scholarly journals Effects of Oestradiol on Plasma Concentrations of Luteinizing Hormone in Ovariectomized Ewes with Clover Disease

1983 ◽  
Vol 36 (3) ◽  
pp. 295 ◽  
Author(s):  
NR Adams ◽  
GB Martin
Keyword(s):  
Luteinizing Hormone ◽  
Breeding Season ◽  
Intravenous Injection ◽  
Intramuscular Injection ◽  
Prolonged Exposure ◽  
Plasma Concentrations ◽  
Oestradiol Benzoate ◽  
Baseline Levels ◽  
The Difference ◽  
Clover Pasture

The effects of oestradiol on plasma luteinizing hormone (LH) concentrations were examined in 15 ovariectomized control ewes and 15 similar ewes with permanent infertility after prolonged grazing on oestrogenic clover pasture ('clover disease'). Before treatment, the plasma concentrations of LH were similar in the control and affected ewes. After intravenous injection with 40 pg oestradiol-I 7 p during the anoestrous season, the decline in LH concentration was greater in the clover-affected ewes and the subsequent elevation above original baseline levels was smaller. After intramuscular injection with 15 or 30 pg oestradiol benzoate during the normal breeding season, fewer clover-affected ewes showed a surge of LH, and the response was both reduced and retarded. This difference between the two groups has not been observed in studies on intact ewes, and it is suggested that in intact ewes the difference is masked by a greater tonic LH activity in affected ewes. The results of the present study are consistent with the hypothesis that prolonged exposure to oestrogenic pasture has a differentiating, or 'androgenizing' effect on the adult ewe.

Effect of various anaesthetics on resting plasma concentrations of luteinizing hormone, follicle-stimulating hormone and prolactin in ovariectomized ewes

1983 ◽  
Vol 98 (1) ◽  
pp. 79-89 ◽  
Author(s):  
I. J. Clarke ◽  
B. W. Doughton
Keyword(s):  
Seasonal Variation ◽  
Luteinizing Hormone ◽  
Breeding Season ◽  
Follicle Stimulating Hormone ◽  
Plasma Concentrations ◽  
Pulse Amplitude ◽  
Experimental Series ◽  
Plasma Prolactin ◽  
Pulsatile Secretion ◽  
Induction Of Anaesthesia

Effects of various anaesthetics on plasma LH, FSH and prolactin levels were studied in ovariectomized ewes. In the first experimental series, conducted between June and November (late breeding season, early anoestrous season), the following treatments were given: saline (i.v.) (n = 7); single thiopentone injection (i.v.) (n = 4); induction of anaesthesia for 2 h with thiopentone (n = 5), ketamine/thiopentone mixture (n = 6), Alphathesin (n = 6) or induction with thiopentone and maintenance with halothane (n = 6). The major findings were: (1) halothane anaesthesia reduced mean plasma LH levels by preventing pulsatile secretion of LH; (2) Alphathesin had the least effect on tonic LH concentration; (3) a single thiopentone injection did not affect LH levels; (4) continuous thiopentone anaesthesia increased LH pulse amplitude; (5) plasma FSH concentration was not affected by any of the treatments; (6) ketamine/thiopentone-induced and Alphathesin-induced anaesthesia increased plasma prolactin levels. In a second experimental series four ovariectomized ewes were anaesthetized with thiopentone for 3 h in January. In contrast to the results obtained with thiopentone in August, treatment in January reduced plasma LH pulse amplitude and mean plasma LH levels. These latter results support the hypothesis that there may be seasonal variation in responses to barbiturate anaesthesia.

