Pneumocystis carinii pneumonia was produced in two groups of rats by the administration of corticosteroids, a low-protein (8%) diet, and tetracycline in the drinking water. A third group not on corticosteroids or a low-protein diet served as controls. Members of the first group were sacrificed weekly for 8 weeks, and lungs were examined. A highly significant correlation was found between the histopathological assessment of the intensity of P. carinii infection and the number of cysts counted in enzyme-digested lungs. P. carinii progressively filled alveoli, and cyst counts increased from less than or equal to 10(4) to 10(9) cysts/g of lung at peak intensity of infection at 7 to 8 weeks. The second group of rats was placed on a regular diet and tapering doses of corticosteroids after week 4, and they were sacrificed at varying intervals for up to 21 weeks. P. carinii was not cleared from the lungs until after week 13 (more than 6 weeks after discontinuation of all steroids). Histologically, there was an increased prominence of alveolar macrophages and the progressive development of interstitial mononuclear cell infiltrate and fibrosis. Thus, P. carinii grows grows slowly in vivo and interacts with specific host cells. The resulting changes may be important in the pathogenesis of the infection and in the clearance of the organism from the lung after immunocompetence has been restored.
Intracellular killing of Staphylococcus aureus by alveolar macrophages is known to be enhanced by exposure to alveolar lining material. Because this material may have a role in pulmonary host defenses, we have studied its effect on pneumococci and other nonstaphylococcal organisms. Alveolar lining material from rats caused rapid killing and lysis of pneumococci. The antipneumococcal activity was localized to the surfactant-containing fraction of the fluid and was not affected by trypsin. Phospholipid extracts of the surfactant fraction or purified lamellar bodies killed pneumococci. Lysis of pneumococci by the surfactant fraction appeared to be mediated by a detergent-like activation of pneumococcal autolysin, in that bacteriolysis was prevented by substitution of ethanolamine for choline in pneumococcal cell walls, and a pneumococcal transformant that lacked autolysin was not lysed. The surfactant fraction readily killed pneumococci containing ethanolamine or the autolysin-defective transformant, and studies with tritiated methyl-D-glucose loading and release showed that killing was associated with increased bacterial cell membrane permeability. Bactericidal activity (without lysis) was observed with several nonpneumococcal gram-positive bacteria, including Streptococcus viridans, unspeciated respiratory streptococci, Streptococcus pyogenes, Streptococcus bovis, and Bacillus species. Purified diacylphospholipids had no antibacterial activity, however, a lysophospholipid, palmitoyl lysophosphatidylcholine, had many properties resembling the surfactant-containing fraction of lavage, including autolysin-mediated pneumococcal lysis, altered cell membrane permeability, and antibacterial activity against several gram-positive bacteria.
Abstract We describe a case of staphylococcal coronary arteritis in the setting of sepsis due to arteriovenous fistula and dialysis catheter infection. The left circumflex coronary artery was the only vessel involved. The patient was a 77-year-old, insulin-dependent diabetic man with chronic renal failure. The immunosuppressed state in diabetes with subsequent septicemia may have facilitated a large number of bacteria to lodge in the atheromatous plaque of the coronary artery. We briefly review previously reported cases and suggest that bacterial arteritis may be an underrecognized cause of acute coronary occlusion.
The tracheobronchial tree of rats was fixed by fixative vapor “from the front,” thus preserving the mucous blanket for morphologic study. Electron microscopic examination of bronchi revealed the ex...
The effectiveness of scintigraphic studies in the study of patients with primary systemic amyloidosis has not been reported previously. This case report describes a patient with the scintigraphic findings of thickened myocardium and delayed gastric emptying, which correlated well with the presence of amyloid deposits in these organs at autopsy. Additionally, the liver and spleen had normal scintigraphic appearances and were free of amyloid at autopsy. Radionuclide studies appear useful in assessing the anatomic and physiologic abnormalities assessed by amyloid deposition.
Subcutaneous injections of the carcinogen dimethylhydrazine in inbred Fischer 344 male rats induced squamous-cell carcinomas in the ear canal, adenocarcinomas in the small bowel and duodenum, and adenomas and adenocarcinomas in the large bowel. The incidences of the tumors induced in the large bowel and ear canal were dose-related. As for tumors of the large bowel, the average size of adenomas was less than that of adenocarcinomas with massive infiltration beyond the muscularis mucosa. The average size of early adenocarcinomas was greater than that of adenomas but less than that of adenocarcinomas with massive infiltration beyond the muscularis mucosa.
