The Effects of Vitamin D Receptor Silencing on the Expression of LVSCC-A1C and LVSCC-A1D and the Release of NGF in Cortical Neurons

Recent studies have suggested that vitamin D can act on cells in the nervous system. Associations between polymorphisms in the vitamin D receptor (VDR), age-dependent cognitive decline, and insufficient serum 25 hydroxyvitamin D(3) levels in Alzheimer's patients and elderly people with cognitive decline have been reported. We have previously shown that amyloid β (Aβ) treatment eliminates VDR protein in cortical neurons. These results suggest a potential role for vitamin D and vitamin D-mediated mechanisms in Alzheimer's disease (AD) and neurodegeneration. Vitamin D has been shown to down-regulate the L-type voltage-sensitive calcium channels, LVSCC-A1C and LVSCC-A1D, and up-regulate nerve growth factor (NGF). However, expression of these proteins when VDR is repressed is unknown. The aim of this study is to investigate LVSCC-A1C, LVSCC-A1D expression levels and NGF release in VDR-silenced primary cortical neurons prepared from Sprague-Dawley rat embryos.qRT-PCR and western blots were performed to determine VDR, LVSCC-A1C and -A1D expression levels. NGF and cytotoxicity levels were determined by ELISA. Apoptosis was determined by TUNEL. Our findings illustrate that LVSCC-A1C mRNA and protein levels increased rapidly in cortical neurons when VDR is down-regulated, whereas, LVSCC-A1D mRNA and protein levels did not change and NGF release decreased in response to VDR down-regulation. Although vitamin D regulates LVSCC-A1C through VDR, it may not regulate LVSCC-A1D through VDR.Our results indicate that suppression of VDR disrupts LVSCC-A1C and NGF production. In addition, when VDR is suppressed, neurons could be vulnerable to aging and neurodegeneration, and when combined with Aβ toxicity, it is possible to explain some of the events that occur during neurodegeneration

Effects of estrogen and tamoxifen on the ultrastructural characteristics of female rat prolactin cells as evaluated by immunogold technique

Estrogens and antiestrogens are known to have effects on protactin (PRL)-producing cells in the anterior pituitary. This study was planned to investigate the effects of estrogen and tamoxifen at immunohistochemical. and immunoelectron microscopic levels on PRL cells of female rat pituitary. Animals were divided into three groups of eight adult female rats each. The first group was the control. group. 200-mu g/day of estrogen was administered subcutaneously for 11 weeks to 16 rats. Tamoxifen was administered to eight of them for the Last 15 days. In diethylstilbestrol (DES)-induced group, serum PRL levels and pituitary weights were found to be elevated when compared with the control group. In the DES plus tamoxifen group the readings were close to that of the control group. PRL-positive cells were enlarged and strongly immunostained in DES-induced group when assessed by tight microscopy. Tamoxifen prevented this effect. At the ultrastructural. level., in the tamoxifen treated group, PRL-producing cells contained both immunopositive and immunonegative secretory granules. Numerous PRL-producing cells exhibited progressive morphological changes in the nuclei compatible with the apoptotic process. The results of this study indicate that tamoxifen prevents not only the proliferative effect of estrogen but also inhibits the secretion mechanism of the cells. (c) 2005 Elsevier GmbH. ALL rights reserved

Immunocytochemical detection of effects of TRH and T-4 on prolactin- and TSH-producing cells in the pituitary gland of Rana ridibunda

Effects of synthetic thyrotropin-releasing hormone (TRH) and various doses of thyroxin (T-4) on prolactin (PRL)-producing cells and thyrotropic cells in the pituitary were investigated in adult mate and female Rana ridibunda frogs. Animals were given 200 mug TRH once a week for 4 weeks and 0.2-0.5 mg T-4 during 3 days per week for a period of 2 weeks by injections in the groin. PRL-producing cells and thyrotropic cells were identified with tight microscopical and electron microscopical immunocytochemical methods, using rabbit anti-PRL and rabbit anti-thyroid stimulating hormone (TSH) as primary antibodies. TRH caused cytological changes in both cell types, which were consistent with increased synthesis and release of both PRL and TSH. Treatment with 0.5 mg T-4 activated both cell types less than TRH treatment did, whereas 0.2 and 0.4 mg T-4 caused inactivation of both cell types. In conclusion, mammalian TRH is effective on both types of frog pituitary cells. Our study suggests that T-4 has a positive rather than a negative effect when concentrations above a certain threshold are given. (C) 2004 Elsevier GmbH. All rights reserved