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Biomedical subjects

A Tamura

Publications and source records attributed to A Tamura.

At least 469 records · Page 26Linked to original sources
PubMed1984

Electron microscopic studies on intracellular multiplication of Rickettsia tsutsugamushi in L cells.

The mechanism and kinetics of intracellular growth of Rickettsia tsutsugamushi were investigated by electron microscopic observations, parallel with quantitative analysis by counting the rickettsiae seen in electron micrographs and by plaque assay for infectivity of the culture. The observations demonstrated the existence of electron-less dense and -dense types of rickettsiae in the early stage of infection, binary fission and the process of release of the microorganisms in the host cell cytoplasm and from the cell surface, formation of abnormally long rickettsiae, and the process of lysis of the host cell in the later stage of infection with vacuole formation between the inner and outer leaflets of the host cell nuclear membrane. Separate titrations of infectivity of the cells and the culture fluid showed a very slow increase in infectivity in the culture fluid compared with the intracellular titer, suggesting that the progeny rickettsiae stay in the cell or at the cell surface for a relatively long period. Doubling time of the rickettsia was found to be about 9 hr.

Animals↗
PubMed1984

Penicillin-insensitive incorporation of D-amino acids into cell wall peptidoglycan influences the amount of bound lipoprotein in Escherichia coli.

Certain D-amino acids, such as D-methionine and D-cystine, were incorporated into cells of Escherichia coli under conditions inhibiting protein and cell wall synthesis. Part of the radioactivity of D-14C-amino acids incorporated into the cells was found in the isolated cell wall peptidoglycan. A covalent linkage between the amino group of the D-amino acids and the peptidoglycan was presumed to be the main cause of the binding of the D-amino acids to peptidoglycan, because the amino group of the D-amino acids in the incorporation product was substituted. Whether the carboxyl terminus was substituted was unknown. The formation of the D-amino acid-peptidoglycan linkage was insensitive to beta-lactam antibiotics such as benzylpenicillin and ampicillin (500 micrograms/ml) and therefore was not due to the reaction of DD-transpeptidation which is involved in the biosynthesis of peptidoglycan. The D-amino acids also strongly inhibited the formation of peptidoglycan-bound lipoprotein in the E. coli cells. The results may suggest the correlation between binding of D-amino acid to peptidoglycan and inhibition of formation of the bound form of lipoprotein.

Amino Acids↗
PubMed1984

Structure-activity relationships on the terminal D-amino acid moiety of a novel cephamycin MT-141.

The effect of chemical modification of the D-amino acid function, which represents the C-7 beta substituent of cephamycin MT-141 on in vitro antibacterial activity was examined. MT-141 was more active on Gram-negative organisms than Gram-positive ones. It showed strong bacteriolytic activity on Gram-negative organisms. Lysis of Escherichia coli K-12 strain JE1011 treated with a low concentration of this antibiotic was preceded by frequent formation of multiple bulges from the cells. Amidation or decarboxylation, removing the acidic function from the D-amino acid of MT-141, resulted in an increase in activity against Gram-positive bacteria, and a decrease against Gram-negative ones. Cells treated with the amide or the decarboxylate did not form multiple bulges but formed single bulges. N-Acetylation of the D-amino acid moiety removing the basic function, caused a marked drop in activity against both Gram-positive and Gram-negative bacteria. The bacteriolytic activity on E. coli was reduced, and cells treated with the N-acetate became filamentous. Conversion of the D-amino acid function of MT-141 to the L configuration caused a moderate drop in activity against both Gram-positive and Gram-negative organisms. Both bacteriolytic and bactericidal activities against E. coli were reduced in the L-congener. Cefoxitin, cefmetazole and latamoxef used as reference antibiotics were less active than MT-141 in the bactericidal activity against E. coli, and induced single bulge formation or filamentation of the cells around MIC levels. Cell-surface permeability, stability to beta-lactamases, and binding affinity to PBPs of E. coli did not differ between MT-141 and its derivatives.

Bacteria↗
PubMed1984

Light scattering stopped-flow studies on the time course of shape changes induced in human erythrocytes by several amphiphilic lipids.

The light scattering stopped-flow method was used to study the time course of shape changes in human erythrocytes induced by two series of lipids (saturated and unsaturated free fatty acids and lysophosphatidylcholine (lysoPC) species, both with various acyl chain lengths (C12-C18] at pH 7.4 and 23 degrees C. The decrease in the scattered light intensity as a function of time suggested that these lipids induce crenation of erythrocytes, the rate constant of which is largely dependent on the nature of the respective lipids. For both series of lipids, an increase in chain length was found to decrease the rate of the induction of shape changes. The results were discussed in relation to hydrophobicity of lipid molecules.

Erythrocytes↗
PubMed1983

Effects of topical application of a calcium antagonist (nifedipine) on feline cortical pial microvasculature under normal conditions and in focal ischemia.

Cat cortical arterioles and venules were exposed in vivo to the Ca2+ antagonist nifedipine under normal conditions and in focal ischemia. Topical application of nifedipine caused a marked, concentration-dependent arteriolar dilatation. The dilatatory responses increased significantly with decreasing arteriolar size. Perivenular microapplication of nifedipine invariably caused dilatation that was less pronounced but more long-lasting than that on the arteriolar side. Arterioles, which constricted after middle cerebral artery occlusion, invariably dilated following nifedipine application. These dilatatory responses were transient but could be repeated, and on some occasions were accompanied by a return of flow in vessels in which stasis had been present. The results suggest that nifedipine is able to dilate cerebral vessels both under normal conditions and when contracted during focal ischemia.

