摘要:

Abstract:Primary monolayer cultures of the newborn rat corpus striatum were treated with the phenothiazine trifluoperazine after various times in culture. When the drug is added to cells at least 3 weeks old, concentrations of 10−7and 10−8Mappear morphologically identical to controls but show significant changes in synthesis of acetylcholine and γ‐aminobutyric acid, particularly the former. The results with these very low concentrations suggest that the drug has a highly specific effect directly on striatal cells, and that it is not acting via calm

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09033.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The sequence of molecular events linking depolarisation‐dependent calcium influx to the release of neurotransmitters from nerve terminals is unknown; however, calcium‐stimulated protein phosphorylation may play a role. In this study the incorporation of phosphate into proteins was investigated using an intact postmitochondrial pellet isolated from rat cerebral cortex. The rate and relative incorporation of label into individual phosphoproteins depended on the prelabelling time and buffer concentrations of calcium and phosphate. After prelabelling for 45 min, depolarisation caused a>20% increase in the labelling of 10 phosphoproteins, and this initial increase was maximal with 41mMK+for 5 s, or 30 μMveratridine for 15 s, in the presence of 1mMcalcium. Both agents also led to an initial dephosphorylation of four phosphoproteins. Depolarisation for 5 min led to a significant decrease in the labelling of all phosphoproteins. All of the depolarisation‐stimulated changes in protein phosphorylation were calcium‐dependent. The depolarisation conditions found to optimally alter the phosphorylation of synaptosomal proteins find many parallels in studies on calcium uptake and neurotransmitter release. However, the uniform responses of such a large number of phosphoproteins to the multitude of depolarisation conditions studied suggest that the changes could equally well relate to recovery events such as biosynthesis of neurotransmitters and regulation of intraterminal metabolic

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09034.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Acetylcholinesterase activities and molecular forms were studied in normal and dystrophic 129/ReJ mice, focusing on four predominantly fast‐twitch muscles and the slow‐twitch soleus. The asymmetric and globular forms were analyzed separately so that the effect of dystrophy on each form could be determined. This comparative study showed the following. (1) In the normal condition, each muscle exhibited a distinct distribution of the molecular forms. (2) The diversity among the fast muscles resulted mainly from variations in the proportions of the three globular forms; in contrast, these muscles showed a constant and precise A12/A8/A4ratio. (3) The slow‐twitch soleus clearly differed from the other muscles in its low acetylcholinesterase activity and distinct distribution of the molecular forms, characterized by a low level of G4and a peculiar ratio among its asymmetric forms, resulting from a relative increase of the A8and A4forms. (4) In dystrophic mice, the diversity of the acetylcholin esterase distribution was lost; all the fast muscles displayed profiles exhibiting the characteristics typical of the soleus. The fast‐twitch extensor digitorum longus, sternomastoid, and plantaris converged towards an identical set of acetylcholinesterase molecules. (5) In contrast, the acetylcholinesterase activity and molecular forms of the soleus were only slightly affected by the disease. These results reveal that the dystrophy modifies both categories of molecular forms of acetylcholinesterase in a very precise manner. Such complex changes, which are highly reproducible in a variety of different muscles, are unlikely to result from nonspecific reactions secondary to the

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09035.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The presence of peptides in pure cultures of neurons from 8‐day‐old chick embryo cerebral hemispheres has been investigated by means of specific radioimmunoassays and chromatographic purification. Somatostatin, Met‐enkephalin, Leu‐enkephalin, and substance P immunoreactive substances have been detected in 8‐day‐old cultures grown in serum‐free culture medium. The peptides were present in the cellular extracts, as well as in the culture medium extracts. β‐Endorphin, thyroliberin, luteinizing hormone‐releasing hormone, and ACTH could not be detected. The largest amount was accounted by somatostatin (48 ± 2 ng/mg protein). Some 60% of the somatostatin‐immunoreactive material was found in the culture medium. Met‐enkephalin, Leuenkephalin, and substance P were present at lower concentrations: 1.61 ± 0.27, 0.24 ± 0.02, and 0.14 ± 0.005 ng/mg protein, respectively. The identities of somatostatin‐ and enkephalin‐immunoreactive materials were confirmed by high pressure liquid chromatography. The findings suggest that cultured neurons that express dopaminergic and GABAergic properties contain peptides similar, if not identical, to somatostatin, Met‐enkephalin,

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09036.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Adenosine uptake by cerebral smooth muscle cells is a carrier‐mediated process. TheKmvalue for adenosine uptake is 10.0 μMand theVmaxis 0.95 nmol/ min‐mg cell protein. This uptake system is inhibited by the adenosine analog 2‐chloroadenosine at low adenosine concentrations. These results prove the existence of a nucleoside transport system associated with cerebral smooth

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09037.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The kinetics ofin vivolabeling of cellular free UMP and nucleolar, nucleoplasmic, and cytoplasmic rRNA with [14C]orotate in rat brain and liver were investigated. Evaluation of the experimental data shows: (a) The rate of nucleolar precursors of ribosomal RNA (pre‐rRNA) synthesis and the deduced rate of ribosome formation in brain is about fivefold lower than in liver and corresponds to 220–260 ribosomes/min/nucleus. (b) The lower rate ofin vivopre‐rRNA synthesis is correlated with a lower activity of RNA polymerase I in isolated brain nuclei, (c) The half‐lives of nucleolar rRNA in brain and liver are 210 and 60 min, respectively, thus showing a slower rate of processing of pre‐rRNA in brain nucleoli. (d) The nucleo‐cytoplasmic transport of ribosomes in brain is also markedly slower than in liver and reflects the lower rates of synthesis and processing of pre‐rRNA. (e) Cytoplasmic ribosomes in brain and liver turn over with half‐lives of about 6 and 4 days, respectively. It is concluded that the markedly lower rate of ribosome biogenesis in brain is specified mainly at the level of transcriptio

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09038.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Synaptosomal plasma membranes (SPMs) were prepared from whole rat brain and assayed for calcium‐stimulated proteolytic activity. Addition of calcium to SPMs caused a dose‐dependent increase in trichloroacetic acid‐soluble protein. Two peaks of protease activity directed against a casein substrate were detectable when SPMs were incubated with low‐ionic‐strength buffer and the extract was fractionated on DEAE‐cellulose. The enzyme in peak 1 required less than 1/10 the calcium concentration for activation as the peak 2 protease (Kact1= 35 μM;Aact2= 500 μM). The specific thiol‐protease inhibitors leupeptin and antipain and the alkylator iodoacetate blocked enzyme activity. The low‐sensitivity protease was converted to a high‐sensitivity enzyme (Kact= 20 μM) by substrate affinity chromatography in the presence of calcium. This protease was purified 550‐fold from SPMs. The high‐ and low‐sensitivity membrane‐associated calcium‐dependent proteases are part of a family of enzymes, the calpains, previously reported in cytosoli

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09039.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:An extensive scheme for the subcellular fractionation of myelinating mouse brain is presented. Several centrifugation procedures for the separation of membranes involved in myelinogenesis are critically appraised, and guidelines for selection of centrifugation conditions are given. Characteristics of subcellular fractions are presented in the form of electron micrographs; also presented are distribution of RNA and protein; electrophoretic profiles of membrane proteins, and verification of the myelin‐specific basic proteins, proteolipid protein, and glycoprotein by the immuno‐electroblot technique; and the distribution of eight marker enzyme activities. Myelin‐related membranes were found to differ both qualitatively and quantitatively in their complement of myelin‐specific proteins. These myelin‐containing fractions appear to represent different stages of myeli‐nation that coexist in developing mouse brain. These results provide the fundamental methodologies and background information for kinetic radioisotope analysis of intracellular events in the assembly of myelin presented in a compan

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09040.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The question of developmental relationships amongst myelin‐related membranes in subfractions of myelinating mouse brain (15 days) was investigated by a time‐staggered double isotope protocol using [3H]leucine and [14C]leucine. Preliminary results are interpreted and discussed in the context of a mathematical conceptualization of pulse‐labeling kinetic analyses of myelin proteins in subcellular membrane compartments. Differences in ratio of the two leucine labels among proteins of myelin‐containing subfractions are interpreted as confirming metabolic differences relating to various stages of development rather than precursor‐product relationships. The incorporation into myelin of 14K, 17K, and 18.5K basic proteins (MBPs) occurs with relatively short delay times, following their synthesis (less than 5 min), and seems to occur simultaneously into all compartments. The 21.5K MBP and the proteolipid protein, on the other hand, require 10–14 min and 14–20 min, respectively. A scheme is presented to illustrate the probable assignment of subfractions to various myelin “compartments” during myelination, and to serve as a working hypothesis for studies on precursor‐pr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09041.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:CO2production from exogenous glucose of cortical, whole hippocampal, and CA3 region hippo‐campal slices, as well as O2consumption of whole hippocampal slices, were measured in the presence of different concentrations of kainic acid. A moderate, significant increase of CO2production was seen only in the CA3 region hippocampal preparation at kainic acid concentrations of 10−4–10−2M. The O2consumption, at the expense of endogenous energy stores of whole hippocampal slices, was substantially increased by 10−3Mkainic acid when the slices were incubated without exogenous glucose. The effect was partly paralleled by the use of high (50mM) K+concentration. Some of the possible factors involved in the differential metabolic responses of brain slices to the action of kainic acid are discusse

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb09042.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY