Role of the gonads in hypertension-prone rats.
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In a genetically hypertension-prone (S) strain of rats it was observed previously that males generally developed hypertension more rapidly on a high salt diet than did females although final pressure ultimately were similar in both sexes. A genetic study had shown that there was no sex-linkage involved in setting blood pressure levels, so it was thought that the gonads might be involved. In the present work, castration of males had no effect on blood pressure but in the females it caused a rise in pressure that could not be distinguished from that in males, both on a high and low salt diet. Castration resulted in greater growth in females than in controls, whereas it had the opposite effect in males. It was speculated that these changes were due to influences on pituitary growth hormone with castration increasing the net output of growth hormone (or enhancing receptor sensitivity to it) in the female and the opposite in the male. From the work of others, there are some data compatible with such an interpretation. Experimentally, growth hormone will induce hypertension in rats. Therefore, it is conceivable that growth hormone is involved in the increment in hypertension observed in these castrate females. Because the effect on blood pressure was observed in castrate females on both high and low NaCl diets, it was considered unlikely that the blood pressure effect was simply due to increased NaCl intake in the food associated with greater growth. It was suggested that this rise in blood pressure with cessation of ovarian function might bear on the unsettled question of "menopausal" hypertension in women: in the genetically susceptible individual an increase in growth hormone associated with declining ovarian funtion in the menopause could provide the stimulus for the appearance of hypertension some years earlier than would otherwise have been the case. (+info)
Production of carbon dioxide in vitro by blastocysts from intact and ovariectomized mice.
(74/1479)
'Normal' and 'delayed implanting' mouse blastocysts were incubated in non-radioactive culture medium for various lengths of time (preincubation), and then placed in culture medium with (14-C)-glucose for 2 hr. The rate of embryonic CO-2 given off by the blastocysts. Normal embryos were unaffected by the length of preincubation. By contrast, 'delayed implantating' embryos had a low level of CO-2 production with short preincubations (i.e. less than 2 hr), but approached the normal range with longer preincubations (i.e. more than 8 hr) and thus, were 'activated ' in vitro. Incubation of the 'delayed implanting' embryos with actinomycin D prevented the expected increase in CO-2 production, indicating that synthesis of new RNA is necessary for their activation. Preincubation of normal and 'delayed implanting' blastocysts with oestradiol-17 beta and/ or progesterone had no effect on the level of CO-2 production, suggesting that the hormones do not directly stimulate or inhibit carbohydrate metabolism in the embryos. (+info)
Uterine response to ovariectomy during the proliferative and luteal phases in the marsupial, Trichosurus vulpecula.
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The uterine luteal phase in T. vulpecula is not dependent upon the secretions of the CL throughout its duration. Ablation of the CL or ovariectomy after Day 7 of the 26-day oestrous cycle does not result in the termination of the uterine secretory phase. The dependence of the luteal phase on the secretions of the CL is demonstrated by ablation of the CL or ovariectomy on Days 2, 4, 8, 12 and 24 of the oestrous cycle. Ablation of the CL before Day 8 resulted in the inhibition of the impending luteal phase, and the commencement of a follicular phase resulting in oestrus 8 to 9 days later. Removal of the CL or ovariectomy on Days 8 or 12 does not completely inhibit the uterine luteal phase since sufficient precursor of uterine milk is stored in the uterine basal glandular epithelium, thus enabling the endometrium to maintain the secretion of uterine milk. (+info)
Motility of the oviduct and uterus of the cow during the oestrous cycle.
