scholarly journals STEROID INHIBITION OF PROTEIN INCORPORATION BY ISOLATED AMPHIBIAN OOCYTES

1974 ◽  
Vol 61 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Allen W. Schuetz ◽  
Robin A. Wallace ◽  
James N. Dumont
Keyword(s):  
Rana Pipiens ◽  
Follicle Cells ◽  
Blood Protein ◽  
Short Treatment ◽  
Nuclear Maturation ◽  
Desoxycorticosterone Acetate ◽  
Protein Incorporation ◽  
The Relationship ◽  
Stimulation Of

The relationship between blood protein (vitellogenin) incorporation and nuclear maturation was studied in individual amphibian oocytes after in vitro exposure to desoxycorticosterone acetate (DOCA). Isolated Rana pipiens oocytes were incubated in vitro with radioactively labeled oocyte yolk precursor ([3H]vitellogenin) obtained from estrogenized Xenopus laevis. Incorporation of labeled vitellogenin into the oocytes continued over a 24-h period. Oocytes simultaneously exposed to DOCA and to labeled vitellogenin exhibited both inhibition of vitellogenin incorporation and stimulation of nuclear maturation and cortical changes. Inhibition of vitellogenin incorporation was observed after approximately 9 h of incubation and was correlated with the time of nuclear breakdown. Preincubation of oocytes in steroid for 9 h essentially terminated vitellogenin incorporation. Incorporation of vitellogenin occurred after removal of follicle cells from the oocyte by a short treatment with EDTA. These results demonstrate the macromolecular vitellogenin transport system remains operative in oocytes which can undergo nuclear maturation and that the steroid DOCA can affect its function. Evidence suggests that the mechanism of steroid inhibition is in part the result of inhibition of the micropinocytotic process in the oocyte cortex.

scholarly journals Prediction of maturational competence of feline oocytes using supravital staining of cumulus cells by propidium iodide

Zygote ◽  
2011 ◽  
Vol 20 (4) ◽  
pp. 333-337 ◽  
Author(s):  
Kenzo Uchikura ◽  
Masashi Nagano ◽  
Mitsugu Hishinuma
Keyword(s):  
Propidium Iodide ◽  
Cumulus Cell ◽  
Membrane Integrity ◽  
Cumulus Cells ◽  
Nuclear Maturation ◽  
Non Invasive ◽  
Maturation Rate ◽  
Cell Layers ◽  
The Relationship

SummaryWe examined the relationship between integrity of cumulus cells and nuclear maturation rate after in vitro culture to determine a non-invasive prediction of the maturational competence of feline oocytes. Feline cumulus–oocyte complexes (COCs) were collected from either small (400–800 μm) or large (≥800 μm) follicles. Immediately after collection, cumulus cells were evaluated morphologically (thickness of cumulus cell layers) and stained with propidium iodide (PI), which penetrates only non-viable cells. Cumulus cells without PI staining were judged as having good membrane integrity. After evaluation, COCs were cultured for 30 h and their nuclear maturation rate was determined. The nuclear maturation rate of oocytes derived from large follicles (89.8%) was higher (p < 0.05) than that from small follicles (60.8%). There was no difference in the maturation rate of oocytes from follicles with the same size regardless of cumulus morphology. In contrast, oocytes that had cumulus cells with good membrane integrity showed a higher maturation rate (93.8%) than oocytes with poor cumulus integrity (76.9%) in large follicles (p < 0.05). We conclude that evaluation of membrane integrity of cumulus cells by propidium iodide staining can be used to predict the maturational competence of oocytes.

