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Biomedical subjects

W Hansel

Publications and source records attributed to W Hansel.

At least 73 records · Page 4Linked to original sources
PubMed1986

Involvement of lipoxygenase products of arachidonic acid metabolism in bovine luteal function.

A series of experiments was conducted to determine the effects of lipoxygenase products of arachidonic acid (AA) metabolism on the function of the bovine corpus luteum (CL). In the first experiment, reaction products of soybean lipoxidase-AA were added to dispersed bovine luteal cells in increasing concentrations. These lipoxygenase products resulted in a dose-related reduction in the biosynthesis of progesterone and 6-keto-prostaglandin (PG)F1 alpha, while the synthesis of PGF2 alpha was unaffected. In a second experiment, the addition of 5-hydroxyeicosatetraenoic acid (5-HETE), a specific lipoxygenase product, again resulted in a reduction in progesterone and 6-keto-PGF1 alpha, with no change in PGF2 alpha synthesis. Extremely high endogenous concentrations of 5-HETE were measured in luteal tissues (36 +/- 17 to 46 +/- 13 ng/10(6) cells) in a third experiment. In the fourth experiment, an inhibitor of the lipoxygenase pathways, nordihydroguaiaretic acid (NDGA) infused into the uterine lumen twice daily on Days 14-18 of the estrous cycle delayed luteolysis and resulted in lengthened estrous cycles (27.2 +/- 0.3 vs 21.5 +/- 1.0 days for controls, p less than 0.05). Thus, an inhibitor of the lipoxygenase pathway of arachidonic acid metabolism delays luteolysis, possibly by removing the preferential inhibition of PGF1 alpha biosynthesis caused by 5-HETE and other products of the lipoxygenase system. Collectively, these results suggest that products of the lipoxygenase pathway are involved in luteolysis in normal heifers.

Animals↗
PubMed1986

Hammond memorial lecture. New concepts of the control of corpus luteum function.

Five new concepts concerning the control of corpus luteum function in the cow have been developed in recent years. Prostacyclin (PGI-2) plays a luteotrophic role. Conversely, products of the lipoxygenase pathway of arachidonic acid metabolism, particularly 5 hydroxyeicosatetraenoic acid (5-HETE), play luteolytic roles. Luteal cells arise from two sources. The small luteal cells are all of theca cell origin; the large cells found early in the cycle (Days 2-6) are mainly of granulosa cell origin. However, a population of large cells found after Day 10 of the cycle are of theca cell origin. Oxytocin of luteal cell origin plays a role in development of the corpus luteum and possibly in its regression. The recently described Ca2+-polyphosphoinositol-protein kinase C second messenger system, as well as the LH-cAMP system, is involved in control of progesterone synthesis in the bovine corpus luteum. Progesterone synthesis in the small theca-derived luteal cells is primarily controlled by the cAMP system. However, elevated intracellular calcium diminishes cAMP-mediated progesterone synthesis in these cells. These findings modify our current concepts of the mechanisms of control of progesterone secretion by the corpus luteum and suggest several new lines of research.

Animals↗
PubMed1985

Concentrations of steroids and gonadotropins in follicular fluid from normal heifers and heifers primed for superovulation.

The concentrations of six steroids and of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in follicular fluid from preovulatory and large atretic follicles of normal Holstein heifers and from preovulatory follicles of heifers treated with a hormonal regimen that induces superovulation. Follicular fluid from preovulatory follicles of normal animals obtained prior to the LH surge contained extremely high concentrations of estradiol (1.1 +/- 0.06 micrograms/ml), with estrone concentrations about 20-fold less. Androstenedione was the predominant aromatizable androgen (278 +/- 44 ng/ml; testosterone = 150 +/- 39 ng/ml). Pregnenolone (40 +/- 3 ng/ml) was consistently higher than progesterone (25 +/- 3 ng/ml). In fluid obtained at 15 and 24 h after the onset of estrus, estradiol concentrations had declined 6- and 12-fold, respectively; androgen concentrations had decreased 10- to 20-fold; and progesterone concentrations were increased, whereas pregnenolone concentrations had declined. Concentrations of LH and FSH in these follicles were similar to plasma levels of these hormones before and after the gonadotropin surges. The most striking difference between mean steroid levels in large atretic follicles (greater than 1 cm in diameter) and preovulatory follicles obtained before the LH surge was that estradiol concentrations were about 150 times lower in atretic follicles. Atretic follicles also had much lower concentrations of LH and slightly lower concentrations of FSH than preovulatory follicles. Hormone concentrations in follicles obtained at 12 h after the onset of estrus from heifers primed for superovulation were similar to those observed in normal preovulatory follicles at estrus + 15 h, except that estrogen concentrations were about 6-40 times lower and there was more variability among animals for both steroid and gonadotropin concentrations. Variability in the concentrations of reproductive hormones in fluid from heifers primed for superovulation suggests that the variations in numbers of normal embryos obtained with this treatment may be due, at least in part, to abnormal follicular steroidogenesis.

