摘要:

Abstract—Kittens deprived of pattern vision until the 28th day of life received monocular visual experience for 3, 6, 14, and 75 h. Biphasic response of serotonin was found in the visual cortex. Stimulation for 3 h resulted in an increase of serotonin level whereas at 14 h it produced a decrease. The effects are transient, no longer observable after 75 h stimulation. No changes were observed in somatosensory corte

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04656.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Acetylcholine synthesis in homogenates of human intercostal muscle was measured by a radiochemical method. Choline acetyltransferase activity in control muscle was about 20 nmol.g−1.h−1. The enzyme was found only in the endplate area of the muscle. At high substrate concentrations its activity was overshadowed by the acetylcholine synthesizing activity of a different enzyme not saturated by 10 mm‐choline. The nonspecific enzyme was present at and away from the endplate area. Choline acetyltransferase in parasternal samples of intercostal muscle from myasthenia gravis patients was about 2.5 times higher than in samples, taken from a more lateral location, of control patients, but theKmfor choline was not altered (0.24 mm). It is suggested that in myasthenia gravis the shortage of acetylcholine receptors is partially compensated for by increased synthesis, storage, and release of the tran

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04657.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Over the 20‐min period following exposure of young chicks to a flashing light as an imprinting stimulus there is an increased incorporation of [14C]leucine into an acidic (tubulin‐enriched) protein fraction of the anterior dorsal forebrain in birds which have learnt the characteristics of the stimulus as compared with, either birds which have been exposed to an imprinting stimulus but learn poorly, or chicks kept in the dark. This brain region has been implicated in several studies as the locus for a number of biochemical modulations that accompany learning. The amount of [14C]leucine incorporated does not seem to be determined by precursor pool availability; it does, however, correlate with a well‐validated measure of the extent to which birds have learnt to recognise the characteristics of the stimulus, as shown by a two‐choice discrimination test. There is no change in the total content of tubulin dimer as assayed by colchicine binding under these conditions. Additionally, in birds which show evidence of learning, the binding of quinuclidinyl benzilate, an irreversible muscarinic ligand, is altered in both the posterior dorsal forebrain and midbrain regions. None of these effects could be simply the result of visual stimulation. The meaning of these changes is

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04658.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Regulation of muscarinic acetylcholine receptor concentration by receptor activity in neuron‐like NG108‐15 hybrid cells is a highly specific process. Receptor levels, monitored by binding of [3H]quinuclidinyl benzilate ([3H]QNB), decreased 50‐75% following 24‐h incubation of cells with muscarinic agonists, but none of the following cellular processes was altered by this chronic receptor stimulation: (1) glycolytic energy metabolism, measured by [3H]deoxy‐d‐glucose ([3H]DG) uptake and retention; (2) rate of cell division; (3) transport, measured by [3H]valine and [3H]uridine uptake; (4) RNA biosynthesis, measured by [3H]uridine incorporation; (5) protein biosynthesis, measured by [3H]valine and [35S]methionine incorporation into total protein and into protein fractions obtained by polyacrylamide gel electrophoresis. In contrast, chronic stimulation did cause a threefold decrease in the capacity of carbachol to stimulate phosphatidylinositol (PI) turnover, a receptor‐mediated response. In addition to cholinomimetics, the neuroeffector adenosine (1 mmfor 24 h) also caused a decrease in [3H]QNB binding levels, but chronic stimulation ofα‐adrenergic, opiate, prostaglandin E1, and prostaglandin F2αreceptors found on NG108‐15 cells caused no changes. The data indicate that loss of muscarinic receptors caused by receptor stimulation is not a consequence of fundamental changes evoked in overall cellular physiology but reflects a specific regulation of cholinoceptiv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04659.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Circadian variations in the activity of tyrosine hydroxylase, tyrosine aminotransferase, and tryptophan hydroxylase were observed in the rat brain stem. Tyrosine hydroxylase exhibited a bimodal pattern with peaks occurring during both the light and dark phases of the circadian cycle. Tyrosine aminotransferase had one daily peak of activity occurring late in the light phase, whereas tryptophan hydroxylase activity was maximal late in the dark phase. Circadian fluctuations in tyrosine hydroxylase activity did not correlate well with circadian variations in the turnover rates of norepinephrine or dopamine nor with levels of these catecholamines. This supports the idea that although tyrosine hydroxylase is the rate‐limiting enzyme in the synthesis of catecholamines, other factors must also be involved in thein vivoregulation of this process. Administration ofα‐methyl‐p‐tyrosine (AMT) methyl ester HC1 (100 mg/kg) had no effect on the activity of tryptophan hydroxylase, but effectively eliminated the peak of tyrosine hydroxylase activity that occurred during the light phase. AMT also lowered levels of tyrosine aminotransferase, but only at times near the daily light to dark transition. These chronotypic effects of AMT emphasize the importance of “time of day” as a factor that must be taken into account in evaluating the biochemical as well as the pharmacological and toxicological ef