(76/1479)
Recordings of electrical activity of the oviduct and uterus were obtained during three oestrous cycles in cows fitted with an extra-cellular multi-electrode assembly. The stages of the cycle were identified by the appearance of the cervico-vaginal secretions and changes in the peripheral plasma level of progesterone were determined by radioimmunoassay. A gradual transition from local non-propagating electrical activity to propagating electrical activity with increase in the duration of contractions and then of their amplitude occurred 48 hr before the onset of oestrus. The transition coincided with a rapid decrease in progesterone level from 5 to 10 ng/ml to less than 0-1 to 0-4 ng/ml. This phenomenon was recorded from all uterine electrode sites, but was most marked at the uterotubal junction. Two days before oestrus, trains of potentials and bursts of activity became progressively grouped, apparently randomly, into prolonged phases in the distal portion of the oviduct and over the entire myometrium. During oestrus, the phases of activity became synchronized at these sites and both their amplitude and frequency reached a maximum. The strength but not the frequency of the phases diminished progressively 3 days after oestrus, followed by relative inactivity. The last remaining zone of activity was the uterotubal junction. During oestrus, the activities of the oviduct and the uterus were modified by oxytocin and adrenaline, the effect of the former being more marked on the uterus and that of the latter on the oviduct. (+info)
Estrogen stimulation of conjugase activity in the uterus of ovariectomized rats.
(77/1479)
Recent observations have indicated that uterine folic acid conjugase (pterolypolyglutamyl hydrolase) undergoes rhythmic variation during the reproductive cycle of the rat. In the present study conjugase activity and ratios of "total" folate to "free" folate were determined in uterine homogenates of ovariectomized rats, with ane without estrogen stimulation. An increase in conjugase levels and a relative increase in the "free" folate component occurred in castrated animals 12 to 18 hours following injection of 10 mug of estradiol-17beta. (+info)
The passage of spermatozoa through the cervix of ovariectomized ewes treated with progesterone and oestrogen.
(78/1479)
Thirty spayed ewes were used in a 2 x 3 split-plot factorial experiment (n = 5) in which oestrus was induced with 30 or 90 mug oestradiol benzoate (OB) following a period of progesterone priming. They were inseminated 36 hr after oestrogen and the numbers of spermatozoa in the caudal, mid- and cranial regions of the cervix (sub-plots) were estimated 1, 12 and 24 hr later. At each interval of time and for each region of the cervix, fewer spermatozoa were recovered from the ewes treated with 30 mug OB than from those treated with 90 mug (P less than 0-05). (+info)
Some biological properties of RMI 12,936, a new synthetic antiprogestational steroid.
(79/1479)
A new synthetic steroid, RMI 12,369, was examined for its contraceptive potential in rats and comparisons with ethinyloestradiol were also made. Marked differences in the biological effects of the compounds were found, RMI 12,936 having high antiprogestational but negligible oestrogenic activity. Administration of RMI 12,936 on Day 1 of pregnancy caused acceleration of egg transport, the initial changes being apparent within 12 hr of dosing. Termination of pregnancy was associated with a significant reduction in ovarian weight. On Day 8 of pregnancy, RMI 12,936 resulted in significant ovarian hypertrophy, apparent within 48 hr, possibly due to a luteotrophic stimulus of placental origin. Pregnancy could not be maintained by progesterone implants, indicating that utilization was inhibited. Egg transfer experiments indicated that the primary effects were probably on the maternal reproductive tract. Pregnancy was terminated after administration of RMI 12,936 ON Day 19. The compound also had antifertility activity following intravaginal administration. (+info)
Estrogen and antagonist-induced changes in endometrial topography of immature and cycling rats.
(80/1479)
The topographical changes of the luminal surface of the endometrium of immature and ovariectomized rats treated with estrogen, antagonists to estrogen, and progesterone. and during various stages of the estrous cycle and in pregnancy were examined by scanning electron microscopy. Massive increases in numbers and length of endometrial cell microvilli were observed at estrus, after injection of estradiol-17beta, diethylstilbestrol, estrogen plus progesterone. or the inhibitor C1628 to immature and ovariectomized rats. Withdrawal of the estrogen stimulus results in diminution of microvilli, producing a state identical to diestrus, during pregnancy, and after injection of progesterone, The estrogen antagonist appears to have both estrogenic and progestogenic properties, stimulating endometrial cell hypertrophy, secretion of protein, and production of numerous apical microvilli. (+info)