci.
PUBLISHED: 07-02-2014
Show Abstract
Hide Abstract
Cell-cell adhesions are important sites through which cells experience and resist forces. In endothelial cells, these forces regulate junction dynamics and determine endothelial barrier strength. We identify the Ig superfamily member EMMPRIN (also known as basigin) as a coordinator of forces at endothelial junctions. EMMPRIN localization at junctions correlates with endothelial junction strength in different mouse vascular beds. Accordingly, EMMPRIN-deficient mice show altered junctions and increased junction permeability. Lack of EMMPRIN alters the localization and function of VE-cadherin (also known as cadherin-5) by decreasing both actomyosin contractility and tugging forces at endothelial cell junctions. EMMPRIN ensures proper actomyosin-driven maturation of competent endothelial junctions by forming a molecular complex with ?-catenin (also known as junction plakoglobin) and Nm23 (also known as NME1), a nucleoside diphosphate kinase, thereby locally providing ATP to fuel the actomyosin machinery. These results provide a novel mechanism for the regulation of actomyosin contractility at endothelial junctions and might have broader implications in biological contexts such as angiogenesis, collective migration and tissue morphogenesis by coupling compartmentalized energy production to junction assembly.
Related JoVE Video
Tissue-engineered, hydrogel-based endothelial progenitor cell therapy robustly revascularizes ischemic myocardium and preserves ventricular function.
J. Thorac. Cardiovasc. Surg.
PUBLISHED: 06-28-2014
Show Abstract
Hide Abstract
Cell-based angiogenic therapy for ischemic heart failure has had limited clinical impact, likely related to low cell retention (<1%) and dispersion. We developed a novel, tissue-engineered, hydrogel-based cell-delivery strategy to overcome these limitations and provide prolonged regional retention of myocardial endothelial progenitor cells at high cell dosage.
Related JoVE Video
Elevated platelet-derived growth factor AB/BB is associated with a lower risk of recurrent vascular events in stroke patients.
Int J Stroke
PUBLISHED: 06-12-2014
Show Abstract
Hide Abstract
Platelet-derived growth factor (PDGF)-AB and BB have been shown to possess angiogenic properties in vivo, and decreased levels have been linked to plaque instability in atherosclerosis. Little work has been done to determine if PDGF is associated with outcomes after stroke, in particular cognitive outcomes. Therefore, in this sudy, we investigated the association between PDGFand both vascular and cognitive outcomes in a cohort of patients with recent nondisabling ischemic stroke.
Related JoVE Video
Fluid shear stress threshold regulates angiogenic sprouting.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 05-19-2014
Show Abstract
Hide Abstract
The density and architecture of capillary beds that form within a tissue depend on many factors, including local metabolic demand and blood flow. Here, using microfluidic control of local fluid mechanics, we show the existence of a previously unappreciated flow-induced shear stress threshold that triggers angiogenic sprouting. Both intraluminal shear stress over the endothelium and transmural flow through the endothelium above 10 dyn/cm(2) triggered endothelial cells to sprout and invade into the underlying matrix, and this threshold is not impacted by the maturation of cell-cell junctions or pressure gradient across the monolayer. Antagonizing VE-cadherin widened cell-cell junctions and reduced the applied shear stress for a given transmural flow rate, but did not affect the shear threshold for sprouting. Furthermore, both transmural and luminal flow induced expression of matrix metalloproteinase 1, and this up-regulation was required for the flow-induced sprouting. Once sprouting was initiated, continuous flow was needed to both sustain sprouting and prevent retraction. To explore the potential ramifications of a shear threshold on the spatial patterning of new sprouts, we used finite-element modeling to predict fluid shear in a variety of geometric settings and then experimentally demonstrated that transmural flow guided preferential sprouting toward paths of draining interstitial fluid flow as might occur to connect capillary beds to venules or lymphatics. In addition, we show that luminal shear increases in local narrowings of vessels to trigger sprouting, perhaps ultimately to normalize shear stress across the vasculature. Together, these studies highlight the role of shear stress in controlling angiogenic sprouting and offer a potential homeostatic mechanism for regulating vascular density.
Related JoVE Video
A DNA-based molecular probe for optically reporting cellular traction forces.
Nat. Methods
PUBLISHED: 04-24-2014
Show Abstract
Hide Abstract
We developed molecular tension probes (TPs) that report traction forces of adherent cells with high spatial resolution, can in principle be linked to virtually any surface, and obviate monitoring deformations of elastic substrates. TPs consist of DNA hairpins conjugated to fluorophore-quencher pairs that unfold and fluoresce when subjected to specific forces. We applied TPs to reveal that cellular traction forces are heterogeneous within focal adhesions and localized at their distal edges.
Related JoVE Video
Force measurement tools to explore cadherin mechanotransduction.
Cell Commun. Adhes.
PUBLISHED: 04-23-2014
Show Abstract
Hide Abstract
Cell-cell adhesions serve to mechanically couple cells, allowing for long-range transmission of forces across cells in development, disease, and homeostasis. Recent work has shown that such contacts also play a role in transducing mechanical cues into a wide variety of cellular behaviors important to tissue function. As such, understanding the mechanical regulation of cells through their adhesion molecules has become a point of intense focus. This review will highlight the existing and emerging technologies and models that allow for exploration of cadherin-based adhesions as sites of mechanotransduction.
Related JoVE Video
Intracranial Stenosis, Cerebrovascular Diseases, and Cognitive Impairment in Chinese.
Alzheimer Dis Assoc Disord
PUBLISHED: 04-16-2014
Show Abstract
Hide Abstract
Extracranial carotid artery disease has been shown to be related to cognitive deficits. However, limited data are available on intracranial stenosis (ICS) and cognitive impairment. We investigate the association between ICS and cognitive impairment in Chinese. Subjects (n=278), recruited from the Epidemiology of Dementia in Singapore Study, underwent comprehensive clinical evaluation, neuropsychological testing, and brain magnetic resonance imaging (MRI), including 3-dimensional-time-of-flight magnetic resonance angiography (MRA). Cognitive function was expressed as composite and domain-specific Z-scores. Cognitive impairment no dementia and dementia were diagnosed according to internationally accepted diagnostic criteria. Linear and logistic regression models were adjusted for age, sex, education, vascular risk factors, and other MRI markers. A total of 29 (10.4%) persons had ICS on MRA, which was significantly associated with both composite cognitive Z-scores [mean difference in Z-score, presence vs. absence of ICS: -0.37 (95% confidence interval: -0.63, -0.12)] and specific domains including executive function, language, visuomotor speed, verbal memory, and visual memory. ICS was also related to significant cognitive impairment (odds ratio: 5.10 [1.24 to 21.02]). With respect to other MRI markers, adjusted for the presence of lacunar infarcts, the associations of ICS with both composite and domain-specific Z-scores, and significant cognitive impairment became nonsignificant; however, adjustment for other MRI markers did not alter these associations. In this Chinese population, presence of ICS was associated with cognitive impairment independent of vascular risk factors. These associations may be mediated through the presence of infarcts.
Related JoVE Video
Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited).