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04660.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Incubation of P2fractions from rat cerebral cortex with32Piin the presence ofl‐glutamate caused an increased phosphorylation of a protein with apparent molecular weight of 43,000 (P43) as demonstrated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and autoradiography. This glutamate‐stimulated phosphorylation of P43was already detectable 10 s after the addition of glutamate and was dependent on the concentration of glutamate in the incubation medium. Other excitatory amino acids such as D‐glutamate,l‐aspartate,d,l‐cysteic acid,l‐cysteinesulfinic acid, andd,l‐α‐aminoadipic acid did not stimulate the phosphorylation of P43. In contrast,α‐ketoglutarate and succinate stimulated the phosphorylation of this protein. Glutamate‐stimulated phosphorylation of P43seemed not to be mediated by either cAMP or cGMP and was inhibited by the presence of Ca2+in the incubation medium. Experiments performed with metabolic inhibitors indicated that glutamate‐stimulated protein phosphorylation is localized in mitochondria. This conclusion is supported by the occurrence of glutamate‐stimulated phosphorylation of P43in mitochondrial fractions from several peripheral tissues. The present results are consistent with the hypothesis that P43is a component of the pyruvate dehydr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04661.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—A study was made to test the influence of rapid variations in glutamic acid decarboxylase (GAD) activity on the susceptibility of rats to hyperbaric oxygen (HBO). GAD was inhibited by the convulsant drug unsymmetrical dimethylhydrazine (UDMH) and reactivated by pyridoxine (PYR) after onset of convulsive activity. There was a relatively long induction period after UDMH injection until the onset of convulsions and the predictable interictal periods between successive periodic convulsions made it possible to study the impact of variations in GAD activity on survival rates, suspectibility to HBO and brain glycogen levels in a time sequence after UDMH administration. The experiments showed that UDMH interferes with aerobic metabolism in brain in such a way that profound alterations in resistance to acute oxygen poisoning resulted. An accumulation of substrate proximal to the enzyme block is assumed to develop during UDMH poisoning. The protective effect against HBO toxicity that was achieved after reactivation of GAD by PYR injection, as well as the rapid re‐establishment of glycogen levels, is believed to speak in favour of this hypothe

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04662.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The specific binding of [3H]spiperone and [3H]domperidone, as defined by 1 μm‐(+)butaclamol, was compared in homogenates of bovine retina and caudate nucleus. Scatchard analyses of saturation data for [3H]spiperone binding yielded dissociation constants (Kd) of 0.35 nmin the retina and 0.64 nmin the caudate nucleus. Comparison of the maximum number of binding sites (Bmax) present in each tissue indicated that the density of sites in bovine caudate nucleus (270 fmol/mg protein) was approximately three times higher than in bovine retina (92 fmol/mg protein). This difference was even more marked in guinea pig tissues, with a ratio of 7:1 between corpus striatum and retina. The pharmacological analysis of [3H]spiperone binding in both the bovine retina and caudate nucleus indicated an interaction with dopaminergic rather than serotonergic sites. However, inhibition curves obtained to dopaminergic agonists in the bovine retina were significantly steeper than those observed in the bovine caudate nucleus, as reflected in the greater Hill coefficients obtained for these agents in the retina. Furthermore, only a small amount of specific [3H]domperidone binding was observed in either the bovine caudate nucleus or the guinea pig striatum, whilst no specific [3H]domperidone binding was detectable in homogenates of either bovine or guinea pig retina. These data suggest that the retina possesses only a small population of dopaminergic D2 sites and that these binding sites may differ from those present in the caudate nuc

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04663.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—[3H]Spiperone binding has been used to study neurotransmitter receptors in bovine caudate nucleus in displacement and saturation binding experiments. Displacement curves for several antagonists are biphasic and can be analysed into contributions from dopaminergic and serotonergic sites. Antagonist binding at each class of sites follows the simple mass action equations for binding at a homogeneous set of sites (slope factors close to unity). Agonist displacement curves also indicate complex behaviour, but agonist binding to the dopaminergic sites alone exhibits heterogeneous properties (slope factors less than unity). Saturation binding experiments have been conducted on each class of site, defining dopaminergic binding of [3H]spiperone as that binding displaced by 0.1 mm‐dopamine and serotonergic binding as that displaced by 0.3 μm‐mianserin. In each case, a single class of binding sites was detected: the binding parameters derived in this way have been used to calculate the proportions of the two classes of binding site observed in displacement experiments. Good agreement was obtained between calculated and observed

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04664.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—A synaptosome‐enriched fraction from sheep cortex was incubated withl‐fucose. The uptake of the sugar into this preparation was dependent on time, temperature, and concentration. A AKmappof 0.94 mm‐l‐fucose and aVmaxappvalue of 0.24 nm‐l‐fucose/mg synaptosomal soluble protein/20 min was determined. After incubation for 10 min at 25°C withl‐[3H]fucose, 70% of the radioactive label was found in the soluble fraction. DEAE‐cellulose chromatography resulted in the elution of three fucosylprotein peaks which were then characterised by gel filtration and sodium dodecyl sulfate‐polyacrylamide electrophoresis (SDS‐PAGE). At least eleven3H protein‐staining bands were identified with M. W. 13,000‐115,000. Control experiments involving the incubation of the hexose with heat‐treated synaptosomes and myelin, mitochondria, and microsomes indicated that the tritiated material associated with the synaptosomal soluble fraction was not due to nonspecific binding or to the presence of contaminating subcellular material. A3H glycopeptide was identified, and on analysis the carbohydrate moiety was found to be rich in sialic acid, fucose, galactose, mannose, andN‐acetylglucosamine. Mild acid treatment of the glycopeptide released fucose, which implies that this carbohydrate occupies a terminal position in the oligosaccharide chain. From these results it is proposed that synthesis or the modification of soluble fucosylglycoprotei

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1981.tb04665.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY