Possible site of negative and positive feedback action of oestrogen on gonadotrophin secretion in normal women

1985 ◽  
Vol 108 (4) ◽  
pp. 440-444 ◽  
Author(s):  
Yasuhito Nagahara ◽  
Akira Miyake ◽  
Keiichi Tasaka ◽  
Yasuhiro Kawamura ◽  
Toshihiro Aono ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Direct Action ◽  
Feedback Effects ◽  
The Third ◽  
Serum Lh ◽  
Gonadotrophin Secretion ◽  
Site Of Action ◽  
The Mean ◽  
Normal Women

Abstract. For determination of the site of action of oestrogen (E) during the negative and positive feedback phases of gonadotrophin secretions, studies were made on the pituitary response to a small amount of LRH and the pulsatility of gonadotrophins after E administration in normal cycling women in the mid-follicular phase. The pituitary responses to an iv bolus of 2.5 μg of synthetic LRH were evaluated by measuring serum LH and FSH 2 h before and 8 h after administration of 20 mg of conjugated E (Premarin). In the next cycle, the pituitary responses to a same dose of LRH were also observed 2 h before and 56 h after E injection. The mean levels of serum LH and FSH and the peak responses to LRH were significantly (P < 0.05) decreased 8 h after E injection, but were significantly (P < 0.05) increased 56 h after E administration. In the third cycle, the pulsatility of gonadotrophins was evaluated by measuring serum LH and FSH every 15 min for 180 min before and 8 h and 56 h after E injection. The pulse frequencies of gonadotrophins were not significantly different before and 8 h and 56 h after E injection. The amplitudes of pulses 56 h after Premarin injection were significantly higher than those before the injection. These findings suggest that the negative and positive feedback effects of E on gonadotrophin secretion may be caused, in part, by its direct action on the pituitary response to LRH.

POSITIVE FEEDBACK ACTION OF OESTRADIOL ON GONADOTROPHIN RELEASE IN 15 DAY OLD FEMALE RATS

1977 ◽  
Vol 86 (2) ◽  
pp. 263-272 ◽  
Author(s):  
J. Kronibus ◽  
W. Wuttke
Keyword(s):  
Column Chromatography ◽  
Positive Feedback ◽  
Female Rats ◽  
Intact Control ◽  
Partial Separation ◽  
Ovx Rats ◽  
Serum Lh ◽  
The Mean ◽  
Intact Rats

ABSTRACT Female rats were ovariectomized (ovx), adrenalectomized (adx) or both (adx-ovx) on day 8 after birth. The serum gonadotrophin concentrations on day 15 were higher in ovx and adx-ovx rats than in sham-operated or untreated controls of the same age. Intact animals on day 15 had higher LH and FSH levels compared with adult, dioestrous levels, and a number of LH peaks were observed. After partial separation of oestradiol (LH 20 column chromatography) from other lipid substances which interfere with the radioimmunoassay for oestradiol, levels of oestradiol were undetectable in ovx and in adx-ovx animals on day 15 but concentrations were relatively high in intact or adx rats. To test whether the high gonadotrophin concentrations in 15-day-old intact rats were due to a positive feedback action of oestradiol, silastic tubes containing different amounts of oestradiol were implanted on day 8 at the time of adrenalectomy and ovariectomy. The mean serum LH and FSH concentrations were increased on day 15 in those animals in which silastic tube implantation resulted in physiological oestradiol levels. These elevated gonadotrophin values were due to a number of peak levels. Injection of 600 μg progesterone on day 15, 8 h before decapitation resulted in high FSH levels in all the implanted animals, whereas LH levels were still variable from one animal to another. This situation is very similar to that in intact control rats and it is concluded that the hypothalamo-pituitary axis in 15-day-old female rats reacts to an oestrogenic stimulus followed by a progestational reaction as does the adult "gonadostat". This would account for the premature, pre-ovulatory type of LH peaks.

Starvation induced anoestrus: effect of chronic food restriction on body weight, its influence on oestrous cycle and gonadotrophin secretion in rats

1983 ◽  
Vol 104 (4) ◽  
pp. 402-409 ◽  
Author(s):  
U. A. Knuth ◽  
H. G. Friesen
Keyword(s):  
Weight Loss ◽  
Body Weight ◽  
Food Restriction ◽  
Oestrous Cycle ◽  
The Third ◽  
Serum Lh ◽  
Gonadotrophin Secretion ◽  
Normal Chow ◽  
Chronic Food Restriction ◽  
Intact Rats

Abstract. To test the effect of chronic starvartion on gonadotrophin secretion and oestrous cycles, rats were fed 50% of their normal chow consumption for 16 days. This caused an increasing rate of anoestrus which became significant during the third expected cycle (6 of 10 rats, P < 0.02) and increased to 8 of 10 rats (P < 0.0001) between day 12 and 16. The accompanying weight loss was around 13 and 17%, respectively. Pituitary weights in intact rats killed on dioestrus became significantly different after 8 days of chow reduction (12.8 ± 0.2 vs 11.3 ±0.4 mg, P < 0.02) with further reductions in groups killed after 12 and 16 days. At this time dioestrous serum FSH levels were significantly inceased in starved rats (112 ± 16 vs 161 ± 13 ng/ml, P < 0.01), while serum LH levels decreased significantly after 12 days (25.0 ± 3.4 vs 13.1 ± 8.8 ng/ml, P < 0.001). Starvation decreased the LH response to LRH administration compared to pro-oestrous controls (1934 ± 672 vs 289 ± 39 ng/ml, P < 0.05), whereas the FSH response was not impaired (457 ± 91 vs 336 ± 54 ng/ml, P > 0.05). In contrast to this pituitary content of LH was similar in both groups, while FSH content was significantly higher in starved animals (13.6 ± 1.7 vs 19.8 ± 1.2 μg, P < 0.01). Chronic starvation immediately after ovariectomy did not affect the post-castrational rise of gonadotrophins. However, LRH administration caused higher serum FSH levels in starved rats (1540 ± 91 vs 1833 ± 90 ng/ml, P < 0.05), whereas LH values did not differ (908 ± 192 vs 721 ± 153 ng/ml, P> 0.05). Gonadotrophin content per pituitary in castrated rats after 16 days of starvation was unchanged.

Restoration of oestrogen-positive feedback effect on LH release in women with prolactinoma by transsphenoidal surgery

1982 ◽  
Vol 100 (4) ◽  
pp. 492-498 ◽  
Author(s):  
Koji Koike ◽  
Toshihiro Aono ◽  
Hirohisa Tsutsumi ◽  
Akira Miyake ◽  
Keiichi Kurachi
Keyword(s):  
Surgical Treatment ◽  
Positive Feedback ◽  
Transsphenoidal Surgery ◽  
Feedback Effect ◽  
Serum Prolactin ◽  
Luteinizing Hormone Releasing Hormone ◽  
Serum Lh ◽  
Lh Release ◽  
The Mean ◽  
Positive Feedback Effect

Abstract. The effect of hyperprolactinaemia on the hypothalamo-pituitary axis was assessed by iv injection of 100 μg luteinizing hormone releasing hormone (LRH) in 7 women with prolactinoma before and 3 months after normalization of the Prl level by transsphenoidal surgery. A dose of 20 mg of conjugated oestrogen (Premarin®) was also injected iv into patients with prolactinoma before and 4 months after surgery, and the serum LH levels were determined serially for 120 h after the injection. Surgical treatment caused significant reduction of the mean (± se) serum prolactin (Prl) level from 123.3 ± 7.8 to 19.4 ± 5.6 ng/ml. But the differences in the basal levels of LH (11.3 ± 2.2 to 8.6 ± 1.5 mIU/ml), FSH (8.3 ± 2.4 to 10.6 ± 3.7 mIU/ml) and oestradiol (26.6 ± 8.6 to 37.5 ± 5.5 pg/ml) before and 4 months after surgery were not significant. An exaggerated LH response to LRH in untreated prolactinoma patients was also observed after surgical treatment. After surgical treatment, patients showed LH release with a peak between 48 and 72 h after the injection of Premarin, whereas before treatment they did not show any LH discharge. The mean percent increase in LH between 48 and 72 h was also significantly higher after operation than before operation. These results suggest that the hyperprolactinaemia in prolactinoma patients may cause an impaired positive feedback effect of oestrogen on LH release and that this derangement can be reversed by reduction of the Prl level by adenomectomy.

