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Biomedical subjects

W Hansel

Publications and source records attributed to W Hansel.

At least 91 records · Page 5Linked to original sources
PubMed1983

Luteolytic effect of 13,14-dihydro-PGF-2 alpha in heifers.

Holstein heifers (4/group) were injected intramuscularly with 0, 5, 10 or 25 mg 13,14-dihydro-PGF-2 alpha on Day 10 of the oestrous cycle. Complete luteolysis and precocious oestrus occurred in 3 of 4 heifers receiving 25 mg and 1 of 4 receiving 10 mg 13,14-dihydro-PGF-2 alpha injected i.m. These features were not affected in heifers injected with 0 or 5 mg 13,14-dihydro-PGF-2 alpha, although plasma progesterone concentrations were depressed in all treated heifers within 75 min. LH concentrations were elevated between 5 and 8 h after 13,14-dihydro-PGF-2 alpha in all treated heifers. The addition of 13,14-dihydro-PGF-2 alpha to dispersed bovine luteal cells did not affect progesterone accumulation during a 2-h period. These results suggest that 13,14-dihydro-PGF-2 alpha may play a role in PGF-2 alpha-induced luteolysis.

Animals↗
PubMed1983

A luteolytic interaction between estradiol benzoate and prostaglandin F2 alpha in cattle.

A possible luteolytic interaction between prostaglandin F2 alpha (PGF2 alpha) and estradiol benzoate (E2B) in cattle was investigated by randomly assigning 20 heifers to one of four groups of a 2 x 2 factorially designed experiment. The treatments for the groups consisted of im administration of: 1) 200 micrograms of E2B, given twice daily on d 10, 11 and 12 of the estrous cycle plus 7 mg PGF2 alpha, given at a separate site, but concurrently with the last injection of E2B; 2) the vehicles for E2B (sesame oil) and PGF2 alpha (saline); 3) E2B and saline and 4) sesame oil and PGF2 alpha. Administration of both E2B and 7 mg PGF2 alpha resulted in luteolysis as evidenced by a shorter mean length of the estrous cycle (P less than .05) when compared with the vehicle-treated control group, and a decline in systemic concentrations of progesterone to less than 1 ng/ml in four of five animals. Administration of PGF2 alpha with sesame oil was luteolytic in only one of five animals and E2B plus saline had no effect on the mean length of the estrous cycle or systemic concentrations of plasma progesterone. These observations suggested a luteolytic interaction between E2B and PGF2 alpha. This luteolytic interaction was examined further in a second experiment. Corpora lutea was removed 12 h after treatment with 200 micrograms E2B or .5 ml sesame oil, administered twice on d 10, 11 and 12 of the cycle, and incubated with luteinizing hormone (LH) and PGF2 alpha in vitro. The effect of both LH and PGF2 alpha was to increase progesterone synthesis (P less than .01), and this effect was observed irrespective of E2B pretreatment. These findings were not consistent with the hypothesis that the luteolytic site of action for either E2B or PGF2 alpha was inhibition of the steroidogenic effects of LH as assessed under in vitro conditions.

Animals↗
PubMed1982

Luteolysis-induced changes in phase composition and fluidity of bovine luteal cell membranes.

X-ray diffraction, fluorescence polarization of trans-parinaric acid, and fluorescence photobleaching recovery of dioctadecyltrimethyneindolecarbocyanine have been used to characterize the phase composition and liquid phase fluidity of bovine luteal cell membranes and membrane lipids for functional corpora lutea collected at midcycle and for regressing corpora lutea collected after treatment with prostaglandin F2 alpha. These results support previous observations of gel phases in microsomal preparations of regressed luteal cells at physiological temperatures and further suggest that the plasma membrane may be the main source of this gel phase. Analysis of the overall lipid composition of the microsomal preparations from these cells indicates a role for sphingomyelin, in the presence of cholesterol, for the generation of a gel phase at physiological temperatures.

