Hg2 plus-induced kidney necrosis. Subcellular localization and structure-linked lysosomal enzyme changes

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Low oxygen tension and discrimination reversal

An experimental group of 9 cats were trained to a visual form discrimination; the valences of the stimuli were then reversed and the cats were subjected to various levels of oxygen deprivation after which they were tested for retention and reversal performance. A normal control group ( N = 9) were trained identically to the experimental group but were not subjected to hypoxia. 10 naive cats constituted the post-hypoxia new-learning group. It was found that 70 min. of oxygen deprivation had a significant effect on retention and reversal performance; one exposure had no observable effect on either function. No differential effects were found on retention or new learning as measured by either retention new-learning or reversal-reversal comparisons.

Complement-fixing antigen from BHK-21 cell cultures infected with lymphocytic choriomeningitis virus

Infection of BHK-21 cells with lymphocytic choriomeningitis (LCM) virus resulted in the production of significant titers of complement-fixing (CF) antigen. The antigen was spontaneously released from the cells, but the highest titer of 1:16 was recovered by disruption of the infected cells by freeze-thawing in tryptose phosphate broth. The antigen could be partially separated from infectious virus by centrifugation. Furthermore, it was possible to detect LCM virus infection of cell cultures by the production of the CF antigen, but this method proved less sensitive than titration by intracerebral inoculation of mice. The CF antigen from cell cultures was at least as sensitive and specific as the reference antigen prepared from infected guinea pig spleen.

Effect of cations on structure-linked sedimentability of lysosomal hydrolases

1. A partially purified lysosomal preparation was obtained from mouse liver sucrose homogenates by differential and discontinuous gradient centrifugation. 2. Triton X-100 or repeated freezing and thawing of the lysosomal suspension (subfraction B) allowed comparison of free and activated values for acid phosphohydrolase, beta-glucuronidase and N-acetylglucosaminidase in the presence and absence of ascorbate. 3. The distribution of hydrolase activities between supernatant and pellet after high-speed centrifugation was measured and the percentages of total enzyme found in the supernatant were: acid phosphohydrolase, 40.7; beta-glucuronidase, 51; N-acetylglucosaminidase, 39.4. 4. Differential rates of elution of the three hydrolases from the membrane fraction occurred with increasing Na(+) and K(+) concentrations, whereas complex biphasic elution curves were obtained as a function of bivalent cation concentration with Ca(2+) and Mg(2+). 5. Sucrose-density-gradient centrifugation of frozen-and-thawed subfraction B demonstrated highly significant changes in the protein gradient profile in the presence of a low concentration of bivalent cation, indicating membrane aggregation and enzyme-membrane association. 6. The data provide further evidence for the nature of lysosomal enzyme binding and indicate the presence of different enzyme-membrane bonds conferring structure-linked latency upon individual lysosomal enzymes.

Fluorimetric determination of D-amino acid oxidase

1. A sensitive fluorimetric procedure for the assay of d-amino acid oxidase has been developed. 2. The method depends on the formation of a fluorescent derivative, 2-hydroxy-3-methylquinoxaline, on condensation of pyruvate with o-phenylenediamine in acid medium. 3. 2-Hydroxy-3-methylquinoxaline fluoresces strongly in 50% (v/v) sulphuric acid after excitation at 375mmu. A single emission peak is observed at 480mmu. 4. Formation of the quinoxaline is dependent on time, temperature, acidity and relative concentration of reactants. 5. A particulate preparation from mouse kidney required FAD for optimum activity at pH8.5; K(m) was 3.8x10(-3)m; K(FAD) was 1.4x10(-7)m and the reaction was strongly inhibited by p-chloromercuribenzoate and phenylmercuric acetate. 6. Subcellular fractionation on a sucrose density gradient confirmed that the d-amino acid oxidase was localized on small granules.

Development of a Scale of Optical Radiation

A description is given of the development ab initio of a scale of optical radiation, in terms of which sources can be calibrated for radiant intensity and detectors for radiant sensitivity. The scale is considered to be accurate to within about �O�2%.