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S J Atlas

Publications and source records attributed to S J Atlas.

53 records · Page 3Linked to original sources
PubMed1988

Progesterone secretion by corpora lutea of the isolated perfused rabbit ovary during pseudopregnancy.

An ovarian in vitro perfusion method was adapted to examine rabbit corpus luteum (CL) function during pseudopregnancy. Ovaries were perfused in vitro with tissue culture Medium 199 with or without 3% bovine serum albumin (BSA). Samples were obtained from both arterial and venous cannulae, allowing rates of progesterone secretion to be determined. Two perfusion methods were compared: a closed system in which perfusion medium continuously recirculated through the tissue, and an open system in which the ovarian vein cannula was left outside the perfusion chamber. The addition of 3% BSA was found to prevent edema and distortion of the interstitial space, and to result in increased progesterone secretion. With the closed perfusion system, the progesterone secretion rate measured over the 6-h perfusion was significantly higher on Day 11 than on Day 1 of pseudopregnancy and had declined significantly on Day 18. There was no difference in secretion rates whether the perfusion system was open or closed, and the results obtained with both systems closely approximated in vivo progesterone secretion rates. Measurements of CL tissue progesterone content before and after in vitro perfusion indicated that the changes in progesterone secretion seen during pseudopregnancy resulted from differences in the synthesis and secretion of progesterone and not from leakage of progesterone already present in the CL prior to perfusion. Taken together, these results indicate that the modified in vitro perfused rabbit ovary preparation described herein is an appropriate model to examine progesterone secretion by ovaries bearing CL.

Animals↗
PubMed1988

The effects of bradykinin on ovulation and prostaglandin production by the perfused rabbit ovary.

Involvement of the vasoactive peptide bradykinin (BK) in ovulation, oocyte maturation, and prostaglandin (PG) production was assessed using an in vitro perfused rabbit ovary preparation. In the first experiment, BK at a concentration of 0.033, 0.33, or 3.3 micrograms/ml was added to the perfusate of one ovary at hourly intervals for the first 10 h of perfusion. The contralateral control ovary was treated with medium alone parallel to the experimental ovary. Ovaries were perfused for a total of 12 h. BK induced ovulation in the absence of gonadotropin in a dose-related fashion, but did not induce maturation of ovulated ova or follicular oocytes. BK significantly stimulated PG production at all concentrations tested, but the effect was not dose related. Prostacyclin, as reflected by the concentration of 6-keto-PGF1 alpha in the perfusate, was the major PG produced. Smaller quantities of PGE2 and PGF2 alpha were present in the perfusate. After a single injection of BK (3.3 micrograms/ml), 6-keto-PGF1 alpha and PGF2 alpha production increased within 15 min and reached a maximum at 60-90 min. PGE2 did not change significantly over this time period. The addition of 1 microgram/ml indomethacin to the perfusate completely inhibited BK-stimulated PG production. However, indomethacin did not significantly affect the ovulatory efficiency of BK-treated ovaries. Neither BK nor indomethacin induced any degenerative changes in ovulated ova or follicular oocytes. The addition of a BK antagonist at 1 microgram/ml every 30 min to the perfusate resulted in an effective blockade of hCG-induced ovulation. These results suggest that BK is involved in the process of follicle rupture, but BK may induce ovulation by a mechanism(s) other than through PG stimulation.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Detection of early pregnancy factor (EPF) using the rabbit ovary and oviduct perfused in vitro.

Two peaks of rabbit serum EPF activity were seen over the course of pregnancy. Rabbit ovaries with or without attached oviducts were perfused in vitro for 5 h beginning 12, 16, 24, 48, 72 and 120 h after mating. Perfused isolated ovaries did not produce EPF in vitro, but significant EPF activity was detected in the perfusate of the ovary together with oviduct. Pseudopregnant animals and those rabbits that did not ovulate exhibited no perfusate EPF activity. Perfusate EPF activity was highest at the time embryos were at the pronuclear stage and continued through the morula stage. Although the location of embryos at 72 h after mating varied between oviduct and uterus, EPF activity was maintained over the perfusion period. The results suggest that EPF release occurs within 3 h of fertilization and that the presence of the preblastocyst embryo is crucial for EPF release.

Animals↗
PubMed1988

Effect of the exposure of intrafollicular oocytes to clomiphene citrate on pregnancy outcome in the rabbit.

