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Biomedical subjects

M Hatano

Publications and source records attributed to M Hatano.

At least 73 records · Page 4Linked to original sources
PubMed1995

Two forms of Hox11 a T cell leukemia oncogene, are expressed in fetal spleen but not in primary lymphocytes.

HOX11 is identified from the breakpoint of human T cell acute lymphoblastic leukemias with t(10;14). Since overexpression of HOX11 in T cells caused leukemias in transgenic mice, the endogenous HOX11 may play a role in proliferation and differentiation of T cells. In order to elucidate the role, we examined the expression of Hox11 in normal lymphocytes by a reverse transcriptase-polymerase chain reaction analysis. Two alternatively spliced Hox11 mRNAs were expressed in fetal spleens. However, lymphocytes did not express Hox11 mRNA during differentiation. Furthermore, it was not induced in primary lymphocytes after activation. These results suggest that ectopic expression of HOX11 in T cells is responsible for leukemogenesis.

Animals↗
PubMed1995

An unseasonable winter outbreak of echovirus type 30 meningitis.

During the winter of late October, 1990 to March, 1991, echovirus type 30 meningitis affected 10 children aged 3-9 years of age in Mikuni, Japan. Five patients presented with constipation, four had diarrhoea, while five complained of severe abdominal pain, in addition to typical symptoms and signs compatible with aseptic meningitis. Echovirus type 30 was isolated from the CSF of nine, from the faeces of 10, and from the throats of eight children. All showed a significant antibody response to echovirus type 30 in paired samples of serum. Antigenic variation and thermostability of a representative isolate indicated some changes in virus structural proteins, possibly reflecting an altered tropism for tissues in the gastrointestinal tract.

Abdominal Pain↗
PubMed1995

Evaluation of cerebral blood flow in patients with idiopathic orthostatic hypotension using Tc-99m HMPAO brain SPECT during postural testing.

To determine whether regional cerebral blood flow (rCBF) would change on standing in patients with idiopathic orthostatic hypotension (IOH), Tc-99m HMPAO SPECT studies were performed during postural testing in five patients with IOH. After 10 minutes of quiet rest on a bed, the patients arose quickly and, at the same time, the radiotracer was injected intravenously. SPECT data were obtained with a ring-type SPECT scanner. Another dose of Tc-99m HMPAO was injected with the subjects in the supine position, and SPECT was performed again. Image subtraction was used to evaluate the change in rCBF caused by postural testing. In all patients, the authors observed a decrease of rCBF ni the frontal cortex and basal ganglia. This preliminary study suggests that changes in rCBF occur in patients with IOH on standing, and Tc-99m HMPAO SPECT performed during postural testing may have an important role in evaluating these changes.

Brain↗
PubMed1995

Insect cell expression of recombinant imidazoleglycerolphosphate dehydratase of Arabidopsis and wheat and inhibition by triazole herbicides.

Imidazoleglycerolphosphate dehydratase (IGPD; EC 4.2.1.19), which is involved in the histidine biosynthetic pathway of Arabidopsis thaliana and wheat (Triticum aestivum), has been expressed in insect cells using the baculovirus expression vector system. N-terminal amino acid sequencing indicated that recombinant IGPDs (rIGPDs) were produced as mature forms via nonspecific proteolytic cleavages in the putative transit peptide region. The wheat rIGPD contained one Mn atom per subunit, and the Mn was involved in the assembly of the subunits to form active IGPDs. Protein-blotting analysis, using antibodies raised against the wheat rIGPD, indicated that IGPD was located in the chloroplasts of wheat. The rIGPDs of Arabidopsis and wheat, which were 86% identical in their primary structures deduced from the cDNAs, exhibited similar properties in terms of the molecular mass, pH optimum, and the Km for the substrate, imidazoleglycerolphosphate. However, the nonselective herbicides 3-amino-1,2,4-triazole and a newly synthesized triazole [(1R*, 3R*)-[3-hydroxy-3-(2H-[1,2,4]triazole-3-yl)-cyclohexyl]- phosphonic acid], inhibited Arabidopsis and wheat IGPDs in a mixed-type and a competitive manner, respectively.

