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Biomedical subjects

M Shemesh

Publications and source records attributed to M Shemesh.

At least 55 records · Page 3Linked to original sources
PubMed1984

Foetal testicular steroidogenesis and responsiveness to LH in freemartins and their male co-twins.

Foetal gonads were obtained from 1) 8 male foetuses that were co-twin to freemartins, 2) 8 isosexual twins, 3) 59 singletons of 45-75 days of gestations, 4) 5 isosexual and 5 male co-twins of 90-120 days and 5) 5 freemartins at 70-120 days of gestation. The gonads were incubated in supplemented medium 199 for 24 h in the absence or presence or LH and the testosterone and progesterone produced measured by RIA. During the time of sexual differentiation (45-75 days) the testes of the male co-twins produced significantly less testosterone than testes from isosexual or singletons of the same age. Testes of foetuses older than 90 days were refractory to LH-stimulation, but freemartin ovaries and testes from their male co-twins continued to respond to LH with increased testosterone production. No significant differences in progesterone production were detected amount co-twins, isosexual twins or singletons at any age. We conclude that the testes of the male twin that is co-twin to a freemartin displays abnormal steroidogenesis. This may be related to reports of abnormal testes after birth in males co-twin to freemartins.

Animals↗
PubMed1984

Modulation of bovine placental prostaglandin synthesis by an endogenous inhibitor.

An endogenous, heat-labile, inhibitor of prostanoid synthesis in maternal caruncle tissue of bovine placentomes was studied. Inhibitory activity was present in caruncle extracts from days 120-250 of gestation, but was not detectable at term (260-280 days). The disappearance of inhibitory activity coincided with an increase in the secretion of prostanoids by dispersed caruncle cells in culture. Coculture of caruncle cells from placentomes of 120-day gestation with fetal cotyledon cells resulted in suppression of prostanoid synthesis by the cotyledon cells. However, this inhibition was not observed in cocultures of dispersed caruncle cells and fetal cotyledon cells from term placentomes. Our findings indicate that an endogenous inhibitor modulates bovine placental prostaglandin synthesis. A decline in the level of this inhibitor at term may be one factor triggering increased prostanoid synthesis required for parturition.

Animals↗
PubMed1984

The role of 17 beta-estradiol in the recovery from oviductal prolapse in layers.

Plasma 17 beta-estradiol concentrations, thecal estrogen content, and uterine prostaglandin synthetase activity were measured in healthy and prolapsed hens as well as in layers that recovered after exposure to low intensity lighting (250 or 50 lx). The effect of estradiol benzoate injections (100 ng, 3 X per week) in hens exposed to high intensity light (greater than 500 lx) was also studied. Prolapsed hens had significantly lower plasma 17 beta-estradiol concentrations (60 +/- 12 pg/ml; mean +/- SEM) than recovered (374 +/- 40 pg/ml) or healthy hens (475 +/- 45 pg/ml). Theca cells from recovered hens had a significantly higher content of 17 beta-estradiol (.7 ng/5 X 10(5) cells) than theca cells from normal or prolapsed birds (.3 ng/5 X 10(5) cells). Microsomes prepared from the uteri of prolapsed hens converted significantly less arachidonic acid to prostaglandin metabolites (4.4%) than did microsomes from healthy or recovered birds (9.0%). Treatment of prolapsed hens with estradiol benzoate resulted in 89% of the birds recovering within 3 weeks compared to a 4% recovery rate in the controls. We conclude that restoration of peripheral 17 beta-estradiol concentrations to normal levels was concomitant with recovery in prolapsed birds, and suggest that the estrogen exerts its effect by raising the level of prostaglandin synthetase activity in the uterus.

Animals↗
PubMed1983

Partial purification of a chorionic gonadotropin-like protein from bovine cotyledons.

