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Biomedical subjects

David Weber

Publications and source records attributed to David Weber.

10 recordsLinked to original sources
PubMed2006

Transient receptor potential vanilloid 4-mediated disruption of the alveolar septal barrier: a novel mechanism of acute lung injury.

Disruption of the alveolar septal barrier leads to acute lung injury, patchy alveolar flooding, and hypoxemia. Although calcium entry into endothelial cells is critical for loss of barrier integrity, the cation channels involved in this process have not been identified. We hypothesized that activation of the vanilloid transient receptor potential channel TRPV4 disrupts the alveolar septal barrier. Expression of TRPV4 was confirmed via immunohistochemistry in the alveolar septal wall in human, rat, and mouse lung. In isolated rat lung, the TRPV4 activators 4alpha-phorbol-12,13-didecanoate and 5,6- or 14,15-epoxyeicosatrienoic acid, as well as thapsigargin, a known activator of calcium entry via store-operated channels, all increased lung endothelial permeability as assessed by measurement of the filtration coefficient, in a dose- and calcium-entry dependent manner. The TRPV antagonist ruthenium red blocked the permeability response to the TRPV4 agonists, but not to thapsigargin. Light and electron microscopy of rat and mouse lung revealed that TRPV4 agonists preferentially produced blebs or breaks in the endothelial and epithelial layers of the alveolar septal wall, whereas thapsigargin disrupted interendothelial junctions in extraalveolar vessels. The permeability response to 4alpha-phorbol-12,13-didecanoate was absent in TRPV4(-/-) mice, whereas the response to thapsigargin remained unchanged. Collectively, these findings implicate TRPV4 in disruption of the alveolar septal barrier and suggest its participation in the pathogenesis of acute lung injury.

Acute Disease↗
PubMed2003

Protein-protein interactions involved in the recognition of p27 by E3 ubiquitin ligase.

The p27(Kip1) protein is a potent cyclin-dependent kinase inhibitor, the level of which is decreased in many common human cancers as a result of enhanced ubiquitin-dependent degradation. The multiprotein complex SCF(Skp2) has been identified as the ubiquitin ligase that targets p27, but the functional interactions within this complex are not well understood. One component, the F-box protein Skp2, binds p27 when the latter is phosphorylated on Thr(187), thus providing substrate specificity for the ligase. Recently, we and others have shown that the small cell cycle regulatory protein Cks1 plays a critical role in p27 ubiquitination by increasing the binding affinity of Skp2 for p27. Here we report the development of a homogeneous time-resolved fluorescence assay that allows the quantification of the molecular interactions between human recombinant Skp2, Cks1 and a p27-derived peptide phosphorylated on Thr(187). Using this assay, we have determined the dissociation constant of the Skp2-Cks1 complex (K(d) 140 +/- 14 nM) and have shown that Skp2 binds phosphorylated p27 peptide with high affinity only in the presence of Cks1 (K(d) 37 +/- 2 nM). Cks1 does not bind directly to the p27 phosphopeptide or to Skp1, which confirms its suggested role as an allosteric effector of Skp2.

Allosteric Regulation↗
PubMed2002

Crystal structure of human cytosolic phosphoenolpyruvate carboxykinase reveals a new GTP-binding site.

We report crystal structures of the human enzyme phosphoenolpyruvate carboxykinase (PEPCK) with and without bound substrates. These structures are the first to be determined for a GTP-dependent PEPCK, and provide the first view of a novel GTP-binding site unique to the GTP-dependent PEPCK family. Three phenylalanine residues form the walls of the guanine-binding pocket on the enzyme's surface and, most surprisingly, one of the phenylalanine side-chains contributes to the enzyme's specificity for GTP. PEPCK catalyzes the rate-limiting step in the metabolic pathway that produces glucose from lactate and other precursors derived from the citric acid cycle. Because the gluconeogenic pathway contributes to the fasting hyperglycemia of type II diabetes, inhibitors of PEPCK may be useful in the treatment of diabetes.

Binding Sites↗
PubMed2002

Six-year molecular analysis of Burkholderia cepacia complex isolates among cystic fibrosis patients at a referral center for lung transplantation.

Over a 6-year period, Burkholderia cepacia complex species were isolated from cystic fibrosis (CF) patients receiving care at The University of North Carolina Hospitals (clinic CF patients) and from those referred from other treatment centers. Fifty-six isolates collected from 30 referred patients and 26 clinic CF patients were characterized by pulsed-field gel electrophoresis (PFGE) and were assayed by PCR to detect the cable pilin gene, cblA. PFGE results indicated that six separate clusters (clusters A to F) were present among the 56 isolates and that three clusters (clusters A, B, and E) consisted only of isolates from referred patients infected with B. cepacia complex isolates prior to referral. However, one cluster (cluster C) consisted of isolates from four CF patients, and hospital records indicate that this cluster began with an isolate that came from a referred patient and that spread to three clinic CF patients. Cluster D consisted of two isolates from clinic CF patients, and hospitalization records are consistent with nosocomial, patient-to-patient spread. cblA was present in only 4 of the 56 isolates and included isolates in cluster E from the referred patients. Our results indicate a lack of spread of a previously characterized, transmissible clone from referred patients to our clinic CF population. Only two instances of nosocomial, patient-to-patient spread could be documented over the 6-year period. An additional spread of an isolate (cluster F) from a referred patient to a clinic patient could not be documented as nosocomial and may have been the result of spread in a nonhospitalized setting. The majority (36 of 56) of our B. cepacia complex-infected CF patients harbor isolates with unique genotypes, indicating that a diversity of sources account for infection. These data suggest that CF patients infected with B. cepacia complex and referred for lung transplantation evaluation were not a major source of B. cepacia complex strains that infected our resident CF clinic population.

Burkholderia Infections↗
PubMed2002

Experimental infection of dusky-footed wood rats (Neotoma fuscipes) with Ehrlichia phagocytophila sensu lato.

Dusky-footed wood rats, Neotoma fuscipes, have been implicated in the natural maintenance of Ehrlichia phagocytophila sensu lato, the agent of human granulocytic ehrlichiosis (HGE), in northern California based on high seroprevalence and amplification of E. phagocytophila s.l. DNA from wood rat blood. In order to further assess granulocytic ehrlichiosis in wood rats, we examined wild-caught wood rats for infection and then performed experimental intra-peritoneal infections with E. phagocytophila s.l. in horse or wood rat blood, and tested animals for 120 days by polymerase chain reaction (PCR) and serology. Of 15 wood rats collected from northern California, three were antibody and PCR-positive for E. phagocytophila s.l. at the time of capture. The naturally infected wood rats remained PCR-positive for a mean of 52 days (+/- 7 SD). Experimental i.p. passage of E. phagocytophila s.l. in wood rat blood was successful in three of four wood rats and the mean duration of PCR-positivity was 75 days (+/- 21.2 SD). Experimental infection with E. phagocytophila s.l. in horse blood succeeded in all four of the recipients and the mean duration of PCR-positivity of 81 days (+/- 17.5 SD). No infected individual appeared to be ill based on feeding behavior, activity, and hydration status. These data confirm that wood rats are susceptible to E. phagocytophila s.l., may develop prolonged infection without clinical ehrlichiosis, and may play a role in maintaining E. phagocytophila s.l. in nature.

Animals↗
PubMedDate not supplied

Cytotoxic T-lymphocyte responses to canarypox vector-based HIV vaccines in HIV-seronegative individuals: a meta-analysis of published studies.

PURPOSE: A successful prophylactic HIV vaccine will probably require neutralizing antibodies and vigorous CTL (CD8+ T-cytotoxic lymphocyte) responses. Canarypox vector-based HIV vaccines (ALVAC-HIV) have been gaining momentum as promising HIV vaccine candidates because of their ability to elicit CTL responses. This quantitative meta-analysis was undertaken to determine a summary estimate of CTL responses to ALVAC-HIV vaccines in HIV-1 seronegative volunteers and to identify reasons for differences among studies in the estimated effects on CTL responses. METHOD: After a literature search and data abstraction, eight randomized, double-blind, placebo-controlled studies were selected for meta-analysis. Stratified and random effects meta-regression analyses were performed to search for response differences among studies. RESULTS: Of the various study characteristics, the number of immunizations and the vaccine dose were associated with the likelihood of developing CTL responses. It was not possible to distinguish the effect of either the number of immunizations or the vaccine dose on CTL responses because these two study characteristics were highly associated with each other. CONCLUSION: More trials are warranted to determine the ideal dose/immunization schedule that would elicit maximal CTL responses.

AIDS Vaccines↗
PubMedDate not supplied

25 Health care trends. What's hot, what's not, and what does the future hold.

As we usher in 2003, America's health care system remains in a chaotic state. Will managed care live or die? Will quality improvement efforts pay off? Are we ready for the next bioterrorism attack? Will the shortage of physician soon rival the shortage of nurses? To help gauge where health care stands today and what the future holds, The Physician Executive asked doctors who serve on ACPE's peer review panel to list the hottest health care trends in the U.S right now. Then, we took the list to three respected health care futurists -- Leland Kaiser, PhD, Jeff Goldsmith, PhD, and Russel Coile, MBA -- and asked them for their insights on the trends. Yes, Kaiser, Goldsmith and Coile are opinionated. Yes, they're controversial. But no matter whether you agree or disagree with their views, the three health care futurists' comments could spark discussions that will help shape U.S. health care this year and beyond. The trends are presented in no particular order.

Delivery of Health Care↗