This study using our piglet HI model shows that it is possible by means of a head-cooling cap to cool the brain more than the body for a 24-hour period while keeping the core temperature mildly hypothermic. However, we were unable to predict temperatures inside the brain using surface temperature probes on the head.

Background: Hypothermia has been shown to be neuroprotective in animal models of hypoxia-ischaemia. It is currently being evaluated as a potentially therapeutic option in the management of neonatal hypoxicischaemic encephalopathy. However, significant hypothermia has adverse systemic effects. It has also recently been found that the stress of being cold can abolish the neuroprotective effects of hypothermia. It is hypothesised that selective head cooling (SHC) while maintaining normal core temperature would enable local hypothermic neuroprotection while limiting the stress and side effects of hypothermia. Objective: To determine whether it is possible to induce moderate cerebral hypothermia in the deep brain of the piglet while maintaining the body at normothermia (39˚C). Methods: Six piglets (,48 hours old) were anaesthetised, and temperature probes inserted into the brain. Temperature was measured at different depths from the brain surface (21 mm (T deep brain ) to 7 mm (T superficial brain )). After a 45 minute global hypoxic-ischaemic insult, each piglet was head cooled for seven hours using a cap circulated with cold water (median 8.9˚C (interquartile range 7.5-14)) wrapped around the head. Radiant overhead heating was used to warm the body during cooling.

Little is known about the neuroendocrine control of fertility in the horse. In this species, unusual features characterize the normal estrous cycle such as a prolonged preovulatory LH surge during the follicular phase and a distinctive FSH surge during the midluteal phase. This study investigated the distribution and hormonal identity of gonadotrophs in the pars distalis (PD) and pars tuberalis (PT) of the equine pituitary gland as possible morphological bases for the referred unusual endocrine characteristics. In addition, the proportion of gonadotrophs in relation to other pituitary cell types during both the estrous cycle and anestrus were investigated. Pituitary glands were collected from sexually active (n = 5) and seasonally anestrous (n = 5) mares in November, and single or double immunofluorescent staining was carried out on 6-microm sections using monoclonal antibodies to the LHbeta or FSHbeta subunits and a polyclonal antibody to ovine LHbeta. Gonadotrophs were densely distributed around the pars intermedia in the PD and in the caudal ventral region of the PT. In addition to isolated cells, clusters of gonadotrophs were found surrounding the capillaries. No significant differences were detected in the number of gonadotrophs between sexually active and anestrous mares in either the PD or PT. In the PD, gonadotrophs represented 22.7 +/- 5. 8% and 19.1 +/- 2.1% of the total cell density in sexually active and anestrous animals, respectively (P: > 0.05). However, in the PT, gonadotrophs accounted for a higher proportion of the total cell population in sexually active (6 +/- 0.1%) than in anestrous (1.2 +/- 0.05%) mares (P: < 0.02). Double immunofluorescence revealed that the majority of gonadotrophs were bihormonal (i.e., positive for LH and FSH); however, in the sexually active mare, a larger proportion of gonadotrophs (22.5 +/- 3.6%) were monohormonal for either LH or FSH, when compared to anestrous animals (9.7 +/- 1.2%; P: < 0.02). Based on these findings we conclude that: 1) although the relative distribution of gonadotrophs is similar to those reported for other species, a significantly larger proportion of gonadotroph cells is present in the equine pituitary gland; 2) gonadotroph density does not appear to differ between sexually active and anestrous mares in the PD; 3) a larger proportion of gonadotrophs is apparent in the PT of sexually active animals; and 4) although a large incidence of bihormonal gonadotrophs is present in the horse, specific LH or FSH cells differentiate predominantly during the sexually active phase.

The intrahypophysial mechanisms involved in the control of gonadotrophin secretion remain unclear. In the horse, a divergent pattern of gonadotrophins is observed at different stages of the reproductive cycle in response to a single secretagogue (gonadotrophin-releasing hormone), and dramatic changes in fertility take place throughout the year in response to photoperiod. This species thus provides a useful model to investigate the regulation of fertility directly at the level of the hypophysis. A series of studies were undertaken to examine the cytological arrangements and heterogeneity of gonadotrophin storage in the pars distalis (PD) and pars tuberalis (PT) of the hypophysis of male and female horses. Specifically, the seasonal and gonadal effects on distribution, density and hormonal identity of gonadotrophs, the existence of gonadotroph-lactotroph associations and the expression of prolactin receptors (PRL-R) as possible morphological bases for the differential control of gonadotrophin secretion were investigated. It became apparent that both isolated and clustered gonadotrophs are normally distributed around the pars intermedia and surrounding capillaries in the PD, and in the caudal ventral region of the PT. In the PD, no effects of season or of reproductive state on the density or number of gonadotrophs could be detected in either male or female animals. In contrast, a fivefold increase in gonadotroph density was observed in the PT during the sexually active stage. In males, robust gonadal effects were detected on the gonadotroph population; orchidectomy significantly reduced both the number and proportion of gonadotrophs, in relation to other hypophysial cell types, in both the PD and PT regions. Luteinizing hormone (LH) monohormonal, follicle-stimulating hormone (FSH) monohormonal and bihormonal gonadotrophs were identified in the PD and PT of male and female horses. Interestingly, in males, the relative proportions of gonadotroph subtypes and the LH/FSH monohormonal gonadotroph ratio were not affected by either season or the presence of the gonads. In contrast, a larger proportion of monohormonal gonadotrophs was clearly observed in sexually active females. Specific gonadotroph-lactotroph associations and expression of PRL-R in cells other than gonadotrophs were detected in the PD throughout the annual reproductive cycle. In addition to a stimulatory gonadal effect on lactotroph density, a substantial gonadal-independent effect of season was apparent on this variable. The findings have revealed important seasonal and gonadal effects on the cytological configuration of the equine hypophysis, which may provide the morphological basis for the intrahypophysial control of fertility.