Differential effects of oxytocin on olfactory, hippocampal and hypothalamic neurogenesis in adult sheep.

New neurons are continuously added in the dentate gyrus of the hippocampus, the olfactory bulb and the hypothalamus of mammalian brain. In sheep, while the control of adult neurogenesis by the social environment or the photoperiod has been the subject of several studies, its regulation by intrinsic factors, like hormones or neurotransmitters is less documented. We addressed this question by investigating the effects of central oxytocin administration on hippocampal, olfactory and hypothalamic neurogenesis. Endogenous markers, Ki67, Sox2 and DCX were used to assess cell proliferation, progenitor cells density and cell survival respectively in non-gestant ewes receiving a steroid treatment followed by intracerebroventricular injections of either oxytocin or saline. The results showed that oxytocin treatment significantly decreases the density of neuroblasts in the olfactory bulb, increases the density of neuroblasts in the ventromedian nucleus of the hypothalamus while no change is observed in both ventral and dorsal dentate gyrus. In addition, no change in the density of progenitor cells is found in the three neurogenic niches. These findings show for the first time that in females, oxytocin can regulate adult neurogenesis by acting on neuroblasts but not on progenitor cells and that this regulation is region specific.

Highly precocious activation of reproductive function in autumn-born goats (Capra hircus) by exposure to sexually active bucks.

Goats are seasonal breeders with the main cue controlling the timing of breeding season being photoperiod. Hence, the season of birth impacts puberty onset: spring-born goats reach puberty in autumn, at 7 mo of age, whereas autumn-born goats reach puberty at 1 yr during the next reproductive season. The aim of this study was to determine whether exposure of autumn-born young females to sexually active males could counteract the delay in puberty onset observed in autumn-born goats. Females exposed to sexually active males (n = 8) reached puberty earlier than isolated females (n = 8), with exposed females ovulating at a mean age of 3.5 mo. To our knowledge, such precocious puberty onset obtained through social stimulation has never been described in the literature. Moreover, those exposed females exhibited estrus behavior for most ovulations. Our results indicate that in goats born out of season, exposure to sexually active bucks is a really efficient approach to induce early puberty, suggesting that social interactions could have a crucial impact on the regulation of pubertal transition.

Disruption of adult olfactory neurogenesis induces deficits in maternal behavior in sheep.

Profound behavioral changes occur in the mother at parturition, a time when the maternal brain undergoes extensive remodeling of neural circuits, especially in olfactory structures. Adult neurogenesis, a form of brain plasticity, could constitute an adaptive response to motherhood. The present study hypothesized that chemical disruption of olfactory neurogenesis would impair the establishment of maternal behavior in sheep. In addition, because ewes are able to learn the olfactory signature of their offspring, we also examined whether disruption of olfactory neurogenesis altered recognition of the familiar lamb. At one month of gestation, ewes received either infusion of the antimitotic drug Ara-C or saline into the lateral ventricles via one-month-long osmotic minipumps. Ara-C infusion dramatically decreased olfactory neurogenesis but spared hippocampal neurogenesis. Mothers exhibiting more than a 70% reduction in olfactory neurogenesis emitted fewer maternal bleats during the first hours after parturition. Reduction of olfactory neurogenesis also negatively affected discrimination of the familiar lamb. Differences in ewes' aggressive behavior toward familiar and alien lambs were observed in sham mothers, but not in mothers with reduced olfactory neurogenesis. In addition, when ewes were given the choice between familiar and unfamiliar anesthetized lambs, so that only olfactory cues were available, mothers with a reduction in neurogenesis greater than 70% were not able to discriminate their own lamb from an alien lamb. These results indicate that adult-born olfactory neurons are to some extent involved in the establishment of maternal behavior in sheep by contributing to the processing of offspring odors.

Exposure to young preferentially activates adult-born neurons in the main olfactory bulb of sheep mothers.

New neurons are continuously added to the main olfactory bulb (MOB) of the mammalian brain. While their function has been demonstrated in olfactory learning, it is less known in an ethological context such as mothering. We addressed this question by investigating whether in sheep mothers the adult-generated olfactory neurons contribute to the processing of odors involved in attraction to lambs and in memorization of its individual signature. Parturient ewes, after having 2 days of contact with their lamb and being separated from them for 3 h, were exposed for 2 h either to their own lamb, an unfamiliar lamb or a familiar adult sheep and then sacrificed. A control group was composed of mothers not exposed to any lambs for 5 h before sacrifice. Bromodeoxyuridine, a marker of cell division, was injected 3 months before parturition and revealed through immunocytochemistry in combination with markers of activation or neuronal maturation. The percentage of adult-born cells activated in the granular layer of the MOB was compared between the four groups. Results show that the whole population of olfactory neuroblasts and in particular the 3-month-old neuroblasts, are preferentially activated by lamb exposure and that the preferential activation is specific to olfactory neurogenesis since no activation was observed in newborn neurons of the dentate gyrus. However, neither neuroblasts nor mature neurons of the MOB differentiate between familiar and unfamiliar lamb exposure. Therefore, our data shows that adult-born neurons contribute to the processing of infantile odors which are determinant for maternal behavior.

Efficiency of the male effect with photostimulated bucks does not depend on their familiarity with goats.

