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11.
Constantin Cojocel Keizo Maita Dale A. Pasino Chao-Hen Kuo Jerry B. Hook 《Life sciences》1983,33(9):855-861
Proximal and distal tubule suspensions were prepared from kidneys of Sprague-Dawley rats by an isolation procedure on a PercollR gradient. The marker enzymes alkaline phosphatase (brush border) and hexokinase (cytoplasmic) as well as p-aminohippurate transport capacity, gluconeogenic activity and electron microscopy were used to characterize the two kidney tubule suspensions. The results of this study indicate that cytochrome P-450 is localized to the proximal tubular cells and that the O-deethylation of 7- ethoxycoumarin was higher in the proximal than distal fraction. Both proximal and distal tubules showed glucuronidation and deacetylation capacities and a relatively equal distribution of non-protein sulfhydryls. These studies demonstrate metabolic heterogeneity of the nephron, the proximal tubule being the main site of renal xenobiotic metabolism. Understanding of metabolic heterogeneity of proximal and distal kidney tubules should provide important information regarding cell specific mechanisms of nephrotoxicity. 相似文献
12.
Constantin Genigeorgis Mohamed S. Foda Antony Mantis Walter W. Sadler 《Applied microbiology》1971,21(5):862-866
Growth and production of enterotoxin C by Staphylococcus aureus strain 137 in 3% + 3% protein hydrolysate powder N-Z Amine NAK broths with 0 to 12% NaCl and an initial pH of 4.00 to 9.83 were studied during an 8-day incubation period at 37 C. Growth was initiated at pH values as low as 4.00 and as high as 9.83 at 0% salt level as long as the inoculum contained at least 10(8) cells per ml. Rate of growth decreased as the NaCl concentration was increased gradually to 12%. Enterotoxin C was produced in broths inoculated with 10(8) cells per ml and above and having initial pH ranges of 4.00 to 9.83, 4.40 to 9.43, 4.50 to 8.55 and respective NaCl concentrations of 0, 4, and 8%. In the presence of 10% NaCl, the pH range supporting enterotoxin C production was 5.45 to 7.30 for an inoculum level of 10(8) cells per ml and 6.38 to 7.30 for 3.6 x 10(6) cells per ml. In repeated experiments in which the inoculum contained 10(8) cells per ml, we failed to demonstrate enterotoxin C production in broths with 12% NaCl and a pH range of 4.50 to 8.55 and concentrated up to 14 times. The effect of NaCl on enterotoxin C production followed the same pattern as its effect on enterotoxin B production. As the concentration of NaCl increased from 0 to 10%, yields of enterotoxin B and C decreased to undetectable amounts. 相似文献
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Evidence that the effect of physical exercise on NK cell activity is mediated by epinephrine 总被引:6,自引:0,他引:6
M Kappel N Tvede H Galbo P M Haahr M Kjaer M Linstow K Klarlund B K Pedersen 《Journal of applied physiology》1991,70(6):2530-2534
The present study was designed to test the hypothesis that the changes in natural killer (NK) cell activity in response to physical exercise were mediated by increased epinephrine concentrations. Eight healthy volunteers 1) exercised on a bicycle ergometer (60 min, 75% of maximal O2 uptake) and 2) on a later day were given epinephrine as an intravenous infusion to obtain plasma epinephrine concentrations comparable with those seen during exercise. Blood samples were collected in the basal state, during the last minutes of exercise or epinephrine infusion, and 2 h later. The NK cell activity (lysis/fixed number of mononuclear cells) increased during exercise and epinephrine infusion and dropped below basal levels 2 h afterward. The increased NK cell activity during exercise and the epinephrine infusion resulted from an increased concentration of NK (CD16+) cells in the peripheral blood. On the other hand, the decreased NK cell activity demonstrated 2 h after exercise and epinephrine infusion did not simply reflect preferential removal of NK cells from the blood, because the proportion of CD16+ cells was normalized. On the basis of the finding that indomethacin abolished the suppressed NK cell activity in vitro and the demonstration of a twofold increase in the proportion of monocytes (CD14+ cells) 2 h after exercise and epinephrine infusion, we suggest that, after stress, prostaglandins released by monocytes are responsible for downregulation of NK cell function. Our findings support the hypothesis that increased plasma epinephrine during physical stress causes a redistribution of mononuclear subpopulations that results in altered function of NK cells. 相似文献
15.
Constantin N. Baxevanis Angelos D. Gritzapis George V. Z. Dedoussis Nikolaos G. Papadopoulos Orestes Tsolas Michael Papamichail 《Cancer immunology, immunotherapy : CII》1994,38(4):281-286
We have recently demonstrated that prothymosin (ProT) when administered intraperitoneally (i.p.) protects DBA/2 mice against the growth of syngeneic leukemic L1210 cells through the induction of tumoricidal peritoneal cells producing high levels of tumor necrosis factor (TNF) [Papanastasiou et al. (1992) Cancer Immunol Immunother 35: 145]. In this report we tested further immunological alterations that may be caused by the administration of ProT in vivo. We demonstrate that i.p. injections of ProT enhance natural killer (NK) cell activity and induce lymphokine-activated (LAK) activity in vivo. Thus, splenocytes from ProT-treated DBA/2 animals exhibited significantly higher cytotoxic activity (up to threefold) against the NK-sensitive YAC cell line and the NK-resistant P815 and L1210 syngeneic tumor cells, as compared to splenocytes from syngeneic control mice. The enhancement of the cytotoxic profile of DBA/2 splenocytes was associated with increased percentages of CD8+ cells, NK cells and activated CD3+ cells. The ProT-induced effect persisted for 30 days after the end of the ProT treatment period and returned to normal levels 20 days later. SPlenocytes from non-treated DBA/2 animals generated high NK and LAK activities in response to ProT in vitro. The ProT-induced NK an LAK activities reached 84% and 75% respectively of what was obtained with interleukin-2 (IL-2). High concentrations of TNF and IL-2 were generated in response to ProT in LAK cultures. These findings suggest that ProT may provide an overall protective effect against tumor growth in vivo through induction of NK and LAK activities possibly indirectly via the production of IL-2 and TNF in the spleen, peritoneal cavity and probably other lymphoid organs.This work was supported by a CEC grant to M. Papamichail 相似文献
16.
Constantin Orfanos 《Cell and tissue research》1962,56(3):387-403
Zusammenfassung Morphologische Unterschiede zwischen fibrillär-phasischen und afibrillärtonischen Skeletmuskelfasern des Frosches werden elektronenmikroskopisch abgebildet und beschrieben. An Synapsen afibrillär-tonischer Fasern werden neben dem synaptischen Axon sehr viel dünnere para-Axone aufgezeigt. Ihre Bedeutung als leitende Axone der terminaisons en grappes oder als Anteile akzessorischer Fasern in der tonischen Synapse wird diskutiert.Durchgeführt mit Unterstützung durch die Deutsche Forschungsgemeinschaft und das Kultusministerium des Landes Nordrhein-Westfalen. 相似文献
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19.
Alexander V. Itkes Kyril T. Turpaev Olga N. Kartasheva Constantin A. Kafiam Evgenii S. Severin 《Molecular and cellular biochemistry》1984,59(1-2):165-171
Summary Dihydrofolate synthetase (EC 6.3.2.12) from N. gonorrhoeae was isolated and enzyme characteristics were determined. The purified enzyme was found quite stable when stored at –60 °C. About 50% of the enzyme activity wag destroyed within 6 weeks when kept at 4 °C. Maximum velocity was observed at pH 9.3. The enzyme required a monovalent cation, K+ or NH4
+ , and divalent cation, Mg2+ or Mn2+ for its function. ATP at 5 mM concentration gave maximum activity. Km values for dihydropteroate and L-glutamate at pH 9.3 were 3.5 × 10–5 M and 6.5 × 10–4 M, respectively. Patterns of product inhibition by dihydrofolate were found to be non-competitive with respect to dihydropteroate, having a Ki value of 5.1 ± 0.8 × 10–4 M, and competitive with respect to L-glutamate, having a Ki value of 6.2 × 10–4 M. 相似文献
20.
Argyris Demetrius Kaliafas Vassilis John Marmaras Constantin Christodoulou 《Development genes and evolution》1984,194(1):37-43
Summary The developmental profile of the major haemolymph proteins (ceratitins) inCeratitis capitata was studied. Ceratitin concentration in the haemolymph decreases dramatically during the last days of pupal life, while the amounts of ceratitins in whole organism extracts remain unchanged. By electrophoretic, immunological and immunofluorescence techniques it was revealed that ceratitins are reabsorbed by the fat body and a fraction of them is deposited in the cuticle. The possible role of ceratitins is discussed. 相似文献