1,720,971 research outputs found
Nerve growth factor transcriptional control of c-fos promoter transfected in cultured spinal sensory neurons.
No full textHigh efficiency gene transfer (greater than 90%) in chicken dorsal root ganglion neurons has been obtained by DNA calcium phosphate co-precipitation, hence providing an important tool to study control of gene expression in primary neurons. Transfection with c-fos promoter sequences linked to the chloramphenicol acetyltransferase reporter gene showed that the serum responsive element functions as a strong transcriptional enhancer. Transcription from this element is developmentally regulated, and mediates the genetic response to nerve growth factor (NGF) in developing avian sensory neurons. Furthermore, NGF exerts a negative effect on transcription from the cyclic AMP responsive element, thereby supporting the involvement of tyrosine kinase activation by NGF in primary sensory neurons
Brain-derived neurotrophic factor selectively rescues mesencephalic dopaminergic neurons from 2,4,5-trihydroxydopamine induced injury
No full textBrain-derived neurotrophic factor (BDNF) supports the survival of sensory neurons as well as retinal ganglion cells, basal forebrain cholinergic neurons, and mesencephalic dopaminergic neurons in vitro. Here we examined the ability of BDNF to confer protection on cultured dopaminergic neurons against the neurotoxic effects of 6-hydroxyDOPA (TOPA or 2,4,5-trihydroxyphenylalanine), a metabolite of the dopamine pathway suggested to participate in the pathology of Parkinson's disease. Cells prepared from embryonic day 14-15 rat mesencephalon were maintained with 10-50 ng/ml BDNF for 7 days prior to addition of TOPA (10-30 microM) for 24 hr. In BDNF-treated cultures, the extensive loss (> 90%) of tyrosine hydroxylase immunopositive cells was virtually ( 90%) of the overall cell population was limited to only a 25-30% recovery. Furthermore, the monosialoganglioside GM1 (1-10 microM), although inactive alone, acted synergistically with subthreshold amounts of BDNF to rescue tyrosine hydroxylase-positive cells against TOPA neurotoxicity. These results add impetus to exploring the therapeutic potential of gangliosides and BDNF in Parkinson's disease
Lack of coupling of D2 receptors to adenylate cyclase in GH3 cells exposed to epidermal growth factor. Possible role of a differential expression of Gi protein subtypes
No full textMechanisms of chromium toxicity in mammalian cell cultures.
No full textOur observations about the cytotoxic and cytogenetic effects of hexavalent and trivalent chromium compounds in mammalian cells cultured in vitro are reviewed. Additional data concerning the induction of chromosomal aberrations and sister chromatid exchanges, the inhibition of nucleic acid and protein synthesis, the interference with nucleotide metabolism, and the modification of membrane-linked enzyme activity are reported. A possible mechanism of chromium action is proposed
Recombinant human ciliary neurotrophic factor alters the threshold of hippocampal pyramidal neuron sensitivity to excitotoxin damage: synergistic effects of monosialogangliosides.
No full textCiliary neurotrophic factor (CNTF) is a multifunctional protein which not only promotes neuronal survival in vitro and in vivo but also controls cell division of neuronal precursors, transmitter differentiation, and glial cell differentiation. Recent studies have indicated that neurotrophic factors can alter hippocampal neuronal threshold to excitotoxin sensitivity. To examine such a role for CNTF, cultures of rat embryonic hippocampal neurons were maintained with recombinant human CNTF for different times, prior to exposure to a toxic dose of glutamate at 5 days in vitro for a further 24 hr. The cytotoxic action of 200 microM glutamate (approximately 40% of pyramidal neurons remaining after 24 hr) was reduced in a concentration-dependent manner in cultures receiving a prior exposure to CNTF within the first 3 days of cell plating: 30 ng/ml CNTF permitted about 75% of the initial number of pyramidal neurons to survive. Presentation of CNTF less than 48 hr before glutamate challenge was ineffective at up to 100 ng/ml. When pyramidal neurons were cultured with a subthreshold concentration (2 ng/ml) of CNTF together with 10 microM of the monosialoganglioside GM1 (or its inner ester form) in the same paradigm, the resulting neuronal survival was similar to that seen with 30 ng/ml CNTF in the face of a glutamate challenge. Such low doses of either CNTF or ganglioside alone were ineffective. The ability of trophic factors to influence the threshold of neuronal sensitivity to excitatory amino acid injury suggests that these proteins could play an important role in the reparative capacity of acutely traumatized central neurons and in neurodegenerative diseases linked to an excitotoxic mechanism
Effects of potassium dichromate on ATP content of mammalian cells cultured in vitro.
