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Biomedical subjects

A Tamura

Publications and source records attributed to A Tamura.

At least 433 records · Page 24Linked to original sources
PubMed1986

Effect of fatty acyl chain length of phosphatidylcholine on their transfer from liposomes to erythrocytes and transverse diffusion in the membranes inferred by TEMPO-phosphatidylcholine spin probes.

TEMPO-phosphatidylcholine (PC) spin probes which have homologous saturated acyl chains of 10, 12, 14 and 16 carbon atoms, were synthesized as analogues of PC. Transfer of TEMPO-PCs from liposomal membrane to the ghost membrane of human erythrocyte and transverse diffusion of TEMPO-PCs within the membrane of intact erythrocytes were determined by measurement of spontaneous increase and decrease in signal amplitude of an anisotropic triplet spectrum, due to dilution of the label by natural phospholipid of the membrane and reduction of the label by the cytoplasmic content of the erythrocyte, respectively. TEMPO-PC molecules in TEMPO-PC liposomes, except dipalmitoyl TEMPO-PC, were rapidly incorporated into the ghost membrane by incubation at 37 degrees C; the PC having shorter acyl chains was transferred faster. The cytoplasmic content of the erythrocyte rapidly reduced the nitroxide radical of the spin probe. The central peak height of ESR signal was once increased by incorporation of TEMPO-PC into the erythrocyte membrane and then was spontaneously decreased during further incubation at 37 degrees C. This decrease indicates that PC molecules traverse from the outer to the inner layer of the membrane lipid bilayer. The decrease of signal amplitude was faster with PC of shorter acyl chain. These findings suggest that both transfer between membranes and transverse diffusion in the membrane may be favored to the PC species with shorter acyl chains.

Cyclic N-Oxides↗
PubMed1986

Production and characterization of monoclonal strain-specific antibodies against prototype strains of Rickettsia tsutsugamushi.

We have developed 18 hybridoma cell lines which secrete murine monoclonal strain-specific antibodies to prototype strains of Rickettsia tsutsugamushi: nine anti-Gilliam, four anti-Karp and five anti-Kato antibodies. All the monoclonal antibodies reacted only with their homologous strains in direct and indirect immunofluorescence (IF), or indirect immunoperoxidase (IP) test. By IF and IP tests with the monoclonal antibodies, 22 strains of R. tsutsugamushi, which were newly isolated from mites, field rodents and patients with Tsutsugamushi disease (scrub typhus) in Japan, were all clearly identified as either Gilliam or Karp type. Analysis by polyacrylamide gel electrophoresis and immunoblotting techniques revealed that the monoclonal antibodies recognized primarily the polypeptides of an apparent molecular weight of 54 to 56 kilodaltons of the homologous rickettsial surface. The monoclonal antibodies produced in the present study should enhance the serotyping and further analytical investigation of the rickettsial antigens since they recognize the strain- or type-specific polypeptides and do not show any cross-reaction among strains.

Animals↗
PubMed1986

Immunological properties of Rickettsia tsutsugamushi, Kawasaki strain, isolated from a patient in Kyushu.

Nine isolates of Rickettsia tsutsugamushi were obtained from patients with Tsutsugamushi disease (scrub typhus) in Miyazaki Prefecture in Kyushu. Immunological analyses of these patients' sera and the isolates were performed by indirect immunofluorescence, indirect immunoperoxidase or immunoblotting techniques. In the analysis of reactions of the patients' sera with the prototype strains Gilliam, Karp, and Kato and with the isolates, sera from two patients, including Kawasaki, showed similar profiles and cross-reaction with the two isolates recovered from the corresponding patients, but reacted only weakly with the prototype strains. With guinea pig polyclonal antibodies against the isolate and prototype strains, Kawasaki strain showed some degree of cross-reaction with Gilliam strain but not with either Karp or Kato strain, nor with Shimokoshi strain which is known to be different antigenically from the prototype strains. Additionally, strain-specific murine monoclonal antibodies against Gilliam, Karp, and Kato strains did not react at all with Kawasaki strain. These results suggest that the Kawasaki strain may be different antigenically from the prototype strains and Shimokoshi strain. The finding two strains of the same antigenic type (Kawasaki) among only nine isolates suggests the presence of Kawasaki-type rickettsiae in Miyazaki Prefecture. Shimokoshi strain also did not react with these strain-specific monoclonal antibodies, suggesting that strains of R. tsutsugamushi antigenically distinct from the prototype strains, such as Kawasaki and Shimokoshi strains, may easily be recognized by their nonreactivity with these monoclonal antibodies.

