Dynamic changes in endogenous hormones from the testes and pituitary in response to a single injection of human chorionic gonadotrophin (hCG) in the Thoroughbred stallion

2010 ◽  
Vol 121 (1-2) ◽  
pp. 165-167 ◽  
Keyword(s):  
Single Injection ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Endogenous Hormones ◽  
Dynamic Changes

AUGMENTATION BY CHLORMADINONE OF THE UTERINE WEIGHT RESPONSE TO HUMAN CHORIONIC GONADOTROPHIN IN INTACT IMMATURE RATS

1965 ◽  
Vol 33 (3) ◽  
pp. 447-454
Author(s):  
M. J. K. HARPER
Keyword(s):  
Single Injection ◽  
Direct Action ◽  
Follicular Development ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Female Rats ◽  
Uterine Weight ◽  
Control Value ◽  
Orally Active ◽  
Stimulation Of

SUMMARY Administration of chlormadinone, an orally active progestational agent without significant oestrogenic activity, to intact immature female rats did not affect either ovarian or uterine weight significantly compared with controls. A single injection of human chorionic gonadotrophin (HCG) caused a 73 % increase in uterine weight in 24 hr. over the control value. This dose significantly increased ovarian weight and although it caused some stimulation of follicular development, ovulation during this time did not occur. When animals were treated with chlormadinone for 8 days, and received HCG on the 8th day, uterine weight was 170% greater than in the controls and 56% greater than with HCG alone. The uterine weight produced was similar to that found in animals treated with mestranol, a potent oestrogen, and HCG. In ovariectomized animals HCG did not affect uterine weight, while the small increase produced by chlormadinone was unaltered when HCG also was given. Mechanisms are discussed by which this augmentation of the uterine response to HCG might be produced. It seems most likely that chlormadinone administration causes storage of endogenous gonadotrophin in the pituitary, and that the exogenous gonadotrophin acts as the 'trigger' for the release of stored hormone, probably by a direct action on the hypothalamus.

The induction of puberty in rapidly-grown gilts

1984 ◽  
Vol 1984 ◽  
pp. 84-84 ◽  
Author(s):  
N. Walker ◽  
P. J. Burnett
Keyword(s):  
Single Injection ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Mating Pattern ◽  
Exogenous Hormones ◽  
Alternative Stimulus

Puberty can be stimulated from about 160 days of age by the introduction of a mature boar usually in accomodation which is novel to the gilt. The interval between stimulation and response is not always predictable and therefore does not facilitate the synchronisation of gilt matings with the mating pattern in an established sow herd. It has been reported previously that a single injection of pregnant mares’ serum gonadotrophin (PMSG) pits human chorionic gonadotrophin (HCG)* will initiate puberty. The investigations reported here concern the use of these exogenous hormones as an additional or alternative stimulus to those described above.

scholarly journals Testosterone Response of Cryptorchid and Hypophysectomized Rats to Human Chorionic Gonadotrophin (hCG) Stimulation

1985 ◽  
Vol 38 (4) ◽  
pp. 445 ◽  
Author(s):  
Y M Hodgson ◽  
DM de Kretser
Keyword(s):  
Single Injection ◽  
Serum Testosterone ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Testosterone Levels ◽  
Hypophysectomized Rats ◽  
Secondary Rise

The testosterone responses to a single injection of HCG (100 i.u.) in hypophysectomized (hypox.), cryptorchid or sham-operated rats were followed over a 5-day period. In sham-operated rats, hCG induced a biphasic rise in serum testosterone, peaks being observed at 2 and 72 h. Reduced testis weights, elevated FSH and LH levels and reduced serum testosterone levels were found after 4 weeks of cryptorchidism, but hCG stimulation resulted in a normal 2 h peak in serum testosterone. However, the secondary rise at 72 h in cryptorchid rats was significantly lower than sham-operated rats.

DIFFERENT MODES OF ACTION OF TWO ANTIOVULATORY COMPOUNDS

1964 ◽  
Vol 45 (4_Suppl) ◽  
pp. S179-S190 ◽  
Author(s):  
G. A. Overbeek ◽  
J. de Visser
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Single Injection ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
List Type ◽  
Modes Of Action ◽  
Final Maturation ◽  
Site Of Action ◽  
Lh Release

ABSTRACT Lynestrenol and 6α-methyllynestrenol were studied in rats for their respective ability to: prevent spontaneous ovulation. prevent ovulation induced by a single injection of luteinizing hormone (human chorionic gonadotrophin). to prevent ovarian hypertrophy in parabiotic (♀[unk]) rats The results warrant the following conclusions about the site of action of both substances: Lynestrenol prevents ovulation by inhibiting FSH release from the pituitary gland, so that there are no ripening follicles ready to respond to LH. 6α-Methyllynestrenol inhibits ovulation by abolishing LH-release thus preventing the final maturation and rupture of normally developing follicles.

