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Biomedical subjects

K Amako

Publications and source records attributed to K Amako.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Induction by Staphylococcus aureus L-form of tumor necrosis factor-alpha from macrophages].

Induction of tumor necrosis factor-alpha (TNF-alpha) by Staphylococcus aureus L-form was investigated. The supernatant of a macrophage culture mixed with S. aureus L-form showed a potent cytotoxic activity to L cells. Addition of anti TNF-alpha antibody inhibited completely the cytotoxic activity of the supernatant, indicating that the activity might be due mostly to TNF-alpha. To investigate localization of TNF-alpha production, the membranes of hypotonicity treated L-form were layered on a step-gradient composed of an upper and lower layers of 35% and 50% sucrose, respectively. The membranes were banded at the interface of 35% and 50% of sucrose. The activity of TNF-alpha production of the membrane fraction was 10-times higher than that of the soluble fraction.

Animals↗
PubMed1989

Basic amphipathic helical peptides induce destabilization and fusion of acidic and neutral liposomes.

We have studied the fusion of small unilamellar vesicles composed of egg PC and of a mixture of egg PC plus egg PA using various basic amphipathic peptides. Fusion was monitored by carboxyfluorescein leakage assay, light scattering, membrane intermixing assay, contents mixing assay and electron microscopy. Ac-(L-Leu-L-Ala-L-Arg-L-Leu)3-NHCH3 (peptide 4(3] and Ac-(L-Leu-L-Ala-L-Lys-L-Leu)3-NHCH3 (peptide 4'3), which have high hydrophobic moments, caused transformation of small unilamellar vesicles into larger and relatively homogeneous ones. Ac-(L-Leu-L-Leu-L-Ala-L-Arg-L-Leu)2-NHCH3 (5(2], which has medium hydrophobic moment, induced weak but appreciable fusion, while Ac-(L-Ala-L-Arg-L-Leu)3-NHCH3 (3(3] which has no helical structure did not show any fusion. However, peptides 4(3), 4'3 and 5(2) caused massive leakage of the contents from small unilamellar vesicles. These results indicated that interaction of the peptides with artificial membranes caused extensive perturbation of the lipid bilayer, followed by fusion. The fusogenic capacity of model basic peptides was correlated with the hydrophobic moment of each peptide when the peptides adopted an alpha-helical structure in the presence of acidic liposomes. Peptides 4(3) and 4'3 also showed weak fusogenic ability for neutral liposomes, while 5(2) and 3(3) showed no ability, suggesting that highly amphipathic peptides, such as 4(3), interact weakly but distinctly with neutral liposomes to fuse them.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Extraction from prawn shells of substances cryoprotective for Vibrio cholerae.

Substances cryoprotective for Vibrio cholerae were detected from prawn shells immersed in phosphate-buffered saline. This cryoprotective activity was heat resistant and sensitive to treatment with trypsin. For the exhibition of its full activity, the presence of Mg ion was indispensable. The cryoprotective activity of this substance was more active than that of other known cryoprotectants, like glycerol or serum.

Animals↗
PubMed1989

Hexagonal surface layer of Campylobacter fetus isolated from humans.

Electron microscopic studies of the surface structure of Campylobacter fetus by the freeze-etching method showed two different types of S layer. One was in a hexagonal array, and the other was in a tetragonal array. A high-passage-number strain lost its S layer during cultivation on culture media but regained it after a single animal passage.

Animals↗
PubMed1989

A cryptic fimbrial gene in Serratia marcescens.

The gene coding for the mannose-sensitive hemagglutinating fimbriae in Serratia marcescens US5 was cloned into Escherichia coli K4 with a cosmid vector system. One of the transformants, US5-1, expressed two morphologically distinct fimbriae, one that was 5-nm wide and one that was 3-nm wide. The latter fimbria was morphologically and serologically indistinguishable from that of strain US5. Genetic analysis of transformant US5-1 showed that the gene responsible for the 5-nm-wide fimbriae was located more than 10 kilobases away from the gene responsible for the 3-nm-wide fimbriae. The molecular sizes of the subunits of these two fimbriae, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were 19 kilodaltons for the 3-nm-wide fimbriae and 20 kilodaltons for the 5-nm-wide fimbriae. Serologically, the 5-nm-wide fimbriae did not cross-react with monoclonal or polyclonal antibodies raised against the mannose-sensitive hemagglutinating fimbriae of strain US5. Strain EL101, which expressed only the 5-nm-wide fimbriae, did not agglutinate chicken or human erythrocytes. These experimental results suggest that the gene for the 5-nm-wide fimbriae is cryptic in strain US5 and is expressed in E. coli K4 only after it is moved by transformation.

