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141.
Graham N. Stone Andy Purvis 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(3):284-295
Summary This study examines the relationship between warm-up rate, body mass, metabolic rate, thermal conductance and normothermic body temperature in heterothermic mammals during arousal from torpor. Predictions based on the assumption that the energetic cost of arousal has been minimised are tested using data for 35 species. The observation that across-species warm-up rate correlates negatively with body mass is confirmed using a comparative technique which removes confounding effects due to the non-independence of species data due to shared common ancestry. Mean warm-up rate during arousal correlates negatively with basal metabolic rate and positively with the temperature difference through which the animal warms, having controlled for other factors. These results suggest that selection has operated to minimise the overall energetic, cost of warm-up. In contrast, peak warm-up rate during arousal correlates positively with peak metabolic rate during arousal, and negatively with thermal conductance, when body mass has been taken into account. These results suggest that peak warm-up rate is more sensitive to the fundamental processes of heat generation and loss. Although heterothermic marsupials have lower normothermic body temperatures and basal metabolic rates, marsupials and heterothermic eutherian mammals do not differ systematically in warm-up rate. Pre-flight warm-up rates in one group of endothermic insects, the bees, are significantly higher than predictions based on rates of arousal of a mammal of the same body mass.Abbreviations BMR
basal metabolic rate
- ICM
independent comparisons method
- MWR
mean warm-up rate
- PMR
peak metabolic rate
- PWR
peak·warm-up rate
-
Tbactivity
body temperature during activity
-
Tbtorpor
body temperature during torpor
- T
arousal
increase in body temperature during arousal 相似文献
142.
Khalid M. Chraibi B. Alain Latche Jean-Paul Roustan Jean Fallot 《Plant cell reports》1991,10(4):204-207
The effects of CoCl2, AgNO3 and ethylene released by exogenous 2-chloroethylphosphonic acid (Ethephon), were studied on shoot regeneration from cotyledons of Helianthus annuus cv. E8206R, a poorly regenerative cultivar. Inhibition of ethylene biosynthesis by CoCl2, at concentrations of 20 K, provoked a substantial enhancement of shoot regeneration (30 %): the control was poorly regenerative. However, CoCl2 had no effect when Ethephon was supplied. Inhibition of ethylene action by AgNO3, at concentrations of 10–25 M, caused a significant increase in plant regeneration: 25 % instead of 1.2 % in the control. Furthermore, addition of Ethephon to AgNO3-treated tissues failed to reduce the stimulation of shoot regeneration caused by AgNO3. On the basis of these findings, it is suggested that ethylene inhibits the regeneration process from cotyledons of sunflower.Abbreviations NAA
1-naphthalene acetic acid
- BAP
6-benzylamino-purine
- GA3
gibberellic acid
- Ethephon
2-chloroethylphosphonic acid
- MS
Murashige and Skoog medium
- AVG
aminoethoxyvinylglycine 相似文献
143.
Summary We report here an improved method for nuclei counting utilizing Triton-X 100 to reduce the size of cell debris, thereby allowing the use of a particle sizer/counter. Furthermore, nuclei are completely released within 30 seconds, as compared to 1 hour using hypotonic solution. The method is accurate above 0.3 × 106 cells/mL. 相似文献
144.
Barry S. Cooperman Alain Expert-Bezançon Lawrence Kahan Jacques Dondon Marianne Grunberg-Manago 《Archives of biochemistry and biophysics》1981,208(2):554-562
We here report the results of using three light-dependent procedures for crosslinking IF-3 to 30 S proteins within an IF-3·30 S complex. In the first procedure, employing FMN as a photosensitizer, protein S12 is found to be the only major crosslinked protein. In the second procedure, IF-3 is first reacted with the new two-stage crosslinking reagent, p-nitrobenzylmaleimide (PNBM), and the PNBM—IF-3·30 S complex is irradiated. The major crosslinked proteins are S3 > S2, S12, S18. Small amounts of crosslinked S11 and S21 are also found. In the third procedure, the IF-3·30 S complex is reacted with PNBM and then irradiated. The major crosslinked proteins are S12 > S3 > S11 and small amounts of crosslinked S1, S13, and S21 are also found. These results are compared with results obtained by others using different crosslinking procedures and are used to discuss the Lake and Kahan model (J. A. Lake and L. Kahan, 1975, J. Mol. Biol., 99, 631–644, and J. A. Lake, 1978, in Advanced Techniques in Biological Electron Microscopy II, Koehler, J. K., ed., pp. 173–211, Springer-Verlag, Berlin) for IF-3 binding to 30 S subunits. 相似文献
145.
