In JoVE (1)

Other Publications (21)

Articles by Miriam Cohen in JoVE

Other articles by Miriam Cohen on PubMed

Heparanase Mediates Cell Adhesion Independent of Its Enzymatic Activity

FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology. Jun, 2003  |  Pubmed ID: 12773484

Heparanase is an endo-beta-D-glucuronidase that cleaves heparan sulfate and is implicated in diverse physiological and pathological processes. In this study we report on a novel direct involvement of heparanase in cell adhesion. We demonstrate that expression of heparanase in nonadherent lymphoma cells induces early stages of cell adhesion, provided that the enzyme is expressed on the cell surface. Heparanase-mediated cell adhesion to extracellular matrix (ECM) results in integrin-dependent cell spreading, tyrosine phosphorylation of paxillin, and reorganization of the actin cytoskeleton. The surface-bound enzyme also augments cell invasion through a reconstituted basement membrane. Cell adhesion was augmented by cell surface heparanase regardless of whether the cells were transfected with active or point mutated inactive enzyme, indicating that heparanase functions as an adhesion molecule independent of its endoglycosidase activity. The combined feature of heparanase as an ECM-degrading enzyme and a cell adhesion molecule emphasizes its significance in processes involving cell adhesion, migration, and invasion, including embryonic development, neovascularization, and cancer metastasis.

Organization and Adhesive Properties of the Hyaluronan Pericellular Coat of Chondrocytes and Epithelial Cells

Biophysical Journal. Sep, 2003  |  Pubmed ID: 12944312

Hyaluronan is a megadalton glycosaminoglycan composed of repeating units of D-N-acetylglucosamine-beta-D-Glucuronic acid. It is known to form a highly hydrated pericellular coat around chondrocytes, fibrosarcoma, and smooth muscle cells. Using environmental scanning electron microscopy we detected fully hydrated hyaluronan pericellular coats around rat chondrocytes (RCJ-P) and epithelial cells (A6). Hyaluronan mediates early adhesion of both chondrocytes and A6 cells to glass surfaces. We show that chondrocytes in suspension establish early "soft contacts" with the substrate through a thick, hyaluronidase-sensitive coat (4.4 +/- 0.7 microm). Freshly-attached cells drift under shear stress, leaving hyaluronan "footprints" on the surface. This suggests that chondrocytes are surrounded by a multilayer of entangled hyaluronan molecules. In contrast, A6 cells have a 2.2 +/- 0.4- microm-thick hyaluronidase-sensitive coat, do not drift under shear stress, and remain firmly anchored to the surface. We consider the possibility that in A6 cells single hyaluronan molecules, spanning the whole thickness of the pericellular coat, mediate these tight contacts.

Glucose and Nitrogen Regulate the Switch from Histone Deacetylation to Acetylation for Expression of Early Meiosis-specific Genes in Budding Yeast

Molecular and Cellular Biology. Jun, 2004  |  Pubmed ID: 15169885

In eukaryotes, the switch between alternative developmental pathways is mainly attributed to a switch in transcriptional programs. A major mode in this switch is the transition between histone deacetylation and acetylation. In budding yeast, early meiosis-specific genes (EMGs) are repressed in the mitotic cell cycle by active deacetylation of their histones. Transcriptional activation of these genes in response to the meiotic signals (i.e., glucose and nitrogen depletion) requires histone acetylation. Here we follow how this regulated switch is accomplished, demonstrating the existence of two parallel mechanisms. (i) We demonstrate that depletion of glucose and nitrogen leads to a transient replacement of the histone deacetylase (HDAC) complex on the promoters of EMG by the transcriptional activator Ime1. The occupancy by either component occurs independently of the presence or absence of the other. Removal of the HDAC complex depends on the protein kinase Rim15, whose activity in the presence of nutrients is inhibited by protein kinase A phosphorylation. (ii) In the absence of glucose, HDAC loses its ability to repress transcription, even if this repression complex is directly bound to a promoter. We show that this relief of repression depends on Ime1, as well as on the kinase activity of Rim11, a glycogen synthase kinase 3beta homolog that phosphorylates Ime1. We further show that the glucose signal is transmitted through Rim11. In cells expressing the constitutive active rim11-3SA allele, HDAC repression in glucose medium is impaired.

