Antibodies to human caudate nucleus neurons in Huntington's chorea

Antibodies reacting with neuronal cytoplasmic antigens present in normal human caudate and subthalamic nuclei were detected in 37 of 80 probands afflicted with Huntington's disease (HD). IgG antibodies were detected by immunofluorescence using frozen sections of unfixed normal human and rat brain. Specificity of IgG binding was confirmed using pepsin F(ab')2 fragments of IgG isolated from positive sera. In vitro complement fixation of IgG antibody was detected in 22 of 31 sera tested. Neuronal cytoplasmic antigens reacting with positive HD sera were diminished after trypsin or RNAase treatment of tissue sections but were not removed by DNAase, neuraminidase, EDTA, or dithiothreitol treatment. Antibody staining of neurons could be removed after absorption with isolated caudate nucleus neurons or by using perchloroacetic acid extracts of caudate nucleus. Prevalence of antibody reacting with neuronal cytoplasm was 3% in 60 normal controls and 6% among a wide variety of patients with diverse neurological disorders. However, one-third of 33 patients with Parkinson's disease showed presence of antineuronal antibody. Among patients with HD, a significant association was noted between duration of clinical disease greater than 7 yr and titers of antibody of 1:2 or greater (P less than 0.001). When 115 family members of HD probands were tested, 30% of unaffected spouses showed presence of antineuronal antibody. 23.2% of first-degree relatives at risk for developing HD was also positive (P less than 0.001). 10.5% of second-degree relatives showed presence of antineuronal antibody. These data may support an environmental or infectious factor somehow involved in the ultimate expression of HD.

Events Surrounding the Early Development of Euglena Chloroplasts: VII. Photocontrol of the Source Of Reducing Power for Chloramphenicol Reduction by the Ferredoxin-NADP Reductase System

d(-)threo-Chloramphenicol blocks chlorophyll and plastid protein synthesis in Euglena. During chloroplast development in white light, but not in red, the cells escape from chloramphenicol inhibition and chlorophyll formation is restored. Concomitantly, chloramphenicol is reduced. Reduction of chloramphenicol in an enzyme extract from Euglena requires NADPH and ferredoxin for maximal activity. Methyl viologen replaces ferredoxin, and when chemically reduced, ferredoxin or methyl viologen reduces chloramphenicol directly. This suggests that the enzyme involved is ferredoxin-NADP reductase. In agreement, crude extracts from wild type and W(3)BUL, a mutant lacking detectable plastids and plastid DNA, when separated on acrylamide gels, show a single band which reduces methyl viologen with NADPH, and its mobility is similar in wild type and in mutant W(3)BUL. The reductase is inducible by light and increases 3-fold in wild type in white or red light and 1.5-fold in W(3)BUL in white light. DCMU does not block chloramphenicol reduction in vivo indicating that electrons originate from sources other than photosynthetic electron transport. We infer that chloramphenicol is reduced by ferredoxin which receives electrons via ferredoxin-NADP reductase. The limiting step is not the enzyme but the source of reducing power which can be supplied from the cytoplasm, probably under control of the blue light receptor. Ferredoxin and ferredoxin NADP reductase appear to be coded in the nuclear genome, synthesized on cytoplasmic ribosomes, and join a group of enzymes which cannot be precisely localized, since they may be active anywhere from their site of synthesis in the cytoplasm to their place of deposition in the chloroplast.

Preferential protection of the minor groove of non-operator DNA by lac repressor against methylation by dimethyl sulphate

The binding of lactose repressor to non-operator DNA was studied by the modification of several DNA's, including glycosylated DNA, with dimethyl sulphate, which affects the minor and major grooves of DNA and single stranded DNA regions. The non-specific binding of the repressor to DNA protected the minor groove but apparently not the major groove of the DNA double helix against methylation and did not increase the content of single stranded DNA regions. This suggests that the repressor on binding to non-operator DNA makes contacts mainly in the minor groove of DNA and does not uncoil the DNA double helix. This is different from the interaction of the repressor with lactose operator DNA which occurs, as shown by Gilbert et al. (1), along both the major and the minor groove.