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51.
The febrile responses of Sprague-Dawley rats to semi-purified human endogenous pyrogen were studied at a thermoneutral ambient temperature (26 degrees C) and in the cold (3 degrees C). It was found that while rats developed typical monophasic febrile responses at thermoneutrality, febrile responses were absent in the cold-exposed rats. Experiments were conducted to determine whether this lack of febrile responses in cold-exposed rats was due to an inability of these animals to generate or retain heat in the cold. Thermogenesis and vasoconstriction were stimulated in cold-exposed rats by selectively cooling the hypothalamus, using chronically implanted thermodes. It was shown that, using this stimulus, metabolic rate could be increased by more than 50 percent and body temperature could be driven up at a rate of 5 degrees C/hour in rats exposed to the cold. Therefore, it was concluded that the lack of febrile responses of cold-exposed rats to pyrogen is in no way due to a physical or physiological inability to retain heat. Instead, it appears that in some manner cold exposure suppresses the sensitivity or responsiveness of the rat to pyrogenic stimuli. 相似文献
52.
A photosystem other than PS370 also mediates the negative phototaxis of Halobacterium halobium 总被引:2,自引:0,他引:2
Tetsuo Takahashi Hiroaki Tomioka Naoki Kamo Yonosuke Kobatake 《FEMS microbiology letters》1985,28(2):161-164
Abstract It was found that a photorepellent system other than photosystem 370 (PS370) also controls the behavior of Halobacterium halobium . Both the dependence of background illumination and wavelength where the response showed maximum action distinguished that photosystem from PS370 whose photoreceptor pigment is thought to be an intermediate of s-rhodopsin (sR). A mutant strain that has no detectable activity in PS370 and in photoattractant response was isolated. This mutant strain showed the repellent response due to the new photosystem. 相似文献
53.
Changes in the concentration of progesterone, estrone, estradiol, prostaglandins (PG) E2, 6-keto F1 alpha and 13,14-dihydro-15-keto F2 alpha (PGFM) were measured in peripheral plasma, and in venous effluent from the shell gland and the largest (F1) and the second largest (F2) preovulatory follicles. Tissue concentrations in the F1, F2 and the most recently ruptured follicle and the shell gland also were determined. Changes in these criteria were compared to changes in uterine contraction before the first ovulation of a sequence. Significant increases of PGF2 alpha and PGFM in the peripheral plasma were observed when the frequency of uterine contraction reached a maximum, about 1 h before ovulation. Relative to peripheral plasma, the concentrations in F1 plasma of progesterone, PGF2 alpha and PGFM were increased 20-fold, 150-fold and 15-fold, respectively, at the time of the maximum frequency of uterine contraction. The highest tissue concentrations of PGs were also observed in the F1 follicle. These results suggest that the largest preovulatory follicle is the major source of PG synthesis and release. These PGs may stimulate uterine contraction and may also play a role in follicular rupture and release of the ovum. 相似文献
54.
The mature larvae of the soybean pod borer Leguminivora glycinivorella, spend over 9 months (October-next August) in the inactive state until pupation down to 3 cm below the surface in soil. Trehalose content of inactive larvae increases in early winter, attaining a maximum (ca 30 mg/g), and decreases in spring, with a concomitant decrease and increase of glycogen. The median supercooling points seasonally change from ?19.8°C (October) to ?25.0°C (February), and to ?17.0°C (June). The lower supercooling points in winter are in part due to the absence of unusually high values (> ?18°C). The increase in trehalose does not seem to be effective in depressing the supercooling points. The larvae are freeze-intolerant, but ambient temperatures in outdoor conditions are always above the supercooling points. The survival rates are very high throughout the inactive period. 相似文献
55.
The functional human dihydrofolate reductase gene 总被引:54,自引:0,他引:54
M J Chen T Shimada A D Moulton A Cline R K Humphries J Maizel A W Nienhuis 《The Journal of biological chemistry》1984,259(6):3933-3943
56.
Males of the fish Oryzias latipes were treated with various chemicals and then mated with normal females. The fertility and hatchability of the eggs laid by the parents were examined, and the dominant lethal effects were estimated. Mitomycin C induced dominant lethals in the fish spermatids and spermatocytes after the males had been treated with concentrations of 2.5 and 25 micrograms/ml. Methyl methanesulfonate (MMS) induced dominant lethals in spermatozoa and spermatozoa and spermatids after the injection of 200 and 400 mg/kg. These results are in good agreement with the results obtained with mice. However, the effects of ethyl methanesulfonate (EMS) were not clear on spermatogenic cells at any stage. We could not recognize any significant induction of dominant lethals by urethanes, bleomycin, caffeine, and two kinds of food-color additives, at least under the present experimental conditions. 相似文献
57.
Phorbol ester increases the level of interleukin 2 mRNA in mitogen-stimulated human lymphocytes 总被引:8,自引:0,他引:8
T Hirano K Fujimoto T Teranishi N Nishino K Onoue S Maeda K Shimada 《Journal of immunology (Baltimore, Md. : 1950)》1984,132(5):2165-2167
TPA alone did not induce the production of IL 2 in human tonsillar lymphocytes but enhanced the PHA-induced IL 2 production by seven-fold. That the effect of TPA was due to an increase in IL 2 mRNA was demonstrated by examining the amount of IL 2 mRNA translatable in Xenopus laevis oocytes, and by Northern blotting analysis using IL 2 cDNA as a probe. In these ways, it was shown that TPA alone did not induce any significant IL 2 mRNA synthesis, but when added together with PHA it increased the level of IL 2 mRNA by at least 10-fold, as compared with that induced by PHA alone. 相似文献
58.
Enrichment and characterization of clonogenic epithelial cells from adult rat liver and initiation of epithelial cell strains 总被引:8,自引:0,他引:8
Kazunori Furukawa Tomiko Shimada Patricia England Yohichi Mochizuki Gary M. Williams 《In vitro cellular & developmental biology. Plant》1987,23(5):339-348
Summary A highly efficient method is described for obtaining prolifertive epithelial cells from adult rat livers for the reproducible
establishment of liver epithelial cell strains. When cells were isolated from livers of 10-to 15-wk-old male Fischer 344 rats
by a collagenase-perfusion method, collected by centrifugation at 50×g for 5 min, and cultured in Williams' medium E containing fetal bovine serum and dexamethasone, colonies of epithelial cells
different in size and morphology from hepatocytes were obtained. Sequential perfusion with collagenase and dispase yielded
numerous epithelial cell colonies. When isolated cells were fractionated by differential centrifugation, the great majority
of hepatocytes were sedimented at 50 ×g for 1 min, whereas many non-hepatocytic cells remiined in the supernatant and could be sedimented by a second centrifugation
at 50×g for 5 min. Culture of the two fractions revealed that almost all the epithelial cell colonies were derived from cells in
the non-hepatocytic cell fraction. The epithelial cells were cytochemically negative for γ-glutamyl transpeptidase activity,
whereas an increase in the activity was detected in hepatocytes with duration in culture. Ultrastructural characteristics
of hepatocytes were not found in the cells of newly established cell strains. These results suggest that adult rat liver epithelial
cells propagable in culture were derived from a cell type other than the hepatocyte. 相似文献
59.
M Shimada R Shimono T Imahayashi H H Ozaki T H Murakami 《Histology and histopathology》1986,1(4):327-333
In order to investigate the causative factors responsible for removal of mucous coat from the gill lamellae of young yellowtail, Seriola quinqueradiata by red tide, diazo-reactions were employed for planktons and their media. The concentration of NO2- in the medium containing the raphidophyceae, Chatonella antiqua (ca 2000 cells/ml), was 0.70 +/- 0.05 (mu g/ml +/- SEM). In addition, diazo-reaction positive substances (NOx) which may degenerate the mucous, was highly concentrated in the cortex (perikaryon) of Chattonella antiqua. Morphologically, mucocysts, and chloroplats were likewise present in the cortex. Mucocysts were packed with fine fibrous content. Histochemically, the mucocysts were stained with PAS and had an abundance of nitrogen oxides (NOx). We observed discharge of the fibrous material from the mucocysts. These results suggest that when Chattonella antiqua is passing between the gill lamellae, NOx discharged from the mucocysts may act on the mucous, leading to the degeneration and concomitant removal of the mucous coat from gill lamellae. 相似文献
60.
Replication timing: histone genes replicate during early S phase in cleavage-stage embryos of sea urchin. 总被引:2,自引:1,他引:1 下载免费PDF全文
Newly synthesized DNA was separated from the bulk of the DNA by pulse-labeling with BUdR and centrifugation in an alkaline CsCl buoyant density gradient. The content of histone gene in the newly synthesized DNA was determined by DNA dot hybridization. The gene contents in DNA replicated during the early half of S phase and during the whole S phase were compared. Results showed that histone genes were replicated during the first half of the S phase in embryos in the early cleavage stage. 相似文献