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Biomedical subjects

S Allen

Publications and source records attributed to S Allen.

At least 91 records · Page 5Linked to original sources
PubMed1998

Multicenter evaluation of the Clostridium difficile TOX A/B TEST.

Clostridium difficile, the primary cause of nosocomial diarrhea in the United States and many other industrialized countries, is recognized as a major health concern because of its ability to cause severe intestinal disease leading to complications such as relapses and infections due to vancomycin-resistant enterococci. The disease results from two toxins, toxins A and B, produced by this pathogen. In this study, we evaluated the TOX A/B TEST, a new 1-h enzyme immunoassay (EIA) that detects toxins A and B. We compared the test with the tissue culture assay, which is recognized as the "gold standard" for C. difficile testing. Evaluations were performed in-house at TechLab, Inc. (Blacksburg, Va.) and off-site at four clinical laboratories. Of 1,152 specimens tested, 165 were positive by the TOX A/B TEST and tissue culture and 973 were negative by both tests. The sensitivity and specificity were 92.2 and 100%, respectively. The positive and negative predictive values were 100 and 98.6%, respectively, and the correlation of the TOX A/B TEST with tissue culture was 98.8%. When discrepant samples were resolved by culture, the sensitivity and specificity were 93.2 and 98.9%, respectively. The positive and negative predictive values were 100 and 98.8%, respectively, with a correlation of 99.0%. There were no specimens that were positive by the TOX A/B TEST and negative by tissue culture. Fourteen specimens were negative by the TOX A/B TEST but positive by tissue culture. Of these, two were negative by toxigenic culture, five were positive by toxigenic culture, and seven were not available for further testing. There were no indeterminate results, since the test does not have an indeterminant zone. In a separate study, 102 specimens that were positive by tissue culture and the TOX A/B TEST were examined in toxin A-specific EIAs. Two specimens that presumptively contained toxin A-negative, toxin B-positive (toxA-/toxB+) isolates were identified. One specimen was from a patient with a clinical history consistent with C. difficile infection. Isolates obtained from these specimens by selective culture on solid media and in broth tested toxA-/toxB+ when grown in brain heart infusion dialysis flasks, which stimulate in vitro production of both toxins. Our findings show that the TOX A/B TEST is suitable as a diagnostic aid for C. difficile disease because it correlates well with tissue culture and detects isolates that may be missed with toxin A-specific EIAs.

Bacterial Proteins↗
PubMed1998

Sensitizing students to functional limitations in the elderly: an aging simulation.

BACKGROUND AND OBJECTIVES: Using activities of daily living (ADLs) and instrumental activities of daily living (IADLs) as a focus, faculty at Eastern Virginia Medical School provide an aging simulation exercise for a mandatory fourth-year clerkship in geriatrics. The specific aims of the simulation are to 1) experience the physical frailties of aging, 2) develop creative problem-solving techniques, 3) identify feelings regarding the experience of functional loss, and 4) develop proactive clinical approaches to the care of the elderly. METHODS: Students are assigned one of four diagnoses (Parkinson's disease, rheumatoid arthritis, advanced diabetes, or stroke) and are then impaired to simulate the frailties of the condition, using a variety of clothes, bindings, and other devices. In their "impaired states," they perform ADLs and IADLs, such as paying bills, organizing their pills, shopping, toileting, dressing, and eating. RESULTS: Evaluation results show the aging simulation to be the highest rated program in the clerkship. A pre- and post-course survey on attitudes toward the elderly showed a statistically significant improvement in students' attitudes toward the elderly following the course. CONCLUSIONS: Simulation exercises in aging are useful activities for helping students better understand the feelings and needs of the elderly.

Activities of Daily Living↗
PubMed1998

Ileostomy.

Several different groups of patients may undergo an ileostomy, the two most common being those with ulcerative colitis and and Crohn's disease. Nurses have an important role in providing information, advice and support to such patients.

Humans↗
PubMed1998

Organizational characteristics associated with agency position in community care networks.

This study examines how organizational characteristics affect agency participation and centrality in community service networks. We find that the network structure of agency relations varies for administrative and client-related activities among the 69 agencies studied, which include all but the most isolated agencies serving people with physical disabilities in a single community. In identifying structurally equivalent groups using network analysis, we find that all types of agencies except HMOs are found throughout community service networks. Analyses show that among the five types of relations, minimal intergroup activity occurs within funding and planning networks and that organizational size and ownership are the best organizational predictors of network location and centrality. Non-profits are the most central for planning and client referrals, and large agencies are the most central for funding. We explore the implications of these findings, particularly for sustaining cooperation within the service networks and for the role of non-profits and medical providers in the community.

