Adaptive Potentials of Skeletal Muscle in Young and Aging Rats

We compared responses of the fast extensor digitorum longus (EDL) and tibialis anterior (TA) muscles in young (15-week) and aging (101-week) male Brown Norwegian rats to 50 days of chronic low-frequency stimulation (CLFS, 10 Hz, 10 hours/day). After 50 days of CLFS, the EDL muscles of the young (22-week) and aging (108-week) rats displayed similar increases in type IIA fibers, relative concentration of myosin heavy chain MHCIIa, elevations in mitochondrial citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities, and similar decreases in glycolytic enzyme activities (glyceraldehydephosphate dehydrogenase, lactate dehydrogenase). TA muscle in young rats contained a few cytochrome c oxidase negative (COX−) type I fibers. Their number was ~2-fold elevated by CLFS. Conversely, aging muscle, which contained a slightly higher amount of COX− fibers than young TA muscle, responded to CLFS with a significant decrease in COX− fibers. The appearance of small COX-positive type I fibers in stimulated aging muscle indicated that regenerating type I fibers “diluted” the COX-deficient fiber population.

Inhibition of Fructolysis in Boar Spermatozoa by the Male Antifertility Agent (S)-a-Chlorohydrin

The (S)-isomer of the male antifertility agent IX-chlorohydrin strongly inhibited the oxidative metabolism of fructose by boar spermatozoa in vitro. The result of this action, which has been deduced to be an inhibition of glyceraldehydephosphate dehydrogenase, caused an accumulation of fructose- 1,6-bisphosphate and the triosephosphates, and a decrease in substrate-level phosphorylation with a concomitant lowering of the energy charge potential of the spermatozoa. The (R)-isomer of IX-chlorohydrin had no inhibitory activity on fructolysis.

On the Action of Chlorosis-Inducing Herbicides in Leaves

The chlorosis induced by several different herbicides (group 1: aminotriazole, haloxidine; group 2: Sandoz 6706, difunon) in developing leaves of rye seedlings (Secale cereale L.) growing in light of 5,000 lx was, in addition to the absence of chlorophyll and carotenoids, accompanied by specific deficiencies of the 70 S ribosomes and of both chloroplastic and peroxisomal enzymes as previously described (Plant Physiol. 61, 1017 - 1022 (1978)) while growth and mitochondrial activities were little or not impaired. In dim light (10 lx) chlorophyll was formed and the chloroplastic and peroxisomal enzymes reached activities comparable to those in untreated leaves at 10 lx. Upon exposure to 30,000 lx a rapid bleaching of existing chlorophyll and a rapid inactivation of the plastidic enzyme NADP-glyceraldehydephosphate dehydrogenase occured after treatment with herbicides of group 2 but not in the presence of herbicides of group 1. After all treatments catalase was rapidly inactivated after transfer to high light intensity. The bleaching of chlorophyll and the enzyme inactivations occurred also at 0 °C. In the herbicide-bleached leaves grown at 5,000 lx the in vivo synthesis of (δ-aminolevulinic acid was low and in the presence of Sandoz 6706 and difunon the capacity for protochlorophyll (ide) synthesis was largely inactivated.