J Appl Phys
PUBLISHED: 04-15-2014
Show Abstract
Hide Abstract
Contractile forces generated by cells and the stiffness of the surrounding extracellular matrix are two central mechanical factors that regulate cell function. To characterize the dynamic evolution of these two mechanical parameters during tissue morphogenesis, we developed a magnetically actuated micro-mechanical testing system in which fibroblast-populated collagen microtissues formed spontaneously in arrays of microwells that each contains a pair of elastomeric microcantilevers. We characterized the magnetic actuation performance of this system and evaluated its capacity to support long-term cell culture. We showed that cells in the microtissues remained viable during prolonged culture periods of up to 15 days, and that the mechanical properties of the microtissues reached and maintained at a stable state after a fast initial increase stage. Together, these findings demonstrate the utility of this microfabricated bio-magneto-mechanical system in extended mechanobiological studies in a physiologically relevant 3D environment.
Related JoVE Video
Microvascular network alterations in retina of subjects with cerebral small vessel disease.
Neurosci. Lett.
PUBLISHED: 04-13-2014
Show Abstract
Hide Abstract
Novel retinal imaging techniques have enabled the assessment of quantitative vascular parameters, which provide information on the microvasculature before the appearance of retinopathy signs. Advances in neuroimaging have revealed that cerebral microbleeds (CMB) - besides lacunar infarcts and white matter lesions (WML) - may be a novel marker of cerebral small vessel disease. We examine whether quantitative retinal vascular parameters are related to cerebral small vessel disease in a Chinese population. Participants from Epidemiology of Dementia in Singapore Study underwent comprehensive examinations, including 3-Tesla cranial magnetic resonance imaging and retinal-photography. Retinal vascular parameters (caliber, tortuosity, fractal dimension) were measured from photographs using a semi-automated computer-assisted program. Lacunar infarcts and CMB were visually graded. Total brain and WML volume were obtained using a validated segmentation tool. A total of 261 subjects were included, of whom 36 had lacunar infarcts, 29 had severe WML, and 83 had CMB. In age-sex-adjusted models, narrower retinal arteriolar caliber, wider venular caliber and smaller arteriolar fractal dimension were associated with presence of multiple CMB. In contrast, no association was found with lacunar infarcts and WML volume. After multivariate adjustments, associations of venular caliber, arteriolar fractal dimensions and arteriolar tortuosity with CMB remained statistically significant. In conclusion, subjects with early structural changes in retinal microvasculature were more likely to have CMBs, supporting hypothesis that CMB may be an early manifestation of cerebral small vessel disease.
Related JoVE Video
Readmission penalties and health insurance expansions: A dispatch from massachusetts.
J Hosp Med
PUBLISHED: 04-11-2014
Show Abstract
Hide Abstract
Payers are penalizing hospitals for high readmission rates. It is unknown whether major changes in population insurance coverage can affect readmission rates, despite the Affordable Care Act's coverage expansions coming into effect this year.
Related JoVE Video
Jostling for position in angiogenic sprouts: continuous rearrangement of cells explained by differential adhesion dynamics.
EMBO J.
PUBLISHED: 04-07-2014
Show Abstract
Hide Abstract
Endothelial sprouting during angiogenesis is a highly coordinated morphogenetic process that involves polarized tip cells leading stalk cells to form new capillaries. While tip and stalk cells previously were thought to be stable and have static phenotypes within the sprout, it is becoming increasingly clear that endothelial cells undergo dynamic rearrangements. A new study using computer simulations, validated by in vitro and in vivo experimental data, now provides an explanation for these rearrangements, showing that sprouting cells are in a continuum of migratory states, regulated by differential cell-cell adhesions and protrusive activities to drive proper vascular organization.
Related JoVE Video
Seasonality of infection rates after total joint arthroplasty.
Orthopedics
PUBLISHED: 04-01-2014
Show Abstract
Hide Abstract
The correlation between season (fall, winter, spring, and summer) and infection rate in surgical patients is well defined in many specialties. To the authors' knowledge, there are no data in the literature on this phenomenon in patients undergoing total joint arthroplasty. They hypothesized that there would be an increased infection rate in the summer months in patients undergoing elective total joint arthroplasty. They retrospectively reviewed consecutive patients undergoing elective total hip or knee arthroplasty at a single institution during 1 year by a single surgeon. Wound infections were defined as any patient requiring oral antibiotics for cellulitis, readmission for intravenous antibiotics, a return to the operating room for irrigation and debridement, or excisional arthroplasty and placement of a cement spacer within 90 days of the initial procedure. Seventeen of 750 patients developed an infection, for an overall incidence of 2.2%. There was a statistically significant difference in infection rate according to season: 3 (1.5%) infections occurred in winter, 1 (0.5%) in spring, 9 (4.7%) in summer, and 4 (2.4%) in fall. The incidence was highest during July (4.5%), August (5.4%), and September (4.3%). There was a statistically significant difference in infection rate between summer/fall (3.6%) vs winter/spring (1.0%). There is an increase in the incidence of infection during summer months for patients undergoing total joint arthroplasty. The authors recommend increased surveillance and more thorough preoperative sterilization procedures during these warmer months.
Related JoVE Video
Evaluation of the Post Stroke Checklist: a pilot study in the United Kingdom and Singapore.
Int J Stroke
PUBLISHED: 03-31-2014
Show Abstract
Hide Abstract
There is currently no standardized process for long-term follow-up care. As a result, management of poststroke care varies greatly, and the needs of stroke survivors are not fully addressed. The Post Stroke Checklist was developed by the Global Stroke Community Advisory Panel as a means of standardizing long-term stroke care. Since its development, the Post Stroke Checklist has gained international recognition from various stroke networks and is endorsed by the World Stroke Organization to support improved stroke survivor follow-up and care.
Related JoVE Video
Mixed messages: The Blueprint for Pharmacy and a communication gap.
Can Pharm J (Ott)
PUBLISHED: 03-25-2014
Show Abstract
Hide Abstract
More than 5 years ago, the Blueprint for Pharmacy developed a plan for transitioning pharmacy practice toward more patient-centred care. Much of the strategy for change involves communicating the new vision.
Related JoVE Video
Topographical variations of the strain-dependent zonal properties of tibial articular cartilage by microscopic MRI.
Connect. Tissue Res.
PUBLISHED: 03-21-2014
Show Abstract
Hide Abstract
The topographical variations of the zonal properties of canine articular cartilage over the medial tibia were evaluated as the function of external loading by microscopic magnetic resonance imaging (µMRI). T2 and T1 relaxation maps and GAG (glycosaminoglycan) images from a total of 70 specimens were obtained with and without the mechanical loading at 17.6 µm depth resolution. In addition, mechanical modulus and water content were measured from the tissue. For the bulk without loading, the means of T2 at magic angle (43.6 ± 8.1 ms), absolute thickness (907.6 ± 187.9 µm) and water content (63.3 ± 9.3%) on the meniscus-covered area were significantly lower than the means of T2 at magic angle (51.1 ± 8.5 ms), absolute thickness (1251.6 ± 218.4 µm) and water content (73.2 ± 5.6%) on the meniscus-uncovered area. However GAG (86.0 ± 15.3 mg/ml) on the covered area was significantly higher than GAG (70.0 ± 8.8 mg/ml) on the uncovered area. Complex relationships were found in the tissue properties as the function of external loading. The tissue parameters in the superficial zone changed more profoundly than the same properties in the radial zone. The tissue parameters in the meniscus-covered areas changed differently when comparing with the same parameters in the uncovered areas. This project confirms that the load-induced changes in the molecular distribution and structure of cartilage are both depth-dependent and topographically distributed. Such detailed knowledge of the tibial layer could improve the early detection of the subtle softening of the cartilage that will eventually lead to the clinical diseases such as osteoarthritis.
