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41.
The distribution of 3[H] arachidonic acid incorporated into cultured mouse peritoneal macrophages was assessed upon stimulation of the cells with either the calcium ionophore A23187 or zymosan. After a labeling time of 24 h, cells were stimulated and processed for light and electron microscopic autoradiography. Grains were primarily localized over the plasma membrane and lipid-containing vesicles of both control and stimulated cells. In macrophages stimulated with ionophore, a decreased labeling density was evident in both of these cell compartments. Similar alterations in labeling pattern were observed in zymosan treated cells, although a larger decline in grain density occurred from the plasma membrane compartment. Immunocytochemical localization of PGE2, a major eicosanoid product released upon ionophore stimulation, revealed the presence of the prostaglandin in clear vesicular structures, many of which appear to be continuous with the plasma membrane. These results provide morphological evidence that different cellular pools of arachidonic acid may be differentially mobilized for eicosanoid production as a function of the mode of stimulation. 相似文献
42.
Mitochondrial DNA (mtDNA) from two breeds of cattle, viz., [Hariana (Bos indicus), Holstein (Bos taurus)] and Indian water buffalo (Bubalis bubalus), was analyzed using 13 restriction endonucleases which recognized an average of about 40 six-base sites. Polymorphism among
cattle was detected with six of these enzymes. The two Holstein differed at six sites, whereas the Hariana breed (Bos indicus) did not show any site polymorphism. Surprisingly, the Hariana type differed by only one site from one of the Holstein types.
The total size of buffalo mtDNA was estimated to be 16.4 kb. Polymorphism within the Murrah buffalo breed was observed with
respect to aBglI site. Scarcely any of the restriction fragments of buffalo mtDNA matched those of cattle mtDNA. 相似文献
43.
Cells can be made temporarily permeable if pulsed by high-intensity short-duration electric fields. The molecular mechanisms underlying this electropermeabilization are still unknown. The kinetic events may be described by four successive steps: induction, expansion, stabilization, and resealing. On one hand, cell electropermeabilization is detected only under more stringent conditions when cells have been treated by ethanol. On the other hand, lysolecithin is observed to facilitate cell electropermeabilization. More precisely, these molecules that modify membrane order, when used in concentrations compatible with cell viability, are shown to affect only the expansion and resealing steps. Electropermeabilization is inducing a transition in the membrane organization. Membrane order is modulating the energy barrier needed to evoke this membrane transition which occurs when cells are submitted to a field larger than a characteristic threshold (expansion step). Less order would increase the magnitude of this energy barrier; more order would decrease it. 相似文献
44.
A study on biological activity measurements and heterotrophic bacteria in a small freshwater lake 总被引:1,自引:1,他引:0
A 6-m-deep lake has been sampled to measure the temporal and depth-wise distribution of heterotrophic bacteria and biological activity in the water. Surface, mid-depth and bottom waters were analysed at monthly intervals for a period of one year. The coefficient of heterotrophic activity, alkaline phosphatase activity and biological oxygen demand are used as an index of biological activity. The bacterial community was at maximum during spring, coinciding with high values of biological activity. Highest biological activity was observed in the bottom waters. Dissolved organic carbon showed a significant positive correlation with most of the biological activity parameters. This suggests that biological activity, as measured by the coefficient of heterotrophic activity, was more closely related to the concentration of substrates than to population density of heterotrophic bacteria. 相似文献
45.
Na,K-ATPase (ATP phosphohydrolase EC 3.6.1.3) activity was determined in homogenates of cortical brain slices after incubation in normal Krebs-Ringer phosphate medium at 1 atm oxygen pressure. After 10 min of incubation Na,K-ATPase activity was reduced by approximately 50%. Longer incubation did not cause further change in activity. The presence of 0.1 mM-MnCl2 in the medium offered significant protection, while an excursion to 10 atm oxygen pressure caused further inactivation. Measurements of malonaldehyde levels suggest that the inhibition of Na,K-ATPase is a result of lipid peroxidation. The evidence indicates that brain slices incubated under standard conditions suffer considerable oxidative damage. 相似文献
46.
Jagdish Ojha Narendra Mishra Mahadeo Prasad Saha Jyoti Swarup Datta Munshi 《Hydrobiologia》1979,63(2):153-159
Oxygen uptake of Channa marulius was studied under water with and without access to air. There was a significant increase in the oxygen uptake through the gills when access to air was prevented. However, this value (0.863 ± 0.058 mlO2/indiv./h) was quite low in comparison to the total bimodal oxygen uptake (2.04 ± 0.14 mlO2/indiv./h) in juveniles. In adult fish the oxygen uptake per unit time increased appreciably (4.673 ± 0.404 mlO2/indiv./h). In juveniles as well as in adults the air breathing dominated over aquatic breathing. This fish showed a definite circadian rhythm in the bimodal oxygen uptake during different hours of the day.This work was performed in the Ichthyology Laboratory, P. G. Dept. of Zoology, Bhagalpur University, and was supported by a research grant from Bhagalpur University 相似文献
47.
Crystals of 6-oxybenzo(a)pyrene free radical, formed chemically from the hydroxy derivative of the carcinogen benzo(a)pyrene, can be solubilized in aqueous solutions of DNA and of caffeine. ESR spectral evidence indicate that the radicals exist as dispersed monomers associated with DNA and with caffeine. Comparison of NMR spin-lattice and spin-spin relaxation times in the protons of caffeine has given direct evidence that a part of the unpaired electron (at least 10(-4)) is transferred from the radical to the associated caffeine molecule. Simple consideration of Mulliken's charge transfer theory, however, leads to the conclusion that the intermolecular charge transfer is not likely to be a major source of stabilization energy of the complex. 相似文献
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