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Biomedical subjects

T Hashizume

Publications and source records attributed to T Hashizume.

At least 181 records · Page 10Linked to original sources
PubMed1988

Cytochrome P-450 in human liver microsomes: high-performance liquid chromatographic isolation of three forms and their characterization.

Three forms of cytochrome P-450, designated as P-450-HM1, P-450-HM2, and P-450-HM3, were isolated from human liver microsomes using high-performance liquid chromatography (HPLC) techniques. Each purified preparation showed a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). From the results of SDS-PAGE, the molecular weights of P-450-HM1, P-450-HM2, and P-450-HM3 were estimated to be 51,000, 54,000, and 52,000, respectively. The oxidized absolute spectra of these three forms of cytochrome P-450 showed Soret absorption peaks at around 417 nm, indicating that these forms were in the low spin state. In a reconstituted system, P-450-HM1 showed the highest catalytic activities of nifedipine and (S)- or (R)-nilvadipine oxidases. The same form showed higher activities of testosterone 6 beta-hydroxylase and progesterone 6 beta- and 16 alpha-hydroxylases. P-450-HM2 showed high N-demethylase activities for benz-phetamine and aminopyrine, and also showed the highest activity of testosterone 16 beta-hydroxylase among the three forms, while it did not show detectable activities of testosterone 6 beta-hydroxylase and progesterone 6 beta- and 16 alpha-hydroxylases. Anti-P-450-HM1 immunoglobulin G (IgG), but not anti-P-450-HM2 IgG, inhibited the activities of testosterone 6 beta-hydroxylase and nifedipine and nilvadipine oxidases in human liver microsomes. Anti-P-450-HM1 IgG was also inhibitory against progesterone 6 beta- and 16 alpha-hydroxylases.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Molecular cloning of the penicillin G acylase gene from Arthrobacter viscosus.

Penicillin G acylase was purified from the cultured filtrate of Arthrobacter viscosus 8895GU and was found to consist of two distinct subunits with apparent molecular weights of 24,000 (alpha) and 60,000 (beta). The partial N-terminal amino acid sequences of the alpha and beta subunits were determined with a protein gas phase sequencer, and a 29-base oligonucleotide corresponding to the partial amino acid sequence of the alpha subunit was synthesized. An Escherichia coli transformant having the penicillin G acylase gene was isolated from an A. viscosus gene library by hybridization with the 29-base probe. The resulting positive clone was further screened by the Serratia marcescens overlay technique. E. coli carrying a plasmid designated pHYM-1 was found to produce penicillin G acylase in the cells. This plasmid had an 8.0-kilobase pair DNA fragment inserted in the EcoRI site of pACYC184.

Amidohydrolases↗
PubMed1988

Mode of action of BO-1341: transport pathway through the outer membrane of Escherichia coli.

BO-1341, a new semisynthetic cephalosporin having a 6,7-dihydroxyisoquinolinium moiety at the C-3 methylene, possesses potent antibacterial activity against Gram-negative bacteria including glucose-nonfermentative bacteria, especially Pseudomonas aeruginosa. In order to elucidate the mechanisms of action, the transport pathway of BO-1341 through the outer membrane of Escherichia coli was studied. The antibacterial activity of BO-1341 was not affected by the deficiency in OmpF and OmpC porin channels compared with its wild-type strain, but was affected by the iron concentration in the medium. Susceptibility testing with the mutants involved in the iron transport system indicated that the tonB mutant was resistant to BO-1341. Analysis of the spontaneous mutants resistant to BO-1341 revealed a mutation in the tonB gene. The strong activity of BO-1341 and the lack of cross-resistance to other cephalosporins may be attributable to the unique transport system through the outer membrane of Gram-negative bacteria.

Anti-Bacterial Agents↗
PubMed1987

Inhibition of platelet aggregation by unsaturated fatty acids through interference with a thromboxane-mediated process.

