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ANDRÉ PICARD JEAN-CLAUDE LABBÉ GÉRARD PEAUCELLIER FRANÇOISE LE BOUFFANT CHRISTIAN LE PEUCH MARCEL DOREE 《Development, growth & differentiation》1987,29(1):93-103
Many studies suggest that MPF activation depends on protein phosphorylation or that MPF is itself a protein kinase. In the present report, cyclic variations of MPF activity have been correlated in vivo with changes in the extent of protein phosphorylation or in vitro with changes of a major protein kinase during the first cell cycles of fertilized starfish eggs. This cycling protein kinase neither requires cAMP nor Ca2+ . Neither colchicine nor aphidicoline, which inhibits cleavage and chromosome replication respectively, was found to suppress the synchronous and cyclic variations of both MPF and protein kinase activities. Protein synthesis was found to be required for both MPF and protein kinase activities to reappear after their simultaneous drop at the time of mitotic or meiotic cleavages. Production of either MPF or protein kinase activities is not the immediate result of protein synthesis since there is a delay at each cell cycle between the time when protein synthesis is required and the time when both MPF and protein kinase activities are produced. This suggests that both MPF and protein kinase activities might involve some post-translational modification of a precursor protein synthesized during the preceeding cell cycle. 相似文献
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中国平脉树螽属五新种记述:直翅目:螽斯科:树螽亚科 总被引:2,自引:0,他引:2
本文报道中国平脉树螽属5个新种。每个新种皆有详细的形态描述和形态特征图。所有模式标本存于北京农业大学昆虫标本室。 相似文献
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Prevost, I. and Le PageDegivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.J.exp. Bot. 36: 19001905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radioimmunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability 相似文献
7.
Tomato fruit ripening and ethylene production were inhibited following treatment with methyl bromide (MB). Methyl bromide significantly delayed ripening initiation in mature-green (MG) fruit and retarded the rate of ripening of turning (T) fruit as measured by color development and flesh softening. Treatment with MB caused an initial transient burst of ethylene production, but the subsequent ripening-associated increase in ethylene was delayed. Ethylene treatment partially overcame MB inhibition in MG fruit but had no affect on T fruit. The inhibition of ethylene production by MB appears to be due to lack of formation of 1-aminocycloprone-1-carboxylic acid (ACC) in MG fruit, whereas in T fruit lack of conversion of ACC to ethylene is indicated. A key feature of MB inhibition of ripening in tomato appears to be reduced sensitivity to ethylene. 相似文献
8.
Chylomicron-chylomicron remnant clearance by liver and bone marrow in rabbits. Factors that modify tissue-specific uptake 总被引:2,自引:0,他引:2
M M Hussain R W Mahley J K Boyles M Fainaru W J Brecht P A Lindquist 《The Journal of biological chemistry》1989,264(16):9571-9582
The metabolism of [14C]cholesterol- and [3H]retinol-labeled chylomicrons obtained from canine thoracic duct or rabbit mesenteric lymph was investigated in normal fasted rabbits. Typically, 70-80% of the chylomicrons injected into the rabbits were cleared from the plasma in 20 min, and their uptake was accounted for principally by the liver and the bone marrow. Surprisingly, the bone marrow was a major site of uptake; the uptake ranged from about half that of the liver to a nearly equal amount. The importance and specificity of chylomicron-chylomicron remnant uptake by the bone marrow were established by demonstrating that (a) bone marrow throughout the body accumulated these lipoproteins, (b) the level of uptake was consistent regardless of how the values were calculated or how the chylomicrons were prepared, (c) the uptake represented specific binding, and (d) radiolabeled intestinal lipoproteins induced in vivo delivered cholesterol and retinol to the marrow. Electron microscopic examination of the rabbit bone marrow established that perisinusoidal macrophages uniquely accounted for the uptake of the chylomicrons. Whereas liver cleared a variety of both triglyceride-rich lipoproteins (chylomicrons, chylomicron remnants, and very low density lipoproteins) and cholesterol-rich lipoproteins (beta-very low density lipoproteins and high density lipoproteins containing apolipoprotein E), bone marrow uptake appeared to be restricted to the triglyceride-rich lipoproteins. More chylomicron remnants (generated in a hepatectomized rabbit) were cleared by the liver than by the bone marrow, and the addition of excess apolipoprotein E to chylomicrons resulted in their preferential uptake by the liver. The role of chylomicron-chylomicron remnant delivery of lipids or lipid-soluble vitamins to rabbit bone marrow is open to speculation, and whether triglyceride-rich lipoprotein uptake occurs to a significant extent in the bone marrow of humans remains to be determined. 相似文献
9.
Monitoring the persistence of Laccaria bicolor as an ectomycorrhizal symbiont of nursery-grown Douglas fir by PCR of the rDNA intergenic spacer 总被引:2,自引:0,他引:2
B. HENRION C. DI BATTISTA D. BOUCHARD D. VAIRELLES B. D. THOMPSON † F. LE TACON F. MARTIN 《Molecular ecology》1994,3(6):571-580
The large-scale inoculation of selected beneficial ectomycorrhizal fungi in forest nurseries has generated renewed interest in the ecology of these symbiotic fungi. However, information on the dissemination and persistence of introduced symbionts is scarce due to the limitation of the current identification methods. To identify ectomycorrhizal fungi on single root tips, we investigated the polymorphism of the PCR-amplified ribosomal DNA intergenic spacer (IGS) from a wide range of ectomycorrhizal fungi. To investigate the reliability of this molecular approach in large-scale surveys, the dissemination and persistence on Douglas fir seedlings of the introduced Laccaria bicolor S238N were assessed in a forest nursery in the Massif Central (France). Several hundred ectomycorrhizas and fruiting bodies were sampled from plots where control and L. bicolor inoculated-Douglas fir seedlings were grown for 1.5 years. PCR typing of mycorrhizas indicated that trees inoculated with L. bicolor S238N remained exclusively colonized by that isolate (or sexually derived isolates) for the entire test period. In contrast, control seedlings were infected by indigenous isolates of Laccaria laccata and Thelephora terrestris. The molecular evidence for the persistence of the introduced mycobiont despite the competition from indigenous isolates of the same species provides further illustration of the potential of exotic species for large-scale microbial application. 相似文献
10.
Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis) 总被引:4,自引:0,他引:4
Analysis of the heat-shock proteins (hsps) of six closely related species
of Poeciliopsis demonstrated the existence of biochemical diversity in the
hsp100, hsp70, hsp60, and hsp30 protein families among species. Each
species expressed five to seven hsp70-related isoforms. Constitutive 70-kD
isoforms were identical among species, but four different patterns of
heat-inducible isoforms were seen in these six species. Members of the
hsp70 family of molecular chaperones are included among the most highly
conserved proteins known, and the possibility of variation in hsp70 among
closely related species has rarely been addressed. The hsp30 family is
known to be less conserved than the hsp70 family, and, as expected, the
Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30
isoforms characteristic of a particular species were unique to that
species. Hsp100 and hsp60 were identical in five of the species, but
alternate isoforms were found in P. monacha. The small size and limited
geographical distribution of the P. monacha population have probably
contributed to the uniqueness of the monacha pattern. Two of the species
were shown to acquire thermotolerance, the ability to withstand normally
lethal temperatures when subjected to a gradual temperature increase.
Rapid-heating protocols commonly used to establish critical thermal maxima
of organisms do not include this inducible component of thermoresistance
and therefore do not adequately assess an organism's capacity to withstand
thermal stress.
相似文献