Rat pups maintained on copper (Cu)-adequate (6ppm), Cu-deficient (2 ppm) or Cu-depleted (0 ppm) diets from parturition were killed at 8-wk. Liver Cu and serum-ceruloplasmin levels confirmed that on the 0- and 2-ppm diets, a Cu-deficient state was induced. Although body weight was unaffected by the deficiency, the liver, heart, and thymus weights (% body weight) were altered. Hepatomegaly occurred in females fed 0-ppm Cu and males fed 2-ppm Cu. Heart weights increased in both sexes fed 0-ppm Cu. Thymus weights decreased in male rats fed 0-ppm Cu. Antibody titers and natural killer-cell cytotoxicity were markedly suppressed in the animals fed 0-ppm Cu. Male rats given 2-ppm Cu showed reduced antibody titer. Delayed-type hypersensitivity and prostaglandin E2 levels were not significantly affected. These studies suggest that certain components of the immune system are Cu dependent.

No abstract

N-Ethylmaleimide modified heavy meromyosin in only 3-fold activated by actin rather than 200-fold as is normal heavy meromyosin (Silverman, R., Eisenberg, E., and Kielley, W. W. (1972), Nature (London) 240, 207). Ultracentrifuge studies demonstrated that in the absence of ATP the N-ethylmaleimide modified heavy meromyosin binds to actin at a ratio of 2 actins to 1 N-ethylmaleimide modified heavy meromyosin. However, it was found that most of the N-ethylmaleimide modified heavy meromyosin was not bound to actin during ATP hydrolysis. Ultracentrifuge studies demonstrated that in the presence of 25 or 50 mM KCl under conditions where the ATPase is maximally activated by actin, less than 5% of the N-ethylmaleimide modified heavy meromyosin was bound to actin. In the absence of KCl there was limited binding but even this binding did not appear to correlate with the N-ethylmaleimide modified heavy meromyosin ATPase rate. Turbidity and viscosity studies also indicated that in the presence of ATP under conditions of maximal actin activation the N-ethylmaleimide modified heavy meromyosin and actin are almost completely dissociated, whereas there is a marked increase in turbidity and viscosity after all of the ATP is hydrolyzed. These results suggest that in the presence of ATP and actin N-ethylmaleimide modified heavy meromyosin exists most of the time in a refractory state unable to bind to actin and only a small part of the time in a nonrefractory state which can interact with actin. It follows that the major rate-limiting step during actin activation is the transition from the refractory to the nonrefractory state. Since the actin activation of N-ethylmaleimide modified heavy meromyosin is lower than that of normal heavy meromyosin this transition may be slower for N-ethylmaleimide modified heavy meromyosin than for normal heavy meromyosin.

No abstract

From birth mice received diets containing copper at 0.5, 1, 2 or 6 mg/kg diet. At 8 wk of age they were killed and copper status and immune responsiveness were determined. Only the groups that received copper at 0.5 or 1 mg/kg showed signs of copper deficiency, such as reduced serum ceruloplasmin, hemoglobin, hematocrit and red blood cell counts and characteristic changes in organ pathology. Body and lymphoid organ weights were altered in the groups that received copper at 0.5 or 1 mg/kg. Males were more severely affected than females. A dose-related reduction in splenic T-cell subpopulations was noted in the 0.5 and 1 mg/kg groups. Responses to lipopolysaccharide challenge were reduced, and an increase in spontaneous cycling cells was noted in the groups receiving copper at 0.5 or 1 mg/kg. Only the group receiving copper at 0.5 mg/kg had increased stem cell activity; this increase was probably due to increased erythropoiesis to meet increased demands for red blood cells in this group. These data indicate that only groups receiving copper at 0.5 or 1 mg/kg in the diet were depleted and marginally depleted in copper, respectively, and that immune hyporesponsiveness differs between the depleted and marginally depleted groups.