Library

Notes: Abstract: Myelin isolated from goldfish brain shows a multilamellar structure with a major dense line and two intraperiod lines. Sodium dodecyl sulfate gel electrophoresis revealed that the protein profile of goldfish brain myelin is distinctly different from that of rat brain myelin. No protein migrating to the position of proteolipid protein or DM-20 was seen in goldfish myelin. Goldfish acclimated to 5°, 15°, and 30°C showed no qualitative differences in myelin proteins. The 13.5 kD protein in goldfish brain myelin and brain homogenate was intensely immunostained with the antiserum to human basic protein by the immunoblot technique. In contrast, none of the proteins of goldfish myelin were immunostained with an-tiproteolipid protein serum; however, both proteolipid protein and DM-20 of rat brain myelin were immunostained. The significance of the synthesis of myelin proteins by astrocytes in the goldfish brain is discussed.

Notes: Abstract— A homogeneous preparation of proteolipid protein (PLP) from rat brain myelin was isolated by preparative gel electrophoresis in sodium dodecyl sulfate and chemically characterized. The results of amino acid and N-terminal amino acid analyses are reported. The same preparation of myelin PLP was used to produce specific precipitating antibodies. Rabbit and goat antisera to myelin PLP each gave a single precipitin line with purified PLP dissolved in Triton X-100. Under identical conditions, no precipitation was observed with antiserum to myelin basic protein or with control serum. Immunofluorescence localization employing antiserum to PLP demonstrated bright specific fluorescence restricted to the myelin sheaths of axons in all anatomical areas of the rat brain examined. Neuronal cell bodies and their dendrites were completely negative with respect to the presence of proteolipid protein. PLP could not be localized in the cell bodies or fibrous processes in any of the glial elements in the adult rat brain. However, myelin PLP was clearly visible in the cytoplasm and processes of actively myelinating oligodendrocytes in the corpus callosum in the brains of 10-day-old rats.

Notes: —We studied the incorporation of radioactivity into individual proteins of myelin by sodium dodecyl sulfate polyacrylamide gel electrophoresis after the injection of [3H]tryptophan into the right eye of developing rabbits. We found that the specific activity of basic protein (c.p.m./mg of basic protein) and the specific activity of DM-20 and proteolipid protein (c.p.m./mg total myelin protein applied to the gel) did not approach the ratio predicted by decussation of the fibres of the rabbit optic nerve. The specific activity of Wolfgram protein, however, approached an expected ratio of 15:1. We therefore concluded that myelin basic protein, DM-20 and proteolipid protein were probably not synthesized in retinal ganglion cells.

Notes: Abstract— —Glutamic acid, glutamine, GABA and aspartic acid exhibited postnatal increases in the developing mouse brain at the same time that the other amino acids, both essential and non-essential, of the pool decreased. The most significant decreases were observed in the concentrations of taurine, phosphoethanolamine, glycine and alanine. The period of rapid accumulation of the members of the glutamic acid family in the mouse brain was concurrent with dramatic increases and decreases in brain weight and water content, respectively.

Notes: Abstract— D-β-hydroxybutyrate (β-OHB) was compared to glucose as a precursor for brain amino acids during rat development. In the first study [3-14C]β-OHB or [2-14C]glucose was injected subcu-taneously (01 μCi/g body wt) into suckling rats shortly after birth and at 6. 11, 13, 15 and 21 days of age. Blood and brain tissue were obtained 20 min later after decapitation. The specific activity of the labelled precursor in the blood and in the brain tissue was essentially the same for each respective age suggesting that the labelled precursor had equilibrated between the blood and brain pools before decapitation. [3-14C]β-OHB rapidly labelled brain amino acids at all ages whereas [2-14C]glucose did not prior to 15 days of age. These observations are consistent with a maturational delay in the flux of metabolites through glycolysis and into the tricarboxylic acid cycle. Brain glutamate, glutamine, asparate and GABA were more heavily labelled by [3-14C]β-OHB from birth-15 days of age whereas brain alanine was more heavily labelled by [2-14C]glucose at all ages of development. The relative specific activity of brain glutamine/glutamate was less than one at all ages for both labelled precursors suggesting that β-OHB and glucose are entering the‘large’glutamate compartment throughout development. In a second study, 6 and 15 day old rats were decapitated at 5 min intervals after injection of the labelled precursors to evaluate the flux of the [14C]label into brain metabolites. At 6 days of age, most of the brain acid soluble radioactivity was recovered in the glucose fraction of the [2-,4C]glucose injected rats with 72, 74, 65 and 63% after 5, 10, 15 and 20 min. In contrast, the 6 day old rats injected with [3-14C]β-OHB accumulated much of the brain acid soluble radioactivity in the amino acid fraction with 22, 47, 57 and 54% after 5, 10, 15 and 20 min. At 15 days of age the transfer of the [14C]label from [2-14C]glucose into the brain amino acid fraction was more rapid with 29, 40, 45, 61 and 73% of the brain acid soluble radioactivity recovered in the amino acid fraction after 5, 10, 15, 20 and 30 min. There was almost quantitative transfer of [14C]label into the brain amino acids of the 15-day-old [3-14C]β-OHB injected rats with 66, 89, 89, 89 and 90% of the brain acid soluble radioactivity recovered in the amino acid fraction after 5, 10, 15, 20 and 30 min. The calculated half life for /?-OHB at 6 days was 19 8 min and at 15 days was 12-2 min. Surprisingly, the relative specific activity of brain GABA/glutamate was lower at 15 days of age in the [3-14C]β-OHB injected rats compared to the [2-14C]glucose injected rats despite a heavier labelling of brain glutamate in the [3-14C]β-OHB injected group. We interpreted these data to mean that β-OHB is a less effective precursor for the brain glutamate ‘subcompartment’ which is involved in the synthesis of GABA.

Notes: A new protein component has been demonstrated in myelin isolated from rat whole brain and from white matter dissected from bovine, dog and rabbit brain. It is also present in rabbit optic nerve. It does not appear to be present in other subcellular fractions of rat brain. It has a molecular weight of 20,540 ± 490(S.D.), as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. A rapid procedure for the isolation of myelin is also described.