This study was designed to determine if exposure of rabbit intrafollicular oocytes to clomiphene citrate (CC) affects pregnancy outcome after in vitro ovulation, in vitro fertilization (IVF), and embryo transfer (ET). Ovaries were perfused in the presence or absence of CC (10(-5) M) and estradiol (E2, 100 ng/ml). Human chorionic gonadotropin (hCG, 50 IU) was added to the perfusate of all ovaries. In vitro ovulated ova were retrieved, inseminated, and transferred to host rabbits. Neither CC nor CC + E2 significantly affected hCG-induced ovulation or fertilization. CC significantly reduced (P less than 0.025) percentage of ovulated ova resulting in offspring. Addition of E2 significantly (P less than 0.05) reversed the reduction in offspring associated with CC alone. These results may be due to the antiestrogenic effects of CC on the intrafollicular oocyte, which compromises postfertilization development.

Animals↗
PubMed1987

The effects of proteolytic enzymes on in vitro ovulation in the rabbit.

The involvement of proteolytic enzymes in follicle rupture was assessed by use of the in vitro perfused rabbit ovary. Streptokinase (10 and 100 units/ml) induced ovulation in the absence of gonadotropin. Ovulation failed to occur in contralateral control ovaries. The time of ovulation in streptokinase- and human chorionic gonadotropin--treated ovaries was similar, but significantly more ova from streptokinase-treated ovaries were immature (p less than 0.001). Other ovaries were pretreated with trans-4-(aminomethyl)-cyclohexane-carboxylic acid, an inhibitor of the conversion of plasminogen to plasmin, and then perfused with human chorionic gonadotropin (50 IU). Ovulatory efficiency was significantly reduced by trans-4-(aminomethyl)-cyclohexane-carboxylic acid at 10 or 1 mmol/L (p less than 0.001), but ovum maturity was unaffected. Aprotinin (100 or 10 micrograms/ml), a potent inhibitor of plasmin, significantly inhibited human chorionic gonadotropin-induced ovulation (p less than 0.001) but did not affect oocyte maturation. Scanning electron microscopy of detergent-treated streptokinase-perfused ovaries revealed loosening and decomposition of collagen in the tunica albuginea. These results suggest proteolytic enzyme involvement in follicle rupture.

Animals↗
PubMed1987

Are ovarian steroids required for ovum maturation and fertilization? Effects of cyanoketone on the in vitro perfused rabbit ovary.

An isolated perfused rabbit ovary preparation was used to determine the effects of cyanoketone, a potent inhibitor of 3 beta-hydroxysteroid dehydrogenase, on ovulation, ovum maturation and fertilizability, and steroid production. In the first experiment, cyanoketone (10(-4) M) was added to the perfusate of one ovary. The contralateral control ovary was perfused with medium alone. Thirty minutes after the onset of perfusion, hCG (50 IU) was added to the perfusate of both ovaries. The ovulatory efficiency of ovaries treated with cyanoketone plus hCG (82.3 +/- 4.6%) was similar to that of ovaries treated with hCG alone (84.8 +/- 4.4%). No difference was observed in the degree of ovum maturity or degeneration between control and cyanoketone-treated ovaries. Progesterone and estradiol production were significantly reduced by cyanoketone treatment; concentrations in the perfusate of ovaries treated with cyanoketone were 9.7% and 8.0% of the control values, respectively, 2 h after exposure to hCG. The concentration of 17-hydroxypregnenolone was not affected by cyanoketone treatment. Exposure to cyanoketone resulted in a significant (P less than 0.005) reduction in the fertilizability of ova ovulated and fertilized in vitro. In the second experiment, the percentage of ova that showed evidence of normal fertilization was significantly (P less than 0.025) increased in ovaries perfused with cyanoketone plus estradiol (64.5%) compared to that in ovaries perfused with cyanoketone alone (32.4%). In the third experiment, the addition of progesterone to the perfusate did not affect fertilizability of ovulated ova in ovaries perfused with cyanoketone plus estradiol. These results suggest that the presence of estradiol in the ovarian steroid environment may be essential for fertilizability of ova, but not for the processes of ovulation or meiotic maturation.

3-Hydroxysteroid Dehydrogenases↗
PubMed1987

The effect of a carbon dioxide pneumoperitoneum on rabbit follicular oocytes and early embryonic development.