Determination of optimal time for mating by artificial insemination with chilled semen using luteinizing hormone surge as an indicator in beagles

1999 ◽  
Vol 35 (4) ◽  
pp. 348-352 ◽  
Author(s):  
T Nishiyama ◽  
T Kinugasa ◽  
T Kimura ◽  
G Watanabe ◽  
K Taya ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Artificial Insemination ◽  
Sperm Count ◽  
Egg Yolk ◽  
Optimal Time ◽  
Lh Surge ◽  
Serum Lh ◽  
The Mean ◽  
Luteinizing Hormone Surge

Artificial insemination (AI) was conducted using the second fraction of semen, which was collected from 15 male dogs, diluted to a total sperm count of 100x10(6) for each insemination with egg-yolk Tris (eyT) citrate acid buffer and incubated at 4 degrees C for 48 hours. Luteinizing hormone (LH) surge was detected to determine the optimal time for mating using canine LH assay kits. Artificial insemination using 100x10(6) sperm was performed on the fourth and sixth days or the fifth and seventh days after the LH surge. The conception rates were 33% (4/12) and 89% (8/9), respectively; the whelping rates also showed similar results. Serum LH and follicle stimulating hormone (FSH) concentrations were measured in nine dogs, and the mean LH concentration (+/- standard deviation) at LH surge was 15.77+/-7.66 ng/ml. The time of the LH surge detected by the canine LH assay kit was very similar to that measured by radioimmunoassay (RIA).

A comparison of the effects of gonadal steroids on naloxone-induced LH secretion in gonadectomized rats

1986 ◽  
Vol 110 (2) ◽  
pp. 327-334 ◽  
Author(s):  
G. M. Spencer ◽  
S. A. Whitehead
Keyword(s):  
Inhibitory Effect ◽  
Gonadal Steroids ◽  
Ovariectomized Rats ◽  
Endogenous Opioid ◽  
Feedback Effects ◽  
Serum Lh ◽  
Gonadotrophin Secretion ◽  
Endogenous Opioid Systems ◽  
Hypothalamic Pituitary Axis ◽  
Lh Secretion

ABSTRACT The effects of the opiate antagonist naloxone on serum LH concentrations was investigated in gonadectomized rats given different regimes of steroid pretreatment. Two injections of testosterone given 48 and 24 h before naloxone treatment failed to reinstate LH responses to this drug in castrated rats while subcutaneous testosterone-filled silicone elastomer capsules implanted for a week were effective in this respect. Injections of oestrogen, oestrogen plus progesterone or progesterone alone all restored LH responses to naloxone in ovariectomized rats when given 48 and/or 24 h before drug treatment, although the magnitude of these responses varied according to the precise steroid treatments. The hypothalamic-pituitary axis was also responsive to naloxone just before the progesterone-induced LH surge in oestrogen-primed ovariectomized rats. Results show that gonadal steroids are permissive to the effects of opiate drugs, but they suggest that endogenous opioid systems do not necessarily mediate the negative feedback effects of steroids. Some other factor(s), as yet unidentified in the rat, may control the opioid modulation of gonadotrophin secretion or exert an independent inhibitory effect on gonadotrophin release. J. Endocr. (1986) 110, 327–334

Influence of Humidy on Radon Volume Activity on Lands

2020 ◽  
Vol 838 ◽  
pp. 111-117
Author(s):  
Jana Bouchalova ◽  
Helena Raclavská ◽  
Vendula Klimantová
Keyword(s):  
Middle Class ◽  
Soil Profile ◽  
Gas Permeability ◽  
Soil Samples ◽  
Soil Gas ◽  
Volume Activity ◽  
The Third ◽  
The Mean ◽  
The Given

