ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03484.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Using stable cell lines containing a series of deletions of the myelin basic protein (MBP) promoter directing the bacterial chloramphenicol acetyltransferase gene in a peripheral neurinoma cell line, we have studied the sequences in the MBP promoter needed for induction by cyclic AMP. Stimulation of expression from the MBP promoter by cyclic AMP is not a rapid response. Expression begins after 24 h and reaches a maximum at ˜72 h. The results from the stable transformants indicate at least one region that appears to be essential to the induction of transcription directed by the MBP promoter. The region that is necessary for induction does not contain a consensus cyclic AMP response element. A specific binding site involved in the induction by cyclic AMP was localized to an NFI binding site

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03485.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:In a previous work, we calculated the dietary α‐linolenic requirements (from vegetable oil triglycerides) for obtaining and maintaining a physiological level of (n‐3) fatty acids in developing animal membranes as determined by the cervonic acid content [22:6(n‐3), docosahexaenoic acid]. The aim of the present study was to measure the phospholipid requirement, as these compounds directly provide the very long polyunsaturated fatty acids found in membranes. Two weeks before mating, eight groups of female rats (previously fed peanut oil deficient in α‐linolenic acid) were fed different semisynthetic diets containing 6% African peanut oil supplemented with different quantities of phospholipids obtained from bovine brain lipid extract, so as to add (n‐3) polyunsaturated fatty acids to the diet. An additional group was fed peanut oil with rapeseed oil, and served as control. Pups were fed the same diet as their respective mothers, and were killed at weaning. Forebrain, sciatic nerve, retina, nerve endings, myelin, and liver were analyzed. We conclude that during the combined maternal and perinatal period, the (n‐3) fatty acid requirement for adequate deposition of (n‐3) polyunsaturated fatty acids in the nervous tissue (and in liver) of pups is lower if animals are fed (n‐3) very long chain polyunsaturated fatty acids found in brain phospholipids [this study, ˜60 mg of (n‐3) fatty acids/100 g of diet, i.e., ˜130 mg/1,000 kcal]rather than α‐linolenic acid from vegetable oil triglycerides [200 mg of (n‐3) fatty acids/100 g of diet,

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03486.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The aim of this study was to evaluate the effect of citalopram, a second generation antidepressant agent producing no β‐down‐regulation, on the receptors and second messenger systems related to noradrenergic transmission in the cerebral cortex of the rat. We confirmed that citalopram does not bind to α1‐, α2‐, and β2‐adrenoceptors, but we found that it attenuates the inhibitory action of the protein kinase C activator, 12‐O‐tetradecanoylphorbol 13‐acetate, on the noradrenergic response from α1‐adrenoceptor. In contrast to most antidepressants, chronic treatment with citalopram does not produce β‐down‐regulation, but increases the responses to noradrenaline from β‐adrenoceptors without increasing the β1,‐adrenoceptor density. Chronic treatment with citalopram also increases the maximal response from α1‐adrenoceptor. The results indicate that β‐down‐regulation is not a necessary character

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03487.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Mice carrying a mutation in the gene encoding the purine salvage enzyme hypoxanthine‐guanine phosphoribosyltransferase (HPRT) have recently been produced to provide an animal model for Lesch‐Nyhan disease. The current‐studies were conducted to characterize the consequences of the mutation on the expression of HPRT and to characterize potential changes in brain purine content in these mutants. Our results indicate that the mutant animals have no detectable HPRT‐immunoreactive material on western blots and no detectable HPRT enzyme activity in brain tissue homogenates, confirming that they are completely HPRT deficient (HPRT‐). Despite the absence of HPRT‐mediated purine salvage, the animals have apparently normal brain purine content. However, de novo purine synthesis, as measured by [14C]formate incorporation into brain purines, is accelerated four‐ to fivefold in the mutant animals. This increase in the synthesis of purines may protect the HPRT‐mice from potential depletion of brain purines despite complete impairment of HPRT‐mediat

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03488.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The effects of intracellularly generated H2O2on cell viability, morphology, and biochemical markers of injury have been investigated in a clonal cell line of neuronal origin (140‐3, mouse neuroblastoma X rat glioma) as a cell culture model for the role of oxidative stress in the longterm loss of neurons in the brain. The H2O2was generated from the redox cycling of menadione, or by the oxidation of serotonin catalyzed by monoamine oxidase, to simulate the effect of amine neurotransmitter turnover. Incubation with menadione at concentrations as low as 10 γMfor several hours resulted in significant losses of cell viability and altered morphology. Similar effects were evident in the presence of serotonin only after incubation overnight with concentrations>1 mM. The cytotoxicity of either agent was potentiated by preincubation with specific inhibitors of two enzymes important to cellular antioxidant defenses, 3‐amino‐1,2,4‐trazole for catalase and 1,3‐bis(chloromethyl)‐1‐nitrosourea for glutathione reductase. Activity of another antioxidant enzyme of particular importance to antioxidant defenses in brain, the selenoprotein glutathione peroxidase, was stimulated fourfold by growth of cultures in the presence of sodium selenite as a source of active‐site Se for the enzyme. The only effect of the selenite on other functionally coupled antioxidant enzymes was a decrease in activity of superoxide dismutase at concentrations>200 nM. The selenite substantially protected cells against oxidative stress induced by combinations of menadione, 3‐amino‐1,2,4‐trazole, and 1,3‐bis(chloromethyl)‐1‐nitrosourea, but was only marginally effective with serotonin as a source of oxidative stress. The monoamine oxidase inhibitor pargyline increased cell survival in the presence of serotonin, demonstrating the role of this enzyme in its cytotoxicity. DNA damage (single strand breaks), but not lipid peroxidation, correlated with the cy

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03489.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:In the presence of substance P (SP; 10 μM), serotonin (5‐HT; 1 μM) triggered a cation permeability in cells of the hybridoma (mouse neuroblastoma X rat glioma) clone NG 108‐15 that could be assessed by measuring the cell capacity to accumulate [14C]guanidinium for 10‐15 min at 37°C. In addition to 5‐HT (EC50, 0.33 μM), the potent 5‐HT3receptor agonists 2‐methyl‐serotonin, phenylbiguanide, andm‐chlorophenylbiguanide, and quipazine, markedly increased [14C]guanidinium uptake in NG 108‐15 cells exposed to 10 μMSP. In contrast, 5‐HT3receptor antagonists prevented the effect of 5‐HT. The correlation (r= 0.97) between the potencies of 16 different ligands to mimic or prevent the effects of 5‐HT on [14C]guanidinium uptake, on the one hand, and to displace [3H]zacopride specifically bound to 5‐HT3receptors on NG 108‐15 cells, on the other hand, clearly demonstrated that [14C]guanidinium uptake was directly controlled by 5‐HT3receptors. Various compounds such as inorganic cations (La3+, Mn2+, Ba2+, Ni2+, and Zn2+), D‐tubocurarine, and memantine inhibited [14C]guanidinium uptake in NG 108‐15 cells exposed to 5‐HT and SP, as expected from their noncompetitive antagonistic properties at 5‐HT3receptors. However, ethanol (100 mM), which has been reported to potentiate the electrophysiological response to 5‐HT3receptor stimulation, prevented the effects of 5‐HT plus SP on [14C]guanidinium uptake. The cooperative effect of SP on this 5‐HT3‐evoked response resulted neither from an interaction of the peptide with the 5‐HT3receptor binding site nor from a possible direct activation of G proteins in NG 108‐15 cells. Among SP derivatives, [D‐Pro9]SP, a compound inactive at the various neurokinin receptor classes, was the most potent to mimic the stimulatory effect of SP on [14C]guanidinium uptake in NG 108‐15 cells exposed to 5‐HT. Although the cellular mechanisms involved deserve further investigations, the 5‐HT‐evoked [14C]guanidinium uptake appears to be a rapid and reliable response for ass

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03490.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Two monoclonal antibodies C5 and M4 raised against Sarkosyl‐insoluble paired helical filaments (PHF) specifically labeled fetal τ, but hardly labeled normal adult τ. C5 immunoreactivity was eliminated by alkaline phosphatase treatment at 37°C, whereas M4 reactivity could be removed only by the treatment at 67°C. Epitope analysis showed that C5 and M4 recognition sites are in residues 386–406 and 198–250, respectively, according to the numbering of the longest human τ isoform. Thus, the phosphorylation sites are located in the amino‐ and carboxyl‐terminal portions of the microtubule‐binding region. These two well‐characterized monoclonals should be valuable in the identification of a protein kinase(s) that converts n

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03491.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Muscarinic cholinergic and α1‐adrenoceptor‐mediated stimulation of phosphoinositide hydrolysis in rat cerebral cortex were compared by measuring carbachol‐ and noradrenaline‐induced accumulation of various intermediates of the phosphoinositide cycle. Unlike carbachol, noradrenaline in the presence of guanosine 5′‐O‐(3‐thiotriphosphate) did not stimulate phospholipase C activity in brain cortical membranes. In cortical slices, the efficacy of noradrenaline to stimulate accumulation of3H‐inositol phosphates and [32P]phosphatidic acid was 2.5 to threefold that of carbachol. However, noradrenaline was less effective than carbachol in stimulating accumulation of [3H]CDP‐diacylglycerol and resynthesis of phosphatidylinositol. This was not due to calcium inhibition of CTP:phosphatidate cytidyltransferase or to different lithium requirements for carbachol‐ and noradrenaline‐stimulated accumulation of [3H]CDP‐diacylglycerol. The noradrenaline‐induced unbalance of the phosphoinositide cycle, which was most apparent at relatively high concentrations of calcium (2.5 mM) in the incubation buffer, was qualitatively reproduced with ionomycin. The use of the α1a‐subtype‐selective adrenoceptor antagonists WB4101 and 5‐methylurapidil revealed a single α1a‐like component mediating the effects of noradrenaline. Our results suggest that the primary mechanism for phospholipase C activation by brain α1adrenoceptors involves an increase

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03492.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Two molecular mass subtypes of muscarinic receptor are expressed by the chick retina (72 and 86 kDa). During development, the ratio of subtypes changes, with the 72‐kDa form becoming predominant. We have found that subtype switch can occur in retina cell culture, and have investigated factors that influence this in vitro increase in the 72‐kDa receptor. Increases similar to those in vivo occurred when cells were cultured at 105cells/cm2, but not at 10‐fold lower density. High‐density cultures, maintained on coverslips, showed no receptor development when transferred to large volumes of fresh medium, indicating that cell‐cell contact alone was not responsible for induction. However, replacement of fresh medium with conditioned medium (from high‐density cultures) resulted in normal induction. There were no morphological differences between cultures with high and low levels of the 72‐kDa receptor. Conditioned medium also induced 72‐kDa receptors in low‐density cultures, consistent with a minimal role for cell‐cell contact. Efficacy of conditioned medium was markedly dependent on age. Media from cells cultured 1–4 days had no effect, but media from cells cultured 5–8 and 1–8 days elicited 1.6‐fold and fourfold increases in the 72‐kDa subtype, respectively. The data indicate that maturing retina cells secrete developmentally regulated factors that are necessary for abundant expression of the 72‐

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03493.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY