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S Plas-Roser

Publications and source records attributed to S Plas-Roser.

At least 19 recordsLinked to original sources
PubMed1988

Estradiol involvement in the luteolytic action of LH during the estrous cycle in the rat.

The study was undertaken to examine LH, prolactin (Prl) and estradiol involvement in the control of corpus luteum function during 4-day cycle in the female rat. A potent LHRH antagonist (Antag) and bromocriptine (BRC) were used to induce LH and Prl deprivation in 4-day cyclic rats. Both drugs were administered after the occurrence of LH and Prl release on the afternoon of proestrus. Blood progesterone (P) concentration on diestrus 1 at 24:00 hr was similar in Antag, Antag + BRC and BRC-treated animals and did not differ from P values in control females. It was then concluded that neither LH nor Prl were necessary for the corpus luteum to achieve its stage of maximal activity during the night from diestrus 1 to diestrus 2. By contrast higher P values were observed on diestrus 2 at 12:00 hr in Antag-treated rats than in those given Antag + BRC, BRC or in the controls. When given on diestrus 1 evening estradiol benzoate completely prevented this effect of Antag to occur in LH and Prl deprived females. These results allow to hypothesize that LH exerts luteolytic effects during the diestrous period of the cycle and also suggest a possible involvement of estradiol in the regression phase of the corpus luteum.

Animals↗
PubMed1985

Prostaglandins involvement in the formation of luteinized unruptured follicles in the cyclic female rat.

The purpose of this investigation was to study the role played by prostaglandins in advanced ovulation and in the formation of luteinized unruptured follicles (LUF) in cyclic female rats. Dose related effects on ovulation were observed in rats given LH on diestrus 2 at 16.30. A significant positive correlation was observed between the number of postovulatory corpora lutea (POCL) and the increasing doses of LH. By contrast the number of LUF was negatively correlated with LH. Indomethacin treatment by 6h30 after administration of an ovulatory LH dose significantly increased the occurrence of LUF at the expense of POCL. Conversely PGF2 alpha when administered by 6h30 after a subovulatory LH stimulation enhanced in a dose dependent manner the number of POCL with respect to the LH treated controls. Under a similar treatment with a subovulatory dose of LH, PGE2 remained without ovulatory effects. The mechanisms of the formation of LUF are discussed on the basis of these results.

Animals↗
PubMed1984

Does corpus luteum function autonomously during estrous cycle in the rat? A possible involvement of LH and prolactin.

This study examined the of LH and prolactin in the control of corpus luteum function during 4-day cycles in the rat. Bromocriptine (BRC) treatment was performed on proestrus or/and estrus morning that means before or after the preovulatory release of LH. This caused complete blood prolactin depression from the time of injection until diestrus 1 afternoon. This decrease in blood prolactin concentration was associated with a rise in the tonic level of LH secretion in those females which received BRC as soon as on proestrus. We first observed that injection on the morning of proestrus of doses of BRC capable of blunting prolactin secretion on proestrus afternoon did not significantly impair the preovulatory release of LH and did not prevent ovulation occurring during the following night. The life span of the corpora lutea edified from ovarian follicles rupturing before or under BRC administration did not exceed that of those formed under physiological circumstances since 4-day cycles culminating in ovulation constantly took place in all the treated animals whatever the time of BRC injection. To determine the pattern of luteal activity in the absence of prolactin secretion, we measured blood progesterone concentration from estrus until late diestrus in female rats injected with BRC on proestrus and/or estrus at 1100 h. The initiation of the function of corpus luteum on estrus and the achievement of its full activity on diestrus 1 did not appear to be affected by BRC. By contrast the level of blood progesterone declined more rapidly on the morning of diestrus 2 in BRC-treated than in control females. The capacity for autonomous progesterone secretion by corpus luteum of the cycle was discussed in the light of previous and present observations.

Animals↗
PubMed1984

Progesterone secretion by luteinized unruptured follicles in mature female rats.

The ability of luteinized unruptured follicles (LUF) to display luteal activity was investigated in mature female rats. Previous findings in our laboratory showed that increasing doses of LH, when injected on late diestrus in 4-day cyclic rats, were capable of inducing the formation of either LUF or postovulatory corpora lutea (POCL) in a dose dependent manner. Four-day cyclers were injected on diestrus 2 at 4.30 p.m. (day 0) with 2.7 micrograms or 5.4 micrograms/100 g of an ovine LH preparation (x 2.94 NIH LH S3) and were killed at different times during the three successive days following injection. Natural 4-day cyclers were killed at corresponding times following spontaneous LH release on proestrus afternoon (day 0). Both LUF and POCL were observed in LH-treated females. LUF appeared more numerous in females given 2.7 micrograms LH than in both natural cyclers and in females injected with 5.4 micrograms LH. On day 1 during the rising phase of luteal activity serum progesterone (P) level did not differ in the three groups despite the high number of LUF in females given 2.7 micrograms LH. On day 2 at 11 a.m. lower P values were observed in both groups of LH-treated females than in natural cyclers, this corresponding to a greater proportion of LUF in the former than in the latter. On day 2, at 5 p.m. by the time of full activity of POCL in natural cyclers, P did not differ in the three groups irrespective of the relative number of ruptured or unruptured follicles. On day 3, P sharply declined in LH-treated and natural cyclers. These results suggest that LUF are capable of secreting P during a period corresponding to the duration of corpus luteum's life span in cyclic female rats.

Animals↗
PubMed1984

Prolactin and the control of cycle length in the female rat.