The effects of acetate and of pyruvate on the pathways of glucose catabolism in lactating mammary tissue. II. Sheep tissue

1969 ◽  
Vol 36 (3) ◽  
pp. 469-478 ◽  
Author(s):  
R. W. Smith ◽  
R. F. Glascock
Keyword(s):  
Pentose Phosphate Pathway ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Mammary Tissue ◽  
Glucose Catabolism ◽  
Glucose Carbon ◽  
Rat Tissue ◽  
The Relationship ◽  
Stimulation Of

SummaryA study was made of the changes in the rates of oxidation of the C(1), C(2) and C(6) atoms of glucose and in the pathways of glucose catabolism in sheep udder tissue in vitro which occurred when acetate and pyruvate were added.Whereas in rat mammary tissue the rate of oxidation of the C(1) atom of glucose was very much greater than that of the C(6) atom, the ratio of the rates of oxidation of these 2 atoms in sheep tissue was less than 2 when glucose was the only substrate.The addition of acetate resulted in an unequal stimulation of the oxidation of these 2 atoms, with the result that the ratio of their rates of oxidation was about doubled. The rate of oxidation of the C(2) atom was also increased.Acetate also increased the participation of the pentose phosphate pathway in glucose catabolism as measured by the incorporation of the C(1) and C(6) atoms of glucose into fatty acids, lactic acid and glycerol.Pyruvate produced little effect on the rate of oxidation of the C(1) atom but somewhat depressed that of the C(6) atom of glucose. At the same time, it caused a large increase in the participation of the pentose phosphate pathway.These results are discussed with reference to re-cycling of glucose carbon in the pentose phosphate pathway and to the relationship between that pathway and fatty acid synthesis. It is noted that the incorporation of glucose carbon into the 3 intermediates used gave values for the participation of that pathway which were in better agreement than was obtained in rat tissue. It is concluded that triose phosphates are more nearly in equilibrium in sheep than in rat mammary tissue.

Involvement of cGMP in LHRH-stimulated gonadotropin release.

1978 ◽  
Vol 235 (6) ◽  
pp. E586 ◽  
Author(s):  
Z Naor ◽  
C P Fawcett ◽  
S M McCann
Keyword(s):  
Mechanism Of Action ◽  
Female Rats ◽  
Male Rats ◽  
Camp Content ◽  
Luteinizing Hormone Releasing Hormone ◽  
Gonadotropin Release ◽  
Male And Female Rats ◽  
The Relationship ◽  
Stimulation Of

Anterior pituitary content of cyclic AMP (cAMP) and cyclic GMP (cGMP) has been measured during stimulation of gonadotropin release by luteinizing-hormone-releasing hormone (LHRH) in vitro to gain more information concerning the relationship between the mechanism of action of LHRH and cyclic nucleotides. During the increased gonadotropin release obtained by incubation by hemipituitaries with LHRH (0.25--25 X 10(-9) M) for 180 min, the glands taken from both male and female rats exhibited increased cGMP content, whereas cAMP content rose only in those taken from male rats. The increase in cGMP content was observed after only 2 min in the presence of LHRH (5 X 10(-9) M) and prior to augmented gonadotropin release. The increase in cAMP content in the male glands was detectable only after 60 min of incubation. These results suggest that cGMP might be involved in the mechanism of action of LHRH.

Cellular mechanisms mediating the stimulation of ovine endometrial secretion of prostaglandin F2α in response to oxytocin: role of phospholipase C and diacylglycerol

1994 ◽  
Vol 141 (3) ◽  
pp. 481-490 ◽  
Author(s):  
W J Silvia ◽  
J-S Lee ◽  
D S Trammell ◽  
S H Hayes ◽  
L L Lowberger ◽  
...  
Keyword(s):  
Time Course ◽  
Prostaglandin F2α ◽  
Endometrial Tissue ◽  
Indole Derivatives ◽  
Cellular Mechanisms ◽  
Response Curves ◽  
The Relationship ◽  
Stimulation Of