Animals↗
PubMed1986

Changes of uric acid level in rat brain after focal ischemia.

Changes of uric acid level in rat cerebral hemisphere after left middle cerebral artery (MCA) occlusion were studied by reversed-phase HPLC with electrochemical detection. Uric acid level in the normal group was 2.98 nmol/g tissue. Uric acid concentration of the left hemisphere in the left MCA-occluded group progressively increased after occlusion, and reached a maximum value of 67.26 nmol/g tissue 24 h after ischemia. Uric acid levels in the right hemisphere remained unchanged. Uric acid concentration of the left hemisphere in sham-operated group was 9.29 nmol/g tissue 24 h after the operation.

Animals↗
PubMed1986

Characterization of polypeptides in Rickettsia tsutsugamushi: effect of preparative conditions on migration of polypeptides in polyacrylamide gel electrophoresis.

The polypeptide compositions and antigenic components of Rickettsia tsutsugamushi were analyzed by modifying the solubilization conditions prior to polyacrylamide gel electrophoresis and by using monoclonal antibodies in immunoblotting experiments. Several polypeptides were converted to larger or smaller molecules by using various conditions for rickettsial sample preparation. Solubilization of a sample in 2-mercaptoethanol-containing buffer resulted in conversion of high-molecular-weight polypeptides to smaller polypeptides and conversion of some of the 43-kilodalton (43K) polypeptide to a 46K polypeptide. The heat modifiability of selected polypeptides was shown by heating samples at 100 degrees C. A major polypeptide on the rickettsial surface which showed strain-specific antigenicity appeared at the 43K position in samples solubilized at 37 degrees C but moved to the 56K position after samples were heated at 100 degrees C. Immunoblotting with an anti-56K polypeptide monoclonal antibody demonstrated that the reactive antigens existed predominantly as the higher-molecular-weight polypeptides. These polypeptides were converted to 43K polypeptides at 37 degrees C or the 56K polypeptides at 100 degrees C by cleavage of disulfide linkages with 2-mercaptoethanol treatment.

Antigens, Bacterial↗
PubMed1986

In vitro evaluation of SF-2103A, a novel carbapenem antibiotic, as a beta-lactamase inhibitor.

SF-2103A, a new carbapenem antibiotic, exhibited a broad antibacterial spectrum and a potent inhibitory activity against a wide range of beta-lactamases, in particular, against cephalosporinases, with lower I50 values than those displayed by sulbactam and clavulanic acid. Using a fixed combination and checkerboard titration, in vitro synergy against the majority of the beta-lactamase-producing strains tested was demonstrated between SF-2103A and various beta-lactam antibiotics, especially cefotaxime, ceftizoxime, and cefoperazone. The synergistic effect of SF-2103A was more pronounced than that of sulbactam. The in vitro synergy was also confirmed by bactericidal and bacteriolytic activities and morphological effects.

Anti-Bacterial Agents↗
PubMed1986

Effect of exogenous lipids incorporated into the membrane of human erythrocytes on its glucose transport activity.