Bromocriptine (BRC) was injected on oestrus afternoon at 16.00 h into 5-day cyclic female rats thus causing reduced cycle length to 4-days. When injected on dioestrus 1 at 13.00 h the drug remained without effects. Blood progesterone concentration on dioestrus 1 afternoon and on dioestrus 2 morning was shown to be lower in 5-day cyclic rats given BRC than in their untreated counterparts. No changes in the rate of follicular growth were observed on dioestrus 2 afternoon in BRC injected 5-day cyclic rats. The pattern of prolactin secretion on oestrus afternoon was compared in 4- and 5-day cyclic female rats. High prolactin values were observed on early afternoon in the former and on late afternoon in the latter. The decline in progesterone secretion during the dioestrous period of the cycle was supposed to be responsible for cycle shortening in 5-day cyclic rats given BRC. It was concluded that prolactin might play a critical role in the establishment of a 5-day rhythm in the rat by controlling progesterone secretion during the dioestrous period of the cycle.

Animals↗
PubMed1982

How different procedures of blood removal affect blood progesterone concentration in the cyclic female rat.

The effects of different procedures of blood removal on blood progesterone level were studied in female rats throughout the diestrous period of estrous cycle. Unoperated, sham operated, adrenalectomized and ovariectomized females were used. The complete manipulation comprising ether anaesthesia and blood collection lasted 3-4 min. Blood removal in itself did not exceed one minute. Blood progesterone levels appeared to be higher in unoperated, sham operated and ovariectomized females bled by heart puncture or from the abdominal vena cava under ether anaesthesia than in their decapitated counterparts bled without ether anaesthesia. Adrenalectomy prevented this effect from occurring. No difference in blood progesterone concentration was noted between anaesthetized and unanesthetized decapitated unoperated females. It was concluded that some procedures of blood removal under ether anaesthesia might cause a stress-related rise in blood progesterone concentration and that ether anaesthesia was not involved.

Adrenal Glands↗
PubMed1982

Influence of blood removal under ether anaesthesia on the release of prolactin during the oestrous cycle in the rat. Involvement of the ovaries.

The aim of this work was to study the stress-like effects of blood removal under ether anaesthesia at different stages of the di-oestrus period in 4-day cyclic female rats. Blood removal by heart puncture or laparotomy and bleeding from the abdominal vena cava both under ether anaesthesia were shown to precipitously evoked prolactin release on di-oestrus I morning and on di-oestrus II afternoon. Adrenalectomy did not prevent this effect from occurring on di-oestrus I morning following either procedure of blood removal. Ovariectomy completely suppressed the stress-like effects of ether anaesthesia whereas progesterone appeared capable of restoring prolactin release under these circumstances. No prolactin positive response to ether anaesthesia was observed on di-oestrus II morning, in unoperated control females.

Adrenalectomy↗
PubMed1982

[Effect of stress on the release of LH and FSH in female rat plasma. Critical study].

The aim of this work was to study the effects of different procedures of blood removal on blood LH and FSH concentration at different stages of the diestrous period in 4-day cyclic female rats. Cardiac puncture, abdominal cava venipuncture both under ether anaesthesia and trunk blood collection were performed on diestrus 1 morning and diestrus 2 morning and afternoon. Non operated, adrenalectomized, sham adrenalectomized cyclic females and ovariectomized females were used. No changes in blood LH and FSH concentrations were observed on either diestrus 1 or diestrus 2 in the non operated and adrenalectomized cyclic females and in ovariectomized females following blood removal by heart puncture and bleeding from the abdominal vena cava, both under ether anaesthesia, as compared to decapitated animals. By contrast, these two procedures of blood removal caused an increase in blood LH concentration in sham adrenalectomized females as compared to their decapitated counterparts. Only heart puncture evoked an augmentation of blood FSH concentration under this experimental schedule. In accordance with previous studies blood LH and FSH concentrations appeared to be greater in ovariectomized than in intact cyclic females.

Adrenalectomy↗
PubMed1981

Follicular growth, ovulatory phenomena and ventromedial nucleus lesions in the rat.

Small ventromedial nucleus lesions were placed in 4-day cyclic female rats in order to determine whether cycle lengthening - previously observed in some females following such lesions - could result from changes in follicular growth. A slowing up in follicle development was observed in lesioned females with a 24-hour cycle lengthening as compared to those with a maintained 4-day cyclicity. Similarly, natural 5-day cyclers displayed slower follicular growth than natural 4-day cyclers. A rebound effect in follicular growth was observed on proestrus in either natural or VMN lesioned 5-day cyclers compared to either natural or VMN lesioned 4-day cyclers. Concomitantly blood FSH level appeared to be higher on proestrus morning and afternoon in 5-day than in 4-day cyclers. The pattern of LH release differed between natural 4-day and natural 5-day cyclers on proestrus at 17:00-19:00 h. LH release appeared to be delayed by one hour in VMN lesioned rats with 24 hour cycle lengthening as compared to natural 5-day cyclers. The duration of LH release in VMN-lesioned rats with a maintained 4-day cyclicity was shorter than in natural 4-day cyclers.

Animals↗
PubMed1980

Echographic study of follicular maturation and ovulation during the normal menstrual cycle.

Follicular development was followed by echography during 18 menstrual cycles in 10 women volunteers. Results were correlated with changes in serum hormone levels, basal body temperature curves, and cervical mucus changes. The average follicular growth as measured from the time of echographic visualization was 0.3 cm/day. The diameter of the follicle measured the day before disappearance was 2.7 +/- 0.3 cm. In all cases echography was shown to indicate accurately the time of ovulation. Given its inoffensive nature, the usefulness of echography in determining the physical event of ovulation is demonstrated. Possible applications in the surveillance of ovulation induction methods and in artificial insemination are discussed.

Adult↗
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↗
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↗