Abstract The first objective was to describe and evaluate the relationship between the ability of oxytocin to stimulate the activity of phospholipase (PL) C and its ability to stimulate the release of prostaglandin (PG) F2α in ovine endometrial tissue. Caruncular endometrial tissue was collected from ovariectomized ewes after completion of an 11-day steroid replacement protocol. In experiment 1, explants were incubated either in the presence (10−6 m) or absence of oxytocin for 0, 1, 3, 10, 30 or 100 min to examine the time-course for activation of PLC and release of PGF2α in response to oxytocin. An increase in the activity of PLC was detected at 3 min while an increase in the release of PGF2α was not detected until 10 min (P<0·05). In experiment 2, explants were incubated in the presence of various oxytocin analogues (10−6 m) to compare their abilities to activate PLC and release PGF2α. Oxytocin and three receptor angonists stimulated the activity of PLC and the release of PGF2α (P<0·05) while two oxytocin receptor antagonists had no effect on either response. In experiment 3, explants were incubated in the presence of oxytocin or arginine vasopressin at 10−9 to 10−6 m to establish dose–response curves for the activation of PLC and release of PGF2α. For both hormones, significant increases (P<0·05) in the release of PGF2α were observed at 10−8 m while increases in PLC activity were not detected until 10−7 m was used. In experiment 4, explants were pretreated with either U-73122 (an inhibitor of PLC activity) or U-73343 (an inactive analogue of U-73122). Explants were then treated with control medium, oxytocin or AlF4−. Both oxytocin and AlF4− stimulated the activity of PLC and the release of PGF2α (P<0·05). U-73122 blocked the ability of oxytocin to stimulate the release of PGF2α (P<0·05) but had no effect on its ability to stimulate the activity of PLC (P>0·1). Based on the results from these experiments, the role of PLC in mediating the stimulatory effect of oxytocin on the release of PGF2α remains unclear. The second objective was to evaluate the role of diacylglycerol (DAG) in mediating the stimulatory effect of oxytocin on endometrial secretion of PGF2α. In experiment 5, explants were incubated in vitro with varying doses of two DAG analogues. Both analogues stimulated the release of PGF2α at 10−6 m (P<0·05), the highest dose tested. Corresponding inactive control compounds had no stimulatory effect. In experiment 6, explants were incubated with two synthetic DAGs and two indole-derived analogues of DAG. The indole derivatives stimulated the release of PGF2α. The synthetic DAGs were less effective in stimulating the release of PGF2α at the doses tested. In experiment 7, explants were preincubated with R59022 or LiCl. R59022 enhanced both the basal and oxytocin-stimulated released of PGF2α (P=0·07). LiCl promoted an increase in the accumulation of inositol trisphosphate (P<0·05) but had no effect on the release of PGF2α (P>0·5). These data indicate that DAG stimulates release of PGF2α from ovine endometrial tissue and may mediate the stimulatory effect of oxytocin on release of PGF2α. Journal of Endocrinology (1994) 141, 481–490

scholarly journals Microfilament-mediated surface change in starfish oocytes in response to 1-methyladenine: implications for identifying the pathway and receptor sites for maturation-inducing hormones.

1981 ◽  
Vol 90 (2) ◽  
pp. 362-371 ◽  
Author(s):  
T E Schroeder
Keyword(s):  
Follicle Cell ◽  
Early Response ◽  
Follicle Cells ◽  
Pisaster Ochraceus ◽  
Receptor Sites ◽  
Equivalent Number ◽  
Cell Processes ◽  
First Time ◽  
Stimulation Of

Oocytes of the starfish Pisaster ochraceus exhibit an early response to 1-methyladenine (the maturation-inducing hormone), which is described for the first time. In this response approximately 6,500 spikelike surface projections, much larger than microvilli, emerge transiently from oocytes stripped of their follicle cells and then treated with the hormone in vitro. Each spike contains a prominent bundle of microfilaments, possibly composed of actin. The distribution of spikes when follicle cells are only partially removed and the morphological details of the normal junctional association between follicle cells and oocytes suggest that 1-methyladenine-sensitive sites (receptor sites) can be identified with the approximately 6,500 postjunctional specializations that are part of the oocyte surface. This finding in turn is employed to construct a set of hypotheses concerning the route that 1-methyladenine normally takes from the follicle cells to an oocyte during stimulation of maturation; it is postulated that, for each oocyte, 1-methyladenine is transported along approximately 6,500 thin follicle-cell processes, it is transmitted across the junctional gaps of an equivalent number of junctions between follicle cells and an oocyte, and then interacts with the postjunctional sites where 1-methyladenine receptors are thought to be clustered. Comparative aspects of this mode of intercellular communication are discussed.

