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Long-term potentiation (LTP) of synaptic strength, the most established cellular model of information storage in the brain, is expressed by an increase in the number of postsynaptic AMPA receptors. However, the source of AMPA receptors mobilized during LTP is unknown. We report that AMPA receptors are transported from recycling endosomes to the plasma membrane for LTP. Stimuli that triggered LTP promoted not only AMPA receptor insertion but also generalized recycling of cargo and membrane from endocytic compartments. Thus, recycling endosomes supply AMPA receptors for LTP and provide a mechanistic link between synaptic potentiation and membrane remodeling during synapse modification. 相似文献
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The level of the plasma prothrombin in the circulating blood is decreased during its passage through the pulmonary capillaries. In 85 per cent. of samples, plasma prothrombin has been found to be less in the blood of the left ventricle than in that from the right ventricle. This difference averaged 10.6 per cent. and ranged from 4 to 19 per cent. In no instance was the level in the right ventricle lower than that in the left. In samples of blood taken from the arterial and venous supply of the head, liver, spleen, intestine, kidney and hind limbs, no significant difference in plasma prothrombin levels was found. A possible explanation of this role of the lung in the loss of plasma prothrombin is thought to be the production of blood platelets in this organ, as demonstrated by Howell and Donahue. Platelets, as they undergo disintegration, initiate the first stage of the clotting process by releasing thromboplastin, which, in the presence of calcium, changes prothrombin to thrombin. 相似文献
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Von B. Kauer 《Anatomia, histologia, embryologia》1976,5(2):122-134
A study of the early development of the heterozygous short-tail mouse (T/+) Because of the great variability during early development, it is recommended for age determination of mouse embryos to consider also features of growth; in the succeeding stages the somites and the three humps (Buckel) provide firm criteria. Since murine types differ from each other in certain features, there is no uniform conception of the kind and the form of the tissues that are affected in gene disturbances. In contrast to the current conception that in the t-mutant the disturbance arises primarily from the chorda dorsalis, the author's findings lead to the conclusion that the neural tube and the cardiovascular system are primarily involved. Chorda disturbances apparently occur in the so-called normal mouse similar to the way they occur in T/t-mutants. Because of the often observed connection between chorda and neural tube, it is possible that neurectoderm is involved in the formation of the chorda; and because of this anomalies of the neural tube in the heterozygous short-tail mouse gain significance. Mesodermal defects were rarely present in the T/t-mutant, while are very impressive in the early development of the short-tail mouse. They are thougth to be related to a rise in blood pressure occasioned by peripheral disturbance of blood flow. 相似文献
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Eurasian Soil Science - Soil formation on the human time scale is immensely time consuming, although it can be significantly accelerated through the effects of vegetation. The content of... 相似文献
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Karin Kauer Henn Raave Tiina Köster Rein Viiralt Merrit Noormets Indrek Keres 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):224-234
Abstract In grassland areas where herbage production has no economic value, the cut grass is often left on the sward surface where its decomposition is influenced by weather conditions. Although the influence of temperature and humidity on decomposition has been investigated under controlled lab conditions, experimentation has generally been under ideal moisture conditions that have not tested the combinations of climatic limitations that might occur in the field. The decomposition of mown turfgrass clippings deposited at different times of vegetation period was studied in situ using nylon bags during the first 8 weeks after deposition to investigate the effect of weather conditions (the air temperature, relative humidity, precipitation) on decomposition. Decomposition is the highest in the case of high air humidity and temperature of 10°C. Limiting factors for decomposition at temperatures above 10°C is the air humidity and below 10°C the air temperature. The general tendency was that the rate of decomposition increased with increasing air temperature up to 10°C, but with further increases of air temperature the decomposition rate slowed down. Relative air humidity had a variable impact (at the beginning of the decomposition process (weeks 1–2) the influence was negative, during weeks 3–8 of the decomposition process the effect was positive), and hence had no generalized relationship with decomposition over the studied decomposition period (weeks 1–8). The most significant influence of weather conditions on the decomposition rate was recorded directly after cutting. If the cutting was done during hot weather conditions, the material was drying fast and therefore decomposed slowly. Our results indicate that for fast decomposition of clippings it is important to maintain the freshness of material. Lower decomposition rates occurred during conditions of hot and dry weather, and also cooler (temperature near to 0°C) weather, and can be compensated as soon as favourable weather arrives. 相似文献
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Postsynaptic calcium is sufficient for potentiation of hippocampal synaptic transmission 总被引：31，自引：0，他引：31
Brief repetitive activation of excitatory synapses in the hippocampus leads to an increase in synaptic strength that lasts for many hours. This long-term potentiation (LTP) of synaptic transmission is the most compelling cellular model in the vertebrate brain for learning and memory. The critical role of postsynaptic calcium in triggering LTP has been directly examined using three types of experiment. First, nitr-5, a photolabile nitrobenzhydrol tetracarboxylate calcium chelator, which releases calcium in response to ultraviolet light, was used. Photolysis of nitr-5 injected into hippocampal CA1 pyramidal cells resulted in a large enhancement of synaptic transmission. Second, in agreement with previous results, buffering intracellular calcium at low concentrations blocked LTP. Third, depolarization of the postsynaptic membrane so that calcium entry is suppressed prevented LTP. Taken together, these results demonstrate that an increase in postsynaptic calcium is necessary to induce LTP and sufficient to potentiate synaptic transmission. 相似文献
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A survey on taxonomy, diagnosis, distribution and pathogenicity of Cryptococcus neoformans is given. The investigation presented here concerns 1046 fecal samples of avian species, which can be kept in the living area of humans. All together only 15 strains have been isolated, 9 of which originated from the same breeder. 相似文献
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Michael C. Melnychuk Charmane E. Ashbrook Richard J. Bell Lyall Bellquist Kate Kauer Jono R. Wilson Ray Hilborn Jay Odell 《Fish and Fisheries》2023,24(5):711-729
The status of federally managed fisheries in the United States is well monitored, but the condition of other marine fisheries, whether state-managed, territory-managed or unmanaged, is less understood and often unknown. We used expert surveys to characterize the management systems of non-federally managed fisheries in US coastal marine states and overseas territories. For 311 fisheries, we estimated an overall Fisheries Management Index (FMI) and a qualitative stock status score. These measures were positively correlated, and while a wide range of research, management, enforcement and socioeconomic criteria were partially met (FMI ≥ 0.5) for 66% of fisheries, stock status was considered as partially acceptable (score ≥ 0.5) for only 45% of fisheries and acceptable (score = 1) for only 16% of fisheries. Higher FMI was typically observed in fisheries with greater commercial landed weight, value, or greater recreational catches. Fisheries from continental states had higher FMI than those from overseas territories. Invertebrates and diadromous fish species had higher FMI on average compared to those of marine fishes. Extrapolating results for surveyed fisheries to nearly 2000 non-federally managed US fisheries while stratifying by state and importance designation (based on commercial, recreational, cultural or ecological importance), we estimate a mean overall FMI of 0.48, and estimate that only 19% of fisheries have a reliable estimate of stock status available; both measures are lower than similar estimates for federally managed fisheries. Funding or capacity constraints and information or data limitations were identified as common challenges faced by state agencies in managing fisheries under their jurisdiction. 相似文献