Influence of neonatal hypothyroidism upon transcription in isolated rat brain and liver nuclei

RNA-polymerase, type I: activity in rat brain cell nuclei and peripheral blood mononuclear cells after Venezuelan equine encephalomyelitis virus infection

Rats inoculated intraperitoneally with 100 LD50 of Venezuelan Equine Encephalomyelitis virus (VEE), showed a significant decrease of DNA-dependent RNA polymerase type I activity of brain nuclei of 29.7% and 59.3% at 24 and 48 hours after infection, respectively, while the animals had no clinical symptoms of illness. No alterations were observed in the nuclei of mononuclear cells at any time. VEE virus titer was higher in the serum than in the brain. The results suggest that viral infection produced a modification in the activity of this enzyme only in brain, even with a low amount of virus, and had no effect on enzyme activity of mononuclear cells.

An electrophoretic analysis of proteolipids from different rat brain subcellular fractions

Proteolipid proteins were extracted from adult rat brain subcellular fractions and purified by chromatography on Sephadex LH-60. Polyacrylamide gel electrophoresis of the delipidized proteins, in the presence or absence of 8 M urea, was carried out with all fractions. The distribution of the various types of proteolipid proteins was studied and their molecular weight calculated by the Ferguson relationship. Several bands of proteolipid proteins were found in the five membrane fractions analyzed. Some of them, such as the 17.5 K and 37 K components were very prominent in mitochondria and synaptosomes. The 30 K component was found in myelin-derived membranes and in microsomes, while the 20 K and 25 K proteolipid proteins were present in all subcellular fractions. The 30 K component (proteolipid protein (PLP)), typical of the purified myelin membranes, showed a similar distribution to that of 2',3'-cyclic-nucleotide 3'-phosphohydrolase (EC 3.1.4.37) activity, while the other major proteolipid protein present in all subcellular fractions (25 K) did not show such parallelism, indicating that it might not be an exclusive component of myelin. The electrophoretic pattern of microsomal proteolipid proteins did not show the high molecular weight components (aggregates of PLP) which are found in myelin. Furthermore, the 30 K component showed a smaller Y0 value than that of the 30 K found in myelin. Thus the presence of 30 K proteolipid protein in microsomes should not be considered as being due to myelin contamination.

Rapid purification of proteolipids from rat brain subcellular fractions by chromatography on a lipophilic dextran gel

Proteolipids from adult rat brain subcellular fractions were purified by a one-step procedure involving chromatography through Sephadex LH-60 eluted with an acidified chloroform-methanol mixture. The protein peak was eluted with the void volume and was free of adventitious lipids. The degree of purification was similar to that attained with the neutral-acidified chloroform-methanol dialysis method with the advantage that this new procedure can be carried out in only 3 h, with a recovery of proteins of 95-100%. Samples containing different lipid/protein ratios passed through the gel gave similar elution profiles. When labeled amino acids or palmitic acid were added to myelin total lipid extracts, no radioactivity was eluted with the protein, indicating that the proteolipid apoproteins purified by this method do not adsorb hydrophobic low-molecular-weight compounds.