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Biomedical subjects

R Wright

Publications and source records attributed to R Wright.

At least 19 recordsLinked to original sources
PubMed1995

Critical threonine and aspartic acid residues within the I domains of beta 2 integrins for interactions with intercellular adhesion molecule 1 (ICAM-1) and C3bi.

Integrins mediate signal transduction through interactions with multiple cellular or extracellular matrix ligands. Evidence is accumulating that the I (or A) domain, a approximately 200-residue inserted sequence in some integrin alpha subunits, mediates ligand binding. We have previously shown that Thr-221 of the putative ligand binding sites within alpha 2 I domain of alpha 2 beta 1 is critical for binding to collagen (Kamata, T., and Takada, Y. (1994) J. Biol. Chem. 269, 26006-26010). Here we report that the mutation of Thr-206 of alpha L blocks intercellular adhesion molecule 1 (ICAM-1) binding to alpha L beta 2 and mutation of Thr-209 of alpha M blocks ICAM-1 and C3bi binding to alpha M beta 2. The data indicate the Thr residues of alpha M and alpha L corresponding to Thr-221 of alpha 2 are critically involved in the ligand interaction with beta 2 integrins. The mutations of the Asp-137 and Asp-239 of alpha L also block ICAM-1 binding to alpha L beta 2, as do the corresponding Asp residues of alpha 2 or alpha M in collagen/alpha 2 beta 1 or C3bi/alpha M beta 2 interactions, respectively. These data suggest that these Thr and Asp residues, conserved among I domains, are critical for interaction with structurally distinct ligands (e.g. ICAMs, C3bi, and collagen).

Amino Acid Sequence↗
PubMed1995

Degradation of HMG-CoA reductase-induced membranes in the fission yeast, Schizosaccharomyces pombe.

Elevated levels of certain membrane proteins, including the sterol biosynthetic enzyme HMG-CoA reductase, induce proliferation of the endoplasmic reticulum. When the amounts of these proteins return to basal levels, the proliferated membranes are degraded, but the molecular details of this degradation remain unknown. We have examined the degradation of HMG-CoA reductase-induced membranes in the fission yeast, Schizosaccharomyces pombe. In this yeast, increased levels of the Saccharomyces cerevisiae HMG-CoA reductase isozyme encoded by HMG1 induced several types of membranes, including karmellae, which formed a cap of stacked membranes that partially surrounded the nucleus. When expression of HMG1 was repressed, the karmellae detached from the nucleus and formed concentric, multilayered membrane whorls that were then degraded. During the degradation process, CDCFDA-stained compartments distinct from preexisting vacuoles formed within the interior of the whorls. In addition to these compartments, particles that contained neutral lipids also formed within the whorl. As the thickness of the whorl decreased, the lipid particle became larger. When degradation was complete, only the lipid particle remained. Cycloheximide treatment did not prevent the formation of whorls. Thus, new protein synthesis was not needed for the initial stages of karmellae degradation. On the contrary, cycloheximide promoted the detachment of karmellae to form whorls, suggesting that a short lived protein may be involved in maintaining karmellae integrity. Taken together, these results demonstrate that karmellae membranes differentiated into self-degradative organelles. This process may be a common pathway by which ER membranes are turned over in cells.

Antifungal Agents↗
PubMed1995

Oral immunization with attenuated Salmonella expressing human sperm antigen induces antibodies in serum and the reproductive tract.

Induction of immune responses in the reproductive tract will be crucial for a functional gamete antigen-based antifertility vaccine. Here we describe the construction and development of an avirulent Salmonella as an oral vaccine delivery vector to elicit sperm-specific immune responses in reproductive tract secretions. A cDNA sequence encoding the human sperm antigen SP10 was cloned on an asd+vector and expressed to a high level in an avirulent delta cya, delta crp, and delta asd vaccine strain of Salmonella typhimurium. Oral immunization of female BALB/c mice with this recombinant Salmonella elicited high-titer anti-SP10 IgG antibodies in serum and IgA antibodies in vaginal secretions. Anti-SP10 antibody titers could be increased by secondary and tertiary oral administrations of the recombinant Salmonella. Induction of sperm-specific antibodies in the reproductive tract following oral administration of a recombinant Salmonella could lead to the development of a simple, safe, efficient, and easy-to-use antifertility vaccine.

Acrosome↗
PubMed1992

Reversible inhibition of albumin production by rat hepatocytes maintained on a laminin-rich gel (Engelbreth-Holm-Swarm) in response to secretory products of Kupffer cells and cytokines.

Decreased albumin synthesis by hepatocytes in liver injury is thought to occur in response to Kupffer cell-derived acute-phase cytokines. In this study we used hepatocytes maintained in a differentiated phenotype, by culture on a laminin-rich gel substratum (Engelbreth-Holm-Swarm matrix), to investigate the effects of Kupffer cell-conditioned medium and purified cytokines (interleukin-1, interleukin-6 and tumor necrosis factor-alpha) on albumin synthesis. Kupffer cell-conditioned medium caused a reversible decrease in albumin synthesis to 64.7% of control (p less than 0.01, Wilcoxon's rank sum test, n = 11) on day 2. Repeated doses caused further dose-dependent reversible responses. The same result was obtained when protease inhibitors (alpha 1-antitrypsin and alpha 2-macroglobulin) were added to Kupffer cell-conditioned medium (n = 3), thus eliminating the potential effect of matrix degradation. Pure interleukin-1, interleukin-6 and tumor necrosis factor-alpha also inhibited albumin synthesis (p less than 0.05, Wilcoxon's rank sum test, n = 5), interleukin-6 having the greatest effect. After exposure to interleukin-1 (30 U.ml-1) and tumor necrosis factor-alpha (300 U.ml-1), decreased albumin synthesis was followed by a rebound increase (n = 3). Our results support the hypothesis that reduced albumin synthesis in the acute-phase response is modulated by cytokines released from Kupffer cells. Moreover, our results suggest that hepatocytes may exhibit a compensatory increase in albumin synthesis after cytokine withdrawal. These findings may be of physiological importance in the recovery from injury and the acute-phase response in vivo.

Albumins↗
PubMed1992

Mutation of a tyrosine localization signal in the cytosolic tail of yeast Kex2 protease disrupts Golgi retention and results in default transport to the vacuole.

Kex2 protease processes pro-alpha-factor in a late Golgi compartment in Saccharomyces cerevisiae. The first approximately 30 residues of the 115 amino acid CO2H-terminal cytosolic tail (C-tail) of the Kex2 protein (Kex2p) contain a Golgi retention signal that resembles coated-pit localization signals in mammalian cell surface receptors. Mutation of one (Tyr713) of two tyrosine residues in the C-tail or deletion of sequences adjacent to Tyr713 results in loss of normal Golgi localization. Surprisingly, loss of the Golgi retention signal resulted in transport of C-tail mutant Kex2p to the vacuole (yeast lysosome), as judged by kinetics of degradation and by indirect immunofluorescence. Analysis of the loss of Kex2 function in vivo after shutting off expression of wild-type or mutant forms proved that mutations that cause rapid vacuolar turnover do so by increasing the rate of exit of the enzyme from the pro-alpha-factor processing compartment. The most likely explanation for these results is that mutation of the Golgi retention signal in the C-tail results in transport of Kex2p to the vacuole by default. Wild-type Kex2p also was transported to the vacuole at an increased rate when overproduced, although apparently not due to saturation of a Golgi-retention mechanism. Instead, the wild-type and C-tail mutant forms of Kex2p may follow distinct paths to the vacuole.

Amino Acid Sequence↗
PubMed1992

Discriminators of willingness to consider cadaveric kidney donation among black Americans.

Black Americans were classified as either willing or unwilling to consider serving as kidney donors according to a combination of demographic and social psychological variables. Findings indicated that, in addition to selected religious variables, willingness to consider donation was associated with gender, age, source of information about organ donation, perceived need for transplants among blacks, self-acceptance of transplant organs and perception of bias in the selection of transplant recipients. Implications of the findings for social work practice and future research are discussed.

Adolescent↗
PubMed1991

Complementation between Sindbis viral RNAs produces infectious particles with a bipartite genome.

Sindbis virus, the type member of the alpha-viruses, is an enveloped virus containing a nonsegmented positive-strand RNA genome. We show that the nonstructural and the structural genes can function to produce infectious virus particles when they are expressed on two different RNA segments. The nonstructural genes are translated from an RNA in which the structural genes have been replaced by the chloramphenicol acetyltransferase gene [Xiong, C., Levis, R., Shen, P., Schlesinger, S., Rice, C. M. & Huang, H. V. (1989) Science 243, 1188-1191]. The structural genes are encoded in a defective-interfering RNA but are translated from a subgenomic RNA. Both segments contain the cis-acting sequences required for replication and packaging and are copackaged. This type of genome provides a model for an ancestral intermediate between alphaviruses and the multipartite positive-strand RNA viruses of plants. These different viruses show sequence similarities in their replicative proteins and are thought to have evolved from a common ancestor.

Animals↗
PubMed1991

Prevention of sepsis following endoscopic retrograde cholangiopancreatography.

Ora; ciprofloxacin was studied as a prophylactic antimicrobial agent in high- and low-risk patients undergoing endoscopic retrograde cholangiography. Ciprofloxacin appeared to be effective, good serum levels were attained, and the drug compared favourably on grounds of cost and convenience with a parenterally-administered cephalosporin.

Administration, Oral↗
PubMed1991

Health, stress, psychological resources, and subjective well-being among older blacks.

This study examines the structural relationships among sociodemographic characteristics, health status, stress, psychological resources, and subjective well-being (SWB) among the Black elderly. A structural equation model of SWB was evaluated with data from the 1979-1980 National Survey of Black Americans. The results revealed that poor subjective health status was predictive of lower levels of personal efficacy and SWB. Stressful life events tended to depress subjective assessments of health and had negative effects on self-esteem and SWB. Marital status and age had positive effects on SWB. Chronic health conditions and other demographic variables, however, had indirect effects on SWB.

Adaptation, Psychological↗
PubMed1991

Isolation and characterization of PEP3, a gene required for vacuolar biogenesis in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae PEP3 gene was cloned from a wild-type genomic library by complementation of the carboxypeptidase Y deficiency in a pep3-12 strain. Subclone complementation results localized the PEP3 gene to a 3.8-kb DNA fragment. The DNA sequence of the fragment was determined; a 2,754-bp open reading frame predicts that the PEP3 gene product is a hydrophilic, 107-kDa protein that has no significant similarity to any known protein. The PEP3 predicted protein has a zinc finger (CX2CX13CX2C) near its C terminus that has spacing and slight sequence similarity to the adenovirus E1a zinc finger. A radiolabeled PEP3 DNA probe hybridized to an RNA transcript of 3.1 kb in extracts of log-phase and diauxic lag-phase cells. Cells bearing pep3 deletion/disruption alleles were viable, had decreased levels of protease A, protease B, and carboxypeptidase Y antigens, had decreased repressible alkaline phosphatase activity, and contained very few normal vacuolelike organelles by fluorescence microscopy and electron microscopy but had an abundance of extremely small vesicles that stained with carboxyfluorescein diacetate, were severely inhibited for growth at 37 degrees C, and were incapable of sporulating (as homozygotes). Fractionation of cells expressing a bifunctional PEP3::SUC2 fusion protein indicated that the PEP3 gene product is present at low abundance in both log-phase and stationary cells and is a vacuolar peripheral membrane protein. Sequence identity established that PEP3 and VPS18 (J. S. Robinson, T. R. Graham, and S. D. Emr, Mol. Cell. Biol. 11:5813-5824, 1991) are the same gene.

Adaptor Proteins, Vesicular Transport↗
PubMed1991

Deoxyribonucleic acid amplification and hybridisation in Crohn's disease using a chlamydial plasmid probe.

The possibility that Crohn's disease is caused by infection with Chlamydia trachomatis was examined by probing for chlamydial plasmid deoxyribonucleic acid (DNA) in DNA extracts from Crohn's disease tissue and by means of a serological study. Gut DNA extracts were obtained from 10 patients with Crohn's disease and four control subjects and were probed with a chlamydial plasmid probe after Southern blotting. The polymerase chain reaction was also used to amplify any chlamydial plasmid DNA present in tissue DNA extracts, before Southern blotting and probing. Chlamydial proctitis control specimens were not available: gut DNA extracts mixed with traces of chlamydia plasmid served as positive controls. Using these techniques, no chlamydial plasmid DNA sequences were found in Crohn's disease tissue. An enzyme linked immunosorbent assay for C trachomatis LI was performed on 48 patients with Crohn's disease and 48 control subjects. Seropositivity was present in 14.6% of patients and 29% of control subjects and was not statistically significant (p greater than 0.05). The failure to show chlamydial DNA and the lack of serological response to chlamydia make C trachomatis infection a very unlikely factor in the pathogenesis of Crohn's disease.

Adult↗
PubMed1990

Correlates of willingness to consider organ donation among blacks.

Professionals in the health care and organ procurement fields reveal that black Americans display limited commitment to organ donation. The present study represents an attempt to shed some light on this issue by examining the relationship of selected demographic, knowledge and attitude-belief variables to willingness to consider organ donation within a black population. Findings indicated that only a few of the demographic and knowledge variables were related to willingness to consider organ donation. All of the attitude-belief variables, however, were found to be significantly associated with the dependent variable. Implications of the findings for recruiting black organ donors and future research are discussed.

Adolescent↗
PubMed1990

Isolation and characterization of PEP5, a gene essential for vacuolar biogenesis in Saccharomyces cerevisiae.

pep5 mutants of Saccharomyces cerevisiae accumulate inactive precursors to the vacuolar hydrolases. The PEP5 gene was isolated from a genomic DNA library by complementation of the pep5-8 mutation. Deletion analysis localized the complementing activity to a 3.3-kb DNA fragment. DNA sequence analysis of the PEP5 gene revealed an open reading frame of 1029 codons with a calculated molecular mass for the encoded protein of 117,403 D. Deletion/disruption of the PEP5 gene did not kill the cells. The resulting strains grow very slowly at 37 degrees. The disruption mutant showed greatly decreased activities of all vacuolar hydrolases examined, including PrA, PrB, CpY, and the repressible alkaline phosphatase. Apparently normal precursors forms of the proteases accumulated in pep5 mutants, as did novel forms of PrB antigen. Antibodies raised to a fusion protein that contained almost half of the PEP5 open reading frame allowed detection by immunoblot of a protein of relative molecular mass 107 kD in extracts prepared from wild-type cells. Cell fractionation showed the PEP5 gene product is enriched in the vacuolar fraction and appears to be a peripheral vacuolar membrane protein.

Alkaline Phosphatase↗
PubMed1990

Viral hepatitis comparative epidemiology.

The epidemiology of HAV, HBV, HCV, HDV and HEV is compared. Spread of HAV and HEV is by the faecal/oral route whereas HBV, HCV and HDV are spread by blood or blood products. HEV is more likely to produce large epidemics than HAV but sporadic cases also occur. HBV, HCV and HDV all occur after blood transfusion, in haemophiliacs and intravenous drug abusers but they differ in their geographical distribution and in the frequency of perinatal transmission which is only common with HBV. Superinfection and interaction between these viruses is discussed.

Hepatitis A↗
PubMed1990

Microbial and endotoxin contamination in water and dialysate in the central United States.

The purified water supplies and randomly selected dialysates of 51 chronic and acute dialysis centers in the central United States were surveyed to assess the relative risks to dialysis patients from microbial and endotoxin contamination. A culture medium more sensitive than those generally employed in routine quality assurance assays was used for recovery of bacteria from water. With this medium, 35.3% of the water samples and 19% of the dialysate samples were out of compliance with the Association for the Advancement of Medical Instrumentation (AAMI) standards: 200 and 2,000 colony forming units (CFU)/ml, respectively. There was no correlation observed between the type of water purification system or the frequency of disinfection of the system and the bacterial and endotoxin contamination levels. There was also no correlation found between the bacterial and fungal CFU per ml and the endotoxin concentration per ml (EU/ml). It is recommended that more sensitive culturing methods be used to provide adequate bacterial monitoring of dialysate center water supplies. Dialysis centers should monitor endotoxin in dialysate on a regular schedule and immediately after any endotoxemic-like patient reactions. Yeast and fungi were observed in 10% and 64% of the water systems, respectively. Dialysate was contaminated by yeast and fungi in 30% and 70% of the centers, respectively. The concentrations of these microbes in both fluids were much lower than bacteria. However, they were observed often enough to warrant further investigation of their impact on the well-being of dialysis patients.

Bacteria↗