Related JoVE Video
Diagnostic criteria for vascular cognitive disorders: a VASCOG statement.
Alzheimer Dis Assoc Disord
PUBLISHED: 03-18-2014
Show Abstract
Hide Abstract
Several sets of diagnostic criteria have been published for vascular dementia since the 1960s. The continuing ambiguity in vascular dementia definition warrants a critical reexamination.
Related JoVE Video
Baseline characteristics and treatment response of patients from the Philippines in the CHIMES study.
Int J Stroke
PUBLISHED: 03-11-2014
Show Abstract
Hide Abstract
The CHIMES Study compared MLC601 with placebo in patients with ischemic stroke of intermediate severity in the preceding 72?h. Sites from the Philippines randomized 504 of 1099 (46%) patients in the study. We aimed to define the patient characteristics and treatment responses in this subgroup to better plan future trials.
Related JoVE Video
The brain lipidomes of subcortical ischemic vascular dementia and mixed dementia.
Neurobiol. Aging
PUBLISHED: 02-26-2014
Show Abstract
Hide Abstract
Despite its importance as the leading cause of vascular dementia, the primary pathogenic mechanisms in subcortical ischemic vascular dementia (SIVD) have remained elusive. Because of the lack of approved therapeutic agents for SIVD, there is a pressing need to identify novel therapeutic targets. Comparative lipidomic analyses of SIVD and mixed dementia (i.e., SIVD and Alzheimer's disease, MixD) may also confer new insights pertaining to the possible interaction between neurodegenerative and vascular mechanisms in the pathogenesis of dementia. Liquid chromatography coupled to mass spectrometry was used to comprehensively analyze the lipidomes of white and gray matter from the temporal cortex of nondemented controls, SIVD, and MixD subjects. Detailed molecular profiles highlighted the pathologic relevance of gray matter sphingolipid fatty acyl chain heterogeneity in dementia. In addition, the levels of sulfatides and lysobisphosphatidic acids were progressively increased in the temporal cortex gray matter from control to SIVD to MixD. White matter phospholipid profiles indicated possible adaptive mechanisms (i.e., increased unsaturation) to chronic ischemia in SIVD and elevated membrane degradation in MixD.
Related JoVE Video
Microfabrication of a platform to measure and manipulate the mechanics of engineered microtissues.
Methods Cell Biol.
PUBLISHED: 02-25-2014
Show Abstract
Hide Abstract
Engineered tissues can be used to understand fundamental features of biology, develop organotypic in vitro model systems, and as engineered tissue constructs for replacing damaged tissue in vivo. However, a key limitation is an inability to test the wide range of parameters that might impact the engineered tissue in a high-throughput manner and in an environment that mimics the three-dimensional (3D) native architecture. We developed a microfabricated platform to generate arrays of microtissues embedded within 3D micropatterned matrices. Microcantilevers simultaneously constrain microtissue formation and report forces generated by the microtissues in real time, opening the possibility to use high-throughput, low-volume screening for studies on engineered tissues. Thanks to the micrometer scale of the microtissues, this platform is also suitable for high-throughput monitoring of drug-induced effect on architecture and contractility in engineered tissues. Moreover, independent variations of the mechanical stiffness of the cantilevers and collagen matrix allow the measurement and manipulation of the mechanics of the microtissues. Thus, our approach will likely provide valuable opportunities to elucidate how biomechanical, electrical, biochemical, and genetic/epigenetic cues modulate the formation and maturation of 3D engineered tissues. In this chapter, we describe the microfabrication, preparation, and experimental use of such microfabricated tissue gauges.
Related JoVE Video
Force-driven evolution of mesoscale structure in engineered 3D microtissues and the modulation of tissue stiffening.
Biomaterials
PUBLISHED: 02-12-2014
Show Abstract
Hide Abstract
The complex structures of tissues determine their mechanical strength. In engineered tissues formed through self-assembly in a mold, artificially imposed boundary constraints have been found to induce anisotropic clustering of the cells and the extracellular matrix in local regions. To understand how such tissue remodeling at the intermediate length-scale (mesoscale) affects tissue stiffening, we used a novel microtissue mechanical testing system to manipulate the remodeling of the tissue structures and to measure the subsequent changes in tissue stiffness. Microtissues were formed through cell driven self-assembly of collagen matrix in arrays of micro-patterned wells, each containing two flexible micropillars that measured the microtissues' contractile forces and elastic moduli via magnetic actuation. We manipulated tissue remodeling by inducing myofibroblast differentiation with TGF-?1, by varying the micropillar spring constants or by blocking cell contractility with blebbistatin and collagen cross-linking with BAPN. We showed that increased anisotropic compaction of the collagen matrix, caused by increased micropillar spring constant or elevated cell contraction force, contributed to tissue stiffening. Conversely, collagen matrix and tissue stiffness were not affected by inhibition of cell-generated contraction forces. Together, these measurements showed that mesoscale tissue remodeling is an important middle step linking tissue compaction forces and tissue stiffening.
Related JoVE Video
Micropatterned multicolor dynamically adhesive substrates to control cell adhesion and multicellular organization.
Langmuir
PUBLISHED: 01-30-2014
Show Abstract
Hide Abstract
We present a novel technique to examine cell-cell interactions and directed cell migration using micropatterned substrates of three distinct regions: an adhesive region, a nonadhesive region, and a dynamically adhesive region switched by addition of a soluble factor to the medium. Combining microcontact printing with avidin-biotin capture chemistry, we pattern nonadhesive regions of avidin that become adhesive through the capture of biotinylated fibronectin. Our strategy overcomes several limitations of current two-color dynamically adhesive substrates by incorporating a third, permanently nonadhesive region. Having three spatially and functionally distinct regions allows for the realization of more complex configurations of cellular cocultures as well as intricate interface geometries between two cell populations for diverse heterotypic cell-cell interaction studies. We can now achieve spatial control over the path and direction of migration in addition to temporal control of the onset of migration, enabling studies that better recapitulate coordinated multicellular migration and organization in vitro. We confirm that cellular behavior is unaltered on captured biotinylated fibronectin as compared to printed fibronectin by examining the cells' ability to spread, form adhesions, and migrate. We demonstrate the versatility of this approach in studies of migration and cellular cocultures, and further highlight its utility by probing Notch-Delta juxtacrine signaling at a patterned interface.
Related JoVE Video
Ankle-brachial index, cognitive impairment and cerebrovascular disease in a chinese population.
