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1.
Reasons for performing study: The foal requires an active hypothalamo‐pituitary‐adrenal (HPA) axis for organ maturation and post natal survival. Prenatal administration of synthetic glucocorticoids may provide an effective method for inducing fetal maturation safely in the mare. Objectives: To determine whether dexamethasone administered to late pregnant mares: 1) will induce fetal maturation and precocious delivery; 2) is safe to use and 3) to identify endocrine responses in the mare and foal. Methods: Pregnant Thoroughbred mares received either 100 mg dexamethasone i.m. (treated n = 5) or 50 ml saline i.m. (control n = 5) at 315, 316 and 317 days of gestation. Plasma progestagens, cortisol and prostaglandin F2α metabolite (PGFM) concentrations were measured before and after treatment. The foals were weighed, the crown‐rump length (CRL) measured and an adrenal stimulation test performed on Day 1. Results: Dexamethasone significantly (P<0.01) reduced gestation length in treated mares without apparent adverse effects. Plasma progestagens increased (P<0.05), and cortisol and PGFM (P<0.05) decreased, following dexamethasone treatment compared with control mares. Foals were clinically mature but those from dexamethasone treated mares had reduced (P<0.05) CRL, but not bodyweights, compared with controls. Their cortisol concentrations increased following exogenous adrenocorticotrophic hormone stimulation but 2 foals from dexamethasone treated mares showed evidence of adrenal suppression. Conclusions: Dexamethasone stimulates precocious fetal maturation and delivery in healthy late pregnant mares. However, fetal HPA activity may be suppressed. Potential relevance: Dexamethasone treatment could be used to improve foal viability in mares at risk of preterm delivery. The endocrine effects of such a therapy must be evaluated before clinical intervention with glucocorticoids can be recommended.  相似文献   

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4.
The embryo of the domestic fowl (Gallus domesticus) tenders one distinctive advantage over general mammalian models for investigating the development of the hypothalamo–pituitary–adrenocortical (HPA) axis. This is the relative simplicity with which the embryonic endocrine environment can be influenced without confounding maternal influences. The ease of direct manipulation of the embryonic endocrine system has facilitated analysis of the development and function of the HPA axis in the chick embryo. As the chick embryo develops, functional activation of the adrenal gland is regulated at three different levels: the adrenal gland itself, the anterior pituitary, and the hypothalamus. The adrenal gland appears capable of independent secretion of glucocorticoids from day 8 until shortly after day 14 of embryonic development, at which point the pituitary influences adrenocortical activity. Around the same age, the hypothalamic level of control also begins. The information covered in this review will describe the major steps in the development of the HPA axis in the chicken embryo and show that the chicken has an emblematic HPA neuroendocrine axis.  相似文献   

5.
In our research we focused our attention on the effect of the immune stress induced by bacterial endotoxin–lipopolysaccharide (LPS) on the hypothalamic–pituitary–gonadal axis (HPG) at the pituitary level. We examined the effect of intravenous (i.v.) LPS injection on luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) release from the anterior pituitary gland (AP) in anestrous ewes. The effect of endotoxin on prolactin and cortisol circulating levels was also determined. We also researched the effect of immune challenge on the previously mentioned pituitary hormones and their receptors genes expression in the AP. Our results demonstrate that i.v. LPS injection decreased the plasma concentration of LH (23%; p < 0.05) and stimulates cortisol (245%; p < 0.05) and prolactin (60%; p < 0.05) release but has no significant effect on the FSH release assayed during 6 h after LPS treatment in comparison with the control levels. The LPS administration affected the genes expression of gonadotropins’β‐subunits, prolactin and their receptors in the AP. Endotoxin injection significantly decreased the LHβ and LH receptor (LHR) gene expression (60%, 64%; p < 0.01 respectively), increased the amount of mRNA encoding FSHβ, FSH receptor (FSHR) (124%, 0.05; 166%, p < 0.01; respectively), prolactin and prolactin receptor (PRLR) (50%, 47%, p < 0.01; respectively). The presented, results suggest that immune stress is a powerful modulator of the HPG axis at the pituitary level. The changes in LH secretion could be an effect of the processes occurring in the hypothalamus. However, the direct effect of immune mediators, prolactin, cortisol and other components of the hypothalamic pituitary–adrenal (HPA) axis on the activity of gonadotropes has to be considered as well. Those molecules could affect LH synthesis directly through a modulation at all stages of LHβ secretion as well as indirectly influencing the GnRHR expression and leading to reduced pituitary responsiveness to GnRH stimulation.  相似文献   

6.
Abortion in mares can be a financially devastating event to horse owners and the equine industry. In this case report, we describe the gross, histopathological and microbiological findings associated with an abortion caused by Salmonella enterica subsp. arizonae, which should be considered in cases of abortion and metritis. Gross and histopathological evaluation of fetal and placental tissue were consistent with ascending septic placentitis resulting in fetal septicaemia. S. enterica subsp. arizonae was isolated from the placenta, lung and fetal gastric contents. Diagnosis was confirmed by MALDI-TOF MS. To our knowledge, this subspecies of S. enterica has not been previously reported as an isolate in a case of late-term equine abortion. A retrospective search of abortion cases at our institution was done, and no similar cases were identified for comparison. This case demonstrates S. enterica subsp. arizonae, although not previously reported as a cause of abortion in pregnant mares and uncommonly isolated from equids in the literature, may cause late-term abortions in susceptible animals. This pathogen should be considered in cases of abortion outbreaks on a farm and merits investigation of the carrier status of mares within a herd.  相似文献   

7.
There are no data available regarding the systemic (adverse) effects which might be induced by topical/dermal glucocorticoids (GCs) application in the horse. Besides their widespread use for the treatment of a variety of peripheral inflammatory disorders such as atopic dermatitis, eczemas or arthritis in the horse, their surreptitious application has become a concern in doping cases in competition/performance horses. Assessing both basal and ACTH‐stimulated plasma cortisol as well as basal ACTH concentrations following application of dexamethsone‐containing dermal ointment is necessary to determine influences on hypothalamus‐pituitary‐adrenal (HPA) axis. Ten clinically healthy adult standardbred horses (6 mares, 4 geldings) were rubbed twice daily each with 50 g dexamethasone‐containing ointment on a defined skin area (30 × 50 cm) for 10 days. RIA and chemiluminescent enzyme immuno‐metric assay were used to determine resting and ACTH‐stimulated plasma cortisol and basal ACTH concentrations, respectively. HPA feedback sensitivity and adrenal function were measured by a standard ACTH stimulation test. Dermal dexamethasone suppressed significantly the resting plasma cortisol level (to 75–98%) below baseline (P < 0.001) within the first 2 days and decreased further until day 10. ACTH stimulation test showed a markedly reduced rise in plasma cortisol concentrations (P < 0.001 vs. baseline). Plasma ACTH level decreased also during topical dexamethasone application. The number of total lymphocytes and eosinophil granulocytes was reduced, whereas the number of neutrophils increased. No significant change of serum biochemical parameters was noted. Dermal dexamethasone application has the potential to cause an almost complete and transient HPA axis suppression and altered leukocyte distribution in normal horses. The effects on HPA axis function should be considered in relation to the inability of animals to resist stress situations. The data further implicate that percutaneously absorbed dexamethasone (GCs) may cause systemic effects relevant to ‘doping’.  相似文献   