Community Networks↗
PubMed1997

Calnexin and calreticulin bind to enzymically active tissue-type plasminogen activator during biosynthesis and are not required for folding to the native conformation.

The roles of the endoplasmic-reticulum lectins calnexin and calreticulin in the folding of tissue-type plasminogen activator (tPA) have been investigated using an in vitro translation system that reconstitutes these processes as they would occur in the intact cell. Using co-immunoprecipitation of newly synthesized tPA with antibodies to calnexin and calreticulin, it was demonstrated that the interaction of tPA with both lectins was dependent upon tPA glycosylation and glucosidase trimming. When tPA was synthesized in the presence of semi-permeabilized cells under conditions preventing complex formation with calnexin and calreticulin, the translation product had a specific plasminogenolytic activity identical with that when synthesized under conditions permitting interactions with both lectins. Furthermore, complexes of tPA bound to calnexin and calreticulin were shown to be enzymically active. These results demonstrate that calnexin and calreticulin can form a stable interaction with correctly folded tPA; however, such interactions are not required for the synthesis of enzymically active tPA.

Calcium-Binding Proteins↗
PubMed1997

Detection of antigen-antibody binding events with the atomic force microscope.

An atomic force microscope (AFM) has been used to directly monitor specific interactions between antibodies and antigens employed in an immunoassay system. Results were achieved using AFM probes functionalized with ferritin, and monitoring the adhesive forces between the probe and anti-ferritin antibody-coated substrates. Analysis of the force distribution data suggests a quantization of the forces, with a period of 49 +/- 10 pN. This periodic force may be attributed to single unbinding events between individual antigen and antibody molecules. These results demonstrate that the AFM could be employed as an analytical tool to study the interactions between the molecules involved in biosensor systems. The potential of the technique to provide information relating to the manner in which the antibody molecule binds to its specific antigen is also discussed.

Animals↗
PubMed1997

An evaluation of the amount of nonoxynol-9 remaining in the vagina up to 4 h after insertion of a vaginal contraceptive film (VCF) containing 70 mg nonoxynol-9.

The objectives of this study were to determine the amount of nonoxynol-9 (N-9) remaining in the vagina 30 min and 1, 1.5, 2, and 4 h after vaginal insertion of a single sheet of VCF containing 70 mg N-9 and to compare these results to the manufacturer's instructions for use of this product. A new method of vaginal lavage was used to obtain samples for N-9 determination. This was an open-label, noncomparative, pharmacokinetic study in 12 healthy women volunteers not at risk for pregnancy. The study consisted of a screening visit followed by five test visits approximately 1 month apart and a final visit 1 week after all test visits were completed. At each test visit, the investigator inserted a single sheet of VCF in the vagina of the volunteer at midcycle. The volunteer remained in the clinic and underwent vaginal lavage with normal saline after one of five specified time intervals had elapsed. The sequence of the intervals completed by each volunteer was determined by randomization. When undissolved film was found in the vagina, it was removed prior to lavage and assayed for N-9 content separately from that recovered in lavage fluid. It was assumed that the N-9 in undissolved film would not contribute significantly to sperm immobilization. Between 18.5 and 28.5 mg of N-9 were recovered in lavage fluid after intervals of 0.5, 1, 1.5, and 2 h. These levels did not differ statistically (p > 0.05). The amount of N-9 recovered dropped significantly at 4 h to 11.0 mg. If it is assumed that an N-9 concentration of 0.100 mg/mL is required to immobilize sperm in vitro, this study suggests that the amount of N-9 remaining in the vagina in the form of dissolved film up to 4 h after insertion of VCF is sufficient to immobilize sperm. The lavage procedure may not have recovered all N-9 remaining in the vagina. However, intercourse did not take place between insertion and lavage; if it had, the proportion of the film remaining undissolved and the total amount N-9 remaining in the vagina at the time of examination might have been affected.

Administration, Intravaginal↗
PubMed1997

Effect of aprotinin on vascular reactivity of coronary bypass grafts.