RELEASE OF GONADOTROPHIN IN OVARIECTOMIZED MICE AFTER EXPOSURE TO MALES

1969 ◽  
Vol 44 (3) ◽  
pp. 293-297 ◽  
Author(s):  
F. H. BRONSON ◽  
C. DESJARDINS
Keyword(s):  
Luteinizing Hormone ◽  
Follicle Stimulating Hormone ◽  
Plasma Concentrations ◽  
Neural Pathway ◽  
Ovariectomized Mice ◽  
Oestradiol Benzoate ◽  
Stimulating Hormone

SUMMARY Gonadectomized female C57BL/6J mice were caged with males to determine the effect of male stimuli on release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Concentrations of hypophysial and plasma FSH were significantly higher after 3 days of exposure to males when compared with controls maintained in the absence of a male. Hypophysial and plasma concentrations of LH were also higher in females caged with males, but not significantly so. Ovariectomized females were given 0·01 μg. oestradiol benzoate daily for 4 days in a second experiment and the effect of cohabitation re-evaluated. There were no significant effects of exposure to males on either FSH or LH after the oestradiol injections. Therefore the presence of males enhances synthesis and release of FSH in gonadectomized females. In addition, the results of the second experiment suggest that oestrogen interferes with this response in some way, possibly blocking the neural pathway utilized by male stimuli.

OESTRADIOL-17α AND PITUITARY RESPONSIVENESS TO LUTEINIZING HORMONE RELEASING FACTOR IN THE RAT: A STUDY USING RECTANGULAR PULSES OF OESTRADIOL-17β MONITORED BY NON-CHROMATOGRAPHIC RADIOIMMUNOASSAY

1977 ◽  
Vol 73 (3) ◽  
pp. 441-453 ◽  
Author(s):  
S. R. HENDERSON ◽  
CHRISTINE BAKER ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
Oestrous Cycle ◽  
Facilitatory Effect ◽  
Oestradiol Benzoate ◽  
High Doses ◽  
Plasma Oestradiol

SUMMARY Plasma concentrations of oestradiol-17β were measured by a non-chromatographic radioimmunoassay during the oestrous cycle, after the s.c. injection of 2·5 or 10 pg oestradiol benzoate (OB), or the s.c. implantation of Silastic capsules containing crystalline oestradiol-17β. The profile of endogenous plasma oestradiol-17β concentrations was similar to that reported by other workers, and lay between the concentrations produced by the low and high doses of OB. The rectangular pulses of increased plasma oestradiol concentrations, produced during the period of implantation of the Silastic capsules, were used to determine the time taken for oestradiol-17β to exert its facilitatory effect on the gonadotrophin response to LH-releasing factor (RF). In animals ovariectomized at dioestrus, oestradiol, at concentrations similar to those reached during the peak of the spontaneous surge, first reduced the LH response. However, after 7 h, responsiveness increased significantly to reach a peak at 12 h. The FSH response was also greatest 12 h after ovariectomy. In animals ovariectomized at metoestrus the effect of oestradiol on the LH response was significantly less than in rats ovariectomized at dioestrus, and the FSH responses were lower than those in animals bearing empty capsules and examined at the same time after ovariectomy. These findings together with the effects of long-term exposure to sodium pentobarbitone are considered with respect to the possible mechanisms, including the priming effect of LH-RF, which may produce increased pituitary responsiveness after ovariectomy and exposure to oestrogen.

A PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING FACTOR ON THE ANTERIOR PITUITARY GLAND IN THE FEMALE RAT

1974 ◽  
Vol 62 (3) ◽  
pp. 573-588 ◽  
Author(s):  
M. S. AIYER ◽  
SHARON A. CHIAPPA ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
External Jugular Vein ◽  
Anterior Pituitary Gland ◽  
Female Rat ◽  
Oestradiol Benzoate ◽  
Plasma Oestradiol