Neuroepidemiology
PUBLISHED: 01-28-2014
Show Abstract
Hide Abstract
Previous studies have assessed the association between ankle-brachial index (ABI) and cognition, mainly using brief cognitive tests. We investigated whether ABI was associated with cognition independent of neuroimaging markers of cerebrovascular disease.
Related JoVE Video
"Stamp-off" to micropattern sparse, multicomponent features.
Methods Cell Biol.
PUBLISHED: 01-21-2014
Show Abstract
Hide Abstract
Spatially patterned subtractive de-inking, a process we term "stamp-off," provides a simple method to generate sparse, multicomponent protein micropatterns. It has been applied to control cell adhesion, study adhesion biology, as well as to micropattern fragile surfaces. This technique can also readily be applied to study nanoscale interactions between cell membrane receptors and surface-immobilized ligands. It is based on conventional microcontact printing and as such requires the same reagents, including photolithographically defined masters, a spin-coater, poly(dimethyl siloxane) (PDMS), and conventional cell culture reagents such as glass coverslips and adhesive proteins. Stamp-off is conceptually simplified into three steps: (1) generation of an appropriate cell culture substrate, PDMS-coated glass, (2) micropatterning with stamp-off, and (3) cell deposition. After elaborating each of these three methods, we discuss limitations of the technique and its applications.
Related JoVE Video
Microvascular network alterations in the retina of patients with Alzheimer's disease.
Alzheimers Dement
PUBLISHED: 01-15-2014
Show Abstract
Hide Abstract
Although cerebral small-vessel disease has been implicated in the development of Alzheimer's disease (AD), the cerebral microcirculation is difficult to visualize directly in vivo. Because the retina provides a noninvasive window to assess the microcirculation, we determined whether quantitatively measured retinal microvascular parameters are associated with AD.
Related JoVE Video
Improving screening for vascular cognitive impairment at three to six months after mild ischemic stroke and transient ischemic attack.
Int Psychogeriatr
PUBLISHED: 01-15-2014
Show Abstract
Hide Abstract
The Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) were compared with and without the addition of a brief processing speed test, the symbol digit modalities test (SDMT), for vascular cognitive impairment (VCI) screening at three to six months after stroke.
Related JoVE Video
Computational and experimental investigation of local stress fiber orientation in uniaxially and biaxially constrained microtissues.
Biomech Model Mechanobiol
PUBLISHED: 01-10-2014
Show Abstract
Hide Abstract
The orientation of cells and associated F-actin stress fibers is essential for proper tissue functioning. We have previously developed a computational model that qualitatively describes stress fiber orientation in response to a range of mechanical stimuli. In this paper, the aim is to quantitatively validate the model in a static, heterogeneous environment. The stress fiber orientation in uniaxially and biaxially constrained microscale tissues was investigated using a recently developed experimental system. Computed and experimental stress fiber orientations were compared, while accounting for changes in orientation with location in the tissue. This allowed for validation of the model, and additionally, it showed how sensitive the stress fiber orientation in the experimental system is to the location where it is measured, i.e., the heterogeneity of the stress fiber orientation. Computed and experimental stress fiber orientations showed good quantitative agreement in most regions. A strong local alignment near the locations where boundary conditions were enforced was observed for both uniaxially and biaxially constrained tissues. Excepting these regions, in biaxially constrained tissues, no preferred orientation was found and the distribution was independent of location. The stress fiber orientation in uniaxially constrained tissues was more heterogeneous, and stress fibers mainly oriented in the constrained direction or along the free edge. These results indicate that the stress fiber orientation in these constrained microtissues is mainly determined by the local mechanical environment, as hypothesized in our model, and also that the model is a valid tool to predict stress fiber orientation in heterogeneously loaded tissues.
Related JoVE Video
Acute slowing of cardiac conduction in response to myofibroblast coupling to cardiomyocytes through N-cadherin.
J. Mol. Cell. Cardiol.
PUBLISHED: 01-09-2014
Show Abstract
Hide Abstract
The electrophysiological consequences of cardiomyocyte and myofibroblast interactions remain unclear, and the contribution of mechanical coupling between these two cell types is still poorly understood. In this study, we examined the time course and mechanisms by which addition of myofibroblasts activated by transforming growth factor-beta (TGF-?) influence the conduction velocity (CV) of neonatal rat ventricular cell monolayers. We observed that myofibroblasts affected CV within 30 min of contact and that these effects were temporally correlated with membrane deformation of cardiomyocytes by the myofibroblasts. Expression of dominant negative RhoA in the myofibroblasts impaired both myofibroblast contraction and myofibroblast-induced slowing of cardiac conduction, whereas overexpression of constitutive RhoA had little effect. To determine the importance of mechanical coupling between these cell types, we examined the expression of the two primary cadherins in the heart (N- and OB-cadherin) at cell-cell contacts formed between myofibroblasts and cardiomyocytes. Although OB-cadherin was frequently found at myofibroblast-myofibroblast contacts, very little expression was observed at myofibroblast-cardiomyocyte contacts. The myofibroblast-induced slowing of cardiac conduction was not prevented by silencing of OB-cadherin in the myofibroblasts, and could be reversed by inhibitors of mechanosensitive channels (gadolinium or streptomycin) and cellular contraction (blebbistatin). In contrast, N-cadherin expression was commonly observed at myofibroblast-cardiomyocyte contacts, and silencing of N-cadherin in myofibroblasts prevented the myofibroblast-dependent slowing of cardiac conduction. We propose that myofibroblasts can impair the electrophysiological function of cardiac tissue through the application of contractile force to the cardiomyocyte membrane via N-cadherin junctions.
Related JoVE Video
Novel pathophysiological markers are revealed by iTRAQ-based quantitative clinical proteomics approach in vascular dementia.
J Proteomics
PUBLISHED: 01-08-2014
Show Abstract
Hide Abstract
Vascular dementia (VaD) is a leading cause of dementia in the elderly together with Alzheimer's disease with limited treatment options. Poor understanding of the pathophysiology underlying VaD is hindering the development of new therapies. Hence, to unravel its underlying molecular pathology, an iTRAQ-2D-LC-MS/MS strategy was used for quantitative analysis of pooled lysates from Brodmann area 21 of pathologically confirmed cases of VaD and matched non-neurological controls. A total of 144 differentially expressed proteins out of 2281 confidently identified proteins (false discovery rate=0.3%) were shortlisted for bioinformatics analysis. Western blot analysis of selected proteins using samples from individual patients (n=10 per group) showed statistically significant increases in the abundance of SOD1 and NCAM and reduced ATP5A in VaD. This suggested a state of hypometabolism and vascular insufficiency along with an inflammatory condition during VaD. Elevation of SOD1 and increasing trend for iron-storage proteins (FTL, FTH1) may be indicative of an oxidative imbalance that is accompanied by an aberrant iron metabolism. The synaptic proteins did not exhibit a generalized decrease in abundance (e.g. syntaxin) in the VaD subjects. This reported proteome offers a reference data set for future basic or translational studies on VaD.
Related JoVE Video
Label-free evaluation of angiogenic sprouting in microengineered devices using ultrahigh-resolution optical coherence microscopy.
