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Biomedical subjects

G D Abrams

Publications and source records attributed to G D Abrams.

At least 55 records · Page 3Linked to original sources
PubMed1985

The independent effects of oxygen radical scavengers on canine infarct size. Reduction by superoxide dismutase but not catalase.

Previous studies demonstrated a significant reduction of ultimate infarct size in the canine heart by the combined administration of superoxide dismutase plus catalase. This study was performed to assess the independent effects of each enzyme on ultimate infarct size due to ischemia/reperfusion. Dogs received 2-hour infusions of superoxide dismutase, catalase, or albumin (controls) via the left atrium beginning 15 minutes before and ending 15 minutes after a 90-minute occlusion of the left circumflex coronary artery. The dogs were killed 6 hours after reperfusion. After histochemical staining, infarct and risk area masses were calculated by gravimetric and planimetric analysis. Infarct size expressed as a percentage of the area at risk was: superoxide dismutase, 19 +/- 5; catalase, 30 +/- 5; and controls, 40 +/- 3. Infarct size in the superoxide dismutase group, but not the catalase group, was significantly less than in controls (P less than 0.05). No significant differences in hemodynamics or area at risk were observed that could explain the differences in infarct size. The results indicate that superoxide dismutase alone protects reperfused ischemic myocardium as well as does the combination of superoxide dismutase and catalase. The beneficial effect of superoxide dismutase and insignificant effect of catalase suggest that tissue damage during ischemia and reperfusion may be mediated largely by superoxide anion but not by hydrogen peroxide.

Animals↗
PubMed1984

Beneficial effects of nafazatrom on ischemic reperfused myocardium.

The effect of nafazatrom, a new antithrombotic agent, was studied in a canine model of regional myocardial ischemia. Nafazatrom was administered 1 mg/kg intravenously every 6 h for 48 h. After 24 h of drug or placebo administration, animals underwent 90 min of occlusion of the proximal left circumflex coronary artery followed by gradual reperfusion over a period of 30 min. Twenty-four hours later, the animals were sacrificed and infarct size was determined by histochemical staining with triphenyltetrazolium chloride. Nafazatrom-treated animals had a significant reduction in infarct size expressed as a percent of the anatomical area at risk for infarction: 21 +/- 5% in the treated group vs. 41 +/- 5% in the control group (X +/- S.E.M., P less than 0.05). Histological examination confirmed the gross results of postmortem histochemical staining. Salvage of ischemically jeopardized tissue appeared to be unrelated to myocardial oxygen demand as there were no hemodynamic differences between groups. The beneficial effects of nafazatrom are presumably related to a limitation of autolytic processes on the heart during and after ischemia as a result of the drug's ability to inhibit lipoxygenase and to prevent the enzymatic degradation of prostacyclin.

Animals↗
PubMed1984

Canine myocardial reperfusion injury. Its reduction by the combined administration of superoxide dismutase and catalase.

Therapy directed against the toxic effects of reactive oxygen species may reduce the final extent of ischemic injury in otherwise viable tissue irreversibly injured by the abrupt reoxygenation of reperfusion. In four groups of dogs, superoxide dismutase plus catalase (groups I-III) or saline (controls) (group IV) was infused into the left atrium. Group I received the infusion for 2 hours, beginning 15 minutes before occlusion of the left circumflex coronary artery (90 minutes) and ending 15 minutes after reperfusion. Group II received the infusion for 1 hour starting 15 minutes before reperfusion. Group III received the infusion for 1 hour beginning 40 minutes after reperfusion. Dogs were killed the next day, and infarct size was determined by dissection and weighing, and confirmed histologically. Infarct size expressed as percent of the anatomic area at risk was: group I, 19.4 +/- 5.0; group II, 21.8 +/- 3.3; group III, 47.6 +/- 10.3; group IV, 43.6 +/- 3.5 (mean +/- SEM). Analysis of variance followed by Duncan's multiple range test showed that ultimate infarct size as assessed in groups I and II differed significantly (P less than 0.05) from that observed in the control animals in group IV, whereas infarct size between groups III and IV did not differ significantly (P greater than 0.05). The percent of left ventricle at risk did not differ between the four groups. The beneficial effects of superoxide dismutase plus catalase could not be explained by hemodynamic differences. Similar protection of jeopardized myocardium in groups I and II suggest that potentially viable tissue is salvaged by scavenging free radicals during early reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Reduction of the extent of ischemic myocardial injury by neutrophil depletion in the dog.

