Search Results

You are looking at 1 - 9 of 9 items for

  • Author: O. M. Møller x
Clear All Modify Search
Free access

O. M. MØLLER

Summary.

Five parous mink bitches remained unmated and unstimulated, during the mating season (i.e. March) and up to 17th April. Seven blood samples were taken between the 17th April and 23rd May. Two of the animals were ovariectomized on 17th April. The plasma progesterone levels and the ovarian histology indicated that unmated mink may develop active corpora lutea, presumably after spontaneous ovulation.

Six pregnant mink were ovariectomized at various stages of pregnancy. In all the bitches, the ovariectomy resulted in an abrupt fall in the peripheral plasma progesterone levels and termination of pregnancy. It seems reasonable, therefore, to assume that in the mink an obligatory relationship exists between luteal function and the maintenance of pregnancy.

Free access

O. M. MØLLER

Summary.

Four blue fox vixens were ovariectomized at different stages of pregnancy. Ovariectomy resulted in an abrupt fall in the peripheral plasma progesterone levels. About 2 days after ovariectomy, blood and/or fetuses were noticed in the respective pens, indicating that removal of the ovaries in this species terminates gestation.

Free access

A. J. Smith, O. P. F. Clausen, B. Kirkhus, T. Jahnsen, O. M. Møller and V. Hansson

Summary. The testes of the blue fox (Alopex lagopus) showed marked seasonal variations in size. Testicular weight and volume increased rapidly during January and February to reach maximal values by the beginning of the breeding season (~15 March). During May and June the weights and volumes of the testes declined gradually to the quiescent state which lasted from July until October. Quantitation by DNA flow cytometry of the seasonal changes in the relative numbers of haploid (1C), diploid (2C) and tetraploid (4C) cell numbers in the testis showed that the increase in testis size from December to February was associated with a rapid expansion of the haploid cell compartment as spermatogenesis resumed. In addition, an increase in number of more mature cell types within the haploid cell population was observed over a 2-month period before the breeding season. The decline in testicular size from the middle of April until October was associated with a reduction in both the absolute and relative sizes of the haploid and tetraploid cell populations and a concomitant increase in the relative numbers of diploid cells. Measurements of the activity of the soluble Mn2 + -dependent adenylate cyclase revealed seasonal variations that closely paralleled those of the haploid cell population, indicating that, as in other species, the enzyme may be associated with maturing germ cells.

Free access

A. J. Smith, M. Mondain-Monval, O. M. MØller, R. Scholler and V. Hansson

Summary. The seasonal changes in testicular weight in the blue fox were associated with considerable variations in plasma concentrations of LH, prolactin, androstenedione and testosterone and in FSH-binding capacity of the testis. An increase in LH secretion and a 5-fold increase in FSH-binding capacity were observed during December and January, as testis weight increased rapidly. LH levels fell during March when testicular weight was maximal. Plasma androgen concentrations reached their peak values in the second half of March (androstenedione: 0·9 ± 0·1 ng/ml; testosterone: 3·6 ± 0·6 ng/ml). A small temporary increase in LH was seen in May and June after the breeding season as testicular weight declined rapidly before levels returned to the basal state (0·5–7 ng/ml) that lasted until December. There were clear seasonal variations in the androgenic response of the testis to LH challenge. Plasma prolactin concentrations (2–3ng/ml) were basal from August until the end of March when levels rose steadily to reach peak values (up to 13 ng/ml) in May and June just before maximum daylength and temperature. The circannual variations in plasma prolactin after castration were indistinguishable from those in intact animals, but LH concentrations were higher than normal for at least 1 year after castration.

