ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04401.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04402.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Résumé—Des séparations sur gel de polyacrylamide ont permis d'établir la distribution électrophorétique des protéines, de l'incorporation d'acides aminés et de l'acétylcholinestérase (AChE; EC 3.1.1.7) du ganglion sympathique au repos et stimulé. Une étude conjointe d'histochimie ultrastructurale a montré que l'essentiel de l'activité acétylcholinestérasique des neurones sympathiques et des nerfs préganglionnaires est localisée dans le réticulum endoplasmique. Les molécules d'AChE du ganglion ont une faible mobilitéélectrophorétique, elles se répartissent en 3 bandes: une majeure et deux mineures. Le profil de radioactivité obtenu après marquage par lal‐[U‐14C]leucine se caractérise par la présence de 3 pics importants qui sont situés au début, au milieu et à la fin de l'électrophorégramme. Les bandes de protéines et le pic de radioactivité migrant dans le début du gel ainsi que la bande majeure d'AChE ne sont extraites qu'en présence de Triton X‐100. La zone de radioactivité contenant l'activité acétylcholinestérasique perd plus de 50% de sa radioactivité après 5 à 8 h de chasse du précurseur. La stimulation préganglionnaire à 16/s appliquée durant 1 à 4h abaisse d'environ 50% l'incorporation de lal‐[U‐14C]leucine dans les protéines migrant au début et à la fin de l'électrophorégramme. La radioactivité associée à l

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04403.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Myelin preparations from the whole brains of 16‐day‐old rats and from cortical regions and brainstem, respectively, of 40‐day‐old rats were separated into light, medium and heavy subfractions on a discontinuous sucrose gradient by a procedure previously used for whole adult rat brain (Matthieu,et al., 1973). The total dry weight of myelin recovered from the 16‐day‐old rats was only 2·4mg/g fresh brain in comparison to 20 mg from adult brains. In 16‐day‐old rat brains, the percentage of the total myelin protein in the light fraction was higher than that found in adult brains; the percentage in the medium fraction was only one‐third that in adults; while the percentage in the heavy fraction was about the same at both ages. The heavy fraction from the 16‐day‐old rats contained less basic protein and proteolipid than the light fraction, and the levels of the 2′3′‐cyclic nucleotide 3′‐phosphohydrolase (CNP) and glycoprotein were less than half those in the light and medium fractions. Double labelling experiments with radioactive fucose indicated that the major labelled glycoprotein in the heavy and medium fractions had a slightly higher apparent mol. wt than that in the light fraction. Electron microscopy showed much readily identifiable, compact myelin in the light and medium fractions from the 16‐day‐old rats, whereas the heavy fraction contained more single membranous structures and much less multilamellar myelin. The yield of myelin/g fresh wt from brainstem of 40‐day‐old rats was 4‐fold higher than from cortical regions, and the percentage recovered in the light fraction was greater in the brainstem. In both regions basic proteins decreased from the light to the heavy fraction, whereas high mol. wt proteins, the glycoprotein and CNP increased. The biochemical and morphological results suggest that in both 16‐day‐old and young adult rats the light fraction is enriched multilamellar, compact myelin. In contrast, the heavy fraction at both ages is enriched in loose, uncompacted myelin and myelin‐related membranes, although the heavy fraction from 16‐day‐old rats also may be substantially con

