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Brain Research Dec 1981A method for the rapid (1-1.5 h) preparation of nerve ending particles (synaptosomes) from rat cerebral cortex is described. The synaptosome fraction has been...
A method for the rapid (1-1.5 h) preparation of nerve ending particles (synaptosomes) from rat cerebral cortex is described. The synaptosome fraction has been characterized by quantitative electron microscopy and enzyme distribution studies. By these criteria, the fraction showed a degree of enrichment in synaptic structures which was comparable to that of the standard (4-5 h) preparation, and substantially better than an alternative fast (2-2.5 h) method. On incubation, synaptosomes obtained by the new procedure accumulated a high tissue concentration of potassium and showed a high, linear rate of oxygen uptake. Depolarization by veratrine caused a significant increase in the rate of respiration and in the release of the physiologically active amino acids; glutamate, aspartate and GABA, as well as a significant reduction in tissue potassium. Thus, the new procedure compared favourably with alternative methods as judged by these indices of metabolic and functional performance. The new preparation method has been found to be of value in metabolic studies of synaptosomes prepared from human post-mortem brain.
Topics: Amino Acids; Animals; Cell Fractionation; Cerebral Cortex; Enzymes; Female; Male; Microscopy, Electron; Oxygen Consumption; Rats; Rats, Inbred Strains; Synaptosomes
PubMed: 7296283
DOI: 10.1016/0006-8993(81)91086-6 -
Journal of Neurochemistry Oct 1986Sialyltransferase has been characterized in P2 pellets derived from animals of increasing age. The enzyme was found to be associated with the plasma membrane and to be... (Comparative Study)
Comparative Study
Sialyltransferase has been characterized in P2 pellets derived from animals of increasing age. The enzyme was found to be associated with the plasma membrane and to be developmentally regulated at times coincident with cell migration and fibre outgrowth. This regulation appeared to be due, in part, to an endogenous competitive inhibitor in the P2 pellet but not in the synaptosome. Optimal transfer of [14C]N-acetylneuraminic acid to endogenous synaptosomal acceptors was achieved only in the absence of detergent. Furthermore, the transferred sialic acid was found to be inaccessible to the action of membrane-bound sialidase. The significance of these findings is discussed.
Topics: Aging; Animals; Brain; Cell Membrane; Glycoproteins; Membrane Proteins; N-Acetylneuraminic Acid; Rats; Rats, Inbred Strains; Sialic Acids; Sialyltransferases; Synaptosomes; Transferases; beta-D-Galactoside alpha 2-6-Sialyltransferase
PubMed: 3746299
DOI: 10.1111/j.1471-4159.1986.tb00737.x -
Neuroscience Letters Mar 1982Diazepam (3 nM-3 microM) enhanced GABA binding to well-washed synaptosomal membranes in a concentration-dependent manner. Half maximal enhancement occurred at 20 nM... (Comparative Study)
Comparative Study
Diazepam (3 nM-3 microM) enhanced GABA binding to well-washed synaptosomal membranes in a concentration-dependent manner. Half maximal enhancement occurred at 20 nM diazepam. Kinetic analysis by non-linear Scatchard analysis revealed that the primary action of diazepam was to increase the affinity of GABA binding to a low affinity site. These results support electrophysiological and other biochemical observations of benzodiazepine-GABA interactions.
Topics: Animals; Binding Sites; Brain; Cell Membrane; Diazepam; Kinetics; Rats; Synaptosomes; gamma-Aminobutyric Acid
PubMed: 7070714
DOI: 10.1016/0304-3940(82)90365-2 -
Journal of Neurochemistry Jun 1975
Topics: Alanine; Aminobutyrates; Animals; Binding, Competitive; Biological Transport, Active; Brain; Calcium; Hydroxybutyrates; Kinetics; Osmolar Concentration; Ouabain; Potassium Chloride; Rats; Receptors, Drug; Sodium; Sucrose; Synaptosomes; gamma-Aminobutyric Acid
PubMed: 1127436
DOI: 10.1111/j.1471-4159.1975.tb03905.x -
Research Communications in Chemical... Nov 1972
Topics: Chemical Phenomena; Chemistry, Physical; Depression, Chemical; Dopamine; Dopamine Antagonists; Electrons; Models, Theoretical; Nerve Endings; Pheniramine; Quantum Theory; Synaptic Vesicles; Synaptosomes
PubMed: 4638600
DOI: No ID Found -
Bollettino Della Societa Italiana Di... May 1984
Topics: Animals; Aspartic Acid; Goldfish; Hippocampus; Kainic Acid; Kinetics; Mitochondria; Neurotransmitter Agents; Potassium; Pyrrolidines; Rats; Synaptosomes; gamma-Aminobutyric Acid
PubMed: 6147150
DOI: No ID Found -
Journal of Inorganic Biochemistry Jun 2004Glutamine (Gln), glutamate (Glu) and gamma-amino butyric acid (GABA) are essential amino acids for brain metabolism and function. Astrocytic-derived glutamine is the...
