Biomedical subjects

D Schams

Publications and source records attributed to D Schams.

At least 91 records · Page 5Linked to original sources

PubMed1994

Immunohistochemical aspects of insulin-like growth factors I and II in the bovine corpus luteum.

The cellular distribution of insulin-like growth factors I and II (IGF-I and -II) was examined in bovine corpora lutea at different stages of the luteal phase using specific antibodies and the avidin-biotin immunoperoxidase technique. At the cellular level, intense immunostaining for IGF-I was exclusively observed in large and small luteal cells and in a limited number of endothelial cells. Positive IGF-I immunoreactivity in luteal cells was thereby distributed in a distinct topographical, lobule-specific manner. Immunoreactivity in central areas of luteal lobules was most abundant in large luteal cells, whereas in peripheral zones significantly (P < 0.05) more small luteal cells exhibited IGF-I immunoreactivity. This distribution pattern was evident from day 4 of the cycle onwards and occurred at all the stages investigated. The percentage of positive small (SLC) and large (LLC) luteal cells revealed by semiquantitative analysis depended on the stage of the cycle as follows: days 4-7: 34% LLC versus 21.3% SLC in central areas and 25.1% LLC versus 32.7% SLC in peripheral zones; days 8-12: 42.9% LLC versus 19.9% SLC in central areas and 23.5% LLC versus 35.2% SLC in peripheral zones; days 13-16: 47.7% LLC versus 19.4% SLC in central areas and 19.2% LLC versus 41.4% SLC in peripheral zones. In contrast to IGF-I, no expression of IGF-II immunoreactivity was seen in large or small luteal cells. Positive immunoreactivity was restricted to the perivascular fibroblasts of large blood vessels and to the pericytes of capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Actions of somatotrophin on oxytocin and progesterone release from the microdialysed bovine corpus luteum in vitro.

In the present investigation, the effect of recombinant (BST) and pituitary-derived (bGH) bovine somatotrophin on progesterone and oxytocin release was examined. Individual copora lutea (CL) were obtained from cows at different stages of the oestrous cycle (days 5-7, 8-12 and 15-18) and also from early pregnancy (days 60-120) and were implanted with an in vitro microdialysis system (MDS). Perfusion with BST for 60 min (0.05, 0.5 and 5 mumol/l) induced a dose-dependent stimulation of progesterone release. Release of oxytocin from CL was significantly stimulated by BST at all dose levels. BST (0.5 mumol/l) stimulated progesterone release most during the early and mid-luteal phases and oxytocin release especially during the early luteal stage (days 5-7) of the oestrous cycle. CL from early pregnancy (days 60-120) treated with BST showed a significant response in progesterone and oxytocin release. bGH showed comparable effects. Our results suggest that somatotrophin acts directly on the secretory function of bovine CL in the MDS, specifically during the early luteal stage (days 5-7) of the oestrous cycle and early pregnancy (days 60-120). Somatotrophin may therefore have physiologically relevant effects associated with the development and maintenance of luteal function.

Animals↗

PubMed1994

Growth factors in milk.

The paper outlines well recognized growth factors in milk (colostrum and during lactation) like the IGF-family; epidermal growth factor; transforming growth factors a, beta; tumor necrosis factor; basic fibroblast growth factor and platelet derived growth factor The origin of these factors is discussed. The IGF-family may be of greater benefit to the newborn calf in contrast to other species where EGF seems to be the dominating and important factor. However, the primary role of the measured growth factors may be related more to the proliferation and maintenance of the lactating gland itself.

Animals↗

PubMed1993

A comparison of hormone levels in follicle-lutein-cysts and in normal bovine ovarian follicles.

Insulin-like growth factors 1 and 2 (IGF-1 and 2), oxytocin, progesterone, estradiol and ubiquitin were measured in bovine follicle-lutein-cysts and in follicular fluid after the classification of ovarian follicles by size (Class I = <4 mm; Class II = 5-8 mm; Class III = 9-12 mm; Class IV = preovulatory; Class V = cystic). It was found that IGF-1 concentrations increased during growth from 280 ng/ml in small follicles to 489 ng/ml in preovulatory follicles; IGF-2 appeared to remain constant in follicular fluid and in cysts (275 ng/ml). Oxytocin values were low in Class I, II and III follicles (30 pg/ml) but increased in preovulatory and cystic follicles (75 pg/ml). Estradiol increased significantly only in preovulatory follicles. Ubiquitin, a protein reflecting cellular replicative activity, could be found in bovine follicular fluid in high concentrations: 1.6 mug/ml in Class I,II and III follicles with the highest amounts in preovulatory follicles (2.3 mug/ml). In contrast with normal follicles, cysts were found to have a minimal concentration of ubiquitin (0.3 mug/ml). Progesterone levels were 5 times higher in cysts (325 ng/ml) and IGF-1 concentrations were markedly higher in cystic follicles (881 ng/ml) than in the other follicles. Simultaneously, maximum gene expression for IGF-1 was found in granulosa/lutein cells of cystic follicles (Class V), suggesting de novo synthesis of IGF-1. Between the different follicle classes progesterone, oxytocin and IGF-1 concentrations correlated positively (r=0.82). Hormonal levels in follicle-lutein-cysts indicated an arrested stage of insufficient luteinization as a possible result from the premature release of LH or from the release of amounts of LH inadequate to cause ovulation.

Journal Article↗

PubMed1993

Milk removal in familiar and unfamiliar surroundings: concentrations of oxytocin, prolactin, cortisol and beta-endorphin.

Eight cows were machine milked either in an operating theatre or in their familiar barn. During the experiments, milk flow curves were recorded and blood samples were taken for determination of concentrations of oxytocin, prolactin, cortisol and beta-endorphin. The milking cluster was attached without udder preparation. After cessation of milk flow, air was blown into the vagina for 2 min. When milk flow had stopped again, 1 i.u. oxytocin and finally 10 i.u. oxytocin were injected to remove the remaining milk. After the start of milking, oxytocin remained basal in unfamiliar, but increased in familiar surroundings. Therefore, during normal milking only 9% of total milk was removed in unfamiliar, whereas 79% was available in familiar surroundings. In response to subsequent vaginal stimulation in the operating theatre, oxytocin increased transiently in five cows and 15-71% of the milk was removed in these animals. In the other three cows in the operating theatre, oxytocin remained basal during vaginal stimulation, and no more milk was available. After injection of 1 i.u. oxytocin, 56 and 11%, and after injection of 10 i.u. oxytocin, 13 and 8% of milk was removed in unfamiliar and familiar surroundings respectively. Concentrations of prolactin increased during the course of milking in both treatments. Premilking concentrations of cortisol and beta-endorphin were elevated in unfamiliar as compared with familiar surroundings. During the course of milking, cortisol increased slightly and beta-endorphin decreased in unfamiliar, whereas both hormones increased markedly during milking in familiar surroundings.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Acute actions of prostaglandin F2 alpha, E2, and I2 in microdialyzed bovine corpus luteum in vitro.

