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Biomedical subjects

J Roos

Publications and source records attributed to J Roos.

At least 109 records · Page 6Linked to original sources
PubMed1976

Hormonal mechanisms involved in the control of oestrous cycle duration by the odour of urine in the rat.

The mechanisms involved in the reduced cycle duration following exposure to the odour of urine were studied in natural and experimental 5-day cyclic female Wistar rats. A decrease in the rate of ovarian progesterone secretion from the morning of dioestrus I to that of dioestrus II was observed in females whose cycle duration was reduced from 5 to 4 days following exposure to the odour of rat urine. No decrease in ovarian progesterone secretion occurred in females maintaining a 5-day cyclicity despite exposure to this odour. An increase in follicular growth was noted in females with cycle duration reduced from 5 to 4 days, when compared with those maintaining a 5-day rhythm. As a result of exposure to the odour of urine no reduced cycle duration occurred in females with cycles lengthened from 4 to 5 days as a result of progesterone injection on dioestrus I of 4-day cycles. Hence the decrease in ovarian progesterone secretion, induced by exposure to the odour of urine, is considered to cause a speeding up in follicular growth, thereby reducing oestrous cycle duration in 5-day cyclic rats.

Animals↗
PubMed1976

Studies on the mode of action of clomiphene citrate.

In order to further investigate the mode of action of clomiphene citrate, 5 oophorectomized women in the age range 28 to 41 years were followed with weekly determinations of serum FSH and LH for 20 weeks after the operation. They received no treatment during the first 4 weeks but during the next 16 weeks they were given estradiol 2 mg X 2 daily orally, and from the 12th to the 16th week in addition clomiphene citrate 50 mgX2 daily. The high level of FSH after the oophorectomy decreased gradually during the treatment with estradiol alone, but this effect was partly neutralized by clomiphene citrate, as we observed a significant increase in FSH within 1 week of initiating treatment with clomiphene citrate. On the other hand, we did not find any significant changes in FSH within 4 weeks after treatment with clomiphene citrate was discontinued. The high level of LH after oophorectomy did not show any significant changes during the whole treatment period. It is concluded that clomiphene citrate primarily stimulated FSH secretion, most probably by a competition with estradiol for the receptor sites in the hypothalamus or the pituitary. In addition, it is concluded that clomiphene citrate has a prolonged effect, probably because of a tight binding to the receptor sites.

Administration, Oral↗
PubMed1976

[Demonstration of a critical period of ovarian activity in the control of early receptivity induced by estrogen in the female rat with 4-day cycles].

A significant decrease in early receptivity during the night from dioestrus II to prooestrus was observed in estrogen-treated 4-day cyclic rats following bilateral ovariectomy on dioestrus II at 4-5 p.m. Early receptivity appeared then to be dependent on the presence of ovary at this stage of the cycle. The mechanism whereby the adrenals may compensate for the ovaries when removed on dioestrus I, at 10-11 a. m. (Roos et al. 1973), was not observed in the present experimental conditions.

Adrenal Cortex↗
PubMed1975

Luteinizing and ovulatory action of oestradiol in the pregnant rat.

Oestradiol injection on Day 10 of pregnancy in rats, resulted in either ovulation or luteinization in 50% of cases on Day 12. Cytological data showed that the number of pituitary LH cells decreased significantly on Day 11 in all oestradiol-treated animals whether responsive or not to oestrogen by ovarian modifications, while the number of pituitary FSH cells only decreased significantly in females with characteristic ovarian signs of preovulation. Bioassay of pituitary FSH confirmed the cytological data. It is concluded that ovulation and luteinization only occurred in the pregnant rat when oestradiol triggered off a synchronous release of LH and FSH.

Animals↗
PubMed1975

LH and FSH in serum after intramuscular administration of LH/FSH-releasing hormone in normal and hypogonadal men.

The increase in serum concentrations of LH and FSH after intramuscular administration of LH/FSH-RH was investigated in normal and hypogonadotrophic hypogonadal males. LH and FSH were measured by specific radio-immunoassays. To evaluate the appropriate dose of LH/FSH-RH for intramuscular administration different doses were administered and with 200 mu g an increase in LH and FSH was found comparable to the results obtained by other investigators using intravenous administration. After the initial studies a simple test including two determinations before LH/FSH-RH administration and one 60 min and 120 min after administration was developed and used in all cases. In 12 normal males a significant increase in the serum concentration of both LH and FSH was found averaging 381% and 148% respectively 60 min after 200 mu g LH/FSH-RH with a slight decrease in LH but not in FSH after 120 min. A positive response similar to that in normal men was observed in 11 hypogonadotrophic hypogonadal patients presenting different clinical pictures. This indicates that in all these patients the hypogonadotrophic state was due to a hypothalamic defect and not to a hypophyseal disorder.

17-Ketosteroids↗
PubMed1975

[New data on the "critical period" of the luteinizing action of estradiol benzoate in female rats].

The luteinizing action of oestradiol benzoate (OB) has been studied in 4-day cyclic female Wistar rats submitted to a dose of 10 mug on the morning of dioestrus I at 10-11 a.m. In a first experimental series a blockage of luteinization was observed in females injected with pentobarbital (PB) either on dioestrus I at 11 a.m. and 5 p.m. respectively or on dioestrus II at 1:30 p.m. In the second series the blockage of luteinization only occured in females injected with PB on dioestrus II at 1:30 p.m. Early mating during the night following dioestrus II overcame this action of PB. The luteinizing effects of OB were therefore concluded to be dependent on the activation on the afternoon of dioestrus II, of the nervous hypothalamic structures. They were also shown to depend on the sensitivity to PB and/or to OB, on the day of dioestrus I, of the hypothalamo-pituitary system.

Animals↗