Effect of constant light on fetal and maternal prolactin rhythms in sheep

A 24-h rhythm of plasma PRL is present in fetal sheep. This rhythm is synchronized to an environmental clue (zeitgeber). We determined whether the light-dark cycle (L:D) is a zeitgeber for the fetal PRL rhythm and, if so, whether the mother might convey this zeitgeber to the fetus. We kept nine ewes (twin pregnancies) in constant light (L:L) and five ewes (singleton) in 14:lO L:D from 110 days gestation. Fetuses and mothers were catheterized at 119 days gestation. Blood samples were taken hourly for 24 h after 16 days under L:L or L:D. A mean 24-h rhythm of PRL was found (by RIA) in fetuses under L:D, but not in those under L:L. However, fetuses under L:L showed individual 24-h PRL rhythms (cosinor analysis) whose acrophases were distributed around the clock. Nonsynchronized rhythms persisted after 23 and 30 days of L:L. Acrophases of PRL rhythms within a set of twins were closer than those between sets, suggesting that twins were responding to a common signal. These findings indicate that the L:D cycle is a zeitgeber for the PRL rhythm in fetal sheep and suggest that the mother might convey the zeitgeber

Cardiovascular responses to alpha-melanocyte stimulating hormone during the perinatal period in sheep

To determine the effects of alpha-melanocyte stimulating hormone (αMSH) on the circulation of undisturbed fetal sheep and young lambs and to explore possible mechanisms of actions, we examined the responses of ascending aortic blood flow, heart rate, stroke volume, and arterial blood pressure to a single intravenous injection of αMSH, ACTH, cortisol and to αMSH after beta-adrenergic blockade. We also measured cardiac output and organ blood flows before and after αMSH injection by the radionuclide labeled microsphere technique. αMSH increased ascending aortic blood flow from 249 ± 23 to 327 ± 30 ml- min-1-kg-1 (P < 0.001), heart rate from 111 ± 10 to 126 ± 11 min-1, (P < 0.001) and stroke volume from 2.32 ± 0.21 to 2.75 ± 0.20 ml-kg-1, (P < 0.001) in 10 young lambs 15-30-day-old. αMSH decreased mean systemic arterial blood pressure from 42.6 ± 1.7 to 39.3 ±1.6 mmHg (P < 0.001) in fetal sheep and min-1, (P < 0.001) and stroke volume from 2.32 ± 0.21 to 2.75 ± 0.20 ml-kg-1, (P < 0.001) i

Estimulação tátil-cinestésica: uma integração entre pele e sistema endócrino? Tactile-kinesthetic stimulation: integration between skin and endocrine system?

Apresenta-se uma revisão da literatura sobre os aspectos neuroendócrinos da pele e as conseqüências da estimulação tátil-cinestésica sobre o córtex adrenal. Os artigos foram identificados a partir das bases de dados MEDLINE e LILACS, usando as palavras-chave "córtex supra-renal", "pele", "massagem", "lactentes", "glicocorticóide" e "ritmo circadiano". O período pesquisado foi de 1990 a 2003. Foram também consultados artigos de destaque publicados antes desse período. Estudos reconhecem o hipotálamo, a hipófise e a glândula adrenal como órgãos dinâmicos durante o desenvolvimento fetal e neonatal, e que respostas de estresse estão presentes ao nascer. A maioria dos estudos revisados, utilizando a estimulação tátil-cinestésica, seja em humanos ou animais, evidencia a capacidade da pele em metabolizar, coordenar e organizar estímulos externos, procurando manter a homeostase interna e externa, demonstrando a interação entre sistema neuroendócrino e a pele. A estimulação tátil-cinestésica parece ter um efeito sobre a reatividade hormonal, porém essa questão merece uma investigação mais aprofundada.<br>A literature review on skin neuroendocrine aspects and the consequences of the tactile- kinesthetic stimulation on the adrenal cortex are presented. The articles were identified through MEDLINE and LILACS data bases, using the keywords "suprarenal cortex", "skin", "massage", "infants", "glucocorticoid" and "circadian rhythm". Single articles published between 1990 and 2003 were considered, as well as outstanding ones prior to this period. Studies recognize that the hypothalamus, the pituitary and the adrenal gland are dynamic organs during fetal and neonatal development, and that stress responses are active at birth. Most of the studies reviewed, using tactile-kinesthetic stimulation, both in humans and animals, confirm skin's ability to metabolize, coordinate and organize external stimuli, attempting to maintain both external and internal homeostasis, demonstrating an interaction between the neuroendocrine system and tactile stimulation. Tactile-kinesthetic stimulation seems to have an effect on hormonal reactivity, although the issue demands further investigation

Chronic stress decreases the expression of sympathetic markers in the pineal gland and increases plasma melatonin concentration in rats.

Chronic stress affects brain areas involved in learning and emotional responses. Although most studies have concentrated on the effect of stress on limbic-related brain structures, in this study we investigated whether chronic stress might induce impairments in diencephalic structures associated with limbic components of the stress response. Specifically, we analyzed the effect of chronic immobilization stress on the expression of sympathetic markers in the rat epithalamic pineal gland by immunohistochemistry and western blot, whereas the plasma melatonin concentration was determined by radioimmunoassay. We found that chronic stress decreased the expression of three sympathetic markers in the pineal gland, tyrosine hydroxylase, the p75 neurotrophin receptor and alpha-tubulin, while the same treatment did not affect the expression of the non-specific sympathetic markers Erk1 and Erk2, and glyceraldehyde-3-phosphate dehydrogenase. Furthermore, these results were correlated with a significant increase in plasma melatonin concentration in stressed rats when compared with control animals. Our findings indicate that stress may impair pineal sympathetic inputs, leading to an abnormal melatonin release that may contribute to environmental maladaptation. In addition, we propose that the pineal gland is a target of glucocorticoid damage during stress

Impact of maternal melatonin suppression on amount and functionality of brown adipose tissue (BAT) in the newborn sheep

© 2014 Seron-ferre, Reynolds, Mendez, Mondaca, Ebensperger, Valenzuela, Valenzuela, Herrera, Llanos and Torres-farfan. In human and sheep newborns, brown adipose tissue (BAT) accrued during fetal development is used for newborn thermogenesis. during gestation on the amount and functionality of BAT in the neonate. We studied BAT from 6 lambs gestated by ewes exposed to constant light from 63% gestation until delivery to suppress melatonin (LL), 6 lambs gestated by ewes exposed to LL but receiving daily oral melatonin (12mg at 1700 hrs, LL+Mel) and another 6 control lambs gestated by ewes maintained in 12h light:12h dark (LD). Lambs were instrumented at 2 days of age. At 4-6 days of age, they were exposed to 24°C (thermal neutrality conditions) for 1 hr, 4°C for 1 hr and 24°C for 1 hr. Afterward, lambs were euthanized and BAT was dissected for mRNA measurement, histology and ex vivo experiments. LL newborns had lower central BAT and skin temperature under thermal neutrality and at 4°C,