SUMMARY The possibility that luteinizing hormone releasing factor (LH-RF) not only stimulates the secretion of luteinizing hormone (LH) but also has the ability to prime the anterior pituitary gland so that further exposure to LH-RF enhances the responsiveness of the gonadotrophs has been investigated. The effect of two successive i.v. injections of the same dose of LH-RF (50 ng/100 g body weight) on the concentration of LH in plasma was determined in rats anaesthetized with sodium pentobarbitone. Blood samples were collected from the external jugular vein immediately before and at frequent intervals after the injections of LH-RF, and plasma concentrations of LH and, in some samples, follicle-stimulating hormone (FSH) were measured by radioimmunoassay. In rats anaesthetized with sodium pentobarbitone at 13.30 h of pro-oestrus and injected i.v. with two successive doses of LH-RF, separated by an interval of 30, 60, 120 or 240 min, the LH response to the second injection was significantly greater than that to the first. The LH response was greatest when the two doses were separated by an interval of 60 min. The FSH response to the second injection of LH-RF given 60 min after the first was not significantly different from that to the first injection. Compared with pro-oestrus, the priming effect of LH-RF was much less at metoestrus and dioestrus, and could not be demonstrated at oestrus. Ovariectomy on the morning of dioestrus reduced the LH responses to the first and second injections of LH-RF given 60 min apart on the afternoon of pro-oestrus, an effect which was partially reversed by administration of oestradiol benzoate shortly after ovariectomy. These findings together with the fact that administration of oestradiol benzoate at metoestrus increased the magnitude of the priming effect of LH-RF at dioestrus suggest that the response at pro-oestrus is dependent upon the rise in plasma oestradiol-17β which reaches a peak on the morning of pro-oestrus. Although oestrogen plays an important role in determining the magnitude of the priming effect of LH-RF, it appears that none of the steroids secreted by either the ovaries or the adrenal glands mediates this effect since the profile and magnitude of the LH responses to the two doses of LH-RF injected at pro-oestrus into rats adrenalectomized and ovariectomized before the first injection of LH-RF were comparable to those in control animals. The possible role which the priming effect of LH-RF may play in the development of the preovulatory surge of LH in the rat and man is discussed.

The effect of stage of breeding season or pre-mating oestrogen and progestagen therapy on fertility in ewe lambs

1994 ◽  
Vol 59 (3) ◽  
pp. 429-434 ◽  
Author(s):  
N. F. G. Beck ◽  
M. C. G. Davies
Keyword(s):  
Breeding Season ◽  
Corpora Lutea ◽  
Oestrogen Therapy ◽  
Crown Rump Length ◽  
Ewe Lambs ◽  
Oestradiol Benzoate

AbstractAn investigation was conducted to determine the effect of mating at puberty or third oestrus or after pre-mating oestrogen and progestagen therapy, designed to mimic the changes that occur in plasma oestrogen and progesterone concentrations during the 1st, 2nd or 3rd oestrous cycles, on fertility in ewe lambs. Twenty-five ewe lambs were mated at puberty on mean date of 18 October and 21 were mated at third oestrus on 3 December. Of these, 28% and 81% of animals mated at puberty and third oestrus lambed, respectively (P < 0·05). A similar number of ewe lambs were mated within 24 h of ram introduction in the groups given one, two or three consecutive applications oestrogen and progestagen (25 μg oestradiol benzoate followed 48 h later by a progestagen pessary left in situ for days). Of the 43 corpora lutea, 21 were represented by viable embryos in the 37 animals holding to service after one application compared with 34 out of 46 corpora lutea in 40 animals given three applications (P < 0·05). Furthermore, embryo crown-rump length, embryo weight and amniotic sac width was greater (P < 0·05), on day of pregnancy, in animals given one compared with three applications of oestrogen and progestagen. These results demonstrate that fertility is improved in ewe lambs mated on third oestrus or after progestagen and oestrogen therapy designed to simulate three oestrous cycles.

Pharmacokinetics and Tissue Residues of Sulfathiazole and Sulfamethazine in Pigs

1994 ◽  
Vol 57 (9) ◽  
pp. 796-801 ◽  
Author(s):  
LIEVE S. G. VAN POUCKE ◽  
CARLOS H. VAN PETEGHEM
Keyword(s):  
Intravenous Injection ◽  
Half Life ◽  
Intramuscular Injection ◽  
Compartment Model ◽  
Absolute Bioavailability ◽  
Pharmacokinetic Parameters ◽  
Tissue Concentrations ◽  
Single Intravenous Injection ◽  
The Individual ◽  
Residue Study