Accumulation of polymorphonuclear neutrophils during the acute inflammatory response may exacerbate tissue injury through the release of activated oxygen products or proteolytic enzymes or both. To assess the role of neutrophils in acute myocardial infarction, circulating neutrophil levels in dogs were reduced by 77 +/- 2% (mean +/- SEM) by administering rabbit antiserum to dog neutrophils. Acute myocardial infarction was induced in open-chest anesthetized dogs by 90 minutes of left circumflex coronary artery occlusion followed by 6 hours of reperfusion. Dogs treated with neutrophil antiserum (n = 8) developed myocardial infarcts that were an average of 43% smaller than infarcts in dogs treated with nonimmune rabbit serum (n = 7) (27.0 +/- 4.5% vs 47.1% +/- 7.5% of the area at risk, p less than 0.05). In a saline-treated control group (n = 8), infarct size was 48.0 +/- 4.7% of the area at risk, a value not significantly different from that of the nonimmune serum group but significantly greater than that in the neutrophil antiserum dogs (p less than 0.05). There were no major hemodynamic differences between groups. Histopathologic examination revealed that infarcted myocardium from dogs given saline or treated with nonimmune serum had a substantial neutrophilic infiltrate, which was virtually absent in infarcted tissue from dogs treated with neutrophil antiserum. These observations suggest that neutrophil accumulation in response to myocardial ischemia may be responsible for a substantial portion of the irreversible myocardial injury resulting from temporary coronary artery occlusion.

Agranulocytosis↗
PubMed1982

Aortic stenosis associated with systemic lupus erythematosus.

Hemodynamically significant valvular lesions have been rarely reported sequelae of Libman-Sacks endocarditis complicating systemic lupus erythematosus (SLE). Furthermore, embolic phenomena associated with these vegetations have not been clearly documented. We present a report of critical aortic stenosis associated with SLE in a patient who had received corticosteroid treatment for several years. An embolus, histologically identical with the aortic valve vegetation, was found in the left anterior descending artery at necropsy. There was no evidence of rheumatic heart disease, bacterial endocarditis or a bicuspid aortic valve. Recent reports suggest an increased incidence of significant valvular dysfunction in patients with SLE who have received long-term corticosteroid treatment.

Adult↗
PubMed1982

Evaluation of a cold-recombinant influenza virus vaccine in ferrets.

Cold-recombinant strains of influenza virus were derived at 25 C using an attenuated cold-adapted (ca) and temperature-sensitive (ts) A/Ann Arbor/6/60 (H2N2) strain and wild-type (wt) strains of epidemic relevance. The cold recombinants were characterized in ferrets in terms of clinical manifestations, viral titers, and histopathologic lesions in turbinates and lungs. The data in ferrets showed that cold recombinants with six genes derived from the ca "master" strain and the two surface antigens of the wt parent strain were predictably attenuated and genetically stable. Attenuation of recombinants with an additional gene derived from the wt parent was less predictable. Recombinants possessing the nonstructural gene of the wt parent showed some reactogenicity at high doses, whereas cold recombinants with RNA 2 from the wt parent did not. A recombinant strain possessing RNA 7 of the wt parent showed reversion to the ts+ phenotype but remained attenuated. Similar results were obtained from testing the recombinants in humans.

Animals↗
PubMed1982

Neurological involvement in mice after infection with a cold-adapted herpes simplex type 2 virus.

