Observer-rated ataxia: rating scales for assessment of genetic differences in ethanol-induced intoxication in mice.

Identification of genetic and physiological mechanisms underlying a drug's or mutation's effects on motor performance could be aided by the existence of a simple observation-based rating scale of ataxia for mice. Rating scales were developed to assess ataxia after ethanol (2.75, 3.0, and 3.25 g/kg) in nine inbred mouse strains. Each scale independently rates a single behavior. Raters, blinded to dose, scored four behaviors (splay of hind legs, wobbling, nose down, and belly drag) at each of four time points after injection. The severities of hind leg splaying and wobbling were quantifiable, whereas nose down and belly dragging were expressed in all-or-none fashion. Interrater reliabilities were substantial (0.75 0 at some time), but all doses were equally effective. Incidence of nose down and belly dragging behaviors increased strain dependently after ethanol, but strains did not differentially respond to dose. Ethanol-induced splaying was modestly, and negatively, genetically correlated with wobbling. Nose down and belly dragging tended to be associated with splaying and wobbling at later times. Four distinct ataxia-related behaviors were sensitive to ethanol. Strains differed in ethanol sensitivity for all measures. Modest strain mean correlations among behaviors indicate that these behaviors are probably under control of largely different genes and that ataxia rating scales should rate separate behaviors on discrete scales.     

A quantitative histochemical study of D-amino acid oxidase activity in rat liver in relationship with feeding conditions.

The histochemical method for the demonstration of D-amino acid oxidase activity in rat liver, based on the use of cerium ions and the diaminobenzidine-cobalt-hydrogen peroxide procedure, was improved by the application of unfixed cryostat sections and a semipermeable membrane interposed between section and gelled incubation medium. The amount of final reaction product precipitated in a granular form was about four times higher with this technique in comparison with conventional procedures using fixed sections and aqueous incubation media. The specificity of the reaction was proven by the 70% reduction of the amount of final reaction product when incubating in the presence of substrate and D,L-beta-hydroxybutyrate, a specific inhibitor of D-amino acid oxidase activity. Cytophotometric analysis of liver sections revealed that the specific test minus control reaction was linear with incubation time and section thickness. The Km value of the enzyme of 10.3 +/- 2.7 mM, as determined in periportal areas, is about five times the value found with biochemical methods in liver cell homogenates. The enzyme activity in periportal areas is about five times the activity in pericentral areas. Fasting (24 and 48 hr) induced a significant decrease in D-amino acid activity in periportal and pericentral areas. The possible physiological role of the enzyme in liver is discussed.