RESUMO
Prenatal glucocorticoids, commonly used in women at risk of preterm delivery, can predispose the newborn to disease in later life. Since male reproductive function is likely to reflect testis development during fetal life, we studied the effects of prenatal glucocorticoids on two key intra-testicular factors that play roles in cellular proliferation and differentiation, 3ß-hydroxysteroid dehydrogenase (3ß-HSD) and inhibin-α. Pregnant sheep (n=42) were treated with betamethasone (0.5 mg/kg) or saline (control) at 104, 111 and 118 days of gestation (DG). Testicular tissue was sampled from fetuses at 121 and 132DG, and from lambs at 45 and 90 postnatal days (PD). Within the betamethasone treated group, 3ß-HSD immunostaining area was greater at 121DG than at 90PD (P=0.04), but the intensity of immunostaining was higher at 90PD than at 121DG (P=0.04), 132DG (P=0.04) and 45PD (P=0.03). Control animals showed no changes in 3ß-HSD area or intensity of immunostaining. No significant differences were observed between treated and control animals in immunostaining area, but immunostaining was more intense in the treated group than in the control group at 90PD (P=0.03). For inhibin-α, the proportion of immunostaining area declined in treated offspring from 121DG to 45PD, in contrast to control values, but recovered fully by 90PD, concomitantly with the onset of spermatogenesis. In conclusion, prenatal betamethasone increased the postnatal testicular expression of inhibin-α but reduced the expression of 3ß-HSD. These effects could compromise androgen-mediated testicular development and therefore adult capacity for spermatogenesis.
Assuntos
17-Hidroxiesteroide Desidrogenases/metabolismo , Betametasona/farmacologia , Feto/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Inibinas/metabolismo , Testículo/metabolismo , Animais , Feminino , Feto/citologia , Feto/efeitos dos fármacos , Idade Gestacional , Técnicas Imunoenzimáticas , Masculino , Gravidez , Ovinos , Testículo/efeitos dos fármacos , Testículo/crescimento & desenvolvimentoRESUMO
In sheep production systems based on extensive grazing, neonatal mortality often reaches 15% to 20% of lambs born, and the mortality rate can be doubled in the case of multiple births. An important contributing factor is the nutrition of the mother because it affects the amount of colostrum available at birth. Ewes carrying multiple lambs have higher energy requirements than ewes carrying a single lamb and this problem is compounded by limitations to voluntary feed intake as the gravid uterus compresses the rumen. This combination of factors means that the nutritional requirements of the ewe carrying multiple lambs can rarely be met by the supply of pasture alone. This problem can overcome by supplementation with energy during the last week of pregnancy, a treatment that increases colostrum production and also reduces colostrum viscosity, making it easier for the neonatal lamb to suck. In addition, litter size and nutrition both accelerate the decline in concentration of circulating progesterone that, in turn, triggers the onsets of both birth and lactogenesis, and thus ensures the synchrony of these two events. Furthermore, the presence of colostrum in the gut of the lamb increases its ability to recognize its mother, and thus improves mother-young bonding. Most cereal grains that are rich in energy in the form of starch, when used as supplements in late pregnancy will increase colostrum production by 90% to 185% above control (unsupplemented) values. Variation among types of cereal grain in the response they induce may be due to differences in the amount of starch digested post-ruminally. As a percentage of grain dry matter intake, the amount of starch entering the lower digestive tract is 14% for maize, 8.5% for barley and 2% for oats. Supplements of high quality protein from legumes and oleiferous seeds can also increase colostrum production but they are less effective than cereal grains. In conclusion, short-term supplementation before parturition, particularly with energy-rich concentrates, can improve colostrum production, help meet the energy and immunological requirements for new-born lambs, and improve lamb survival.
Assuntos
Colostro/fisiologia , Necessidades Nutricionais , Carneiro Doméstico/fisiologia , Ração Animal/análise , Fenômenos Fisiológicos da Nutrição Animal , Animais , Dieta/veterinária , Suplementos Nutricionais/análise , FemininoRESUMO
Pre-natal glucocorticoids are used in women at risk of preterm delivery to induce foetal lung maturation. However, glucocorticoids can produce negative outcomes for other tissues such as the reproductive system. We therefore tested the effects of pre-natal betamethasone on testicular morphology and apoptotic protein immune expression during pre- and post-natal development. Pregnant ewes (n = 42) bearing singleton male foetuses were randomly allocated to receive intramuscular injections of saline or betamethasone (0. 5 mg/kg) at 104, 111 and 118 days of gestation (DG). Testes were collected at 121 and 132 DG, and at 45 and 90 post-natal days (PD) and subjected to morphometric analysis (volume densities of sex cords and interstitial tissues; sex cord diameter). Immunohistochemistry (% stained area) was used to assess active caspase-3, Bax, Bcl-2 and cell-cycle proteins (PCNA). Compared with control values, betamethasone treatment decreased sex cord diameter at 121 DG, 45 and 90 PD, and sex cord volume at 90 PD. Active caspase-3 was decreased by betamethasone at 121 DG and 90 PD, but Bax was increased in all betamethasone groups. Bcl-2 and PCNA decreased in the betamethasone groups at 121 DG and 45 PD, but increased at 132 DG and 90 PD. We conclude that high levels of pre-natally administered glucocorticoid reduce foetal testicular development, perhaps via changes in the balance between pro- and anti-apoptotic proteins and cell-cycle proteins. These outcomes could compromise the future spermatogenic potential of male offspring.
Assuntos
Apoptose/fisiologia , Betametasona/farmacologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal , Ovinos/crescimento & desenvolvimento , Testículo/efeitos dos fármacos , Animais , Betametasona/administração & dosagem , Feminino , Glucocorticoides/administração & dosagem , Glucocorticoides/farmacologia , Masculino , Gravidez , Testículo/crescimento & desenvolvimento , Testículo/metabolismoRESUMO
We tested the hypothesis that acute pre-natal exposure to high levels of synthetic glucocorticoid (betamethasone) would alter fetal testicular development through actions on gonadal glucocorticoid receptors (GRs). Pregnant Merino ewes bearing singleton male fetuses (n = 24) were allocated randomly among four equal groups to be injected intramuscularly with saline or betamethasone (0.5 mg/kg) either on day 109 of gestation or on both day 109 and day 116 of gestation. Fetal testes were collected at post-mortem, 5 days after each treatment. The volume of interstitial tissue and the volume, length and diameter of the sex cords were measured, and Sertoli cells and gonocytes were counted. For cord volume and interstitial tissue volume, control testes demonstrated maturational changes as fetal age advanced from 109 to 116 days of gestation. For that period, the single injection of betamethasone significantly reduced Leydig cell proliferation (P < 0.05), but had no effect on Sertoli cell numbers. Immunohistochemistry was used to localize GR and proliferating cell nuclear antigen in testicular cells. GR immunoexpression in Leydig cells was higher in fetuses exposed to betamethasone at 109 days of gestation than in control fetuses. Sertoli cells showed low levels of GR. It was concluded that, during mid-gestation, a brief period of glucocorticoid treatment could affect testicular development in male sheep fetuses. The mechanism probably involves direct effects on Leydig cells, as these cells express extra-GR in response to the treatment. Sertoli cells seem to produce less GR than Leydig cells, perhaps explaining their lack of response to betamethasone. These outcomes may have important implications for future fertility in male offspring.
Assuntos
Betametasona/farmacologia , Glucocorticoides/farmacologia , Receptores de Glucocorticoides/efeitos dos fármacos , Ovinos/embriologia , Testículo , Animais , Contagem de Células , Divisão Celular/efeitos dos fármacos , Divisão Celular/fisiologia , Tamanho Celular , Feminino , Idade Gestacional , Células Intersticiais do Testículo/efeitos dos fármacos , Células Intersticiais do Testículo/fisiologia , Masculino , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Distribuição Aleatória , Células de Sertoli/citologia , Células de Sertoli/efeitos dos fármacos , Células de Sertoli/fisiologia , Testículo/citologia , Testículo/efeitos dos fármacos , Testículo/embriologia , Testículo/crescimento & desenvolvimentoRESUMO
The present study was conducted to determine if the social status of Australian Cashmere goats affects their response to the male effect in terms of LH secretion, ovulation and expression of estrus. Australian Cashmere goats were kept isolated from the males during 5 months. The index of success (SI) of each goat was calculated to establish their social rank. In the first experiment, the ten most dominant and the 10 most subordinate goats were separated from the original herd and housed in two pens (5 dominant and 5 subordinate animals in each pen). An androgenized wether was then introduced into each pen. Luteinizing hormone (LH) was measured every 20 min from 2h before to 4h after introduction of the male in the goats of first pen and from 4 to 8h after male introduction in the second pen. In the second experiment, the remaining 50 goats were exposed in their original pen to two androgenized wethers. Their association index with the males (AI) was calculated for each of these 50 goats, and the intervals from exposure to the males to the onset of estrus and to ovulation were determined. During the first 4h after male introduction, the dominant goats had more LH pulses (0.65+/-0.06 compared with 0.3+/-0.09; P<0.05) and greater LH mean concentrations (1.79+/-0.14 ng/ml compared with 1.30+/-0.15 ng/ml, P=0.05) than the subordinate animals. Although not significantly different, the AI was 35% greater for high and medium ranking goats than for low ranking animals (0.031+/-0.004, 0.032+/-0.005 and 0.023+/-0.005, respectively, P>0.05). Although the number of goats ovulating in response to male exposure was similar between dominance groups (high: 100%, medium: 94% and low ranking: 92%), the high and medium dominance goats showed a greater incidence of expression of estrus than low-dominance goats (94.4%, 89.5% and 53.8%, respectively, P<0.05). It is concluded that the social rank of the Australian Cashmere goat influences their response to the male effect in terms of early LH secretion and expression of estrus.
Assuntos
Cabras/fisiologia , Comportamento Sexual Animal/fisiologia , Predomínio Social , Animais , Austrália , Estro , Feminino , Inseminação Artificial/veterinária , Hormônio Luteinizante/metabolismo , Masculino , Ovulação , Caracteres Sexuais , Fatores de TempoRESUMO
This study tested whether the effects of a short period of nutritional supplementation given to ewes during the luteal phase on follicle development and ovulation rate is associated with an increase in circulating concentrations of FSH, glucose or metabolic hormones. Oestrus was synchronised with two prostaglandin injections given 9 days apart and the supplement consisted of corn grain and soybean meal. Corriedale ewes with low body condition were randomly assigned to 2 groups: the control group (C; n = 10) received a maintenance diet while the short-term supplemented group (STS; n = 10) received double the maintenance diet over days 9 to 14 of the oestrous cycle (day 0 = ovulation). Ovaries were examined daily by ultrasound and blood was sampled three times a day during the inter-ovulatory interval for measuring reproductive and metabolic hormones. On days 9, 11 and 14 of the oestrous cycle, half of the ewes from each group (n = 5) were bled intensively to determine the concentrations of glucose, insulin, IGF-I and leptin. Plasma FSH, progesterone, oestradiol and androstenedione concentrations were similar among groups. Dietary supplementation increased plasma insulin concentrations from the first to the sixth day of supplementation and increased glucose concentrations on the third day, compared with control ewes. Plasma leptin concentrations were higher in STS ewes from the second to the fifth day of supplementation. The pattern of IGF-I concentrations was similar among groups. In STS ewes, the nutritional treatment prolonged the lifespan of the last non-ovulatory follicle, so fewer follicular waves developed during the cycle. In STS ewes, increased concentrations of glucose, insulin and leptin one day before ovulatory wave emergence were associated with increased numbers of follicles growing from 2 to 3 mm and with stimulation of the dominant follicle to grow for a longer period. We suggest that the mechanism by which short-term nutritional supplementation affects follicle development does not involve an increase in FSH concentrations, but may involve responses to increased concentrations of glucose, insulin and leptin, acting directly at the ovarian level. This effect is acute, since concentrations of all three substances decrease after reaching peak values on the third day of supplementation. The status of follicle development at the time of maximum concentrations of glucose and metabolic hormones may be one of the factors that determines whether ovulation rate increases or not.