PubMed Health⌕ Search

Biomedical subjects

L V Osadchuk

Publications and source records attributed to L V Osadchuk.

At least 19 recordsLinked to original sources
PubMed2001

Handling during pregnancy in the blue fox (Alopex lagopus): the influence on the fetal pituitary-adrenal axis.

Previous studies revealed that handling is a stressor for farmed blue foxes. The present study was designed to examine the effects of a 1-min daily handling stress applied to pregnant blue fox vixens on the function of the fetal pituitary-adrenal system. Plasma concentrations of adrenocorticotropin hormone (ACTH), cortisol, and progesterone, adrenal content of cortisol and progesterone, in vitro adrenal production of these steroids and response to ACTH, and adrenal weights were measured in control (C; n = 73) and stressed (S; n = 58) fetuses. The ACTH levels were lower in stressed fetuses than in the controls (C: males, 128.6 +/- 6.1 pg/ml; females, 165.9 +/- 6.1 pg/ml; S: males, 122.3 +/- 5.4 pg/ml; females, 145.0 +/- 8.1 pg/ml; P < 0.05). In contrast, increased plasma cortisol concentrations in both sexes were demonstrated in stressed compared with control fetuses (C: males, 9.2 +/- 0.4 ng/ml; females, 9.2 +/- 0.4 ng/ml; S: males, 11.8 +/- 0.7 ng/ml; females, 13.2 +/- 0.7 ng/ml; P < 0.00001). The same difference was observed in plasma progesterone concentrations (C: males, 1.54 +/- 0.07 ng/ml; females, 1.49 +/- 0.10 ng/ml; S: males, 1.86 +/- 0.11 ng/ml; females, 1.74 +/- 0.10 ng/ml; P < 0.01). Prenatal stress did not change the baseline adrenal production of cortisol but prevented the cortisol response to ACTH in female fetuses and decreased the progesterone production in both sexes. Additionally, prenatally stressed fetuses of both sexes had significantly lower adrenal weights than controls (C: males, 9.4 +/- 0.3 mg; females, 9.5 +/- 0.4 mg; S: males, 8.1 +/- 0.3 mg; females, 8.2 +/- 0.4 mg; P < 0.001). These results indicate that prenatal handling stress induces a dysregulation of the pituitary-adrenal axis in the fetus and suggest that increased plasma glucocorticoids in the stressed dam can cross the placenta and influence the fetal hypothalamicpituitary-adrenal axis.

Adrenal Glands↗
PubMed2000

Effect of restricted food intake on production, catabolism, and effects of IGF-I and cyclic nucleotides in cultured ovarian tissue of domestic nutria (Myocastor coypus).

