scholarly journals Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs.

1984 ◽  
Vol 98 (4) ◽  
pp. 1247-1255 ◽  
Author(s):  
J Gerhart ◽  
M Wu ◽  
M Kirschner
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Germinal Vesicle ◽  
Small Scale ◽  
Xenopus Laevis Oocytes ◽  
Germinal Vesicle Breakdown ◽  
Cytoplasmic Factor ◽  
M Phase ◽  
Cytostatic Factor ◽  
Meiotic Cycle

We have examined the regulation of maturation-promoting factor (MPF) activity in the mitotic and meiotic cell cycles of Xenopus laevis eggs and oocytes. To this end, we developed a method for the small scale extraction of eggs and oocytes and measured MPF activity in extracts by a dilution end point assay. We find that in oocytes, MPF activity appears before germinal vesicle breakdown and then disappears rapidly at the end of the first meiotic cycle. In the second meiotic cycle, MPF reappears before second metaphase, when maturation arrests. Thus, MPF cycling coincides with the abbreviated cycles of meiosis. When oocytes are induced to mature by low levels of injected MPF, cycloheximide does not prevent the appearance of MPF at high levels in the first cycle. This amplification indicates that an MPF precursor is present in the oocyte and activated by posttranslational means, triggered by the low level of injected MPF. Furthermore, MPF disappears approximately on time in such oocytes, indicating that the agent for MPF inactivation is also activated by posttranslational means. However, in the absence of protein synthesis, MPF never reappears in the second meiotic cycle. Upon fertilization or artificial activation of normal eggs, MPF disappears from the cytoplasm within 8 min. For a period thereafter, the inactivating agent remains able to destroy large amounts of MPF injected into the egg. It loses activity just as endogenous MPF appears at prophase of the first mitotic cycle. The repeated reciprocal cycling of MPF and the inactivating agent during cleavage stages is unaffected by colchicine and nocodazole and therefore does not require the effective completion of spindle formation, mitosis, or cytokinesis. However, MPF appearance is blocked by cycloheximide applied before mitosis; and MPF disappearance is blocked by cytostatic factor. In all these respects, MPF and the inactivating agent seem to be tightly linked to, and perhaps participate in, the cell cycle oscillator previously described for cleaving eggs of Xenopus laevis (Hara, K., P. Tydeman, and M. Kirschner, 1980, Proc. Natl. Acad. Sci. USA, 77:462-466).

Diacylglycerol production in Xenopus laevis oocytes after microinjection of p21ras proteins is a consequence of activation of phosphatidylcholine metabolism

1990 ◽  
Vol 10 (1) ◽  
pp. 333-340
Author(s):  
J C Lacal
Keyword(s):  
Xenopus Laevis ◽  
Inositol Phosphates ◽  
Biological Response ◽  
Germinal Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Ras Proteins ◽  
Germinal Vesicle Breakdown ◽  
Second Peak ◽  
Synthesis And Degradation ◽  
Phosphatidylcholine Metabolism

Microinjection of p21Ha-ras proteins into Xenopus laevis oocytes induces a rapid increase of 1,2-diacylglycerol (DAG) levels. The observed alterations in DAG levels were consistent with the ability of the protein to induce maturation, measured by germinal vesicle breakdown (GVBD). Both the increase in DAG levels and GVBD activity were dependent on the ability of the proteins to undergo membrane translocation. Alterations of DAG levels or GVBD activity did not correlate with changes in the levels of inositol phosphates. However, at minimal doses sufficient to achieve maximal biological response, a biphasic increase in the amounts of phosphocholine and CDP-choline was observed. The first burst of phosphocholine and CDP-choline preceded the increase in DAG levels. The second peak paralleled the appearance of DAG. Choline kinase activity was also increased in oocyte extracts after p21ras microinjection. These results suggest that both the synthesis and degradation of phosphatidylcholine are activated after microinjection of ras proteins into Xenopus oocytes, resulting in a net production of DAG.

Lysophosphatidic acid induces a pertussis toxin-sensitive Ca(2+)-activated Cl- current in Xenopus laevis oocytes

1992 ◽  
Vol 263 (4) ◽  
pp. C896-C900 ◽  
Author(s):  
M. E. Durieux ◽  
M. N. Salafranca ◽  
K. R. Lynch ◽  
J. R. Moorman
Keyword(s):  
Xenopus Laevis ◽  
Pertussis Toxin ◽  
Lysophosphatidic Acid ◽  
Reversal Potential ◽  
Germinal Vesicle ◽  
Membrane Receptor ◽  
Xenopus Laevis Oocytes ◽  
Germinal Vesicle Breakdown ◽  
Specific Membrane ◽  
Specific Membrane Receptor

Lysophosphatidic acid (LPA) induces a Ca(2+)-activated Cl- current in defolliculated Xenopus laevis oocytes. The response appears mediated by a specific membrane receptor, because no current is induced when related compounds [phosphatidic acid (PA), lysophosphatidylcholine (LPC), and lysophosphatidylserine (LPS)] are applied extracellularly or when LPA is injected intracellularly. Incubation in pertussis toxin prevents the response. The response is mediated by a Ca(2+)-activated Cl- current because 1) it is abolished by intracellular ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA; 5 mM) but not affected by changes in extracellular Ca2+ concentration and 2) the reversal potential becomes more positive at lower Cl- concentrations. Suramin (2 mM) blocks the LPA-induced current, but PA, LPS, LPC, and the platelet-activating factor antagonist WEB-2086 do not. The response is dose dependent for LPA concentrations from 10(-8) to 10(-3) M. Incubation of oocytes in LPA does not induce germinal vesicle breakdown. These findings suggest that this novel oocyte response to LPA is mediated by a specific membrane receptor linked to a pertussis toxin-sensitive G protein.