CAPACITATION AND FERTILIZATION DURING PSEUDOPREGNANCY IN THE RABBIT

1971 ◽  
Vol 49 (4) ◽  
pp. 581-589
Author(s):  
R. H. F. HUNTER
Keyword(s):  
Embryonic Development ◽  
Fallopian Tube ◽  
Single Injection ◽  
Great Majority ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Fallopian Tubes ◽  
Rate Of Development ◽  
Additional Group ◽  
The Mean

SUMMARY Capacitation and fertilization during pseudopregnancy in the rabbit were examined on Days 4, 6, 8, 10 and 12 after mating with vasectomized males. At each of these five stages of pseudopregnancy, ovulation was induced in ten animals by a single injection of human chorionic gonadotrophin (HCG); an additional group of oestrous rabbits was similarly injected to serve as controls. Ejaculated spermatozoa were inseminated directly into the Fallopian tubes during laparotomy performed 2 h after the ovulating injection, and 15–22 h later the eggs were examined microscopically for evidence of fertilization. The mean number and range of induced ovulations decreased between Days 4 and 12 of pseudopregnancy. An overall recovery of 66% of the eggs resulting from these ovulations was achieved, the great majority being located in the Fallopian tubes. Fertilized eggs were obtained from 93% of the 60 does and 84% of the recovered eggs were fertilized. There was neither a decrease in the level of fertilization with advancing stages of pseudopregnancy, nor did the stage of pseudopregnancy influence the rate of development from pronuclear to four-celled eggs. Conspicuous among the small number of abnormal fertilizations were four dispermic pronuclear eggs and two digynic pronuclear eggs. It is concluded that after injection of HCG, complete capacitation of ejaculated spermatozoa can be achieved in the Fallopian tube between Days 4 and 12 of pseudopregnancy as rapidly as in the tube of oestrous rabbits. Furthermore, a high proportion of the eggs induced to ovulate during pseudopregnancy can be fertilized, though their potential for full embryonic development requires further study.

PROGESTERONE LEVELS AFTER INDUCTION OF OVULATION IN DIOESTROUS RATS

1980 ◽  
Vol 87 (1) ◽  
pp. 141-146 ◽  
Author(s):  
MARIKO SHIROTA ◽  
SHUJI SASAMOTO
Keyword(s):  
Single Injection ◽  
Secretory Activity ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Corpora Lutea ◽  
Induction Of Ovulation ◽  
Normal Number ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Premature Ovulation

Maximal levels of progesterone in the plasma after premature ovulation induced by either the administration of human chorionic gonadotrophin (HCG) or LH-releasing hormone (LH-RH) to dioestrous (day 0) rats were observed from 33 to 45 h but decreased 3 h earlier than after spontaneous ovulation. This suggested an earlier decline in the secretory activity of corpora lutea formed from premature ovulations than that of corpora lutea formed during a normal oestrous cycle. The next spontaneous ovulation occurred 4 days (day 5) after premature ovulation induced by LH-RH on day 0. A single s.c. injection of 2·5 μg oestradiol-17β (OE2) at 10.00 h on day 2 to these animals advanced the next spontaneous ovulation by 1 day. A normal number of oocytes was shed, indicating that earlier secretion of oestrogen on day 2 had advanced the next spontaneous ovulation. A single injection of 2·5 μg OE2 to normal 4-day cyclic rats at metoestrus failed to advance the next ovulation. An earlier decline of progesterone levels in the plasma of rats after premature ovulation as compared with spontaneous ovulation may explain the greater effectiveness of oestrogen in the former group. The progesterone surge was observed during the period of premature ovulation in both HCG- and LH-RH-treated groups. This progesterone release in the periovulatory period may be responsible for the inhibition of gonadotrophin surges on the expected day of prooestrus (day 1).