Animals↗
PubMed1982

Study of the direct action of luteinizing hormone-releasing hormone agonists at the testicular level in intact rats treated with an antiluteinizing hormone serum.

Is it well known that LHRH agonists can inhibit testicular functions by gonadal desensitization secondary to endogenous LH release and that a direct action at the gonadal level has also been demonstrated. Since an excess of anti-LH serum can be used, as an alternative to hypophysectomy, to neutralize the influence of endogenous LH release, the relative importance of the testis and pituitary gland in the inhibitory effect of a LHRH agonist, [D-Ser-(TBU)6,des-Gly-NH210]LHRH ethylamide (Buserelin), was studied on gonadal gonadotropin receptors in intact adult male rats treated with equine anti-LH or normal horse serum (NHS). A single administration of increasing doses (1-100 ng) of Buserelin leads to a progressive inhibition of testicular LH and PRL receptor levels by 70% and 40%, respectively, in animals injected with NHS. Treatment with the anti-LH serum completely prevents this inhibitory effect of a single dose of the LHRH agonist. After two successive injections of Buserelin in NHS-treated animals, testicular LH receptors are reduced by 70% and 80% with the 100- and 500-ng doses, respectively, while testicular PRL receptors are inhibited by 40-60%. In animals treated with the anti-LH serum, the inhibition of testicular LH receptors is reduced by only 18% (100 ng Buserelin) and 55% (500 ng Buserelin), while the inhibitory effect on PRL receptors is abolished. The present data show that endogenous LH release induced by a single injection of a LHRH agonist plays an essential role in the loss of testicular LH receptors measured 2 days later. Moreover, upon repeated injection of the LHRH agonist, neutralization of endogenous LH release by an anti-LH serum markedly reduces the inhibitory effect of the LHRH agonist on LH receptors, while it completely prevents the effect on PRL receptors, suggesting that the inhibitory effect of the LHRH agonist in the male rat is predominantly due to endogenous LH release rather than to a direct action of the peptide at the testicular level.

Animals↗
PubMed1982

Evidence of membrane changes during regression in the bovine corpus luteum.

Microsomal membranes prepared from bovine corpora lutea (CL) were examined by wide angle x-ray diffraction to determine if there were structural changes in the cellular membranes during regression. In samples prepared from CL removed at midcycle, all of the membrane lipid was in the liquid crystalline phase at body temperature. However, examination of microsomes prepared from regressing luteal tissue revealed a phase transition in which a portion of the lipid bilayer was in a gel phase at body temperature. Coincident with this physical change was a decline in CL function. These results indicate that there are structural changes that occur at the submicroscopic level in cellular membranes during luteal regression, which appear to be related to the loss in cellular function.

Animals↗
PubMed1981

Luteotropic effects of bovine blastocysts.

A series of experiments was conducted to determine whether 18-day bovine blastocysts could stimulate synthesis of progesterone by dispersed bovine luteal cells in vitro. Both blastocyst homogenates and extracts of blastocyst homogenates were luteotropic. The luteotropic activity of the blastocysts appeared to be due to one or more heat-labile substances with a molecular weight of less than 12,000 daltons.

Animals↗
PubMed1981

Gross and histopathologic effects of medroxyprogesterone acetate and progesterone on the mammary glands of adult beagle bitches.

Adult beagle bitches received 0.2 to 75 mg/kg doses of medroxyprogesterone acetate (MPA) once every 3 months for 1 to 1.5 years. Doses greater than 2.0 mg/kg prevented the recurrence of ovarian cycles; lower doses did not. MPA (10 and 75 mg/kg) induced a dose-related development of multiple, large (greater than 5 mm diameter) mammary nodules that occurred earlier in older dogs than in younger dogs. MPA-induced mammary hyperplasia and nonnodular dysplasias were also noted. Most of the large (5 to 110 mm in diameter) MPA-induced nodules were, in nearly equal numbers, nodules of lobular hyperplasia, simple adenomas, or complex adenomas. Such benign mammopathies all appear to have histopathologic counterparts in human breast disease. However, simple adenomas are uncommon in both humans and dogs. Some of the MPA-induced nodules were benign mixed tumors with cartilaginous metaplasia. No malignant tumors were found. Induction of mammary tumors by 75 mg MPA/kg was not affected by prior ovariectomy but was reached by prior hypophysectomy, suggesting involvement of pituitary secretion in MPA-induced mammary gland disease.

Adenoma↗
PubMed1981

Plasma hormone concentrations associated with early embryo mortality in heifers.

Results of a detailed study involving 18 pregnant, 17 cyclic and 12 inseminated but non-pregnant Holstein heifers indicated the following. (1) Jugular plasma progesterone concentrations were higher (P less than 0.05) in pregnant than in cyclic or in inseminated--non-pregnant animals from Days 10 through 18. (2) Jugular plasma progesterone concentrations of inseminated--non-pregnant animals could be related to heifers in which (a) fertilization may not have occurred (N = 5); (b) embryonic death may have occurred between Days 6 and 9 (N = 5); and (c) embryo mortality may have occurred shortly before Day 18 (N = 2). (3) Jugular plasma oestradiol concentrations were higher (P less than 0.05) in pregnant than in cyclic animals between Days 10 and 18; the oestrogen values of the inseminated--non-pregnant animals resembled those of the pregnant animals. (4) The steroid-synthesizing capabilities of incubated luteal tissues from inseminated--non-pregnant heifers more closely resembled those of tissues from pregnant animals than those of cyclic animals. (5) At Day 18 PGF concentrations in endometrial and luteal tissues and ovarian arterial plasma did not differ among the 3 groups. (6) PGF and progesterone concentrations of luteal tissues were negatively correlated (r = -0.77, P less than 0.05) in cyclic animals and positively correlated (r = 0.73, P less than 0.05) in pregnant animals, implying a luteotrophic effect of PGF in pregnant animals. These results suggested a luteotrophic effect of the embryo, beginning as early as Day 10 of pregnancy, and the results of further experiments suggested that (i) homogenates and extracts of Day 18 bovine embryos contain one or more substances capable of stimulating progesterone synthesis in dispersed bovine luteal cell preparations; (ii) the luteotrophic activity was proportional to the protein contents of the embryo homogenates; and (iii) the luteotrophic activity was heat labile and was removed from homogenates by dialysis, indicating a structure of one or more relatively small molecules.

Animals↗
PubMed1980

The effects of prostacyclin (PGI2) and 6-keto-PGF1 alpha on bovine plasma progesterone and LH concentrations.

Injections of 1 mg PGI2 directly into the bovine corpus luteum significantly increased peripheral plasma progesterone concentrations within 5 min. Concentrations were higher in the PGI2-treated heifers than in saline-injected controls between 5 and 150 min and at 3.5, 4, 5, and 7 h post-treatment. Levels tended to remain elevated through 14 h. Saline and 6-keto-PGF1 alpha were without effect on plasma progesterone levels. The luteotrophic effect of PGI2 was not due to alterations in circulating LH concentrations. An in vitro experiment assessed the effects of either PGI2 alone or in combination with LH on progesterone production by dispersed luteal cells. Progesterone accumulation over 2 h for control, 5 ng LH, 1 microgram PGI2, 10 micrograms PGI2, and 10 micrograms PGI2 plus 5 ng LH averaged 99 +/- 42, 353 +/- 70, 152 +/- 35, 252 +/- 45, and 287 +/- 66 ng/ml (n = 4), respectively. Thus PGI2 has luteotrophic effects on the bovine CL both in vivo and in vitro.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Oestrous cycle length and plasma progesterone concentrations following administration of prostaglandin F-2 alpha early in the bovine oestrous cycle.

