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Biomedical subjects

G D Abrams

Publications and source records attributed to G D Abrams.

At least 91 records · Page 5Linked to original sources
PubMed1970

Efficiency of various intestinal bacteria in assuming normal functions of enteric flora after association with germ-free mice.

Strictly anaerobic and facultatively anaerobic bacteria were isolated from the intestinal tract of normal mice. Germ-free mice were associated with mixtures of varying complexity of pure cultures of these bacteria. The development of normal features in these animals was then determined on the basis of the following criteria: (i) size of the cecum, (ii) size of the Escherichia coli population in the cecum, (iii) histology of the intestinal tract, and (iv) development of a mucosa-associated flora in stomach and large intestine. Germ-free mice contaminated with cecal contents from conventional mice were used as controls to establish normal values for these parameters. Some strictly anaerobic bacteria could be implanted into germ-free mice only after prior implantation of an E. coli strain. E. coli was found in large numbers in stomach and cecum of mice monocontaminated with this organism. Use of restraining devices indicated that the E. coli population in the stomach was maintained by coprophagy and did not contribute significantly to the size of the cecal population. A mixture of 50 strictly anaerobic bacteria plus 80 facultative anaerobes rendered recipient animals normal with respect to the criteria tested. Other, less complex bacterial mixtures reduced the cecal size and the intestinal E. coli population to levels intermediate between those found in normal and germ-free mice. With all bacterial mixtures tested, the intestinal E. coli population decreased, if at all, within a period of about 10 days after introduction of other bacteria, and remained stable thereafter. This suggests that the intestinal E. coli population is controlled by a mechanism which reduces population size without affecting the growth rate.

Journal Article↗
PubMed1966

Effect of the normal microbial flora on the resistance of the small intestine to infection.

Abrams, Gerald D. (The University of Michigan Medical School, Ann Arbor), and Jane E. Bishop. Effect of the normal microbial flora on the resistance of the small intestine to infection. J. Bacteriol. 92:1604-1608. 1966.-Mucosal structure in the small intestine is known to be influenced by the normal microbial flora. This suggests that mucosal resistance to invasion by enteric pathogens might also be affected by the flora. To assess this possibility, germ-free and conventional mice were challenged with Salmonella typhimurium, and both the growth of organisms within the intestinal lumen and the translocation to mesenteric lymph nodes were studied quantitatively. There were significantly more organisms 24 hr after intragastric challenge in the mesenteric nodes of germ-free animals than in those of conventional ones. However, since intraluminal growth in the intestine was also greater in germ-free animals, no conclusion could be drawn about mucosal resistance per se. Results were similar when the challenge was intraduodenal. However, when intestinal emptying was prevented by ileal ligation before challenge, both intraluminal growth and translocation of S. typhimurium were equal in the two groups of mice. It is concluded from these data, as well as from preliminary dye studies of intestinal motility, that the normal flora does not influence mucosal resistance directly, but may alter enteric infection by affecting intestinal emptying.

Animals↗
PubMedDate not supplied

Platelet depletion in experimental myocardial infarction.

Accumulation of platelets in the microvasculature after acute myocardial ischemia may exacerbate tissue injury through the formation of microthrombi and by the release of vasoactive substances. To assess the role of platelets in myocardial ischemic injury and infarction, circulating platelets were reduced by 94 +/- 2% (mean +/- S.E.M.) with sheep antiserum to canine platelets. Regional myocardial ischemia was produced by occlusion of the left circumflex coronary artery (LCCA) for 90 min followed by reperfusion for 5 hours. Infarct size did not differ significantly between antiplatelet serum and nonimmune serum groups: 36 +/- 8 vs. 43 +/- 4% of the area at risk, determined by a post-mortem dual staining technique (p greater than 0.05). A second occlusion-reperfusion control group, sacrificed at 24 hours, did not differ from 5 hr reperfused groups with regard to infarct size. Coronary sinus thromboxane B2 (TXB2) concentrations were not altered significantly by platelet depletion. Histopathologic examination confirmed the presence of necrosis in the infarcted myocardium and revealed substantial leukocytic infiltration in both groups. The results suggest that circulating platelets are not required for the full expression of myocardial ischemic injury resulting from temporary coronary artery occlusion followed by reperfusion.

Animals↗
PubMedDate not supplied

Creation of reentry tears in aortic dissection by means of percutaneous balloon fenestration: gross anatomic and histologic considerations.

PURPOSE: To study the safety and efficacy of percutaneous fenestration in aortic dissection, transmural tears in canine and human aortae were created with conventional angioplasty balloons. MATERIALS AND METHODS: Tears created in the aortae of five living dogs were compared with tears created in postmortem specimens. Percutaneous fenestration was performed in a woman with acute type I dissection and ischemic hepatitis who died in multisystem failure, and the balloon tear was documented at autopsy. Additional tears in the human aorta were studied in necropsy specimens of normal, Marfanoid, atherosclerotic, and acutely and chronically dissected thoracic and abdominal aortae. RESULTS: In the canine aorta, transmural balloon tears resulted in rapid death of all five animals, and the tears were approximately 10% longer than tears created post mortem with the same balloon. In human aortic specimens, most transmural and all transseptal tears were linear and were oriented nearly perpendicular to the longitudinal axis of the aorta. Tears that were initiated near calcified plaques or large aortic branches extended in unpredictable directions. The transverse orientation of the tears coincided with the long axis of smooth muscle cells in the media of the intact aorta or the dissection septum. CONCLUSION: Percutaneous balloon fenestration, when performed in areas of the aorta relatively free of atherosclerosis, results in transverse tears in the aortic dissection septum. Percutaneous fenestration of the aortic dissection septum appears feasible and should be considered as a treatment option in carefully selected cases of aortic dissection with ischemic complications. A final conclusion regarding the safety and efficacy of percutaneous fenestration undertaken to relieve organ ischemia requires further clinical experience.

Aged↗
PubMedDate not supplied

Canine model of acute aortic rupture: treatment with percutaneous delivery of a covered Z stent--work in progress.

PURPOSE: To develop a percutaneous treatment for aortic rupture with use of a covered intraluminal stent. MATERIALS AND METHODS: A transmural tear was created percutaneously in the thoracic aorta in six dogs with use of a 4-mm angioplasty balloon. Gianturco Z stents were covered with polytetrafluoroethylene, loaded into a 14-F sheath, and advanced through the femoral artery to the site of injury. Within 2 minutes after initiation of the injury, the stent was deployed. Homologous canine blood was given during the procedure. Dogs that survived 24 hours were then killed. RESULTS: The first stent did not expand completely, and the dog died in 1 hour. At necropsy, the first two dogs (1-hour and 8-hour survival) had a large left hemothorax and extensive periaortic hematoma, indicating intrathoracic exsanguination. The next four dogs were treated with a modified stent and survived 2 hours (n = 1), 8 hours (n = 1), and 24 hours (n = 2). At necropsy hemothorax did not exceed 15 mL, and periaortic hematomas were small. The cause of death in the two early casualties with the modified stent is uncertain. There were no signs of spinal cord injury despite occlusion of three pairs of intercostal arteries. CONCLUSION: The covered Z stent (in its modified form) tamponaded the aortic tear, preventing exsanguination. Long-term studies of biocompatibility of this device appear justified.

Acute Disease↗