Biomedical subjects

K Shiga

Publications and source records attributed to K Shiga.

At least 73 records · Page 4Linked to original sources

PubMed1992

A point mutation of c-Ki-ras gene was found in human esophageal carcinoma cell lines but not in primary esophageal carcinomas.

Activation of the ras oncogene in primary human esophageal carcinomas and cell lines established from such carcinomas was analyzed using the polymerase chain reaction (PCR)-direct sequencing method. This analysis revealed a GC----AT transition at the second base in the 12th codon of the c-Ki-ras gene in TE1 and TE2 esophageal carcinoma cell lines. In contrast, no point mutation was detected in the 12th, 13th, and 61st codon of the c-Ki-ras and c-Ha-ras gene in 31 primary esophageal carcinomas including those from which TE1 and TE2 cell lines were established. These results demonstrate that while activation of the c-Ki-ras gene by point mutation occurred in a subset of esophageal carcinoma cell lines during establishment of the cell lines, the activation events are not important in the transformation of human esophageal epithelial cells.

Adenocarcinoma↗

PubMed1992

Anion-induced conformational change of apo-electron-transferring flavoprotein.

Apoprotein of electron-transferring flavoprotein (ETF) exists in an equilibrium between two different forms, only one of which can associate with FAD (Sato, K. et al. (1991) J. Biochem. 109, 734-740), as represented in the following kinetic scheme: A* in equilibrium with A, A+FAD in equilibrium with holoETF, where "A*" and "A" are the different forms of apoETF. In the present study, the effects of various anions on the conversion between the two forms of apoETF were investigated by kinetic analyses on binding of FAD to apoETF. All the anions tested here induced the conversion from "A*" to "A"; the order of the effectiveness was I- approximately Br- greater than Cl- greater than F-. Further, glycerol also induced the conversion from "A*" to "A". The elution pattern of apoETF on molecular sieve chromatography was changed by addition of salts or glycerol; this change was due to the conversion from "A*" to "A" by the added solutes. The "A*" form was eluted more rapidly than the "A" form, indicating that the "A*" form exists in a looser conformation than the "A" form. The far-UV CD spectral change upon addition of salts indicated that a greater part of the secondary structure is retained in the conversion from "A*" to "A," but the "A" form contains a somewhat larger amount of beta-sheet than "A*."

Algorithms↗

PubMed1992

Resonance Raman study on complexes of medium-chain acyl-CoA dehydrogenase.

Resonance Raman (RR) spectra of the complex of pig kidney medium-chain acyl-CoA dehydrogenase with acetoacetyl-CoA and of the purple complex formed upon the addition of octanoyl-CoA to the dehydrogenase were obtained. RR spectra were also measured for the complexes prepared by using isotopically labeled compounds, i.e., [3-13C]-, [1,3-13C]-, and [2,4-13C2]acetoacetyl-CoA; [1-13C]octanoyl-CoA; the dehydrogenase reconstituted with [4a-13C]- and [4,10a-13C2]FAD. Both bands of oxidized flavin and acetoacetyl-CoA were resonance-enhanced in the 632.8 nm excited spectra of the acetoacetyl-CoA complex; this confirms that the broad long-wavelength absorption band is a charge-transfer absorption band between oxidized flavin and acetoacetyl-CoA. The 1,622 cm-1 band was assigned to the C(3)=O stretching mode coupling with the C(2)-H bending mode of the enolate form of acetoacetyl-CoA and the bands at 1,483 and 1,119 cm-1 were assigned to bands associated with the C(2)=C(1)-O- moiety. Both bands of fully reduced flavin and the substrate were resonance-enhanced in the 632.8 nm excited spectra of the purple complex. As the enzyme is already reduced, the substrate must be oxidized to octenoyl-CoA; the complex is a charge-transfer complex between the reduced enzyme and octenoyl-CoA. The low frequency value of the 1,577 cm-1 band, which is associated with the C(2)-C(1)=O moiety of the octenoyl-CoA, suggests that the enzyme-bound octenoyl-CoA has an appreciable contribution of C(2)=C(1)-O-.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗

PubMed1992

The binding of adenine nucleotides to apo-electron-transferring flavoprotein.