8.
Birds tend to adjust their behavior and physiology to changes in food availability in their environment. Seasonal fluctuation of food resources may act as an energetic challenge, augmenting hypothalamus–pituitary–adrenal axis (HPA axis) activity, leading to an increase in corticosterone concentrations and promoting the metabolism of energy stores. Plant invasions may alter seasonal food fluctuations by providing a food supply during scarce seasons. This could attenuate the energetic challenge, reducing HPA axis activity and the metabolism of reserves. Using a system with seasonal fluctuation in food availability, we tested if fruit supplementation by the invasive fleshy‐fruited Pyracantha angustifolia during the season of native fruit scarcity decreases the consumption of energy stores through activity attenuation of the HPA axis. We measured changes in body condition and circulating corticosterone (CORT) concentration in Turdus chiguanco occurring at sites both invaded and not invaded by P. angustifolia over 3 time periods that correspond to the periods prior to, during and after highest fruit production of the plant. Fruit scarcity in the ecosystem appears as an energetic challenge for T. chiguanco, given that body mass, fat score and residuals of body mass/tarsus length decreased during winter in a site not invaded by the exotic shrub. Conversely, the presence of the invasive plant seemed to attenuate the metabolism of energetic reserves, as we did not record changes in body condition in birds inhabiting the invaded site. Unexpectedly, plasma CORT concentration did not vary between sites or periods. Further evaluation is required to elucidate how enhanced body condition, resulting from the consumption of a fleshy‐fruited invasive plant, affects survivorship and reproductive performance in T. chiguanco.  相似文献   

9.
Recently, a new molecule, kisspeptin (Kp), and in particular Kisspeptin 10 (Kp10), was implicated in stimulating the hypothalamic–pituitary–gonadal axis. The aim of this study was to evaluate circulating Kp10 levels in the early post–partum period of the dairy cow. Blood samples were collected from 40 dairy cows, at 10 (T10), 12 (T12), 14 (T14) and 16 (T16) days after calving. Progesterone (P4) levels were evaluated using ELISA, and levels of oestrogens (E2) and Kp were evaluated using a radio‐immunologic method. After an initial plateau, Kp10 significantly increased at T14 and decreased at T16. The P4 and E2 mean serum values remained in the physiological range. It is likely that Kp10 enhanced hypothalamic GnRH release as well as pituitary gonadotropin secretion, thus promoting follicular growth and the increase in E2 levels, which might have further enhanced Kp10 release through a positive feedback loop. To our best knowledge, this is the first report on the range of Kp10 blood concentration during the early post–partum period in the dairy cow. The results of our study will increase our current understanding of the complex neuro‐endocrine crosstalk underlying the resumption of ovarian cyclicity in the dairy cow.  相似文献   

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11.
The influence of two topical dexamethasone applications (dermal and ototopical) on plasma insulin, glucose, thyroid hormone and cortisol levels was investigated in beagle dogs. Both treatments significantly decreased basal cortisol values, associated with exaggerated rise in insulin (∼50%), together with unchanged serum glucose levels. Dermal dexamethasone quickly decreased plasma thyroxin (T4) levels; whereas dexamethasone in ear drops gradually inhibited time-dependently T4 release (18–50%). Both formulations blunted plasma triiodothyronine (T3) levels but the response induced by dermal dexamethasone was stronger than by dexamethasone ear drops. Upon drug withdrawal, insulin secretion returned to baseline a week after treatment cessation, while cortisol, T4 and T3 levels did not reach baseline values. These results suggest that topical glucocorticoids unexpectedly trigger secondary hypothyroidism with concomitant suppression of hypothalamic–pituitary–adrenal axis but sensitize the endocrine pancreas, thus, their application needs careful evaluation for surprisingly different effects on endocrine stress axis activity.  相似文献   

