Purification and properties of spleen necrosis virus DNA polymerase

DNA polymerase was purified to apparent electrophoretic homogeneity from virions of spleen necrosis virus (SNV). (SNV is a member of the reticuloendotheliosis group of avian ribodeoxyviruses). The SNV DNA polymerase appears to consist of a single polypeptide with a molecular weight of 68,000. The SNV DNA polymerase has a preference for Mn2+ for DNA synthesis with an RNA template and Mg2+ for DNA synthesis with a deoxyribohomopolymer template. At the optimum concentrations of divalent cation, the relative rates of DNA synthesis by SNV DNA polymerase with different template.primers were similar to the relative rates of DNA synthesis by an avian leukosis virus DNA polymerase, with the exception of a lower relative rate of DNA synthesis by SNV DNA polymerase with SNV RNA. However, in contrast to DNA synthesized by the avian leukosis virus DNA polymerase with a SNV RNA template, DNA synthesized by SNV DNA polymerase with an SNV RNA template did not hybridize to the SNV RNA. SNV DNA polymerase has RNase H activity which is antigenically distinct from the RNase H activity of avian leukosis-sarcoma virus DNA polymerase.

Lymphocyte-increasing action and hypocalcemic action of parotid gland extract

It has previously been shown in our laboratory that the hypocalcemic substances purified from the thymus have a potent lymphocyte-increasing action in mice. Then, lymphocyte-increasing activity was examined with bovine parotid gland extracts, which showed a hypocalcemic activity as potent as that of the thymus extracts. The lymphocyte-increasing activity was assayed in the littermates of neonatal mice of Swiss-Webster strain; the materials used for this experiment were purified preparations and several fractions obtained from the parotid gland extracts in the course of purification. It was found that the potency of lymphocyte-increasing activity rose approximately in parallel with the rise in hypocalcemic activity with progress in purification. The final product, which was purified from the gland by isoelectric precipitation at pH 5.4, fractional precipitation with ammonium sulfate, chromatography on DEAE-cellulose, gel filtration on Sepharose 6B and preparative disc electrophoresis, gave a single band in polyacrylamide gel electrophoresis. Its intravenous injection in rabbits, in a dose of 10 mug/kg, produced a significant lowering in serum calcium (percent decrease 10.24 +/- 1.06%) compared with control animals given an injection of physiological saline. Intraperitoneal injection of this purified product, in a dose of 0.5 mug/mouse, in the littermates of neonatal mice, also produced a significant increase (ratio of lymphocytes to polymorphs 2.47 +/- 0.07) in lymphocytes compared with control animals injected with physiological saline (L/P ratio 1.57 +/- 0.05). These facts suggest that this purified protein fraction inherently contains both activities, but the possibility cannot be ruled out of slight contamination by a substance having a high activity. On the other hand, a fraction having no activity for lowering serum calcium but which had activity for increasing the lymphocytes was obtained. This is the first paper to report the presence of lymphocyte-increasing substances in the bovine parotid gland and the purification of one of the substances from the gland.

A hypocalcemic and lympnocyte-stimulating substance isolated from thymus extracts, and its physicochemical properties

Two kinds of active protein fraction, TP1 and TP2, were isolated from bovine thymus extracts. Both these fractions showed a single band in polyacrylamide gel disc electrophoresis. Though these two fractions showed a difference in potency, they both lowered serum calcium in rabbits and increased lymphocytes in mice. Molecular weight determination by SDS polyacrylamide gel electrophoresis gave the values of 68,000 for TP1 and 57,000 for TP2. Amino acid composition of TP1 did not show marked characteristics but was clearly different from that of bovine serum albumin. Isoelectric focusing showed the isoelectric point at pH 5.65 for TP1 and pH 5.4 for TP2. Dose-response relation in serum calcium-lowering activity was examined with a sample purified from the extracts, and a linear dependence of the response to log dose was recognized over a moderate range of doses. The time-course measurement of the hypocalcemic activity showed that the action of TP1 is somewhat different from that of calcitonin.

Cytochemical demonstration of ornithine carbamoyltransferase activity in liver mitochondria of rat and mouse

In order to demonstrate ornithine carbamoyltransferase activity cytochemically, thin slices of liver and kidney of rat and mouse were fixed in cold acetone or formol-calcium, and incubated in a medium containing l-ornithine, carbamoyl phosphate, Tris-maleate buffer (pH 7.2), lead nitrate and sucrose. The specific reaction product occurred in the mitochondria of the hepatocytes only, and not in other cells of the liver or kidney. The specificity of the reaction was supported by the following observations. (1) The mitochondrial reaction was not obtained in sections incubated in a medium from which ornithine was omitted. (2) Other amino acids gave no reaction. (3) p-Chloromercuribenzoate suppressed the reaction. (4) The hepatocytes of chick (uricotelic) did not give the reaction. A nonspecific reaction in lysosomes and brush borders is caused probably by acid and alkaline phosphatase activities.