Apoprotein of electron-transferring flavoprotein (ETF) reacts with FAD as follows: A*<-->A, A+FAD<-->holoETF. Two different forms of apoETF (A* and A) convert into each other and only one of them, A, can associate with FAD [Sato, K. et al. (1991) J. Biochem. 109, 734-740]. In the present study, the reactions between apoETF and ATP, ADP, AMP, riboflavin, or FMN were investigated. It was revealed that all three adenine nucleotides bind with apoETF with the same kinetic reaction scheme as FAD, and compete with FAD. These results suggest that the nucleotides bind to A with the same location as the ADP part of FAD in holoETF and that the ADP-binding site of apoETF is generated upon conversion from A* to A. Neither riboflavin nor FMN bound to apoETF regardless of the presence or absence of the nucleotides, indicating that the ADP part of the FAD molecule is essential to the incorporation of the isoalloxazine ring into ETF. The binding rate constant of FAD to A was 1/20 of that of ADP while the dissociation rate constant was 1/1,000. This indicates that the riboflavin part of FAD inhibits the binding of FAD by steric hindrance, while after the binding, it stabilizes the complex.

Adenine Nucleotides↗

PubMed1992

[Extent and degree of coronary flow reserve in hypertrophic cardiomyopathy assessed by delta Fract map unfolding coronary flow reserve index].

Patients with hypertrophic cardiomyopathy (HCM) are known to have ischemic events and decreased coronary flow reserve, but the variabilities in the site and degree of fall between patients with this disease have not been clarified. To elucidate these variabilities, we performed exercise myocardial single photon emission computed tomography (SPECT) using double dose method in 30 patients with HCM (6 with obstruction, 17 with non-obstruction, 7 with apical hypertrophy) and 10 normals. Then, the delta Fract (coronary flow reserve index) map was obtained for each subject. Exercise and then rest Tl-201 myocardial scintigraphy were performed after administration of Tl-201. The data were reconstructed, making the circumferential curves from the same level of short-axis imaging during exercise and at rest. By subtracting the values at rest from the values during exercise, which were divided by the values at rest, delta Fract in each frame was obtained, and described on the unfolded map. The extent and degree of coronary flow reserve were visually estimated by this delta Fract map. Patients were categorized into 5 groups: diffuse fall of coronary flow reserve (D-type), 6 cases; localized fall of the septum or lateral wall (L-type), 5 cases; fall of apical region (A-type), 5 cases; mild fall (M-type), 6 cases; and normal pattern (N-type), 8 cases. We concluded that delta Fract map is useful for evaluating the extent and degree of coronary flow reserve in HCM.

Adult↗

PubMed1992

[Repeated blackout in a patient with accelerated idioventricular rhythm].

There has been no report that Accelerated Idioventricular rhythm (AIVR) causes a syncope attack. The patient described in this report is very rare because AIVR chronic without any heart diseases has been observed for 13 years, and because it is considered that AIVR is closely associated with his repeated blackouts. A 62-year-old male was admitted to our hospital because of repeated syncopal attacks. He reported that he occasionally felt lightheaded after strenuous lifting and pushing or pulling against resistance. We found that AIVR could produce a remarkable arterial pressure drop partly because of ventricular asynergy and loss of timed atrial contribution. Furthermore, we observed syncopal attacks during Valsalva maneuver and found abnormalities of baroreceptor reflex (Lack of reflex tachycardia and weakened evershoot phenomenon). It is concluded that AIVR is not a benign arrhythmia in this patient because it has been a possible cause of syncope attack due to systemic arterial pressure drop and baroreceptor abnormalities.

Accelerated Idioventricular Rhythm↗

PubMed1992

[Clinical evaluation of 123I-BMIPP myocardial scintigraphy in patients with hypertrophic cardiomyopathy].

123I-BMIPP myocardial scintigraphy was performed in 13 patients with hypertrophic cardiomyopathy and compared with 201Tl myocardial scintigraphy performed within 3 months for evaluating the clinical significance of 123I-BMIPP myocardial scintigraphy. SPECT images were divided into 13 segments and segmental images were visually scored on a 4 (increased tracer uptake) to 0 (severely decreased tracer uptake) scale according to the tracer uptake. In comparison of 123I-BMIPP early images and 201Tl perfusion images, mismatches were seen in about 70% of all segments. The number of segments demonstrating lower myocardial uptake of 123I-BMIPP was larger than that of 201Tl. In hypertrophic regions, the tracer uptake of 123I-BMIPP early images was significantly lower than that of 201Tl images and the lower uptake of 123I-BMIPP delayed images was more marked. In non-hypertrophic regions, no significant difference was seen between the tracer uptakes of 123I-BMIPP early images and 201Tl images but the tracer uptake of 123I-BMIPP delayed images was significantly lower than that of 201Tl images. The mismatch between the tracer uptakes of 123I-BMIPP images and 201Tl images was thought to be a reflection of disordered myocardial fatty acid metabolism. "Washout", the difference between the tracer uptakes of 123I-BMIPP early images and delayed images was also thought to be a reflection of disordered myocardial fatty acid metabolism. These results suggest that 123I-BMIPP is a promising radiopharmaceutical for evaluating disordered myocardial fatty acid metabolism in patients with HCM.