12.
Macpherson, M. L., Giguère, S., Hatzel, J. N., Pozor, M., Benson, S., Diaw, M., Sanchez, L. C., Vickroy, T. W., Tell, L., Wetzlich, S., Sims, J. Disposition of desfuroylceftiofur acetamide in serum, placental tissue, fetal fluids, and fetal tissues after administration of ceftiofur crystalline free acid (CCFA) to pony mares with placentitis. J. vet. Pharmacol. Therap.  36 , 59–67. The objective of this study was to determine the pharmacokinetics of CCFA in mares with placentitis and evaluate the disposition of the drug in fetal fluids, fetal membranes, colostrum, and serum of foals. A secondary objective was to obtain pilot data regarding the efficacy of CCFA for improving foal survival in mares with placentitis. Twelve pregnant pony mares were enrolled in the study, inoculated with Streptococcus zooepidemicus, intracervically and assigned to one of three groups: CEFT (n = 3; administered CCFA only; 6.6 mg/kg, IM, q96h); COMBO (n = 6; administered combination therapy of CCFA, altrenogest, and pentoxifylline); UNTREAT (n = 3, no treatment). Treatment was initiated at the onset of clinical signs. Concentrations of desfuroylceftiofur acetamide (DCA), the acetamide derivative of ceftiofur and desfuroylceftiofur metabolites, were measured using high‐performance liquid chromatography. Maximum and minimum serum concentrations of DCA at steady state in treated mares were 2.40 ± 0.40 μg/mL and 1.06 ± 0.29 μg/mL, respectively. Concentration of DCA in colostrum was 1.51 ± 0.60 μg/mL. DCA concentrations in placenta and fetal tissues were very low (median = 0.03 μg/mL) and below the minimum inhibitory concentration of relevant pathogens. DCA was not detected in amniotic fluid or foal serum. Treatment did not appear to improve foal survival (CEFT: 0/3; COMBO: 2/6; UNTREAT: 2/3). Bacteria were recovered from the uterus of most mares postpartum and from blood cultures of most foals regardless of treatment.  相似文献   

13.
环核苷酸（cAMP／cGMP）与肉鸡内分泌及免疫功能的关系   总被引：3，自引：0，他引：3  
以艾维茵肉鸡为实验对象，研究了血清环核苷酸与肉鸡内分汔及免疫功能的关系。结果表明，以性法氏囊病病毒（IBDV）强毒株攻击后，肉鸡垂体－肾上腺轴活动加强，并发生针对IBDV的特异性免疫反应，血清cAMP与cGMP含量均上升，但cAMP/cGMP比值保持稳定，提示垂体－肾上腺轴活动加强使cAMP上升与抗IBDV特异性免疫细胞内效应大分子的合成有关，而cAMP/cGMP比值的稳定则是保持一种高阈平衡，以维持内环境的稳态。由于IBDV强毒株破坏了机体免疫系统，未经IBDV疫苗免疫的肉鸡cAMP、抗IBDV抗体和IL－2的上升幅度均比经IBDV疫苗免疫的肉鸡小。  相似文献   

14.
We describe here the gross and microscopic lesions in 18 experimentally induced and 120 natural Campylobacter abortions. In natural Campylobacter abortions, gross lesions were reported infrequently; placentitis was recorded in 6% and hepatic lesions in 4% of our field cases. Placentitis was the microscopic lesion identified most consistently in natural abortions (93%) and was often observed in association with abundant bacterial colonies in chorionic villi (54%) and less often with placental vasculitis (13%). In natural abortions, suppurative fetal pneumonia (48%), necrosuppurative hepatitis (16%), and purulent meningitis (7%) were also observed. The better-preserved specimens from experimentally induced abortions were utilized to define placental changes more precisely. Placentitis was identified in all 18 experimentally induced abortions and was observed most consistently in the chorionic villus stroma (100%), often accompanied by suppurative surface exudate (89%). An inflammatory infiltrate was less commonly identified in the cotyledonary hilus (39%) and intercotyledonary placenta (22%). Bacteria were visualized in H&E-stained sections in 89% of placentas from experimentally infected ewes, primarily as well-demarcated bacterial colonies within subtrophoblastic, sinusoidal capillaries (89%), in the cotyledonary villus stroma (89%), and within the cytoplasm of trophoblasts (22%). Transmission electron microscopy and immunohistochemistry confirmed that the vast majority of the well-demarcated bacterial colonies characteristic of Campylobacter abortion were within subtrophoblastic sinusoidal capillaries. The most characteristic microscopic lesions identified in cases of Campylobacter abortion in sheep were placentitis with placental bacterial colonies, placental vasculitis, and fetal pneumonia.  相似文献   

15.
Fertility of domestic roosters decreases at ∼50 wk of age. In a previous study on aging white leghorn roosters, low fertility was accompanied by low levels of both hypothalamic vasoactive intestinal peptide (VIP) and pituitary prolactin (PRL) mRNA expression; however, their role in aging broiler breeder rooster reproduction is still unclear. In this study we compared reproductive activities of young (35-wk-old) and aging (73-wk-old) broiler breeder roosters. Weekly semen volume; concentration and ejaculation grade; and concentrations of plasma testosterone, estradiol, and PRL were examined. Every other week, 10 roosters from each group were euthanized, their testes weighed, and hypothalamus and pituitary removed to determine mRNA expression of hypothalamic GnRH-I, pituitary FSH, pituitary LH, hypothalamic VIP, and pituitary PRL. Aging roosters had significantly lower testis weight and semen volume, sperm concentration, ejaculation grade and plasma testosterone and low hypothalamic GnRH-I, pituitary FSH, and pituitary LH mRNA expression than young roosters (P ≤ 0.05). Aging roosters had higher concentrations of plasma estradiol and PRL and higher hypothalamic VIP and pituitary PRL mRNA expression than young roosters (P ≤ 0.05). We suggest that PRL, which is known to inhibit the gonadal axis, and its releasing factor, VIP, play an important role in the reproductive failure associated with age in broiler breeder roosters.  相似文献   

16.
This study was conducted to examine the effects of weaning stress on gene expression of specific markers in hypothalamus‐pituitary‐adrenal (HPA) axis and neuronal activity in the newly weaned piglets. Twelve 28‐days‐old, newly weaned crossbred (Landrace × Yorkshire × Duroc) male piglets from 6 l (2 piglets/l) were randomly categorized into two groups: (a) weaning stress: piglets were separated from their dams, relocated and mixed with the unacquainted domestic piglets for 2 hr (stress, n = 6); (b) no‐stress: piglets stayed with their dams in the farrowing house (NS; n = 6). After weaning stress, all piglets were electrically euthanized and the blood samples/HPA tissues were collected for subsequent analysis, including plasma cortisol and mRNA expression of c‐fos, c‐jun, corticotropin‐releasing hormone (CRH), CRH receptor 1 (CRHR‐1) and adrenocorticotropin hormone receptor (MC2R). Results: Weaning stress significantly (p < 0.05) increased the plasma cortisol level and suppressed the expression of c‐fos and CRH in hypothalamus. In addition, weaning stress enhanced the mRNA abundance of c‐jun and CRHR‐1 in the pituitary gland. No significant differences in the gene expression of MC2R and CRHR‐1 were observed in the adrenal gland between treatment groups. Taken together, HPA involved in weaning stress and CRHR‐1 and c‐jun could be potential markers to evaluate the activation of HPA axis.  相似文献   

17.
The effects of prolonged, intermittent infusion of β‐endorphin or naloxone into the third cerebral ventricle of follicular‐phase ewes on the expression of genes encoding GnRH and GnRHR in the hypothalamus and GnRHR in the anterior pituitary gland (AP) were examined by an enzyme‐linked immunoabsorbent assay. Activation or blockade of μ‐opioid receptors significantly decreased or increased the GnRH concentration and GnRHR abundance in the hypothalamus, respectively, and affected in the same way GnRHR quantity in the AP gland. The changes in the levels of GnRH and GnRHR after treatment with β‐endorphin as well as following action of naloxone were reflected in fluctuations of plasma LH concentrations. On the basis of these results, it is suggested that β‐endorphinergic system in the hypothalamus of follicular‐phase ewes affects directly or via β‐endorphin‐sensitive interneurons GnRH and GnRHR biosynthesis leading to suppression in secretory activity of the hypothalamic‐pituitary axis.  相似文献   