Free access

M. Mondain-Monval, O. M. MØller, A. J. Smith, A. S. McNeilly and R. Scholler

Summary. A heterologous radioimmunoassay system developed for the rabbit and suitable for a wide range of mammalian species has been shown to measure prolactin in the plasma of the blue fox. Evaluation of prolactin levels throughout the year showed that concentrations displayed a circannual rhythm with the highest values occurring in May and June. Prolactin concentrations remained low (∼2·5 ng/ml plasma) from July until April with no consistent changes found around oestrus (March—April). In 8 pregnant females, the prolactin increase in late April and May coincided with the last part of gestation and lactation: concentrations (mean ± s.e.m.) increased to 6·3 ± 0·6 ng/ml at mid-gestation, 9·7 ± 2·1 ng/ml at the end of gestation and 26·7 ± 5·0 ng/ml during lactation. In 10 non-pregnant animals, the mean ± s.e.m. values were 7·2 ± 1·2 ng/ml in April, 8·8 ± 2·2 ng/ml in May and 9·8 ± 1·3 ng/ml in June. The prolactin profile in 4 ovariectomized females was similar to that observed in non-pregnant animals, but the plasma values tended to be lower during the reproductive season (April—June). In intact females, the only large LH peak (average 28 ng/ml) was observed around oestrus. During pro-oestrus, baseline LH levels were interrupted by elevations of 3·1–10·4 ng/ml. During the rest of the year, basal levels were < 3 ng/ml. In ovariectomized females, LH concentrations increased within 2 days of ovariectomy and remained high (35–55 ng/ml) at all times of year.

Free access

M. Mondain-Monval, A. J. Smith, P. Simon, O. M. Møller, R. Scholler and A. S. McNeilly

Summary. A heterologous radioimmunoassay system developed for the sheep was shown to measure FSH in the plasma of the blue fox. FSH concentrations throughout the year showed a circannual rhythm with the highest values (61 ·6 ± 14·8 ng/ml) occurring shortly before or at the onset of the mating season, a pattern similar to that of LH. The concentration of FSH then declined when androgen concentrations and testicular development were maximal at the time of the mating season (March to May). Thereafter, concentrations remained low (25·2 ± 4·1 ng/ml) in contrast to those of LH. Implantation of melatonin in August and in February maintained high plasma values of FSH after the mating season (142·3 ± 16·5 ng/ml) in association with a maintenance of testicular development and of the winter coat. The spring rise of prolactin was suppressed by melatonin treatment. The release of FSH after LHRH injection was also increased during this post-mating period in melatonin-treated animals, in contrast to the response of the control animals which remained low or undetectable.

These results suggest that changes both in the secretions of FSH and prolactin may be involved in the prolongation of testicular activity and in the suppression of the spring moult after melatonin administration.

Keywords: blue fox; FSH; melatonin; LHRH; seasonal cycle

Free access

O. M. Møller, M. Mondain-Monval, A. Smith, E. Metzger and R. Scholler

Summary. During pro-oestrus, baseline LH concentrations for 9 vixens (pooled data) ranged from 0·8 to 5·3 ng/ml. In each vixen, baseline levels were interrupted by elevations of LH ranging from 3·1 to 10·4 ng/ml. A major preovulatory LH surge was detected in all the vixens. The LH peak ranged from 13·5 to 73·0 ng/ml with an average of 27·8 ± 18·8 (s.d.) ng/ml. Plasma LH concentrations declined to a basal level of 1·3 ± 1·0 ng/ml within 48 h of the peak value. The duration of the LH surge was 1–3 days. The LH peak occurred 1 or 2 days before any sexual receptivity was observed. All the vixens were mated twice 2–5 days after the LH peak; 8 conceived. Plasma concentrations of oestradiol-17β increased gradually during the last 6–7 days before oestrus and reached maximum values (124–373 pg/ml) at the time of the preovulatory LH peak. The first significant increase in plasma progesterone concentration occurred simultaneously with the LH peak. During oestrus (normally 3–5 days), progesterone levels rose steeply, attaining a mean concentration of 57·0 ± 17·5 ng/ml when the vixens went out of heat. Androstenedione and testosterone values changed similarly, both increasing at the beginning of pro-oestrus and reaching maximum values (805–1879 pg/ml and 328–501 pg/ml respectively) 1 day before to 1 day after the oestradiol-17β peak.

The electrical resistance of the vaginal tract increased rapidly during the last 2–3 days of pro-oestrus, reaching a maximum value (300–640 Ω) ~2 days after the oestradiol-17β peak that corresponded with the onset of sexual receptivity. Towards the end of oestrus, the values fell to 100–200 Ω.

Free access

A. J. Smith, M. Mondain-Monval, K. Andersen Berg, P. Simon, M. Forsberg, O. P. F. Clausen, T. Hansen, O. M. Møller and R. Scholler

Summary. Melatonin administration to male blue foxes from August for 1 year resulted in profound changes in the testicular and furring cycles. The control animals underwent 5-fold seasonal changes in testicular volume, with maximal values in March and lowest volumes in August. In contrast, melatonin treatment allowed normal redevelopment of the testes and growth of the winter coat during the autumn but prevented testicular regression and the moult to a summer coat the following spring. At castration in August, 88% of the tubular sections in the testes of the controls contained spermatogonia as the only germinal cell type, whereas in the treated animals 56–79% of sections contained spermatids or even spermatozoa. Semen collection from a treated male in early August produced spermatozoa with normal density and motility.

Measurement of plasma prolactin concentrations revealed that the spring rise in plasma prolactin values (from basal levels of 1·6–5·4 ng/ml to peak values of 4·1–18·3 ng/ml) was prevented; values in the treated animals ranged during the year from 1·8 to 6·3 ng/ml. Individual variations in plasma LH concentrations masked any seasonal variations in LH release in response to LHRH stimulation, but the testosterone response to LH release after LHRH stimulation was significantly higher after the mating season in the treated animals, indicating that testicular testosterone production was maintained longer than in the controls.

The treated animals retained a winter coat, of varied quality and maturity, until the end of the study in August.

Free access

J Lüttgenau, B Möller, D Kradolfer, O Wellnitz, R M Bruckmaier, A Miyamoto, S E Ulbrich and H Bollwein

Lipopolysaccharide (LPS), the endotoxin of Gram-negative bacteria, has detrimental effects on the structure and function of bovine corpus luteum (CL) in vivo. The objective was to investigate whether these effects were mediated directly by LPS or via LPS-induced release of PGF. Bovine ovaries with a mid-cycle CL were collected immediately after slaughter and isolated perfused for 240 min. After 60 min of equilibration, LPS (0.5 μg/ml) was added to the medium of five ovaries, whereas an additional six ovaries were not treated with LPS (control). After 210 min of perfusion, all ovaries were treated with 500 iu of hCG. In the effluent perfusate, concentrations of progesterone (P4) and PGF were measured every 10 and 30 min, respectively. Punch biopsies of the CL were collected every 60 min and used for RT-qPCR to evaluate mRNA expression of receptors for LPS (TLR2, -4) and LH (LHCGR); the cytokine TNFA; steroidogenic (STAR, HSD3B), angiogenic (VEGFA 121, FGF2), and vasoactive (EDN1) factors; and factors of prostaglandin synthesis (PGES, PGFS, PTGFR) and apoptosis (CASP3, -8, -9). Treatment with LPS abolished the hCG-induced increase in P4 (P≤0.05); however, there was a tendency (P=0.10) for increased release of PGF at 70 min after LPS challenge. Furthermore, mRNA abundance of TLR2, TNFA, CASP3, CASP8, PGES, PGFS, and VEGFA 121 increased (P≤0.05) after LPS treatment, whereas all other factors remained unchanged (P>0.05). In conclusion, reduced P4 responsiveness to hCG in LPS-treated ovaries in vitro was not due to reduced steroidogenesis, but was attributed to enhanced apoptosis. However, an impact of luteal PGF could not be excluded.