The authors recall some data concerning the distribution, the ecology and the taxonomy of Nuia and describe in detail its mode of growth, distinguished by 6 different growth-forms. 相似文献
146.
In extracts from Zea mays shoots, the presence of thiol compoundsin the extraction buffer was necessary to get an active 3 deoxy-D-arabinoheptulosonic acid 7-phosphate (DAHP) synthase. Its pH optimumfor activity was about 7.5. Of the different cations tested,only Mn++ was an activator. Enzyme stability was optimal inTris-HCl buffer, pH 7.5, that contained a reducing agent, Mn++and a polyol. Contrary to other reports, phosphoenolpyruvate(PEP) did not stabilize the preparation significantly. The synthaseexhibited high affinities for both erythrose-4-phosphate (Km:0.24 mM) and PEP (Km: 0.31 mM). Its specific activity was highestin young shoots. Corn DAHP synthase was inhibited in vitro by tryptophan. Moreover,the enzyme was retarded on a tryptophan agarose affinity column,but it was removed with the bulk of protein from the same supportwhen eluted with buffer containing tryptophan. Inhibition whichwas easily lost during storage at 4°C was pH dependent andincreased during development. Maximal inhibition, about 60%with 1 mM tryptophan, was observed in extracts from 8 day-oldshoots. Phenylalanine and tyrosine were not inhibitory, andno synergistic effects were observed when the aromatic aminoacids were tested in combination. Isoenzymes could not be demonstrated. (Received April 23, 1980; ) 相似文献
147.
148.
Alain B. Schreiber Johan Hoebeke Bernard Vray A. Donny Strosberg 《Experimental cell research》1981,132(2)
The association and dissociation mechanisms of lectin membrane receptor microclustering on HeLa cells have been studied by measuring resonance energy transfer between fluoresceinated and rhodaminated lentil lectin. Compounds known to affect membrane receptor mobility, such as Ca2+ ions, methylamine, cytochalasin D and nocodazole, did not modify the association kinetics nor the maximal energy transfer values at 4 and 37 °C. Dissociation of the membrane receptor microclusters was followed by measuring the temporal decrease in energy transfer values at 4 °C after preincubation for different time intervals at 37 °C. The rate of dissociation of the lectin receptors decreased in the presence of Ca2+ ions (10−3 M) and after cross-linking with anti-lectin antibodies. An increase was observed in the presence of cytochalasin D (10−6 M) and, to a lesser extent, of methylamine (10−2 M). When cytochalasin D and methylamine were combined at subliminal concentrations, a partial synergistic effect was observed. Nocodazole (10−6 M) had no effect. The results suggest that the association of lectin membrane receptors in microclusters is mediated only by physicochemical parameters. Ca2+ ions, cytochalasin D (microfilaments) and methylamine (transglutaminase)-sensitive components appear, however, to play an important role in the stabilization of the receptor microclusters. 相似文献
149.
Using mouse thymocytes, mitogen-induced [3H]thymidine incorporation was compared with a recently developed flow-cytometric technique, based on acridine orange staining of cells, which differentiates the G0 and G1 phase of thymocytes. PHA induces a transient but considerable G0-G1 shift without any substantial proliferation. On the other hand, crude supernatants derived from Con A-stimulated human peripheral blood mononuclear cells induce only a minor G0-G1 shift and no proliferation. However, PHA in the presence of this supernatant induced an increased [3H]thymidine uptake in thymocytes and a shift from G1 to S. These results support the current hypothesis that a factor present in Con A-activated supernatants in conjunction with PHA stimulation indeed facilitates the entrance of G1 cells into the S phase. The flow-cytometric technique might be used in the study of the interaction of endogenous mediators with exogenous mitogenic agents in activating lymphocytes to proceed through the initial G0-G1 phases of the cell cycle. 相似文献
150.
Four strains of both Taphrina pruni and T. institiae were cultivated under identical conditions and and lipids and fatty acids were quantitatively analysed at two stages of their development. Tri- and diglycerides are the major neutral lipids in both species. Phosphatidylcholine and phosphatidylethanolamine are the most abundant polar lipids. Qualitatively, the two species show identical fatty acid contents, except for margaric acid (17:0) which was only found in Taphrine pruni. Quantitatively there are several differences: palmitoleic acid (16:1) occurs in reasonable amounts regularly and only in Taphrina pruni. The ratios 16:0/18:0 and 18:1/18:2 are generally higher for T. insititiae whereas the degree of unsaturation of fatty acids is higher in the former. The results are discussed with regard to data on other fungal species. 相似文献