Changes in the Activity of the Maturation-Promoting Factor Are Correlated with Those of a Major Cyclic AMP and Calcium-Independent Protein Kinase During the First Mitotic Cell Cycles in the Early Starfish Embryo

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.     

中国平脉树螽属五新种记述：直翅目：螽斯科：树螽亚科

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。     

Inactivation of detergent-solubilized sarcoplasmic reticulum ATPase

Inactivation of sarcoplasmic ATPase in the solubilized state was studied in the absence and presence of Ca2+, Mg2+ and glycerol. The effects of the detergents octa(ethyleneglycol) mono-n-dodecyl ether (C12E8), 1-O-tetradecylpropanediol-(1,3)-3-phosphorylcholine and myristoylglycerophosphocholine were compared. All three detergents caused a rapid decline of the dinitrophenyl phosphatase activity of the unprotected enzyme. The stabilizing effect of Ca2+ ions was kinetically analysed. It was found that the stability of the solubilized enzyme depends on the Ca2+ concentration in a manner which is best explained by assuming rapid inactivation of Ca2+-free enzyme accompanied by slow inactivation of a calcium-enzyme complex (E1Ca). The apparent affinity constants obtained are in the order of 10(6)M-1, suggesting that high-affinity Ca2+ binding must be involved. No indications of a contribution were found, either of low-affinity Ca2+-binding sites of the conformational state E2 or of the high-affinity calcium complex E1Ca2. If Ca2+ was replaced by Mg2+, which exerts a weaker protection, the apparent affinity constants for Mg2+ are in the range of 1 mM-1. The stoichiometry of the effect of Mg2+ depends on the detergent.     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.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     

Explanation of the pseudohypoaldosteronism (PHA)-stress syndrome with an artificial aldosterone receptor model

A receptor for aldosterone was studied in the cytosol of rectal mucosa of two sisters (M.A., M.B.) with the clinical manifestations of pseudohypoaldosteronism (PHA). Compared to age matched controls the patients showed a decreased affinity for aldosterone (M.A. Kd1: 0.18 nM, Kd2: 4.55 nM; Nmax1: 0.185 fmol/mg cytosol protein (CP), Nmax2: 3.12 fmol/mg CP, respectively). In an attempt to find an explanation for the phenomenon of stress-induced electrolyte imbalance in PHA patients an experimental set up was designed, using aldosterone antibody material as artificial aldosterone receptor. Specific binding was evaluated in addition with and without a 25-100-fold molar excess of dexamethasone (DEX) in order to overcome the glucocorticoid affinity of the aldosterone receptor, a phenomenon proposed to be the cause for the severe consequences of stress in some patients with PHA. The aldosterone antiserum showed two binding sites, similar to the natural receptor (Kd1: 0.15 nM, Kd2: 1.30 nM; Nmax: 30 fmol/mg CP and 130 fmol/mg CP, respectively). Under the influence of DEX the high affinity binding site (Kd1) was occupied by the glucocorticoidanalogon (Kd: 1.30 nM; Nmax: 125 fmol/mg CP). In conclusion, in stress situations, with increased quantities of glucocorticoid circulating, the high affinity binding site of the aldosterone receptor might be occupied by the glucocorticoids, while the low affinity binding site in PHA patients might not have sufficient binding capacity to maintain the electrolyte balance.     

Monitoring the persistence of Laccaria bicolor as an ectomycorrhizal symbiont of nursery-grown Douglas fir by PCR of the rDNA intergenic spacer

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.