Acid release at meiotic maturation of oocytes in the polychaete annelidSabellaria alveolata

Summary About 1 pmole of acid per egg is released when prophasic oocytes undergo maturation under the action of sperm, proteases or ionophore A 23187. No similar acid release occurs at fertilization of matured oocytes. These findings are compared with data onUrechis and sea urchin.     

Role of calcium in the reinitiation of oocyte meiosis in Sabellaria alveolata (L.) (Annelida, Polychaeta)]

Meiotic maturation is triggered by ionophores A 23187 and X 537 A, even in absence of extracellular calcium. CaMg free medium alone initiates 100% maturations while Ca free SW triggers varying percentages of maturation and Mg free SW has no effect.     

Allantoinase in the marine polychaete Eudistylia vancouveri.

Allantoinase, an enzyme in the purine-urea cycle, was found in Eudistylia vancouveri (Polychaeta). The enzyme had a pH optimum at 7.6. The Km was 0.012 M allantoin, and the Arrhenius energy of activation was 12.6 to 14.6 kcal/mol.     

Genetic activity of mouse oocytes during in vitro "spontaneous" maturation]

Mouse oocytes, liberated from ovarian follicles, resume meiosis in the obligatory presence of Ca++. PHMPS exerts a toxic effect on this mechanism. m-RNA synthesis, in contrast to that of r-RNA. seems to be required during the first hours of maturation in order to ensure realization of the following steps: in addition the 2nd maturation period, corresponding to the first polar body extrusion, depends on the presence of proteins synthesized during the chromatin condensation process and germinal vesicle breakdown. We suggest that it might be a factor responsible for microtubule formation in metaphase I.     

Effect of adrenotropic substances on the growth and maturation of oocytes of the sea urchinStrongylocentrotus nudus

Summary Growth and maturation of oocytes in sea urchins is inhibited under the influence of catecholamines. A monoaminergic system is assumed to participate in the regulation of oogenesis.     

Isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus Rana): changes during oocyte maturation

Rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly and disassembly dynamics of frog oocyte tubulin compared to that in brain. By using centrifugation, SDS-PAGE, two-dimensional gel electrophoresis and Western blots, probed with anti-α-tubulin monoclonal antibodies, polymorphic α-tubulins (isoforms) were compared in brains and follicle-enclosed oocytes of northern (Rana pipiens) and southern (R. berlandieri) frogs. Oocyte tubulin in both species had isoforms with greater ranges of isoelectric point (pI) than those of brain tubulins; in particular, the oocyte tubulin pIs ranged further into the acidic region of the isoelectric-focusing gels than corresponding brain tubulin. This difference may, in part, be responsible for the previously reported assembly differences between oocyte tubulin (undetectable assembly) and brain tubulin (high assembly). Isoforms of α-tubulin with relat ively acidic pI were more abundant in northern frog brain and oocyte soluble extracts than in analogous extracts from southern frogs. Furthermore, additional acidic α-tubulin isoforms were found in progesterone-treated oocytes (i.e., eggs), indicating increased heterogeneity of acidic a-tubulin isoforms during oocyte meiotic maturation. Among northern frog oocyte soluble components fractionated on Superose-6b columns, tubulin complexes with apparent molecular mass of about 1800 kDa were found to contain acidic α-tubulin isoforms while the putative oligomeric tubulins with an apparent molecular mass of about 250 kDa contained an additional relatively basic α-tubulin isoform. The acidic α-tubulin isoforms, therefore, are proposed to be associated with cold-adaptable cells of brain and oocytes, and may also be involved in stabilization of large soluble tubulin complexes in oocytes of the northern frog. Received 1 October 2002; accepted 9 October 2002 RID="*" ID="*"Corresponding author.     

Oocyte maturation in vitro: contribution of the oviduct to total maturation in Xenopus laevis.

Contact of progesterone matured oocytes of Xenopus laevis with the oviduct reduces the time necessary to attain cleavage capacity from 24 h to 3 h. Full maturity has been demonstrated by normal development of the matured eggs after fertilization.     

Quantitative determination of acetylcholinesterase activity in individual megakaryocytes at various stages of maturation

Zusammenfassung Die Aktivität der Azetylcholinesterase von einzelnen Megakaryozyten verschiedener Reifegrade wurde mit Hilfe des Cartesischen Tauchers bestimmt. Die Megakaryozyten zeigen auf dem Megakaryoblasten- und Promegakaryozytenstadium grosse Unterschiede der Azetylcholinesteraseaktivität. In der letzten Phase der Reifung, wenn die Zellen einen Durchmesser von 45 µ erreichen, wird das Ferment am stärksten wirksam.     

Age factor in the maturation of collagen. Intramolecular linkages in mildly denatured collagen

Zusammenfassung In den Extrakten von Schwanzsehnen der Ratten (30 min in Natriumacetatpuffer, pH 4,5, auf +40°C erwärmt) vermehren sich mit zunehmendem Alter die elektrophoretisch getrennten-Komponenten auf Kosten der -Komponenten.

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This work has been aided by institutional grants from Sigrid Jusélius Foundation and U.S. Department of Agriculture, Foreign Research and Technical Programs Division.     

Oocyte maturation in vitro: Contribution of the oviduct to total maturation inXenopus laevis

Summary Contact of progesterone matured oocytes ofXenopus laevis with the oviduct reduces the time necessary to attain cleavage capacity from 24 h to 3 h. Full maturity has been demonstrated by normal development of the matured eggs after fertilization.