No full textIn order to elucidate the mechanism of the cytotoxic activity of hexavalent chromium (Cr(VI)), the alterations of intracellular ATP levels induced by potassium dichromate in cultured hamster fibroblasts (BHK line) have been studied. Two kinds of treatment procedures were adopted: (1) BHK cell suspensions were exposed to 0.05--1.00 mM K2Cr2O7 in Hanks' balanced salt solution (BSS) for up to 180 min and ATP concentrations were determined immediately after the exposure to Cr(VI). A decrease of ATP content was observed with 0.25--12.00 mM K2Cr2O7 but only in the case of the highest dose was it related in a linear fashion to the duration of the treatment. (2) Cells were preincubated in BSS for 30 min with 0.05--1.00 mM dichromate. They were then reincubated in Eagle's minimal essential medium (MEM) for up to 180 min and ATP was measured at different time points. Immediately after the exposure to chromium all the treated cultures showed a depletion of ATP content. However while the cells treated with 0.25--0.25 mM dichromate rapidly resumed ATP levels very similar to that of the control, no recovery was detected in cells treated with 0.50 and 1.0 mM K2Cr2O7, even after 180 min. The observed effects have been attributed to the oxidizing activity of Cr(VI), which subtracts electrons from electron donors involved in metabolic pathways producing ATP, and to the ability of Cr(III), deriving from Cr(VI) reduction, to form stable coordination complexes with ATP precursors and enzymes involved in ATP synthesis
Excitatory amino acids (EAA): trophic influences and neuronal damage in the mammalian central nervous system (CNS)
No full textThe cytoxic effects of glutamate on cultured cerebellar granule neurons are reporte
Lack of coupling of D-2 receptors to adenylate cyclase in GH-3 cells exposed to epidermal growth factor. Possible role of a differential expression of Gi protein subtypes.
No full textExposure of GH-3 cells to epidermal growth factor for 4 consecutive days induced the expression of both D-2(415) and D-2(444) dopamine-receptor isoforms. Epidermal growth factor also promoted a remarkable increase in the content of Gi3 protein, which is responsible for receptor-induced activation of potassium channels in GH-3 cells. D-2 receptors in this model apparently activate a specific transducing pathway, leading to opening of potassium channels and inhibition of prolactin release by cAMP-independent mechanisms. This is shown by: 1) the selective D-2 agonist quinpirole, while inactive on vasoactive intestinal peptide-induced prolactin release, strongly inhibited the hormone secretion induced by neurotensin; 2) quinpirole, up to 100 microM, did not inhibit cAMP production evoked by vasoactive intestinal peptide both in intact cells and in broken cell membrane preparations; and 3) quinpirole and other D-2 agonists strongly potentiated Rb+ efflux when measured in a nominally calcium-free reaction solution containing 100 mM potassium (voltage-dependent component), but did not modify Rb+ efflux if measured in a reaction solution containing 1 mM calcium and 5 mM potassium (calcium-activated, cAMP-dependent component)
Nerve growth factor (NGF) receptors in a central nervous system glial cell line: upregulation by NGF and brain-derived neurotrophic factor
No full textThe neurotrophic proteins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are related in their primary amino acid structures. In this study we investigated the extent to which the low-affinity NGF receptor (LNGFR) in C6 glioma cells can discriminate between the neurotrophins NGF and BDNF. LNGFR-immunoreactivity (IR) was studied in C6 cells treated for 16 hr with NGF (50 ng/ml) or BDNF (10 ng/ml), using immunogold labelling and electron microscopic morphometric analysis. The cells were exposed to the anti-NGFR antibody 192-IgG, followed by immunoglobulin conjugated with colloidal gold. Untreated C6 cells exhibited some surface gold label (positive LNGFR-IR). Cells treated with NGF or BDNF displayed significantly increased LNGFR-IR on all surfaces in terms of gold labeling, which was more pronounced in NGF-treated cells. LNGFR-IR was also localized in coated endocytotic vesicles, in smooth endoplasmic reticulum, and in secondary multivesicular lysosomes in neurotrophin-treated and untreated cells. The increase in LNGFR protein was further substantiated by a correspondingly higher content of LNGFR mRNA detected after 15 hr of either NGF or BDNF treatment. These results suggest that the LNGFR in glial cells can be upregulated by the structurally related neurotrophins NGF and BDNF
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