The research is primarily focused on the determination of humidity on radon volume activity in different soil gas permeabilities in a given land. The research also included the detrermination of the radon index in the given land. The mean concentrations of radon in soil gas during the drought ranged from 15.9 - 24.1 kBq/m3 and in the precipitation period 16.3 - 26.7 kBq/m3. The first area was characterized by low gas permeability of soils, where a low radon index was determined during the dry season and a medium radon index was determined in the precipitation period. The second area, the medium gas permeability of the soils was determined from the analysis of the collected soil samples. The values of the third quartile in both cases measurements of radon volume activity in soil gas fall into the middle class of radon index. The third location would be determined by high gas permeability of soils. The radon index of the given land during the drought was determined as the medium, as in the case of measurement of radon volume activity in soil gas in the period with added moisture in the soil profile. The analysis confirmed the effect of moisture on the volume activity of radon.

scholarly journals Ultrasound Determination of Gestational Age Using Placental Thickness in Female Dogs: An Experimental Study

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
André Luiz Louzada Maldonado ◽  
Edward Araujo Júnior ◽  
Débora Sartori Mendonça ◽  
Luciano Marcondes Machado Nardozza ◽  
Antonio Fernandes Moron ◽  
...  
Keyword(s):  
Experimental Study ◽  
Body Weight ◽  
Gestational Age ◽  
Thickness Measurement ◽  
Mean Values ◽  
The Third ◽  
Large Size ◽  
The Mean ◽  
Placental Thickness

Objective. To verify if the placental thickness allows determining the gestational age, evaluating the correlation between the referred gestational age with the studied one, and the accuracy of the placental thickness measurement (biometry) with fetal morphologic parameters in bitches.Methods. The placental thickness of 336 bitches of diverse breeds was evaluated. Bitches were divided in three groups by body weight: small, medium, and big large size. The gestations pregnancies were evaluated by ultrasound from the third week of gestation. An analysis was performed between the mean values of the gestational age obtained of placental thickness by adjustment of curves and the reported gestational age. Student'st-test was applied to compare the mean of reported and placental thickness gestational age. Significance was defined asP<0.05.Results. A positive and statistically significant correlation exists between the placental thickness and gestational age. The expression that presents the best correlation coefficient and explanation was thickness of placenta = 0.021xgestational age −0.314.Conclusion. It is possible to determine the gestational age in relation to the placental thickness measured by ultrasound in bitches with a satisfactory accuracy in relation to fetal morphologic parameters as gestational vesicle, ribs, or kidneys.

Chemical Determination of Niacinamide in Multivitamin Preparations

1968 ◽  
Vol 51 (4) ◽  
pp. 828-834
Author(s):  
Omer Pelletier
Keyword(s):  
Coefficient Of Variation ◽  
Microbiological Method ◽  
Chemical Methods ◽  
Mean Values ◽  
The Third ◽  
Collaborative Studies ◽  
Chemical Determination ◽  
Aoac Method ◽  
The Mean

Abstract The AOAC method and the Pelletier and Campbell method for the assay of niacinamide in multivitamin preparations were compared in two collaborative studies. In the first study, three multivitamin sirup preparations were analyzed by six laboratories; the proposed method gave higher results for two preparations but lower results for the third. In the second study, four types of multivitamin preparations were analyzed; twelve laboratories reported on the chemical methods and three laboratories on the microbiological method. There was no difference in the mean values for two types of samples, but one sample of multivitamin tablets yielded mean values about 5% lower by the proposed method, suggesting the presence of a trace of niacin; with a multivitamin and mineral sirup the proposed method gave values about 6% higher than the AOAC method and 3% lower than the microbiological assay. The coefficient of variation for any sample in any laboratory by the AOAC method was about 14% in the first study and 1 1% in the second study; by the proposed method it was 4 and 9% in the same respective studies. It is recommended that the present AOAC method be modified by adjusting the pH of sample hydrolysates in the range of 2.5—4.5 instead of 7—9 to reduce the absorhance of the blanks, and that the method of Pelletier and Campbell be adopted as official, first action.

FAILURE OF HISTAMINE TO INDUCE THE RELEASE OF LUTEINIZING HORMONE IN CASTRATED RATS PRIMED WITH SEX STEROIDS

1978 ◽  
Vol 78 (3) ◽  
pp. 447-448 ◽  
Author(s):  
A. O. DONOSO ◽  
A. M. BANZAN
Keyword(s):  
Luteinizing Hormone ◽  
Positive Feedback ◽  
Sex Steroids ◽  
Third Ventricle ◽  
Male Rats ◽  
Intraventricular Injection ◽  
Mediobasal Hypothalamus ◽  
Feedback Effects ◽  
The Third

Instituto de Investigaciones Cerebrales, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina (Received 10 March 1978) Injection of histamine into the third ventricle causes the release of luteinizing hormone (LH) in ovariectomized, steroid-primed and pro-oestrous rats (Donoso, Banzan & Borzino, 1976; Donoso, 1978). In oestrous rabbits, intraventricular injection of large doses of histamine or injection of histamine into the mediobasal hypothalamus induces ovulation and secretion of progesterone by the ovaries (Sawyer, 1955; Endröczi & Hilliard, 1965). However, histamine has no effect on the concentration of LH in the plasma of male rats (Donoso & Banzan, 1976). Together, these results suggest that histamine is able to induce the release of LH both before ovulation and in the presence of an adequate hormonal background. The positive feedback effects of oestradiol and progesterone on the release of gonadotrophins are absent in male rats. Injection of oestradiol, progesterone or testosterone into steroid-primed

Assessment of the negative and positive feedback effects of administered oestrogen on gonadotrophin release in patients with anorexia nervosa

1977 ◽  
Vol 7 (3) ◽  
pp. 397-405 ◽  
Author(s):  
A. Wakeling ◽  
C. J. Beardwood ◽  
V. A. deSouza
Keyword(s):  
Anorexia Nervosa ◽  
Negative Feedback ◽  
Positive Feedback ◽  
Complete Response ◽  
Normal Weight ◽  
Feedback Effects ◽  
Serum Lh ◽  
Definite Sequence ◽  
Hypothalamic Pituitary Axis ◽  
Lh Release

SynopsisThe capacity of the hypothalamic–pituitary axis to respond with changes in LH release to the negative and positive feedback effects of oestrogen was assessed in 19 patients with anorexia nervosa at different stages of the illness. Ethinyl oestradiol, 200 μg daily for 3 days, was administered and serial estimations of serum LH were carried out during and after the course of oestrogen.In patients with anorexia nervosa tested when markedly underweight, negative feedback effects of oestrogen were demonstrated in those patients with detectable levels of LH. None of the patients demonstrated positive feedback release of LH to the oestrogen stimulus.After the resumption of a more normal weight, basal LH levels were higher and negative feedback effects of oestrogen were observed in 11 out of 12 patients. The complete response to oestrogen with a subsequent positive release of LH to the oestrogen stimulus was shown by only 3 patients. Two of these 3 patients maintained a normal weight during the subsequent 6 months and both resumed regular menstruation shortly after the test. Three additional patients who had shown only negative feedback effects of oestrogen on LH release similarly maintained a normal weight and only 1 of them resumed menstruation, starting 3 months after the oestrogen test.It was concluded that in recovery from anorexia nervosa there is a return of normal hypothalamicpituitary–gonadal activity in a definite sequence with recovery of the hypothalamus to respond normally to the negative feedback effects of oestrogen followed by return of the positive feedback capacity between oestrogen and LH which allows menstruation to resume. The resumption of normal hypothalamic–pituitary function is clearly dependent in part upon correction of the malnutrition. However, after correction of the malnutrition some patients fail to menstruate, and this appears to be determined by a continuing impairment of the hypothalamus to respond normally to the feedback effects of oestrogen upon gonadotrophin release.

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