Experimental intracerebral infection of 4-week-old mice with the MS strain of herpes simplex virus type 2 or its derivative cold variant was compared. The infectious process was followed in both the brain tissue and the trigeminal ganglia, using hematoxylin and eosin and antigenic tracing with indirect peroxidase-antiperoxidase staining. The wild-type virus elicited a severe meningitis and necrotic lesions by 7 days post-inoculation in the brain. The cold variant produced a mild meningitis and no necrotic lesions. In both viral infections, the neuron seemed to be the target cell at the early stages. Infection with the wild-type strain was able to spread through host tissues and produce confluent lesions, whereas infection with the cold mutant seemed to be confined to individual neurons. Data suggest that the cold variant is restricted in its ability to lyse the cells and spread in the host nervous tissue.

Animals↗
PubMed1981

Enzyme-linked immunosorbent assay of serum protein SAA in rhesus monkeys with secondary amyloidosis.

Tissue deposits of amyloid protein AA and a concomitant elevation of serum protein SAA have been demonstrated previously in mice and humans with secondary amyloidosis, but not in rhesus monkeys (Macaca mulatta). In this study, protein SAA was quantitated in normal and amyloidotic rhesus monkeys using an enzyme-linked immunosorbent assay. Protein AA was isolated from the liver of a rhesus monkey with secondary amyloidosis by a combination of water extraction and gel filtration chromatography. The purified material had rigid, nonbranching fibrillar structures typical of amyloid on electron microscopy and a molecular weight of 9000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The amino acid content and partial sequence were comparable to those reported previously for protein AA of rhesus monkeys. As measured by enzyme-linked immunosorbent assay, normal rhesus monkeys had SAA levels of 40 to 64 ng. of AA equivalents per ml., whereas amyloidotic rhesus monkeys had SAA levels of 1700 to 95,000 ng. of AA equivalents per ml. An elevation of protein SAA was also detected in an amyloidotic pigtailed macaque (Macaca nemestrina) using rabbit antirhesus protein AA. Rabbit antisera against human and mouse protein AA reacted strongly with rhesus protein AA and with amyloidotic rhesus serum, but only slightly with normal rhesus serum, indicating that rhesus proteins AA and SAA have antigenic determinants cross-reactive with protein AA of xenotypic species.

Amino Acid Sequence↗
PubMed1980

Mucosal damage mediated by clostridial toxin in experimental clindamycin-associated colitis.

A toxin produced by Clostridium difficile has been implicated in the pathogenesis of antibiotic-associated colitis in humans and experimental animals. This study was undertaken in order to define the sequential evolution of caecal mucosal lesions in the hamster and to relate those lesions directly to the clostridial toxin. Sterile filtrates from a culture of C. difficile and from caecal contents of clindamycin-treated hamsters were studied with respect to their effects on the caecal mucosa and on cultured cell monolayers. The toxic filtrates both produced cellular swelling in vitro, and appeared to have a similar cytotoxic effect on caecal epithelial cells in vivo. Cellular damage was followed by extensive epithelial desquamation and the evolution of an acute pseudomembranous typhlitis. The pathogenetic sequence produced by the filtrates was identical with that previously described after direct clindamycin treatment. These findings demonstrate that intraluminal clostridial toxin can mediate development of the characteristic antibiotic-associated mucosal lesions.

Animals↗
PubMed1978

Clindamycin-induced enterocolitis in hamsters.

A lethal enterocolitis was induced in hamsters by oral or parenteral administration of clindamycin in amounts comparable to those used in treatment of humans. The intestinal lesions were characterized histologically as an acute inflammatory reaction with pseudomembrane formation and resembled the lesions seen in humans with antibiotic-induced colitis. Results of quantitative stool cultures showed the numbers of Peptostreptococcus and Corynebacterium decreased in animals with colitis after challenge with 100 mg of clindamycin/kg, while numbers of Escherichia coli, Streptococcus faecalis, and clindamycin-resistant Clostridium sordellii and Clostridium difficile increased. Bacteria were not seen within the intestinal lesions. Viruses were not isolated from hamsters with colitis. Although the pathogenesis of this syndrome is not completely established, the evidence is consistent with the hypothesis that the disease is caused by clostridial toxins and that the production of these toxins by organisms within the intestines is enhanced by the effects of clindamycin upon the bowel flora.

Administration, Oral↗