The bovine CL is one of the sites for the production of prostaglandins (PG). Although many in vitro models, mainly using dispersed luteal cell incubations, have shown the variety of CL responses to PGs (luteotropic, no effect, or luteolytic), the functional role of luteal PGs in cattle remains to be elucidated. Therefore, the aim of the present study was to examine the effects of PGs with respect to progesterone (P4) and oxytocin (OT) release from the bovine CL in vitro (Days 8-12 of the estrous cycle) via a microdialysis system (MDS), in which intact cell-to-cell contact exists. Thirty-minute perfusion with PGF2 alpha, PGE2, and PGI2 (10(-10)-10(-5) M) induced significant, but different, acute effects. PGF2 alpha and PGE2 clearly stimulated hormone (P4 and OT) release, while PGI2 slightly inhibited hormone secretion during infusion at low doses but stimulated secretion at 10(-6) and 10(-5) M concentrations. Additionally, catabolized PGF2 alpha and PGI2 (13,14-dihydro-15-keto-PGF2 alpha [PGFM] and 6-keto-PGF1 alpha, respectively) induced responses different from those of the original PGs; both PGFM and 6-keto-PGF1 alpha at low doses weakly inhibited P4 release, but at 10(-5) M concentration stimulated release. Phorbol 12-myristate 13-acetate (TPA), a potent stimulator of the protein kinase C (PKC) system in bovine luteal cells, stimulated P4 and OT release when administered alone. Pre-exposure with TPA (10(-9) M) for 2.5 h resulted in an increase in the stimulative potency of PGF2 alpha and PGI2, but not of PGE2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Chicken egg antibodies for immunohistochemical labeling of growth hormone and prolactin in bovine pituitary gland.

We describe the production of polyclonal chicken antibodies specific for bovine growth hormone (bGH) and prolactin (PRL). Antibodies were generated by immunization of laying hens with recombinant bGH (rbGH), pituitary derived bGH (pbGH), and ovine PRL (oPRL). After the lipoprotein fraction was removed by dextran sulfate precipitation the antibodies were isolated from the egg yolks by ammonium sulfate precipitation. Immunization with rbGH and oPRL generated large amounts of specific antibodies, as revealed by ELISA and Western blot analysis. Antibodies against pbGH showed pronounced crossreactions with oPRL. The antibodies against rbGH and oPRL were well suited for sensitive and specific labeling of the GH- and PRL-synthesizing cells in bovine pituitary glands by immunohistochemistry. In addition, a quick and sensitive procedure for demonstration of both bGH- and PRL-synthesizing cells in a single paraffin section by double immunohistochemistry is presented. The chicken anti-bGH antibodies showed excellent results in combination with rabbit anti-PRL antibodies. The main advantage of avian antibodies in double immunostaining methods is the lack of crossreactions between avian antibodies and mammalian immunoglobulins and receptors which bind to the crystalline fragment of mammalian immunoglobulins (Fc receptors).

Animals↗

PubMed1993

Follicular fluid composition in the grey seal (Halichoerus grypus) during the oestrous cycle.

During the period of lactational oestrus, the corpus luteum of ovaries of grey seals decreased in size following the birth of the pup, while on the contralateral ovary one major large follicle rapidly expanded. These large follicles had the highest concentration of oestradiol (4282 +/- 609 ng ml-1) and progesterone (499 +/- 168 ng ml-1). Osmolality (322 +/- 3 mosmol kg-1) and the intrafollicular concentration of electrolytes (Na: 126 +/- 1; Cl: 96 +/- 1; Ca: 1.3 +/- 0.1 mumol ml-1) and proteins (94 +/- 1 mg ml-1) were independent of stage of lactation and follicle size. Concentrations were lower in follicular fluid than in plasma. The concentrations of triglycerides and, to some extent, those of vitamin E, cholesterol and phospholipids were affected by the decrease in the plasma concentration of these components with the onset of lactation and the increase in follicle size. These two events resulted in a marked decrease of these components in the largest follicles at the end of lactational oestrus. Vitamin A (exclusively as retinol), although a blood-borne component in follicular fluid, was the only component with a higher concentration in small and medium follicles than in plasma and decreased with increasing follicle size despite an increase in plasma retinol. This decrease and the negative correlation with intrafollicular oestradiol might indicate a high demand of preovulatory follicle structures for vitamin A owing to its possible importance in steroid hormone or protein synthesis or in both processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Localization and concentration of a new bioactive acetic seminal fluid protein (aSFP) in bulls (Bos taurus).

The concentration of the new bioactive acetic seminal fluid protein (aSFP) was determined in body fluids of bulls. An aSFP-specific radioimmunoassay was elaborated and established for routine measurement. No crossreaction of the aSFP antibody was found with other seminal plasma proteins and known growth factors. The 14 kDa aSFP was detected in secretions of ampulla and seminal vesicles by immunoblot analysis, but not in testis, epididymis or blood. Large quantities of aSFP were measured by radioimmunoassay in the fluid from the ampulla (2.6 +/- 0.3 mg ml-1) and seminal vesicles (3.0 +/- 0.4 mg ml-1). Immunohistochemistry techniques demonstrated that aSFP was localized mainly in the secretory epithelium of ampulla and seminal vesicles. Large amounts of aSFP (4.0 +/- 0.4 mg ml-1) were present in seminal plasma of bulls within a range of 1-7 mg ml-1, but aSFP could not be found on membranes of spermatozoa. Concentrations vary considerably among individuals, suggesting that aSFP may have a role in bovine reproduction.

Animals↗

PubMed1993

Multiple effects of neuropeptide Y, substance P and vasoactive intestinal polypeptide on progesterone and oxytocin release from bovine corpus luteum in vitro.

Recent observations indicate that the rat ovary receives not only adrenergic but also peptidergic innervation. In ruminants, there are few data available on the extent of a possible direct regulation of the peptidergic innervation of the ovary including the corpus luteum (CL). The direct effects of neuropeptide Y (NPY), substance P (SP) and vasoactive intestinal polypeptide (VIP) on the release of progesterone and oxytocin from midluteal phase CL (days 8-12) were examined in vitro. A possible direct neural influence might provide a sensitive short-term control. Long-term as well as short-term effects were assessed using both a serum-reduced luteal cell culture and a microdialysis system (MDS) of luteal tissue. In the long-term experiments, luteal cells were preincubated from the start of the culture for 48 h with NPY, SP and VIP (10 pmol/1-100 nmol/l). During the following 4 h the neuropeptides showed a dose-dependent stimulation of progesterone release, but there was no effect on oxytocin release. LH showed a synergistic effect with NPY, SP and VIP on progesterone release. In the short-term experiments, the neuropeptides were added 48 h after the start of the culture. All three peptides were most stimulatory to LH-supported progesterone release 30 min after addition, and the effect decreased greatly thereafter to the control level from 60 to 120 min. In contrast, LH alone induced the maximal progesterone stimulation at 120 min. In the MDS, a 30-min perfusion with NPY, SP or VIP (10 nmol/l, 100 nmol/l and 1 mumol/l) induced significant acute effects on progesterone and oxytocin release.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of somatotropin treatment on growth performance, carcass traits, and the endocrine system in finishing beef heifers.

The objectives of this study were to investigate the effects of exogenous somatotropin on growth performance and carcass traits and on concentrations of somatotropin (ST), IGF-I, insulin, glucagon, free fatty acids (FFA), and glucose in plasma of finishing Simmental beef heifers. Three treatment groups, which included 12 heifers each, received a subcutaneous injection of a slowly released recombinant bovine somatotropin (rbST) at two doses (320 and 640 mg, respectively) or a placebo at 2-wk intervals. Treatments began at an average BW of 286 kg and continued until the animals were slaughtered at approximately 520 kg. Heifers had ad libitum access to corn silage and received 1.8 kg/d of concentrate. A before-feeding blood sample was collected from the jugular vein immediately before and 1 wk after each injection during treatment. Treatment tended to increase ADG and to reduce energy consumption per kilogram of gain, whereas feed and energy intake were not altered. Dressing percentage and conformation did not seem to be affected by treatment. Treatment led to a dose-dependent reduction of fat tissue in carcass as well as in kidney fat and to a simultaneous increase of lean tissue (P < .05). Furthermore, treatment caused moderate increases of ST in both treated groups, whereas IGF-I concentrations increased markedly soon after the beginning of the treatment. Insulin and FFA concentrations were elevated in treated groups compared with controls. Glucagon concentrations were not altered by treatment. Effects on growth performance and carcass characteristics are discussed in view of metabolic and endocrine changes.

