摘要:

Abstract:Highly purified rat brain myelin showed a significant level of ethanolamine kinase, amounting to 17% of the specific activity of whole brain homogenate. This kinase level in myelin was an order of magnitude higher than that of lactate dehydrogenase, a marker for cytosol. Subcellular distribution studies revealed that in addition to myelin, this kinase was present in the P1, P2, P3, and cytosolic fractions with highest relative specific activity in the latter. The possibility that myelin activity resulted from adsorption of the soluble enzyme was unlikely since activity was retained in myelin that had been washed with buffered sodium chloride or taurocholate. Mixing experiments and repeated purification further indicated that the enzyme is intrinsic to myelin. Kinetic studies indicated similarKmvalues for ethanolamine in the microsomal, cytosolic, and myelin fractions but a significantly lower apparentKmfor ATP in myelin. This and other differences suggested the possible existence of isozymes. Establishment of the presence of this kinase completes the list of phospholipid synthesizing enzymes needed to synthesize phosphatidylethanolamine from diacylglycerol within the myelin membrane.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13119.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Indices of presynaptic serotonergic nerve endings were assayed in neocortical biopsy samples from patients with histologically verified Alzheimer's disease. The concentrations of 5‐hydroxytryptamine (serotonin) and 5‐hydroxyindoleacetic acid, serotonin uptake, and K+‐stimulated release of endogenous serotonin were all found to be reduced below control values. Changes occurred in samples from both the frontal and temporal lobes, but they were most severe (at least a 55% reduction) in the temporal lobe. This is indicative of substantial serotonergic denervation. Values for serotonergic markers in Alzheimer's disease samples did not show correlations with rating of the severity of dementia, indices of cholinergic innervation, or senile plaque and cortical pyramidal neurone loss. However, neuronbrillary tangle count and an index of glucose oxidation (both probably reflecting pyramidal cells) correlated with the concentration of 5‐hydroxyindoleacet

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13120.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A procedure is reported that allows the purification and amino terminal sequencing of pig brain choline acetyltransferase. The enzyme (present in extremely low amounts in this tissue) is eluted together with its antibody from an affinity column by a mild pH shift and the resulting enzyme‐antibody complex separated by gel electrophoresis. The band corresponding to the enzyme is electroeluted from the gel using volatile solutions allowing the direct determination of the amino acid composition and partial sequence. The first 11 residues are: Pro‐IIe‐Leu‐Glu‐Lys‐Thr‐Pro‐

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13121.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A monoclonal antibody (mAb), termed BBS/NC/VI‐H14 (H14), that reacts with the human enzyme γγ‐enolase was prepared. It was directed against the γ‐subunit and did not cross‐react with the α‐ or β‐subunit. The mAb H14 can be used for quantitative determination of γγ‐enolase in a two‐site immunoradiometric assay (two‐site IRMA). It is also suitable for immunostaining formalin‐fixed tissues. The specific identification of γγ‐enolase provided by the two‐site IRMA with H14 is discussed in relation to the cellu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13122.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Incubated slices and freshly dissociated cells from 8‐day‐old rat cerebellum were used to try to identify the cells that participate in the large increases in cyclic GMP levels that follow activation of excitatory amino acid receptors in this tissue. In the slices, cyclic GMP responses to L‐gluta‐mate and related excitants were unaffected by tetrodotoxin and could be replicated by the guanylate cyclase activator nitroprusside. Nitroprusside and the receptor agonists appeared to activate the same pool of the enzyme. Prior destruction of neuroblasts, deep nuclei, or Golgi neurones did not cause loss of responses to L‐glutamate. If granule cells were rendered necrotic, however, the cyclic GMP responses to all excitants tested were reduced by ≧ 90%. Substantial losses of responses to veratridine and high K+levels also occurred, but the nitroprusside‐induced elevations were unaffected. In dissociated cell suspensions, the magnitude of responses to receptor agonists, but not those to nitroprusside, was markedly dependent on cell concentration. Responses to L‐glutamate were the same in cell suspensions that were Purkinje cell depleted and Purkinje cell enriched. It is concluded that granule cells are primarily involved in the cyclic GMP responses to excitatory amino acids but that the cyclic GMP accumulations occur elsewhere, probably

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13123.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Sodium‐dependent high‐affinity choline uptake was measured in various regions of the brains of rats irradiated for 45 min with either pulsed or continuous‐wave low‐level microwaves (2, 450 MHz; power density, 1 mW/cm2; average whole‐body specific absorption rate, 0.6 W/kg). Pulsed microwave irradiation (2‐μs pulses, 500 pulses/s) decreased choline uptake in the hippocampus and frontal cortex but had no significant effect on the hypothalamus, stria‐turn, and inferior colliculus. Pretreatment with a narcotic antagonist (naloxone or naltrexone; 1 mg/kg i.p.) blocked the effect of pulsed microwaves on hippocampal choline uptake but did not significantly alter the effect on the frontal cortex. Irradiation with continuous‐wave microwaves did not significantly affect choline uptake in the hippocampus, striatum, and hypothalamus but decreased the uptake in the frontal cortex. The effect on the frontal cortex was not altered by pretreatment with narcotic antagonist. These data suggest that exposure to low‐level pulsed or continuous‐wave microwaves leads to changes in cholinergic fu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13124.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Photolabeling of the benzodiazepine receptor, which to date has been done with benzodiazepine agonists such as flunitrazepam, can also be achieved with Ro 15‐4513, a partial inverse agonist of the benzodiazepine receptor. [3H]Ro 15‐4513 specifically and irreversibly labeled a protein with an apparent molecular weight of 51, 000 (P51) in cerebellum and at least two proteins with apparent molecular weights of 51, 000 (P51) and 55, 000 (P55) in hippocampus. Photolabeling was inhibited by 10 μM diazepam but not by 10 μM Ro 5‐4864. The BZ1receptor‐selective ligands CL 218872 and ß‐carboline‐3‐carboxylate ethyl ester preferentially inhibited irreversible binding of [3H]Ro 15‐4513 to protein P51. Not only these biochemical results but also the distribution and density of [3H]Ro 15–4513 binding sites in rat brain sections were similar to the findings with [3H]flunitrazepam. Thus, the binding sites for agonists and inverse agonists appear to be located on the same pro‐teins. In contrast, whereas [3H]flunitrazepam is known to label only 25% of the benzodiazepine binding sites in brain membranes, all binding sites are photolabeled by [3H]Ro 15‐4513. Thus, all benzodiazepine receptor sites are associated with photolabeled proteins with apparent molecular weights of 51, 000 and/or 55, 000. In cerebellum, an additional protein (MW 57, 000) unrelated to the benzodiazepine receptor was labeled by [3H]Ro 15‐4513 but not by [3H]flunitrazepam. In brain sections, this component contributed to higher labeling by [3H]Ro 15–4513 in the granu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13125.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Neuroblastoma cells were used to determine the effect of high carbohydrate and polyol levels onmyo‐inositol metabolism. The presence of elevated concentrations of glucose or sorbitol caused a significant decrease in both inositol accumulation and incorporation into phospholipid. These conditions, however, did not alter the accumulation of the other phospholipid head groups or the growth rate and water content of the cells. Two weeks of growth in either of the modified conditions was necessary to obtain a maximal effect on inositol incorporation. In contrast, growth in elevated concentrations of fructose, mannitol, or dulcitol had no effect on inositol metabolism. The reduced inositol accumulation and incorporation into lipids seen with glucose or sorbitol supplementation resulted in a decrease in the total phosphatidylinositol content of the cell without changing the levels of the other phospholipids. Kinetic analysis of cells grown in the presence of elevated glucose indicated that V1maxfor inositol uptake was significantly decreased with little change in the K1max. These data suggest that glucose decreases myo‐inositol uptake in this system by noncompetitive inhibition. Cells grown in the presence of increased glucose also had elevated levels of intracellular sorbitol and decreased levels ofmyo‐inositol. These results suggest that the high levels of glucose and sorbitol which exist in poorly regulated diabetes may be at least partially responsible for diabetic neuropathy via a reduction in the cellular content of myo‐inositol and phosphatidylinositol. This system may be a useful model to determine the effect of reduced inositol phospholipid levels on neural cell f

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13126.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A 4‐year old boy died of diffuse disseminated sclerosis (DDS) of the brain and was found to have also pseudo‐arylsulfatase A deficiency (PASAD) with about 20% residual arylsulfatase A (ASA) and cerebroside sulfatase (CS) activity. The reexamination of lipids did not show any sulfatide accumulation in the patient's organ extracts. Although the residual CS activity in the patient's extracts was clearly demonstrable only after partial purification, it was concluded that this activity protects organ tissues from sulfatide accumulation in PASAD, since in sulfatide lipidosis (metachro‐matic leukodystrophy, MLD) no residual CS activity was detectable. The study of residual ASA activity in the patient's fibroblasts by gel electrofocusing resulted in an almost normal enzyme microheterogeneity. However, the detailed study of the brain galactolipids in the patient revealed an elevated ratio of sulfatide/galactocerebroside content, despite the decrease of both lipids. In tissues of other patients with severe demyelinating diseases different from DDS and MLD, this galactolipid ratio was also found to be increased, especially in three patients with adrenoleukodys‐trophy. A general mechanism of this anomaly in severe de‐myelination is c

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13127.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:In the absence of its cofactor, pyridoxal 5′‐phosphate (pyridoxal‐P), glutamate decarboxylase is rapidly inactivated by aspartate. Inactivation is a first‐order process and the apparent rate constant is a simple saturation function of the concentration of aspartate. For the β‐form of the enzyme, the concentration of aspartate giving the half‐maximal rate of inactivation is 6.1 ± 1.3 mM and the maximal apparent rate constant is 1.02 ± 0.09 min−1, which corresponds to a half‐time of inactivation of 41 s. The rate of inactivation by aspartate is about 25 times faster than inactivation by glutamate or γ‐aminobutyric acid (GABA). Inactivation is accompanied by a rapid conversion of holoenzyme to apoenzyme and is opposed by pyridoxal‐P, suggesting that inactivation results from an alternative transamination of aspartate catalyzed by the enzyme, as previously observed with glutamate and GABA. Consistent with this mechanism pyridoxamine 5′‐phosphate, an expected transamination product, was formed when the enzyme was incubated with aspartate and pyridoxal‐P. The rate of transamination relative to the rate of decarboxylation was much greater for aspartate than for glutamate. Apoenzyme formed by transamination of aspartate was reactivated with pyridoxal‐P. In view of the high rate of inactivation, aspartate may affect

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb13128.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY