Equine pituitary pars intermedia dysfunction (PPID) is a common and serious condition that gives rise to Cushing's disease. In the older horse, it results in hyperadrenocorticism disrupted energy metabolism, severity of which varies with time year. To gain insight into mechanism its pathogenesis, 24-h profiles for peripheral plasma melatonin, serotonin, dopamine cortisol concentrations were determined at winter summer solstices, autumn spring equinoxes six horses diagnosed disease matched...

The present study examines the ovulatory activity of wild and domesticated ewes subjected to either a constant photoperiod long days (16L:8D) or natural changes in daily for 16 mo. aim was determine whether an endogenous reproductive rhythm controls seasonal these sheep, how might affect this. effects long-day photoperiods on long-term prolactin melatonin secretion were also evaluated. two species showed under conditions, suggesting existence reproduction. This differently expressed types...

Seasonal changes in mammalian physiology, such as those affecting reproduction, hibernation, and metabolism, are controlled by pituitary hormones released response to annual environmental changes. In temperate zones, the primary cue driving seasonal reproductive cycles is change day length (i.e., photoperiod), encoded pattern of melatonin secretion from pineal gland. However, although reproduction relies on hypothalamic gonadotrophin-releasing hormone output, most cells producing pars...

In sheep, as in other mammalian species, the pronounced reduction GnRH and gonadotropin secretion that characterizes stages of infertility is normally associated with a conspicuous increase PRL. A possible role PRL modulating release implies presence activation specific receptors target tissues (i.e. pituitary, hypothalamus). this study, we investigated expression receptor (PRL-R) messenger RNA (mRNA) sheep pituitary distribution translated product cell types. Using primers designed to flank...

The intrapituitary mechanisms underlying the inhibitory actions of hyperprolactinaemia on reproductive axis remain unclear. Previous work primary pituitary cultures revealed combined suppressive effects prolactin (PRL) and dopamine gonadotrophin response to GnRH. However, whether these occur directly at level gonadotroph are accompanied by changes in gene expression is still unresolved. Here, αT 3 -1 LβT2 cells were used investigate PRL synthesis release monocultures under basal...

Angiogenesis and vascular regression are critical for the female ovulatory cycle. They enable progression of follicular development, corpora lutea formation regression. in ovary occurs under control endothelial growth factor-A (VEGFA) family proteins, which generated as both pro-(VEGF(165)) anti(VEGF(165)b)-angiogenic isoforms by alternative splicing. To determine role VEGF(165)b cycle, we measured expression marmoset ovaries immunohistochemistry ELISA, used transgenic mice over-expressing...

Abstract Previous studies in sheep have shown that whereas the inhibitory effects of dopamine (DA) systems on GnRH/gonadotrophin secretion are readily detectable during sexually inactive phase under long days (LD), suppressive endogenous opioid peptide (EOP) most evident active short (SD). The hypothesis proposed this study is DA pathways interact with EOP neurons to regulate GnRH/gonadotropin and photoperiod modulates interaction relay its effect seasonal reproductive cycle. To test...

Previous studies have provided evidence for a paracrine interaction between pituitary gonadotrophs and lactotrophs. Here, we show that GnRH is able to stimulate prolactin (PRL) release in ovine primary cultures. This effect was observed during the breeding season (BS), but not nonbreeding (NBS), abolished by application of bromocriptine, specific dopamine agonist. Interestingly, gained ability PRL NBS cultures following treatment with bromocriptine. In contrast, thyrotropin-releasing...

Abrupt alterations in the 24-h light : dark cycle, such as those resulting from transmeridian air travel, disrupt circadian biological rhythms humans with detrimental consequences on cognitive and physical performance. In present study, a jetlag-simulated phase shift photoperiod temporally impaired peaks of peripheral clock gene expression racehorses but acutely enhanced athletic performance without causing stress. Indices aerobic anaerobic capacities were significantly increased by...

Aims The aim of this study was to determine and compare the congruency articular surface contact area patellofemoral joint (PFJ) during both active passive movement knee with use an MRI mapping technique in stable unstable PFJ. Patients Methods A prospective case-control imaging patients a history PFJ instability control group volunteers without symptoms performed. PFJs were imaged scan from 0° through 40° flexion. measurement mapped 5-mm intervals on axial slices. In all, 40 studied. case...

This study was conducted to investigate whether the photoperiodic regulation of seasonal changes in pulsatile LH secretion ram involves activity inhibitory hypothalamic dopaminergic (DA) pathways. To test this hypothesis, a series experiments carried out Soay rams which effects DA-D2 receptor antagonist (sulpiride) or agonist (bromocriptine) on were determined under both long and short days. In each experiment blood samples collected every 10 min for 8 h starting at time vehicle, sulpiride...

