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81.
Summary Calcium is released from the isolated heavy sarcoplasmic reticulum (SR) of frog skeletal muscle upon application of 0.1–1 mM diethylpyrocarbonate (DEP, an imidazolyl reagent). The Ca-ATPase activity of SR was suppressed by 20% in the presence of 1 mM DEP. More than 1 mM of free magnesium ion or 5 M ruthenium red eliminated the effect of DEP on calcium release but not on Ca-ATPase activity. A plausible site of DEP action is on the calcium channel. 相似文献
82.
H. -P. Lipp H. Schwegler W. E. Crusio D. P. Wolfer M. -C. Leisinger-Trigona B. Heimrich P. Driscoll 《Cellular and molecular life sciences : CMLS》1989,45(9):845-859
Summary Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural randomization, 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning.In comparison with the classical lesion approach for identifying relationships between brain and behavior, the present procedure appears to be superior in two aspects: it is non-invasive, and it focuses automatically on those brain traits which are used by natural selection to shape behaviorally-defined animal populations, i.e., it reveals the natural regulators of behavior. 相似文献
83.
T. Hatano Y. Kato M. Katayama S. Marumo 《Cellular and molecular life sciences : CMLS》1989,45(4):400-402
Summary A new potent antiauxin, -(5,7-dichloroindole-3-)isobutyric acid has been synthesized and shown to inhibit auxin-mediated elongation ofAvena coleoptiles and to stimulate root growth of rice seedlings. Its activity is stronger than -(p-chlorophenoxy)isobutyric acid and is comparable to that of 2,3,5-triiodobenzoic acid, which are typical antiauxins. 相似文献
84.
H. Nawrath J. Rupp H. Jakob U. Sack F. Mertzlufft W. Dick 《Cellular and molecular life sciences : CMLS》1989,45(4):337-339
Summary The opioid agonists morphine (selective for -receptors) and ethylketocyclazocine (selective for kappa-receptors), at concentrations evoking strong effects in neuronal structures, did not significantly affect the configuration of the intracellularly recorded action potential and the force of contraction in ventricular heart muscle isolated from guinea pigs, rabbits and man. These results suggest that any changes of heart functions in vivo in response to opioid-like drugs are probably not mediated postsynaptically at the myocardial cell membrane but rather presynaptically, influencing the release of noradrenaline and/or acetylcholine from the nerve terminals. 相似文献
85.
Evidence for anoxygenic photosynthesis from the distribution of bacteriochlorophylls in the Black Sea 总被引:7,自引:0,他引:7
The contribution of anoxygenic photosynthesis to carbon cycling in the Black Sea, the world's largest body of anoxic marine water, has been vigorously investigated and debated for over four decades. Penetration of light into the sulphide-containing deep water may result in a zone of anaerobic primary production by photosynthetic bacteria. We report here the results of analyses of photosynthetic pigments in samples of suspended particulate matter collected from two stations in the western basin of the Black Sea. Our data demonstrate high concentrations of a bacterio-chlorophyll at the chemocline, and thus the potential for anoxygenic photosynthesis as a component of primary production in the carbon cycle of the Black Sea. More than 95% of the pigments in the bacteriochlorophyll-maximum are accounted for by a series of aromatic carotenoids and bacteriochlorophylls-e, including a previously unreported geranyl ester of 4-i-butyl bacteriochlorophyll-e. The distribution of pigments is characteristic of the obligate phototrophs Chlorobium phaeobacteroides and C. phaeovibriodes. Total depth-integrated bacteriochlorophyll at one station exceeded total chlorophyll-a in the overlying oxygenated portion of the euphotic zone. We suggest that anoxygenic photosynthesis is a relatively recent phenomenon in the Black Sea initiated by shallowing of the chemocline over the past decade and development of an anoxic layer devoid of O2 and H2S. 相似文献
86.
This article briefly discusses the the new fossil assemblage found in the 600-650-million-year-old shales of the Pertatataka formation in central Australia. It includes about two dozen taxa of spinose, process-bearing or otherwise ornamented acritarchs, many of them extremely large relative to comparably ornamented fossils in younger rocks. These acritarchs reveal a glimpse of early evolution and Proterozoic life. 相似文献
87.
H. Underwood 《Cellular and molecular life sciences : CMLS》1989,45(10):914-922
Summary The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a multioscillator circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world. 相似文献
88.
Summary Apart from cancer and mutation induction, radiobiological effects on mammals are mostly attributable to cell death, defined as loss of proliferative capacity. Survival curves relate retention of that capacity to radiation dose, and often manifest a quasi-threshold (shoulder). The shoulder is attributable to an initial mechanism of repair (Q-repair) which is gradually depleted as dose increases. Another form of repair, which is not depleted (P-repair), increases the dose required to deliver an average of one lethal event per cell (dose D0). Neither form of repair can unambiguously be linked with repair of defects in isolated DNA. An important initial lesion may well be disruption of the complex structural relationship between the DNA, nuclear membrane and associated proteins. One form of P-repair may be restoration of that structural relationship. 相似文献
89.
B. Lindblad W. E. Burkel T. W. Wakefield L. M. Graham J. C. Stanley 《Cellular and molecular life sciences : CMLS》1988,44(3):223-224
Summary The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF1 and TxB2 was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5×10–3 to 5×10–7 g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented. 相似文献
90.