Akio Ohyama

Association between the pH-dependent conformational change of West Nile flavivirus E protein and virus-mediated membrane fusion.

The major envelope protein (E) of West Nile virus mediates fusion between the membranes of the viral envelope and the target cell at optimum pH values of just below neutrality. The fusion is critical for the entry mechanism, allowing virus to escape from the acidic endosomal compartment. To define the role of the viral E protein in the fusion reaction, the conformational change in E and concomitant change of viral infectivity were studied quantitatively, using protease digestion of the E protein and assay of viral infectivity. The results showed that the conformational change occurred in a pH-dependent manner with an upper threshold of pH 7.0 and maximum conversion occurring at pH 6.4 and below. The conversion was rapid and reached a half-maximal value within 15 s after acidification. The exposure of free or cell-bound virions to acid pH resulted in the loss of infectivity in an almost identical pH-dependent manner. Based on these findings, it is suggested that there are two distinct viral modes of entry into macrophages, i.e. infectious endocytosis and non-infectious viral fusion with plasma membranes, with the pH of the extracellular medium determining which of these predominates. The implications of these observations for the role of the E protein in membrane fusion and the probable localization of fusion epitopes are discussed.

Description of Achromobacter xylosoxidans Yabuuchi and Ohyama 1971

More than 70 characters of 55 strains of Achromobacter xylosoxidans were compared with those of the type strain of A. xylosoxidans, ATCC 27061 (= KM 543). Repeated examination of these 55 strains confirmed the stability of the flagellar morphology and biochemical reaction pattern and performed that the species can be recognized by these characters. Two strains of Alcaligenes faecalis, two strains of Alcaligenes denitrificans, five strains of Alcaligenes sp., and five strains of each of King groups IIIa and IIIb were identified as strains of A. xylosoxidans. The base compositions of the deoxyribonucleic acids of 20 strains are given. The cellular fatty acid composition of extractable and bound lipids of five strains was determined. The minimal characters for the identification of strains of A. xylosoxidans are presented.

In Vitro Antimicrobial Activity of Ceftizoxime Against Glucose-Nonfermentative Gram-Negative Rods

Ceftizoxime, a new cephalosporin, was active against Pseudomonas cepacia, Flavobacterium meningosepticum, Alcaligenes faecalis, and Acinetobacter calcoaceticus and was more potent against Pseudomonas aeruginosa and Pseudomonas putida than was carbenicillin.

Pseudomonas melanogena Iizuka and Komagata 1963, a Later Subjective Synonym of Pseudomonas maltophilia Hugh and Ryschenkow 1960

Strain IAM 1554 (ATCC 17806) is herein designated as the type strain of Pseudomonas melanogena Iizuka and Komagata 1963 and compared with ATCC 13637, the type strain of Pseudomonas maltophilia Hugh and Ryschenkow 1960. The three additional strains used in the original description of P. melanogena and five strains of P. maltophilia originally identified as Pseudomonas alcaligenes are also studied. The morphological and physiological attributes and deoxyribonucleic acid base compositions of the 10 strains are sufficiently similar so as to place these strains in a single species, the correct name of which is P. maltophilia. The name P. melanogena is reduced to being a junior synonym of P. maltophilia.

New sensitivity test using flow cytometry

SummaryFlow cytometry (FCM) has been used to evaluate not only the malignancy of tumor cells but also the effects of chemotherapy. Here a new application of FCM for selecting the best antineoplastic agent in the chemotherapy for brain tumors is reported.Through our preliminary study using established brain tumor cell lines, the system for this sensitivity test was developed. Antineoplastic agents were placed in contact with monolayer-cultured cells; then cell viability and changes in the DNA histogram were analyzed by FCM. Cell viabilities were measured with the fluorescein diacetate (FDA) staining method, and the DNA histogram was analyzed by the propidium iodide (PI) staining method. The best antineoplastic agent was determined based on changes in cell viability and cell cycle. In other words, when markedly decreased viability as compared with that of the control, is measured by FCM, then the agents can be considered to have had a cytocydal effect on the tumor cells, and thus the sensitivity of the agents is able to be evaluated. If the viability of the tumor cell is observed to be similar to that of the control, the cytostatic effects of the agents are able to be evaluated only if a marked change is observed in the DNA histogram.After the preliminary study, this system was applied clinically to malignant brain tumor cases, resulting in success in selecting the best antineoplastic agent for each individual case. Our sensitivity test using this FCM established in vitro system has much potential value for clinical use.

Electron Microscopic Observation of the Budding Maturation of Group B Arboviruses

In the maturation process of group A arboviruses as generally known immature particles are enveloped while passing into the lumen of cytoplasmic vacuoles or while being extruded through the cell membrane (2). Differing from group A arboviruses, numerous efforts by many investigators (1, 3-5, 7, 8, 10-14) have failed to provide enough informations on the morphological maturation process of group B arboviruses. Our study has been focused on an electron microscopic insight into such maturation process of group B arboviruses by which the envelope is formed around the nucleocapsid. Three mouse-adapted virus strains, Japanese encephalitis virus ( JEV) JaGAr-01, dengue virus (DV) type 4 H-241 (MB-2), and yellow fever virus (YFV) 17D, were used in this experiment. Vero cells were grown in Eagles minimum essential medium added with calf serum in 10%, and the infected cells were maintained with a decreased concentration, 2%, of calf serum. Monolayered Vero cell cultures were inoculated with each virus suspension prepared by the following procedure; a 10% suckling mouse brain emulsion made with Dulbeccos phosphate-buffered saline (PBS) was centrifuged at 1,000 rpm for 5 min, and the supernatant was diluted to 1:100 with PBS. The infected Vero cells were frozen and thawed at harvest to use the supernatant as inocula for the next passage. The culture interval was 4 days for the first passage and 48 hr after the 2nd passage. Infected Vero cells at various stages were subjected to fixation with 2% glutaraldehyde and then with 1% OsO4, followed by dehydration with ethanol in serial concentrations. Peroxidase-labeled antibody and ferritin-labeled antibody, specific for each of the 3 virus strains used, were prepared for immuno-electron microscopy according to Nakane and Kawaoi (9) and Singer and Schick (15). The specific fluorescence for JEV was observed by the fluorescent antibody technique at the perinuclear region of cytoplasm of Vero cells, 15 hr after inoculation of virus. The development of specific immunofluorescence was slightly delayed in DV and YFV, when compared with that of JEV. The specific fluorescence for each virus extended gradually into the cytoplasmic area from the juxtanuclear to

Comments on the Japanese Translation of the International Code of Nomenclature of Bacteria

In an attempt to facilitate proper understanding by Japanese bacteriologists of the rules which govern the nomenclature of bacteria, a Japanese translation of the International Code of Nomenclature of Bacteria was made by Ochi et al. (3). Proposals are here made to change several of the Japanese characters in the translation which do not accurately convey the intended meaning. (i) The Japanese terms “hyojun” and “kijun,” used to translate the English term “type,” should not be used in the Japanese text of the Code because they may lead the Japanese reader to misunderstand the nomenclatural type concept.The English term “type” should be used in the Japanese Code without translation. (ii) The Japanese term “keiyō-mei” was used t o translate the English term “epithet.” It should also be rejected because “keiyō-mei” may be understood by the Japanese reader as a word for “name.” “Keiyo-go” is proposed as a replacement for “keiy6-mei.”