A 2‐year comparative study was carried out to evaluate the effect of ovary size, follicle size and oocyte quality 3‐month‐old Simmental calves efficiency using calf ovaries in an vitro fertilization (IVF) programme. We evaluated effects different concentrations follicle‐stimulating hormone (FSH) oestradiol‐17β (E‐17β) maturation medium on development oocytes into morula blastocysts. The proportion recovered (62.1%; 42.8%; 25.3%) percentage good cumulus complexes (84.2%; 59.8%; 45.9%)...

Summary. Prepubertal crossbred beef heifers were injected (i.v.) with 50 μg bovine LH every 2 h for 48 (first injection at 0 h). At 28 h, number and diameter of ovarian follicles determined by ultrasonic scanning, unilateral removal either the ovary bearing largest follicle (Group UL, N = 5) or opposite UO, 4) was performed; control animals remained intact I, 5). Blood samples taken (starting h) a 60-h period to assess concentrations gonadotrophins oestradiol. Preovulatory-like surges...

Hyperprolactinemia is a major cause of infertility, brought about by inhibition gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus and impairment luteinizing (LH) output pituitary gland. However, whereas actions prolactin (PRL) within brain have been investigated extensively, its specific effects at level gonadotroph target cells remain unclear. Here, we provide evidence that PRL are more complex than originally envisaged. Using cell monoculture, first series experiments...

Previous studies have shown that the chronic administration of melatonin in mediobasal hypothalamus (MBH) using micro-implants Soay rams housed under long days causes a sustained decrease secretion prolactin as occurs response to short days. The purpose this study was investigate whether hypothalamic dopaminergic (DA) systems acting through D2 receptors may be involved melatonin-induced effect. Groups living were treated MBH with containing bromocriptine (BROM, DA receptor agonist), or...

To help elucidate the regulatory mechanism responsible for divergent gonadotrophin secretion during sexual maturation, we examined gonadotroph population and hormonal identity of subtypes in pituitary glands juvenile (age, 1.7 +/- 0.2 yr) adult 12.3 0.8 male rhesus monkeys (Macacca mulatta). Serum LH testosterone concentrations were, respectively, 3 7 times lower juveniles than adults, thus confirming different stages development. Immunohistochemistry revealed that proportion gonadotrophs...

In the sheep pituitary, localization of prolactin (PRL) receptors in gonadotrophs and existence gonadotroph-lactotroph associations have provided morphological evidence for possible direct effects PRL on gonadotropin secretion. Here, we investigated whether can readily modify LH response to GnRH throughout ovine annual reproductive cycle. Cell populations were obtained from pituitaries during breeding season (BS) nonbreeding (NBS), plated monolayer cultures 7 days, assigned receive one...

A combined suppressive effect of prolactin (PRL) and dopamine on the secretion luteinising hormone (LH) at level pituitary gland has been identified in sheep, a short-day breeder. However, little is known about role PRL intra-pituitary regulation gonadotrophic axis long-day breeders. In present study, we investigated effects LH follicle-stimulating (FSH) during equine annual reproductive cycle. Horse pituitaries were obtained breeding season (BS) nonbreeding (NBS). Cells dispersed, plated to...

Previous studies have shown that treatment with micro-implants of melatonin in the mediobasal hypothalamus (MBH) sexually inactive Soay rams exposed to long days induces an increase secretion FSH and reactivation testicular axis, as normally occurs response short days. The current study was conducted investigate possible involvement hypothalamic dopaminergic (DA) systems this melatonin-induced effect. At 10 weeks under days, were treated MBH containing bromocriptine (DA agonist) or sulpiride...

In seasonal mammals living in temperate zones, photoperiod regulates prolactin secretion, such that plasma concentrations peak during the summer months and are lowest winter. sheep, a short-day breeder, circulating has important modulatory effects on reproductive system via inhibitory actions pituitary gonadotrophs hypothalamic gonadotrophin-releasing hormone release. The exact cellular mechanisms account for chronic hypersecretion of is not known, although evidence supports an...

The timing of the onset puberty, duration seasonal ovulatory activity, and length postpartum anestrus were studied by means blood plasma progesterone concentrations in a flock European female mouflons (Ovis gmelini musimon) maintained captivity under natural photoperiod (40 degrees 25'N). Concentrations peripheral determined radioimmunoassay samples collected from jugular vein twice week. First ovulations breeding season highly synchronized occurred mid-October. In contrast, cessation cycles...

Prolactin (PRL) has been implicated in central actions including those that result its own regulation and/or the suppression of gonadotropin secretion. It is not clear, however, which neuronal systems may mediate effects PRL. Here, using dual immunohistochemistry for c-Fos and either tyrosine hydroxylase (TH) or proopiomelanocortin (POMC), we have assessed activation, following centrally administered PRL, within two networks shown to participate inhibitory reproductive function. Male rats...

Prolactin signalling within hypothalamic areas associated with the control of fertility was examined in male and lactating female rats. Following exogenous prolactin treatment, phosphorylation STAT5 (signal transducer activator transcription) arcuate nucleus measured using a highly sensitive immunoblotting strategy. A significant increase phosphorylated detected rats compared same-sex controls. No such effect apparent males. Phosphorylation not observed liver either males or females. These...