The presence of placental gonadotropin activity in early pregnancy was studied in the cow. Cotyledons from the first trimester of gestation were used to isolate a chorionic gonadotropin-like (CG-like) protein by means of ammonium sulfate precipitations (0.17-4.5 M) and gel filtration on Sephadex G-100 and DEAE-Sephadex. The CG-like activity was measured by a radioreceptor assay (RRA) specific for human chorionic gonadotropin (hCG). Luteotrophic activity was also assessed in two separate in vitro bioassays using cultures of bovine granulosa and rat Leydig cells. It was found that the 3 M ammonium sulfate precipitate of cotyledon extracts contained a CG-like activity of 179 mIU/mg protein as measured by RRA. The precipitate inhibited 125I-hCG binding in a linear fashion. A ninefold increase in specific activity was achieved by further purification on Sephadex G-100 (800 mIU/mg protein) and Sephadex-DEAE (1600 mIU/mg). In experiments with cell cultures, it was found that 20 micrograms of protein eluted from Sephadex-DEAE (equivalent to 16 mIU of hCG as determined by RRA) added to the culture medium significantly enhanced (P less than 0.05) progesterone production by the granulosa cells and testosterone production by the Leydig cells. We conclude that the bovine placenta contains a chorionic gonadotropin which may serve to maintain the corpus luteum of pregnancy.

Animals↗
PubMed1983

Bovine placentomes contain factors which decrease progesterone secretion.

We examined the effects of 20% ammonium sulfate precipitates from cytosolic extracts of whole placental tissue collected between 100-150 days of gestation on progesterone secretion by bovine granulosa cells and dispersed bovine luteal cells. These extracts produced a dose-dependent inhibition (23-92%) of progesterone synthesis by bovine granulosa cells. However, no inhibitory activity could be demonstrated in similarly prepared extracts from term placentae. Inhibitory activity could be extracted from both maternal caruncles and fetal cotyledons. In the presence of 2 mg/ml of maternal caruncle extract, basal progesterone secretion was dramatically reduced (90%), as was steroidogenesis in the presence of bovine lutenizing hormone (bLH) and 8 bromocyclic (Br)-cAMP. Moreover, coincubation of dispersed luteal cells and dispersed fetal or maternal placental cells from 100- to 150-day placentae produced a significant (50%) reduction in progesterone content of the medium. The addition of 2 mg/ml of caruncle or fetal cotyledon extract from 100- to 150-day placentae also produced 100% and 50% inhibitions, respectively, of progesterone secretion by dispersed placental cells. Thus, the inhibitory factor appears to be produced by cells of both the maternal and fetal placenta. It is heat-stable and not extractable by ether. The inhibitory substance eluted was two distinct peaks from Sephadex G-100 columns, one with a molecular weight of about 60,000 daltons and the other about 30,000 daltons. Using isoelectric focusing, several peaks of inhibitory activity were obtained, one with a pI of 3-5, the others having pIs between 6 and 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Isolation and characterization of a 94,000-dalton protein with thyrotropic activity from early bovine placenta.

A thyrotropic protein was extracted and purified from the placenta of early bovine gestations. After protein extraction, the 45-60% ammonium sulfate precipitate of maternal and fetal bovine cotyledons was found to compete with thyroid stimulating hormone (TSH) for binding to thyroid cell membranes and to mediate TSH specific biological effects including the stimulation of cyclic AMP production, iodide uptake, and thyroxine secretion. The placental thyrotropin was further purified by gel and anion exchange chromatography, followed by binding to thyroid cell membranes and elution by mild acid treatment. 400 micrograms of isolated protein with 4.5 units of TSH-like binding activity/mg of protein was recovered from the placenta of a 90-day-old bovine gestation, representing 2 X 10(-4%) of its original wet weight. The placental thyrotropin appeared to be a 94,000-dalton protein with pI 6.0 and composed of two noncovalently associated chains of 50,000 and 44,000 daltons. The placental 94,000-dalton thyrotropin bound to TSH membrane receptors and induced specific TSH-mediated biological effects, but was structurally and immunologically distinct from TSH and hypophysical or placental gonadotropins.

Animals↗
PubMed1982

The interaction of cultured thyroid cells of early bovine embryos with thyrotropin and thyroglobulin.

We have prepared primary thyroid cell cultures of early bovine embryos from the first trimester of pregnancy in order to study the ontogeny of their interaction with TSH and thyroglobulin (Tg). The ability of these cells to synthesize and secrete Tg, as well as the trophic effect of TSH on the organization of the thyroid cells, were also investigated. To determine the maturation of these functions we prepared fluorescent conjugates of TSH, Tg, and anti-Tg antibodies, and visualized their interaction with the thyroid epithelial cells. Our study shows that the ability to bind TSH and Tg exists as early as the gestational age of 3 cm crown-rump length (CRL; 40 days) but does not develop linearly with embryonic age. Thus, there is a significant increase in the percentage of Tg-binding cells at 12 cm CRL, when colloid is first noticed in vivo, and a considerable elevation in TSH-binding cells around 15 cm CRL, when thyrotropic cells and TSH secretion from the fetal pituitary are first evident. Tg-containing cells and the ability to secrete Tg are observed at about 20 intrauterine days. The three thyroidal properties probably develop independently since only part of the Tg-containing cells bind Tg or TSH, and a significant proportion of the cells that exhibit Tg-binding do not bind TSH. The results support the notion that TSH is essential for the formation of follicle-like structures and effects the organization of thyroid cells into a functional structure in vitro from the late precolloidal stage.

Animals↗
PubMed1981

The ontogeny of the thyrotropin-thyroid axis in early bovine embryos.

T4 and T3 formation and their response to TSH, cAMP, and prostaglandin E2 (PGE2) stimulation were studied by RIA in cultured bovine fetal thyroids from 130 embryos of 1.2-25.0 cm crown-rump length (CRL). T4 and T3 were found in all of the freshly isolated glands studied, and their concentrations increased significantly (P less than 0.05) during a 24-h incubation of glands from fetuses with a CRL greater than 8.0 cm. The release of T4 (nanograms per mg tissue), but not of T3, increased consistently with CRL (r = 0.64; P less than 0.05). The addition of TSH (0.5 mU) to the culture medium induced a 2- to 3-fold increase in the secretion of T4, but not of T3, by glands of fetuses with a CRL of 3.0-25.0 cm (P less than 0.05). Dibutyryl cAMP (10(-4) M) and PGE2 (10(-4) M) had comparable effects. A combination of TSH and theophylline (1 mM) or of TSH and dibutyryl cAMP significantly enhanced the T4 released by cultured tissue into the medium (P less than 0.05) over that induced by either agonist, but the combined effect was not fully additive. The total PGE2 in the tissue and medium was not changed by the addition of 0.5 mU TSH, and indomethacin had no effect on TSH-induced T4 secretion. The data show that thyroids of fetuses that have reached a CRL of 3.0 cm have the enzymatic capacity to produce both T4 and T3, and T4 is the dominant product formed. While exogenous PGE2 at high concentrations stimulates fetal T4 secretion, it does not mediate the actions of TSH and cAMP on the fetal thyroid.

Adenosine↗
PubMed1981

Iodine metabolism and the effect of TSH in thyroid glands of early bovine embryos.

The ontogeny of the thyrotrophin-thyroid axis during the first trimester was studied in 104 bovine embryonic thyroids taken from foetuses of crown-rump length 1.4 to 19.2 cm (25-120 days). The uptake of labelled iodine in vitro in the absence or presence of TSH was measured. The per cent incorporation of radioiodine into iodotyrosines and iodothyronines in the presence and absence of TSH was also studied. It was found that the foetal tissue displayed radioiodine uptake by 25 days of foetal life and the uptake increased with age. TSH caused a further increase in radioiodine uptake in foetuses of 40 days or older. Incorporation of radioiodine into MIT and DIT was apparent at 25 days and into T3 and T4 by 40 days of foetal life. Addition of TSH increased the proportion of total radioiodine found as DIT and thyroxine in foetuses of 40 days older. This TSH stimulation of radioiodine incorporation increased with age. However, the proportion of radioiodine found as MIT and T3 was not affected before 120 days of foetal life. This was in marked contrast to the adult thyroid where the proportion of radioiodine found as T3 was increased by the addition of TSH. It is concluded that the foetal thyroid can respond to TSH by at least 40 days of foetal life and that this response differs from that seen in the adult.

Animals↗
PubMed1981

Altered steroidogenesis by the fetal bovine freemartin ovary.

Ovaries were taken from 12 freemartins of crown-rump length 4.2-27.5 cm (47-130 days of gestation), 16 singleton fetuses of 5-8 cm (55-75 days) and 18 single fetuses of 10-20 cm (78-108 days). Ovaries were incubated for 24 h in tissue culture Medium 199 supplemented with 5% calf serum. The freemartin ovaries produced 0.16-2.1 ng testosterone/ovary/24h compared with less than 50 pg for normal singleton ovaries. Oestrogen was undetectable n the ovaries (less than 50 pg) of freemartin fetuses of crown-rump length 4.2-9.4 cm (47-77 days), while 16 normal ovaries of the same stage produced 1375 +/- 300 pg/ovary/24 h. The presence of abnormally high amounts of testosterone and the absence of normally occurring oestrogen in the freemartin ovary indicate that the pattern of steroidogenesis in the freemartin is altered as early as 47 days of gestation.

Animals↗
PubMed1981

Effects of phyto-oestrogens on progesterone synthesis by isolated bovine granulosa cells.

The effects of phyto-oestrogens on progesterone synthesis by isolated bovine granulosa cells in vitro were assessed. Various concentrations (0.37-3700 nmol/1) of biochanin A, genistein or oestradiol were added to cultures of bovine granulosa cells and the consequent changes in progesterone synthesis were measured. The effects of alkali-soluble extracts of Rhodes grass (Chloris gayana) and fodder beet (Beta vulgaris, var.) were also examined. Another series of experiments tested the effects of genistein and oestradiol on the increase of progesterone synthesis brought about by the addition of LH to the culture medium. It was found that biochanin A and genistein increased progesterone synthesis by 40-50% when added in concentrations of 3.5 and 185 nmol/1 respectively. At higher concentrations of phyto-oestrogens greater than 176 nmol/1 for biochanin A and 1850 nmol/1 for genistein. Oestradiol showed similar effects: maximum stimulation of progesterone secretion occurred in the presence of 0.184 nmol/1; inhibition was found with concentrations of greater than 1.84 nmol/1. Extracts of Rhodes grass but not of fodder beet also showed biphasic effects. Both genistein and oestradiol in high concentrations (3700 and 3671 nmol/1 respectively) inhibited the increase in progesterone synthesis provoked by LH. The data indicated that phyto-oestrogens, like oestradiol, have a dose-related, biphasic effect on steroidogenesis in the isolated bovine granulosa cell system.

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PubMed1979

Steroidogenesis and prostaglandin synthesis by cultured bovine blastocysts.

Bovine blastocysts were collected at Days 13, 15 and 16 and placed in TCM-199 supplemented with 5% fetal calf serum; some blastocysts were immediately frozen while the others were cultured for 48 h and then frozen. Samples (tissue + medium, 5--12/group) were thawed, homogenized and analysed by radioimmunoassays. Measurable amounts of progesterone were found in all blastocysts but values were higher (P less than 0.01) after culture. Testosterone was not found in the cultured or uncultured blastocysts at Day 13, but was detectable on Days 15 and 16 and in greater amounts (P less than 0.05) in the cultured blastocysts. PGF and PGE-2 were increased (P less than 0.05) in the cultured blastocysts in all 3 days. Oestradiol was measurable in some but not all blastocysts. It is suggested that PG synthetase and enzymes capable of synthesizing progesterone, testosterone and, possibly, oestradiol are present in these early bovine blastocysts.

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