The aims of these in vitro experiments were to examine the effects of short-term food restriction on ovarian secretory activity and the role of IGF-I and cAMP- and cGMP-dependent intracellular mechanisms in the control of ovarian function in domestic nutria. Slices of ovary from sexually mature animals kept under conditions of normal and restricted ((1/2) of standard ration) feeding were cultured with or without IGF-I (50 ng/ml), cAMP analogues (dbcAMP and Rp-cAMPS), and cGMP analogues (8-pCPT-cGMP and Rp-8-Br-PET-cGMPS; all at 100 nM). In nonovarian cells dbcAMP activates and Rp-cAMPS inhibits protein kinase A, while 8-p-CPT-cGMP activates and RP-8-Br-PET-cGMPS inhibits protein kinase G and cGMP-gated ion channels. IGF-I release and catabolism, as well as the release of progesterone (P), estradiol (E), and cAMP by the cultures, were evaluated using RIA. IGF-I did not affect cAMP release, while each of the cAMP and cGMP analogues inhibited IGF-I release in both control and experimental groups. Fasting did not affect cAMP or IGF-I release. It partially prevented the effect of Rp-cAMPS, but not of other cyclic nucleotides, on IGF-I release and inhibited IGF-I catabolism. The Rp-cAMPS and Rp-8-Br-PET-cGMPS also inhibited IGF-I catabolism and the effects were greater with tissue from food-restricted than control animals. Ovaries from the underfed nutria secreted significantly more P and less E than those from normally fed animals. IGF-I and both cAMP analogues, given alone, did not affect P release whereas a combination of IGF-I and Rp-cAMPS increased P output in control, but not in the experimental group. The 8-pCPT-cGMP had no effect P release. Rp-8-Br-PET-cGMPS, given alone or in combination with IGF-I, dramatically increased P secretion by tissue from control but not underfed animals. Estradiol secretion by tissue from underfed animals was stimulated by IGF-I, dbcAMP, Rp-cAMPS, 8-pCPT-cGMP, and Rp-8-Br-PET-cGMPS as well as by combinations of IGF-I and Rp-cAMPS or Rp-8-Br-PET-cGMPS; these effects were not seen with control tissue. The results demonstrate that: (1) ovaries of domestic nutria secrete IGF-I, P, E, and cAMP; (2) cAMP and cGMP can influence IGF-I release and catabolism; (3) the cyclic nucleotides may have an IGF-I-mediated effect on P and E output; (4) IGF-I and cyclic nucleotides can prevent the effect of undernutrition on E, but not on P release; (5) effects of cAMP and cGMP on P and E are probably not mediated by protein kinase A, protein kinase G, or cGMP-gated ion channels; and (6) food restriction can influence ovarian IGF-I catabolism, P, and E release and modulate the effects of cyclic nucleotides and IGF-I on steroidogenesis. It is concluded that ovarian secretory activity may be regulated separately by nutrition and the cyclic nucleotide-IGF-I system, and there may be functional interrelationships between these mechanisms.

Animals↗
PubMed1998

[Biosynthesis of testosterone in the gonads in silver fox embryos after long-term selection for domesticated behavior].

Fetal gonad weight and testosterone content in serum and gonads were analyzed in silver fox every five days from the 35th day of pregnancy until delivery. Fetal testicles were also tested for testosterone production induced by chorionic gonadotropin (CG) in vitro. Pregnant females were sampled from an experimental population subjected to selection for domesticated behavior and a commercial population (control). Fetal gonad weight was significantly lower in domesticated animals than in controls. No differences were revealed in the testosterone contents in their serum and gonads and in the basal production of testosterone in fetal testicles. CG-induced production of testosterone was detectable from the 40th day of fetal development in domesticated animals and from the 50th day in controls. The results obtained suggest that domestication results in the hetero-chronic fetal development of the hypophysial-testicular complex in silver fox.

Animals↗
PubMed1997

Cortisol production in fetal adrenals of the silver fox.

The present study was designed to examine cortisol production by the silver fox fetal adrenals and their response to ACTH at different periods of prenatal life. Serum levels of cortisol were determined on days 35, 40, 45 and 50 of gestation (term on day 52) in embryos of both sexes. Cortisol content in adrenal tissue homogenates and its in vitro adrenal production were also investigated at the same time points. Hormones were measured by RIA. The levels of cortisol changed slightly during embryonic life. The adrenal content and the in vitro production of cortisol increased sharply and progressively (by 4-10 times from days 35 to 50 of gestation). The rises in cortisol content and in vitro production were associated with a rapid growth of the fetal adrenals. There were no sex differences in cortisol level and its adrenal content. ACTH (50 mIU per sample) increased the in vitro cortisol production by the adrenals in the two sexes on all the studied days (by 3-4 times on day 35 and by 1.4-1.7 times on day 50). These results indicate that 1) silver fox fetal adrenals are capable of synthesising cortisol; 2) ACTH is a potent activator of the in vitro cortisol production during embryonic life in this species.

Journal Article↗
PubMed1997

[Phenogenetic analysis of prenatal development of the glucocorticoid function of the adrenals in silver foxes after long-term selection for domesticated behavior].

The level of cortisol in serum and adrenals and its production by adrenals in vitro was studied by the radioimmune method in male and female silver fox embryos, starting from day 30 of pregnancy every five days. Pregnant females from a commercial population and an experimental population, which had been selected for domestic behavior, was used. It was shown that, at the end of the prenatal developmental stage, all investigated parameters of the glucocorticoid function of adrenals were significantly lower in embryos from selected mothers as compared to the unselected control group. The addition of adrenocorticotropic hormone into the incubation medium increased cortisol biosynthesis at all embryogenesis stages, but in the selected population the increase was less than that in the control group.

