Elevated levels of dietary ascorbic acid increase immune responses in channel catfish

Channel catfish fingerlings were fed purified diets containing 0 to 3000 mg/kg of ascorbic acid until external signs of scurvy were seen in the fish fed the ascorbic acid-deficient diet. At this time, resistance to bacterial infection, antibody production, complement activity and phagocytic activity were assessed for fish from the various dietary treatments. Mortality rates of fish experimentally infected with Edwardsiella ictaluri, the bacterium causing enteric septicemia in channel catfish, decreased with increases in dietary ascorbic acid doses, ranging from 100% for fish fed the ascorbic acid-deficient diet to 15% for fish fed 300 mg ascorbic acid per kilogram diet and 0 for fish fed 3000 mg ascorbic acid per kilogram diet. Antibody response to E. ictaluri antigen, hemolysis of sensitized sheep erythrocytes by complement activity and phagocytic engulfment of E. ictaluri by peripheral phagocytes were each impaired in fish fed the diet without supplemental ascorbic acid; intracellular bactericidal activity of the phagocytes was not affected by ascorbic acid deficiency. There were no differences in antibody production, complement activity, or phagocytic activities among fish fed diets containing 30-300 mg ascorbic acid/kg of diet. However, the dose level of 3000 mg ascorbic acid/kg significantly enhanced antibody production and complement activity.

Viral integration near c-myc in 10-20% of mcf 247-induced AKR lymphomas

We induced AKR thymomas by injecting retrovirus MCF 247 that we had tagged with a fragment of phage lambda in its U3 region. About 10-20% of the 26 primary tumors studied showed both rearranged and germline c-myc bands in Southern blots. The rearranged c-myc genes were cloned from two of the tumors and studied by Southern analysis in two others. In all four cases, rearrangement was due to integration of MCF 247 proviruses about 2 kilobases (kb) 5' of the three c-myc exons and in the opposite transcriptional orientation. Thus, viral integrations were clustered within a 1-kb range in the tumors that revealed c-myc rearrangements. Three of the four proviruses appeared to be intact, whereas the fourth had an internal deletion of about 3 kb.

Critical phenomena and thermodynamics of dilute aqueous sodium chloride to 823 K

Semiempirical equations are developed that represent the behavior of dilute solutions of NaCl in water (steam) in the range 723-823 K where ion pairing is extensive. This supplements the equations given earlier for more concentrated solutions. In this temperature range the system NaCl/H(2)O shows critical behavior with two phases below the critical pressure. The equations for the dilute solutions yield critical behavior. Though the equations for concentrated solutions do not yield critical behavior at the critical pressure, only a very small interpolation function is required to connect smoothly the two equations. The ion-pairing equilibrium constants are reported as well as the Gibbs energies of hydration for both ions and ion pairs.