Adipose Tissue↗

PubMed1993

Pharmacokinetics of a recombinant bovine growth hormone and pituitary bovine growth hormone in lactating dairy cows.

The disposition of pituitary-derived bovine growth hormone (pbST) and of a recombinant bovine growth hormone (rbST) produced by Lilly (somidobove, USAN) were compared after an intravenous bolus administration (36.69 micrograms/kg for pbST and 35 micrograms/kg for rbST) to eight lactating cows in a crossover study. It was shown that dose-dependent parameters (volume of distribution, clearance) were significantly different between the two test articles. The steady mean state volume of distribution (.10 +/- .018 vs .12 +/- .015 L/kg) and clearance (.119 +/- .012 vs .143 +/- .011 L.kg-1.h-1) were lower for the pbST than for the somidobove. In contrast, the mean (+/- SD) residence times were not different for the two test articles (50.0 +/- 8.6 vs 46.9 +/- 5.9 min for pbST and somidobove, respectively). The origin of the difference is unclear, but it cannot be explained by the slight difference between the administered dose of the two test articles (< 5%) because the actual dose rate was used to calculate all dose-dependent parameters.

Animals↗

PubMed1992

Aetiology of disturbed milk ejection in parturient primiparous cows.

Milk flow in nine primiparous cows with disturbed milk ejection (D) and in six corresponding control animals (C) with normal milk removal was recorded during machine milking and blood samples were taken before and during milking to determine plasma oxytocin, vasopressin, prolactin, cortisol, oestradiol-17 beta, luteinizing hormone, progesterone and beta-endorphin concentrations. Manual teat stimulation before milking lasted for 1 min. After milk flow had stopped, air was blown into the vagina for 2 min. When milk flow had stopped again, 1 i.u. oxytocin and finally 10 i.u. oxytocin were injected to remove residual milk. During and after teat stimulation, oxytocin remained basal in D, but increased in C, whereas prolactin increased in both groups. While 94% of total milk was obtained in C during this period, only 9% could be removed from D, indicating lack of alveolar milk ejection. During vaginal stimulation, oxytocin increased transiently in D and more than by teat stimulation in C. This allowed the removal of 75% of milk in D, whereas almost no more milk was available in C. After oxytocin injections, 3 and 16% of residual milk were obtained in C and D respectively. Basal oestradiol-17 beta concentration was higher in D than in C (11.6 and 2.0 ng/l respectively), whereas beta-endorphin level was lower (24.1 and 86.6 micrograms/l respectively). Basal concentration of luteinizing hormone and progesterone, and concentration of cortisol and vasopressin before and during milking were comparable in C and D. We conclude that in cows with disturbed milk ejection afferent nervous pathways to the hypothalamus were intact, because prolactin was released by teat stimulation. However, oxytocin was only released by vaginal stimulation, i.e. milk ejection was centrally inhibited during teat stimulation.

Animals↗

PubMed1992

Evidence for oxytocin receptors in cultured bovine luteal cells.

Specific receptors for oxytocin (OT) on intact luteal cells are demonstrated. Cultured cells from bovine corpora lutea (CL) at different stages (Days 3-5, 8-12, and 15-18 of the estrous cycle) were examined for OT receptors by a radioreceptor assay using the 125I-labeled OT antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH2(9)] -vasotocin. Binding specificity was demonstrated in displacement studies with various related peptides. Scatchard analysis revealed the presence of a binding site with an association constant of Ka = 2.6 x 10(9) M-1 and a capacity of 5.9 fmol/micrograms DNA. Additionally, in 50% of the experiments (n = 6) two different binding sites were observed. The Ka of the high-affinity site was 2.6 x 10(10) M-1; its capacity was 0.73 fmol/micrograms DNA. The low-affinity site had an apparent Ka of 4.9 x 10(8) M-1 and a capacity of 8.8 fmol/micrograms DNA. Observation of one versus two binding sites related neither to the assay conditions nor to the state of the individual CL used for the cell culture and therefore appeared to reflect individual variation within the OT receptor population. Significant binding of OT was observed at all luteal stages. OT binding was maximal at the mid-luteal stage (Days 8-12). We conclude that a direct action of OT on the bovine CL is mediated by the OT receptor, supporting the hypothesis that luteal OT plays an important physiological role in the regulation of progesterone release and/or other luteal functions in a paracrine or autocrine fashion.

Animals↗

PubMed1992

Binding and action of insulin-like growth factors and insulin in bovine luteal tissue during the oestrous cycle.

The effect of insulin-like growth factors (IGFs) and insulin on the release of progesterone and oxytocin from bovine corpus luteum was investigated at early (days 5-7), mid- (days 8-12) and late (days 15-18) luteal phases of the oestrous cycle in an in vitro microdialysis system. The expression of specific receptors was evaluated in bovine corpora lutea of the respective luteal stages. A 30 min infusion of IGF-1, IGF-2 (1.3, 13 and 130 nmol l-1) or insulin (13, 130 and 1300 nmol l-1) caused a stimulation of the release of progesterone (P < 0.05). IGF-1 was most effective in releasing progesterone. Oxytocin release from corpora lutea was stimulated by insulin at all doses tested (13-1300 nmol l-1), whereas the IGFs were only effective at the highest dose (130 nmol l-1) applied. The high doses of IGFs (130 nmol l-1) and insulin (1300 nmol l-1) stimulated the release of progesterone and oxytocin throughout the luteal phase (P < 0.05). For all three peptides, greatest stimulation was seen during the late luteal phase (days 15-18 of the oestrous cycle) with the peak of progesterone release directly related to peptide infusion (P < 0.05). In addition, IGF-1 stimulated total release of progesterone (units in 4 h) after the beginning of the stimulation during this phase (P < 0.05). IGF-1 caused a gradual increase of progesterone even beyond the time of peptide perfusion, whereas IGF-2 and insulin stimulated progesterone release only during the peptide perfusion. Distinct receptors for IGF-1 and IGF-2 were present in corpora lutea membrane preparations at all stages investigated. Specific binding for insulin was also seen in all stages of the cycle without any cycle-dependent changes in the amount of binding. The displacement of labelled insulin by unlabelled IGF-1 and IGF-2 did not show the rank of order that has been described as typical for insulin receptors (i.e. insulin > IGF-1 > IGF-2), but comparable binding affinities were observed for the three unlabelled ligands. Specific binding of IGF-2 was markedly higher than that of IGF-1 or insulin throughout the cycle (1.9- and 4.9-fold higher compared with IGF-1 and insulin, respectively). Receptor specificity did not change during luteal development. Binding affinity and capacity of IGF-1 receptor was constant throughout the oestrous cycle. Specific IGF-2 binding increased and showed a positive co-operativity towards the end of the cycle. Specific binding of insulin was not significantly different in the three luteal stages examined.

Animals↗

PubMed1992

Effects of basic fibroblast growth factor, transforming growth factor-beta and nerve growth factor on the secretory function of the bovine corpus luteum in vitro.

