摘要:

Abstract—Drugs such as cocaine, procaine, pheniprazine (Catron) and veratridine, which have actions on sympathetic nerves and nerve terminals, were examined for their ability to increase serotoninN‐acetyltransferase (EC 2.3.1.5; NAT) in pineal organ culture. The absence of potassium (0 KCl) was also examined. NAT is known to respond to β‐adrenergic stimulation. It was found that these drugs and 0 KCl increased the enzyme activity 100 to 2000‐fold in innervated pineals but had virtually no effect in denervated pineals. The effects on innervated pineals were blocked by the β‐blocker propranolol but not by the α‐blocker, phentolamine. These drugs and 0 KCl inhibited to varying degrees [3H] 1‐norepinephrine uptake in pineals. It is concluded that these agents activated the β‐adrenergic receptor on pineal cells by causing an accumulation of extraneuronal norepinephrine. The accumulation of norepinephrine is due, at least in part, to the blockade of norepinephrine reuptake by nerve terminals.The ability of veratridine to stimulate NAT and to inhibit norepinephrine uptake was reversed by tetrodotoxin, a blocker of sodium permeability in excitable tissue, thus veratridine acts by increasing sodium permeability in nerve terminals. This adds support to the theory that catecholamine uptake is a process that requires a sodium gradient across the nerv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11580.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—An enzymatic isotopic assay for the measurement of β‐phenylethylamine in brain, with a sensitivity of 100‐200 pg, has been developed. With this assay, the endogenous β‐phenylethylamine content (1.5 ng/g) in the rat brain has been determined. Phenylalanine administration increases the brain levels of this amine; inhibition of monoamine oxidase causes a 40‐fold increase in brain β‐phenylethylamine. After a combined treatment with a monoamine oxidase inhibitor and phenylalanine, the β‐phenylethylamine content in the brain increases to about 400‐fold. This increase can be blocked by the central decarboxylase inhibitor NSD‐1055. p‐Chlorophenylalanine also increases β‐phenylethylamipe concentration in the brain, and this effect is potentiated by a simultaneous admin

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11581.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—A toxin purified from crude venom of the scorpionL. quinquestriatusreleases [3H]norepinephrine from synaptosomes prepared from rat brain. The toxin‐induced release is dependent on duration of exposure and concentration of toxin in the medium. The absence of calcium in the medium diminishes toxin‐induced release but does not abolish it. Toxin‐induced release is diminished by tetrodotoxin or, to a lesser extent, by desmethylimipramine. Since the released tritium is present predominantly as norepinephrine, it appears that toxin‐induced release is similar to that produced by veratradine or tyramine and is distinct from reserpine induce

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11582.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Polysomes prepared from rat cerebral microsomes, following preincubation with a high concentration of puromycin (2.5 mM) in the presence of rat liver soluble enzymes, were very similar to normal polysomes in yield, A 260nm:A 280nmratio and in absorbance profile on sucrose density gradients. However, the capacity for amino acid incorporation was inhibited by more than 50 per cent by puromycin treatment. The extent of inhibition far exceeded what could be expected from the amount of residual puromycin bound to polysomes, suggesting that some essential step in polypeptide synthesis was damaged. An examination of the labelled polypeptides, using sucrose density gradient centrifugation, showed that most of the new chains synthesized by puromycin‐polysomes were released into solution. However, small amounts of polypeptides of high specific radioactivity were distributed among the polysomal aggregates. In contrast to normal polysomes, the specific radioactivity of puromycin polysomes was the highest in aggregates of six or more ribosomes and declined sharply at the levels of trimers and dimers. It is suggested that cerebral polysomes pretreated with puromycin become defective in the termination mechanism with the consequence that even though they are capable of moving at least short distances on the messenger RNA and of releasing the polypeptide chains formed, a concomittant release of monomeric ribosomes is obstructed. This may result in the‘clogging’of the terminus of the mRNA, thus blocking further polypeptide sy

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11583.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Activities of rat brain galactosylsphingosine (psychosine) and galactosylceramide (galactocerebroside) galactosyl hydrolases were compared using several criteria. Aqueous homogenates of rat brain were extracted at ‐30°C with a mixture of ether‐methanol (3:1, v/v). This procedure eliminated most of endogenous galactosylceramide and improved the linearity of the enzymatic reaction without inactivating the enzyme. The thermostability of both enzymes was identical while the reference 4‐methylumbelliferyl β‐galactosidase was less thermostable. The enzymes, solubilized from the ether‐methanol powder, were quantitatively precipitated in the combined ammonium sulphate fractions of 20–30% and 30–40% saturation. DEAE‐cellulose column chromatography gave identical elution patterns for the two enzymes, with a single major and two minor peaks. Electrofocusing of the major activity peak, obtained from the DEAE‐cellulose column, produced a sharp single peak of galactosylsphingosine‐ and galactosylceramidehydrolysing activities at an isoelectric point of pH 4.45. Developmental changes of these enzymes were identical, showing the most rapid rise concomitant with the period of active myelination. During development, at different purification steps, and in different organs, the ratio of the activities of galactosylsphingosine and galactosylceramide galactosyl hydrolases was relatively constant. While none of these criteria provides definitive proof of identity, they collectively suggest strongly that a single enzyme might catalyse hydrolysis of both galactosylsphingosine

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11584.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—S‐100 protein has been found in the nuclei isolated from the brain cortex of rabbit. The nuclear S‐100 constitutes a small portion (0.55 per cent) of the S‐100 present in the cytosol. Most of the large and pale nuclei appear to contain much more S‐100 than the small and dark ones. The nuclear membrane is permeablein vitroto S‐100 in presence of divalent cations. Three forms of S‐100 occur in subnuclear fractions: free S‐100, present in the soluble protein fraction; labile‐bound S‐100, present in the deoxyribonucleoprotein fraction and stable‐bound S‐100, present in the residual or‘nucleolar’fraction. The localization of the S‐100 in those regions of the nucleus that are most active in RNA synthesis provides basic information for further studies on the possible role of this protein on genomic

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11585.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The optic system ofScardinius erythrophthalmushas been used to study the axonal translocation of radioactivity from [3H]glucose. Intraocularly injected precursors were transported intra‐axonally along the optic nerve towards the contralateral optic tectum. In comparison with the well known properties of axonal protein transport there were remarkable differences in the proximo‐distal translocation of [3H]glucose. These were: (1) a delay in the labelling of the structures investigated, after tracer application; (2) only a rapid phase of transport; and (3) no accumulation of radioactivity in the region of nerve terminals in the optic tectum connected with the injected eye. The transported material was almost exclusively in the form of TCA‐soluble compounds and was mainly glucose itself or its low molecular derivatives, but not glycogen. The rate of transport was decreased by lowered temperatures and was not immediately dependent on retinal protein synthesis. Colchicine blocked the axonal transport of glucose by up to 60–70

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11586.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Cerebrosides, sulphatides and sphingomyelin were isolated from bovine CNS myelin and from myelin‐free axons derived from myelinated axons. The fatty acid composition of each sphingolipid was determined by gas‐liquid chromatography of the fatty acid methyl esters. In each case the fatty acids of the axonal sphingolipids were of shorter average chain length than those from the corresponding myelin lipids. These differences, however, were small and the fatty acids of the axonal cerebrosides and sulphatides were similar in average chain length to those reported previously for bovine myelin. The principal unsubstituted acid of both cerebroside and sulphatide from axons was 24: 1, with the total long chain acids (>C18) amounting to 80 and 85 per cent, respectively. The corresponding figures for myelin galactolipids were 94 and 95 per cent long chain acids. The principal α‐hydroxy acid of both axonal galactolipids was 24 h:0, with cerebroside having 80 per cent and sulphatide 92 per cent long chain acids, compared to the figures of 87 and 97 per cent for the corresponding myelin lipids. In axonal sphingomyelin the major acid was 18:0 (compared to 24:1 in myelin) and the long chain acids were 61 per cent of the total vs 76 per cent of the total for myelin sphingomyelin. The non‐identity of axonal and myelin sphingolipid fatty acids substantiates the belief that they are intrinsic axonal constituents. These findings do not rule out the possibility of a close metabolic relationship between the sphingolipids of the axon and its mye

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11587.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Bovine axons derived from myelinated CNS axons were found to have 13.5% lipid. This lipid was composed of 20.1% cholesterol, 20.1% galactolipid, 14.6% ethanolarhine phosphatides (56.4% in the plasmalogen form), 18.3% choline phosphatides (10.0% in the plasmalogen form), 9.3% sphingomyelin, 5.6% phosphatidyl serine and 3.4% phosphatidyl inositol. The bovine axons had 0.33 μg ganglioside NeuNAc/mg dry weight. The axon gangliosides were found to contain the four major types of bovine gangliosides, as well as gangliosides GM2and GD3. The latter two amounted to 20.9 and 15.8 mole per cent respectively, of total gangliosides. On a molar basis, about one half of the gangliosides were monosialogangliosides, with a decreased contribution by gangliosides GT1and GD1brelative to ganglioside distributions which have been reported for most other CNS components. The relationship of the bovine axonal lipid composition to bovine white matter and its constituents, as well as to other CNS and PNS axonal preparations is discuss

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11588.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—High concentrations of dopamine were found in thenucleus accumbensand olfactory tubercle of the rat brain using a radiochemical enzymatic assay technique. An active uptake system for [3H]dopamine that is temperature sensitive and dependent on external sodium ions is present in synaptosome‐rich homogenates of these two brain areas. This uptake process is potently inhibited by benztropine (IC50= 2.0 × 10‐7m). Dextroamphetamine d was 4.5 times more potent than 1‐amphetamine in inhibiting dopamine uptake in thenucleus accumbensand six times more potent in the olfactory tubercle andcorpus striatum. Low concentrations of dopamine caused an increase in adenosine 3′5′‐monophosphate (cyclic AMP) formation in homogenates of both thenucleus accembensand olfactory tubercle. This effect was potently blocked by chlorpromazine. The α‐adrenoceptor antagonist phentolamine weakly antagonized the stimulation of this adenylate cyclase by dopamine, but the β‐adrenoceptor antagonist

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb11589.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY