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1.
Pacemaker Properties of Completely Isolated Neurones in <Emphasis Type="Italic">Aplysia californica</Emphasis> 总被引:1,自引:0,他引:1
SINGLE-CELL pacemaker activity is interesting because of its function in temporal organization and information processing in the nervous system. Many invertebrate neurones are regularly and autonomously active1,2. Although the pacemaker rhythm probably originates within the recorded neurone, it is not clear whether it originates in the axonal tree or in the cell soma. Alving3 approached this question by studying pacemaker activity in the soma of Aplysia nerve cells, after ligaturing the axonal stem with fine sutures. The study described here presents evidence that nerve cell somata which are completely dissociated from all surrounding tissue and with or without axons, are able to maintain regular autorhythmic activity for periods of more than 24 h. The method of complete isolation of cells represents some progress over Alving's method because it is easier to accomplish, has a larger yield of viable neurones and allows longer recording periods. 相似文献
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Tetsuo ARAI Ju-Peng LIU Chun-Mei HUANG Xin-Yue CHENG Yasuhiko WATARI Makio TAKEDA 《Entomological Science》2004,7(3):237-244
Photoperiodic regulation of nymphal development was examined in four species of cricket collected in the Xinjiang‐Uygur Autonomy Region, China (approximately 43°N, 81–89°E). Fifty percent of individuals of Modicogryllus frontalis reared at 28°C reached adulthood in approximately 80 days in conditions of 11 h light : 13 h dark (LD 11:13) to 14:10, and in approximately 95 days under LD 15:9 to 16:8. Melanogryllus desertus started adult emergence earliest under LD 16:8 at 28°C, but some individuals required much longer to mature, and thus two peaks of adult emergence occurred at approximately 60 and 160 days after hatching. More individuals hatched during the late peak in LD 18:6 than in LD 16:8. The mean nymphal period was approximately 100 days in LD 11:13 to 14:10. Both species showed short‐day type photoperiodic responses, but Mo. frontalis developed faster than did Me. desertus. The latter occupied a wider range of habitat conditions and was more variable in life cycle than the former. Modicogryllus burdigalensis started adult emergence earliest in LD 16:8 at 28°C in the six photoperiods tested, most adults emerging within 60 days. The mean nymphal period was 80 days in LD 15:9, 135 days in LD 14:10 and 80–100 days in LD 11:13 to 13:11, showing an intermediate type of photoperiodic response. Acheta domesticus was a long‐day type species, and the proportion of delayed individuals increased with decreasing photoperiod. In the dry climate of Xinjiang‐Uygur, nymphal overwintering seems to be successful in all of the four different patterns of nymphal development. 相似文献
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During the ripening stage of barley and rice, the sink activitywas defined as the dry matter increase per units sink size,leaf area and time, as follows: NAR = A.SinkW+NAR', where NAR is the net assimilation rate (g d.wt dm2d1);A is the sink activity [g d.wt g1d.wt (ear) dm2d1]; Sink W is ear wt per plant at heading (g d.wt);and NAR' is net assimilation rate excluding the assimilate ofsink organ (g d.wt dm2 d1). Plant material with 16 combinations of mutually different sink(ear) and source (leaf) size were produced at heading for eachcrop: parts of each leaf and ear were removed to produce fourgrades in barley, and also a part of each leaf was removed producingfour grades for four rice varieties showing different ear size.NAR and NAR' were determined during 26 and 21 d in barley andrice after heading, respectively. Sink activity (A), representedas the assimilation rate induced by the sink organ, was estimatedfrom the relationship between SinkW and NAR using the previousequation. The sink activity was significantly higher in ricewith a value of 00.028 g d.wt g1 d.wt (ear) dm2d1 vs. 00.0017 in barley, suggesting that therelative role of leaves for grain filling is considerably higherin rice than in barley. The sink activity obtained in the studymight be introduced into a model to predict the yields of barleyand rice. Hordeum vulgare L, barley, Oryza saliva L, rice, dry matter, NAR, sink, source, sink activity, model 相似文献
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Normal human epidermal melanocytes became swollen and more dendritic with an increase in the amount of tyrosinase and immunoreactive b-locus protein when they were cultured for 2 days with the following arachidonic acid metabolites: prostaglandin (PG) D2, leukotriene (LT) B4, LTC4, LTD4, LTE4, thromboxane (TX) B2 and 12-hydroxy eicosatetraenoic acid (12-HETE). The effect of LTC4 was particularly strong compared to that of PGE2, about which we have previously reported. On the other hand, PGE1, PGF2α and 6-ketoPGF1α did not show any significant stimulatory effect. These data suggest that arachidonate-derived chemical mediators, especially LTC4, may be responsible for the induction of post-inflammatory hyperpigmentation of the skin. 相似文献
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Phenotypic plasticity of internode elongation stimulated by deep-seeding and ethylene in wheat seedlings 总被引:2,自引:0,他引:2
Deep-seeding and ethylene were found to stimulate extension growth of the first internode of intact wheat (Triticum aestivum L.) seedlings in darkness. Seedlings of Hon Mang Mai emerged from much deeper in the soil than the seedlings of the other varieties used and their first internodes elongated to a much greater extent in response to ethylene. Carbon dioxide slowed elongation of the first internode and inhibited ethylene action. Elongation of the first internode due to deep-seeding and ethylene treatment showed high heritabilities, suggesting a genetic basis underlying those traits. 相似文献
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TAKEDA JUNKO; MORIKAWA HIROMICHI; KINOSHITA HIDEAKI; SENDA MITUGI 《Plant & cell physiology》1971,12(6):949-960
Permeability coefficients for the cell membrane of Nitella jlexilishave been determined for some organic substances by measuringtheir transcellular transport with the double chamber method.Benzyl alcohol is rapidly taken up in the vacuole of the cell.In the double chamber method benzyl alcohol taken up in thevacuole at one end of the cell is not as rapidly transportedto the other end as expected from the rate of protoplasmic streamingin the vacuole. This can be explained by assuming the presenceof a "non-streaming part" in the vacuole. The uptake of ureainto the streaming part of the cell is stimulated by directlyilluminating the part where the cell is immersed in urea solution. (Received March 10, 1971; ) 相似文献