J Biomed Opt
PUBLISHED: 01-08-2014
Show Abstract
Hide Abstract
Understanding the mechanism of angiogenesis could help to decipher wound healing and embryonic development and to develop better treatment for diseases such as cancer. Microengineered devices were developed to reveal the mechanisms of angiogenesis, but monitoring the angiogenic process nondestructively in these devices is a challenge. In this study, we utilized a label-free imaging technique, ultrahigh-resolution optical coherence microscopy (OCM), to evaluate angiogenic sprouting in a microengineered device. The OCM system was capable of providing ?1.5-?m axial resolution and ?2.3-?m transverse resolution. Three-dimensional (3-D) distribution of the sprouting vessels in the microengineered device was imaged over 0.6×0.6×0.5??mm3, and details such as vessel lumens and branching points were clearly visualized. An algorithm based on stretching open active contours was developed for tracking and segmenting the sprouting vessels in 3-D-OCM images. The lengths for the first-, second-, and third-order vessels were measured as 127.8±48.8???m (n=8), 67.3±25.9???m (n=9), and 62.5±34.7???m (n=10), respectively. The outer diameters for the first-, second-, and third-order vessels were 13.2±1.0, 8.0±2.1, and 4.4±0.8???m, respectively. These results demonstrate OCM as a promising tool for nondestructive and label-free evaluation of angiogenic sprouting in microengineered devices.
Related JoVE Video
Computer tomography for prediction of cognitive outcomes after ischemic cerebrovascular events.
J Stroke Cerebrovasc Dis
PUBLISHED: 01-07-2014
Show Abstract
Hide Abstract
The aim of this study was to evaluate whether parameters noted on a single, acute computed tomographic (CT) scan, are associated with significant cognitive impairment (SCogI), and can help in the prediction of SCogI 3-6 months after stroke or transient ischemic attack (TIA).
Related JoVE Video
Retinal vascular fractals and cognitive impairment.
Dement Geriatr Cogn Dis Extra
PUBLISHED: 01-01-2014
Show Abstract
Hide Abstract
Retinal microvascular network changes have been found in patients with age-related brain diseases such as stroke and dementia including Alzheimer's disease. We examine whether retinal microvascular network changes are also present in preclinical stages of dementia.
Related JoVE Video
A pilot study to examine the correlation between cognition and blood biomarkers in a Singapore Chinese male cohort with type 2 diabetes mellitus.
PLoS ONE
PUBLISHED: 01-01-2014
Show Abstract
Hide Abstract
Diabetes is reported to be linked to poorer cognitive function. The purpose of this study is to examine (a) clinical correlation between cognitive function and the biochemical perturbations in T2DM, and (b) the impact of statin treatment on cognitive function in diabetic subjects.
Related JoVE Video
Discovery of prognostic biomarker candidates of lacunar infarction by quantitative proteomics of microvesicles enriched plasma.
PLoS ONE
PUBLISHED: 01-01-2014
Show Abstract
Hide Abstract
Lacunar infarction (LACI) is a subtype of acute ischemic stroke affecting around 25% of all ischemic stroke cases. Despite having an excellent recovery during acute phase, certain LACI patients have poor mid- to long-term prognosis due to the recurrence of vascular events or a decline in cognitive functions. Hence, blood-based biomarkers could be complementary prognostic and research tools.
Related JoVE Video
Necking and failure of constrained 3D microtissues induced by cellular tension.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 12-09-2013
Show Abstract
Hide Abstract
In this paper we report a fundamental morphological instability of constrained 3D microtissues induced by positive chemomechanical feedback between actomyosin-driven contraction and the mechanical stresses arising from the constraints. Using a 3D model for mechanotransduction we find that perturbations in the shape of contractile tissues grow in an unstable manner leading to formation of "necks" that lead to the failure of the tissue by narrowing and subsequent elongation. The magnitude of the instability is shown to be determined by the level of active contractile strain, the stiffness of the extracellular matrix, and the components of the tissue that act in parallel with the active component and the stiffness of the boundaries that constrain the tissue. A phase diagram that demarcates stable and unstable behavior of 3D tissues as a function of these material parameters is derived. The predictions of our model are verified by analyzing the necking and failure of normal human fibroblast tissue constrained in a loop-ended dog-bone geometry and cardiac microtissues constrained between microcantilevers. By analyzing the time evolution of the morphology of the constrained tissues we have quantitatively determined the chemomechanical coupling parameters that characterize the generation of active stresses in these tissues. More generally, the analytical and numerical methods we have developed provide a quantitative framework to study how contractility can influence tissue morphology in complex 3D environments such as morphogenesis and organogenesis.
Related JoVE Video
Design and formulation of functional pluripotent stem cell-derived cardiac microtissues.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 11-19-2013
Show Abstract
Hide Abstract
Access to robust and information-rich human cardiac tissue models would accelerate drug-based strategies for treating heart disease. Despite significant effort, the generation of high-fidelity adult-like human cardiac tissue analogs remains challenging. We used computational modeling of tissue contraction and assembly mechanics in conjunction with microfabricated constraints to guide the design of aligned and functional 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues that we term cardiac microwires (CMWs). Miniaturization of the platform circumvented the need for tissue vascularization and enabled higher-throughput image-based analysis of CMW drug responsiveness. CMW tissue properties could be tuned using electromechanical stimuli and cell composition. Specifically, controlling self-assembly of 3D tissues in aligned collagen, and pacing with point stimulation electrodes, were found to promote cardiac maturation-associated gene expression and in vivo-like electrical signal propagation. Furthermore, screening a range of hPSC-derived cardiac cell ratios identified that 75% NKX2 Homeobox 5 (NKX2-5)+ cardiomyocytes and 25% Cluster of Differentiation 90 OR (CD90)+ nonmyocytes optimized tissue remodeling dynamics and yielded enhanced structural and functional properties. Finally, we demonstrate the utility of the optimized platform in a tachycardic model of arrhythmogenesis, an aspect of cardiac electrophysiology not previously recapitulated in 3D in vitro hPSC-derived cardiac microtissue models. The design criteria identified with our CMW platform should accelerate the development of predictive in vitro assays of human heart tissue function.
Related JoVE Video
Effects of MLC601 on Early Vascular Events in Patients After Stroke: The CHIMES Study.
Stroke
PUBLISHED: 10-17-2013
Show Abstract
Hide Abstract
Early vascular events are an important cause of morbidity and mortality in the first 3 months after a stroke. We aimed to investigate the effects of MLC601 on the occurrence of early vascular events within 3 months of stroke onset.
Related JoVE Video
Novel peptide-doxorubucin conjugates for targeting breast cancer cells including the multidrug resistant cells.
J. Med. Chem.
PUBLISHED: 09-30-2013
Show Abstract
Hide Abstract
The efficacy of chemotherapeutic doxorubucin (Dox) in cancer treatment is limited by two main factors, nonspecific toxicity and the emergence of tumor resistance. To overcome these hurdles, in this study peptide-Dox conjugates were prepared. A decapeptide 18-4a (NH2-WxEYAAQkFL-CONH2) with high specificity for breast cancer cells and improved proteolytic stability was conjugated to Dox to give peptide-Dox ester (1) and amide (2) conjugates. Cell uptake studies showed that the conjugates were 6-10 times selective for breast cancerous cells (MCF-7 and MDA-MB-435) over noncancerous cells (HUVECs and MCF-10A). Conjugate 1 displayed similar toxicity as free Dox toward the breast cancerous cells and was about 40 times less toxic toward the noncancerous cells and 4-fold more toxic toward the Dox resistant MDA-MB-435-MDR cells than the free Dox. These data suggest that conjugate 1 can be used as a potential prodrug for improving the therapeutic index of Dox and potentially many other cytotoxic drugs.