Androstenedione↗
PubMed1985

Progesterone and prostanoid production by bovine binucleate trophoblastic cells.

A procedure for preparing highly enriched suspensions of bovine binucleate trophoblastic cells was developed and data showing that these cells produce progesterone, prostacyclin (PGI2), and prostaglandin E2 (PGE2) were obtained. Approximately 200 X 10(6) enzymatically dissociated cells from bovine cotyledons were applied to the surface of a density gradient of 2% to 4% Ficoll-400 using the Wescor CELSEP sedimentation chamber. After 90-120 min of sedimentation at unit gravity, fractions containing binucleate trophoblastic cells were obtained and washed in HEPES-buffered Medium 199. Preparations of 90% to 100% binucleate trophoblastic cells were obtained routinely; viability was 50% to 80%. After incubation at 37 degrees C, concentrations (ng/10(5) cells) of progesterone were greater in those fractions containing binucleate cells than in those containing primarily smaller, mononucleate cells. Total progesterone secreted (mean +/- SEM) after 4 h by 1 X 10(5), 2 X 10(5), 4 X 10(5), 8 X 10(5), and 1.6 X 10(6) binucleate cells was 0.27 +/- 0.03, 1.01 +/- 0.09, 4.02 +/- 0.37, 10.31 +/- 0.92, and 20.96 +/- 2.23 ng, respectively (r = 0.997). Addition of 10% fetal bovine serum (FBS) or normal anestrous cow serum increased (P less than 0.05) production of progesterone by binucleate trophoblastic cells. Luteinizing hormone, follicle-stimulating hormone, prolactin, thyrotropin, and 8-bromo-adenosine 3',5'-cyclic monophosphate had no effect. Binucleate trophoblastic cells also produced PGI2 in relation to number of cells incubated (r = 0.996). Time courses for production of PGI2, PGE2, and progesterone were similar. Aspirin inhibited production of PGI2 and PGE2 by about 50% at a dose of 100 microM; FBS stimulated production of both prostanoids.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Inhibition of bovine luteal function by indomethacin.

Experiments were conducted to determine the effects of infusing indomethacin, a prostaglandin synthetase inhibitor, into the uterine lumen on the development and function of the bovine corpus luteum in the presence and absence of concurrently administered oxytocin. Each treatment was given twice daily on d 4, 5 and 6 of the estrous cycle. Treatments (six heifers/group) and resulting estrous cycle lengths were as follows: (1) untreated controls, 20.6 +/- .4 d; (2) .2 M phosphate buffer vehicle infused into the uterine lumen, 21.0 +/- .6 d; (3) 40 mg indomethacin infused into the body of the uterus, 16.5 +/- 1.0 d; (4) 150 USP units oxytocin injected sc, 10.0 +/- 1.2 d and (5) a combination of oxytocin and indomethacin as in treatments 3 and 4, 14.1 +/- 1.3 d. Plasma concentrations of progesterone were lower (P less than .05) in each treatment group from d 7 onward, when compared with untreated and vehicle-treated controls. Indomethacin alone effectively inhibited the development and function of the corpus luteum, and was without effect on oxytocin-induced inhibition of luteal function. In summary, it appears that a prostaglandin of either uterine or ovarian origin, or both, is required for the normal development and function of the bovine corpus luteum.

Animals↗
PubMed1985

Increased ovulation rate of adult ewes treated with anti-bovine LH antiserum during the normal breeding season.

Adult Suffolk ewes (n = 14) were treated on d 10 of the estrous cycle with anti-bovine luteinizing hormone (LH) antiserum. Control ewes (n = 10) were treated with normal horse serum. Estrous behavior and the number of corpora lutea and ovarian follicles were examined at the subsequent estrous cycle. Daily plasma concentrations of progesterone (P4), follicle stimulating hormone (FSH) and estradiol were determined before and after treatment. Ewes treated with antiserum had a higher (P less than .05) ovulation rate (2.7 +/- .2) than did controls (2.1 +/- .1). No differences were found in the numbers of large (greater than 5 mm) or small (less than 5 mm) follicles between treatment groups. Estrus was delayed (P less than .025) approximately .6 d/in ewes treated with antisera. Immunoreactive FSH increased (P less than .05) within 1 d after treatment and remained higher than the controls for 5 d. Peak estradiol concentrations occurred on d 17 for treated ewes compared with peak concentrations on d 15 or 16 for control ewes. The P4 concentrations were generally less (P less than .025) in treated ewes throughout the luteal phase of the treatment cycle. These data demonstrate that ovulation rate is increased in ewes treated with LH antiserum. The marked increase in plasma FSH suggests a possible mechanism whereby ovulation rate is enhanced.

Animals↗
PubMed1985

A seven-day synchronization method for ewes using medroxyprogesterone acetate (MAP) and prostaglandin F2 alpha.

Estrous cycles of adult (n = 27), farm-flock, Suffolk ewes and Polypay range ewes (n = 224) were controlled with medroxyprogesterone acetate (MAP)-impregnated vaginal pessaries inserted (d 0) for 7 d in combination with prostaglandin F2 alpha (PGF2 alpha) injected on d 6. Descriptive criteria of the effects of this treatment regimen on endocrine characteristics of the estrous cycle were evaluated in the experiment with farm-flock ewes. The efficacy of this synchronization regimen on reproductive performance of range-bred ewes was tested in a second trial. Suffolk ewes bred at the second observed estrus after treatment to provide comparisons of cycle length between treated and control ewes. Polypay ewes were exposed to fertile rams at the controlled estrus. Eighty-nine percent of Suffolk ewes were in estrus within 3 d after pessary removal. All nonsynchronized Suffolk ewes (n = 24) were in estrus over a 21-d period. Estrous cycle lengths of treated ewes averaged 16.8 +/- .2 d. Plasma progesterone concentrations were similar for treated and control ewes during the luteal phase of the estrous cycle. Ninety-one percent of the range-bred, controlled ewes lambed. Sixty-two percent of these ewes lambed within 150 d after exposure to fertile rams compared with only 17% of nonsynchronized ewes (P less than .05). Lambing percentage was similar by 167 d for treated (87%) or control (88%) ewes. Lambs per ewe exposed averaged 1.68 and 1.80 for treated and nonsynchronized groups, respectively. These data indicate the effectiveness of this 7-d treatment method for control of the estrous cycle of ewes during the normal breeding season. Results further show that this treatment scheme has practical application for range breeding of ewes.

Animals↗
PubMed1984

Calcium-dependent, cyclic nucleotide-independent steroidogenesis in the bovine placenta.

Dispersed bovine placental cells (fetal cotyledon and maternal caruncle) were shown to synthesize progesterone. To determine if their steroidogenic activity could be modulated by a cyclic nucleotide-mediated process, we added luteinizing hormone, 8-bromoadenosine 3',5'-monophosphate, 8-bromoguanosine 3',5'-monophosphate, adenosine, or cholera toxin to dispersed cells from placentomes of 100-283 days gestational age and examined progesterone synthesis during 3-to 16-hr incubation periods. Net progesterone production, defined as the amount of progesterone released in excess of the zero-time cellular progesterone content, was determined by using a specific RIA. None of these agents significantly affected progesterone synthesis. In contrast, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (MIX; 0.2-0.5 mM) caused a marked increase in progesterone formation. In time course studies it was found that MIX produced a 5-fold increase in progesterone production in 16 hr, with steroid production increasing linearly during this time. MIX also increased the conversion of exogenous pregnenolone to progesterone by placental cells. In view of the failure of cyclic nucleotide analogues and activators of adenylate cyclase to stimulate steroidogenesis, it was necessary to consider other modes of action of MIX. Since MIX is known to affect intracellular calcium translocation, we examined the effects of the calcium ionophore A23187 on progesterone formation. This drug enhanced progesterone formation and augmented the stimulatory effects of MIX. The stimulatory action of A23187 was not affected by cyclic nucleotide analogues. Our data suggest that progesterone synthesis in the bovine placentome is calcium dependent and cyclic nucleotide independent.

1-Methyl-3-isobutylxanthine↗
PubMed1984

Prolongation of the bovine estrous cycle with a gonadotropin-releasing hormone analog.

A series of in vitro and in vivo experiments was conducted to determine the effects of gonadotropin-releasing hormone (GnRH) on bovine luteal function. Biosynthesis of progesterone by bovine luteal cells during a 2-h incubation was determined following addition of 0, 10, 20, 40, 80 and 100 ng GnRH. Synthesis of progesterone was significantly depressed only by the 100-ng dose of GnRH. Luteal cells were incubated with 0.1 and 1.0 microgram GnRH in the presence and absence of 0, 1, 2 and 5 ng bovine luteinizing hormone (LH). Again, only the highest dose of GnRH significantly depressed LH-stimulated production of progesterone. Three experiments were conducted to assess the effects of repetitively administered GnRH. In the first, twice daily intrauterine infusions of 100 micrograms GnRH on Days 12, 13 and 14 of the bovine estrous cycle was without effect on plasma concentrations of progesterone and the functional life span of the corpus luteum (CL). In the second experiment, 10 micrograms of a highly potent GnRH analog (GnRH-A) was injected subcutaneously four times daily on Days 9-12 of the estrous cycle. GnRH-A-treated heifers had longer (P less than 0.05) mean estrous cycle lengths (26.2 +/- 0.72 days) when compared to control heifers (20.25 +/- 0.25 days). Plasma concentrations of progesterone were higher in the GnRH-A-treated group on Days 9-13 and Days 15-22 of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Induction of lymphopenia causes luteal dysfunction in cattle.

Studies were conducted to determine the effects of lymphopenia on reproductive function in heifers. Ten normally cycling heifers were injected with antilymphocyte serum (ALS) or normal horse serum (NHS) once daily between Days 3-6 or 9-17 of the estrous cycle. The ALS caused a significant reduction in circulating lymphocytes without affecting other blood cells. Concentrations of plasma progesterone were reduced (P less than 0.05) in heifers treated with ALS compared to NHS-treated heifers. The concentrations of circulating luteinizing hormone (LH) were also reduced in ALS-treated heifers. LH determinations in frequently collected blood samples showed that the number of LH pulses in the ALS-treated animals (1.4 +/- 0.4) was significantly (P less than 0.05) lower than NHS-treated controls (3.2 +/- 0.2). These studies suggest that immunosuppression caused by induction of lymphopenia causes luteal dysfunction in cycling heifers as a result of decreased pituitary LH secretion.

Animals↗
PubMed1984

Origin of different cell types in the bovine corpus luteum as characterized by specific monoclonal antibodies.

Specific monoclonal antibodies to granulosa and thecal cell surface antigens were produced and used to determine the contributions of theca and granulosa cells to the bovine corpus luteum (CL). Binding of each antibody was examined on collagenase-dispersed luteal cells from 18 cycling and 14 pregnant heifers by indirect immunofluorescence. The percent binding of the large luteal cells to granulosa antibody (GrAb) declined (P less than 0.01) as the age of the CL advanced: 77 +/- 6, 47.5 +/- 3, and 30 +/- 2 for Days 4-6, 10-12 and 16-18, respectively. Further reduction in binding of GrAb to large cells occurred between 50 and 100 days of pregnancy and no labeling was seen thereafter. Fourteen percent of the small luteal cells were bound by GrAb on Days 4-6 of the cycle, and none were labeled during subsequent stages. In contrast, when thecal antibody (TAb) was used, the proportions of large cells that were labeled increased (P less than 0.01) between Days 4-6 (10 +/- 1.3%) and 10-12 (46 +/- 3%). The percentage of large cells bound by TAb then remained unchanged until midpregnancy, declined as pregnancy advanced, and disappeared during late gestation. A majority of small luteal cells were bound by TAb throughout the estrous cycle: 70 +/- 4%, 69 +/- 3% and 58 +/- 6% at Days 4-6, 10-12, 16-18, respectively. Labeling of small cells by TAb occurred throughout pregnancy but declined (P less than 0.05) as gestation advanced. These studies suggest that the large cells of the early cyclic CL are derived from granulosa cells, while most of the small cells are of thecal origin. Small cells develop into large cells as the age of the CL increases. Granulosa-derived cells disappear during early pregnancy, while cells of thecal origin persist throughout pregnancy.

