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Biomedical subjects

A Allen

Publications and source records attributed to A Allen.

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

Outcome of renal replacement therapy in antineutrophil cytoplasmic antibody-associated systemic vasculitis.

Antineutrophil cytoplasmic antibody-associated systemic vasculitis (AASV) frequently leads to end-stage renal disease (ESRD). Potentially fatal disease activity can continue after the onset of ESRD in both dialysis and transplant patients, despite the immunosuppressive effects of uremia and rejection prophylaxis, leading to concerns that such patients have greater morbidity and mortality. To assess the outcome of AASV patients receiving renal replacement therapy, a retrospective analysis of 59 patients from our unit who received chronic dialysis, renal transplantation, or both, was performed. The survival of AASV patients with ESRD was comparable to national registry controls, as were both graft and patient survival after renal transplantation. Ther is no evidence that standard immunosuppressive protocols should be altered for AASV patients receiving renal transplants. The rate of relapse of vasculitis for patients on chronic dialysis and after transplantation was 0.09 and 0.02 per patient per year, respectively. These rates are lower than those of other series and support the contention that continued immunosuppression after ESRD, as practiced in our unit, is warranted. Relapses usually responded to cyclophosphamide and high-dose prednisolone treatment. Significantly, vasculitic flare-ups in dialysis patients were sometimes initially misdiagnosed as dialysis complications, leading to fatal delays in effective treatment. Follow-up by physicians experienced in the diagnosis and treatment of vasculitis activity should continue in these patients.

Adolescent↗
PubMed1998

Telemedicine in Latin America.

Latin America, stretching 6,000 miles from Mexico to Tierro del Fuego, is comprised of twenty countries totaling nearly 1/2 billion people. There are wide variations in median income levels, medical access, telecommunications infrastructures, and levels of rurality. The great variety of settings precludes any simple approach to telemedicine deployment.

Computer Communication Networks↗
PubMed1998

High-affinity benzodiazepine antagonists reduce responding maintained by ethanol presentation in ethanol-preferring rats.

In the present study, we examined two high-affinity and selective benzodiazepine (BDZ) receptor antagonists (ZK 93426, CGS 8216) in ethanol (EtOH)-preferring rats whose responding (i.e., lever pressing) was maintained by the presentation of EtOH. The in vivo actions of CGS 8216 (1-30 mg/kg) and ZK 93426 (5-75 mg/kg) were examined after intraperitoneal or oral administration. Flumazenil (10-40 mg/kg) was used as a reference BDZ antagonist. EtOH (10% v/v) and saccharin (0.05 g/v) solutions were concurrently available for 30 min each day under a two-lever fixed-ratio schedule in which four responses on one lever produced the EtOH solution and four responses on the other lever produced the saccharin solution. A 40 mg/kg intraperitoneal injection of flumazenil given on the first injection day (day 1) nonsignificantly reduced control levels of responding maintained by EtOH by 36%. No effects were observed 24 hr after drug administration (day 2). Oral administration of flumazenil was without effect. On day 1, intraperitoneal administration of CGS 8216 (1-20 mg/kg) and ZK 93426 (1-50 mg/kg) reduced control levels of responding maintained by EtOH by 44% to 73%; on day 2, EtOH maintained responding continued to be suppressed with the highest doses (> or = 20 mg/kg) suppressing control levels of responding by as much as 62%. Oral administration of higher doses of CGS 8216 (5-30 mg/kg) and ZK 93426 (10-75 mg/kg) reduced responding maintained by EtOH by as much as 54% to 84% of controls; however, no effects were seen on day 2. Only the highest intraperitoneal dose of ZK 93426 (50 mg/kg) suppressed responding maintained by saccharin. These findings demonstrate that some BDZ antagonists decrease responding maintained by EtOH. The findings suggest that certain BDZ antagonists may have potential as pharmacotherapies to prevent or decrease EtOH abuse in humans.

Animals↗
PubMed1998

A novel method for the visualization of the in situ mucus layer in rat and man.