Induction of germinal vesicle breakdown in Xenopus laevis oocytes: synergistic action of progesterone and insulin

1984 ◽  
Vol 101 (1) ◽  
pp. 7-12 ◽  
Author(s):  
C. Le Goascogne ◽  
S. Hirai ◽  
E.-E. Baulieu
Keyword(s):  
Xenopus Laevis ◽  
Physiological Role ◽  
Germinal Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Germinal Vesicle Breakdown ◽  
Low Sensitivity ◽  
Dose Dependent ◽  
Subthreshold Level ◽  
Insulin Like Growth Factors

ABSTRACT Progesterone is the hormone that reinitiates the meiotic division of amphibian oocytes and insulin and insulin-like growth factors are also active on defolliculated oocytes in vitro. We have studied Xenopus laevis oocytes (stage 5–6) of different hormonal sensitivities, obtained from unstimulated and from human chorionic gonadotrophin-stimulated females. Some oocytes from unstimulated females were also precultured with a subthreshold level of progesterone. A dose-dependent potentiating effect of the action of progesterone was observed with insulin, and this was particularly remarkable in low-sensitivity oocytes. Since in the presence of insulin, the optimally effective concentration of progesterone was much reduced (as an example from 1 μmol/l to 50 nmol/l), it is suggested that an insulin-like growth factor may play a physiological role in the reinitiation of meiosis in ovaries. J. Endocr. (1984) 101, 7–12

scholarly journals Diacylglycerol production in Xenopus laevis oocytes after microinjection of p21ras proteins is a consequence of activation of phosphatidylcholine metabolism.

1990 ◽  
Vol 10 (1) ◽  
pp. 333-340 ◽  
Author(s):  
J C Lacal
Keyword(s):  
Xenopus Laevis ◽  
Inositol Phosphates ◽  
Biological Response ◽  
Germinal Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Ras Proteins ◽  
Germinal Vesicle Breakdown ◽  
Second Peak ◽  
Synthesis And Degradation ◽  
Phosphatidylcholine Metabolism

Microinjection of p21Ha-ras proteins into Xenopus laevis oocytes induces a rapid increase of 1,2-diacylglycerol (DAG) levels. The observed alterations in DAG levels were consistent with the ability of the protein to induce maturation, measured by germinal vesicle breakdown (GVBD). Both the increase in DAG levels and GVBD activity were dependent on the ability of the proteins to undergo membrane translocation. Alterations of DAG levels or GVBD activity did not correlate with changes in the levels of inositol phosphates. However, at minimal doses sufficient to achieve maximal biological response, a biphasic increase in the amounts of phosphocholine and CDP-choline was observed. The first burst of phosphocholine and CDP-choline preceded the increase in DAG levels. The second peak paralleled the appearance of DAG. Choline kinase activity was also increased in oocyte extracts after p21ras microinjection. These results suggest that both the synthesis and degradation of phosphatidylcholine are activated after microinjection of ras proteins into Xenopus oocytes, resulting in a net production of DAG.

Environmental (anti-)androgenic chemicals affect germinal vesicle breakdown (GVBD) of Xenopus laevis oocytes in vitro

2014 ◽  
Vol 28 (3) ◽  
pp. 426-431 ◽  
Author(s):  
Shan Cao ◽  
Wei Xu ◽  
Qin-Qin Lou ◽  
Yin-Feng Zhang ◽  
Ya-Xian Zhao ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Germinal Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Germinal Vesicle Breakdown

scholarly journals Antibodies to the ras gene product inhibit adenylate cyclase and accelerate progesterone-induced cell division in Xenopus laevis oocytes.

1986 ◽  
Vol 6 (2) ◽  
pp. 719-722 ◽  
Author(s):  
S E Sadler ◽  
A L Schechter ◽  
C J Tabin ◽  
J L Maller
Keyword(s):  
Adenylate Cyclase ◽  
Xenopus Laevis ◽  
Gene Product ◽  
Germinal Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Dependent Manner ◽  
Ras Gene ◽  
Concentration Dependent Manner ◽  
Germinal Vesicle Breakdown

Microinjection of monoclonal antibodies (lines 238, 172, and 259) directed against the ras gene product, p21, into Xenopus laevis oocytes accelerated progesterone-induced germinal vesicle breakdown. Antibody 238 had the greatest effect on the acceleration of progesterone-induced oocyte maturation, and this effect was correlated with in vitro inhibition of adenylate cyclase (EC 4.6.1.1) activity in a concentration-dependent manner. Inhibition of adenylate cyclase by antibody 238 was also measured in membranes prepared from oocytes pretreated with either cholera toxin or pertussis toxin. These results suggest a role for the ras gene product in the regulation of vertebrate cell adenylate cyclase activity.

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