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P Lähdesmäki

Publications and source records attributed to P Lähdesmäki.

12 recordsLinked to original sources
PubMed1979

Ability of calf brain synaptic membranes to bind [35S]taurine to their triton X-100 and chloroform extracts.

A protein fraction containing reducing sugars was prepared from calf brain synaptic membranes with 0.5% Triton X-100, and another fraction containing bound phosphorus with a 2 : 1 chloroform--methanol mixture. Both protein fractions bound small amounts of [35S]taurine, the first fraction about 25 pmol/g protein and the second about 220 pmol/g protein. The Triton X-100 extract represented 13.8% of the membrane proteins, but the chloroform--methanol extract only 0.9%. The binding of taurine to the Trition X-100 extract was temperature sensitive, but was only slightly inhibited by hypotaurine and beta-alanine.

Alanine↗
PubMed1979

Synaptosomal accumulation of intracerebrally injected amino acids.

The distribution of the labels of [35S]taurine, [3H]lysine, [14C]glutamate and [14C]norleucine in mouse brain subcellular fractions was followed after intracerebral injection in vivo. [35S]taurine, [3H]lysine and [14C]glutamate and its metabolites accumulated in the nerve terminals, lysine and glutamate also occurring in the synaptic vesicles, while remained mainly in soluble synaptoplasm [14C] nor leucine penetrated the brain cell membranes slowly, but was still bound to the synaptic vesicles to a greater extent than taurine.

Amino Acids↗
PubMed1977

Effect of aromatic acids on the influx of aromatic amino acids in rat brain slices.

The influx of [3H]phenylalanine, [3H]tyrosine and [3H]tryptophan into brain cells was studied using brain slices from adult rats. Each aromatic amino acid inhibited the influx of the others into the brain cells. Tryptophan inhibited non-competitively the influx of phenylalanine, and phenylalanine similarly that of tyrosine and tryptophan. On the other hand, tyrosine inhibited competitively the influx of phenylalanine, and similarly tryptophan that of tyrosine, and tyrosine that of tryptophan. Among the aromatic organic acids tested, only phenylpyruvate and homogentisate had any inhibitory effect on the influx of the aromatic amino acids. These effects were generally competitive, non-competitive inhibition being obtained only in the inhibition of phenylalanine influx by homogentisate. The existence of only one common transport system for aromatic amino acids appear to be unlikely.

Animals↗
PubMed1977

Amino acids in the synaptic vesicle fraction from calf brain: content, uptake and metabolism.

A synaptic vesicle fraction was prepared from calf brain cortex, containing 10 identified amino acids and two unidentified ninhydrin-positive compounds, one of which is apparently a peptide. The most plentiful amino acids were taurine (1.8 nmol/g original tissue), glutamic acid (1.8), serine (0.9), aspartic acid (0.8) and GABA (0.8); the others identified were cysteic acid (or cysteinesulphinic acid), glutamine, alanine, glycine and lysine. The unknown peptide occurred in a high concentration (about 16 alanine equivalents/g), and contained mainly aspartic acid and serine. Cysteic acid (or cysteinesulphinic acid) also occurred in relatively high amounts, but its peak contained acid-labile impurities. The influx of [14C]glutamate into the vesicles took place by means of non-saturable migration, while two saturable systems having very similar properties were dominant only at low glutamate concentrations. Influx constants for these quantitatively low uptake systems were Km, 34 and 92 micrometer, and Vmax, 33 and 49 nmol/min/g obtained by v versus v/S plot. Almost the same values were also obtained by a 1/v versus 1/S plot. GAD and GABA-T activities in the vesicles were only 1/200th of those in the synaptosomes.

4-Aminobutyrate Transaminase↗
PubMed1977

Extramitochondrial protein synthesis in calf brain synaptosomes.

Isolated synaptosomes of calf brain cortex incorporated labelled amino acids into their mitochondrial, membranous and soluble proteins in an approximate ratio of 1:1:0.5 Synaptosomal protein synthesis was sensitive to ATP, noradrenaline, cycloheximide and puromycin, and together with mitochondrial protein synthesis, also to chloramphenicol, 2.4-dinitrophenol, KCN and hyperosmotic conditions. The absence of Na+ and K+ ions slightly inhibited both synaptosomal and mitochondrial protein synthesis. Using incorporated radioactivity as an indicator of synthesized proteins, the synaptosomal soluble proteins could be obtained in one large peak in gel and indicator of synthesized protein, the synaptosomal soluble proteins could be obtained in one large peak in gel filtration on Sephadex G-100 and G-25, and in two components in disc electrophoresis on a 7% polyacrylamide gel. An approximate molecular weight was calculated for the synthesized proteins using known proteins as standards, giving 15000-35000 in the gel filtration eluant, and 27000 and 36000 in the disc electrophoresis bands.

Adenosine Triphosphate↗
PubMed1977

A peptide containing aspartic acid, glutamic acid and serine in calf brain synaptic vesicles.

Free amino acids and other amino compounds in calf brain synaptic vesicles were identified and determined by thin-layer chromatography and ion-exchange chromatography. The vesicles contained ten identified amino acids with glutamic acid, aspartic acid, taurine and gamma-aminobutyric acid in the highest concentrations, and also cysteic acid (or cysteinesulfinic acid), glutamine, alanine, serine, glycine and lysine. The vesicles also contained certain unknown acid-labile, ninhydrin-positive compounds, one of which was a peptide yielding, after acid hydrolysis, about 40% aspartic acid, 30% serine, 15% glutamic acid, 10% glycine and possibly some alanine and lysine. The concentration of the peptide in the vesicles was as high as that of all the other amino compounds together.

Amino Acids↗