18.
This study investigated whether a single intra‐articular administration (IA) of dexamethasone (DEX) in horses at therapeutic dosage could exert a systemic effect by influencing the hypothalamic‐pituitary‐adrenal axis activity as a consequence of (limited) absorption and systemic distribution. The results indicated that DEX was detectable in urine collected 12–48 h after IA administration and that injection was accompanied by a reduced urine excretion of cortisol, 6β‐hydroxycortisol (6βOHF) and two other metabolites of cortisol lasting up to 48 h post‐DEX administration. The systemic effects in horses treated with DEX by IA route are similar to those that typically occur with short‐term treatment including the reduction in urinary cortisol concentration.  相似文献   

19.
Our understanding of the development and progression of equine pituitary pars intermedia (PI) dysfunction has expanded over the last decade, although much remains to be explained. Degeneration of the hypothalamic periventricular dopaminergic neurons results in disinhibition of the endocrine cells of the PI, the melanotropes. As a result, the PI enlarges, compressing the adjacent lobes, the pars distalis and pars nervosa. The disinhibited melanotropes overproduce pro‐opiomelanocortin peptides, including α‐melanocyte stimulating hormone, β‐endorphin, corticotrophin‐like intermediate lobe peptide and adrenocorticotropin. The excess in PI hormones, perhaps in concert with a deficiency in other pituitary hormones, results in clinical signs of pituitary PI dysfunction. Evidence suggests both oxidative stress and accumulation of misfolded neuronal proteins contribute to damage to the periventricular neurons, although it is not clear if these pathologies actually initiate the disease or are downstream events.  相似文献   

20.
Choudhury, S., Garg, S. K., Singh, T. U., Mishra, S. K. Cellular coupling of potassium channels with β2 adrenoceptors in mediating myometrial relaxation in buffaloes (Bubalus bubalis). J. vet. Pharmacol. Therap. 33 , 22–27. Present study unravels the functional presence of potassium channels and their involvement in mediating β2 adrenoceptors‐induced myometrial relaxation in buffalo myometrium. Isolated myometrial preparations exhibited rhythmic spontaneity with regular pattern of amplitude and frequency. Levcromakalim produced concentration‐dependent inhibitory effect on myometrial spontaneity and relaxant effect and the dose–response curve (DRC) was shifted towards right in the presence of glybenclamaide. In the tissues pretreated with glybenclamide, relaxant effect of albuterol was significantly (P < 0.05–0.001) lower (pD2 = 6.94, Rmax = 96.8 ± 3.3%; n = 5) compared with albuterol alone (pD2 = 8.55, Rmax = 101.1 ± 6.3%; n = 6) and the DRC was shifted to right. In the presence of tetraethyl ammonium (TEA) also, significant (P < 0.001) rightward shift of DRC of albuterol with decrease in maximal effect (pD2 = 8.05, Rmax = 71.2 ± 7.4%; n = 7 vs. control pD2 = 8.55, Rmax = 101.1 ± 6.3%; n = 6) was observed. On the other hand, 4‐aminopyridine (1 mm ) sensitized the myometrial strips and increased the amplitude and frequency/min of myometrial spontaneity but failed to significantly alter the DRC of albuterol. Results of present study suggest the functional presence of KATP, BKCa and KV channels in buffalo myometrium, but β2‐adrenoreceptor agonist‐induced myometrial relaxation seems to be KATP and BKCa channel‐dependent only. Further, our studies also suggest promising therapeutic potential of potassium channel modulators as tocolytics in buffaloes.  相似文献   

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