In JoVE (1)

Other Publications (10)

Articles by Erik R. Barthel in JoVE

Other articles by Erik R. Barthel on PubMed

Manipulating the Production and Recombination of Electrons During Electron Transfer: Femtosecond Control of the Charge-transfer-to-solvent (CTTS) Dynamics of the Sodium Anion

Journal of the American Chemical Society. Jun, 2002  |  Pubmed ID: 12071773

The scavenging of a solvated electron represents the simplest possible electron-transfer (ET) reaction. In this work, we show how a sequence of femtosecond laser pulses can be used to manipulate an ET reaction that has only electronic degrees of freedom: the scavenging of a solvated electron by a single atom in solution. Solvated electrons in tetrahydrofuran are created via photodetachment using the charge-transfer-to-solvent (CTTS) transition of sodide (Na(-)). The CTTS process ejects electrons to well-defined distances, leading to three possible initial geometries for the back ET reaction between the solvated electrons and their geminate sodium atom partners (Na(0)). Electrons that are ejected within the same solvent cavity as the sodium atom (immediate contact pairs) undergo back ET in approximately 1 ps. Electrons ejected one solvent shell away from the Na(0) (solvent-separated contact pairs) take hundreds of picoseconds to undergo back ET. Electrons ejected more than one solvent shell from the sodium atom (free solvated electrons) do not recombine on subnanosecond time scales. We manipulate the back ET reaction for each of these geometries by applying a "re-excitation" pulse to promote the localized solvated electron ground state into a highly delocalized excited-state wave function in the fluid's conduction band. We find that re-excitation of electrons in immediate contact pairs suppresses the back ET reaction. The kinetics at different probe wavelengths and in different solvents suggest that the recombination is suppressed because the excited electrons can relocalize into different solvent cavities upon relaxation to the ground state. Roughly one-third of the re-excited electrons do not collapse back into their original solvent cavities, and of these, the majority relocalize into a cavity one solvent shell away. In contrast to the behavior of the immediate pair electrons, re-excitation of electrons in solvent-separated contact pairs leads to an early time enhancement of the back ET reaction, followed by a longer-time recombination suppression. The recombination enhancement results from the improved overlap between the electron and the Na(0) one solvent shell away due to the delocalization of the wave function upon re-excitation. Once the excited state decays, however, the enhanced back ET is shut off, and some of the re-excited electrons relocalize even farther from their geminate partners, leading to a long-time suppression of the recombination; the rates for recombination enhancement and relocalization are comparable. Enhanced recombination is still observed even when the re-excitation pulse is applied hundreds of picoseconds after the initial CTTS photodetachment, verifying that solvent-separated contact pairs are long-lived, metastable entities. Taken together, all these results, combined with the simplicity and convenient spectroscopy of the sodide CTTS system, allow for an unprecedented degree of control that is a significant step toward building a full molecular-level picture of condensed-phase ET reactions.

Sigmoid Perforation and Bucket-handle Tear of the Mesocolon After Bicycle Handlebar Injury: a Case Report and Review of the Literature

Journal of Pediatric Surgery. Dec, 2011  |  Pubmed ID: 22152904

We describe an unusual case of sigmoid colon perforation secondary to a bicycle handlebar injury. Because the patient presented 2 days after the initial injury, we suspected that the colon perforation was not the immediate result of the bicycle accident but, rather, was secondary to devascularization. At operation, we found a bucket-handle tear of the colonic mesentery, which was the patient's primary injury and cause of the perforated colon.

Availability of a Pediatric Trauma Center in a Disaster Surge Decreases Triage Time of the Pediatric Surge Population: a Population Kinetics Model

Theoretical Biology & Medical Modelling. 2011  |  Pubmed ID: 21992575

The concept of disaster surge has arisen in recent years to describe the phenomenon of severely increased demands on healthcare systems resulting from catastrophic mass casualty events (MCEs) such as natural disasters and terrorist attacks. The major challenge in dealing with a disaster surge is the efficient triage and utilization of the healthcare resources appropriate to the magnitude and character of the affected population in terms of its demographics and the types of injuries that have been sustained.

A Multicellular Approach Forms a Significant Amount of Tissue-engineered Small Intestine in the Mouse

Tissue Engineering. Part A. Jul, 2011  |  Pubmed ID: 21395443

Tissue-engineered small intestine (TESI) has successfully been used to rescue Lewis rats after massive small bowel resection. In this study, we transitioned the technique to a mouse model, allowing investigation of the processes involved during TESI formation through the transgenic tools available in this species. This is a necessary step toward applying the technique to human therapy. Multicellular organoid units were derived from small intestines of transgenic mice and transplanted within the abdomen on biodegradable polymers. Immunofluorescence staining was used to characterize the cellular processes during TESI formation. We demonstrate the preservation of Lgr5- and DcamKl1-positive cells, two putative intestinal stem cell populations, in proximity to their niche mesenchymal cells, the intestinal subepithelial myofibroblasts (ISEMFs), at the time of implantation. Maintenance of the relationship between ISEMF and crypt epithelium is observed during the growth of TESI. The engineered small intestine has an epithelium containing a differentiated epithelium next to an innervated muscularis. Lineage tracing demonstrates that all the essential components, including epithelium, muscularis, nerves, and some of the blood vessels, are of donor origin. This multicellular approach provides the necessary cell population to regenerate large amounts of intestinal tissue that could be used to treat short bowel syndrome.

Human Tissue-engineered Colon Forms from Postnatal Progenitor Cells: an in Vivo Murine Model

Regenerative Medicine. Nov, 2012  |  Pubmed ID: 23164081

Aim: Loss of colon reservoir function after colectomy can adversely affect patient outcomes. In previous work, human fetal intestinal cells developed epithelium without mesenchyme following implantation in mice. However, for humans, postnatal tissue would be the preferred donor source. We generated tissue-engineered colon (TEC) from postnatal human organoid units. Materials & methods: Organoid units were prepared from human colon waste specimens, loaded onto biodegradable scaffolds and implanted into immunocompromised mice. After 4 weeks, human TEC was harvested. Immunofluorescence staining confirmed human origin, identified differentiated epithelial cell types and verified the presence of supporting mesenchyme. Results: Human TEC demonstrated a simple columnar epithelium. Immunofluorescence staining demonstrated human origin and the three differentiated cell types of mature colon epithelium. Key mesenchymal components (smooth muscle, intestinal subepithelial myofibroblasts and ganglion cells) were seen. Conclusion: Colon can form from human progenitor cells on a scaffold in a mouse host. This proof-of-concept experiment is an important step in transitioning TEC to human therapy.

Calcified Gallstone in a 3 year-old Boy: a Case Report

BMC Research Notes. 2012  |  Pubmed ID: 22888958


Giant Cystic Meconium Peritonitis Presenting in a Neonate with Classic Radiographic Eggshell Calcifications and Treated with an Elective Surgical Approach: a Case Report

Journal of Medical Case Reports. 2012  |  Pubmed ID: 22857611

Giant cystic meconium peritonitis is relatively rare. Patients often present with nonspecific physical findings such as distension and emesis. Plain abdominal films remain invaluable for identifying the characteristic calcifications seen with a meconium pseudocyst, and large eggshell calcifications are pathognomonic for the giant cystic subtype.

Can a Pediatric Trauma Center Improve the Response to a Mass Casualty Incident?

The Journal of Trauma and Acute Care Surgery. Oct, 2012  |  Pubmed ID: 22835994

Recent events including the 2001 terrorist attacks on New York; Hurricane Katrina; the 2010 Haitian and Chilean earthquakes; and the 2011 earthquake, tsunami, and nuclear disaster in Japan have reminded disaster planners and responders of the tremendous scale of mass casualty disasters and their resulting human devastation. Although adult disaster medicine is a well-developed field with roots in wartime medicine, we are increasingly recognizing that children may comprise up to 50% of disaster victims, and response mechanisms are often designed without adequate preparation for the number of pediatric victims that can result. In this short educational review, we explore the differences between the pediatric and adult disaster and trauma populations, the requirements for designation of a site as a pediatric trauma center (PTC), and the magnitude of the problem of pediatric disaster patients as described in the literature, specifically as it pertains to the availability and use of designated PTCs as opposed to trauma centers in general. We also review our own experience in planning and simulating pediatric mass casualty events and suggest strategies for preparedness when there is no PTC available. We aim to demonstrate from this brief survey that the availability of a designated PTC in the setting of a mass casualty disaster event is likely to significantly improve the outcome for the pediatric demographic of the affected population. We conclude that the relative scarcity of disaster data specific to children limits epidemiologic study of the pediatric disaster population and offer suggestions for strategies for future study of our hypothesis. LEVEL OF EVIDENCE: Systematic review, level III.

Solid Pseudopapillary Tumor of the Pancreas: a Single-institution 20-year Series of Pediatric Patients

Journal of Pediatric Surgery. Jun, 2012  |  Pubmed ID: 22703796

Solid pseudopapillary tumor (SPT) of the pancreas is a rare neoplasm. The objective of this study was to review our institution's experience and provide an update on current management in the pediatric population.

Steady-state and Time-dependent Thermodynamic Modeling of the Effect of Intravenous Infusion of Warm and Cold Fluids

The Journal of Trauma and Acute Care Surgery. Jun, 2012  |  Pubmed ID: 22695427

Hypothermia results in vital sign lability, coagulopathy, wound infections, and other sequelae. Normothermia can be restored by several modalities, including passive blanket heating, warm forced-air devices, and active fluid warming (AFW). In AFW, intravenously administered fluids are heated to 40 to 45 °C to minimize net thermal losses and to raise body temperature. Clinical studies have demonstrated the efficacy of AFW as part of a strategy encompassing several methods, but the isolated contribution of AFW to warming has not been theoretically examined in detail.

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