Spatial and Temporal Sequence of Events in Cell Adhesion: from Molecular Recognition to Focal Adhesion Assembly

Chembiochem : a European Journal of Chemical Biology. Oct, 2004  |  Pubmed ID: 15457530

A new concept that attributes a pivotal role to the pericellular coat in the regulation of the early stages of cell adhesion is presented. Quick, adaptable, and transient adhesion through multiple cooperative weak interactions provides the cell with an additional level of modulation in the decision-making process that precedes the commitment to adhesion at a particular site. Hyaluronan emerges as a modulator of cell adhesion in certain cells, mediating binding or repulsion through its polyelectrolyte character, in addition to its chirality and molecular-recognition properties. The biophysical properties of hyaluronan as well as its ultrastructural organization are analyzed in relation to this proposed function.

Magnetic Resonance Imaging Visualization of Hyaluronidase in Ovarian Carcinoma

Cancer Research. Nov, 2005  |  Pubmed ID: 16288020

Hyaluronan, a high molecular weight, negatively charged polysaccharide, is a major constituent of the extracellular matrix. High molecular weight hyaluronan is antiangiogenic, but its degradation by hyaluronidase generates proangiogenic breakdown products. Thus, by expression of hyaluronidase, cancer cells can tilt the angiogenic balance of their microenvironment. Indeed, hyaluronidase-mediated breakdown of hyaluronan correlates with aggressiveness and invasiveness of ovarian cancer metastasis and with tumor angiogenesis. The goal of this work was to develop a novel smart contrast material for detection of hyaluronidase activity by magnetic resonance imaging (MRI). Gadolinium-diethylenetriaminepentaacetic acid (GdDTPA) covalently linked to hyaluronan on the surface of agarose beads showed attenuated relaxivity. Hyaluronidase, either purified from bovine testes or secreted by ES-2 and OVCAR-3 human epithelial ovarian carcinoma cells, activated the hyaluronan-GdDTPA-beads by rapidly altering the R1 and R2 relaxation rates. The change in relaxation rates was consistent with the different levels of biologically active hyaluronidase secreted by those cells. Hyaluronan-GdDTPA-beads were further used for demonstration of MRI detection of hyaluronidase activity in the proximity of s.c. ES-2 ovarian carcinoma tumors in nude mice. Thus, hyaluronan-GdDTPA-beads could allow noninvasive molecular imaging of hyaluronidase-mediated tilt of the peritumor angiogenic balance.

Dynamic Study of the Transition from Hyaluronan- to Integrin-mediated Adhesion in Chondrocytes

The EMBO Journal. Jan, 2006  |  Pubmed ID: 16407968

Membrane-bound hyaluronan mediates the initial adhesive interactions between many cell types and external surfaces. In RCJ-P chondrocytes, such early contacts are mediated through a thick hyaluronidase-sensitive coat. The early adhesion is followed by integrin-mediated interactions and the formation of stable focal adhesions. During this process, the distance between the cell membrane and the surface is reduced from micrometers to few tens of nanometers. The transition from hyaluronan- to integrin-mediated adhesion was studied on glass surfaces by total internal reflection fluorescence microscopy. Hyaluronan-mediated adhesion precedes focal adhesions formation by 2-10 min. After these initial interactions, the pericellular hyaluronan remains sequestered into discrete pockets between the cell and the surface, which are a few hundreds nanometers thick and a few micrometers wide, and are flanked by focal adhesions. The hyaluronan coat facilitates the nucleation of small paxillin-rich contacts, which later mature into focal adhesions. These dynamic studies demonstrate that pericellular hyaluronan mediates initial cell-surface adhesion, and regulates the formation of focal adhesions.

Differential Growth Identified in Salamander Larvae Half-sib Cohorts: Survival Strategy?

Development, Growth & Differentiation. Oct, 2006  |  Pubmed ID: 17026717

In this study we describe the growth of several different larval cohorts (i.e. half-siblings of the same mother born on the same day) of a rare, xeric-adapted salamander Salamandra s. infraimmaculata Martens, 1885, under constant density and food conditions from birth to metamorphosis. The larvae spend the critical first phase of their lives in water, mostly in temporary ponds. Age and weight at metamorphosis were highly affected by varying food conditions. We have identified six different growth modes that these larvae use, both fast growing and slow growing. Each larval cohort was found to use 2-4 different such growth modes regardless of their initial weight. Fast growing modes (I-III) will enable larvae to survive dry years, and metamorphose bigger. Slow growing modes (IV-VI), used by 8% of the larval population, will enable survival only in rainy years. These last growth modes effect differential temporal dispersal in wet years by delaying the emergence of postmetamorphs onto land. Distribution of growth modes in the larval population is affected by food but not by density conditions. Late-born, fast-growing larvae will have an advantage in dry years being able to metamorphose and disperse, whereas the slow-growing larvae will survive only in wet years.

P120 Catenin Regulates Lamellipodial Dynamics and Cell Adhesion in Cooperation with Cortactin

Proceedings of the National Academy of Sciences of the United States of America. Jun, 2007  |  Pubmed ID: 17576929

The armadillo-family protein, p120 catenin (p120), binds to the juxtamembrane domain of classical cadherins and increases cell-cell junction stability. Overexpression of p120 modulates the activity of Rho family GTPases and augments cell migratory ability. Here we show that down-regulation of p120 in epithelial MCF-7 cells by siRNA leads to a striking decrease in lamellipodial persistence and focal adhesion formation. Similar alterations in lamellipodial activity were observed in MCF-7 cells treated with siRNA to cortactin, an activator of Arp2/3-dependent actin polymerization. We found that, in many cell types, p120 is colocalized with cortactin-containing actin structures not only at cell-cell junctions, but also at extrajunctional sites including membrane ruffles and actin-rich halos around endocytotic vesicles. p120 depletion led to dramatic loss of cortactin and its partner, Arp3, from the cell leading edges. Cortactin and p120 are shown to directly interact with each other via the cortactin N-terminal region. We propose that the mechanism underlying p120 functions at the leading edge involves its cooperation with cortactin.

Efficacy and Tolerability of Asenapine in Acute Schizophrenia: a Placebo- and Risperidone-controlled Trial

The Journal of Clinical Psychiatry. Oct, 2007  |  Pubmed ID: 17960962

This 6-week trial assessed the efficacy, tolerability, and safety of the investigational psychopharmacologic agent asenapine versus placebo and risperidone in patients with acute schizophrenia (DSM-IV criteria).

ABO Blood Group Glycans Modulate Sialic Acid Recognition on Erythrocytes

Blood. Oct, 2009  |  Pubmed ID: 19704115

ABH(O) blood group polymorphisms are based on well-known intraspecies variations in structures of neutral blood cell surface glycans in humans and other primates. Whereas natural antibodies against these glycans can act as barriers to blood transfusion and transplantation, the normal functions of this long-standing evolutionary polymorphism remain largely unknown. Although microbial interactions have been suggested as a selective force, direct binding of lethal pathogens to ABH antigens has not been reported. We show in this study that ABH antigens found on human erythrocytes modulate the specific interactions of 3 sialic acid-recognizing proteins (human Siglec-2, 1918SC influenza hemagglutinin, and Sambucus nigra agglutinin) with sialylated glycans on the same cell surface. Using specific glycosidases that convert A and B glycans to the underlying H(O) structure, we show ABH antigens stabilize sialylated glycan clusters on erythrocyte membranes uniquely for each blood type, generating differential interactions of the 3 sialic acid-binding proteins with erythrocytes from each blood type. We further show that by stabilizing such structures ABH antigens can also modulate sialic acid-mediated interaction of pathogens such as Plasmodium falciparum malarial parasite. Thus, ABH antigens can noncovalently alter the presentation of other cell surface glycans to cognate-binding proteins, without themselves being a direct ligand.

Asenapine Versus Olanzapine in Acute Mania: a Double-blind Extension Study

Bipolar Disorders. Dec, 2009  |  Pubmed ID: 19832806

To assess the efficacy and tolerability of asenapine versus olanzapine in the extended treatment of bipolar mania.

A 3-week, Randomized, Placebo-controlled Trial of Asenapine in the Treatment of Acute Mania in Bipolar Mania and Mixed States

Bipolar Disorders. Nov, 2009  |  Pubmed ID: 19839993

Asenapine is approved for bipolar disorder and schizophrenia. This was a 3-week, randomized, double-blind, placebo-controlled trial of asenapine for treating acute bipolar mania.

Asenapine in the Treatment of Acute Mania in Bipolar I Disorder: a Randomized, Double-blind, Placebo-controlled Trial

Journal of Affective Disorders. Apr, 2010  |  Pubmed ID: 20096936

Asenapine is indicated in adults for acute treatment of manic or mixed episodes associated with bipolar I disorder with or without psychotic features. This randomized, double-blind, placebo-controlled trial assessed the efficacy, safety, and tolerability of asenapine in bipolar I disorder.