Animals↗
PubMed1984

Modulation of bovine placental prostaglandin synthesis by an endogenous inhibitor.

An endogenous, heat-labile, inhibitor of prostanoid synthesis in maternal caruncle tissue of bovine placentomes was studied. Inhibitory activity was present in caruncle extracts from days 120-250 of gestation, but was not detectable at term (260-280 days). The disappearance of inhibitory activity coincided with an increase in the secretion of prostanoids by dispersed caruncle cells in culture. Coculture of caruncle cells from placentomes of 120-day gestation with fetal cotyledon cells resulted in suppression of prostanoid synthesis by the cotyledon cells. However, this inhibition was not observed in cocultures of dispersed caruncle cells and fetal cotyledon cells from term placentomes. Our findings indicate that an endogenous inhibitor modulates bovine placental prostaglandin synthesis. A decline in the level of this inhibitor at term may be one factor triggering increased prostanoid synthesis required for parturition.

Animals↗
PubMed1984

Insemination of Holstein heifers at a preset time after estrous cycle synchronization using progesterone and prostaglandin.

Two experiments were conducted to study estrous cycle control regimens that combine progesterone administration via an intravaginal device ( PRID ) with a single injection of prostaglandin F2 alpha (PG). In Exp. I, 242 Holstein heifers were assigned randomly to one of three treatment groups at 14 to 18 mo of age. Treatments were: 1) control, 2) PRID -6 + PG-6 ( PRID in place for 6 d plus PG on the day of PRID removal) and 3) PRID -7 + PG-6 ( PRID in place for 7 d plus PG on the day before PRID removal). Heifers were observed for estrous activity and were inseminated at 8 to 20 h after estrus was detected. Estrus and ovulation were effectively synchronized after both PRID + PG treatments. Ninety-nine percent of the heifers in each group were in estrus within 168 h after PG injection. However, the interval from PG administration to the onset of estrus was longer after PRID -7 + PG-6 (75 +/- 2 h) than after PRID -6 + PG-6 (66 +/- 2 h). A lower variance in the interval from PG treatment to estrus was observed after PRID -7 + PG-6, suggesting that the 24 h delay in PRID withdrawal improved the synchrony of the onset of estrus. Pregnancy rates (72 to 82%) did not vary across treatment groups. Two-hundred seventy-four heifers were assigned to Exp. II. Treatments were 1) control, 2) 2 X PG (two injections of PG at an 11 d interval) and 3) PRID -7 + PG-6.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Methylation in bovine luteal cells as a regulator of luteinizing hormone action.