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04404.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—A reproducible model of subacute methyl mercury (MeHg) intoxication was developed in the adult rat following the daily intragastric administration of 10 mg methyl mercury/kg body wt. Synaptosomes isolated from animals during the latent phase of mercury neurotoxicity (6‐10 days) demonstrated no significant change in respiratory control, State 3, State 4, or 2,4‐dinitrophenol stimulated respiration with succinate, glutamate or pyruvate plus malate. During the neurotoxic phase, a significant decline in respiratory control was evident with all substrates. Cerebellar synaptosomes revealed qualitatively similar but quantitatively greater inhibition of 2,4‐dinitrophenol stimulated respiration during the latent and neurotoxic phases with glutamate.In vitrostudies of synaptosome respiration, oxidative phosphorylation and respiratory control with 5‐15 μm‐methyl mercury revealed a stimulation of initial State 4 respiration, loss of RCI, inhibition of State 3 but no change in the gramicidin or 2,4‐dinitrophenol uncoupled rate supported by pyruvate‐malate. Phosphate did not relieve the State 3 inhibition. At 25 μm‐methyl mercury and above, considerable inhibition of electron transfer occurred. At this concentration, cytochromecoxidase was inhibited 50%. Isosmotic replacement of medium KC1 by mannitol reduced the MeHg stimulation of State 4 respiration but had no effect on MeHg inhibition of ADP stimulated respiration. Half‐maximal stimulation of State 4 respiration by MeHg occurred at [K]+⋍ 6 mm. These findings are compatible with an energy‐linked methyl mercury induced cation translocation across the synaptosome

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04405.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Data comparing tricarboxylic acid cycle dynamics in mitochondria from rabbit brain using [2‐ or 3‐14C]pyruvate with and without cosubstrates (malate, α‐ketoglutarate, glutamate) are reported. With a physiological concentration of an unlabelled cosubstrate, from 90‐99% of the isotope remained in cycle intermediates. However, the liberation of14CO2and the presence of14C in the C‐1 position of α‐ketoglutarate indicated that multiple turns of the cycle occurred. Entry of pyruvate into the cycle was greater with malate than with either α‐ketoglutarate or glutamate as cosubstrate. With malate as cosubstrate for [14C]pyruvate the amount of [14C]citrate which accumulated averaged 30nmol/ml or 23% of the pyruvate utilized while α‐ketoglutarate averaged 45 nmol/ml or 35% of the pyruvate utilized. With α‐ketoglutarate as cosubstrate for [14C]pyruvate, the average amount of [14C]citrate which accumulated decreased to 8 nmol/ml or 10% of the pyruvate utilized while [14C]α‐ketoglutarate increased slightly to 52 nmol/ml or an increase to 62%, largely due to a decrease in pyruvate utilization. The percentage of14C found in α‐ketoglutarate was always greater than that found in malate, irrespective of whether α‐ketoglutarate or malate was the cosubstrate for either [2‐ or 3‐14C]pyruvate. The fraction of14CO2produced was slightly greater with α‐ketoglutarate as cosubstrate than with malate. This observation and the fact that malate had a higher specific activity than did α‐ketoglutarate when α‐ketoglutarate was the cosubstrate, indicated a preferential utilization of α‐ketoglutarate formed within the mitochondria.Whenl‐glutamate was a cosubstrate for [14C]pyruvate the principal radioactive product was glutamate, formed by isotopic exchange of glutamate with [14C] α‐ketoglutarate. If malate was also added, [14C]citrate accumulated although pyruvate entry did not increase. Due to retention of isotope in glutamate, little [14C]succinate, malate or aspartate accumulated. When [U‐14C]l‐glutamate was used in conjunction with unlabelled pyruvate more14C entered the cycle than when unlabelled glutamate was used with [14C]pyruvate and led to α‐ketoglutarate, succinate and aspartate as the major isotopic products. When in addition, unlabelled malate was added, total and isotopic α‐ketoglutarate increased while [14C]aspartate decreased. The increase in [14C]succinate when [14C] glutamate was used indicated an increase in the flux through α‐ketoglutarate dehydrogenase and was accompanied by a decrease of pyruvate utilization as compared to experiments when either α‐ketoglutarate or glutamate were present at low concentration.It is concluded that the tricarboxylic acid cycle in brain mitochondria operates in at least three open segments, (1) pyruvate plus malate (oxaloacetate) to citrate; (2) citrate to α‐ketoglutarate and; (3) α‐ketoglutarate to malate, and that at any given time, the relative rates of these segments depend upon the substrate composition of the environment of the mitochondria. These data suggest an approach to a steady state consistent with th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04406.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Subcellular fractions from brains of 5, 10, 13, 16, 21, 30 day‐old and adult rats were prepared. Protein content and various enzyme activities were assayed in all fractions and brain homogenates. γ‐Glutamyl transpeptidase activity and 5′‐nucleotidase were very low at 5 days of life but steadily increased, reaching adult concentrations at about 30 days after birth. Alkaline phosphatase, instead slowly decreased with maturation, while monoamine oxidase after an initial decrease, increased rapidly to adult levels.The relation between the appearance of enzymatic activity in brain and the blood‐brain barrier function

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04407.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—A comparison was made of the manner in which choline chloride and 3,3‐dimethyl‐1‐butanol react with the acetylenzyme formed during the hydrolysis of esters of acetic acid by acetylcholinesterase. Acetylcholine and acetylthiocholine were the substrates. The ratio of the formation of alkyl acetate to that of acetic acid increased linearly with the concentration of dimethylbutanol, but approached a limiting value as the concentration of choline was increased. Total enzymic activity was inhibited by choline and activated slightly by dimethylbutanol. The effects of varying ionic strength, pH and substrate concentration were examined. The effects of tetraethyl‐ and tetramethylammonium ions on the reaction of dimethylbutanol with the acetylenzyme were also studied. The results suggest that dimethylbutanol and choline bind to different regions of the active site. A mechanism for the reaction of choline and substrate with acetylcholinesterase is

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04408.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The distribution of choline acetyltransferase (ChAc, EC 2.3.1.6) andl‐glutamate 1‐carboxylyase (glutamate decarboxylase, GAD, EC 4.1.1.15) was studied in serial frontal slices of the substantia nigra (SN) (pars compacta, PC; pars reticulata, PR; an intermediate region, IR) as well as in other brain areas from post mortem tissue of control and Parkinsonian patients.Within the SN from control brain ChAc and GAD activities showed a distinctive distribution: ChAc activity in PC was higher than in PR and IR by 427% and 253% respectively and within PC the enzyme activity in the rostral part exceeded that in the control part by 353%. The GAD activity in PC was higher by 41% than that in PR and within PC seemed to be higher in the caudal than in the rostral part. For both enzyme activities there were no significant differences between PR and IR or within these regions.In Parkinsonian brain both ChAc and GAD activities were reduced to 15‐25% of controls in all 3 regions of the SN. The distinctive distribution of ChAc and GAD activity found in the SN of control brain was abolished: no difference was observed between the 3 regions. However, within PC the ChAc activity was lower in the medial than in the rostral part.Since nigral ChAc is possibly located in interneurons, the decrease in enzyme activity may be connected with the cell loss observed in the SN of Parkinsonian brain.By contrast, nigral GAD is probably contained in terminals of strio‐nigral neurons and the decrease in enzyme activity in Parkinson's disease in the absence of striatal cell loss, may reflect a change in the functional state of these GABA neurons.Among various areas of control brains ChAc activity was highest incaudate nucleusandputamenwhile GAD was highest in SN.caudate nucleus, putamenandcerebral cortex.In Parkinsonian brain the most severe reduction in ChAc and GAD activities was found

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04409.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—A variety of isoxazoles structurally related to muscimol (3‐hydroxy‐5‐aminomethylisoxazole) were tested as inhibitors of the uptake of GABA and some other amino acids in rat brain slices, and of the activity of the GABA‐metabolizing enzymesl‐glutamate 1‐carboxylyase and GABA:2‐oxo‐glutarate aminotransferase. A bicyclic derivative, 4,5,6,7‐tetrahydroisoxazolo[4,5‐c]pyridin‐3‐ol, proved to be a more potent inhibitor of GABA uptake than muscimol. Structure‐activity studies on this derivative, which appeared to be a competitive inhibitor of GABA uptake, led to the findings that nipecotic acid (piperidine‐3‐carboxylic acid) is a powerful non‐competitive inhibitor of GABA uptake, and that perhydro‐1,2‐oxazine‐6‐carboxylic acid is a relatively

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04410.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY