Search PubMed⌕ Search

Biomedical subjects

K Amako

Publications and source records attributed to K Amako.

At least 109 records · Page 6Linked to original sources
PubMed1985

Motility as an intestinal colonization factor for Campylobacter jejuni.

The colonization of the intestinal tract of suckling mice by Campylobacter jejuni was examined by orally challenging the mice with a wild-type strain and several nonmotile mutant strains which were isolated after treating the wild-type strain with mutagens. The wild-type strain had colonized the lower portion of the small intestine, the caecum and the colon 2 d after inoculation. Two nonmotile strains, one of which (M8) had lost all the flagellar structure including the filament, the hook and the basal structure, and the other (M1) which had lost only the filament region, were both cleared from the intestinal tract 2 d after challenge. Another nonmotile strain (M14), which had a complete flagellar structure like that of the wild-type strain, did not colonize and was cleared from the intestinal tract like the other nonmotile and nonflagellated strains. One atypically motile strain (M5), which had a shorter flagellar filament than that of the wild-type strain, colonized the intestinal tract only when mice were challenged with a large inoculum. None of the mice challenged with either the wild-type or any of the mutant strains showed signs of illness. We concluded that motility is an important factor in the colonization of the intestinal tract of suckling mice by C. jejuni.

Adhesiveness↗
PubMed1984

Evidence for the presence of a capsule in Vibrio vulnificus.

Vibrio vulnificus strain FCC, isolated from a patient with a wound infection, and reference strain ATCC 27562, were examined by electron microscopy for the presence of capsules. Both strains had a layer heavily stained with ruthenium red. The number of stained cells was high in strain FCC and low in strain ATCC 27562. The proportion of stained cells correlated with virulence against mice and with susceptibility to the bactericidal activity of normal human serum. Rapid freezing and substitution fixation, a mild method, revealed on the cell surface a fibrous layer of relatively low electron density, which we considered to represent a capsule.

Blood Bactericidal Activity↗
PubMed1984

Cross wall synthesis and the arrangement of the wall polymers in the cell wall of Staphylococcus spp.

The growing process and the fine structure of the cross wall of Staphylococcus were investigated by electron microscopy. Examination of the tangentially sectioned cross wall revealed that it was initially synthesized as a thin cell wall layer by an invaginated cytoplasmic membrane. The wall thickness soon increased by additional synthesis of the wall from the cytoplasmic membrane located at the side region of the cross wall. Scanning electron microscopic observation of sodium dodecyl sulfate-treated and mechanically separated cross walls revealed that the outer surface of the cross wall exhibits regular circular structures and the inner surface showed has an irregular surface. This indicates that cell wall materials were arranged in a regular circular manner in the initially synthesized thin layer. It is conceivable that in Staphylococcus spp. two cell wall synthesizing systems are present: wall-elongation synthesis in which wall materials are arranged in a regular circular manner and wall-thickening synthesis in which wall materials are arranged in an irregular manner.

Cell Wall↗
PubMed1984

Purification and characterization of Serratia marcescens US5 pili.

The pili of Serratia marcescens US5 isolated from a patient with urinary tract infection were purified and characterized. During the aeration culture, the pili were detached from the bacteria and were precipitated by the addition of ammonium sulfate. The purification of the pili was carried out by ion-exchange chromatography and gel filtration on Sepharose 4B. In electron microscopy, the purified pilus showed a filament of 3 nm in diameter and 0.3 micron in average length. The molecular weight of the protein subunit of the purified pili was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two protein bands appeared. One has a molecular size of 19,000 daltons, and the other has a molecular size of 39,000 daltons. The isoelectric point was 3.7. The content of hydrophobic amino acids in purified pili subunits was 42% of the total amino acid content. Further purification of pili by isopycnic centrifugation failed to remove the large protein band. No identical protein bands to pili proteins were detected in the electrophoresis pattern of the outer membrane proteins extracted from S. marcescens US5 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These two proteins might be a dimer of a small molecule. A survey of clinically isolated strains of S. marcescens revealed that more than 60% of the strains had this type of pili. These results suggest that these pili are widely distributed among strains of S. marcescens.