The effects were investigated of basic fibroblast growth factor (bFGF), transforming growth factor-beta (TGF-beta) and nerve growth factor (NGF) on the release of progesterone and oxytocin from the bovine corpus luteum (CL) at different stages of the oestrous cycle. A microdialysis system (MDS) of CL and a cell culture system with a reduced number of endothelial cells were used. In the MDS of CL from the mid-luteal stage (days 8-12 of the oestrous cycle), infusion with bFGF (0.1, 1, 10 and 100 ng/ml), TGF-beta (0.1, 1 and 10 ng/ml) and NGF (0.1, 1, 10 and 100 ng/ml) for 30 min induced significant acute effects on the release of progesterone. Both bFGF and NGF stimulated the release of progesterone during peptide infusion, TGF-beta and also bFGF in the period thereafter. This stimulation was dose-dependent during and after the infusion only for bFGF. This response pattern was observed at all luteal stages for the three growth factors, but bFGF was more stimulatory at the early (days 5-7) and mid-luteal stages during and after peptide infusion. The release of oxytocin was stimulated by bFGF in a dose-dependent manner. At the highest dose, bFGF, TGF-beta and NGF stimulated the release of oxytocin throughout all three luteal stages. When luteal cells were cultured with growth factors, only TGF-beta showed a dose-dependent inhibition of both basal and LH-stimulated progesterone as well as oxytocin release (measured between 48 and 52 h of culture). NGF had an inhibitory effect only on the basal release of oxytocin. bFGF had no effect on the release of either hormone under continuous stimulation in cell culture. The results indicate that bFGF, TGF-beta and NGF act directly and acutely on the secretory function of bovine CL in the MDS but also have long-term effects as shown in cell culture. bFGF appears to be an important autocrine/paracrine regulator of CL function, since local expression of its mRNA, peptide synthesis and its mitogenic and non-mitogenic actions have now been confirmed. Endothelial cells from the CL have been identified as target cells for bFGF. Differences observed between the two systems might thus be attributed to the presence or absence of cell-to-cell contact and a reduced number of endothelial cells, as well as to the duration of peptide stimulation and medium changes every 24 h compared with the flow-through conditions in the MDS.

Animals↗

PubMed1992

Regulation of bovine intra-luteal function by peptide hormones.

There is increasing evidence for the existence of substances in ovarian tissues and fluids which are able to act locally, either alone or by modulating the actions of the gonadotropins, thus modifying the functions of ovarian cells. There are now clear data for oxytocin (OT), insulin-like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) in luteal tissue, with regard to specific expression of mRNA, secretion of peptid and receptors. Biological effects of these growth factors and others on luteal tissue were determined during the estrous cycle using two different in vitro systems; a novel microdialysis system (MDS) of intact luteal tissue and culture of luteal cells. The concentrations of secreted progesterone and OT were used as parameters. MDS; OT was most stimulative during the early luteal phase (days 5-7) and decreased continuously from days 8-12 to days 15-18. During early and mid stages bFGF was the most potent stimulator and at the late stage IGF-1 and IGF-2 were most stimulatory. Transforming growth factor beta (TGF-beta) stimulated the release of OT most effective at the early luteal stage. Results from the cell culture system (where no cell to cell contact exists) showed a different pattern. IGF-1 and IGF-2 had a stimulatory effect during long and short term stimulation, bFGF only during short term and OT showed no effect. Receptors were found for all peptides examined of luteal cells. A model of an intraovarian cascade-like system for the amplification of luteal function is presented.

Animals↗

PubMed1992

[Gonadotropin release and course of diseases after administration of a GnRH-analog in cattle with follicular-thecal cysts].

Twenty-five heifers and cows with follicular cysts (high level of total oestrogens, low level of progesterone in plasma) were treated with 20 or 50 micrograms buserelin i.m. 5-84 weeks after parturition. Two hours after medication an increased LH release was observed in all animals. In contrast to LH, FSH concentration was not increased in all cows. Twelve days after treatment a high progesterone concentration in plasma could be determined in 17 of 25 treated animals. Twenty cows showed oestrous symptoms 23.5 +/- 9.6 days after medication. The oestrous cycle was prolonged in 10 cows. Nineteen cows were inseminated and 14 cows became pregnant after 1-4 (phi 1.7 +/- 0.9) inseminations (73.6% of all inseminated cows and 56% of all treated cows). The differences in conception rate and in services per conception after treatment with 20 or 50 micrograms buserelin in favour of the higher dosage cannot be attributed to the medication.

Animals↗