Related JoVE Video
Cognitive screening improves the predictive value of stroke severity scores for functional outcome 3-6 months after mild stroke and transient ischaemic attack: an observational study.
BMJ Open
PUBLISHED: 09-05-2013
Show Abstract
Hide Abstract
To investigate the prognostic value of the neurocognitive status measured by screening instruments, the Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE), individually and in combination with the stroke severity scale, the National Institute of Health Stroke Scale (NIHSS), obtained at the subacute stroke phase or the baseline (?2 weeks), for functional outcome 3-6 months later.
Related JoVE Video
Augmentation of integrin-mediated mechanotransduction by hyaluronic acid.
Biomaterials
PUBLISHED: 08-20-2013
Show Abstract
Hide Abstract
Changes in tissue and organ stiffness occur during development and are frequently symptoms of disease. Many cell types respond to the stiffness of substrates and neighboring cells in vitro and most cell types increase adherent area on stiffer substrates that are coated with ligands for integrins or cadherins. In vivo cells engage their extracellular matrix (ECM) by multiple mechanosensitive adhesion complexes and other surface receptors that potentially modify the mechanical signals transduced at the cell/ECM interface. Here we show that hyaluronic acid (also called hyaluronan or HA), a soft polymeric glycosaminoglycan matrix component prominent in embryonic tissue and upregulated during multiple pathologic states, augments or overrides mechanical signaling by some classes of integrins to produce a cellular phenotype otherwise observed only on very rigid substrates. The spread morphology of cells on soft HA-fibronectin coated substrates, characterized by formation of large actin bundles resembling stress fibers and large focal adhesions resembles that of cells on rigid substrates, but is activated by different signals and does not require or cause activation of the transcriptional regulator YAP. The fact that HA production is tightly regulated during development and injury and frequently upregulated in cancers characterized by uncontrolled growth and cell movement suggests that the interaction of signaling between HA receptors and specific integrins might be an important element in mechanical control of development and homeostasis.
Related JoVE Video
Measuring cell-cell tugging forces using bowtie-patterned mPADs (microarray post detectors).
Methods Mol. Biol.
PUBLISHED: 08-20-2013
Show Abstract
Hide Abstract
Cells generate traction forces upon adhesion to the extracellular matrix as well as to neighboring cells. These forces are important for the growth and maintenance of adhesion structures such as focal adhesions and adherens junctions, and may play roles in tissue development. Here, we describe a method for measuring the tugging force transmitted across the cell-cell junction between two paired cells.
Related JoVE Video
Association of silent lacunar infarct with brain atrophy and cognitive impairment.
J. Neurol. Neurosurg. Psychiatr.
PUBLISHED: 08-09-2013
Show Abstract
Hide Abstract
Silent lacunar infarct (SLI) is associated with cognitive decline and linked to an increased risk of stroke and dementia. We examined the association of SLI with MRI measures of cortical thickness, subcortical and lateral ventricular shapes and cognition in 285 ethnic Chinese elderly.
Related JoVE Video
Neuroimaging standards for research into small vessel disease and its contribution to ageing and neurodegeneration.
Lancet Neurol
PUBLISHED: 07-23-2013
Show Abstract
Hide Abstract
Cerebral small vessel disease (SVD) is a common accompaniment of ageing. Features seen on neuroimaging include recent small subcortical infarcts, lacunes, white matter hyperintensities, perivascular spaces, microbleeds, and brain atrophy. SVD can present as a stroke or cognitive decline, or can have few or no symptoms. SVD frequently coexists with neurodegenerative disease, and can exacerbate cognitive deficits, physical disabilities, and other symptoms of neurodegeneration. Terminology and definitions for imaging the features of SVD vary widely, which is also true for protocols for image acquisition and image analysis. This lack of consistency hampers progress in identifying the contribution of SVD to the pathophysiology and clinical features of common neurodegenerative diseases. We are an international working group from the Centres of Excellence in Neurodegeneration. We completed a structured process to develop definitions and imaging standards for markers and consequences of SVD. We aimed to achieve the following: first, to provide a common advisory about terms and definitions for features visible on MRI; second, to suggest minimum standards for image acquisition and analysis; third, to agree on standards for scientific reporting of changes related to SVD on neuroimaging; and fourth, to review emerging imaging methods for detection and quantification of preclinical manifestations of SVD. Our findings and recommendations apply to research studies, and can be used in the clinical setting to standardise image interpretation, acquisition, and reporting. This Position Paper summarises the main outcomes of this international effort to provide the STandards for ReportIng Vascular changes on nEuroimaging (STRIVE).
Related JoVE Video
Comparison of the Montreal Cognitive Assessment and the Mini-Mental State Examination in detecting multi-domain mild cognitive impairment in a Chinese sub-sample drawn from a population-based study.
Int Psychogeriatr
PUBLISHED: 07-22-2013
Show Abstract
Hide Abstract
We examined the discriminant validity of the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE) in detecting multiple-domain mild cognitive impairment (md-MCI) in a Chinese sub-sample drawn from elderly population-based study.
Related JoVE Video
Rac1 is deactivated at integrin activation sites through an IQGAP1-filamin-A-RacGAP1 pathway.
J. Cell. Sci.
PUBLISHED: 07-10-2013
Show Abstract
Hide Abstract
Cell migration makes a fundamental contribution to both normal physiology and disease pathogenesis. Integrin engagement with extracellular ligands spatially controls, via the cyclical activation and deactivation of the small GTPase Rac1, the dynamic membrane protrusion and cytoskeletal reorganization events that are required for directional migration. Although the pathways that control integrin-mediated Rac1 activation are reasonably well defined, the mechanisms that are responsible for switching off activity are poorly understood. Here, proteomic analysis of activated integrin-associated complexes suggests filamin-A and IQ-motif-containing GTPase-activating protein 1 (IQGAP1) as candidates that link ?1 integrin to Rac1. siRNA-mediated knockdown of either filamin-A or IQGAP1 induced high, dysregulated Rac1 activity during cell spreading on fibronectin. Using immunoprecipitation and immunocytochemistry, filamin-A and IQGAP1 were shown to be part of a complex that is recruited to active ?1 integrin. Mass spectrometric analysis of individual filamin-A, IQGAP1 and Rac1 pull-downs and biochemical analysis, identified RacGAP1 as a novel IQGAP1 binding partner. Further immunoprecipitation and immunocytochemistry analyses demonstrated that RacGAP1 is recruited to IQGAP1 and active ?1 integrin, and that suppression of RacGAP1 expression triggered elevated Rac1 activity during spreading on fibronectin. Consistent with these findings, reduced expression of filamin-A, IQGAP1 or RacGAP1 triggered unconstrained membrane protrusion and disrupted directional cell migration on fibrillar extracellular matrices. These findings suggest a model whereby integrin engagement, followed by filamin-A, IQGAP1 and RacGAP1 recruitment, deactivates Rac1 to constrain its activity spatially and thereby coordinate directional cell migration.
