摘要:

Abstract:For the purpose of demonstrating the action of taurine as a neuromodulator in addition to its suggested neurotransmitter function, the effects of taurine and muscimol on the depolarization‐induced Ca‐dependent release of [3H]γ‐aminobutyric acid (pH]GABA) andl‐[3H]glutamate in cerebellar slices from guinea pigs were investigated. The release of [3H]GABA was found to be greatly decreased by a GABA agonist, muscimol, and by taurine, but not by glycine. The release ofl‐[3H]glutamate was little affected by taurine. The release of [3H]GABA was enhanced by bicuculline and strychnine, but not by picrotoxin, and the suppressive action of muscimol on the GABA release was antagonized by bicuculline, picrotoxin, and strychnine, suggesting the possible existence of presynaptic autoreceptors for GABA in the cerebellum. The suppressive action of taurine on the release of [3H]GABA, on the other hand, was blocked only by bicuculline. These results suggest that taurine reduced the release of [3H]GABA from cerebellar slices by acting on the GABA autoreceptors or, more likely, on other types of receptors that are sensitive to bicuculline. As a possible mechanism for this modulatory action of taurine, the blockade by this amino acid of the influx of Ca2+into cerebellar tissues was tentatively

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12645.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Ammonia, amino acids (AA), and middle molecules (MM) have been implicated in the pathogenesis of experimentally induced acute hepatic coma in the pig. Hemodialysis (HD) using either a low‐ (Cuprophan = CU) or a high‐permeability (polyacrylonitrile = AN 69°) membrane has demonstrated the role of MM. Selective hemodialysis (SHD) of AA or NH3and MM was performed by adding either NH3(group I) or AA (group II) to the dialysate during AN 69 HD; for MM, SHD only was performed by adding NH3and AA to the dialysate (group III). In group I the brain levels of tyrosine were similar to those in undialyzed animals with decreased striatal dopamine and decreased norepinephrine in the midbrain only. Brain tryptophan was higher than normal, but brain levels of 5‐hydroxytryptamine and 5‐hydroxyindoleacetic acid (5‐HT, 5‐HIAA) were within normal limits. In group II, despite an efficient NH3clearance, brain NH3levels were as high as in group I and did not correlate with plasma levels. Brain tyrosine (despite tyrosine overload of the dialysate) was lower than in group I; striatal dopamine decreased (but to a lesser extent than in group I), and norepinephrine was normal. Brain tryptophan was higher than normal, with an increase in brain 5‐HT and 5‐HIAA. In group III, results were similar to group I, except for a limited increase of 5‐HT in the pons. Brain octopamine levels increased only in undialyzed and CU‐HD animals, demonstrating a specific relation with MM. These experiments demonstrate the interrelationship between NH3and neutral AA with regard to passage through the blood‐brain barrier and to in

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12646.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The amounts of β‐endorphin‐ and Met‐enkephalin‐immunoreactive material are higher in the pituitary of aged rats. However, the aging process decreases the content of βendophin‐, but does not affect that of Met‐enkephalin‐immunoreactive material, in hypothalamus. Thus, it seems that the regulatory mechanisms in the two areas are differentially affected by increasing age. On the other hand, the pituitary increase of these peptides is in line with the assumption that in the elderly the hormonal response to str

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12647.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The intraaxonal transport of phospholipids in regenerating hypo‐glossal nerve of the rabbit was investigated by administration of labeled lipid precursors into the medulla oblongata. At various time intervals after crushing the left hypoglossal nerve at the level of the digastric muscle, a mixture of 60 MCi of [2‐3H]glycerol and 15 /μCi of [1‐14C]palmitate, dissolved in 15% bovine serum albumin, was injected into the calamus scriptorius of the fourth ventricle. The amount and the pattern of labeling of glycerophospholipids synthesized in the motor neurons were determined. Three days after nerve crush there was an accumulation of labeled glycerophospholipids immediately proximal to the injury site. Seven days after crushing, the regenerating nerve incorporated rapidly transported labeled lipids in greater amounts than the contralateral normal nerve; the incorporation was elevated along the entire length of the nerve containing both regenerating axons and the post‐crush sprouting terminals. The difference between the two sides increased up to 14 days, but disappeared as regeneration proceeded (21‐45 days). The “pool” of radioactive lipids remaining in the cell bodies of hypoglossal nuclei, in the segments of nerve, both proximal and distal to the crush site, and in all the segments of uncrushed nerve was similar 6–12 h after labeling. Among the phospholipids, the highest3H and14C radioactivity was observed in phos‐phatidylcholine and phosphatidylethanolamine. These results support the hypothesis than an increase in the amount of glycerophospholipids, conveyed by rapid axonal transport, takes place in the first 2 weeks during nerve regeneration. The increased transport of lipids presumably reflects an augmented demand for membrane precursors during the

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12648.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Axonal transport of phospholipids in normal and regenerating sciatic nerve of the rat was studied. At various intervals after axotomy of the right sciatic nerve in the midthigh region and subsequent perineurial sutures of the transected fascicles, a mixture of 60 μCi [Me‐HC]choline and 15 μCi [2‐3H]glycerol in the region of the spinal motor neurons of the L5 and L6 segments was injected bilaterally. The amount of radioactive lipid (and in certain cases its distribution in various lipid classes) along the nerve was determined as a function of time. Three days after fascicular suture and 6 h after spinal cord injection of precursors, there was an accumulation of labeled phospholipids and sphingolipids in the transected sciatic nerve in the region immediately proximal to the site of suture. Nine days after, there was a marked increase in the accumulation of radioactivity in the distal segments of the injured nerve, which increased up to 14 days after cutting and disappeared as regeneration proceeded (21–45 days). In all segments of both normal and regenerating nerve fibers, as well as in L5 and L6 spinal cord segments, only phosphatidylcholine and sphingomyelin were labeled with [14C]choline. These results suggest that the regeneration process in a distal segment of a peripheral neuron, following cutting and fascicular repairing by surgical sutures, is sustained in the first 3 weeks by changes in the amount of phospholipids rapidly transported along the axon towards the site of nerve fiber ou

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12649.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The effect of prolonged exposure to light on the activity of dopaminergic neurons and dopamine (DA) metabolism of chick retinae was investigated. α‐Fluoromethyldopa, a potent and specific irreversible inactivator of aromatic amino acid decarboxylase, was used to assess DA turnover after inhibition of synthesis, and also to assessin vivotyrosine hydroxylase activity by dihydroxyphenylalanine accumulation. After 48 h of light exposure, retinal DA in 12‐day‐old chicks was about 30% higher (p<0.005) whereas dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were elevated two to three times (p<0.005) the level of controls kept in the dark for the same period. DA turnover was about twofold faster in the light (t1/2= 31 min) than in the dark (t1/2= 65 min). Tyrosine hydroxylase, assayedin vitrowith saturating levels of cofactor and substrate, increased by about 50% after light exposure. The apparent tyrosine hydroxylase activityin vivowas approximately sixfold higher in the light than the dark. These results are interpreted and discussed in terms of the regulation of DA synthesis, and the use of DOPAC and HVA as indices of DA function in the

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12650.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:P2protein, a myelin‐specific protein, was detected immunocyto‐chemically and biochemically in rabbit central nervous system (CNS) myelin. P2protein was synthesized by rabbit oligodendrocytes and was present in varying amounts throughout the rabbit CNS. Comparison of P2and myelin basic protein (MBP) stained sections revealed that P2antiserum did not stain all myelin sheaths within the rabbit CNS. The proportion of myelin sheaths stained by P2antiserum and the amount of P2detected biochemically were greater in more caudal regions of the rabbit CNS. The highest concentration of P2protein was found in rabbit spinal cord myelin, where P2antiserum stained the majority of myelin sheaths. P2protein was barely detectable biochemically in myelin isolated from frontal cortex, and in sections of frontal cortex only occasional myelin sheaths reacted with P2antiserum. These results suggest that the regional variations in the amount of P2protein are due to regional differences in the number of myelin sheaths that contain P2protein. P2protein was detected immunocytochemically and biochemically in rabbit sciatic nerve myelin. Immunocytochemically, P2antiserum only stained a portion of the myelin sheaths present. The myelin sheaths not reacting with P2antiserum had small diameters and represented less than 10% of the total myelinated fib

