ABSTRACT
Chronic toxicity level of chemicals to bacteria can depend on composition and concentration of medium ingredients. This was demonstrated by means of a growth rate inhibition test with the marine bacterium V. fischeri. In a minimal medium (following the validity criterion of achieving a least cell multiplication rate) containing only yeast extract as organic nutrient component, V. fischeri was to Cu2+ 11.9 times, to Hg2+ 3 times and to Zn2+ 2.8 times more sensitive than in the complete defined medium. Obviously yeast extract did not interfere greatly in the complexation mechanisms. The detection limits of the toxicity of Cd2+, 3,5-dichorophenol and nitrobenzene were not influenced by the substrate.
Subject(s)
Culture Media , Vibrio/growth & development , Cadmium/toxicity , Chlorophenols/toxicity , Copper/toxicity , Mercury/toxicity , Nitrobenzenes/toxicity , Vibrio/drug effects , Yeasts , Zinc/toxicitySubject(s)
Athletic Injuries/rehabilitation , Joint Instability/rehabilitation , Physical Therapy Modalities/methods , Proprioception/physiology , Shoulder Dislocation/rehabilitation , Tennis/injuries , Adolescent , Athletic Injuries/physiopathology , Female , Humans , Joint Instability/physiopathology , Muscle Contraction/physiology , Range of Motion, Articular/physiology , Shoulder Dislocation/physiopathologyABSTRACT
Purified myelin of human brain from 15 young adult (below 50 years of age) and old (above 70 years of age) autopsy cases each was examined by isopycnic centrifugation in continuous sucrose gradients, and for lipid composition. The mean buoyant density of myelin was the same in both groups. Apparent features of old age were a wide range of density values, less compact myelin bands, and the dissociation of myelin into two bands in six of 15 old cases. Lipid analyses of randomly selected myelin samples of each group revealed an inverse relationship between the total lipid to protein ratio and density of myelin. In old age total lipids decreased by an average 10 mol lipid per mol protein. This decrease was accounted for by cholesterol, phosphatidylserine and cerebrosides. Changes in fatty acid moieties mainly affected sphingolipids. C20:0 and C24:0 of sphingomyelin increased, as did even more markedly the more hydrophilic OH-fatty acids of cerebrosides. Correlations with buoyant density existed for the ratios of cholesterol to protein in young adult cases, and those of galactolipids to protein in old cases. The results suggest that old age is associated with impaired stability and altered lipid composition of myelin.