L-glutamine with D-glucose stimulates oxidative metabolism and NaCl absorption in piglet jejunum

1992 ◽  
Vol 263 (6) ◽  
pp. G960-G966 ◽  
Author(s):  
J. M. Rhoads ◽  
E. O. Keku ◽  
J. P. Woodard ◽  
S. I. Bangdiwala ◽  
J. G. Lecce ◽  
...  
Keyword(s):  
Oxidative Metabolism ◽  
Carbonic Acid ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Glutamine Metabolism ◽  
Nacl Absorption ◽  
The Relationship ◽  
Stimulation Of

To explore the relationship between intestinal fluid absorption and oxidative metabolism, we measured the effects of amino acids and glucose on piglet jejunal ion transport and oxygen consumption (QO2) in vitro. Jejunal QO2 was stimulated by L-glutamine and D-glucose but not by the nonmetabolizable organic solutes methyl beta-D-glucoside or L-phenylalanine. QO2 was maximally enhanced by the combination of D-glucose and L-glutamine (5 mM). Even though 5 mM L-glutamine was previously found to be insufficient to stimulate NaCl absorption, 5 mM L-glutamine enhanced jejunal NaCl flux when combined with equimolar mucosal D-glucose. Either D-glucose or methyl beta-D-glucoside caused an increase in short-circuit current (Isc), an increase in Na+ absorption in excess of Isc, and a decrease in Cl- secretion, when L-glutamine was substituted for D-glucose (10 mM) on the serosal side. This relationship suggests that mucosal sugars, if combined with L-glutamine, enhance neutral NaCl absorption as well as electrogenic Na+ flow. (Aminooxy)acetate, an inhibitor of alanine aminotransferase, abolished the stimulation of QO2 and the NaCl-absorptive response to L-glutamine. We conclude that the oxidative metabolism fueled by L-glutamine is linked to a NaCl-absorptive mechanism in the intestine. We propose that the CO2 produced by glutamine metabolism yields carbonic acid, which dissociates to H+ and HCO3-, which may stimulate parallel antiports in the apical membrane.

Cumulus cell features and nuclear chromatin configuration of in vitro matured canine COCs and the influence of in vivo serum progesterone concentrations of ovary donors

Zygote ◽  
2009 ◽  
Vol 17 (1) ◽  
pp. 79-91 ◽  
Author(s):  
B. A. Rodrigues ◽  
A. E. F. Silva ◽  
P. Rodriguez ◽  
L. F. Cavalcante ◽  
J. L. Rodrigues
Keyword(s):  
Cumulus Cell ◽  
Nuclear Chromatin ◽  
Serum Progesterone ◽  
Nuclear Maturation ◽  
Cumulus Oocyte Complex ◽  
Chromatin Configuration ◽  
The Relationship

SummaryPhenotype integrity is viewed as an indicator of cumulus–oocyte complex (COC) viability. The objectives of this study were: (a) to observe the influence of cumulus investment expansion on the nuclear chromatin configuration of canine oocytes matured in vitro; (b) to examine the relationship between cumulus cell (CC) expansion and its morphology after in vitro maturation (IVM); (c) to ascertain the influence of in vivo serum progesterone (SP) concentrations of ovary donors on oocyte nuclear maturation, CC phenotypes and degrees of CC expansion of in vitro matured COCs. After 48 h of IVM in modified TCM 199, CCs from grade 1 and 2 COCs were stained with propidium iodide. Oocyte chromatin configuration was visualized by Hoechst 33342 stain. Results showed that oocyte IVM was not influenced by degree of CC expansion (D1, D2 and D3) in COCs. From the CC types (C1, C2 and C3), number of C1 types was higher at D1 expansion and differed from those observed at D2 and D3 expansions. Additionally, rates of apoptosis in D1 CCs were lower than those observed in D2 CCs (p < 0.05). Oocyte nuclear maturation was not influenced by in vivo SP concentrations of ovary donors. On the other hand, D3 expansion prevailed in COCs from bitches at SP > 2.5 ng/ml (p < 0.001). Moreover, in vitro CC apoptosis was associated both with low (0–1 ng/ml) and with high (>5 ng/ml) in vivo SP levels. These findings indicate that morphology of CCs from in vitro matured dog oocytes gives valuable information on viability of COCs and could possibly be used as a parameter in predicting the quality of oocytes destined for in vitro fertilization (IVF) and their outcomes.