EFFECTS OF CONTINUOUS LIGHT ON THE REPRODUCTIVE CYCLE OF THE FEMALE RAT: INDUCTION OF OVULATION AND PITUITARY GONADOTROPHINS DURING PERSISTENT OESTRUS

1967 ◽  
Vol 38 (4) ◽  
pp. 389-394 ◽  
Author(s):  
K. B. SINGH ◽  
G. S. GREENWALD
Keyword(s):  
Luteinizing Hormone ◽  
Single Injection ◽  
Follicle Stimulating Hormone ◽  
Continuous Light ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
The Other ◽  
Constant Light ◽  
Female Rat ◽  
Control Light

SUMMARY The majority of rats exposed to constant light for approximately 6 weeks ovulated within 24 hr. after an injection of human chorionic gonadotrophin (HCG), but required 24–48 hr. after a single injection of progesterone. This suggests that HCG acted directly on the ovary but that progesterone acted indirectly by way of the hypothalamo-hypophysial system. Animals injected with progesterone after 6 weeks of constant light failed to ovulate after single or spaced injections of progesterone at 90 days of constant light while HCG administration was still effective. Pituitary content and concentration of luteinizing hormone (LH) in constant-light animals (duration of constant light: 45 days) were below normal pituitary levels during prooestrus and were in the range of normal oestrous values. On the other hand, follicle-stimulating hormone (FSH) content and concentration were similar to those in cyclic rats. Single injections of 1 mg. progesterone changed neither LH nor FSH concentration, despite the fact that such treatment induced ovulation. Bilateral ovariectomy increased both LH and FSH content and concentration in constant-light animals to the same extent as in control light—dark animals.

GONADOTROPHIN REQUIREMENTS FOR IMPLANTATION IN THE MOUSE

1971 ◽  
Vol 50 (1) ◽  
pp. 19-27 ◽  
Author(s):  
B. M. BINDON
Keyword(s):  
Luteinizing Hormone ◽  
Half Life ◽  
Single Injection ◽  
Follicle Stimulating Hormone ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Suckling Mice ◽  
Rat Pituitary ◽  
Pituitary Glands ◽  
Pregnant Mare Serum Gonadotrophin

SUMMARY Gonadotrophins were injected into mated hypophysectomized and suckling mice in an attempt to induce implantation. In these two classes of animal implantation is normally delayed by absence or suppression of pituitary gonadotrophin release. Antibodies raised against ovine gonadotrophins were injected into mice soon after mating in an attempt to inhibit implantation. Pregnant mare serum gonadotrophin (PMSG) was effective in inducing implantation in both hypophysectomized and in suckling mice. This may mean that a gonadotrophin with the qualities of PMSG normally initiates implantation. Alternatively, PMSG may have been effective by virtue of its long half-life rather than any special hormonal attributes. Human chorionic gonadotrophin was ineffective in both types of mouse. Mixtures of ovine follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (100 μg of each), injected daily for 3 days, were necessary to induce implantation in hypophysectomized mice. Implantation was readily induced in suckling mice by a single injection of FSH (equivalent to 12·5 μg NIH-FSH-S3) prepared from rat pituitary glands. Implantation was readily inhibited by anti-ovine LH. Anti-ovine FSH was ineffective but this did not cross-react with mouse FSH.

THE EFFECT OF A SINGLE INJECTION OF DIETHYLSTILBOESTROL OR PROGESTERONE ON THE HAMSTER OVARY

1965 ◽  
Vol 33 (1) ◽  
pp. 13-23 ◽  
Author(s):  
G. S. GREENWALD
Keyword(s):  
Anterior Pituitary ◽  
Single Injection ◽  
Follicular Development ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Oestrous Cycle ◽  
The Other ◽  
Follicular Atresia ◽  
Follicular Growth ◽  
Antral Follicles

SUMMARY A single injection of 0·25 mg. stilboestrol or 5 mg. progesterone at metoestrus (day 1) affected follicular development in the hamster ovary in different ways. Stilboestrol induced widespread follicular atresia but apparently did not interfere with the release of ovulating hormone at the end of the oestrous cycle. The atresia produced by stilboestrol appears to be mediated by changes in the levels of circulating gonadotrophin rather than by a direct effect on the ovary. This was demonstrated by injecting pregnant mare serum on day 1 of the cycle followed by stilboestrol treatment at various times thereafter. Under these circumstances the ovulation rate was only reduced below control values when stilboestrol was injected on day 1. Progesterone given on day 1 of the cycle did not interfere with the maturation of healthy Graafian follicles but acted on the terminal stages of follicular growth by blocking ovulation. After a single injection of progesterone, the life span of antral follicles was prolonged to 8–9 days. The ovulation-inhibiting effects of progesterone given on day 1 of the cycle were overcome by the injection of human chorionic gonadotrophin on day 4. Thus, progesterone blocked ovulation indirectly by preventing release of ovulating hormone from the anterior pituitary. The effects of shifting the single injection of stilboestrol or progesterone to the other days of the oestrous cycle are also considered.

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