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12651.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The calcium binding protein calmodulin and the opiate receptor binding sites are unevenly distributed in various subcellular fractions of neuroblastoma‐glioma NG108‐15 cells. The crude mitochondrial‐membrane fraction of these cells contains two membrane fractions that are separable by sucrose gradient centrifugation. These two differ in the content of both calmodulin and opiate receptors. Leucine enkephalin andd‐Ala2‐methionine enkephalinamide decrease the amount of membrane‐bound calmodulin in the NG108‐15 cells in a time‐ and dose‐dependent manner, whereas the opiate antagonists naloxone and levallorphan have an opposite effect. Naloxone blocks the effect of leucine enkephalin and dextrallorphan has no significant effect. The opiate alkaloids entorphine and phenazocine induce changes similar to that of the enkephalins whereas morphine is inactive even at high concentrations. The alteration in the amount of membrane‐bound calmodulin after a short incubation (15 min) with the enkephalins or with naloxone is reflected as an opposite change in the amount of calmodulin in the cell cytosol. Naloxone and levallorphan also increase the number of opiate receptors in NG108‐15 cells but dextrallorphan has no such effect. Modulation of the intracellular distribution of calmodulin by opioid peptides and alkaloids may control the activity of various membrane‐bound and cytosolic systems that are calmodulin‐

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12652.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Primary cultures were prepared from newborn rat brain. After 16‐18 days, they consisted mainly of mature and immature astrocytes and oligodendrocytes, as judged by immunohistochemistry. To study the metabolism of ethanolamine glycerophospholipids, the cells were incubated with 1‐[1‐3H]alkyl‐sn‐glycero‐3‐phosphoethanolamine (1‐alkyl‐GPE), for 1–20 h. Five main products were formed: 1‐alkyl‐2‐acyl‐GPE; 1‐alkyl‐2‐acyksn‐glycero‐3‐phosphocholine (1‐alkyl‐2‐acyl‐GPC); 1‐alkenyl‐2‐acyl‐GPE (ethanolamine plasmalogen); 1‐alkenyl‐2‐acyl‐GPC (choline plasmalogen); and 1‐alkyl‐glycerol. Acylation of the substrate was the main reaction during the first 3 h of incubation, whereas desaturation to plasmaiogen reached a maximum after 12 h. Greater amounts of radioactivity were observed in the phosphatidylcholine fraction after longer incubation times. Only small amounts of choline plasmalogen were observed. The phosphatidylethanolamine fraction consisted of 26.5% diacyl‐, 27.5% alkyl‐acyl‐, and 46.0% alkenyl‐acyl‐ compounds, whereas the corresponding data for the phosphatidylcholine fraction were 78.5, 16.4, and 5.1%, respectively, after 20 h of inc

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12653.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Glycine uptake was investigated in cultured Y79 retinoblastoma cells containing different degrees of phospholipid fatty acid unsaturation. The modifications were produced by growing the retinoblastoma cells in medium supplemented with various unsaturated fatty acids. Glycine was taken up by the retinoblastoma cells through two kinetically distinguishable processes. The high‐affinity system is totally dependent upon extracellular Na+and partially dependent upon Ca2+. Of the glycine taken up by retinoblastoma cells, 85–90% remains as free intracellular glycine and less than 3% is incorporated into cellular protein. When the cells are grown in a medium containing 10% fetal bovine serum as the only source of fatty acids, the phospholipids contained 23% polyunsaturated fatty acids. Under these conditions the high‐affinity system has aK′mof 34.2 ± 3.7 μMand a V′maxof 91.2 ± 16.2 pmol min−1mg protein−1. The low‐affinity system has aK′mof 2.7 ± 0.4 mMand aV′maxof 4.1 ± 0.5 nmol min−1mg protein−1. When the polyunsaturated fatty acid content of the phospholipids was increased by supplementing the medium with linolenic or docosahexaenoic acids (n‐3 polyunsaturates) or linoleic or arachidonic acids (n‐6 polyunsaturates), theK′mandV′maxof the high‐affinity glycine uptake system were increased three‐ to fourfold. By contrast, supplementing the medium with oleic acid, an n‐9 monounsaturate, did not significantly alter theK′morK′maxfor glycine uptake. The results with this model system suggest that one of the effects of the high polyunsaturated fatty acid content normally present in neural cell membranes may be a modulation of the high‐affinity transport system so that it functio

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12654.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY