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R J Ryan

Publications and source records attributed to R J Ryan.

At least 73 records · Page 4Linked to original sources
PubMed1980

Interactions of gonadotropins with corpus luteum membranes. VIII. The different properties of rat luteal cell light and heavy membranes cannot be explained by fractionation of inside-out and outside-out plasma-membrane vesicles.

Fractions enriched in luteal cell plasma-membranes were isolated from superovulated rat ovaries. Cell surface-membrane marker enzyme activities were measured in both light and heavy membrane fractions, with or without treatment with various detergents, to assess whether these fractions consisted of resealed vesicles with different orientations (i.e. inside-out or outside-out). Control and digitonin-treated membranes were also fractionated on sucrose-density gradients to monitor the buoyant density perturbation of each surface-membrane marker induced by this detergent. In another experiment, hCG-binding sites of superovulated rat ovaries were labelled in vivo by injecting [131I]hCG intravenously 2 h prior to fractionation and isolation of ovarian membranes. Membranes were then tested for the ability to bind [125I]hCG and [131I]hCG in vitro. These experiments indicated that light and heavy rat luteal cell membrane fractions had similar levels of inside-out membrane vesicles (ranging from 0 to 34%), and that the hCG-binding sites of the 2 fractions appeared to be equally freely accessible to hormone in vivo. It is concluded that differences in membrane orientation cannot account for the distinct properties and marker enzyme profiles of rat ovarian light and heavy membranes, providing further support that these membrane are derived from different regions of the luteal cell surface-membrane.

5'-Nucleotidase↗
PubMed1980

Specific binding of human chorionic gonadotropin to human corpora lutea in the menstrual cycle.

Luteal tissue from 26 premenopausal women undergoing surgery for nonendocrine disease was examined for specific binding to human chorionic gonadotropin. Results showed a nadir in the percentage of binding on day 10, with a gradual increase until maximal binding was obtained on days 22 through 26. Binding then markedly declined to that seen on day 1 of the menses and decreased gradually to its lowest level on day 10.

Adult↗
PubMed1980

Anovulation with estrogen production: receptor disorders?

Receptor antibodies have been implicated in the pathogenesis of several autoimmune disorders such as Graves disease. The authors hypothesized that serum antibodies against the luteinizing hormone (LH) receptor existed in women with chronic anovulation syndrome and continuously stimulated the ovaries. Twenty patients with the clinical diagnosis of anovulation with estrogen production were studied. The effects of serum globulins on the binding of 125I-labeled human chorionic gonadotropin (hCG) to ovarian receptors in the patients were compared with the effects in age-matched controls. These studies did not demonstrate significant inhibition of 125I-hCG binding to ovarian receptors by immunoglobulins of patients with anovulation and estrogen production in comparison with those of control subjects. This finding suggests that the cause of anovulation with estrogen production is not an autoimmune phenomenon involving the LH receptor of the human ovary.

Adenylyl Cyclases↗
PubMed1980

Preparation of GTP sensitive adenylate cyclase from luteinized rat ovaries.

Previous studies have shown that human chorionic gonadotropin stimulation of rat ovarian adenylate cyclase activity is enhanced but not augmented by GTP. Extraction of crude rat luteal membranes with 2M urea induced a GTP augmentation of hCG stimulation of adenylate cyclase activity of 3.5 fold. This augmentation of hormonal stimulation of adenylate cyclase activity by GTP was not accompanied by a decrease in hormone binding such as has been observed with other hormonally stimulated adenylate cyclase.

Adenylyl Cyclases↗
PubMed1979

Premature menopause. I. Etiology.

The premature menopause syndrome has been regarded as one of the organ-specific autoimmune disorders because circulating antibodies to ovarian tissue have been demonstrated. Fifteen women with spontaneous cessation of menses after initial menarche before they were 35 years old were seen between 1975 and 1977. Increased serum levels of gonadotropin and failure of estrogen secretion were documented. Serum from each woman was examined for antibodies to normal ovary. Proteins from ovaries of normal premenopausal women were extracted and iodinated with 125I. The labeled proteins were incubated with sera for 48 hours, after which goat antihuman gamma-globulin was added and allowed to incubate for 72 hours. The precipitate was washed and evaluated for radioactive label. The binding of antibodies increased in the sera of patients with the premature menopause syndrome, compared with the control sera. This suggests that the etiology of premature menopause may be mediated by circulating antibodies to ovarian tissue.

Adult↗
PubMed1979

Interactions of gonadotropins with corpus luteum surface membranes. V. Differential effects of digitonin on the buoyant densities of light and heavy rat ovarian membrane fractions.

Previous studies have indicated that rat luteal cells at certain stages of development can be fractionated so as to obtain two plasma membrane fractions with different densities and different profiles of marker enzymes. The light membrane fractions (density 1.13) contain the majority of hCG-binding sites and little or no cyclase enzyme, while the heavy membranes (density 1.17) contain the majority of cyclase enzyme and lesser quantities of hormone-binding sites. These membrane fractions were further compared with respect to their susceptibility to perturbation by digitonin. The buoyant density of luteal cell light membrane fractions, as marked by [125I]iodo-hCG binding, Mg2+-dependent ATPase, and 5'-nucleotidase, were highly perturbable by digotonin (delta density, greater than 0.05), while adenylate cyclase activity and phosphodiesterase activity associated with this fraction were only slightly perturbed (delta density, less than 0.02). The buoyant density of luteal cell heavy membrane fractions, as marked by adenylate cyclase, ATPase, and nucleotidase, was not significantly perturbed by digotonin. The hCG binding associated with the heavy membrane fraction was not perturbed by digitonin. From these studies, we conclude that the adenylate cyclase activity associated with light membrane fractions is due to contamination by heavy membranes, while the hCG-binding activity in heavy membrane fractions is intrinsic to that membrane. Except for the lysosomal marker (glucuronidase), which was solubilized by digitonin, the detergent had no significant effect on the density of mitochondrial, Golgi, GERL (Golgi, endoplasmic reticulum, and lysomal), or endoplasmic reticulum membranes. Plasma membranes from isolated granulosa cells and ovaries obtained 24 h after priming with PMS gonadotropin-hCG behaved as heavy membranes (density, 1.17) which contained hCG-binding sites, adenylate cyclase, nucleotidase, and Mg2+-dependent ATPase. These were not significantly perturbed by digitonin. The appearance of light membranes and the segregation of adenylate cyclase from the majority of hCG-binding sites is a development feature of the luteal cell.

Adenylyl Cyclases↗
PubMed1979

FSH stimulation of 3H-glucosamine-incorporation into proteoglycans by porcine granulosa cells in vitro.

Porcine granulosa cells from small follicles were incubated in the presence of 1 muCi/ml 3H-glucosamine and various hormones. Proteoglycans were digested with protease, and the mucopolysaccharides (MPS) were recovered. Most of the labeled MPS was found in secretory products. Maximum incorporation of 3H-glucosamine into MPS occurred after incubation with FSH for 8--16 h. Cell concentrations of 0.5--4.0 x 10(6)/ml proved to be ample. Highly purified porcine or human FSH gave consistent, significant stimulation by doses in the order of 100 pg/ml. Linear log-dose response curves occurred from 0.1 to 10.0 ng/ml, and maximal stimulation at 10 ng/ml was 22-fold above control. Preparations of hCG, hTSH and NIH-LH-S18 were not effective. Incubations with 1--10 mM dibutyryl cyclic AMP significantly increased incorporation into MPS, suggesting that effects of FSH may be mediated by cyclic AMP.

Animals↗
PubMed1979

A search for antibodies to luteinizing hormone receptors in premature ovarian failure.

We recently published evidence of the presence of circulating antibodies in the sera of patients who had the diagnosis of premature menopause syndrome. This led to the question: Is there a circulating antibody in the sera of patients with premature menopause syndrome which interferes with gonadotropin-luteinizing hormone (LH) receptor interaction on the luteal cell surface? Serum samples from 14 women with the diagnosis of Premature menopause syndrome were examined to see whether they would block the binding of 125I-labeled human chorionic gonadotropin (hCG) to human corpora lutea. All patients had spontaneous cessation of menses before the age of 35 years and documentation of increased gonadotropin secretion and failure of estrogen secretion. When the sera of the study group were incubated with 125I-labeled hCG and LH receptor from human corpora lutea, no difference in binding was observed when compared with controls. This suggests that there is no circulating antibody that interferes with hCG-LH receptor interaction and that would thereby lead to loss of ovarian function in premature menopause syndrome.

Adult↗