RESUMO
Developmental programming refers to processes that occur during early life that may have long-term consequences, modulating adult health and disease. Complex diseases, such as diabetes, cancer and cardiovascular disease, have a high prevalence in different populations, are multifactorial, and may have a strong environmental component. The environment interacts with organisms, affecting their behaviour, morphology and physiology. This interaction may induce permanent or long-term changes, and organisms may be more susceptible to environmental factors during certain developmental stages, such as the prenatal and early postnatal periods. Several factors have been identified as responsible for inducing the reprogramming of various reproductive and nonreproductive tissues. Among them, both natural and synthetic steroids, such as endocrine disruptors, are known to have either detrimental or positive effects on organisms depending on the dose of exposure, stage of development and biological sexual background. The present review focuses on the action of steroids and endocrine disruptors as agents involved in developmental programming and on their modulation and effects on female neuroendocrine functions.
Assuntos
Disruptores Endócrinos/toxicidade , Hormônios Esteroides Gonadais/fisiologia , Sistemas Neurossecretores/crescimento & desenvolvimento , Animais , Feminino , Humanos , Sistemas Neurossecretores/efeitos dos fármacos , Sistemas Neurossecretores/fisiopatologia , Síndrome do Ovário Policístico/fisiopatologia , Gravidez , Efeitos Tardios da Exposição Pré-Natal/fisiopatologiaRESUMO
Exposure to adverse environmental conditions can elicit a stress response, which results in an increase in endogenous corticosterone levels. In early life stages, it has been thoroughly demonstrated that amphibian larval growth and development is altered as a consequence of chronic stress by interfering with the metamorphic process, however, the underlying mechanisms involved have only been partially disentangled. We examined the effect of intraspecific competition on corticosterone levels during larval development of the toad Rhinella arenarum and its ultimate effects on cell proliferation in particular brain areas as well as the pituitary gland. While overcrowding altered the number of proliferating cells in the pituitary gland, hypothalamus, and third ventricle of the brain, no differences were observed in areas which are less associated with neuroendocrine processes, such as the first ventricle of the brain. Apoptosis was increased in hypothalamic regions but not in the pituitary. With regards to pituitary cell populations, thyrotrophs but not somatoatrophs and corticotrophs showed a decrease in the cell number in overcrowded larvae. Our study shows that alterations in growth and development, produced by stress, results from an imbalance in the neuroendocrine systems implicated in orchestrating the timing of metamorphosis.
Assuntos
Encéfalo/crescimento & desenvolvimento , Bufo arenarum/crescimento & desenvolvimento , Proliferação de Células , Aglomeração , Sistemas Neurossecretores/crescimento & desenvolvimento , Hipófise/crescimento & desenvolvimento , Estresse Fisiológico , Animais , Apoptose , Encéfalo/citologia , Corticosterona/análise , Larva/citologia , Larva/crescimento & desenvolvimento , Metamorfose Biológica , Sistemas Neurossecretores/citologia , Hipófise/citologiaRESUMO
Stress events during adolescence may contribute to the expression or exacerbation of physical and behavioral disorders. However, little attention has been given to the physiological and behavioral changes promoted by stress during this period of ontogeny. In the present study we investigated, in adolescent male rats, the effects of repeated exposure to restraint or variable stress on: (a) locomotor activity and corticosterone levels after exposure to a novel environment; (b) corticosterone levels in response to the exposure to restraint stress; and (c) changes in body, thymus and adrenal weights. The results demonstrated that repeated exposure to restraint or variable stress reduced the locomotor response, but did not affect corticosterone secretion, in response to a novel environment. Moreover, both chronic stress procedures did not change corticosterone secretion in response to acute restraint stress. Furthermore, our results showed that repeated restraint, but not variable stress, produced a decrease in body weight along the stress exposure. Finally, we observed that the exposure to variable stress reduced the thymus relative weight. Taken together our results suggest that behavioral and physiological changes induced by exposure to chronic stress during adolescence depend on the stress regimen.
Assuntos
Comportamento Animal/fisiologia , Corticosterona/sangue , Atividade Motora/fisiologia , Sistemas Neurossecretores/fisiopatologia , Estresse Psicológico/fisiopatologia , Timo/fisiopatologia , Animais , Doença Crônica , Corticosterona/metabolismo , Modelos Animais de Doenças , Masculino , Sistemas Neurossecretores/crescimento & desenvolvimento , Sistemas Neurossecretores/metabolismo , Ratos , Ratos Wistar , Estresse Psicológico/complicações , Timo/crescimento & desenvolvimento , Timo/patologiaRESUMO
The ontogeny of the neurohormonal peptides vasoactive intestinal polypeptide (VIP), neurotensin (NT), substance P (SP), calcitonin gene-related peptide (CGRP), gastrin/cholecystokinin (GAS/CCK), and somatostatin (SOM) as well as serotonin (SER) and nitric oxide synthase (NOS) was investigated in the gastrointestinal tract of the urodele Ambystoma mexicanum, the axolotl, using immunohistochemical techniques. The first regulatory substances to appear were SP, SOM, and SER that could be immunohistochemically detected up from stage 1. At early stage 2, VIP immunoreactivity was observed infrequently in enteric nerve fibers. With the onset of external feeding at late stage 2, SP-immunoreactive (IR) and SER-IR endocrine cells and VIP-IR nerve fibers were present throughout the gastrointestinal tract. Furthermore, in the small intestine NT-IR and GAS/CCK-IR endocrine cells appeared. At stage 3, SER immunoreactivity was observed not only in endocrine cells but also in nerve fibers. CGRP-IR and SP-IR nerve fibers were detectable at stage 4 and stage 5, respectively. From stage 5 on, a minority of the CGRP immunoreactivity occurred in SP-IR nerve fibers. NOS immunoreactivity did not appear before stage 6 when it was found infrequently in nerve fibers. Thus, several phases of development can be distinguished: (1) at the yolk sac stages only few regulatory substances are present. (2) At the onset of external feeding, all endocrine cell types investigated were readily detectable. Thus, the onset of external feeding seems to trigger the development of the gastrointestinal endocrine system. (3) The endocrine cells are first found in the proximal part of the gastrointestinal tract and later in higher numbers in the distal parts. (4) The dually distributed neurohormonal peptides and SER first appear in endocrine cells and later additionally in nerve fibers. Thus, the nerve fibers likely set up the fine regulation of gastrointestinal blood flow and motility.
Assuntos
Ambystoma/crescimento & desenvolvimento , Sistema Digestório/crescimento & desenvolvimento , Neuropeptídeos/análise , Sistemas Neurossecretores/crescimento & desenvolvimento , Óxido Nítrico Sintase/análise , Serotonina/análise , Ambystoma/metabolismo , Animais , Peptídeo Relacionado com Gene de Calcitonina/análise , Colecistocinina/análise , Sistema Digestório/química , Gastrinas/análise , Imuno-Histoquímica , Larva/crescimento & desenvolvimento , Larva/metabolismo , Sistemas Neurossecretores/química , Neurotensina/análise , Somatostatina/análise , Substância P/análise , Peptídeo Intestinal Vasoativo/análiseRESUMO
The pineal complex of larval Geotria australis lampreys has been examined by light- and electron-microscopy. The complex consists of a pineal organ and a smaller parapineal organ, the former being situated dorsal to the latter. It is concluded that the pineal organ is a functioning photoreceptor, with neural and endocrine output. The parapineal appears to be a more basic neuroendocrine organ without photosensory capability. Day-night comparisons of the pineal complex show no obvious differences in ultrastructure; this could be related to the chronobiological role of the complex as a constant monitor of ambient light levels, rather than a mere visual receptor that changes its sensitivity at night.
Assuntos
Diencéfalo/ultraestrutura , Lampreias/anatomia & histologia , Sistemas Neurossecretores/ultraestrutura , Glândula Pineal/ultraestrutura , Animais , Ritmo Circadiano , Diencéfalo/crescimento & desenvolvimento , Lampreias/crescimento & desenvolvimento , Larva , Microscopia Eletrônica , Sistemas Neurossecretores/crescimento & desenvolvimento , Glândula Pineal/crescimento & desenvolvimentoRESUMO
In adult female rats born from Streptozotocin-diabetic mothers, blood glucose measured under basal conditions or 30 min after glucose administration was similar to controls; however at 180 min 50% of offspring from diabetics was moderately hyperglycemic whereas 100% of controls were normoglycemic. The time of vaginal opening, and after maturity, the number of rats with regular estrous cycles was in the range of controls. After ovariectomy, control rats receiving estradiol showed a sharp increase of serum LH at 4 pm following progesterone treatment at 10 am, while rats born from diabetic mothers failed to modify serum LH. Estradiol receptors in cell nuclei and cytosolic progestin receptors were determined in anterior pituitary, hypothalamus and preoptic area of rats subjected to a 4-day estradiol treatment. Changes were statistically significant in the hypothalamus only, in that rats born from diabetic mothers showed reduced induction of progestin receptors coupled to increased binding of (3H)-estradiol in cell nuclei. These findings bring support for a hypothalamic defect in rats born from diabetic mothers, the reduction of hypothalamic progestin receptors being reflected in the reduced sensitivity to the positive feedback action of progesterone to release LH.