Adrenal Glands↗
PubMed1997

[Sexual activity and anomalous spermatogenesis in young male silver foxes].

The total number of spermatozoa in ejaculate of males with normal sexual activity was 165,647,5 million and the mean percentage of morphologically abnormal spermatozoa was 21,64,4%. The percentage of morphologically defective spermatozoa in sexually inactive males was significantly lower than in sexually active ones.

Animals↗
PubMed1997

[Effect of long-term selection for behavior on progesterone level in blood and its level in adrenal glands of silver fox embryos].

The level of progesterone in blood serum and its concentration in adrenals and gonads have been assayed in male and female silver fox embryos, starting from day 35 of pregnancy for every five days. Pregnant females from an experimental population, selected for the domestic type of behavior and, as a control group, females from a commercial population, were used. At the end of prenatal development (days 45-50) the concentration of progesterone in adrenals was show to be significantly lower in embryos from mothers of the selected population, than in the unselected control group. On the contrary, the domesticated and wild animals did not differ in the level of progesterone in blood. The results suggest that selection of animals for domestic behavior decreases the synthesis of progesterone by embryonic adrenal glands.

Adrenal Glands↗
PubMed1995

Gonadal function in mink under artificial photoperiods.

Exposure of juvenile minks to artificial light conditions imitating early autumn (additional illumination from 20 June to 20 July followed by 8 h daylight from 21 July to 10 October--photoperiod I; 8 h daylight from 21 July to 10 October--photoperiod II) induced the prolonged modification of sex steroid concentrations. The increase in plasma testosterone concentrations during the prepubertal period was followed by a decrease before and during the mating period in experimental males. The concentration of oestradiol in plasma increased just before the start of the mating period (January and February) in females under photoperiod I, and these hormonal changes were accompanied by an increase in fertility. The conditions of photoperiod II (involving fewer hours of daylight) had less effect on the sex steroid concentration in the blood of females, and fertility was not changed. The response of gonads to hCG injection at the beginning of puberty (November) was higher in males exposed to photoperiod I conditions and in females exposed to both photoperiods than in control animals.

Animals↗
PubMed1994

Testosterone production in fetal testes of the silver fox.

Testosterone content was studied in fetal serum and testes of silver foxes during different periods of prenatal life. The first sign of testosterone synthesis in the testes could be detected starting from the 31st day of gestation by radioimmunoassay. Subsequently its content sharply increased and showed maximum value on the 50th day. Detectable serum testosterone level in male silver fox fetus was noted from the 40th day, its serum concentration increased in prenatal life, but only insignificantly. Testicular production of testosterone was stimulated by hCG at the stages studied from Day 40 on. It is supposed that silver fox testes were able to respond to gonadotrophin not earlier than by Day 40 of prenatal life, but the establishment of pituitary-testicular interrelationship was clearly demonstrated at the end of embryogenesis (Day 50).

Journal Article↗
PubMed1992

[Sex steroid hormones and brain serotonin in the estrous cycle of silver foxes].

A significant increase in hypothalamic serotonin and estradiol levels was found in silver foxes during proestrus. During estrus, the plasma estradiol concentration was reduced and a significant increase in progesterone level was correlated with a decrease in the brain serotonin content. The data obtained suggest that the brain serotonin plays a mediating role in the control of ovarian hormonal activity and ovulation in silver foxes.

Animals↗
PubMed1990

[Hormones, reproductive behavior and fertility in male silver foxes].

The relationships between gonadal and glucocorticoid hormones and reproductive behaviour were estimated in two groups of silver fox males classified as either low or high sex activity. Levels of testosterone and cortisol in peripheral plasma measured by radioimmunoassay did not differ between the groups. However, when receptive females were introduced to experimental males, levels of testosterone in plasma increased significantly only in the males with high sex activity within 1 hr after a test of sexual behaviour. Low sex activity of silver fox males correlated with an increased level of aggressive behaviour and decreased fertility.

Agonistic Behavior↗
PubMed1988

[Effect of adrenocorticotropin on the progesterone level in the peripheral blood and on adrenal progesterone production in vitro in female silver foxes].

The plasma progesterone increased following a single injection of ACTH (3 ME/kg). The progesterone production was also increased by ACTH after incubation of adrenals in vitro. The data suggest that the adrenal glands of female silver foxes are capable not only of secreting progesterone, but also of responding to ACTH with a further increase in the progesterone secretion.

Adrenal Glands↗
PubMedDate not supplied

[The effect of the photoperiod on steroid hormone secretion, on seasonal reproductive rhythms and on fertility in female silver foxes].

The silver fox is a strictly seasonal breeder and photoperiod is a main factor that regulates reproduction in this species. The aim of the present work was to study the effects of different skeleton photoperiods on the induction of early estrus, hormonal activity of gonads and fertility in anestrous silver foxes. Adult females (n = 48) were exposed to short days (9.5L:14.5D) from September until March. Females (n = 12) kept under the natural daylight conditions served as the control. The experimental groups received illumination in two fractions: 7- and 2.5-hour long. The 7-hour period comprised natural daylight from 10:00 to 17:00 and an additional light pulse at night (00-02:30, group 1), in the morning (06:00-08:30, group 2) and in the evening (17:30-20:00, group 3). There are three types of response in group 1. A half of animals showed signs of estrus in November-December, 2.5-3.0 months before the natural reproductive season. The second part displayed no changes until the end of the experiment indicating photorefractoriness. The third part had estrus during the natural reproductive season. Photoperiod 2 and 3 did not affect the temporal pattern of reproductive rhythm. All artificial photoperiods increased the estradiol level and decreased the progesterone, cortisol and testosterone levels during the anestrous phase and suppressed the ovarian hormonal activity during the follicular and luteal phases but photoperiod 1 had the most pronounced effects. Fertility was decreased in all experimental groups. Our results suggest that the photoperiod with a light pulse at night can induce early estrus and ovarian hormonal activity in anestrous females. The data obtained suggest that decreased fertility under these conditions could be due to altered ovarian hormonal secretion.

Animals↗
PubMedDate not supplied

[The effect of prenatal stress on steroidogenesis in the gonads of Arctic foxes (Alopex lagopus)].

Handling is a source of stress for farm-bred blue foxes. The influence of handling during the late gestational period was investigated in 10-day old male and female blue foxes. Testosterone and estradiol were measured by RIA in the plasma, gonadal homogenates and in vitro incubates from blue foxes of both sexes. The gonads were incubated in vitro without or with human chorionic gonadotropin. In cubs of both sexes, the gonad weights and ovarian estradiol production were decreased by stress. The testicular testosterone and ovarian estradiol contents were increased in prenatally stressed cubs as compared to the controls. The testicular content and baseline in vitro production of testosterone were not affected by prenatal stress, but the testicular response to human chorionic gonadotropin was higher in the stressed group. This study suggests that prenatal stress induced by handling pregnant vixens may influence gonadal steroidogenesis and this effect was more pronounced in female cubs.

Analysis of Variance↗
PubMedDate not supplied

[Sex-related differences in blood and gonad levels of testosterone in silver fox fetuses].

The mass of silver fox fetuses of both sexes, their gonads, and adrenals, and the levels of testosterone in blood serum and in gonads and adrenals were determined from day 31 of gestation and every five days thereafter until its termination. Marked sex-related differences were revealed: the blood and gonad levels of testosterone in male fetuses were much higher than those in female fetuses. The fetal adrenals contained significantly less testosterone than the gonads. No sex-related differences in the content of testosterone in the fetal adrenals were found. No differences were found in the body and adrenal mass in female and male fetuses at all the developmental stages studied, while the mass of ovaries exceeded that of testes from day 45 of gestation. The data obtained suggest sex dimorphism in the production of testosterone by gonads in silver foxes appears after day 35 and appears to correspond to the period of morphological differentiation of gonads.

Adrenal Glands↗