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991.
992.
PAUL D. STEIN M.D. CHIN-HUA WANG M.D. JEANNE M. RIDDLE Ph.D. DONALD J. MAGILLIGAN JR. M.D. 《Journal of cardiac surgery》1988,3(3):253-261
The microstructure of 33 spontaneously degenerated porcine bioprosthetic valves was assessed by scanning electron microscopy in order to gather insight regarding the degenerative process. Twenty-four mitral and 9 aortic valves were removed from 32 patients. The duration of insertion was 7.7 +/- 2.4 years (mean +/- SD). All valves showed denudation of endothelial cells and exposure of the subendothelial fibrous tissue. Fibroblastlike cells were occasionally seen. Platelet deposits were observed on 22 of 33 valves (67%). Leukocytes were observed on the surface of 27 of 33 valves (82%). Mononuclear leukocytes were the most common category of cells (66%). Crystalline material was present on the surface of some leukocytes, suggesting that they may serve as a nidus for calcification. Transmission electron microscopy showed leukocytes in the process of phagocytizing collagen fibers. Macrophages, by exerting their scavenger function seem to contribute to destruction of the collagen framework of the valves. Whether the observed lymphocytes and plasma cells reflect an immunological involvement is unclear. 相似文献
993.
The acquisition of allergic contact dermatitis limits the therapeutic usefulness of topical nitrogen mustard in man. A reproducible experimental model for this syndrome has been provided in the guinea-pig. Guinea-pigs were sensitized to nitrogen mustard (HN2) by means of the repeated epicutaneous administration of sensitizer to a skin site, and the injection into that site of complete Freund's adjuvant. Application of dimethyl sulphoxide before HN2 to the sensitization or challenge site facilitated the sensitization and challenge procedures. Positive challenge could be elicited by the intradermal injection of a non-toxic amount of HN2. The methodology extends to the study of a variety of other sensitizers and potential sensitizers. 相似文献
994.
In vitro production of erythropoietin by mouse fetal liver 总被引:5,自引:0,他引:5
Mouse fetal liver tissue has been cultured and shown to produce and release into the culture medium an erythropoietically active substance for up to 30 days of culture. Since this substance can be completely neutralized by an antiserum to erythropoietin and shows a dose-- response relationship in the plethoric mouse assay, it is suggested that the culture medium contains erythropoietin, a hormone important in the regulation of erythropoiesis. Using this procedure, we have obtained the equivalent of about 20.7 unites of erythropoietin from five T-flasks (75 sq cm) over the 30-day culture period. 相似文献
995.
MARTIN L. GOLDMAN M.D. VICTOR SKORAPA JR. JOHN T. GALAMBOS M.D. F.A.C.G. KHEE-TIANG OEN M.D. DONNA FRANKO JOVE M.D. MORTON SILBERMAN D.V.M. 《The American journal of gastroenterology》1978,70(5):489-495
Transcatheter intra-arterial tissue adhesives are effective agents for producing medical splenectomy in dogs. Because of the rapid polymerization of the tissue adhesive, localized occlusion of the splenic artery mimicking a surgical ligation can be achieved leaving the intrasplenic vessels patent. Splenic infarction without evidence of infection was accomplished. 相似文献
996.
BORZELLECA JOSEPH; HAYES JOHNNIE R.; CONDIE LYMAN W.; EGLE JOHN L. JR 《Toxicological sciences》1985,5(3):478-486
Acute and Subchronic Toxicity of 2,4-Dichlorophenol in CD-IMice. BORZELLECA, J. F., HAYES, J. R., CONDIE, L. W., AND EGLE,J. L. JR. (1985) Fundam. Appl. Toxicol. 5, 478486. Theacute oral LD50 of 2,4-dichlorophenol (2,4-DCP) employing cornoil as vehicle was determined to be 1352 mg/kg for female and1276 mg/kg for male CD-I mice. CD-I mice of both sexes wereexposed to 2,4-DCP in drinking water containing 10% Emulphorfor 90 days at concentrations of 0.2, 0.6, and 2.0 mg/ml providingtheoretical daily doses of 50, 150, and 500 mg/kg. These concentrationsresulted in mean daily doses of 50, 143, and 491 mg/kg for femalesand 40, 114, and 383 mg/kg for males. In both sexes, fluid consumptionwas lower in the vehicle control group (10% Emulphor) and inthe 2,4-DCP treated groups than in the naive controls (deionizedwater). There were no biologically significant differences inbody weight gain between females or males in the vehicle controland experimental groups. No differences were found in terminalorgan weights or organ weight ratios in either sex. Hematologicaldifferences were observed in males only and included an increasein leukocytes (high dose) and an increase in polymorphonuclears(low dose). Clinical chemistry parameters were altered in femalesonly and included a decrease in creatinine (low dose), an increasein BUN/creatinine ratio (mid dose), and an increase in ALP (highdose). In an assessment of the hepatic microsomal mixed functionoxidase system, no significant differences were found in thecomponents of the system, component activity, the kinetics ofethylmorphine N-demethylase, or the metabolism of testosterone.Administration of 2,4-DCP to CD-I mice of both sexes for 90days at mean doses of 40 to 491 mg/kg/day in drinking waterdid not elicit either consistent compound-related or dose-dependentsignificant toxicological effects 相似文献
997.
Improved control of image optical density with low-dose digital and conventional radiography in bedside imaging 总被引:1,自引:0,他引:1
Schaefer CM; Greene RE; Oestmann JW; Kamalsky JM; Hall DA; Llewellyn HJ; Robertson CL; Rhea JT; Rosenthal H; Rubens JR 《Radiology》1989,173(3):713-716
The technical and diagnostic performance of simultaneously acquired low-dose (44% of standard dose) storage-phosphor digital radiographs (system resolution = 0.2 mm, 10 bits) were compared with those of standard-dose conventional bedside radiographs of the chest in 32 patients. The mean optical density (OD) of the lungs (800 measurements) was closer to the ideal density with digital radiography (1.45 OD +/- 0.20 [standard deviation] vs 1.75 OD +/- 0.53) and was less often outside the usable range (2.5% vs 42.5%). Receiver operating characteristic analysis for detection of simulated nodules and monitoring devices (nine readers, 4,608 observations) showed that digital radiography was superior to conventional radiography (P less than .05) for four of the nine readers and equivalent to conventional radiography for five readers. The authors concluded that digital radiography produces more consistent and ideal image density and performs at least as well as conventional radiography under phantom test conditions. 相似文献
998.
999.
1000.