Amino Acid Sequence↗
PubMed1988

Generation of Listeria monocytogenes-specific T cells mediating delayed footpad reaction and protection in neonatally thymectomized mice but not in nude mice.

Neonatally thymectomized (NTx) mice, sham-operated control mice and congenitally athymic nude mice were immunized with viable Listeria monocytogenes and their spleen cells examined for the capacity to transfer both delayed footpad reaction and protection against challenge at the site of local transfer. Cells from immune NTx mice conferred significant degrees of delayed footpad reaction and protection comparable to sham mice, while cells from immune nude (nu/nu) mice did not. This ability was completely eliminated by the treatment of cells with anti-Thy1, anti-Lyt1 or anti-L3T4 antibody plus complement but not with anti-Lyt2 antibody plus complement. These results indicated that NTx mice can normally mount the immunity to L. monocytogenes by generating Lyt1+2-, L3T4+ T cells. Immune competence of NTx mice and thymus dependency of various immune responses are discussed.

Animals↗
PubMed1988

Purification and antigenic analysis of flagella of Campylobacter jejuni.

The flagella of Campylobacter jejuni strain FUM158432 were purified and a flagellin preparation consisting of only a single peptide of 63,000 daltons was obtained. The peptide of 92,000 daltons usually associated with a flagellar preparation was shown to be a peptide derived from the hook region. Antiserum was prepared by immunizing a rabbit with the flagellin preparation. The reaction of the antiserum was found to be highly specific for the flagellar filament by immunoelectron microscopy and for flagellin peptide by the immunoblotting method. Seventeen of 23 clinically isolated strains of C. jejuni reacted with this antiserum but the other six strains did not, indicating the existence of antigenic variation of the flagella of C. jejuni. The flagella of a few strains of C. coli also reacted with this antiserum.

Agglutination↗
PubMed1988

Fine structures of the capsules of Klebsiella pneumoniae and Escherichia coli K1.

The fine structures of the capsules of Klebsiella pneumoniae and Escherichia coli were determined by the rapid-freezing technique. The capsular layer was seen as a densely packed accumulation of fine fibers. The thickness of the capsule was approximately 160 nm in K. pneumoniae and less than 10 nm in E. coli K1. Two layers were observed in the Klebsiella capsule in which the arrangements of the fibers were different. The inner layer of the capsule was formed by a palisade of thick and dense bundles of the fibers standing at right angles on the surface of the outer membrane. In the outer layer these thick bundles of fibers loosened into fine fibers which spread over the bacterial surface, forming a fine network structure.

Antigens, Bacterial↗
PubMed1988

Cloning and sequence of the gene encoding the major structural component of mannose-resistant fimbriae of Serratia marcescens.

Serratia marcescens US46, a human urinary tract isolate, exhibits mannose-resistant hemagglutination and agglutinates yeast cells, thereby indicating that it has two types of adhesins. We constructed a cosmid library for the DNA of this organism and isolated DNA clones carrying genes for mannose-sensitive (MS) and mannose-resistant (MR) fimbriae. On introduction of the cloned genes into Escherichia coli K-12, MS and MR fimbriae were formed. These fimbriae were functionally and morphologically indistinguishable from those of S. marcescens. Subcloning of these gene clusters revealed that the genes encoding MS fimbriae reside on a 9-kilobase (kb) DNA fragment, while those encoding MR fimbriae are present on a 12-kb fragment. Transposon insertion and maxicell analyses revealed that formation of MR fimbriae is controlled by several genes which reside on the 9-kb fragment. The nucleotide sequence of smfA, the gene encoding the major structural component of MR fimbriae, revealed that this gene encodes a 174-amino-acid polypeptide with a typical procaryotic signal peptide. The primary structure of the smfA product showed significant homology with the primary structure of the E. coli fimbrial subunit.

Amino Acid Sequence↗