scholarly journals Ileal pH and apparent absorption of magnesium in rats fed on diets containing either lactose or lactulose

1993 ◽  
Vol 70 (3) ◽  
pp. 747-756 ◽  
Author(s):  
Astrid M. P. Heijnen ◽  
Elizabeth J. Brink ◽  
Arnoldina G. Lemmens ◽  
Anton C. Beynen
Keyword(s):  
Apparent Absorption ◽  
Enhanced Absorption ◽  
The Relationship ◽  
Negative Relationships ◽  
Stimulation Of

The hypothesis was tested that dietary lactose v. glucose stimulates Mg absorption in rats because lactose lowers pH of the ileal lumen, which improves Mg solubility which in turn enhances Mg availability for transport across the ileal epithelium. For comparison, the effects of lactulose were studied because it shares with lactose the characteristic of being poorly digestible. Replacement of glucose by lactose (100 g/Kg) significantly stimulated apparent absorption of Mg. Apart from Mg absorption, lactulose also significantly enhanced absorption of Ca and phosphate. Lactose v. glucose lowered the pH of the ileal lumen from 7·5 to 7·2, whereas lactulose significantly reduced it to 7·0. In in vitro incubations a decrease in pH within the range of fluctuation in vivo was found to cause an improved solubility of Mg, and to a lesser extent also of Ca and phosphate. The smaller fall of ileal pH induced by feeding lactose instead of lactulose may explain why lactose improved Mg absorption only. For all individual rats combined there were negative relationships between ileal pH and apparent absorption of minerals, the relationship being strongest for Mg. Neither lactose nor lactulose was found to raise ileal solubility of minerals, which could relate to the possibility that the time of sampling was not appropriate. It is suggested that lactose-induced stimulation of Mg absorption in rats is caused by a lowering of ileal pH.

scholarly journals THE COMPARATIVE BEHAVIOR OF MAMMALIAN EGGS IN VIVO AND IN VITRO

1935 ◽  
Vol 62 (5) ◽  
pp. 665-675 ◽  
Author(s):  
Gregory Pincus ◽  
E. V. Enzmann
Keyword(s):  
Polar Body ◽  
Pituitary Hormones ◽  
Follicle Cells ◽  
Nuclear Maturation ◽  
Sequence Of Events ◽  
First Polar Body ◽  
Chronological Sequence ◽  
Mammalian Eggs

1. A definite chronological sequence of events occurs in the eggs and follicles of rabbits after mating or after the injection of ovulation-inducing substances. The follicle secretes secondary liquor folliculi, and there occurs a separation of the corona radiata from strands connecting it to the follicle cells. The ovum goes through nuclear maturation with as climax the production of the first polar body by the 8th hour after copulation. 2. Thyroxin injections cause indirectly the same effects as mating or pituitary injections but no ovulation occurs. The thyroxin effect occurs later than the pituitary effect and is due to an initiation of atresia in the follicles. 3. Explantation of ova results in typical maturation phenomena which are apparently unaffected by the presence of pituitary hormones or of thyroxin in the culture medium. 4. It is concluded that maturation of the ovum can be obtained simply by isolating it from the normal follicular environment. 5. Normal fertilization can be secured with eggs removed from the follicles.

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