Glucocorticoid modulation of atrial natriuretic peptide, oxytocin, vasopressin and Fos expression in response to osmotic, angiotensinergic and cholinergic stimulation.

The regulation of fluid and electrolyte homeostasis involves the participation of several neuropeptides and hormones that utilize hypothalamic cholinergic, alpha-adrenergic and angiotensinergic neurotransmitters and pathways. Additionally, it has been suggested that hypothalamus-pituitary-adrenal axis activity modulates hormonal responses to blood volume expansion. In the present study, we evaluated the effect of dexamethasone on atrial natriuretic peptide (ANP), oxytocin (OT) and vasopressin (AVP) responses to i.c.v. microinjections of 0.15 M and 0.30 M NaCl, angiotensin-II (ANG-II) and carbachol. We also evaluated the Fos protein immunoreactivity in the median preoptic (MnPO), paraventricular (PVN) and supraoptic (SON) nuclei. Male Wistar rats received an i.p. injection of dexamethasone (1 mg/kg) or vehicle (0.15 M NaCl) 2 h before the i.c.v. microinjections. Blood samples for plasma ANP, OT, AVP and corticosterone determinations were collected at 5 and 20 min after stimulus. Another set of rats was perfused 120 min after stimulation. A significant increase in plasma ANP, OT, AVP and corticosterone levels was observed at 5 and 20 min after each central stimulation compared with isotonic saline-injected group. Pre-treatment with dexamethasone decreased plasma corticosterone and OT levels, with no changes in the AVP secretion. On the other hand, dexamethasone induced a significant increase in plasma ANP levels. A significant increase in the number of Fos immunoreactive neurons was observed in the MnPO, PVN and SON after i.c.v. stimulations. Pre-treatment with dexamethasone induced a significant decrease in Fos immunoreactivity in these nuclei compared with the vehicle. These results indicate that central osmotic, cholinergic, and angiotensinergic stimuli activate MnPO, PVN and SON, with a subsequent OT, AVP, and ANP release. The present data also suggest that these responses are modulated by glucocorticoids.

A contribution to the histological study of hypercementosis using metal staining.

After studying hypercementosis, in detail using metallic staining procedures, the authors reached the following conclusions: (1) The histology of hypercementosis, observed by metallic staining reveals remarkable and characteristic microscopical alterations. (2) The Rio Hortega12 procedures, the mitochondria technique of Polak,10 and the method of Achucarro-Hortega13 are of great value for the study of the morphology of cementum. (3) Among the technical procedures used, we consider the 1916 method of Achucarro-Hortega as affording the best view of cementocytes. (4) The Sharpey fibers, revealing great irregularity in course, shape and size, and frequent interruptions could be clearly observed; heavily stained lacunae were frequently observed along the cementum-dentin border; a direct deposit of cellular cementum on the dentin in the middle third of the root was frequently observed. Curiously, an acellular cementum deposit next to a cellular cementum layer could be observed; we also noted numerous cementocytes of different shapes and sizes, at times exhibiting alterations of a degenerative type, particularly fragmentation of protoplasmic prolongations. (5) The techniques used also showed the frequency of blood vessels in the texture of hyperplastic cementum and the presence of capillaries near cementum-dentin junction.