A Novel Approach to Measuring Activity in Chronic Obstructive Pulmonary Disease: Using 2 Activity Monitors to Classify Daily Activity

Journal of Cardiopulmonary Rehabilitation and Prevention. May-Jun, 2010  |  Pubmed ID: 20216326

Patients with chronic obstructive pulmonary disease with a low profile of daily activity have poor health outcomes. Although walking is a common activity, it may not be the most relevant physical activity to measure in this population. It was the purpose of this study to determine the accelerometer-defined thresholds that discriminate a range of daily activities and use these thresholds to assess activity profiles among stages of disease severity.

Asenapine for Long-term Treatment of Bipolar Disorder: a Double-blind 40-week Extension Study

Journal of Affective Disorders. Nov, 2010  |  Pubmed ID: 20537396

Asenapine is approved in the United States for acute treatment of manic or mixed episodes of bipolar I disorder with or without psychotic features. We report the results of long-term treatment with asenapine in patients with bipolar I disorder.

The Sialome--far More Than the Sum of Its Parts

Omics : a Journal of Integrative Biology. Aug, 2010  |  Pubmed ID: 20726801

The glycome is defined as the glycan repertoire of cells, tissues, and organisms, as found under specified conditions. The vastly diverse glycome is generated by a nontemplate driven biosynthesis, which is indirectly encoded in the genome, and very dynamic. Due to this overwhelming diversity, glycomic analysis must be approached at different hierarchical levels of complexity. In this review five such levels of complexity and the experimental approaches used for analysis at each level are discussed for a subclass of the glycome: the sialome. The sialome, in analogy to the canopy of a forest, covers the cell membrane with diverse array of complex sialylated structures. Sialome complexity includes modification of sialic acid core structure (the leaves and flowers), the linkage to the underlying sugar (the stems), the identity, and arrangement of the underlying glycans (the branches), the structural attributes of the underlying glycans (the trees), and finally, the spatial organization of the sialoglycans in relation to components of the intact cell surface (the forest). Understanding the full complexity of the sialome thus requires combined analyses at multiple levels, that is, the sialome is far more than the sum of its parts.

Use of Pedometer and Internet-mediated Walking Program in Patients with Chronic Obstructive Pulmonary Disease

Journal of Rehabilitation Research and Development. 2010  |  Pubmed ID: 20803392

We evaluated an Internet-mediated, pedometer-based program to promote walking in chronic obstructive pulmonary disease (COPD). First, we assessed the accuracy of the Omron HJ-720ITC pedometer (OMRON Healthcare, Inc; Bannockburn, Illinois) in 51 persons with COPD. The Bland-Altman plot showed a median difference of 3 steps (5th and 95th quintiles, -8.0 and 145.0, respectively). We calculated percent difference = ([manual - Omron step counts]/manual step counts) x 100. Variability in percent difference occurred at the lowest usual walking speeds. At speeds 80% of the manual step counts in 20 of the 23 persons with walking speed 0.94 m/s. Accuracy is more variable at lower speeds, but the Omron captures more than 80% of manual step counts in most persons.In this preliminary study, an Internet-mediated walking program using the Omron significantly increased step counts in COPD.

The Relationship of the BODE Index to Oxygen Saturation During Daily Activities in Patients with Chronic Obstructive Pulmonary Disease

Lung. Aug, 2011  |  Pubmed ID: 21701832

The frequency of oxygen desaturation during daily activities in chronic obstructive pulmonary disease (COPD) is poorly defined. The BODE index predicts survival in COPD. The purpose of this study was to determine the relationship between BODE scores and oxygen saturation during daily activities.

Sexual Selection by Female Immunity Against Paternal Antigens Can Fix Loss of Function Alleles

Proceedings of the National Academy of Sciences of the United States of America. Oct, 2011  |  Pubmed ID: 21987817

Humans lack the common mammalian cell surface molecule N-glycolylneuraminic acid (Neu5Gc) due to a CMAH gene inactivation, which occurred approximately three million years ago. Modern humans produce antibodies specific for Neu5Gc. We hypothesized that anti-Neu5Gc antibodies could enter the female reproductive tract and target Neu5Gc-positive sperm or fetal tissues, reducing reproductive compatibility. Indeed, female mice with a human-like Cmah(-/-) mutation and immunized to express anti-Neu5Gc antibodies show lower fertility with Neu5Gc-positive males, due to prezygotic incompatibilities. Human anti-Neu5Gc antibodies are also capable of targeting paternally derived antigens and mediate cytotoxicity against Neu5Gc-bearing chimpanzee sperm in vitro. Models of populations polymorphic for such antigens show that reproductive incompatibility by female immunity can drive loss-of-function alleles to fixation from moderate initial frequencies. Initially, the loss of a cell-surface antigen can occur due to drift in isolated populations or when natural selection favors the loss of a receptor exploited by pathogens, subsequently the same loss-of-function allele can come under sexual selection because it avoids being targeted by the female immune system. Thus, we provide evidence of a link between sexual selection and immune function: Antigenicity in females can select against foreign paternal antigens on sperm and rapidly fix loss-of-function alleles. Similar circumstances existed when the CMAH null allele was polymorphic in ancestral hominins, just before the divergence of Homo from australopithecines.

Detecting Motor Vehicle Travel in Accelerometer Data

COPD. Apr, 2012  |  Pubmed ID: 22409288

Chronic Obstructive Pulmonary Disease (COPD) frequently has a significant impact on patients' everyday activity. Because of this, accurate measurement of daily activity is of particular interest. Although accelerometers are an objective means of measuring daily activity, these devices sense vibrations and erroneously score motor vehicle travel (MVT) as moderate physical activity. It is the objective of this study to develop a new method to analyze accelerometry data that would accurately classify MVT as non-acceleration, or sitting/standing. As sitting/standing has a different pattern of count-to-count variability than walking, we hypothesized that a rolling standard deviation (RSD), which is a measurement of volatility in the data, would more accurately classify periods of MVT than analysis based on activity counts alone. Twenty-two subjects with COPD were studied. A training set of 15% of the dataset was used to establish an RSD-threshold during MVT based on the upper 95%-confidence interval. The accuracy of the RSD thresholds were tested and presented as sensitivity, specificity and receiver operating curves. Results demonstrated high sensitivity and specificity suggesting that the RSD not only accurately classified MVT, but had a low rate of misclassification. The RSD analysis scored more MVT as sitting/standing than assessment by VMU alone. The accuracy of accelerometers to define the profile of daily activity in sedentary populations, such as those with COPD, is greatly improved.

Membrane-Bound Mucins and Mucin Terminal Glycans Expression in Idiopathic or Helicobacter Pylori, NSAID Associated Peptic Ulcers

Digestive Diseases and Sciences. May, 2012  |  Pubmed ID: 22576713

BACKGROUND: The ratio of Helicobacter pylori/NSAID-negative gastric ulcers is increasing. Idiopathic gastric ulcers have unique clinical and endoscopic features, and are associated with more bleeding complications and a higher mortality. Alterations in gastric mucin expression and sialylation pattern may be important in ulcer pathogenesis. AIMS: The purpose of this study was to determine the expression pattern of membrane-bound mucins and side chain sugars in H. pylori associated-, NSAID-, and idiopathic-gastric ulcers. METHODS: We randomly selected 92 patients with H. pylori (group 1, n = 30), NSAID (group 2, n = 18), combined H. pylori and NSAID associated gastric ulcers (group 3, n = 24), and patients with idiopathic gastric ulcers (group 4, n = 20). Immunohistochemistry for T-cell CD4/CD8, MUC1, MUC4, MUC17, and ECA and SNA lectins staining was performed on sections from the ulcer margins. Inflammation score was assessed according to the Sydney system. RESULTS: Bleeding and mortality rates were significantly higher in group 4. CD4 positive T cell count was higher in H. pylori positive patients (P = 0.009). Staining intensity of MUC17 was higher in group 1 than in group 4, foveola and glands alike, with 11.50 ± 3.47 versus 6.80 ± 4.02, and 9.61 ± 4.26 versus 7.59 ± 3.26, respectively (P < 0.0001). This was a mirror image with MUC1. SNA lectin staining was increased in group 4, in parallel to MUC1 expression, indicating more abundant α2-6 sialylation in that group. CONCLUSIONS: Cytoplasmic MUC17 staining was significantly decreased in the cases with idiopathic ulcer. The opposite was demonstrated for MUC1. This observation might be important, since different mucins with altered sialylation patterns likely differ in their protection efficiency against acid and pepsin.

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