Thomas G. Kawakami

Genotoxicity of the phosphoramidate agent tabun (GA)

Five mutagenicity tests were performed on Agent GA (Tabun, phosphoramidocyanidic acid, dimethyl-, ethyl ester) as part of a program to demilitarize chemical warfare agents. GA was mutagenic in Salmonella spp. assays with S-9 and it was a direct-acting mutagen to mouse lymphoma cells. GA did not promote unscheduled DNA synthesis in rat hepatocytes; it induced sister chromatid exchanges in mouse cells in vitro but in vivo. The conclusion that GA is a weakly acting mutagen is supported by the fact that it was mutagenic in only three of the five assays, and that increases in mutagenicity were often less than 2-fold the controls and occurred near toxic levels.

Cyclic-3′,5′-AMP-dependent and independent protein kinase levels in normal and feline sarcoma virus transformed cells

Abstract The results of these studies have revealed no differences in the level of the cyclic-3′,5′-AMP (cAMP) -dependent or independent protein kinases, using calf thymus histone as substrate, in normal and feline sarcoma virus transformed cells. Similarly, the degree of responsiveness of the basal protein kinase activity to cAMP was also identical in the two cell types. These experiments have been carried out in normal, bovine-derived (thymic) fibroblasts and confirmed in feline-derived, embryonic mixed cell cultures. Thus, these results are consistent with the conclusion that one of the major amplification mechanisms for cAMP is not altered following viral transformation.

Studies on the prevalence of type C virus associated with gibbon hematopoietic neoplasms.

Gibbon malignancy frequently involves the hematopoietic system and can occur in clusters. Virus isolated from gibbon neoplasms possessed typical type C virus morphology, and the virion measured 100 nm in diameter with an electron-dense nucleoid measuring approximately 75 nm. The virus incorporated 3H-uridine into the nucleic acid and rested at a buoyant density of 1.14-1.16 g/cm3. Intra-and interspecific antigenic determinants were present, and the intraspecific antigenic determinant was shared with the woolly monkey sarcoma virus but not with feline or murine type C viruses. The virus and antibody reactive to the virus are more prevalent in gibbon groups that experience leukemia than those free of hematopoietic neoplasms.

Effects of administration of recombinant human interleukin-2 in dogs

The clinical and immunohaeamatological effects of recombinant humen interleukin-2 (rhIL-2) administration were evaluated in normal dogs. Three groups of three dogs per group were administered rhIL-2 subcutaneously at a dose of 6 × 104 IU, 6 × 105 IU, or 6 × 106 IU/kg once daily for five consecutive days. Toxic clinical signs were limited primarily to diarrhoea, the severity of which, was dose dependent, with resolution within 7 days of the last rhIL-2 injection. Marked circulating eosinophilia occurred in dogs of the two highest dose groups and transient rise in blood lymphocyte numbers occurred in dogs given the highest dose of rhIL-2. The most significant immunological effects were elevated in vitro conA and pokeweed mitogen-stimulated lymphocyte blastogenic responsiveness in the highest dose group and dose-dependent elevation of antigen-specific antibody (IgG and IgM) production. Peak relative antibody production was markedly elevated, as compared to controls, in dogs administered 6 × 105 IU, 6 × 106 IU rhIL-2/kg.

Establishment and partial characterization of a radiation-induced canine monocytic leukemic cell line (RK9ML-1)

A myeloid leukemic cell line, designated RK9ML-1, was established from a dog with acute radiation-induced monocytic leukemia. Based on cytochemical stains which reacted positively only with nonspecific esterase, morphological and ultrastructural characteristics which indicated the presence of phagocytic vacuoles and lysosomal bodies, and cell surface properties which indicated the presence of Fc receptors, all the findings support that RK9ML-1 is of monocytic lineage. Chromosomal analysis of the cell line indicated the cells to be hypodiploid with acrocentric autosomes characteristic of canine cells.

Oncogenicity of gibbon retrovirus determined by leukemia-specific genomic sequences

Abstract The genome of a type C virus, GaLV-5, isolated from several clinically healthy gibbons, was examined for the presence of nucleotide sequences related to the myelogenous leukemia-specific “MYE” RNA and the lymphocytic leukemia-specific “LYM” RNA which have been isolated from several strains of oncogenic GaLV (L. Sun and T. G. Kawakami, J. Virol. , 35 , 400–408 (1980)). The genomes of these oncogenic GaLVs were each separated into sequences homologous and nonhomologous to GaLV-5. Based on hybridization analysis, the nonhomologous RNA fractions were found to contain either the MYE RNA or the LYM RNA. This indicates that the leukemia-specific RNAs are lacking in the genome of GaLV-5. This lack was further confirmed by analysis of hybridization kinetics. The presence of leukemia-specific RNA sequences in GaLV genomes that were isolated from animals with leukemia and the absence of these sequences in virus strains isolated from animals free of clinical symptoms of leukemia indicate that the leukemia-specific RNA sequences are closely associated with the oncogenesis of leukemia in gibbons.