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Biomedical subjects

J Roos

Publications and source records attributed to J Roos.

At least 91 records · Page 5Linked to original sources
PubMed1981

Involvement of the adrenals in ovulation induced by unilateral ovariectomy in the rat.

The aim of this study was to investigate the mechanisms of the stress-related ovulatory effects of unilateral ovariectomy (ULO) when performed on diestrus III at 10.00-11.00 hr in 5-day cyclic female rats. Ovulation evoked by ULO was suppressed in adrenalectomized rats. An increase in blood progesterone within 1 hour after ULO was observed in non adrenalectomized rats and suppressed in adrenalectomized rats. Pentobarbital (PB) treatment (30 mg/kg, ip) concomitant with ULO at 10.00-11.00 hr on diestrus III did not prevent progesterone to increase at 12.00-13.00 hr. A partial blockade of ovulation resulted from PB treatment from 13.00 hr to 18.00 hr on diestrus III. No blockade of ovulation occurred following PB injection at 23.00 hr. It was concluded that progesterone released from the adrenals following ULO constituted the trigger of ovulation during a critical period of diestrus III extending from 10.00 to 23.00 hr.

Adrenal Glands↗
PubMed1980

Mechanisms of action of testosterone propionate on LH and FSH release by the pituitary gland in cyclic female rats.

The aim of this work was to determine whether changes in pituitary responsiveness to LRH could account for the effect of testosterone propionate (TP) on the gonadotrophic function of the pituitary in 4-day cyclic female rats. Doses of 250, 500 and 1000 ng LRH were injected ip on pro-oestrus at 15.30 h in rats either pre-treated with 5 mg TP on dioestrus II at 10.00 h or injected with 30 mg/kg pentobarbital (PB) at 13.00 h. LH release induced within 30 min by LRH was higher in PB than in TP-treated rats. Even by using 250 ng LRH full ovulation was observed on the morning of oestrus in PB-treated rats. On the other hand, only partial ovulation occurred whatever the dose of LRH used in TP-treated rats; a great number of luteinized follicles was shown to be constantly associated with post-ovulatory corpora lutea. While LRH caused a significant FSH release (30 min later) in TP-treated rats, no FSH release could be shown in PB-treated rats. The pituitary FSH content appeared to be decreased and the pituitary LH content remained unchanged while a sharp increase in both blood FSH and LH concentrations occurred following injection of 1000 ng LRH in TP-treated rats. Concomitantly a sharp decrease in the number of pituitary gonadotrophs (AB-PAS+) was observed. A significant decrease in the number of the small roundshaped PAS positive cells was also observed. The mechanisms whereby TP influences the function of the pituitary-ovarian axis are discussed in the light of these results.

Animals↗
PubMed1980

A hormonal and temporal analysis of the mechanisms involved in the control of ovulation induced by hemiovariectomy in the rat.

The present study was undertaken to investigate the mechanisms of the stress-related ovulatory effects of hemicastration in the rat. Previous work (Roos et al., 1976) had shown that ovulation induced by unilateral ovariectomy (ULO) was suppressed in adrenalectomized females when ULO was performed on dioestrus III at 10--11 h in 5-day cyclic rats. Using the same experimental schema an increase in blood progesterone within 1 to 4 hours after ULO has been found to be present in adrenal intact females and suppressed in adrenalectomized rats. PB treatment (30 mg/kg, i.p.) concomitant with ULO at 10--11 h on dioestrus III significantly decreased the number of ovulating females without preventing blood progesterone concentration to increase at 12--13 h. A partial blockade of ovulation resulted from PB injection at 13 or 18 h. The ovulatory effects of ULO observed in females injected with PB at 23 h on dioestrus III or at 5 h on prooestrus were identical to those observed in hemiovariectomized non PB treated females. Only a small proportion of hemiovariectomized females displayed an LH release at 15--16 h and 17.30 h--18.30 h on dioestrus III. In contrast a significant FSH release was observed in this interval of time following ULO. Microscopic examination of the ovaries on prooestrus at either 11 h or 16 h revealed the presence of corpora lutea with morphological features corresponding to very different stages of development. We can conclude that progesterone of adrenal origin constituted the trigger of ovulation and caused LH-release during a time period extending from 13 h to 23 h on dioestrus III following ULO in the rat.

Adrenalectomy↗
PubMed1978

Action of testosterone propionate on the gonadotrophic function of the pituitary gland in the cyclic female rat.

Four-day cyclic female rats were injected with 5 mg testosterone propionate (TP) at dioestrus II at 10.00. A blockade of ovulation was observed on the morning of oestrus in most of these animals. No LH surge occurred in the afternoon of pro-oestrus. By contrast the size of follicles exceeding 400 micrometer in diameter did not differ in the afternoon of pro-oestrus in TP-treated and control females. Moreover both the number of follicles and the blood FSH concentration appeared to be higher at 14.00 on pro-oestrus in TP-treated than in control females. The effects of TP in vivo are thus in agreement with the observations which showed that TP caused a blockade of LH release and the maintenance of FSH release in vitro.

Animals↗
PubMed1978

The adrenal cortex and the luteotrophic action of estrogens during the estrous cycle in the rat.

The aim of this study was to evaluate the effects of estradiol benzoate (EB) on ovarian progesterone secretion in the presence or in the absence of the adrenals. 4-day cyclic female rats were injected with 10 microgram EB on the morning of diestrus I. An increase in the rate of ovarian progesterone secretion in diestrus II at either 10--11 a.m. or at 2 : 30--3 : 30 p.m. was only observed in one of two experimental series. A very significant increase in the peripheral blood progesterone concentration was noted in adrenalectomized EB-treated females as compared to EB-injected intact females, thus suggesting that the adrenals might inhibit the luteotrophic action exerted by EB on the ovary. Experiments in dexamethasone (DEX)-EB-treated females confirmed this view. Peripheral blood progesterone concentration was significantly greater in DEX-EB-treated females than in EB-treated females. The possible mechanisms were discussed in the light of experiments involving the administration of metyrapone (MET) prior to EB injection. While blood progesterone concentration increased following MET-treatment only, no cumulative effects resulted from combined MET and EB-treatment. Progesterone of adrenal origin was then supposed to be implicated in the inhibitory action of the adrenal cortex on the luteotrophic action of EB in cyclic female rats.

Adrenalectomy↗
PubMed1977

Interlaboratory oral anticoagulant quality assessment by the Netherlands Federation of Thrombosis Services.

The 50 laboratories of the Netherlands Federation of Thrombosis Services, covering a population of 9 million and responsible for the laboratory control of approximately 150,000 patients under oral anticoagulation, have participated since 1974 in a voluntary external and internal quality control program. The external program comprises a monthly distribution to the member laboratories of a series of artificially prepared control blood samples, two of which are identical. The overall variation of the coagulation times found were 10% (CV) in 1974 and 8% (CV) in 1975. Performance improved rather abruptly at the beginning of 1975, after the application of a tight methodological standardization and improvement by the manufacturer of the thromboplastin preparation (Thrombotest) used by the great majority of the laboratories involved. The main source of variation was found to be random error in the Thrombotest determination, approximately 6%. Interbatch variation of Thrombotest and inter-aliquot variation of control blood samples both do amount to approximately 3%(CV). In terms of rabbit tissue thromboplastins, which have a lower sensitivity than Thrombotest (i.e., a flatter slope of the correlation between the PT and the anticoagulant effect), the total variation in the performance of the Dutch laboratories is 2.2--5.6% (CV), which is unusually low. The main reason for this is the fact that the laboratories can rely not only on the services of the manufacturer but also on a central information office and a reference laboratory responsible for the preparation of the control blood as well as the standardization (calibration) of thromboplastin.

Anticoagulants↗
PubMed1977

[New data on luteotropic mechanism of action of estrogens during the rat estrus cycle].

An increase in peripheral blood progesterone concentration was observed in diestrus II, at 17:30 in 4-day cyclic female rats subcutaneously injected with 10 microgram estradiol benzoate (EB) at 10:00-11:00 on diestrus I. Pentobarbital injection (30 mg/kg) at 13:30 on diestrus II did not prevent this effect on EB. By contrast PB injected at 13:30 on diestrus II as above completely suppressed the luteinizing or ovulating effects of EB. The action of estrogen on blood progesterone level was therefore concluded to be unrelated to the mechanisms underlying estrogen-induced ovulation luteinization in the cyclic female rat.

Animals↗
PubMed1976

Ultrastructural changes of pituitary gonadotropic cells in estrogen-treated pregnant rats.

An ultrastructural study of gonadotropic pituitary cells was performed in estrogen-treated pregnant rats. Estradiol-treatment on Day 10 of pregnancy led to signs of ovulation or luteinization on Day 12 in 50% of the animals. Degranulation was observed in the FSH and LH cells of estrogen-responsive rats, whereas in the unresponsive group, the same cells were intensely granulated. The FSH cells of the control group showed signs of degranulation which could be correlated with follicular development. LH cells were sometimes degranulated. The role played by FSH and LH cells in the triggering of ovulation and luteinization by estrogen in the pregnant rat is discussed in the light of the ultrastructural observations.

Animals↗