Cardiomyopathy, Hypertrophic↗

PubMed1992

[Diffuse subendocardial ischemia in a patient with aortic valve stenosis without coronary artery disease by exercise 201Tl SPECT].

A case of aortic valve stenosis without coronary artery disease was confirmed to have diffuse subendocardial ischemia by exercise Thallium-201 myocardial single photon emission computed tomography. A 72-year-old woman, who had been diagnosed as aortic valve stenosis, was admitted because of chest pain during exercise. In cardiac catheterization findings, the patient angiographically had normal coronary arteries and no asynergy of left ventricular wall motion. The peak flow velocity in continuous wave Doppler echocardiography was about 5.0 m/sec at aortic valve level, providing a pressure drop of 100 mmHg across a stenotic valve with calculating on a modified Bernoulli equation (PG = 4V2). Thallium-201 myocardial SPECT images during exercise showed a transient "dilation and a widespread wall thinning" of left ventricle with apical perfusion defect. Simultaneous electrocardiogram showed further ST depression and the patient had chest pain. In 6 months after aortic valve replacement the patient no longer demonstrated both apical perfusion defect and "wall thinning" in postoperative thallium-201 myocardial SPECT images and also had neither ST depression nor chest pain. Thus; a transient "dilation and wall thinning" of left ventricle in this patient is suspected to be a sign of diffuse subendocardial ischemia.

Aged↗

PubMed1991

Sequence of the chicken rig gene encoding ribosomal protein S15.

The nucleotide sequence of the chicken rig gene encoding ribosomal protein S15 was determined. The 1.6-kb gene consists of four exons and three introns. The 5'-flanking region of the gene lacks TATA- or CAAT-box sequences. Several GC-box sequences were found around the transcription start point.

Amino Acid Sequence↗

PubMed1991

Isomerization of delta 1-piperideine-2-carboxylate to delta 2-piperideine-2-carboxylate on complexation with flavoprotein D-amino acid oxidase.

The 1,646 cm-1 band in a resonance Raman spectrum obtained with excitation in the charge-transfer band of the complex of oxidized D-amino acid oxidase (DAO) with the oxidation product of D-lysine catalyzed by DAO shifted to 1,617 cm-1 upon 2-13C substitution of lysine. Thus, the band is assigned to a C(2) = C(3) stretching mode of the enamine, delta 2-piperideine-2-carboxylate (En). In the enzyme-free solution, the product is preferentially in the cyclic imine form, delta 1-piperideine-2-carboxylate (Im). Thus, DAO has a higher affinity for the enamine form than for the imine form. The pH effects on the affinity of DAO for the product and on the molar absorption coefficient at 630 nm in the charge-transfer band, suggest that the enzyme-bound product is En in the neutral form at the N atom. As the value of observed rate constant between DAO and the product was constant at high product concentrations, the binding mechanism can be explained as follows; E + Im in equilibrium with EIm in equilibrium with EEN: rapid bimolecular and slow unimolecular processes. The isomerization of the imine form to the enamine form proceeds in the slow process. The low affinity of Im for DAO may be due to a steric repulsion of the hydrogen atoms of Im at C(3) in the active site. The hydrogen atoms of a substrate D-amino acid at C(3), which correspond to the C(3) hydrogens of Im, may act repulsively in the active site and the repulsive energy may induce strain or distortion of the substrate and the enzyme, accelerating the catalytic reaction.

Animals↗

PubMed1991

The existence of two different forms of apo-electron-transferring flavoprotein.

The association process of FAD and apo-electron-transferring flavoprotein (apoETF) from hog kidney was investigated. The reaction schemes which involve the association-dissociation of the protein species could be excluded by the light scattering data, which indicated that the molecular weights of apoETF and holoETF are identical. The binding reaction between FAD and a large excess of apoETF was monophasic and obeyed pseudo-first order kinetics. On the other hand, the reaction between apoETF and a large excess of FAD was biphasic: the fast phase obeyed a pseudo-first order reaction, and the rate of the slow phase was almost independent of FAD concentration. These results suggest the existence of two different forms of apoETF, as represented in the following reaction scheme: [formula: see text] where "F" is FAD, "H" is holoETF, and "A" and "A" are the different forms of apoETF. The kinetic parameters were determined as k-1 = 3.9 x 10(4) M-1.s-1, k-1 approximately 10(-5) s-1, k+2 = 1.0 x 10(-3) s-1, and k-2 = 3.1 x 10(-3) s-1, in 50 mM potassium phosphate buffer, pH 7.6, containing 0.3 mM EDTA, and 5% v/v glycerol, at 7 degrees C. The elution patterns of apoETF on molecular sieve chromatography were very different from that of holoETF although the true molecular weights were identical. This result suggests that the structure of apoETF differs greatly from that of holoETF.