Glutamine (Gln), glutamate (Glu) and gamma-amino butyric acid (GABA) are essential amino acids for brain metabolism and function. Astrocytic-derived glutamine is the precursor of the two most important neurotransmitters: glutamate, an excitatory neurotransmitter, and GABA, an inhibitory neurotransmitter. In addition to their roles in neurotransmission these neurotransmitters act as alternative metabolic substrates that enable metabolic coupling between astrocytes and neurons. The relationships between Gln, Glu and GABA were studied under lead (Pb) toxicity conditions using synaptosomal fractions obtained from adult rat brains to investigate the cause of Pb neurotoxicity-induced seizures. We have found that diminished transport of [(14)C]GABA occurs after Pb treatment. Both uptake and depolarization-evoked release decrease by 40% and 30%, respectively, relative to controls. Lower expression of glutamate decarboxylase (GAD), the GABA synthesizing enzyme, is also observed. In contrast to impaired synaptosomal GABA function, the GABA transporter GAT-1 protein is overexpressed (possibly as a compensative mechanism). Furthermore, similar decreases in synaptosomal uptake of radioactive glutamine and glutamate are observed. However, the K(+)-evoked release of Glu increases by 20% over control values and the quantity of neuronal EAAC1 transporter for glutamate reaches remarkably higher levels after Pb treatment. In addition, Pb induces decreased activity of phosphate-activated glutaminase (PAG), which plays a role in glutamate metabolism. Most noteworthy is that the overexpression and reversed action of the EAAC1 transporter may be the cause of the elevated extracellular glutamate levels. In addition to the impairment of synaptosomal processes of glutamatergic and GABAergic transport, the results indicate perturbed relationships between Gln, Glu and GABA that may be the cause of altered neuronal-astrocytic interactions under conditions of Pb neurotoxicity.
Topics: Animals; Brain; Brain Chemistry; Glutamic Acid; Glutamine; Lead; Male; Rats; Rats, Wistar; Seizures; Signal Transduction; Synaptosomes; gamma-Aminobutyric Acid
PubMed: 15149801
DOI: 10.1016/j.jinorgbio.2004.02.010 -
The Journal of Pharmacology and... May 1987Effects of the organochlorine insecticides chlordecone, mirex, 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane and...
Effects of the organochlorine insecticides chlordecone, mirex, 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane and 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane on free intrasynaptosomal Ca2+ [( Ca++]i), synaptosomal 45Ca uptake and synaptosomal plasma and mitochondrial membrane potentials in vitro were studied. Chlordecone (10-50 microM) increased [Ca++]i from the resting level of 370 nM in a dose- and time-dependent manner to above 1.5 microM. This took place in the presence of 1 mM extrasynaptosomal Ca++ but not in nominally Ca++-free medium. Verapamil, a voltage sensitive Ca++ channel blocker, inhibited the initial increase of [Ca++]i caused by chlordecone, by 40%. Chlordecone also elevated [Ca++]i in synaptosomes in which mitochondrial Ca++ uptake had been abolished by valinomycin. Chlordecone depolarized partially the synaptosomal plasma membrane and, to a lesser extent, the potential of mitochondria within synaptosomes. However, chlordecone appeared to inhibit synaptosomal K+-stimulated and unstimulated 45Ca++ uptake by 20 to 30%. Inasmuch as chlordecone also stimulated release of 45Ca++ and the fluorescent dye fura-2 from preloaded synaptosomes, the apparent inhibition of uptake might be due to lysis of some synaptosomes by chlordecone. The effect of chlordecone on [Ca++]i decreased when the total amount of tissue in incubations was increased. [Ca++]i was only elevated marginally by mirex at the same concentration range. The results suggest that chlordecone increases free intrasynaptosomal Ca++ mainly by increasing influx of extrasynaptosomal Ca++. The principal mechanism appears to be a nonspecific leakage of Ca++ through the plasma membrane but some Ca++ may pass through voltage-sensitive Ca++ channels due to chlordecone-induced membrane depolarization.
Topics: Animals; Calcium; Chlordecone; DDT; Insecticides; Isomerism; Male; Mathematics; Mirex; Rats; Rats, Inbred F344; Synaptosomes; Valinomycin; Verapamil
PubMed: 2437290
DOI: No ID Found -
Journal of Lipid Research Nov 1973Subcellular fractionation of human brain cortex obtained at autopsy yielded microsomal and synaptosome-rich fractions from the gray matter and microsomal and purified...
Subcellular fractionation of human brain cortex obtained at autopsy yielded microsomal and synaptosome-rich fractions from the gray matter and microsomal and purified myelin fractions from the white matter. The phospholipids of myelin were high in plasmalogens, and the molar ratio of alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 4. The acyl groups of the myelin phosphoglycerides were enriched in monoenes (mainly 18:1 and 20:1) and a tetraene, 22:4(n - 6). The phospholipids in the synaptosome-rich fraction were high in diacyl sn-glycero-3-phosphorylcholine, and the molar ratio of the alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 0.88. The acyl groups of synaptosomal ethanolamine phosphoglycerides were rich in 22:6(n - 3) but contained a very low amount of 20:1. The lipid composition of microsomes from the gray matter was different from that of microsomes from the white matter but was nearly identical with that of the synaptosome-rich fraction. Except for a slightly lower proportion of alkenyl acyl sn-glycero-3-phosphorylethanolamine and sphingomyelin, the lipid composition of microsomes from the white matter was also similar to that of the myelin. There were also species-related differences between the brain lipid composition of human and subhuman primates and that of the rodents. Furthermore, the brain lipid composition in normal human subjects is rather constant and does not seem to be affected much by individual variations.
Topics: Aged; Brain Chemistry; Cell Membrane; Cerebral Cortex; Ethanolamines; Humans; Microscopy, Electron; Microsomes; Middle Aged; Myelin Sheath; Phospholipids; Sphingomyelins; Subcellular Fractions; Synaptosomes
PubMed: 4742559
DOI: No ID Found -
[Influence of microwave radiation on synaptic structure and function of hippocampus in Wistar rats].Zhonghua Lao Dong Wei Sheng Zhi Ye Bing... Apr 2007To investigate the effect of microwave radiation on synaptic structure, characteristic of synaptosome, the contents and release of neurotransmitters in hippocampus in...
OBJECTIVE
To investigate the effect of microwave radiation on synaptic structure, characteristic of synaptosome, the contents and release of neurotransmitters in hippocampus in Wistar rats.
METHODS
Wistar rats were exposed to microwave radiation with average power density of 30 mW/cm(2). Electron telescope was used to study the change of the synaptic structure at 6 h after radiation and to identify synaptosome. Flow cytometry and electron spin resonance were used to study the change of the concentration of Ca(2+) in synapse and the fluidity of membrane proteins of synaptosome. High performance liquid chromatography (HPLC) and spectrophotometer were used to study the changes of contents and release of amino acids and acetylcholine in hippocampus.
RESULTS
Microwave radiation of 30 mW/cm(2) caused deposits of synapse vesicle, elongation of active zone, the increase of thickness of postsynaptic density (PSD) and curvature, and perforation of synapse. The concentration of Ca(2+) in synapse (P<0.01) and tc of membrane proteins (P<0.01) of synaptosome increased contents of glutamic acid and glycine (P<0.01) and release of GABA increased the increase of contents and release of acetylcholine, and activity of acetyl cholinesterase (P<0.01) increased.
CONCLUSION
Microwave radiation can induce the injure of synaptic structure and function of hippocampus, and then induce the disorder of the ability of learning and memory in rats.
Topics: Animals; Hippocampus; Male; Microwaves; Rats; Rats, Wistar; Synapses; Synaptosomes
PubMed: 17535652
DOI: No ID Found