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T Shimada

Publications and source records attributed to T Shimada.

At least 865 records · Page 48Linked to original sources
PubMed1986

Sodium-independent, hydrogen ion-dependent changes in membrane potential and conductance induced by dipeptides in Triturus enterocytes.

The effects of Na+ and pH in the medium on dipeptide transport across Triturus small intestinal brush border membrane were studied electrophysiologically. Although glycylglycine exists mainly in the zwitterionic form at pH 7.30, it induced marked depolarization in the membrane potential and reduction in the input resistance both in the presence and absence of Na+ in the medium. Similar Na+-independent depolarization and resistance change were also observed with L-carnosine. On the contrary, glycine induced membrane depolarization and reduction in the input resistance only in the presence of Na+ in the medium. When pH of the medium was lowered to 6.00, the magnitude of the depolarization induced by glycylglycine increased by 33%, while at pH 8.30, it decreased by 39%. These data indicate that dipeptide transport across the intestinal brush border membrane is coupled with H+ and has no direct interaction with Na+.

Animals↗
PubMed1986

Human-liver cytochromes P-450 involved in polymorphisms of drug oxidation.

Nine forms of cytochrome P-450 have been purified to electrophoretic homogeneity from human-liver microsomes. These include the enzymes involved in debrisoquine 4-hydroxylation, phenacetin O-deethylation and mephenytoin 4-hydroxylation, three reactions which are characterized by genetic polymorphism in humans. Evidence for the involvement of the above enzymes comes from reconstituted immunochemical inhibition studies with human-liver microsomes. These and other lines of evidence are consonant with the view that different forms of cytochrome P-450 are involved in the three reactions. The debrisoquine 4-hydroxylase has been studied most extensively in terms of its substrate specificity. In addition, an analogous rat enzyme shows some homology and serves as a useful model. The use of antibodies raised to the rat-liver enzyme in immuno-inhibition studies with human-liver microsomes provides a means of determining the extent to which this enzyme participates in other reactions. Translation of rat-liver mRNA in vitro yields the intact debrisoquine 4-hydroxylase; studies with human mRNA suggest a lower frequency than in rats. The basis for impaired catalytic activity in phenotypically poor human metabolizers appears to be an altered enzyme in all three cases, as opposed to a decreased level of a single enzyme. Using antibody screening of fusion proteins expressed in a cDNA library, it has been possible to isolate cDNA probes for all three of these cytochromes P-450 for use in screening individuals and ultimately determining the basis of these polymorphisms.

Binding Sites↗
PubMed1986

[Bacterial and clinical studies on imipenem/cilastatin sodium in urological infection].

Antibacterial activities of imipenem (MK-0787), cefazolin (CEZ), cefmenoxime (CMX) and cefoperazone (CPZ) were measured by using an agar dilution method against 243 strains of bacteria isolated from the patients with urinary tract infections. The MIC80 of MK-0787 against S. epidermidis, E. faecalis, E. coli, K. pneumoniae, E. cloacae, S. marcescens, P. mirabilis, P. vulgaris and P. aeruginosa was less than or equal to 0.10, 3.13, less than or equal to 0.10, 0.20, 0.78, 1.56, 3.13, 3.13 and 6.25 micrograms/ml, respectively. MK-0787 was more active than CEZ, CMX and CPZ against all bacterial species except Proteus spp. Imipenem/cilastatin sodium (MK-0787/MK-0791) 500 mg/500 mg two times a day for 5 days was given to 31 cases of chronic complicated urinary tract infections and a case of acute prostatitis. Overall clinical effectiveness rate judged by the criteria proposed by the Japanese UTI committee in 22 cases of chronic complicated urinary tract infection treated with MK-0787/MK-0791 was evaluated to be 86% including excellent in 6 cases, moderate in 13 cases and poor in 3 cases. As side effects, 2 cases encountered eruption or anorexia. Abnormal laboratory findings were observed in 6 cases.

Adult↗
PubMed1986

[Two cases of thrombosis of an aneurysm in the acute stage].