Animals↗
PubMed1983

A double-blind clinical evaluation of the effect of Nizofenone (Y-9179) on delayed ischemic neurological deficits following aneurysmal rupture.

The effect of Nizofenone (Y-9179), a vertebral protective agent, on delayed ischemic neurological deficits following subarachnoid hemorrhage (SAH) due to aneurysmal rupture was investigated by a cooperative double-blind clinical trials. Delayed ischemic neurological deficits following SAH are closely associated with the occurrence of vasospasm, and the effectiveness of any cerebral protective agent depends on sufficient coverage by the drug over the period around the onset of ischemic insult. Therefore, the study was designed so that the effect of Nizofenone could be analyzed in terms of these two factors. In patients admitted within day 9 of SAH, drug administration was immediately initiated and continued for 5 days. When delayed ischemic neurological deficits occurred, angiography was carried out to confirm the presence of vasospasm, and then drug administration was extended for an additional 5 days. Ten of the 100 cases enlisted in the study were excluded prior to code-breaking because of the occurrence of severe complications not related to vasospasm. Out of the 42 cases of the Nizofenone group and 48 of the placebo group, 25 and 29 developed vasospasm, respectively. Thus Nizofenone did not prevent vasospasm. Of the 25 cases of the Nizofenone group with vasospasm, 13 cases received sufficient drug coverage around the onset of vasospasm. The placebo group, the total Nizofenone group, and the Nizofenone group with sufficient drug coverage were stratified according to the occurrence of vasospasm. The disability status index one month after admission and the neurological functions, such as motor and speech functions, of each group were then compared. In patients who developed vasospasm, only the Nizofenone group with sufficient drug coverage had a significantly better outcome than the placebo group (p less than 0.05). No particular side effect of Nizofenone was observed. Thus, the results indicate that Nizofenone may be useful in the therapy of delayed ischemic neurological deficits following SAH, although the effect of the drug may be considerably influenced by the timing of its administration.

Adult↗
PubMed1983

Penetration of Rickettsia tsutsugamushi into cultured mouse fibroblasts (L cells): an electron microscopic observation.

The mechanism of penetration of purified Rickettsia tsutsugamushi (Gilliam strain) into cultured mouse fibroblasts (L cells) was examined by electron microscopy. After 10-40 min of infection, rickettsiae in the process of being phagocytized were often seen on the cell surface. These were restricted to the rickettsiae which seemed to be intact in morphology, while heavy plasmolyzed ones were never phagocytized. Additionally, rickettsiae were taken up individually into a phagosome, and phagocytosis of several rickettsiae together was rarely observed, except in the case of heat-inactivated microorganisms. In the cells, phagosomes whose membranes enclosed rickettsiae either tightly or loosely were seen. Rickettsiae in the loose phagosomes often showed signs of plasmolysis and were rarely released into the cell cytoplasm. Partial disintegration of phagosomal membranes and the escape of rickettsiae from the phagosomes were seen only in tight phagosomes. Large phagosomes containing a clump of several rickettsiae were observed occasionally, in which case the microorganisms were deformed and seemed to be denatured. From the above observations and the frequency of appearance of these different penetration stages in the specimens 10, 20, and 40 min after infection, it was concluded that the rickettsiae enter initially into a tight phagosome by phagocytosis and are then released into the cell cytoplasm by disruption of the phagosomal membrane. No other mechanisms of penetration were found. On the other hand, rickettsiae inactivated by trypsin did not attach to host cells. Inactivation by heat or UV irradiation resulted in reduction of phagocytosis, and rickettsiae treated with rifamycin could penetrate into the host cell cytoplasm to the same extent as in the case of infection with intact rickettsiae.

Animals↗
PubMed1983

Lipid composition of winged bean (Psophocarpus tetragonolobus).

The lipids were extracted from the winged bean (Psophocarpus tetragonolobus) seed with water-saturated n-butanol. Lipids were separated into groups by preparative TLC on silica gel G. The amount of each lipid type was determined by analysis of the fatty acid constituents in each lipid type. Glyceride was the major lipid accounting for 89.6% of the total, followed by an unknown lipid 4%, free fatty acid of 2.3%, 1,3-diglyceride, 1,2-diglyceride and steryl ester as 1% each and finally a polar lipid as 0.2%. The results show that winged bean oil should be suitable for edible purposes. Triglycerides showed a similar profile of fatty acids to those of whole lipid: the major fatty acids were palmitic (10.9%), stearic (4.5%), oleic (37.1%), linoleic (19.0%), eicosenoic (3.6%), behenic (18.5%) and lignoceric (4.2%) acids. Compared to soybean oil, winged bean oil contained long chain fatty acids and a fairly small amount of linolenic acid which is favorable regarding oil stability against autoxidation.

Chemical Phenomena↗
PubMed1983

Effects of insulin, dexamethasone and phorbol ester on virus production in cultivated DBA/2 mouse leukemia (MLA) cells.

The in vitro production of intracytoplasmic oncovirus A-particles and of atypical mammary tumor virus (MLAV) from a line of DBA/2 mouse leukemia (MLA) cells were compared in the presence of insulin, dexamethasone and 12-0-tetradecanoyl-phorbol-13-acetate (TPA), which are known to stimulate the synthesis of mouse mammary tumor virus. High amounts of A-particles were recovered from cells cultivated in the presence of dexamethasone (1 microgram/ml) as compared to untreated controls; in contrast, the production of MLAV was suppressed. Insulin and TPA did not show any significant effects.

Animals↗