The plasma pharmacokinetics and tissue penetration of sulfathiazole (ST) and sulfamethazine (SM) after intravenous and intramuscular injection in pigs were studied. Following a single intravenous dose of 40 mg ST/kg of bodyweight or 80 mg SM/kg of bodyweight, the plasma ST and SM concentrations were best fitted to a two-compartment model. The areas under the curve were 447 ± 39 and 1485 ± 41 mg/h/L, clearances were 0.090 ± 0.007 and 0.054 ± 0.001 L/kg/h, volumes of distribution were 1.16 ± 0.16 and 0.77 ± 0.06 L/kg, half-lifes in distribution phase were l.18 ± 0.57 and 0.23 ± 0.16 h and half-lifes in eliminations phase were 9.0 ± l.6 and 9.8 ± 0.6 h. When the two compounds were administered simultaneously as a single intravenous injection, the pharmacokinetic parameters for ST were not significantly different. The values for SM show statistical differences for some important parameters: α, β and the AUC0–&gt;∞ were significantly decreased and t1/2α, Vd and CIB were significantly increased. It can be concluded that after a single intravenous injection of 40 mg/kg, sulfathiazole has a high tl/2β resulting in higher tissue concentrations. This half-life, which is higher than what is reported in the literature, is not influenced by the simultaneous presence of sulfamethazine. The tl/2β for sulfamethazine after a single intravenous injection of 80 mg/kg is comparable to the data from the literature and is not influenced by the presence of sulfathiazole. Sulfathiazole and SM were also administered simultaneously as an intramuscular injection to healthy pigs at a dosage of 40 and 80 mg/kg bodyweight. Pharmacokinetic experiments were conducted on three pigs. From this pharmacokinetic study it can be concluded that upon a single intramuscular administration of 40 mg/kg of ST and 80 mg/kg of SM the absolute bioavailability in pigs is 0.92 ± 0.04 for ST and l.01 ± 0.07 for SM. Six pigs received five intramuscular im) injections as a single dose of ST and SM every 24 h for five consecutive days for the residue study. The pigs were slaughtered at different times after the last dose was given and samples were taken from various tissues and organs. Concentrations were determined by a microbiological method and a HPTLC method. No edible tissue contained more than 100 μg/kg of the individual sulfonamides after 10 days of withdrawal. It means that adult animals which have a shorter half-life and thus lower tissue concentrations will certainly meet the economic community EC) maximum residue limits after a 10 days withdrawal period.

PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE, TESTOSTERONE AND ANDROSTENEDIONE IN CASTRATED AND ADRENALECTOMIZED BULL CALVES

1978 ◽  
Vol 79 (1) ◽  
pp. 137-138 ◽  
Author(s):  
J. J. BASS ◽  
A. J. PETERSON ◽  
E. PAYNE
Keyword(s):  
New Zealand ◽  
Plasma Concentration ◽  
Luteinizing Hormone ◽  
Agricultural Research ◽  
Plasma Concentrations ◽  
Young Male ◽  
Research Centre ◽  
Similar Magnitude ◽  
Research Division ◽  
Bull Calves

Ministry of Agriculture and Fisheries, Research Division, Ruakura Agricultural Research Centre, Hamilton, New Zealand (Received 17 April 1978) An increase in the plasma concentration of luteinizing hormone (LH) occurs in response to castration in bull calves aged 1–4 months; this response is of similar magnitude to that seen in cattle castrated as adults (Odell, Hescox & Kiddy, 1970). In bull calves castrated at birth, however, there is no increase in the plasma concentration of LH until after 28 days of age (Bass, Peterson, Payne & Jarnet, 1977). In other species a range of responses to castration has been reported. Gonadectomy of male guinea-pigs 0–35 days after birth produces an increase in the plasma concentration of LH similar to that observed in guineapigs castrated as adults (Donovan, ter Haar, Lockhart, MacKinnon, Mattock & Peddie, 1975). In contrast, the castration of young male macaques does not cause an immediate increase in the

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