Addition of a phosphatidylcholine (dilinoleoyl), lysophosphatidylcholine (palmitoyl), saturated or unsaturated long-chain fatty acid (stearic or oleic) into human erythrocyte suspension caused both dose-dependent incorporation of the lipid into the membrane and inhibition of the glucose transport across the membrane. Loading to or partial removal of cholesterol from the membrane increased or decreased the transport rate, respectively. There was no correlation between the changes in the transport activity and those in cell shape caused by such alterations in the membrane lipid composition.

Blood Glucose↗
PubMed1986

[Focal cerebral infarction in the rat: I. Operative technique and physiological monitorings for chronic model].

The purpose of this paper is to develop a new chronic model of focal cerebral infarction by occluding the middle cerebral artery (MCA) in the rat. The operative method and results of physiological monitoring before, during, and after operation are shown. In adult male Sprague-Dawley rats, the left MCA was occluded via trans-retro-orbital approach simply by retracting the temporalis muscle. This method was slightly modified from our original method for chronic experiments. In a group of rats, systemic arterial pressure and blood gases were monitored using a femoral arterial catheter before, during, and after the operation. In the other group, blood pressure by tail-cuff method, neurological findings, and body weight were examined for one week after the MCA occlusion. During the operation under the halothane anesthesia, systemic arterial pressure decreased about 30% comparing with preanesthetic normal value and then quickly returned to normal within 30 minutes after the operation. Body weight progressively decreased in the occluded group during the observation period of one week, although body weight in the sham-operated group decreased only for initial few days and recovered. No animal died during first one week. Slight right hemiparesis was observed only in the MCA occluded group for few days.

Animals↗
PubMed1986

[Focal cerebral infarction in the rat: II. Neuropathological study and local cerebral blood flow pattern].

We have recently reported that middle cerebral artery (MCA) occlusion in the rat produces a uniform pattern of cerebral ischemia in an acute phase. This study was done to determine if this model is also useful for quantitative evaluation of infarction size in a chronic phase. [Methods] Sprague-Dawley rats were anesthetized with halothane and left MCA was occluded via transretro-orbital approach. The following studies were done. Neuropathological study was done one week after MCA occlusion. After perfusion fixation, the brain was cut into 6 coronal slices and stained sections were examined. Local cerebral blood flow patterns were observed by 14C-iodoantipyrine autoradiographic technique 1, 2, and 5 days after the occlusion. [Results] Neuropathological studies invariably showed infarct in the cortex and the lateral part of the basal ganlia. The ratio of the infarct to the total areas of both hemispheres in 6 coronal sections was 14.05 +/- 2.66% (Mean +/- SD) in MCA occluded animals (N = 14) and 0.59 +/- 0.46% in sham operated animals (N = 12). Relative to the contralateral hemisphere, marked reduction in CBF was seen in the territory of the MCA and moderate reductions were also seen in the surrounding areas. The same pattern of increased CBF as previously reported was also seen in the ipsilateral substantia nigra and globus pallidus 1, 2, and 5 days after the occlusion. These results indicate the usefulness of this chronic focal cerebral infarction model in the evaluation of infarction.

Animals↗
PubMed1986

[Treatable ischemic neuronal damage in the gerbil hippocampus].

The Mongolian gerbil is known to develop delayed neuronal death in the hippocampus following brief forebrain ischemia (Brain Res 239: 57-69). Morphological, biochemical, or electrophysiological studies on this neuronal injury have shown that neurons still retain potential reversibility at the earlier period of alteration. To examine this possibility, immediately following 5 min of ischemia in the gerbil, pentobarbital, diazepam, or nizofenone was injected. Seven days following ischemic insult, animals were perfusion fixed and neuronal density in the hippocampal CA1 subfield was counted. Most of the neurons in the CA1 sector survived ischemic insult when a drug was given, whereas most of them were lost without the treatment. The average neuronal density of treated groups showed a statistically significant (p less than 0.01) persistence compared with that of control group. The effective dosage of the drugs were 20-40 mg/kg in pentobarbital, 10-20 mg/kg in diazepam, and 12.5-25 mg/kg in nizofenone. On the other hand, when pentobarbital was injected 1 hr following ischemia, while neurons still remain intact morphologically, it showed no effect. This result indicates that the neuronal damage of "delayed neuronal death" type is reversible if treatment is instituted at an early period of cell change.

Animals↗
PubMed1985

Second lytic target of beta-lactam compounds that have a terminal D-amino acid residue.

A new biochemical mechanism of lysing bacterial cells by treatment with certain beta-lactam compounds that possess a terminal D-amino acid moiety in their side chain was demonstrated. The two functions of the molecule, the beta-lactam and terminal D-amino acid moiety, are both involved in the activity of lysing gram-negative bacteria, which is characterized by very rapid lysis of the cells in the first few hours after their contact with the compound. This mechanism was proved by studies on one such compound, named MT-141, which contains a terminal D-cysteine moiety with free amino and carboxyl groups in the 7 beta-side chain of the 7 alpha-methoxy-cephalosporin skeleton. This compound bound to the cell-wall peptidoglycan of Escherichia coli through the D-amino group of its terminal D-amino acid moiety and this seemed to cause rapid cell lysis. Both activities, of binding to peptidoglycan and of causing rapid cell lysis, were inhibited by certain D-amino acids, but not by L-amino acids. Mutants were isolated that had simultaneously gained decreased sensitivity to this kind of beta-lactam compound and supersensitivity to globomycin, an inhibitor of formation of lipoproteins which function in linking the peptidoglycan to the outer membrane. These results suggest that binding of the terminal D-amino acid moiety of the beta-lactam compound to peptidoglycan somehow influences formation of the linkage between the outer membrane and the peptidoglycan and consequently enhances the cell lytic activity of the beta-lactam portion of the molecule.

Amino Acid Sequence↗
PubMed1985

In-vitro and in-vivo activities of a novel cephamycin MT-141 against the Bacteroides fragilis group in comparison with six cephem antibiotics.

MT-141 inhibited 90% of the clinical isolates of Bacteroides fragilis at 3.13 mg/l, whereas six reference cephem antibiotics inhibited them at 12.5- greater than 100 mg/l. MT-141 was stable to the Bacteroides beta-lactamases, but the stability alone could not explain the potent activity of MT-141 against the other Bacteroides spp., which produced only small amounts of beta-lactamase, but were resistant to other cephem antibiotics. MT-141 exhibited a higher killing rate and more potent in-vivo efficacy than the reference cephem antibiotics against Bact. fragilis No. 36 combined with Escherichia coli No. 29. In conclusion, the in-vitro and in-vivo anti-bacteroides activities of MT-141 ranked first among those of the cephem antibiotics compared.

Animals↗
PubMed1985

Quantitative studies on translocation and metabolic conversion of lysophosphatidylcholine incorporated into the membrane of intact human erythrocytes from the medium.

The fate of palmitoyl-lysophosphatidylcholine (lysoPC) incorporated into the membrane of intact human erythrocytes from a medium was investigated under nonhemolytic conditions at 37 degrees C by means of 14C-labeled tracers. The lysoPC was first incorporated into the outer half of the membrane lipid bilayer and then gradually translocated into the inner half during the incubation. At the same time it was metabolically converted into phosphatidylcholine (PC) and free fatty acid (FFA) plus glycerophosphorylcholine by the actions of acyltransferase and lysophospholipase, respectively. The half times of the conversion were about 14 h, while the value of 0.5 h was obtained when the half time was measured with the hemolysate of the lysoPC-loaded erythrocytes. Chymotrypsin treatment of unsealed ghosts caused a definite decrease in lysophospholipase activity, while similar treatment of resealed ghosts did not. This together with other evidence already reported in the literature suggests that both lysophospholipase and acyltransferase may be located in the inner surface of the membrane. The above findings strongly suggest that the most of the lysoPC loaded to the membrane is gradually translocated from the outer to the inner half of the bilayer and soon converted to either PC or FFA.

Acyltransferases↗