Agglutination↗
PubMed1983

Morphological differences in flagella in Campylobacter fetus subsp. intestinalis and C. fetus subsp. jejuni.

Intact flagella were isolated from human pathogenic strains of Campylobacter, C. fetus subsp. intestinalis and C. fetus subsp. jejuni, by the method of DePamphilis and Adler and examined by electron microscopy. The isolated flagella were composed of a filament, a hook, a basal body, and a large disk associated with the end of the hook region covering the basal body. The width of the hook was approximately 28 nm, somewhat greater than that of the filament (20 nm in diameter). The hook region of C. fetus subsp. intestinalis was curved, but it was straight in C. fetus subsp. jejuni. The structure of the basal body of the two subspecies was similar to that reported for other gram-negative bacteria. The large disk detached from the flagella showed concentrically arranged circular structures. This structure was more clearly observed in the disk of C. fetus subsp. jejuni than in C. fetus subsp. intestinalis. Observations of thin-sectioned profiles at the attachment site of the flagellum revealed that the large disk is located on the inner side of the outer membrane. The role of the large disk in bacterial movement is not clear, but it is assumed that it acts as an organ to protect the flagellar insertion site from vigorous rotation of the polar end inflicted during bacterial movement.

Campylobacter fetus↗
PubMed1983

Growth of the surface of Corynebacterium diphtheriae.

Surface structure and growth of the surface of Corynebacterium diphtheriae mitis strain were investigated by scanning electron microscopy and the immunofluorescence technique. The surface of the cell revealed by the scanning electron microscope showed a few elevated circular zones which encompassed the cell. The cell diameter increased at this zone and this gave the club-shaped appearance to this species. The cell surface labeled with specific antibodies against the whole bacterial cell and tagged with ferritin remained at a constant length during cell division cycles and the new cell surface emerged from the polar ends of the cell. This new wall surface was completely devoid of the ferritin particles indicating that the cell wall component on the old preexistent wall was completely conserved. A similar finding was obtained by immunofluorescence microscopy. C. diphtheriae, unlike Bacillus spp., showed apical growth as has been observed in fungal cells.

Cell Division↗
PubMed1982

Arrangement of peptidoglycan in the cell wall of Staphylococcus spp.

The arrangement of peptidoglycan in the cell wall of Staphylococcus was observed with the newly developed freeze-fracture technique, using n-octanol instead of water as the freezing medium. The replica of the trichloroacetic acid-extracted cell wall (TCA-wall) showed two areas. One of them has a concentric circular structure, a characteristic surface structure of the staphylococcal cell wall, and the other showed an irregular and rough surface. The chemical analysis of the wall revealed that the TCA-wall consisted of mostly peptidoglycan. By digesting the TCA-wall with lysozyme, the circular structures were greatly disturbed, and they disappeared after 60 min of treatment. From these observations it can be expected that the peptidoglycan is arranged in a concentric circular manner in the newly generated cell wall of Staphylococcus.

Cell Wall↗
PubMed1981

Pili mediated agglutination of Serratia marcescens in human urine.

Of 51 strains of Serratia marcescens isolated from patients with urinary or respiratory tract infections, 35 agglutinated in human urine. The agglutinating strains possessed numerous pili which were morphologically distinct from common pili or type I pili. The diameter of the pili was 3 nm and the average length was 0.3 micrometer. Electron microscopic examination showed that 80% or more of the cells of the agglutinating strains and 0 to 8% of the cells of the nonagglutinating strains were piliated. When an agglutinating strain was heated at 55 C for 10 min, it lost its agglutinating capacity and concomitantly its pili. These results suggest that the agglutination might occur because of interactions between the pili and some factors in human urine. The urinary slime appears to contain these agglutinating factors.

Agglutination↗