Related JoVE Video
Endothelial cell sensing of flow direction.
Arterioscler. Thromb. Vasc. Biol.
PUBLISHED: 06-27-2013
Show Abstract
Hide Abstract
Atherosclerosis-prone regions of arteries are characterized by complex flow patterns where the magnitude of shear stress is low and direction rapidly changes, termed disturbed flow. How endothelial cells sense flow direction and how it impacts inflammatory effects of disturbed flow are unknown. We therefore aimed to understand how endothelial cells respond to changes in flow direction.
Related JoVE Video
Decreased rabphilin 3A immunoreactivity in Alzheimers disease is associated with A? burden.
Neurochem. Int.
PUBLISHED: 06-21-2013
Show Abstract
Hide Abstract
Synaptic dysfunction, together with neuritic plaques, neurofibrillary tangles and cholinergic neuron loss is an established finding in the Alzheimers disease (AD) neocortex. The synaptopathology of AD is known to involve both pre- and postsynaptic components. However, the status of rabphilin 3A (RPH3A), which interacts with the SNARE complex and regulates synaptic vesicle exocytosis and Ca(2+)-triggered neurotransmitter release, is at present unclear. In this study, we measured RPH3A and its ligand Rab3A as well as several SNARE proteins in postmortem neocortex of patients with AD, and found specific reductions of RPH3A immunoreactivity compared with aged controls. RPH3A loss correlated with dementia severity, cholinergic deafferentation, and increased ?-amyloid (A?) concentrations. Furthermore, RPH3A expression is selectively downregulated in cultured neurons treated with A?25-35 peptides. Our data suggest that presynaptic SNARE dysfunction forms part of the synaptopathology of AD.
Related JoVE Video
Microfluidics embedded within extracellular matrix to define vascular architectures and pattern diffusive gradients.
Lab Chip
PUBLISHED: 06-20-2013
Show Abstract
Hide Abstract
Gradients of diffusive molecules within 3D extracellular matrix (ECM) are essential in guiding many processes such as development, angiogenesis, and cancer. The spatial distribution of factors that guide these processes is complex, dictated by the distribution and architecture of vasculature and presence of surrounding cells, which can serve as sources or sinks of factors. To generate temporally and spatially defined soluble gradients within a 3D cell culture environment, we developed an approach to patterning microfluidically ported microchannels that pass through a 3D ECM. Micromolded networks of sacrificial conduits ensconced within an ECM gel precursor solution are dissolved following ECM gelation to yield functional microfluidic channels. The dimensions and spatial layout of channels are readily dictated using photolithographic methods, and channels are connected to external flow via a gasket that also serves to house the 3D ECM. We demonstrated sustained spatial patterning of diffusive gradients dependent on the architecture of the microfluidic network, as well as the ability to independently populate cells in either the channels or surrounding ECM, enabling the study of 3D morphogenetic processes. To highlight the utility of this approach, we generated model vascular networks by lining the channels with endothelial cells and examined how channel architecture, through its effects on diffusion patterns, can guide the location and morphology of endothelial sprouting from the channels. We show that locations of strongest gradients define positions of angiogenic sprouting, suggesting a mechanism by which angiogenesis is regulated in vivo and a potential means to spatially defining vasculature in tissue engineering applications. This flexible 3D microfluidic approach should have utility in modeling simple tissues and will aid in the screening and identification of soluble factor conditions that drive morphogenetic events such as angiogenesis.
Related JoVE Video
Chinese medicine neuroaid efficacy on stroke recovery: a double-blind, placebo-controlled, randomized study.
Stroke
PUBLISHED: 06-18-2013
Show Abstract
Hide Abstract
Previous clinical studies suggested benefit for poststroke recovery when MLC601 was administered between 2 weeks and 6 months of stroke onset. The Chinese Medicine Neuroaid Efficacy on Stroke recovery (CHIMES) study tested the hypothesis that MLC601 is superior to placebo in acute, moderately severe ischemic stroke within a 72-hour time window.
Related JoVE Video
Effect of B vitamins and lowering homocysteine on cognitive impairment in patients with previous stroke or transient ischemic attack: a prespecified secondary analysis of a randomized, placebo-controlled trial and meta-analysis.
Stroke
PUBLISHED: 06-13-2013
Show Abstract
Hide Abstract
High plasma total homocysteine (tHcy) has been associated with cognitive impairment but lowering tHcy with B-vitamins has produced equivocal results. We aimed to determine whether B-vitamin supplementation would reduce tHcy and the incidence of new cognitive impairment among individuals with stroke or transient ischemic attack?6 months previously.
Related JoVE Video
Innovations at Miami practice show promise for treating high-risk Medicare patients.
Health Aff (Millwood)
PUBLISHED: 06-05-2013
Show Abstract
Hide Abstract
Patients with five or more chronic conditions drive most Medicare costs. Our organization, ChenMed, developed a scalable primary care-led delivery model that focuses on this population while getting reimbursed through full-risk capitation by Medicare Advantage plans. ChenMed is a primary care-led group practice based in Florida that serves low-to-moderate-income elderly patients, largely through the Medicare Advantage program. Our model includes a number of innovations: a one-stop-shop approach for delivering multispecialty services in the community, smaller physician panel sizes of 350-450 patients that allow for intensive health coaching and preventive care, on-site physician pharmacy dispensing, a collaborative physician culture with peer review, and customized information technology. These innovations have improved patient medication adherence, increased the time doctors and patients spend together, and led to high rates of patient satisfaction. Additionally, our Medicare patients have substantially lower rates of hospital use than their peers in the Miami Medicare market. Creating chronic disease centers focused on seniors with multiple chronic conditions is a promising delivery system innovation with major potential to improve the cost and quality of care.
Related JoVE Video
How vinculin regulates force transmission.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 05-28-2013
Show Abstract
Hide Abstract
Focal adhesions mediate force transfer between ECM-integrin complexes and the cytoskeleton. Although vinculin has been implicated in force transmission, few direct measurements have been made, and there is little mechanistic insight. Using vinculin-null cells expressing vinculin mutants, we demonstrate that vinculin is not required for transmission of adhesive and traction forces but is necessary for myosin contractility-dependent adhesion strength and traction force and for the coupling of cell area and traction force. Adhesion strength and traction forces depend differentially on vinculin head (V(H)) and tail domains. V(H) enhances adhesion strength by increasing ECM-bound integrin-talin complexes, independently from interactions with vinculin tail ligands and contractility. A full-length, autoinhibition-deficient mutant (T12) increases adhesion strength compared with VH, implying roles for both vinculin activation and the actin-binding tail. In contrast to adhesion strength, vinculin-dependent traction forces absolutely require a full-length and activated molecule; V(H) has no effect. Physical linkage of the head and tail domains is required for maximal force responses. Residence times of vinculin in focal adhesions, but not T12 or V(H), correlate with applied force, supporting a mechanosensitive model for vinculin activation in which forces stabilize vinculins active conformation to promote force transfer.