Amino Acid Sequence↗
PubMed1995

[A study on accuracy of rCBF measurements using the conventional microsphere method with N-isopropyl-p-[123I]iodoamphetamine and SPECT].

To evaluate the accuracy of conventional microsphere method for the measurement of regional cerebral blood flow (rCBF) based on the microsphere model with N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) and SPECT, we performed simulation analysis and clinical studies. Although the microsphere method requires early SPECT scan at a few minutes after injection of the tracer for the accurate measurement of rCBF, the conventional microsphere method, which is generally used, requires more delayed SPECT scan with long scan-duration. In the conventional microsphere method, the delayed SPECT image is corrected to the image at a few minutes after injection of the tracer by using the monitored entire brain activity. By the simulation analysis based on the 2-compartment model (influx; K1 and outflux; k2) using the input function and the entire brain activity obtained from eight subjects respectively, it was found that the conventional microsphere method overestimated the rCBF in the practical range of rCBF and Vd (= K1/k2) given in the 2-compartment model. When the values of rCBF and Vd in the 2-compartment model were given at 0.5 (ml/g/min) and 30 (ml/g) respectively, the rate of overestimation of rCBF by the conventional microsphere method was determined to be 17.3 +/- 0.7% (mean +/- S.D.). Also in clinical studies for eight subjects, the conventional microsphere method overestimated the rCBF compared with those evaluated by non-linear least squares fitting (NLLSF) analysis based on the 2-compartment model. Those results agreed well with the simulation analysis, suggesting the validity of the simulation. The rCBF values clinically estimated by the conventional method were, however, significantly correlated with those calculated by NLLSF analysis, and there were not so much difference between the two quantitative rCBF images obtained by the conventional microsphere method and the microsphere method. Therefore, we conclude that the conventional microsphere method is clinically useful in spite of the overestimation of rCBF.

Amphetamines↗
PubMed1994

Analysis of IL-2 gene regulation in c-fos transgenic mice. Evidence for an enhancement of IL-2 expression in splenic T cells stimulated via TCR/CD3 complex.

Effects of the deregulated c-fos gene product on IL-2 expression were studied in splenic T cells from c-fos transgenic (H2-c-fos) mice. IL-2 gene expression and IL-2 production by H2-c-fos T cells stimulated with immobilized anti-CD3 Abs were enhanced and prolonged as compared with those by control T cells. Activator protein-1 activity in nuclear extract from the H2-c-fos T cells was also higher than that from the control cells. There was no significant difference in the activity of other transcription factors including IL-2 kappa B, NFAT, and Oct-1, between the H2-c-fos and the control T cells. However, activity of a negative regulatory element binding factor (NRE-A) in the H2-c-fos T cells was much lower than that in the control cells. These results suggest that c-Fos/activator protein-1 is a major regulatory factor for IL-2 gene expression in splenic T cells activated through the TCR/CD3 complex.

Animals↗
PubMed1994

Glu318 and Thr319 mutations of cytochrome P450 1A2 remarkably enhance homolytic O-O cleavage of alkyl hydroperoxides. An optical absorption spectral study.

Interactions of putative distal mutants of cytochrome P450 1A2 (P450 1A2) with hydroperoxides were studied with optical absorption spectroscopy. The Soret absorption at 393 nm of the wild-type P450 1A2 decreased by adding H2O2, tert-butyl hydroperoxide (TBHP), and cumyl hydroperoxide (CHP), whereas the absorption decrease was accompanied by the appearance of a new band around 423 nm for Glu318 and Thr319 mutants with similar treatments. Spectral simulation based on Gaussian analyses and visible bands indicate that H2O2- and TBHP-induced intermediates' spectra of the wild type are close to that of Compound I of horseradish peroxidase, whereas TBHP- and CHP-induced intermediates' spectra of the mutants are close to that of Compound II of horseradish peroxidase. Based on kinetic parameters of the spectral changes, it is suggested that: 1) TBHP and CHP mainly form porphyrin+.FeIV = O due to heterolytic O-O scission in the wild type, while forming porphyrinFeIV = O for the mutants owing to homolytic O-O scission; and 2) heterolytic O-O scission of H2O2 is not changed by the mutations. Heterolytic/homolytic cleavage ratios for the P450 1A2 reactions with CHP obtained from product analysis were consistent with those obtained from spectral changes.

Alcohols↗
PubMed1994

Essential role of His163 of cytochrome P450 1A2 in catalytic functions associated with cytochrome b5.

The effect of cytochrome b5 on the activity of cytochrome P450 1A2 (P450 1A2) and three site-directed mutants designed to alter surface charges has been investigated. Cytochrome b5 increased the rate of oxidation of methanol and/or 7-ethoxycoumarin 2- to 10-fold in both wild type and mutant P450. Cytochrome b5 also increased the coupling of electron transfer to substrate hydroxylation as opposed to the uncoupling reaction which leads to peroxide production. The effect of cytochrome b5 on both wild type and the Lys99Glu and Lys401Glu mutants are similar. In contrast, turnover numbers in the His163Glu mutant did not change in the presence of cytochrome b5. The reduction potential of the His163Glu mutant decreased approximately -40 mV while the Lys99Glu and Lys401Glu mutants exhibited little change. The rate of photoreduction decreased from 1.1 x 10(-1) min-1 to 8.3 x 10(-3) min-1 in the His163Glu mutant while the rate of electron transfer from ferrous P450 to ferric cytochrome b5 increased from 0.02 min-1 to > 5 min-1. Overall, the present study suggests that His163 is important to keep an appropriate redox potential of P450 1A2 for optimum electron transfer to occur from cytochrome b5. Based on the P450 101 crystal structure, His163 is not expected to directly contact the heme. Therefore, the resulting change in redox properties in the His163Glu mutant is probably not the result of a direct electrostatic change in the heme environment.

Amino Acid Sequence↗
PubMed1994

Differential roles of Glu318 and Thr319 in cytochrome P450 1A2 catalysis supported by NADPH-cytochrome P450 reductase and tert-butyl hydroperoxide.

The kinetic values for 7-ethoxycoumarin (7-EC) hydroxylation have been obtained in both the NADPH-cytochrome P450 reductase- and tert-butyl hydroperoxide (TBHP)-supported systems for several Glu318 and Thr319 mutants of cytochrome P450 1A2. The results with the reductase-supported system suggest that Glu318 is important for both substrate binding and catalysis, whereas Thr319 is critical for neither, although the size of the residue at position 319 influences catalytic activity. In contrast, neither Glu318 nor Thr319 appears to be important for catalytic turnover in the TBHP-supported system despite the fact that the size of the amino acid at position 319 affects the binding of TBHP and 7-EC in opposite manners. The roles of these two distal amino acids in the cytochrome P450 1A2-catalyzed oxidation of 7-EC therefore differ for the reactions supported by cytochrome P450 reductase and TBHP.

Amino Acid Sequence↗
PubMed1994

[Quantifying regional cerebral blood flow with N-isopropyl-p-[123I]iodoamphetamine and SPECT by one-point sampling method].

We developed a new non-invasive technique; one-point sampling method, for quantitative measurement of regional cerebral blood flow (rCBF) with N-isopropyl-p-[123I]iodoamphetamine and SPECT. Although the continuous withdrawal of arterial blood and octanol treatment of the blood are required in the conventional microsphere method, the new technique does not require these two procedures. The total activity of 123I-IMP obtained by the continuous withdrawal of arterial blood is inferred by the activity of 123I-IMP obtained by the one point arterial sample using a regression line. To determine when one point sampling time was optimum for inferring integral input function of the continuous withdrawal and whether the treatment of sampled blood for octanol fraction was required, we examined a correlation between the total activity of arterial blood withdrawn from 0 to 5 min after the injection and the activity of one point sample obtained at time t, and calculated a regression line. As the results, the minimum % error for the inference using the regression line was obtained at 6 min after the 123I-IMP injection, moreover, the octanol treatment was not required. Then examining an effect on the values of rCBF when the sampling time was deviated from 6 min, we could correct the values in approximately 3% error when the sample was obtained at 6 +/- 1 min after the injection. The one-point sampling method provides accurate and relatively non-invasive measurement of rCBF without octanol extraction of arterial blood.

Adolescent↗
PubMed1994

[A problem of quantitative measurement of regional cerebral blood flow using microsphere model and N-isopropyl-p-[123I]iodoamphetamine (IMP): comparison with 133Xe SPECT and sequential dynamic 123I-IMP SPECT].

Regional cerebral blood flow (rCBF) was measured in 13 patients with various cerebral disease by N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT with the microsphere model (rCBF (CbST)), which was compared with 133Xe inhalation SPECT (rCBFXe). Continuous withdrawal of arterial blood was performed for 5 minutes and SPECT image was obtained from 25 min to 55 min after the tracer injection. The reconstructed counts at 5 min was corrected using entire cerebral counts collected at 5 min, 20 min, and 60 min after the tracer injection. As compared with rCBFXe, rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. Regional CBF was also measured using one minute short time SPECT images at 5 min (rCBF (Cb5)), 20 min (rCBF (Cb20)), and 60 min (rCBF (Cb60)) after the injection. Regional CBF tended to be underestimated with time from the tracer injection due to the wash-out from brain tissue to blood. In comparison with rCBF (Cb5), rCBF (CbST) was underestimated in high flow areas and overestimated in low flow areas. This error was considered to be due to the correction of reconstruct counts using entire cerebral counts, because of the kinetic behavior of 123I-IMP was different in each region of the brain.

Adult↗
PubMed1993

Effect of mutations of ionic amino acids of cytochrome P450 1A2 on catalytic activities toward 7-ethoxycoumarin and methanol.

Catalytic efficiencies, percentages of rates of product formation per NADPH oxidized, and rates of product formation per O2 consumed of ionic mutants of cytochrome P450 1A2 (P450 1A2) were studied. Efficiencies of Lys99Glu, Lys453Glu, and Arg455Glu mutants for the hydroxylation reaction toward 7-ethoxycoumarin in the reconstituted system were much lower than that of the wild type (less than 17%), which corresponds to lower turnover numbers for these mutants. In contrast, the catalytic efficiencies for the hydroxylation reaction toward methanol of the three mutants were more than 45% that of the wild type in spite of these mutants' lower turnover numbers. Turnover numbers and catalytic efficiencies of Arg137Leu and Lys401 Glu mutants toward both substrates were comparable to those of the wild type. The electron-transfer rate from the reductase to the heme of P450 1A2 was decreased by 30% upon addition of excess methanol, while it was not influenced by addition of excess 7-ethoxycoumarin. The turnover numbers toward both 7-ethoxycoumarin and methanol as well as the rate constant of electron transfer were decreased by 25-40% by raising the concentration of KCl from 0 to 300 mM in the reconstituted system containing 50 mM potassium phosphate buffer. The turnover numbers toward both substrates of the above-mentioned five ionic mutants caused by tert-butyl hydroperoxide in the absence of the reductase and NADPH were comparable to those of the wild type. The effect of phospholipid constituents on the catalytic activity toward 7-ethoxycoumarin of the wild type was also studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Regulation of class II MHC gene expression by the inducible anti-sense RNA in transgenic mice.

We have established a gene regulatory system in mice by the inducible anti-sense RNA. We have generated transgenic mice carrying the anti-sense DNA composed of the class II MHC gene under the control of the human metallothionein IIa gene promoter. The detectable amount of anti-sense RNA was constitutively produced in spleen and bone marrow from transgenic mice and the amount in spleen was increased about fivefold by the stimulation of mice with heavy metal ions. We have previously reported that the reduction of class II MHC molecules on early B lineage cells by the anti-sense RNA results in delay of their development in the bone marrow culture. The early B cell development was slightly delayed in the culture from the transgenic mice. This delay was augmented in the culture by the addition of heavy metal ions in proportion to its concentration. These results suggest that the inducible anti-sense RNA reduces the expression of class II MHC molecules on B lineage cells.

Animals↗
PubMed1993

The cytochrome P450 1A2 active site: topology and perturbations caused by glutamic acid-318 and threonine-319 mutations.

Phenyldiazene reacts with rat liver CYP1A2 expressed in Saccharomyces cerevisiae to give a phenyl-iron complex that rearranges to a mixture (NB:NA:NC:ND = 12:54:14:20, subscript indicates pyrrole ring) of N-phenyl-PPIX (PPIX = protoporphyrin) regioisomers. The same isomer pattern is obtained in each instance when the purified or microsomal enzyme reacts with phenyldiazene, indicating that the active site topology is not altered by removal of the protein from the membrane. Reaction of the enzyme with biphenylhydrazine gives a similar distribution of N-biphenyl-PPIX isomers, but reaction with (2-naphthyl)-hydrazine only gives the NC and ND regioisomers and a trace of the NA isomer of N-(2-naphthyl)-PPIX. The mutations E318D, E318A, and E318V cause relatively minor changes in the observed regioisomer ratios. In contrast, the mutations T319A, T319V, and T319S suppress formation of the NC and ND isomers of N-phenyl-PPIX. The reaction of T319A with biphenylhydrazine yields major amounts of the NB adduct rather than the small amounts observed with CYP1A2 and the Glu-318 mutants, but does not give the NC and ND regioisomers. Other, less dramatic, changes in the isomer ratios are also observed. The results indicate that the active site of CYP1A2 is open above all four quadrants of the heme group including, to some extent, the region above pyrrole ring B. Pyrrole ring B is completely inaccessible in most cytochrome P450 enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Chiral recognition at cytochrome P450 1A2 active site: effects of mutations at the putative distal site on the bindings of asymmetrical axial ligands.

Effects of mutations at the putative distal site of cytochrome P450 1A2 on chiral discrimination for binding (R)-(+)- and (S)-(-)-1-(1-naphthyl)ethylamine (ligand I), (R)-(-)- and (S)-(+)-1-cyclohexylethylamine (ligand II), and (R)-(+)- and (S)-(-)-1-(4-pyridyl)ethanol (ligand III) were studied by optical absorption spectra. The wild-type P450 1A2 exhibited different dissociation constants (Kd) for the R- and S-enantiomers of these ligands. The R/S ratios of the Kd values for ligands I and II were 5.2 and 2.9, respectively, and the S/R ratio for ligand III was 6.0. Mutations at the putative distal site, such as Glu318Asp and Glu318Ala, remarkably enhanced the discrimination: the R/S ratio of the Kd values for ligand I increased from 5.2 to 20-60, while the R/S ratio for ligand II decreased from 2.9 to 0.8-0.9. These remarkable changes in the R/S ratios were not observed with Glu318Asp mutation for ligand III binding, whereas affinities for both enantiomers of ligand III were markedly decreased by the Glu318Ala mutation. Mutation Thr319Ala increased the R/S ratio of the Kd values for ligand I slightly but markedly decreased the R/S ratio of ligand II (from 2.9 to 0.8) and the S/R ratio of ligand III (from 6.0 to 1.0). Similar enhancements of the chiral discriminations were observed with the mutation Lys250Leu at another putative substrate-recognition site. Differences between the R- and S-enantiomers of the standard enthalpy and entropy of ligand III binding were changed most remarkably by the Thr319Ser mutation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

[A new graphic method for evaluation of distribution volume on N-isopropyl-p-[123I]iodoamphetamine (IMP) SPECT].

We developed a new graphic method using N-isopropyl-p-[123I]iodoamphetamine (IMP) and SPECT of the brain, the graph on which all three parameters, cerebral blood flow, distribution volume (Vd) and delayed count to early count ratio (Delayed/Early ratio), were able to be evaluated simultaneously. The kinetics of 123I-IMP in the brain was analyzed by a 2-compartment model, and a standard input function was prepared by averaging the time activity curves of 123I-IMP in arterial blood on 6 patients with small cerebral infarction etc. including 2 normal controls. Being applied this method to the differential diagnosis between Parkinson's disease and progressive supranuclear palsy, we were able to differentiate both with a glance, because the distribution volume of the frontal lobe significantly decreased in Parkinson's disease (Mean +/- SD; 26 +/- 6 ml/g). This method was clinically useful. We think that the distribution volume of 123I-IMP may reflect its retention mechanism in the brain, and the values are related to amine, especially to dopamine receptors and its metabolism.

Aged↗