1. The observed thickness of the gastric mucus barrier varies widely, even appearing discontinuous, depending on the methods used. Here we describe the development and application of a modified periodic acid Schiff/Alcian Blue staining technique for use on cryostat sections of gastric mucosa. This technique for the first time enables the preservation and visualization of the full thickness of the adherent gastric mucus layer and the underlying mucosa. 2. In designing this novel method we have selected those procedures which would result in the least alteration to the mucus layer. The methods used were snap freezing, cryostat sectioning of the whole stomach followed by brief ethanol pretreatment (10 min in 100% ethanol), a prolonged staining with periodic acid Schiff/Alcian Blue (15 min and 2.5 h respectively), a gentle post-fixation (45 min paraformaldehyde vapour at 37 degreesC) and the use of a water-soluble mountant. 3. A continuous, adherent mucus layer was observed over the surface of the rat gastric mucosa (periodic acid Schiff/Alcian Blue stained) and human gastric antral biopsies (periodic acid Schiff stained). In the rat the mean (S.D.) mucus thickness measurements along the antrum to oesophageal axis (which was divided histologically into four regions, A to D) were: A, 166 (47) micrometer; B, 179 (48) micrometer; C, 184 (50) micrometer; D (the non-glandular stratified epithelium at the top of the stomach), Absent. In human gastric antral biopsies the mean (S.D.) mucus thickness was 144 (52) micrometer. 4. This new technique has enabled the visualization and precise measurement of thickness of the gastric mucus layer in rat and man. The adherent gastric mucus layer was observed to be continuous in the rat glandular stomach and human antrum. In validation experiments in rat the mean mucus thickness measurements were found to be twice those measured by conventional histological techniques, in which the mucus layer appeared discontinuous and patchy. However, they were within the range of thickness values seen in unfixed tissues and in the rat in vivo preparation.

Aged↗
PubMed1997

A polydisperse linear random coil model for the quaternary structure of pig colonic mucin.

The distribution of molecular weights for polymeric colonic mucus glycoprotein or "mucin" isolated and solubilised in the presence of protease inhibitors from pig colons is shown to be considerably greater than its "subunit" (thiol reduction product) and papain digested forms using the technique of size-exclusion chromatography coupled to multi-angle laser light scattering, and confirmed by sedimentation equilibrium measurements. The conformation of this mucin is probed by examining the molecular weight-intrinsic viscosity relationship in terms of the Mark-Houwink-Kuhn-Sakurada analysis for its polymeric (or "whole"), reduced and papain-digested forms: an exponent "a" of (1.1 +/- 0.1) is obtained indicating a linear random coil conformation consistent with other mucins. Size-exclusion chromatography coupled to multi-angle laser light scattering is shown to provide a relatively simple complementary technique to sedimentation equilibrium for the molecular weight distribution analysis of polydisperse materials.

Animals↗
PubMed1997

Prospective, randomized, double-blind study of high-dose aprotinin in pediatric cardiac operations.

BACKGROUND: Perioperative aprotinin decreases postoperative blood loss in adults undergoing cardiac operations, but its role is less clear in children. Therefore, a trial of aprotinin in pediatric cardiac operations was conducted to study the efficacy of its use in children. METHODS: Forty-two patients were randomly assigned to receive either high-dose aprotinin or placebo. Aprotinin efficacy was assessed using time from protamine administration to skin closure, postoperative blood loss and hemoglobin loss, and postoperative transfusion requirements. Measures of fibrinolysis (fibrin degradation product titers) and platelet preservation (beta-thromboglobulin levels) were also assessed. RESULTS: There were no statistically significant differences between groups in any of the blood loss or transfusion parameters. Fibrin degradation product levels, measured 4 hours postoperatively, had increased significantly for control patients, but remained unchanged for the aprotinin group (p < 0.02). beta-Thromboglobulin levels increased more rapidly during cardiopulmonary bypass in the control group (p = 0.03). CONCLUSIONS: Aprotinin appears to provide no clinical benefit in routine pediatric cardiac operations. A reduction in fibrinolysis, with perhaps an early preservation of platelet structure, is seen in the aprotinin group.

Aprotinin↗