In ewes, the ovulatory response of females exposed to familiar rams is lower than the response of those exposed to novel ones. In goats, males rendered sexually active by exposure to long days are more efficient to induce ovulation in seasonal anestrous females than untreated males. Two experiments were conducted to determine 1) whether male goats remain familiar to females after 45days of separation; and 2) whether photostimulated males are able to stimulate the sexual activity of females, independently of their familiarity with them. In Experiment 1, three groups of goats (n=10 goats per group) were put in contact with males (n=2 per group) during 10days in November (familiarization period). These males were called familiar males. After 15, 30 and 45days of separation from the males, females of each group were exposed to familiar or novel males during 10min. In each test, goats in contact with novel males displayed more distress bleats, escapes, head butts, and sniffing than those in contact with familiar males (P<0.05). In Experiment 2, we used sexually inactive (n=4 control males), and sexually active males (n=4 photostimulated males). In February, two groups of goats (n=50 each) were put in contact with control or photostimulated males (n=2 each) during 10days ("familiar" control or photostimulated male, respectively). After 45days of separation from the males, both groups of females were further divided into two groups (n=25 goats per group). In April, two groups were re-exposed to "familiar" control or "familiar" photostimulated males (n=2 per group), whereas the other two groups were exposed to "novel" control or "novel" photostimulated males (n=2 per group). The photostimulated males displayed a higher level of sexual behavior than the controls. The proportion of goats that ovulated and displayed estrus was higher when exposed to the photostimulated males than when exposed to control ones (≥80% vs. 0%; P<0.05). These proportions did not differ between groups exposed to familiar or novel photostimulated males (P>0.05). We concluded that after 45days of separation, males are still familiar to females. The photostimulated males are able to induce the sexual activity of seasonally anestrous goats independently of their familiarity with them.

Vaginocervical stimulation of Ewes induces the rapid formation of a new bond with an alien young without interfering with a previous bond.

Ewes form a selective olfactory memory for their lambs after 2 hr of mother-young interaction following parturition. Mothers will subsequently reject any strange lamb at suckling. The present study investigated whether artificial vaginocervical stimulation (VCS) allows the formation of a selective bond with an unfamiliar lamb and whether it interferes with the maintenance of the bond formed with the familiar lamb. At 2 hr postpartum, mothers were separated from their familiar lamb after having formed a selective bond with it and were given 10 min of mechanical VCS. In the "VCS + lamb" group (n = 24) an unfamiliar lamb was left with the ewe for 2 hr whereas in the "VCS no lamb" group (n = 26) the mother was left alone for the same period of time. Ewes of the "no VCS" group (n = 14) did not receive any VCS. In the majority of animals of the "VCS + lamb" group (23/24) VCS induced a complete acceptance of the unfamiliar lamb without any disruption of the bond previously formed with the familiar lamb. VCS or 2 hr of separation did not disrupt the maintenance of the selective bond initially formed with the familiar lamb since all the ewes of the "VCS no lamb" and "no VCS" groups accepted it at suckling.

Detection and isolation of equine herpesviruses 1 and 4 from horses in Normandy: an autopsy study of tissue distribution in relation to vaccination status.

Equine herpesviruses type 1 and 4 (EHV-1 and EHV-4) are ubiquitous in the equine population. One of their main properties is their ability to establish life-long latent infections in their hosts even in those with natural or vaccine-induced immunity. However, effect of vaccination status on prevalence and tissue tropism was not established. In this study, EHV-1 and EHV-4 were detected by polymerase chain reaction and by classical virus isolation from neural, epithelial and lymphoid tissues collected from unvaccinated (33) or vaccinated (23) horses. The percentage of EHV-1- and EHV-4-positive horses between vaccinates and unvaccinates was similar. Both viruses were detected in all tissues of both groups; in particular, lymph nodes draining the respiratory tract, nasal epithelium and nervous ganglia [i.e. trigeminal ganglia (TG)], which represent the main positive sites for EHV-1 and EHV-4. In vaccinated animals, the nervous ganglia (i.e. TG) were less frequently positive than in unvaccinated animals. Detection of positive TG was strongly correlated to the presence of EHV-1 in nasal epithelium.

Hypertension: a survey of 7000 Air France employees.

During a period of one year, 6,863 employees underwent routine medical check-ups: 3,223 ground staff, 3,129 cabin staff, and 511 cockpit crew. One hundred and fifty permanent hypertensives were recorded and their status and evolution analysed in a survey. For every patient data were collected on illness, treatment, heredity, aetiology, risk factors, type of work and life style. The 150 patients surveyed were divided into four groups: (A) 70 satisfactorily treated hypertensives (57 men, 13 women); (B) 31 unsatisfactorily treated hypertensives (24 men, 7 women); (C) 33 neglected hypertensives (31 men, 2 women); and (D) 16 newly discovered hypertensives (14 men, 2 women). The incidence of hypertension was higher in ground staff (3.9%) than in cockpit crew (1.76%) and very low in cabin staff (0.41%). The neglected and unsatisfactorily treated hypertensives showed a clear improvement in their blood pressure through ongoing surveillance. In conclusion, while the incidence of hypertension in the population surveyed is quite low, this study shows a significantly lower rate in cabin staff and a large proportion of neglected and unsatisfactorily treated hypertension. It also shows how an occupational medical practitioner with no power of prescription can be effective in detecting the disease and referring the employee to his general practitioner, with a view towards achieving better collaboration.