cis- and trans-unsaturated fatty acids with 18 carbon atoms (oleic, linoleic, elaidic and linolelaidic acid) inhibited aggregation of washed rabbit platelets stimulated with collagen, arachidonic acid and U46619 when in the same concentration ranges. Thrombin-induced aggregation was not affected by any of them. Saturated fatty acid (stearic acid) had no effect on this response. The inhibition is independent of the induced change in membrane fluidity, since trans-isomers could not induce the change in fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. Unsaturated fatty acids, except linoleic acid, did not interfere with the formation of thromboxane B2 from exogenously added arachidonic acid. All the unsaturated fatty acids only slightly inhibited the arachidonic acid liberation by phospholipase A2 in platelet lysate. This indicates that the unsaturated fatty acids may block a process after formation of thromboxane A2 in response to collagen and arachidonic acid. The increase in phosphatidic acid formation stimulated with U46619 was inhibited dose dependently by each of the unsaturated fatty acids but that stimulated with thrombin was not affected by any of them. Phospholipase C activity measured by diacylglycerol formation in unstimulated platelet lysate was not inhibited by the fatty acids. The elevation of cytosolic free Ca2+ induced by arachidonic acid or U46619 and Ca2+ influx by collagen were inhibited almost completely at the same concentration as that which inhibited their aggregation. These data suggest that the unsaturated fatty acids were intercalated into the membrane and inhibited collagen- and arachidonic acid-induced platelet aggregation by causing a significant suppression of the thromboxane A2-mediated increase in cytosolic free Ca2+, probably due to interference with the receptor-operated Ca2+ channel.

Animals↗
PubMed1987

N-ethylmaleimide inhibits Ca2+ influx induced by collagen or arachidonate on rabbit platelets.

N-Ethylmaleimide dose dependently inhibited platelet aggregation induced by collagen or arachidonate but did not inhibit the aggregation by thrombin or ionophore A23187 within the concentrations tested. [3H]Arachidonate release from membrane phospholipids of the collagen-stimulated platelets was inhibited by N-ethylmaleimide in parallel with the inhibition of aggregation, but not in response to A23187. N-Ethylmaleimide prevented 45Ca2+ influx into platelet cells from outer medium induced by collagen, and also inhibited the increase in the concentration of cytoplasmic free Ca2+, which probably results from Ca2+ influx, as monitored by quin2 fluorescence, under stimulation with arachidonate. The concentration of N-ethylmaleimide giving a complete inhibition of Ca2+ influx was consistent with that required to inhibit collagen- or arachidonate-induced aggregation. Prostaglandin metabolism from arachidonate to thromboxane A2 was not disturbed by N-ethylmaleimide, while phosphatidate formation induced by arachidonate was slightly inhibited by it at concentrations at which aggregation was completely inhibited. These data suggest that N-ethylmaleimide preferentially suppresses increase in cytoplasmic free Ca2+ which is linked to thromboxane A2-receptor occupation in collagen- or arachidonate-stimulated platelets, probably due to blockage of Ca2+ influx through Ca2+-channel protein, thereby inhibiting aggregation induced by these agonists.

Animals↗
PubMed1987

Structure determination of a new fluorescent tricyclic nucleoside from archaebacterial tRNA.

A highly fluorescent nucleoside was detected in enzymatic digests of the extremely thermophilic archaebacterium Sulfolobus solfataricus by combined liquid chromatography-mass spectrometry (LC/MS). Following isolation, the structure was determined primarily by mass spectrometry, to be 3-(beta-D-ribofuranosyl)-4,9-dihydro-4,6,7-trimethyl-9-oxoimidazo[ 1, 2-a]purine (mimG), a new derivative of the Y (wye) nucleoside. The structural assignment was verified by comparison of the base released by acid hydrolysis with the corresponding synthetic base, using mass spectrometry, chromatography, and UV absorption and fluorescence properties. Nucleoside mimG was also detected by LC/MS in hydrolysates of the thermophiles Thermoproteus neutrophilus and Pyrodictium occultum. These results constitute the first finding of a member of the hypermodified Y family of nucleosides in archaebacteria.

Archaea↗
PubMed1987

Penetration of imipenem and other antibiotics into inflammatory exudate and their efficacy in pseudomonas infection in the rat granuloma pouch model.

The rat granuloma pouch model was used to study the penetration of imipenem into inflammatory exudate and its efficacy in an experimental local infection. Rats were given a single intravenous injection of drug via the tail vein at a dose of 40 mg/kg. The peak concentrations of imipenem, ceftizoxime, cefazolin, and cefsulodin in exudates ranged from 10.1 to 12.3 mg/l, except that ampicillin achieved only 5.4 mg/l. Imipenem rapidly reached peak concentration after injection, but the half life for elimination of imipenem from exudate was 77.7 min, which was shorter than that of other beta-lactam antibiotics. Imipenem exhibited more rapid reduction in bacterial growth than cefsulodin in an experimental local infection with Pseudomonas aeruginosa in the pouch model. The results suggested that imipenem was an effective agent in treating the local infection.

Animals↗
PubMed1987

Therapeutic effects of imipenem-cilastatin on experimental intrauterine infections in rats.

The therapeutic effects of imipenem-cilastatin (MK-0787-MK-791) on experimental intrauterine infections in progesterone-treated virgin rats and postpartum rats were studied. The relative efficacy of imipenem-cilastatin for the treatment of such intrauterine infections was compared with that of cefazolin and ampicillin for the treatment of infections caused by Escherichia coli and Streptococcus faecalis, respectively. Treatment with imipenem-cilastatin significantly inhibited the proliferation of E. coli and S. faecalis in uteri, as compared with the proliferation in untreated controls. Cefazolin failed to affect the E. coli infection. With the S. faecalis infection, ampicillin effectively reduced bacterial growth, as compared with that in untreated controls. However, ampicillin was inferior to and comparable to imipenem-cilastatin in progesterone-treated virgin rats and postpartum rats, respectively. A further experiment with S. faecalis infections in rats made neutropenic by intraperitoneal injection of cyclophosphamide showed that the therapeutic effectiveness of imipenem-cilastatin was superior to that of ampicillin and was not influenced by neutropenia. Our results suggest that imipenem-cilastatin may be a useful agent for the treatment of obstetric and gynecologic infections.

Ampicillin↗
PubMed1987

[Pulmonary resection by microwave tissue coagulator (MTC)--clinical application].

A 55 year old male with metastatic lung and liver cancer was subjected to pulmonary and hepatic resections using Microwave Tissue Coagulator (MTC). No adverse effects were observed in this patient after operation. The resected specimen of the lung had the bronchioli partially accompanied with cartilages. Coagulation for the bronchioli of at least lmm in size, by MTC, could be carried out resulting in no air leakage after operation.

Adenocarcinoma↗
PubMed1986

Specific diagnosis of hepatocellular carcinoma by delayed hepatobiliary imaging.

For assessment of the value of delayed hepatobiliary imaging with technetium 99m (99mTc)-(Sn)-N-pyridoxyl-5-methyltryptophan (99mTc-PMT) for specific diagnosis of hepatocellular carcinoma, 88 patients with various malignant and benign liver diseases (49 with hepatocellular carcinoma, 4 with cholangiocellular carcinoma, 10 with metastatic liver carcinoma, 2 with liver cysts, 2 with liver hemangioma, 1 with liver abscess, 2 with intrahepatic lithiasis, 12 with liver cirrhosis, and 6 with chronic hepatitis) were studied. In 20 (41%) of the 49 patients with hepatocellular carcinoma, greater uptake of 99mTc-PMT by the tumor than by the surrounding liver tissue was seen in delayed hepatobiliary images, whereas in eight patients (16%), equilibrated uptake was seen. No increased uptake of the radioisotope by hepatic lesions was seen in 21 patients with localized liver diseases other than hepatoma. Moreover, in 18 patients with diffuse liver diseases, no focal accumulation of the radioisotope was seen in delayed 99mTc-PMT images. In addition, of 28 patients with hepatocellular carcinoma in whom the serum alpha-fetoprotein level showed little or no increase, 12 showed increased uptake of 99mTc-PMT by the tumor. In assessing delayed 99mTc-PMT images, however, it was necessary to consider following complications: accumulation of tracer in obstructed and dilated biliary trees; retention of radioactivity in nonneoplastic liver tissues; difficulties in evaluating 99mTc-PMT uptake by small hepatic tumors; overlapping of radioactivity in the gut and gallbladder in delayed 99mTc-PMT images of tumors. This study indicates that delayed 99mTc-PMT images can be useful in the diagnosis of hepatocellular carcinoma.

Aged↗
PubMed1985

Concentration of 99mTc-Sn-N-pyridoxyl-5-methyltryptophan, a biliary agent, in distant metastases of hepatomas.

During the last 2 years, eight patients with hepatocellular carcinoma who were suspected of having distant metastases have been studied to determine whether a new biliary agent, 99mTc-Sn-N-pyridoxyl-5-methyltryptophan (99mTc-PMT), is taken up by extrahepatic tumors. In all eight patients, scintigrams showed a clearly increased uptake of 99mTc-PMT radioactivity by the extrahepatic tumors. In contrast, an increased uptake by the tumors of gallium citrate Ga 67 was only detected in four of the seven patients examined. The results obtained in this study suggest that 99mTc-PMT is useful both for characterizing the nature of extrahepatic tumors in patients with hepatoma and for detecting the metastases.

Adult↗