Related JoVE Video
Microvascular structure and network in the retina of patients with ischemic stroke.
Stroke
PUBLISHED: 05-28-2013
Show Abstract
Hide Abstract
Microvascular disease has been implicated in the pathogenesis of stroke. The retina provides a window to assess microcirculation noninvasively. We studied the association between quantitatively measured retinal microvascular characteristics and acute ischemic stroke.
Related JoVE Video
Influence of racial differences on outcomes after thrombolytic therapy in acute ischemic stroke.
Int J Stroke
PUBLISHED: 05-22-2013
Show Abstract
Hide Abstract
The National Institutes of Neurological Disorders and Stroke and the European Co-operative Acute Stroke III trials enrolled a largely Caucasian population, but the results are often extrapolated onto non-Caucasians. A limited number of nonrandomized studies have proposed that non-Caucasian patients show differential response to tissue plasminogen activator.
Related JoVE Video
Geometric control of vascular networks to enhance engineered tissue integration and function.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 04-22-2013
Show Abstract
Hide Abstract
Tissue vascularization and integration with host circulation remains a key barrier to the translation of engineered tissues into clinically relevant therapies. Here, we used a microtissue molding approach to demonstrate that constructs containing highly aligned "cords" of endothelial cells triggered the formation of new capillaries along the length of the patterned cords. These vessels became perfused with host blood as early as 3 d post implantation and became progressively more mature through 28 d. Immunohistochemical analysis showed that the neovessels were composed of human and mouse endothelial cells and exhibited a mature phenotype, as indicated by the presence of alpha-smooth muscle actin-positive pericytes. Implantation of cords with a prescribed geometry demonstrated that they provided a template that defined the neovascular architecture in vivo. To explore the utility of this geometric control, we implanted primary rat and human hepatocyte constructs containing randomly organized endothelial networks vs. ordered cords. We found substantially enhanced hepatic survival and function in the constructs containing ordered cords following transplantation in mice. These findings demonstrate the importance of multicellular architecture in tissue integration and function, and our approach provides a unique strategy to engineer vascular architecture.
Related JoVE Video
Biomimetic model to reconstitute angiogenic sprouting morphogenesis in vitro.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 04-08-2013
Show Abstract
Hide Abstract
Angiogenesis is a complex morphogenetic process whereby endothelial cells from existing vessels invade as multicellular sprouts to form new vessels. Here, we have engineered a unique organotypic model of angiogenic sprouting and neovessel formation that originates from preformed artificial vessels fully encapsulated within a 3D extracellular matrix. Using this model, we screened the effects of angiogenic factors and identified two distinct cocktails that promoted robust multicellular endothelial sprouting. The angiogenic sprouts in our system exhibited hallmark structural features of in vivo angiogenesis, including directed invasion of leading cells that developed filopodia-like protrusions characteristic of tip cells, following stalk cells exhibiting apical-basal polarity, and lumens and branches connecting back to the parent vessels. Ultimately, sprouts bridged between preformed channels and formed perfusable neovessels. Using this model, we investigated the effects of angiogenic inhibitors on sprouting morphogenesis. Interestingly, the ability of VEGF receptor 2 inhibition to antagonize filopodia formation in tip cells was context-dependent, suggesting a mechanism by which vessels might be able to toggle between VEGF-dependent and VEGF-independent modes of angiogenesis. Like VEGF, sphingosine-1-phosphate also seemed to exert its proangiogenic effects by stimulating directional filopodial extension, whereas matrix metalloproteinase inhibitors prevented sprout extension but had no impact on filopodial formation. Together, these results demonstrate an in vitro 3D biomimetic model that reconstitutes the morphogenetic steps of angiogenic sprouting and highlight the potential utility of the model to elucidate the molecular mechanisms that coordinate the complex series of events involved in neovascularization.
Related JoVE Video
Fibrous hyaluronic acid hydrogels that direct MSC chondrogenesis through mechanical and adhesive cues.
Biomaterials
PUBLISHED: 03-23-2013
Show Abstract
Hide Abstract
Electrospinning has recently gained much interest due to its ability to form scaffolds that mimic the nanofibrous nature of the extracellular matrix, such as the size and depth-dependent alignment of collagen fibers within hyaline cartilage. While much progress has been made in developing bulk, isotropic hydrogels for tissue engineering and understanding how the microenvironment of such scaffolds affects cell response, these effects have not been extensively studied in a nanofibrous system. Here, we show that the mechanics (through intrafiber crosslink density) and adhesivity (through RGD density) of electrospun hyaluronic acid (HA) fibers significantly affect human mesenchymal stem cell (hMSC) interactions and gene expression. Specifically, hMSC spreading, proliferation, and focal adhesion formation were dependent on RGD density, but not on the range of fiber mechanics investigated. Moreover, traction-mediated fiber displacements generally increased with more adhesive fibers. The expression of chondrogenic markers, unlike trends in cell spreading and cytoskeletal organization, was influenced by both fiber mechanics and adhesivity, in which softer fibers and lower RGD densities generally enhanced chondrogenesis. This work not only reveals concurrent effects of mechanics and adhesivity in a fibrous context, but also highlights fibrous HA hydrogels as a promising scaffold for future cartilage repair strategies.
Related JoVE Video
Inflammatory markers and their association with post stroke cognitive decline.
Int J Stroke
PUBLISHED: 03-16-2013
Show Abstract
Hide Abstract
Population-based studies have demonstrated the association of inflammation and cognitive impairment. However, few studies to date have examined this association in ischemic stroke patients.
Related JoVE Video
Structure, function, and cortical representation of the rat submandibular whisker trident.
J. Neurosci.
PUBLISHED: 03-15-2013
Show Abstract
Hide Abstract
Although the neurobiology of rodent facial whiskers has been studied intensively, little is known about sensing in other vibrissae. Here we describe the under-investigated submandibular "whisker trident" on the rats chin. In this three-whisker array, a unique unpaired midline whisker is laterally flanked by two slightly shorter whiskers. All three whiskers point to the ground and are curved backwards. Unlike other whiskers, the trident is not located on an exposed body part. Trident vibrissae are not whisked and do not touch anything over long stretches of time. However, trident whiskers engage in sustained ground contact during head-down running while the animal is exploring or foraging. In biomechanical experiments, trident whiskers follow caudal ground movement more smoothly than facial whiskers. Remarkably, deflection angles decrease with increasing ground velocity. We identified one putative trident barrel in the left somatosensory cortex and two barrels in the right somatosensory cortex. The elongated putative trident-midline barrel is the longest and largest whisker barrel, suggesting that the midline trident whisker is of great functional significance. Cortical postsynaptic air-puff responses in the trident representation show much less temporal precision than facial whisker responses. Trident whiskers do not provide as much high-resolution information about object contacts as facial whiskers. Instead, our observations suggest an idiothetic function: their biomechanics allow trident whiskers to derive continuous measurements about ego motion from ground contacts. The midline position offers unique advantages in sensing heading direction in a laterally symmetric manner. The changes in trident deflection angle with velocity suggest that trident whiskers might function as a tactile speedometer.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.