Mammalian AT2 Receptors Expressed in Xenopus laevis Oocytes Couple to Endogenous Chloride Channels and Stimulate Germinal Vesicle Break Down

2009 ◽  
Vol 24 (1-2) ◽  
pp. 45-52 ◽  
Author(s):  
Rosalina Reyes ◽  
Lakshimdevi Pulakat ◽  
Ricardo Miledi ◽  
Ataúlfo Martínez-Torres
Keyword(s):  
Xenopus Laevis ◽  
Chloride Channels ◽  
Germinal Vesicle ◽  
Germinal Vesicle Break Down ◽  
At2 Receptors

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).

scholarly journals Effect of Adding Insulin Transferrin Selenium (ITS) in the Medium on Maturation and Fertilization Rates of Bali Cattle Oocytes

2019 ◽  
Vol 24 (3) ◽  
pp. 95
Author(s):  
Hikmayani Iskandar ◽  
H Sonjaya ◽  
M Yusuf
Keyword(s):  
Germinal Vesicle ◽  
Fertilization Rate ◽  
Fertilization Rates ◽  
Randomized Design ◽  
Maturation Rate ◽  
Bali Cattle ◽  
Germinal Vesicle Break Down ◽  
Metaphase I

The aim of this study was to determine the effect of adding Insulin Transferrin Selenium (ITS) in the medium on maturation and fertilization rates of Bali cattle oocytes. The ovarium of Bali cows were sliced to produce oocytes, then the collected oocytes were subsequently selected based on their quality. Those oocytes were maturated for 24 hours and then fertilized for 18 hours in the incubators of 5% CO2 with temperature of 38.5ºC. Oocytes were stained using 2% of aceto orcein, and observed under a microscope. This study was divided into four treatments at different addition of ITS in the medium and replicated four times, and analized using a Factorial Complete Randomized Design (CRD)at each treatment. The treatments consisted of P0 as control, P1 (5 ng/ml), P2 (10 ng/ml), and P3 (15 ng/ml). Parameters observed in this study were the stages of oocytes maturation rate that consisted of germinal vesicle (GV), germinal vesicle break down (GVBD), metaphase I (M-I), and metaphase II (M-II), and fertilization rate that consisted of absence of pronucleus (P0), 1 pronucleus (PN1), 2 pronucleus (PN2), and more than two pronucleus (>2PN). The results of this study showed that addition of ITS at 5-15 ng/ml did not effect maturation and fertilization rates of Bali cows oocytes.The conculision of the study is addition of ITS at 5 ng / ml produces the best level of maturation and for the best level of fertilization with addition ITS at 15 ng / ml.

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.

scholarly journals Effects of Epidermal Growth Factor and Myo-Inositol on Nuclear Configuration and Subsequent Embryonic Development of Sheep Oocytes

2021 ◽  
Vol 9 (12) ◽  
pp. 2147-2152
Author(s):  
Omar Mardenli ◽  
Hadi Awad Hassooni ◽  
Mahdi Saleh Mohammad Alkerwi
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Culture Media ◽  
Calf Serum ◽  
Germinal Vesicle ◽  
Cellular Level ◽  
Biological Interactions ◽  
Epidermal Growth ◽  
Germinal Vesicle Break Down ◽  
Metaphase I

Growth factors and vitamin-like substances have great positive importance in most biological interactions in the cellular level. The addition of these elements in the culture media will increase the yield of the resulting embryos and improve quality. We examined the effects of epidermal growth factor (EGF) and myo-inositol (MI) on meiotic maturation and yields of blastocyst of Awassi sheep oocyte across two experiments. The oocytes obtained were subjected into three treatments: A (without EGF nor MI), B (10 ng/ml EGF + 20 mmol/l MI) and C (50 ng/ml EGF +40 mmol/l MI). Oocytes were then cultured in Ham's F-10 medium supplemented with 5% (v: v) fetal calf serum and 40 ng/ml follicle - stimulating hormone. In the first experiment, during the 27-h culture period, the oocytes were assessed for germinal vesicle break down, metaphase-I and metaphase-II stages across three-time intervals (9, 21 and 27-h). Results of the experiment showed that EGF and MI enhanced the rates of germinal vesicle break down phase (1.53%; 27-h interval; lowest value), metaphase-I (33.87%; 21-h interval) and metaphase-II (89.23%; 27-h interval). In the second experiment, the oocytes incubated in treatment B achieved the highest rates of cleavage (81.96%), 2-8 cell (62.35%) and blastocyst (45.09%). It is concluded from the present study that incubating sheep oocytes in culture media containing a cocktail of EGF (10 ng/ml) and MI (20 mmol/l) significantly improves the rates of metaphase-II, fertilization and blastocyst rates.

Expression of the c-myc proto-oncogene during development of Xenopus laevis

1986 ◽  
Vol 6 (12) ◽  
pp. 4499-4508
Author(s):  
M W King ◽  
J M Roberts ◽  
R N Eisenman
Keyword(s):  
Xenopus Laevis ◽  
Transcriptional Activation ◽  
Somatic Cells ◽  
Germinal Vesicle ◽  
Significant Decline ◽  
Cdna Clones ◽  
Nuclear Fraction ◽  
Early Cleavage ◽  
Cleavage Stages ◽  
Neurula Stage

We isolated and characterized Xenopus laevis c-myc cDNAs from an oocyte-specific library. These cDNA clones encompass 2.35 kilobases of the X. laevis c-myc RNA and contain the entire coding domain of 1,257 nucleotides of the 419-amino acid-long X. laevis c-myc protein. The 2.7-kilobase X. laevis c-myc mRNA is expressed in the oocyte, maintained in the egg, and is present throughout the early cleavage stages of embryogenesis. At the time of transcriptional activation in the embryo the c-myc RNA levels show a significant decline and then reaccumulate continuously throughout the remainder of premorphogenic development. At the early neurula stage of embryogenesis the pattern of c-myc RNA expression is elevated in the mesoderm with respect to the endoderm and ectoderm. In the adult X. laevis the c-myc mRNA is expressed in some (e.g., skin, muscle) but not all differentiated tissues. The X. laevis c-myc protein migrates as a doublet of 61,000- and 64,000-dalton species. Both species are phosphorylated in oocytes and somatic cells, exhibit extremely short half-lives of less than 30 min, and are localized to the nuclear fraction of somatic cells. By contrast, the oocyte protein shows both cytoplasmic and germinal vesicle distribution and appears to be stable.

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