The effect of a carbon dioxide (CO2) pneumoperitoneum and its duration on rabbit follicular oocytes was assessed by evaluating fertilization and subsequent embryonic development rates. CO2 may cross the plasma membrane and form carbonic acid, which liberates H+, thus lowering the intracellular pH. There were no significant differences in arterial pH and [HCO3-] between CO2 and air treatment groups, whereas arterial pCO2 and pO2 were significantly increased in the CO2 treatment group. We found that the duration of pneumoperitoneum, irrespective of type of gas used, was negatively correlated with success of embryonic development. These findings necessitate that more attention be given to the gas used for creation of a pneumoperitoneum during egg retrieval for in vitro fertilization and an attempt be made to minimize duration of the pneumoperitoneum.

Animals↗
PubMed1987

Estradiol reverses the limiting effects of clomiphene citrate on early embryonic development in the in vitro perfused rabbit ovary.

This study examined whether the addition of estradiol (E2) to the perfused rabbit ovary would reverse the deleterious effects of clomiphene citrate (CC) on early embryonic development. Ovaries were perfused with CC (10(-5) M) or CC + E2 (1 to 1000 ng/ml). Human chorionic gonadotropin (hCG, 50 IU) was added to the perfusate of each ovary. In vitro ovulated ova in cumulus were retrieved and inseminated in vitro. E2 significantly increased the percentage of ovulated ova achieving (1) the 2-cell stage at 36 hours, (2) the morula stage by 84 hours, and (3) the blastocyst stage at 132 hours. The percentage of inseminated ova showing evidence of degeneration was reduced in ovaries treated with E2. These data suggest that CC may exert an antiestrogenic effect on the intrafollicular oocyte, which interferes with postfertilization development.

Animals↗
PubMed1986

Effect of clomiphene citrate on in vitro ovulated ova.

The effect of clomiphene citrate (CC) on developmental capacity of ovulated ova was studied with isolated in vitro perfused rabbit ovaries. Fifty-two ovulated ova were recovered from ovaries perfused with human chorionic gonadotropin (hCG) in a medium containing CC and 45 ova from ovaries perfused with hCG in a CC-free medium. Ova were cultured and inseminated with capacitated sperm and observed serially for evidence of fertilization and stage of development. CC did not affect the fertilization of ovulated ova. However, the percentage of ova which had reached the morula stage by 60 hours was significantly reduced in the CC-treated (15.4%) group, compared with the control group of ovaries (48.9%). A significant percentage of inseminated ova from CC-treated ovaries (65.4%) showed evidence of degeneration, as compared with control ovaries (37.8%). Thus, a partial loss of developmental capacity may explain the discrepancy observed between the rate of successful ovulation induction and the establishment of pregnancy associated with CC administration in humans.

Animals↗
PubMed1986

The effect of ovarian steroidogenesis on ovulation and fertilizability in the in vitro perfused rabbit ovary.

The effects of aminoglutethimide phosphate (AGP) on ovulation, ovum maturation, fertilizability, and steroid production were studied with the use of an isolated perfused rabbit ovary preparation. AGP (10(-3) or 10(-4) M) was added to the perfusate of one ovary. The contralateral control ovary was perfused in medium alone. Thirty minutes later human chorionic gonadotropin (hCG) (50 IU) was added to the perfusate of all ovaries. No difference was observed in time of ovulation or ovulatory efficiency between controls and AGP-treated ovaries. The degree of ovum maturity and degeneration was also comparable in the two groups. Progesterone and estradiol production were significantly reduced by AGP treatment. A second experiment examined fertilizability of ova ovulated in vitro after perfusion with 10(-3) M AGP. AGP significantly reduced the rate of normal fertilization as observed 12 h after insemination. The percentage of inseminated ova with evidence of degeneration was greater in ova from AGP-treated ovaries than in those from controls, however, this difference was not significant. The study indicates that AGP affects neither hCG-induced ovulation nor meiotic resumption; however, fertilizability of ova from ovaries treated with AGP is impaired. These data suggest that the intrafollicular steroid environment may participate in cytoplasmic maturation of ovulated ova.

Aminoglutethimide↗
PubMed1982

Actions of hormones and other factors upon oocyte maturation.

Oocyte maturation is controlled by a combination of hormonal and local follicular factors. Osmolarity, pH, and perhaps Ca2+ concentration of the surrounding medium are also important. Follicular fluid contains a low molecular weight OMI which acts to keep the oocyte from maturing. Luteinizing hormone added to cultured cumulus enclosed porcine oocytes can reverse the inhibitory action of OMI. The level of OMI in the follicular fluid appears to decrease as the follicle matures. Addition of FSH and prolactin to cultured granulosa cells stimulates OMI secretin whereas addition of testosterone or dihydrotesterone brings about a decrease in OMI secretion. Elevated LH in vivo may bring about oocyte maturation before ovulation by (a) an antagonist action on OMI; (b) stimulating the synthesis of testosterone by theca cells and thus inhibiting the synthesis of OMI by granulosa cells; and (c) action on the granulosa cells to promote luteinization which may also cause a decrease in OMI synthesis. The hastened oocyte maturation associated with follicular atresia could be due to a decline in OMI due to granulosa cell death and/or elevated follicular androgens.

Androgens↗
PubMed1980

The relationship between high-affinity binding of cytochalasin B to 3T3 cells and inhibition of sugar transport and cell motility.

Transport and motility inhibitors have been used to classify different types of high-affinity cytochalasin B (CB) binding sites in 3T3 cells. The potency of phloretin and phlorizin as inhibitors of sugar uptake paralleled their effectiveness in displacing high-affinity bound CB from the cells, indicating that the two compounds compete with CB for binding to sites associated with sugar transport proteins. On the other hand, cytochalasins D and E, which did not inhibit sugar uptake, inhibited binding of CB to a portion of the high-affinity sites, most probably those associated with actin-containing cytoskeletal-contractile structures. A small amount of high-affinity CB binding remained in the presence of both phloretin and cytochalasin E, indicating that the cells have a third class of sites which is not related to either sugar transport or cell motility, When isolated membranes were examined, it was found that a fraction of each class of high-affinity CB binding sites were associated with the fraction. In contrast, only sites sensitive to cytochalasin D were recovered in a soluble extract of the cells.

Animals↗
PubMed1978

Dihydrocytochalasin B. Biological effects and binding to 3T3 cells.

Dihydrocytochalasin B (H2CB) does not inhibit sugar uptake in BALB/c 3T3 cells. Excess H2CB does not affect inhibition of sugar uptake by cytochalasin B (CB), indicating that it does not compete with CB for binding to high-affinity sites. As in the case of CB, H2CB inhibits cytokinesis and changes the morphology of the cells. These results demonstrate that the effects of CB on sugar transport and on cell motility and morphology involve separate and independent sites. Comparison of the effects of H2CB, CB, and cytochalasin D (CD) indicates that treatment of cells with any one of the compounds results in the same series of morphological changes; the cells undergo zeiosis and elongation at 2-4 microM CB and become arborized and rounded up at 10-50 microM CB. H2CB is slightly less potent than CB, whereas CD is five to eight times more potent than CB in causing a given state of morphological change. These results indicate that the cytochalasin-induced changes in cell morphology are mediated by a specific site(s) which can distinguish the subtle differences in the structures of the three compounds. Competitive binding studies indicate that excess H2CB displaces essentially all of the high-affinity bound [3H]CB, but, at less than 5 x 10(-5) M H2CB is not so efficient as unlabeled CB in the displacement reaction. In contrast, excess CD displaces up to 40% of the bound [3H]CB. These results suggest that three different classes of high-affinity CB binding sites exist in 3T3 cells: sites related to sugar transport, sites related to cell motility and morphology, and sites with undetermined function.

3T3 Cells↗
PubMed1976

High-affinity cytochalasin B binding to normal and transformed BALB/3T3 cells.

To study the molecular basis of changes in sugar uptake rate in cultured mouse fibroblasts with different physiological states, we have measured the high affinity binding of [3H] cytochalsin B, a potent sugar transport inhibitor, to actively growing and contact inhibited Balb/3T3 cells as well as to 3T12 and SV3T3 cells. Binding was the same whether the cells were detached from dishes with EDTA or trypsin. The amount of drug bound to intact cells measured with a centrifugation assay was essentially the same as that bound to cell sonicates measured with equilibrium dialysis. Cytochalasin B binding to intact cells was extremely rapid and reversible over a wide range of drug concentrations, and was not affected by 0.1 M D--glucose in the assay medium. Actively growing and contact inhibited 3T3 cells had a similar number of high affinity cytochalasin B binding sites per cell, while 3T12 and SV3T3 cells had one third to one fourth the number of sites per cell. However, the number of sites per mug cellular protein appeared to be similar for cells in all of the physiological states examined.

Animals↗