摘要:

Abstract:Cerebral ischemia is one of the most common neurological insults. Many pathological events are undoubtedly triggered by ischemia, but only recently has it become accepted that ischemic cell injury arises from a complex interaction between multiple biochemical cascades. Tissue acidosis is a well established feature of ischemic brain tissue, but its role in ischemic neuropathology is still not fully understood. Within the last few years, new evidence has challenged the historically negative view of acidosis and suggests that it may play more of a beneficial role than previously thought. This review reintroduces the concept of acidosis to ischemic brain injury and presents some new perspectives on its neuroprotective potential.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03589.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Antisera were raised in rabbits against five synthetic peptides. These peptides have been identified as potentially antigenic epitopes from the sequence of porcine choline acetyltransferase (ChAT) using primary and secondary structure analysis. All five antisera recognized immunoaffinity‐purified antigen from porcine brain in an ELISA and on western blots. Four antisera recognized ChAT on dot blots, and another four antisera reacted with native and degraded enzyme in a sandwich ELISA using monoclonal antibodies as the capture antibody. One peptide antiserum was of similar avidity in this sandwich ELISA as a polyclonal antibody raised against immunoaffinity‐purified ChAT. The same antiserum reacted with the enzyme from human placenta in an ELISA and on western and dot blots and recognized ChAT in rat, primate, and human neurons. Thus, a single peptide (amino acids 168‐ 189) provides the means for easy, reliable, and reproducible generation of antibodies against ChAT suitable for replacing conventional polyclonal and monoclonal antib

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03590.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:K+‐evoked acetyl[3H]choline ([3H]ACh) release was inhibited in a concentration‐dependent manner by apomorphine and the D2agonist quinpirole in striatal slices prepared from euthyroid and hypothyroid rats. However, there was a significant increase in the maximum inhibition observed with both agonists in the hypothyroid compared with the euthyroid group, which paralleled the increased D2agonist sensitivity reported for stereotyped behavior. The D2antagonist raclopride decreased, and the D, antagonist SCH 23390 increased, the inhibition of [3H]ACh release by apomorphine, confirming an inhibitory role for D2receptors and an opposing role for D1receptors. Because there is no difference in D1or D2receptor concentration between the euthyroid and hypothyroid groups, it is suggested that thyroid hormone modulation of D2receptor sensitivity affects a receptor‐mediated event. Following intrastriatal injection of pertussis toxin (PTX), apomorphine no longer inhibited [3H]ACh release. In fact, increased [3H]‐ ACh release was observed, an effect reduced by SCH 23390, providing evidence that D1receptors enhance [3H]‐ ACh release, and confirming that a PTX‐sensitive G protein mediates the D2response. As it has been reported that thyroid hormones modulate G protein expression, this mechanism may underlie their effect on dopamine agonist‐ mediated inhi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03591.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:A novel fluorescent Na+indicator, Na+‐binding benzofuran isophthalate (SBFI), was used to follow changes in the intracellular free Na+concentration ([Na+]1) of synaptosomes. The dye, when loaded into synapto‐ somes in the form of its acetoxymethyl ester, was responsive to changes of [Na+]1. Calibration was made using the 340/380 nm excitation ratio when the cytoplasmic Na+concentration was equilibrated with different concentrations of extracellular Na+in the presence of 2 μMgramicidin D. The basal value of [Na+]1in synaptosomes in the presence of 140 mMextracellular Na+was found to be 10.9 ± 1.8 mM.Veratridine, which opens potential‐dependent Na+channels, caused a sudden increase in [Na+]1in a concentration‐dependent manner (1 ‐20 μM), whereas the effect of ouabain (20 and 50 μM), the inhibitor of the plasma membrane Na+,K+‐ATPase, was more gradual. The rise in the fluorescence intensity upon addition of veratridine was prevented completely by 2 μMtetrodotoxin. α‐Latrotoxin, the black widow spider toxin, caused an increase in the fluorescence intensity, which became evident 1 min after the addition of the toxin. The rate of increase was proportional to the concentration of the toxin (0.19–1.5 nM). This report confirms our earlier finding demonstrating a Na+‐dependent component in the action of α‐Iatrotoxin, and shows that changes in [Na+]1in synaptosom

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03592.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Bradykinin‐ and substance P (SP)‐stimulated second messenger studies in isolated subsets of neuroglia showed bradykinin‐stimulated synthesis of phospho‐ inositides (PI) in type‐1 astrocytes and oligodendrocytes. SP‐stimulated PI accumulation was restricted to oligoden‐ drocyte/type‐2 astrocyte progenitor cells and type‐2 astrocytes. These data were confirmed by analysis of calcium transients in single cells. In a regional study, SP‐stimulated PI accumulation in primary astrocyte cultures was restricted to white matter. We conclude that regional heterogeneity in the expression of peptide receptors in cultures of primary astrocytes arises from a restricted distribution on subsets of macroglia. SP receptors restricted on cells of the oligodendrocyte/type‐2 astrocyte type‐2 lineage in vitro, coupled with in vivo observations by others, suggests that SP receptor expression is conserved on subsets of macroglia in vitro and possibly reac

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03593.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:“Synaptodendrosomes” are subcellular fractions that contain pinched‐off axon terminals and dendrites. These fractions are a potential source of RNAs that are localized in dendrites. However, these fractions may also contain RNAs that are seen in situ in neuronal cell bodies and glia. To evaluate whether Synaptodendrosomes could be used as a source of dendritic RNA, we studied the RNA content of this fraction as compared with RNA isolated from total forebrain and a cell body‐enriched fraction. RNA was analyzed by gel electrophoresis, oligo‐dT chromatography, and northern blot hybridization. RNA from Synaptodendrosomes contained a greater proportion of low‐molecular‐weight nonpolyadenylated RNAs. RNAs known to be present in dendrites (mRNA for the a subunit of the calcium/calmodulin‐dependent protein kinase II and the polymerase III transcript BC1) were detected in Synaptodendrosomes; RNAs that are restricted to neuronal and glial cell bodies (mRNAs for the 68‐kDa neurofilament protein, 43‐kDa growth‐associated protein, β‐tubulin, and β‐ actin) were present only at low levels. However, the mRNA for glial fibrillary acidic protein (seen in situ in glial cell bodies and processes) was present at high levels in the synap‐ todendrosomes. These results support and extend previous studies indicating that a limited subset of mRNAs is present in neuronal and astrocyte processes and reveal that both of these types of mRNAs are present in Synaptodendrosomes. Thus, Synaptodendrosomes may be useful as a source of dendritic RNAs, but it will be necessary to develop strategies to subtract mRNAs pr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03594.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Levels of the guanine nucleotide binding proteins G11α and Gqα, which produce receptor regulation of phosphoinositidase C., were measured immunologically in 13 regions of rat central nervous system. This was achieved by immunoblotting membranes from these regions with antisera (CQ series) that identify these two polypeptides equally, following separation of the membranes using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis conditions that can resolve Gqα and G11α. In all regions examined, Gqα was more highly expressed than G11α. Ratios of levels of Gqα to G11α varied between the regions from 5:1 to 2:1. Quantitative measurements of the levels of Gqα and G11α in each region were obtained by comparison with known amounts of purified liver Gqα and G11α and withE. coliexpressed recombinant Gqα. Areas that expressed Gqα highly included olfactory bulb (930 ng/ mg of membrane protein), frontal cortex (700 ng/mg of membrane protein), parietal occipital cortex (670 ng/mg of membrane protein), caudate putamen (1,003 ng/mg of membrane protein), hippocampus (1,045 ng/mg of membrane protein), hypothalamus (790 ng/mg of membrane protein), and cerebellum (950 ng/mg of membrane protein). More modest levels were observed in thalamus (450 ng/mg of membrane protein), pituitary (480 ng/mg of membrane protein), optic chiasma (330 ng/mg of membrane protein), and spinal cord (350 ng/mg of membrane protein). Gna was more evenly expressed with values ranging from about 170 ng/mg of membrane protein in spinal cord and optic chiasma to close to 300 ng/mg of membrane protein in regions expressing high levels of Gqα. A third polypeptide could be identified by the CQ antisera in all brain regions. The possibility that this polypeptide is the α subunit o

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03595.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:Previous studies have shown that cells of the TE671/RD human clonal line express muscle‐type nicotinic acetylcholine receptors (nAChR) and m3‐type muscarinic acetylcholine receptors (mAChR) whose numbers and function are regulated by agonist treatment and second messenger modulation. Here we show that cytochalasin treatment, which causes disruption of actin networks, induces marked changes in the numbers and distribution of nAChR, but not mAChR. Moreover, whereas cytochalasin treatment fails to alter nAChR function significantly, it acutely potentiates mAChR‐mediated phosphoinositide hydrolysis. Treatment of TE671/RD cells with different cytochalasin analogues (rank order efficacy at 5 μg/ml is H>J = B = C = D>A = E) produces a two‐to fourfold increase in numbers of membrane‐bound nAChR (Smaxin units of specific125l‐labeled α‐bungarotoxin binding per milligram of membrane protein). nAChR up‐regulation is evident after 1–2 days of cytochalasin B exposure, is maximal after 3–6 days of drug treatment, and is dominated by an approximately 10‐fold increase (per cell) in an intracellular nAChR pool. Cytochalasin‐induced nAChR up‐regulation is similar in magnitude to, but not additive with, up‐regulation of nAChR following chronic exposure to nicotine or phorbol ester. Northern blot analysis shows a four‐to fivefold coordinate increase in levels of mRNA that encode nAChR α, β, γ, or θ subunits in cytochalasin‐treated cells, suggesting that nAChR up‐regulation has a possible transcriptional basis. Studies done using a86Rb+efflux assay indicate that cytochalasin treatment has no significant effect on nAChR function. By contrast, cytochalasin treatment has no effect on the numbers of mAChR as assessed by binding studies with the radioantagonist3H‐labeled quinuclidinyl benzilate, but it induces marked enhancement of carbachol‐stimulated, but not basal, phosphoinositide hydrolysis. These studies suggest that presumed modulation by cytochalasin treatment of cytoskeletal microfilament integrity can differentially influence expression and function of mAChR (a prototype of the metabotropic receptor superfamily) and nAChR (a prototype of the ligand‐gated ion‐channel superfamily). The results also suggest possible new roles for the cytoskeleton in regulation of membran

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03596.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:A dramatic, time‐dependent loss ofl‐glutamine was observed in mouse and rat hippocampal slices equilibrated in normal artificial CSF under static (no‐flow) and super‐fused (constant‐flow) conditions. Concomitant with the decline inl‐glutamine, there was a significant, but less pronounced, decrease in levels of the neurotransmitter amino acids, γ‐aminobutyric acid,l‐aspartate, andl‐glutamate. The disappearance ofl‐glutamine was a result of diffusion from the tissue to the artificial CSF rather than chemical or biochemical transformation. The loss of amino acids from the hippocampal slices was prevented to different degrees by the addition of 0.5 mMexogenousl‐glutamine to the artificial CSF. The levels of newly synthesized amino acids were also determined, because they may be more indicative of the neuronal activity than the total tissue levels of amino acids. The effects of perturbations in glutamine (length of the equilibration time and addition of exogenous. glutamine) on newly synthesized glutamate were more pronounced under 4‐aminopyridine‐stimulated than control (unstimulated) conditions. Therefore, a loss ofl‐glutamine from the hippocampal slices may have neurophysiological effects and wa

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03597.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract:The sequence of a high molecular weight (HMW) τ cDNA cloned from a neuroblastoma N115 library contains, in addition to the C‐and N‐terminal and middle regions present in the low molecular weight mouse brain τ proteins, a 711‐bp nonhomologous domain (exon 4a) and a region of 198 bp corresponding to exon 6 of the τ gene. Protein immunoblot analysis, performed with antibodies specific either for a sequence present in the N‐terminal region of all the τ variants or for exon 4a revealed several bands suggesting that more than one τ form is expressed in this cell line. Northern blot experiments performed with a number of cDNA probes spanning domains common and uncommon to low molecular weight and HMW τ allowed the identification of four τ transcripts differing in the size of their coding and noncoding regions. All these transcripts contain the sequence encoded by exon 6, but two of them lack exon 4a. As shown by RNase protection assays, the N‐terminal region of these transcripts is also variable and contains either exon 1, or exons 1 and 2, or exons 1–3. Yet all these HMW τ forms contain four homologous repeats in their C‐terminal domain both in the differentiated and nondifferentiated cells, i.e., have adult characteristics. In conclusion, the data reported in this article demonstrate that several HMW τ variants are expressed in neuroblastoma N115 cells and that the transition between immature to mature τ forms occurring during brain development is not required for neurite outgrowth during morphological differenti

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1993.tb03598.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY