In order to know the mechanism controling the host specificity of tobacco mosaic virus (TMV), three species of plants showing various degrees of resistance to TMV or TMV-RNA infection were selected and the fate of infecting viral genome was studied. Extract was obtained from leaves 0.5-6hr after inoculation of ³²P-TMV or ³²P-TMV-RNA and analyzed by sucrose density gradient centrifugation. It was found that polysomes containing infecting 32P-RNA were formed in plants resistant to TMV to the same extent as in susceptible tobacco plants, suggesting that the host specificity of TMV is determined at a stage of viral multiplication later than the step of translation of infecting viral genome.

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Antibacterial activities of 146 chloramphenicol (CM) derivatives and analogues were investigated in a CM-resistant strain of Staphylococcus aureis. Seventeen compounds tested showed the same or much higher antibacterial activity when compared with CM. These compounds could be classified into two groups: The first group included ten compounds containing a benzoyl moiety in their structure and the remaining seven compounds did not possess that moiety. Compounds, which showed a fourfold higher antibacterial activity than CM, were six CM derivatives and two CM analogues. They were all included in the first group. Present and previous studies indicated that the most active CM-related compound was DL-α-dichloroacet-amido-α-methylene-P-nitropropiophenone, termed No. 61 (previously called CM 17). The mecha-nism of antibacterial activity of this compound was due to the fact that this was not inactivated be the CM acetyltransferase produced by the CM-resistant strain.

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Splenectomized mice were injected intravenously with Escherichia coli endotoxin or Newcastle disease virus at different intervals. Serum and various organs were taken at different intervals and tested for virus-inhibiting factor (IF) or interferon titer. Production of endotoxin-induced IF was depressed immediately after splenectomy. This depression was recovered in six weeks. IF was then formed mainly in the lung and liver. Splenectomy did not immediately affect IF production induced with virus. In the course of time, the production of late-appearing virus-induced IF was gradually depressed, whereas the formation of early-appearing virus-induced IF was progressively enhanced. These results were interpreted as follows: (1) Endotoxin-induced IF and virus-induced early IF are formed by different mechanisms, although these IFs have similar physicochemical properties; (2) In splenectomized mice, the activity of spleen to form endotoxin-induced IF may be compensated by certain cells in various organs, whereas that for production of virus-induced late IF is not; (3) The production of virus-induced late IF depends on the spleen by a somewhat indirect way. When mice were inoculated with virus within 60 days after splenectomy, the serum IF titer was higher than those of organs. These findings suggested that the organs examined were not the major sources of virus-induced serum IF in splenectomized mice.

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Serological evidence for dissemination of rhinovirus serotypes 3, 5, 13, 14, 17, 26, 30 and 41, and a Japanese isolate 149N, which has not been typed as yet. was obtained by measuring neutralizing antibody in a total of 750 serum samples collected in Iwate Prefecture, a northern part of the main island Honshu of Japan, in 1965 to 1969. Judging from the age-specific antibody incidence curves obtained by testing sera from outpatients at Iwate Medical College Hospital, the circulation of types 13, 14, 30 and 41 seems more active than that of types 3, 5. 17 and 26. Comparison in the age-specific antibody incidence between two groups of sera col-lected from outpatients at the hospital over different periods, October 1968-June 1969 and February-August 1968, revealed very active circulation of types 13, 14 and 30 over the period between the collections as compared with type 41. Some differences in the age preference were shown among the serotypes. The results of tests in different cities showed marked differences in the antibody distribution by age depending upon the place and serotype. Seroconversion was shown in some individuals who were tested one year apart. These findings are interpreted to indicate that there is a constant flux in the serotypes infecting any given population, and that several serotypes are usually circulating almost simultaneously.

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Purification of enterotoxin D from Staphylococcus aureus 494 was attempted by utilizing the following techniques: Concentration of bacterial culture supernatant with polyethylene glycol 20000, CM-cellulose column chromatography, Sephadex G-100 gel-filtration, chromatography on a DEAE cellulose column with concave gradient elution and gel-filtration with Sephadex G-50. The final preparation obtained gave a single precipitin line with anti-crude enterotoxin D serum and no precipitation with anti-enterotoxin A, B or C when it was tested by Ouchterlony's technique. It was capable of producing 100% emesis in monkeys at about 1.25μg of protein per kg body weight. Antiserum prepared by injecting rabbits with the purified preparation gave a single precipitin line with concentrated crude toxin, and it also gave a single are when tested in immuncelectrophoresis with concentrated crude toxin. A type-specific neutralization effect in monkeys was obtained. Thus, enterotoxin D has been identified with a purified preparation.

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From March 1971 through February 1972 isolation attempts of Yersinia enterocolitica were made on 442 specimens, consisting of 292 feces from patients hospitalized with symptoms of suggestive dysentery, 22 from sporadic cases of diarrhea in children, 43 specimens of ileum resected from autopsy cases which exhibited pathological changes in their intestine, and 85, appendix vermiformis which had been excised. A simultaneous survey on the normal distribution of the bacterium in healthy persons was conducted on 30587 fecal samples from adults and 402 specimens from newborns. As a result of the survey, 12 strains of Y. enterocolitica were isolated; two strains from the ileum of two autopsy cases, five from excised appendix vermiformis, two from feces of hospitalized patients suspected of dysentery, and three from feces of sporadic cases of diarrhea in children. No strains of this bacterium were isolated from healthy adults and newborns. Major pathological findings of autopsy cases were conspicuous hemorrhagic necrosis and edema of the small intetine, limited to within 1 meter of the ileocecum. Biotype and scrotype of 12 isolates were as follows; one isolate from an excised appendix vermiformis was blotype 2 and serotype 5B, while all of the remaining 11 were biotype 4 and scrotype 3. These results suggested that strains of a specific biotype and scrotype were likely to be playing a very important role in the development of this illness in man.

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Various single-stranded RNAs, which do not induce antiviral cell resistance in L and chick cmbryo cells, were found to antagonize the action of inducer RNAs such as poly (C)•poly (I). The non-inducing RNA inhibited production of interferon stimulated by inducer RNA, but did not inhibit the action of exogenously added interferon. Two aspects were discerned in the antagonism of non-inducing RNA, namely intrinsic antagonism and anti-protamine effect. The intrinsic antagonism is the one observed in the absence of protamine. The anti-protamine effect is elimination of the potentiating action of protamine on inducing RNA [10] by non-inducing RNA in a large excess over protamine. The relative importance of the two effects will vary depending on the concentrations of protamine and non-inducing RNA used. Non-inducer RNA added to cells pretreated with inducer RNA for 1-3hr effectively inhibited the development of antiviral cell resistance, but was not very effective when added prior to inducer RNA. RNA from MS2 phage virions was found to be an inducer in chick embryo cell but a non-inducer and antagonist in human embryo lung fibroblasts, indicating that a given RNA may possess both the inducer and the antagonist characters. The induction of interferon by viruses was not signifi-cantly inhibited by non-inducing RNA. The results obtained are consistent with an assumption that non-inducing RNA competitively inhibits the binding of inducer RNA to cellular receptor sites. although altcrnatise interpretations are not excluded.

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Crystalline material showing square lattice arrays attached to the cell envelope of Corynebacterium diphtheriae grown in liquid cultures was demonstrated under the electron microscope using negative staining and sectioning techniques. Two types of lattice patterns could be found in the crystal. One was a square lattice consisting of parallel lines (about 3.2nm in diameter) with an average distance between their centers of 5.3nm. The second type of lattice pattern was composed of thinner parallel lines (approximately 2.2nm in diameter) with a closer periodicity being about 3.5nm. The two types of lattice patterns appeared to intersect each other at an angle of 45 degrees. The lattice arrays were disorganized and disappeared upon treatment with proteolytic enzymes, alkali and sodium dodecyl sulfate. This crystalline material seemed to be composed of protein(s) but not to be related to diphtheria toxin.

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Antibacterial activity of rifampicin (RFP) against intracellular Shigella and enteropathogenic Escherichia coli was tested in a cell culture system and compared with that of known active controls such as chloramphenicol (CP), kanamycin (KM), streptomvcin (SM) or tetraeyeline (TC), with reference to minimal inhibitory concentrations (MIC) and to chemotherapeutic effecls on intraperitoneal infections in mice. When RFP, CP. or TC was applied to 1, cells and Hela cells infected respeetively with Shigella flexneri 2a and enteropathogenic E. coli 0143. both cellinfection and intracellular multiplication of the bacilli were considerably inhibited, while RFP was less active against the extracellular bacilli in cell∼free environments than KM and SM Comparing the intracellular antibacterial activity between RFP and TC or CP. the former was less active than the latter two. This discrepancy in antibacterial activity between extra-and intracellular environments could in part be attributed to the fact that RFP penetrated more easily into cultured cells than KM and SM did.

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