Twenty-five strains of mycobacteria, every strain taken from a different animal, were isolated from tuberculosis-like lesions of the submandibular lymph node or the mesenteric lymph node of swine. Fifteen strains were identified as Mycobacterium intracellulare, four strains as Mycobacterium scrofulaceum, three strains as Mycobacterium fortuitum, one as Mycobacterium tuberculosis, one as a chromogenic M. intracellulare, and one as an unidentified Group IV. Two strains (T-128 and T-167) were initially identified as M. intracellulare, as these were slow-growing nonphotochromogens, did not reduce nitrate, two week-arylsulfatase-positive, did not hydrolyze Tween 80, and ethambutol-resistant. They, however, showed urease, nicotinamidase and pyrazinamidase activities and differed from other M. intracellulare strains in several other characteristics. Majority of the porcine isolates of M. intracellulare were serotypes "Davis" and "IV." On the other hand, majority of the M. intracellulare strains isolated from patients in this country were serotypes "Arnold" and "Yandle." Findings suggest that swine infected with M. intracellulare probably are not the main source of M. intracellulare strains that infect humans. Characteristics of a rapid-growing mycobacterial strain, which was pathogenic for swine, were described. This organism was differentiated from known pathogens of rapid-growing mycobacteria, M. fortuitum and Mycobacterium chelonei.

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It was confirmed by passive transfer experiments that the function of thymus-derived cells specific for hamster erythrocytes (HRBC) was deficient in the low-responder mouse strains. 1) Antibody production against HRBC was enhanced by passive transfer of thymus cells from normal SL mice (high-responder) to normal C57BL/6 mice (low-responder). 2) The enhancing effect of passive transfer of thymus cells from SL mice was abrogated by pre-sensitization of the recipients (C57BL/6) with thymus cells from SL mice. 3) In C57BL/6 mice, antibody production against HRBC was enhanced by the transfer of lymph node or spleen cells from C57BL/6 mice which had been sensitized with HRBC in Freund's complete adjuvant or hamster lymphoma cells.

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Immune ribonucleic acid (iRNA) preparations were extracted from spleens of rabbits immunized either with Salmonella flagella or f₂ phage. The enzyme extract prepared from popliteal lymph node cells of immunized rabbits induced DNA synthesis in a cell-free system in the presence of iRNA. The enzyme activity was demonstrated only after stimulation with a corresponding antigen and was inhibited by large amounts of rifampicin, rifampicin derivatives or by treatment of the iRNA with ribonuclease, but neither actinomycin D nor mitomycin C affected it. Pretreatment of iRNA with deoxyribonuclease did not affect the enzyme activity. This DNA polymerise could induce DNA synthesis only by using the corresponding iRNA but not by using either normal RNA or iRNA prepared against another antigen. This new DNA presumably represents an intermediate in the antibody formation process specified by this enzyme using iRNA as a template.

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Two oligosaccharides were isolated from a partial hydrolysis of the lipopolysaccharide from Shigella dvsenteriae which had a common antigen with human red blood cells (RBC). A disaccharide sh-2 had a structure of O-β-D-galactosyl-(1→2)-D-galactose, and was active in the hemagglutination inhibition test between human O RBC and anti-S. dysenteriae chicken serum. A tetrasaccharide sh-12 was composed of galactose and rhamnose and was a more effective inhibitor than sh-2. Both oligosaccharides were assumed to be derived from the determinant structure of a common antigen. Serological specificity of the hemagglutinin in chicken serum was examined using these oligosaccharides and human milk oligosaccharides, and the 1→2 linked galactosyl residue was supposed to be important for determination of the heterophile RBC antigenicity.

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An immune ribonucleic acid (iRNA) preparation was made using phenol extracts of spleens of mice previously immunized with Salmonella tennessee flagella. An enzyme, also prepared from the spleens of these mice, induced the incorporation of ³H-UTP into the acid-insoluble fraction in a cell-free system in the presence of this RNA. The enzyme activity could be demonstrated from the spleens of immunized mice but not from normal ones, and this activity was also inhibited by two derivatives of rifamycin. Treatment with ribonuclease or heating at alkaline pH resulted in a loss of activity in added RNA. The ³H-uridine-labeled product was found resistant to ribo-nuclease treatment but became sensitive when the product was subjected to heat treatment. However, actinomycin D, mitomycin C or bleomycin A₂ did not inactivate the enzyme activity. These results suggest that this enzyme induces the incorporation of UTP into the acid-insoluble fraction using iRNA as a template and the product may be a newly synthesized RNA which forms a hybrid with iRNA. This enzyme activity may play a role in the antibody formation process, and may account for the in vivo replication of iRNA by this enzyme, viz., probably an RNA-dependent RNA replicase.

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Induction of cellular deoxyribonucleic acid synthesis by infection with bovine adenovirus type 3 was examined in 7 clones of a mouse cell line. Cellular DNA synthesis was induced by infection both at 37C and at 41C in 5 clones. In the other 2 clones, however, cellular DNA synthesis was induced only at 41C and not at 37C. In a clone non-inducible at 37C, the incubation at 41C prior to infection resulted in induction of cellular DNA synthesis at 37C. The preincubation effect was not inhibited by cyeloheximide during the incubation at 41C. In an other clone non-inducible at 37C, the preincubation effect was not observed. The existence of a temperature-dependent cellular factor(s) regulating the induction of cellular DNA synthesis was suggested.

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Interferon was produced in high yields in mouse L cell cultures infected with Newcastle disease virus, with a specific activity of the order of 10⁶ units per mg protein. It was partially purified by zinc acetate precipitation, carboxymethyl Sephadex chromatography, Sephadex gel filtration and pressure dialysis. On electrophoresis in polyacrylamide gel, it consisted of a fast-moving sharp component and a slow, broadly distributed component(s). The highest specific activity of the former component so far obtained was 8. 10⁷ units per mg protein, numerically the highest value ever reported for interferon. It was considered likely, however, that the protein components in the purified samples, revealed by staining of the electrophoresis gel, still represented mostly impurities. Gel filtration experiment indicated some heterogeneity of interferon in molecular weight but the major component was estimated to be 30000 in molecular weight. Interferon activity could be maintained without added preservatives for prolonged periods, provided that the protein concentration of the sample itself was high. One interferon unit as defined in this paper was found to correspond to 0.3 international unit.

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The cephalosporin β-lactamase from Pseudomonas aeruginosa GN918 was purified using CM-Sepha-dex column chromatography. The resulting preparation gave a single protein peak on electro-focusing column chromatography and a single protein band on polyacrylamide-gel electrophoresis. The specific enzyme activity was 22950 units per mg of the purified enzyme protein. The optimal pH was 7.5 and the optimal temperature was 40C for the hydrolysis of cephaloridine. Isoelectric point was 8.7 and the approximate molecular weight of the enzyme was found to be 34000±2000. The enzyme activity was inhibited by iodine, p-chloromercuribenzoate and semi-synthetic penicillins. The enzymological properties of the isolated preparation have been compared with β-lactamases derived from other gram-negative enteric bacteria.

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