Ultrastructure of a Hexagonal Array in Exosporium of a Highly Sporogenic Mutant of Clostridium botulinum Type A Revealed by Electron Microscopy Using Optical Diffraction and Filtration

The ultrastructure of a hexagonal array in the exosporium from spores of a highly sporogenic mutant of Clostridium botulinum type A strain 190L was studied by electron microscopy of negatively stained exosporium fragments using optical diffraction and filtration. The exosporium was composed of three or more lamellae showing an equilateral, hexagonal periodicity. Images of the single exosporium layer from which the noise had been filtered optically revealed that the hexagonally arranged, morphological unit of the exosporium was composed of three globular subunits about 2.1 nm in diameter which were arranged at the vertices of an equilateral triangle with sides of about 2.4 nm. The morphological units were arranged with a spacing of about 4.5 nm. The adjacent globular subunits appeared to be interconnected by delicate linkers.     

Isolation of Nontoxigenic Variants Associated with Enhanced Sporulation and Alteration in the Cell Wall from Clostridium botulinum Type A 190L by Treatment with Detergents

Nontoxigenic variants were isolated from Clostridium botulinum type A strain 190L after treatment with detergents such as deoxycholate, sodium dodecyl sulfate, Tween 80 and Brij-58. Deoxycholate was most effective for obtaining the variants. The variants exhibited a markedly increased frequency of sporulation compared with the oligosporogenic parent strain. The cell wall of the parent strain was composed of an outer layer and an inner layer, whereas that of the variants lost the outer layer. After treatment with mitomycin C the parent strain was subjected to lysis and produced bacteriophages with a hexagonal head and a contractible tail, while the nontoxigenic variants did not yield bacteriophages or phage-like structures. There appears to be a close relationship among the toxigenic and sporogenic properties, formation of the outer cell wall layer and lysogeny.     

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin‐dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA‐treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA‐treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA‐induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.     

Studies on the Structure of Gluco-oligosaccharides Obtained from the Partial Acid Hydrolyzate of Sclerotia of Sclerotinia libertiana

The defatted sclerotia powder was partially hydrolyzed with dilute acid, and the material obtained was fractionated by carbon column chromatography, separated into two disaccharides, three trisaccharides and three tetrasaccharides, respectively. In these hydrolyzates α, α-trehalose, Iaminaribiose, and gentiobiose were identified.     

Identification of heterogeneous and microheterogeneous subunits of glutathione S-transferase in rat liver cytosol

Subunits of multiple molecular forms of dimeric glutathione S-transferase in rat liver cytosol were analyzed by two-dimensional gel electrophoresis (isoelectric focusing/sodium dodecyl sulfate-electrophoresis) followed by staining with Coomassie blue dye. The five subunits, Ya, Yb, Yb', Yc, and Yp (Mr's 26,500, 27,500, 27,500, 28,500, and 26,000, respectively) of seven molecular forms, A2, AC, C2, B2, BL, L2, and GST-P, were identified by comparison of molecular weights and pI values with those of purified molecular forms and by immunoadsorption of the molecular forms in the cytosol as well as those synthesized in vitro using antibodies against the seven forms. Yp is the subunit of placental glutathione S-transferase, GST-P (YpYp), which is markedly increased in carcinogen-treated rat livers [A. Kitahara et al. (1984) Cancer Res. 44, 2698-2703; K. Satoh et al. (1985) Proc. Natl. Acad. Sci. USA 82, 3964-3968]. Microheterogeneity was detectable within Yb, Yb', and Yp subunits, the different forms, termed Yb1, Yb2, Yb'1, Yb'2, and Yp1, Yp2, being similar in size but differing by approx. 0.3 pI unit within each subunit. These microheterogeneous forms were also detectable in the polypeptides translated in vitro in a rabbit reticulocyte lysate translation system from liver poly(A)-containing RNAs, suggesting that they are translatable from distinct mRNAs.     

A preliminary study on quantitative relations among growth,reproduction and mortality in fishes

As a quantitative approach to the life histories of fishes, the present paper attempted to predict a relation among reproduction, growth and mortality numerically with a technique of control theory, the discrete maximum principle. A method for predicting the relation was derived on the postulate that natural selection maximized the net reproductive rate subject to a few constraints. The derived method was applied to Atlantic cod and Atlantic herring populations in the Southern Gulf of St. Lawrence as numerical examples. The examples demonstrated that the theoretical reproductive effort and body weight were well consistent with the observed ones every age but the theoretical survival rates were slightly different from the observed ones. For the reasons mentioned below, however, it should be interpreted that the examples rather support the adopted postulate to a certain degree. First, in general, it is very difficult to obtain good estimates of the rates with traditional methods. Second, intense fishing pressure possibly changes the life history parameters to some extent in fish populations. Moreover, the examples also suggested that, to examine the postulate in further detail, similar analyses had to be made with the data of many fish populations on which intense fishing pressure had not been exerted.     

A novel photoaffinity ligand for the phencyclidine site of the N-methyl-D-aspartate receptor labels a Mr 120,000 polypeptide

A radiolabeled photoaffinity ligand has been developed for the N-methyl-D-aspartate (NMDA)-preferring excitatory amino acid receptor complex. [3H]3-Azido-(5S, 10R)(+)-5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-imine [3H]3-azido-MK-801 demonstrated nearly identical affinity, density of binding sites, selectivity, pH sensitivity, and pharmacological profile in reversible binding assays with guinea pig brain homogenates to those displayed by its parent compound, MK-801. When employed in a photo-labeling protocol designed to optimize specific incorporation, [3H]3-azido-MK-801 labeled a single protein band which migrated in sodium dodecyl sulfate-polyacrylamide gels with Mr = 120,000. Incorporation of tritium into this band was completely inhibited when homogenates and [3H]3-azido-MK-801 were coincubated with 10 microM phencyclidine. These data suggest that the phencyclidine site of the NMDA receptor complex is at least in part comprised of a Mr = 120,000 polypeptide.