Rat Brain Microsomal Fraction Research Articles

Effect of intraventricular injections of brain isoantibodies on learning

The present method of assessing the effects of anti-brain isoantibody on learning involves multiple slow intraventricular injections of serum γ-globulin (IgG) into the lateral ventricles of chronically prepared unanesthetized subjects. Injections of 80 μl of normal rat IgG on the 8 days preceding training had no adverse effect on the abilities of the subjects to learn a visual discrimination problem. Such trained subjects also performed at criterion after they received an additional intraventricular injection of normal IgG on the day they reached criterion. In contrast, subjects that had received anti-brain IgG before training performed below criterion after they received an intraventricular injection of normal IgG on the day they reached criterion. Subjects that received intraventricular injections of immune IgG prepared from the sera of rats that had been immunized with the microsomal fraction of rat brain (RB F-III) or rat liver (RL F-III) required a statistically significant larger number of trials to learn a visual discrimination problem than control subjects that received normal rat IgG. The anti-RB F-III IgG had a more widespread effect than the anti-RL-F-III in that it produced subjects with statistically significantly higher latencies, poorer memories, and an unusual behavioral trait tentatively called “spinning”. The effect of the anti-RL F-III is believed to be due to its reaction with species-specific antigens in the brain whereas the more deleterious effect of the anti-RB F-III IgG is thought to be due to its reactivity with both species-specific and organ-specific antigens in the brain. The present experiments have confirmed and extended the results obtained earlier with actively immunized subjects.

Partial purification and ouabain sensitivity of lubrol-extracted sodium-potassium transport adenosine triphosphatases from brain and cardiac tissues

Lubrol extracts containing (Na + K)-activated adenosine triphosphatase of specific activity 70–100 μmoles P l/mg of protein/hr were prepared from rat brain microsomal fractions. The enzyme was stable in 0.32 M sucrose containing 1 mM EDTA at pH 6.9 and had properties, regarding optimal concentrations of ATP, Na and K required for maximal activation, similar to those of particulate preparations of the rat brain enzyme. The apparent K m for the enzyme was 5.0 × 10 −4 M and the optimal pH was 6.8. Sucrose density gradient separation further purified the (Na + K)-activated adenosine triphosphatase, but the resulting preparation was not homogeneous, despite high specific activity (400 μmoles P i/mg of protein/hr), and contained at least five protein staining bands on disc gel electrophoresis. Lubrol treatment was effective in extracting the enzyme from cardiac tissue of both rat and guinea pig and appeared to increase the sensitivity of the enzyme to ouabain. Enzymes of cerebral origin from the two species were of equal sensitivity to ouabain. The enzyme extracted by Lubrol treatment from guinea pig heart microsomes was 23 times more sensitive to ouabain than a similar preparation from rat heart.

Occurrence of light particles carrying DNA-like RNA in the microsomal fraction of adult rat brain

We have shown the existence of three types of entity in the 20–60-S sedimenting part of a deoxycholate-treated microsomal fraction of rat brain. 1. 1. 18-S ribosomal RNA-containing particles similar in sedimentation properties and density to those described previously by other authors in cells with a high mitotic index. 2. 2. DNA-like RNA-containing particles not described before in the cytoplasm of adult animal cells. The particles are highly labelled in brain, and part of them can be separated from the 18-S ribosomal RNA particles by their sedimentation behaviour. Their buoyant density and sedimentation properties suggest that they may be related to the polysomal-like complex described by Samarina, Lukanidin and Georgiev 1 in the liver nuclei. Their presence in the cytoplasm supports the hypothesis that such particles are involved in the transport of messenger RNA from the nucleus to the cytoplasm. 3. 3. Membranous structures resulting from the deoxycholate treatment without any RNA; these could be separated from other particles by using their flotation properties. After centrifugation, membranes floated on a 1.3 M sucrose layer whereas RNA-containing particles were found on 1.7 M sucrose.

Metabolism of sulfatides. I. The effect of galactocerebrosides on the synthesis of sulfatides

Sulfatides, the 3′-sulfate esters of galactocerebrosides, are components of the mammalian myelin sheath. The synthesis of these lipids can be followed by measuring the incorporation of S35-sulfate into the lipid fraction of brain (Davison and Gregson, 1962). In the rat cerebrum, the period of active synthesis of sulfatides invivo (Davison and Gregson, 1962) and invitro (McKhann, et al, 1965) coincides with the onset of the histological appearance of myelin.Despite the close chemical similarity of galactocerebrosides and sulfatides, their metabolic relationships have not been established. The studies reported in this paper indicate that galactocerebrosides are sulfated by a soluble enzyme obtained from the microsomal fraction of rat brain.