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P. P. Nelson 《Bulletin of mathematical biology》1964,26(3):255-263
Résumé Le sommeil est caractérisé d'une part par une inhibition généralisée du cortex, d'autre part par une synchronisation totale
du cœur, des poumons, et du cortex. Les états répondant à ces conditions correspondent à des bilans énergétiques bien déterminés.
Les phénomènes transitoires résultent essentiellement de l'action du centre régulateur de métabolisme. D'autres états totalement
synchronisés existent: marche, vol des oiseaux. Dans un tel état synchronisé, un individu possède la notion de temps. 相似文献
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Lucienne Fenaux Yves de Greef Christiane Cellario 《International Review of Hydrobiology》1992,77(4):651-663
The growth of the skleleton and changes in biochemical constituents (proteins, carbohydrates and lipids) were observed in embryos (days 0 and 1) and larvae (2-8 days) of the sea urchin Paracentrotus lividus that were starved (C 0) or fed low (1,000 cells of Hymenomonas elongata, C 1) or high (5,000 cells, C 5). Different batches of C 1 and C 5 larvae were fed first the 2nd, 3rd, 4th or 5th day after fertilization. Initiation of feeding 24 h after hatching slowed down the rate of increase in length of the larval appendages. A differential growth of skeletic rods (somatic and postoral rods) and variations in proteins weights shows the existence of a mixotrophic phase between endotrophic and planktotrophic phases. Best development occured in larvae which were first fed at the lower food level 24 h after hatching. On the 2nd and the 3rd day the somatic/postoral rod ratio is ≥1. This higher ration can be used to estimate the age of natural populations of larvae. 相似文献
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Sans résumé 相似文献
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Preliminary Study of the Effects of Impoundment of LG-2 Reservoir (James Bay Territory, Quebec) on the Net Seston and the Zooplankton of Impounded Rivers and Lakes The effects of impoundment on the biomass of net seston and zooplankton in lakes and rivers of Northern Quebec were investigated from 1978 to 1980, before, during and after the completion of LG2 Reservoir on the River La Grande (53° 54′ N, 76° 78′ W). In lotic stations, a 41–77% decrease in net seston was observed due to sedimentation of mineral particles (36–80 mg/m3 in 1978 to 10–21 mg/m3 in 1979). The ratio of organic to total seston increased from an average of 0.18 before the impoundment to 0.65 after. The flooding phase brought about a trophic upsurge; the biomass of the zooplankton increased by one to two orders of magnitude at the various sites; the greatest increases occurred in the central stations near the dam, the smallest in the upper stations near the inflow. In lake stations, no significant difference between years could be detected; the mean zooplankton biomass for all three years ranged from 6.59 mg/m3 to 34.34 mg/m3. Spatial variations between lakes were however significant. Results are compared with those in other natural lakes in Canada and reservoirs in the United States. Comparative examination of phytoplankton biomass before and after impoundment of LG2 Reservoir suggests that bacterioplankton and allochthonous organic material are key elements in the pelagic food chain after impoundment. 相似文献
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Water stress, induced by addition of polyethyleneglycol 600 to the nutrient solution, reduces the ribonucleic acid content of cotton leaves. The chloroplastic compartment, especially its ribosomal fraction, was most affected, even losing ribonucleic acid to the cytoplasmic compartment. Decrease of ribonucleic acid content on dehydration of leaf tissue is linked with an increase of ribonuclease. 相似文献
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E. Sacquet C. Méjean C. Leprince M. Riottot 《Biochimica et Biophysica Acta (BBA)/General Subjects》1977,499(1):67-72
Axenic and holoxenic (conventional) rats were fed a diet containing trace amounts of [2,4-3H]cholic and [24-14C]chenodeoxycholic acids. In the feces of both groups of rats, the percentage of labelled bile acids which were 3H-labelled was slightly different. In the experimental conditions used, the intestinal microflora only slightly modified the synthesis of 12α-hydroxylated bile acids. 相似文献
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A. Lyoussoufi C. Gadenne R. Rieux et F. Faivre d'Arcier 《Entomologia Experimentalis et Applicata》1994,72(3):239-244
The nature of the responses of the sheep blowfly Lucilia sericata Meigen (Diptera: Calliphoridae) to carrion odours and carbon dioxide were examined in a windtunnel in the laboratory and the attractiveness of carrion-bait was examined in the field. In the wind tunnel, gravid 9-day-old females increased both the number and duration of their flights, in response to carrion odours. In addition, linear velocity was reduced and the sinuosity of flight increased in the presence of these odours. With 3-day-old females, the response to carrrion odour depended on previous exposure to proteinaceous material. Protein deprived females showed kinetic responses to carrionodour which were similar to those of gravid females. No such changes were observed in protein-fed females. No responses to CO2 were observed. In the field, the importance of olfactory cues in bait location was demonstrated by the absence of L. sericata from sticky targets lacking an odour bait. Increased bait concentration did not affect the age, sex ratio or ratio of L. sericata to other Lucilia spp. caught, but did increase the numbers caught. Analysis of the reproductive status of females caught, indicated that a greater number of gravid females were caught than expected, while a lower number of females in the final stages of vitellogenesis were caught than expected. The results show that the responses of L. sericata to odours are complex, and are dependent on both exogenous and endogenous stimuli, the latter including the stage of ovarian development. 相似文献