Twice daily i.m. injections of PGF-2 alpha on Days 3 and 4 of the bovine oestrous cycle inhibited progesterone secretion by the corpus luteum and induced precocious oestrus. Injections given less frequently or earlier in the cycle did not induce precocious oestrus but twice daily injection on Days 2 and 3 or Day 4 appeared to inhibit progesterone secretion without affecting oestrous cycle length.

Animals↗
PubMed1980

Corpus luteum maintenance during early pregnancy in the cow.

Holstein heifers (18 pregnant, 12 inseminated but non-pregnant, and 17 cyclic) were studied during the first 18 days after oestrus. Jugular vein plasma progesterone concentrations were significantly (P < 0.05) higher in pregnant than in non-pregnant and cyclic animals between Days 10 and 18. Jugular oestradiol concentrations were also higher in pregnant than in cyclic animals between Days 6 and 16 (P < 0.05). No differences were found among the three groups in jugular LH levels during Days 1-18. Ovarian and uterine vein progesterone and oestradiol concentrations suggested that the elevated peripheral plasma concentrations of these steroids in pregnant animals were due mainly to increased ovarian production, but the embryo itself may have contributed to the oestradiol levels found at Day 17. Luteal tissues from pregnant animals contained more progesterone when incubated alone or with LH than tissues from cyclic animals (P < 0.06). However, LH-stimulated synthesis (incubated with LH minus incubated alone) was nearly identical for the three groups of tissues. Therefore, loss of responsiveness to LH does not appear to be the initial event in luteolysis. Concentrations of PGF in ovarian arterial plasma in cyclic and pregnant animals were similar at Day 18, although uterine vein concentrations were higher (P < 0.05) in the cyclic animals. Free arachidonic acid concentrations in corpora lutea at Day 18 were higher (P < 0.05) in cyclic than in pregnant animals. The data suggest that the embryo may produce one or more luteotrophic substances that stimulate increased progesterone secretion by the corpus luteum beginning as early as Day 10 of pregnancy.

Animals↗
PubMed1980

Concurrent uterine venous and ovarian arterial prostaglandin F concentrations in heifers treated with oxytocin.

In preliminary studies 5 of 6 heifers given oxytocin subcutaneously on Day 2--6 of the oestrous cycle had depressed progesterone levels by Day 5, and each had a precocious oestrus and a normal preovulatory LH surge. Oxytocin treatments given once daily on Days 5 and 6, or twice daily on Day 5 and 6 or 4, 5 and 6 resulted in shortened cycles and lower jugular progesterone concentrations in 1 of 5, 2 of 4 and 4 of 5 heifers, respectively. On the basis of these data, uterine venous and ovarian arterial catheters were inserted into 17 animals on Day 3 of the oestrous cycle and oxytocin treatments were given twice daily on Days 4, 5 and 6. Oxytocin treatment significantly depressed jugular progesterone levels by Day 8 and increased uterine venous prostaglandin (PG) F concentrations between 30 and 240 min after each injection. No changes of PGF concentrations occurred in uterine venous blood in control heifers, or in ovarian arterial blood from oxytocin-treated or control animals. It therefore appears that some factor other than PGF or a mechanism other than local veno-arterial transfer of PGF is involved in mediating the inhibitory effects of oxytocin on bovine corpus luteum function.

Animals↗
PubMed1980

Control of luteal function and implantation in the mink by prolactin.

Mink (Mustela vison) were treated during the period of embryonic diapause with prolactin or ergocryptine (CB-154). Prolactin advanced implantation time and hastened onset of luteal phase progesterone secretion. Duration of gestation in prolactin-treated adult mink was shorter than that of control mink. Ergocryptine had the opposite effects, prolonging gestation and inhibiting onset of luteal phase progesterone secretion. Prolactin is suggested to be the luteotrophin necessary for termination of embryonic diapause in mink.

Animals↗