Thrombus formation within aneurysm is common and has generally been proved to be a slowly progressive phenomenon. We report two cases of acute completely thrombosis of aneurysms. The initial angiogram failed to reveal aneurysm and other etiology of subarachnoid hemorrhage. CT revealed diffuse cisternal blood and acute hydrocephalus. We decided to operate on these patients in the acute stage because of the generally-known strict correlation between the amount of cisternal high density on CT and the subsequent development of vasospasm and ischemic event. Case 1. A 68 year-old female was admitted on Day 1 with neurological deterioration of Grade 3 (H & K). Complete angiographic study was done, including the basal view and stereotechnique, but failed to reveal aneurysm. On Day 2 we operated on this patient and discovered a thrombosed aneurysm of the anterior communicating artery (3 X 7 mm in size). Case 2. A 51 year-old male suffering from subarachnoid hemorrhage was transferred to our hospital on Day 0. Emergency angiography gave no information, but the pattern of cisternal clots on CT was suggested the existence of an aneurysm of the right internal carotid artery. The next day we performed angiography once more, at that time 2 X 5 mm internal carotid bifurcated aneurysm was revealed. Shortly thereafter we operated and found the intra-aneurysmal clot. Through consideration of these we have reached the following conclusions. When CT findings in a patient with subarachnoid hemorrhage show the diffuse cisternal clots due to rupture of aneurysm, we should consider immediate surgery even if the angiogram is negative in order to lessen the risk of delayed vasospasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1985

Contribution of promoter to tissue-specific expression of the mouse immunoglobulin kappa gene.

The immunoglobulin kappa (kappa) gene promoter was activated by a "neutral" enhancer derived from Harvey murine sarcoma virus (HaMuSV) in immunoglobulin-producing myeloma cells, regardless of the enhancer's orientation or position in the vector. In one fibroblast line (3T3) the immunoglobulin kappa gene promoter was completely inactive when linked to the HaMuSV enhancer, whereas in mouse L cells, promoter activity was observed only with the HaMuSV enhancer in tandem with the immunoglobulin kappa gene promoter. The differential behavior of the gene promoter, when activated by a neutral enhancer in these three murine cell lines, suggests that promoter sequences contribute to the tissue-specific expression of this gene.

Animals↗
PubMed1985

A convenient assay for mephenytoin 4-hydroxylase activity of human liver microsomal cytochrome P-450.

A simple and rapid method for the determination of (S)-mephenytoin 4-hydroxylase activity by human liver microsomal cytochrome P-450 has been developed. [Methyl-14C] mephenytoin was synthesized by alkylation of S-nirvanol with 14CH3I and used as a substrate. After incubation of [methyl-14C]mephenytoin with human liver microsomes or a reconstituted monooxygenase system containing partially purified human liver cytochrome P-450, the 4-hydroxylated metabolite of mephenytoin was separated by thin-layer chromatography and quantified. The formation of the metabolite depended on the incubation time, substrate concentration, and cytochrome P-450 concentration and was found to be optimal at pH 7.4. The Km and Vmax rates obtained with a human liver microsomal preparation were 0.1 mM and 0.23 nmol 4-hydroxymephenytoin formed/min/nmol cytochrome P-450, respectively. The hydroxylation activity showed absolute requirements for cytochrome P-450, NADPH-cytochrome P-450 reductase, and NADPH in a reconstituted monooxygenase system. Activities varied from 5.6 to 156 pmol 4-hydroxymephenytoin formed/min/nmol cytochrome P-450 in 11 human liver microsomal preparations. The basic system utilized for the analysis of mephenytoin 4-hydroxylation can also be applied to the estimation of other enzyme activities in which phenol formation occurs.

Aryl Hydrocarbon Hydroxylases↗
PubMed1985

Activation of factor XII and prekallikrein with cholesterol sulfate.

Cholesterol sulfate was found to display a strong ability to trigger the activation of Factor XII and prekallikrein in the presence of HMW kininogen. Other sulfate ester derivatives of testosterone, estrone, pregnenolone and dehydroepiandrosterone and cholesterol tested did not show any effect on the activation of Factor XII and prekallikrein. The activity of cholesterol acetate and sulfodeoxycholic acid was very weak. Cholesterol sulfate markedly shortened the partial thromboplastin time of normal human plasma, but not plasmas deficient in Factor XII, Factor XI and HMW kininogen. Upon prolonged incubation, the partial thromboplastin time of prekallikrein-deficient plasma was also shortened. Moreover, as well as kaolin and sulfatide, cholesterol sulfate shortened the partial thromboplastin time of plasmas from monkey, dog, rat, guinea pig, sheep, cow, hog and horse, but not from duck and chicken. Since cholesterol sulfate is distributed in erythrocytes, various organs and body fluids, it may play an important role in the activation of the intrinsic blood coagulation system.

Animals↗
PubMed1985

Proton-coupled transport of glycylglycine in rabbit renal brush-border membrane vesicles.

Transport of glycylglycine into rabbit renal brush-border membrane vesicles was found to be Na+-independent, H+ gradient-dependent and electrogenic. Marked overshoot uptake of the dipeptide was observed when an inward-directed proton gradient and inside-negative potential difference were imposed simultaneously across the vesicular membranes. Saturable depolarization of vesicular membranes could be demonstrated with glycylglycine by use of a fluorescent cyanine dye, di-S-C3(5). The results indicate that glycylglycine is contransported with H+ across the membranes.

Animals↗
PubMed1985

A new function of kininogens as thiol-proteinase inhibitors: inhibition of papain and cathepsins B, H and L by bovine, rat and human plasma kininogens.

The amidolytic activities of papain and rat liver cathepsins B, H and L were strongly inhibited by high (HMM) and low (LMM) molecular mass kininogens from bovine, human and rat plasmas, and their Ki values were estimated to be in the order of 10(-10) - 10(-11)M for papain and 10(-8) - 10(-9)M for cathepsins. The derivatives of bovine kininogens, HMM kinin-free protein, HMM kinin- and fragment 1 X 2-free protein, and LMM kinin-free protein also showed strong inhibitory activity toward these thiol-proteinases. These results suggest that a reactive site which interacts with thiol-proteinases is contained in the heavy chain portion in kininogens.

Animals↗
PubMed1985

Only the promoter region of the constitutively expressed normal and amplified human dihydrofolate reductase gene is DNase I hypersensitive and undermethylated.

The human dihydrofolate reductase (DHFR) gene was found to be undermethylated only in its 5' promoter region; the remaining CCGG residues in the 30-kilobase (kb) DHFR gene were insensitive to digestion by HpaII. Each of 27 CpG residues that were part of an HpaII or HhaI cutting site within a 1.1-kb segment of the DHFR gene promoter region were found to be unmethylated. All 80 copies of the DHFR gene in methotrexate-resistant HeLa cell line exhibited this pattern of undermethylation of only the promoter region. This same region was shown to be DNase I hypersensitive in chromatin from normal cells and from those cells in which the DHFR gene was amplified. Again, all copies of the amplified gene exhibited DNase I hypersensitivity of the promoter region. The remainder of the 30-kb DHFR gene is both completely methylated and insensitive to DNase I digestion. Detailed mapping of the DNase I-hypersensitive region revealed four strong cutting sites within a 500-base pair segment immediately upstream from the DHFR coding sequence and a weak cutting site within intron I. Two of the strong DNase I cutting sites in chromatin were also sensitive to S1 nuclease nicking when this DNA fragment was part of supercoiled plasmid DNA. Promoter undermethylation and DNase I hypersensitivity, features previously shown for specialized and inducible genes, have now been shown to be characteristic of the constitutively expressed DHFR gene. That these features characterize all copies of the amplified DHFR gene in a methotrexate-resistant cell line suggest that all gene copies are transcriptionally active.

Cell Line↗