OBJECTIVE: Aprotinin reduces postoperative bleeding and the need for transfusion after cardiopulmonary bypass. The current clinical concern about aprotinin is that it may increase the incidence of postoperative graft thrombosis and thromboembolic phenomena. The fact that the mechanism of action of aprotinin is not completely elucidated and that its effects on the vascular reactivity of bypass conduits are unknown raise doubts regarding its safety. In an attempt to clarify these issues we investigated the vascular reactivity of the human saphenous vein and internal thoracic artery to a range of vasoconstrictor agents in the presence or absence of aprotinin. METHODS: Human saphenous vein was obtained from 24 patients and internal thoracic artery from 7 patients undergoing coronary artery bypass. Vessels were set up in organ baths to record changes in vessel wall tension. RESULTS: Endothelium-dependent relaxations to acetylcholine in saphenous vein rings were unaffected after aprotinin treatment. Contractions to the thromboxane analog U46619 were significantly attenuated after aprotinin treatment in the saphenous vein. Maximum responses were reduced from control values of 88 +/- 7.5 mN to 49.3 +/- 4.8 mN with 1 mumol/L doses of aprotinin (p < 0.05) and 36.6 +/- 4.8 mN with 10 mumol/L doses of 5-hyroxytryptamine or noradrenaline after aprotinin incubations. Furthermore, contractions to U46619 in the internal thoracic artery were unaffected by aprotinin. CONCLUSION: Our data show that there is a preservation of endothelium-dependent responses to acetylcholine and a reduced U46619 vasoconstrictor action on the saphenous vein after aprotinin treatment. Thus the direct effect of aprotinin on the vessel wall could counteract the potential effect of its prothrombotic action on graft patency.

Acetylcholine↗
PubMed1997

Altered endothelial and smooth muscle cell reactivity caused by University of Wisconsin preservation solution in human saphenous vein.

PURPOSE: We have investigated the effect of University of Wisconsin (UW) solution at different temperatures on endothelial and smooth muscle cell function of the human saphenous vein to define the efficacy of UW solution as a preservation solution for saphenous vein conduits. METHODS: Saphenous vein segments from 38 patients undergoing coronary artery bypass surgery were examined with an isolated organ bath technique to monitor changes in vessel reactivity. RESULTS: Endothelial-dependent relaxations to acetylcholine were attenuated after incubation in UW solution at both 4 degrees C and 28 degrees C (p < 0.05, n = 10). In contrast, relaxations to sodium nitroprusside were unchanged after incubation in UW solution at both temperatures (n = 8). The responses to 90 mmol/L KCl were increased at both 4 degrees C and 28 degrees C, respectively. Tyrode's: 27.2% +/- 3.1% and 23.8% +/- 3.0%, UW: 64.7% +/- 8.0% and 73.1% +/- 11% (p < 0.001). In addition, the responses to 5-HT were enhanced at 4 degrees C and 28 degrees C (p < 0.05). In contrast, responses to noradrenaline were enhanced only at 28 degrees C compared with the responses after incubations in Tyrode's solution (p < 0.05, n = 6). Furthermore U46619 (0.3 nmol/L to 1 nmol/L) responses were augmented at 4 degrees C (p < 0.05, n = 7). The potency (pD2) values for each agonist were not significantly different after incubations in UW solution. CONCLUSIONS: We conclude that UW solution produces attenuation of acetylcholine relaxations and temperature-dependent increased reactivity of smooth-muscle cell function in the isolated human saphenous vein. These studies document the complex interactions brought about by UW solution on the different components of the vascular wall that need to be elucidated further if this solution is to attain a place in vascular preservation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1997

Tissue penetration of Meropenem in patients undergoing gynecologic surgery.

The purpose of this study was to assess the tissue-penetrating ability of a new beta-lactam antibiotic, meropenem, in 64 patients undergoing elective gynecologic surgery. Patients received a single 500-mg dose intravenously before surgery. Plasma and tissue concentrations of meropenem were highest at approximately 1 hour, and good tissue penetration was seen in the variety of specimens evaluated. The median plasma concentration at approximately 1 hour was 13.3 micrograms/mL. The median fluid and tissue concentrations at approximately 1 hour were as follows: cervix, 8.5 micrograms/g; endometrium, 2.3 micrograms/g; fallopian tube, 1.9 micrograms/g; myometrium, 3.6 micrograms/g; ovary, 2.3 micrograms/g; and uterus, 2.3 micrograms/g. These tissue concentrations exceed the MICs of meropenem for 90% of typical pathogens associated with gynecologic infections. Meropenem readily penetrates gynecologic tissue. A single 500-mg dose provides adequate tissue concentrations for treatment of gynecologic infections caused by susceptible pathogens.

Adult↗
PubMed1997

Cross-clade human immunodeficiency virus (HIV)-specific cytotoxic T-lymphocyte responses in HIV-infected Zambians.

We have examined cross-clade HIV-specific cytotoxic T-lymphocyte (CTL) activity in peripheral blood of eight Zambian individuals infected with non-B-clade human immunodeficiency virus type 1 (HIV-1). Heteroduplex mobility assay and partial sequence analysis of env and gag genes strongly suggests that all the HIV-infected subjects were infected with clade C HIV-1. Six of eight C-clade HIV-infected individuals elicited CTL activity specific for recombinant vaccinia virus-infected autologous targets expressing HIV gag-pol-env derived from B-clade HIV-1 (IIIB). Recognition of individual recombinant HIV-1 B-clade vaccinia virus-infected targets expressing gag, pol, or env was variable among the patients tested, indicating that cross-clade CTL activity is not limited to a single HIV protein. These data demonstrate that HIV clade C-infected individuals can mount vigorous HIV clade B-reactive CTL responses.

Cross Reactions↗
PubMed1997

Transformation by bovine papillomavirus type 1 E6 is independent of transcriptional activation by E6.

We have generated mutants of bovine papillomavirus type 1 E6 (BE6) that are defective for transcriptional activation and have analyzed these mutants for transformation of contact-inhibited cells and association with the mammalian protein E6-AP. These BE6 mutants demonstrate that transformation by BE6 does not require transcriptional activation and that association of BE6 with E6-AP is a function separable from transcriptional activation by BE6. Association of BE6 with E6-AP appears to be necessary but not sufficient for transformation by BE6. In addition, the mutational analysis of BE6 demonstrates that transactivation, transformation, and association with E6-AP all require sequences throughout the BE6 gene, indicating that the papillomavirus E6 proteins do not have a simple domain structure.

Amino Acid Sequence↗
PubMed1997

Isovolumetric regulation in a distal nephron cell line (A6).

The effects of gradually reducing the osmolality of the basolateral solution (pi b) were examined in a renal epithelial cell line (A6). pi b was linearly decreased with time from 260 to 140 mosmol/ kgH2O. Cell volume did not change when pi b was gradually decreased at dilution rates (D(r)) of 1-1.5 mosmol. kgH2O-1. min-1. Increasing D(r) to 3 or 6 mosmol. kgH2O-1. min-1 abolished this isovolumetric regulation (IVR). Replacing Cl- by NO3- or SCN- inhibited IVR markedly, whereas Br- substituted perfectly for Cl-. On the other hand, with all these anions, the regulatory volume decrease (RVD) was completely developed. Ba2+ (30 mM) markedly slowed down RVD but improved IVR. The discrepancies between RVD and IVR suggest that different mechanisms are used to control cell volume during gradual and shockwise hyposmotic perturbations. During gradual and shockwise reductions of pi b, cellular K+ content was reduced to the same extent; 86Rb efflux was only partially inhibited by Ba2+. The amount of intracellular K+ depletion could account for 70% of the cationic osmolyte loss, which suggests that K+ is the major cation excreted during both types of perturbations.

Animals↗
PubMed1997

Association of toxic shock syndrome toxin-secreting and exfoliative toxin-secreting Staphylococcus aureus with Kawasaki syndrome complicated by coronary artery disease.

Kawasaki syndrome (KS) has been reported to be associated with selective expansion of Vbeta2+ T cells and either staphylococcal toxic shock syndrome toxin-1 or streptococcal pyrogenic exotoxin C in uncomplicated cases. However, there have been no previous studies on the role of superantigens in KS associated with coronary artery disease, the major complication of this illness. The present study characterized bacteria isolated from three acute KS patients who developed coronary artery disease. Staphylococcus aureus secreting either TSST-1 (n = 3) or exfoliative toxin A (n = 1), both known to stimulate expansion of Vbeta2+ T cells, were isolated from all three patients. The percent Vbeta2+ T cells was determined in three patients with coronary artery disease. On presentation, one patient demonstrated reduction, whereas the other two showed expansion, of Vbeta2+ T cells. Repeat analyses of the latter two children showed their percent Vbeta2+ T cells to decrease toward normal. These observations suggest that coronary artery disease in KS may result from superantigenic stimulation of Vbeta2+ T cells. This is also the first demonstration of an association of staphylococcal exfoliative toxin with acute KS. The observation that three different bacterial toxins associated with KS are potent activators of Vbeta2+ T cells suggests an important role for this T cell subset in the pathogenesis of this autoimmune disease.

Aneurysm↗
PubMed1997

Activation of naive xenogeneic but not allogeneic endothelial cells by human naive neutrophils: a potential occult barrier to xenotransplantation.

Here we demonstrate that human neutrophils, the predominant circulating leukocytes in intimate contact with endothelial cells lining the vasculature, directly recognize xenogeneic endothelium independently of xenoreactive natural antibody and complement. A rapid and calcium-dependent activation of native (unstimulated) xenogenic endothelial cells by human neutrophils leads to 1) translocation of P-selectin from the Wiebel-Palade bodies to the surface of xenogeneic endothelial cells, 2) increased synthesis and expression of vascular cell adhesion molecule-1 on the xenogeneic endothelial cells, and 3) enhanced killing of the xenogeneic endothelium by natural killer cells. Our data directly implicate naive neutrophils as major early participants in xenograft recognition and endothelial activation independent of xenoreactive natural antibodies and complement.

Animals↗