Experiments were conducted to determine if methylation is a part of the mechanism by which luteinizing hormone (LH) and epinephrine stimulate progesterone production by dispersed bovine luteal cells. Corpora lutea (CL) were collected from 24 Holstein heifers on Day 10 of the estrous cycle and dispersed with collagenase. Net progesterone accumulation, representing total progesterone synthesized by 10(6) cells during a 2-h incubation was determined. Cells from 7 CL were treated with 0 and 5 ng LH, in the presence and absence of methylation inhibitor, S-adenosyl-homocysteine (SAH, 1 mM). LH-stimulated progesterone production was inhibited (P less than 0.05) in the presence of SAH(209 +/- 19 vs. 119 +/- 7 ng/10(6) cells). In the absence of LH, progesterone production was unaffected (87 +/- 22 vs. 68 +/- 28) by SAH. Cells from 4 CL were treated with 10 micrograms epinephrine or 10 micrograms isoproterenol with and without SAH. Both epinephrine and isoproterenol-stimulated progesterone production was inhibited (P less than 0.05) by the presence of SAH (204 +/- 24 vs. 125 +/- 18 and 198 +/- 15 vs. 130 +/- 8). Progesterone production by cells from 4 CL was unaffected by the presence of SAH when treated with Medium 199 (M199) (75 +/- 32), 10 micrograms cholera toxin, which directly stimulates adenylate cyclase on the cytoplasmic side of plasma membranes (168 +/- 19), or 3 mM dibutyryl cAMP (210 +/- 40).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Bovine placentomes contain factors which decrease progesterone secretion.

We examined the effects of 20% ammonium sulfate precipitates from cytosolic extracts of whole placental tissue collected between 100-150 days of gestation on progesterone secretion by bovine granulosa cells and dispersed bovine luteal cells. These extracts produced a dose-dependent inhibition (23-92%) of progesterone synthesis by bovine granulosa cells. However, no inhibitory activity could be demonstrated in similarly prepared extracts from term placentae. Inhibitory activity could be extracted from both maternal caruncles and fetal cotyledons. In the presence of 2 mg/ml of maternal caruncle extract, basal progesterone secretion was dramatically reduced (90%), as was steroidogenesis in the presence of bovine lutenizing hormone (bLH) and 8 bromocyclic (Br)-cAMP. Moreover, coincubation of dispersed luteal cells and dispersed fetal or maternal placental cells from 100- to 150-day placentae produced a significant (50%) reduction in progesterone content of the medium. The addition of 2 mg/ml of caruncle or fetal cotyledon extract from 100- to 150-day placentae also produced 100% and 50% inhibitions, respectively, of progesterone secretion by dispersed placental cells. Thus, the inhibitory factor appears to be produced by cells of both the maternal and fetal placenta. It is heat-stable and not extractable by ether. The inhibitory substance eluted was two distinct peaks from Sephadex G-100 columns, one with a molecular weight of about 60,000 daltons and the other about 30,000 daltons. Using isoelectric focusing, several peaks of inhibitory activity were obtained, one with a pI of 3-5, the others having pIs between 6 and 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Prostacyclin, prostaglandin F2 alpha and progesterone production by bovine luteal cells during the estrous cycle.

Corpora lutea (CL) were collected from Holstein heifers on Days 5, 10, 15 and 18 (5/day) of the estrous cycle. Dispersed luteal cell preparations were made and 10(6) viable luteal cells were incubated with bovine luteinizing hormone (LH) and different amounts of arachidonic acid in the presence and absence of the prostaglandin (PG) synthetase inhibitor indomethacin. The concentrations of progesterone, PGF2 alpha and 6-keto-PGF1 alpha, the stable inactive metabolite of prostacyclin (PGI2), were measured. Day 5 CL had the greatest initial content of 6-keto-PGF1 alpha (1.01 +/- 0.16 ng/10(6) cells), and synthesized more 6-keto-PGF1 alpha (2.55 +/- 0.43) than CL collected on Days 10 (0.57 +/- 0.11), 15 (0.08 +/- 0.05) and 18 (0.19 +/- 0.03) during a 2-h incubation period. Arachidonic acid stimulated the production of 6-keto-PGF1 alpha by Days 10, 15 and 18 luteal tissue. PGF2 alpha was produced at a greater rate on Day 5 (0.69 +/- 0.17 ng/10(6) cells) than on Days 10 (0.06 +/- 0.01), 15 (0.04 +/- 0.02) and 18 (0.08 +/- 0.01). Arachidonic acid stimulated and indomethacin inhibited the production of PGF2 alpha, in most cases. The initial content of 6-keto-PGF1 alpha was higher than that of PGF2 alpha on all days of the cycle and more 6-keto-PGF1 alpha was synthesized in response to arachidonic acid addition. The ratio of 6-keto-PGF1 alpha content to PGF2 alpha content was 4.39, 2.30, 1.25 and 1.13 on Days 5, 10, 15 and 18, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