Animals↗

PubMed1991

A resonance Raman study on a reaction intermediate of Pseudomonas L-phenylalanine oxidase (deaminating and decarboxylating).

Resonance Raman (RR) spectra of purple intermediates of L-phenylalanine oxidase (PAO) with non-labeled and isotopically labeled phenylalanines as substrates, i.e., [1-13C], [2-13C], [ring-U-13C6], and [15N]phenylalanines, were measured with excitation at 632.8 nm within the broad absorption band around 540 nm. The spectra obtained resemble those of purple intermediates of D-amino acid oxidase (DAO). The isotope effects on the 1,665 cm-1 band with [15N] or [2-13C]phenylalanine indicate that the band is due to the C = N stretching mode of an imino acid derived from phenylalanine, i.e., alpha-imino-beta-phenylpropionate. The intense band at 1,389 cm-1 is contributed to by the CO2- symmetric stretching and C-CO2- stretching modes of alpha-imino-beta-phenylpropionate. The 1,602 cm-1 band, which does not shift upon isotopic substitution of phenylalanine, corresponds to the 1,605 cm-1 band of DAO purple intermediates and was assigned to a vibrational mode associated with the C(10a) = C(4a) - C(4) = O moiety of reduced flavin. These results confirm that PAO purple intermediates consist of the reduced enzyme and an imino acid derived from a substrate, and suggest that the plane defined by C(10a) = C(4a) - C(4) = O of reduced flavin and the plane containing H2+N = C - CO2- of an imino acid are arranged in close contact to each other, generating a charge-transfer interaction.

Amino Acid Oxidoreductases↗

PubMed1991

[Impairment of left ventricular diastolic function during the asymptomatic period in vasospastic angina patients without significant coronary stenosis].

We examined whether recurrent transient ischemia may effect left ventricular systolic and diastolic function or not. Left ventricular systolic and diastolic function during the asymptomatic period was studied by gated radionuclide ventriculography (RNV) in 25 patients with vasospastic angina (VA) who had no significant coronary stenosis, in 25 patients with effort angina (EA), and in 20 controls (C). There was no significant difference among patients in all three groups in regards to systolic indices (Ejection Fraction, Peak Ejection Rate). But diastolic indices (Peak Filling Rate, Time to Peak Filling Rate, 1/3 Mean Filling Rate, 1/3 Filling Fraction) were impaired not only in patients with EA but also in patients with VA. The treatment with nitrates and/or Ca antagonist for 6-24 months did not bring about any changes in these data concerning systolic and diastolic function in patients with VA. Thus, it is suggested that the diastolic function is impaired in patients with VA even during the asymptomatic period, though systolic function remains normal. Recurrent transient ischemia may cause irreversible myocardial injury.

Adult↗

PubMed1991

[Effect of age on visualization of right atrium by thallium-201 myocardial scintigraphy].

With Thallium-201 (Tl) myocardial scintigraphy, right atrial (RA) myocardium has been visible in the disease involving the right side of the heart. We have found RA visualization in the elderly patients without the evidence of right heart disease. Therefore, we studied the relation of age to the RA visualization with Tl myocardial scintigraphy performed at rest. Planar images of 291 patients without valvular or congenital heart disease were read by two observers and classified into the three by the degree of RA visualization; RA 0 = not visualized, RA 1+ = moderately visualized, RA 2+ = intensely visualized. The results were as follows: 93.1% of under 50 y.o., 77.8% of fifties, 86.7% of sixties, 50.5% of seventies and 36.7% of over 80 y.o. showed RA 0. 6.9% of under 50 y.o., 22.2% of fifties, 8.3% of sixties, 46.5% of seventies and 36.7% of over 80 y.o. showed RA 1+. None of under 60 y.o., 5.0% of sixties, 3.0% of seventies, and 26.6% of over 80 y.o. showed RA 2+. In conclusion, RA visualization in Tl myocardial scintigraphy, suggesting right heart overload, may increase with aging.

Aged↗

PubMed1991

[The clinical significance of reverse redistribution of Tl-201 SPECT at rest in the 1st month after the onset of acute myocardial infarction].

The pattern of Thallium-201 reverse redistribution (r-RD) at rest has been reported in some patients with acute myocardial infarction (AMI) in the acute phase. But there is no report of this pattern in the later phase. To investigate the significance of Thallium-201 reverse redistribution in the subacute phase, 37 patients with AMI underwent Thallium-201 SPECT at rest a month after the onset. The patients were classified into three groups visually and 19 of 37 patients (51%) showed the persistent defect pattern (Group PD), and the remaining 18 patients (49%) had the reverse redistribution pattern (Group r-RD). None of them had the redistribution pattern. Coronary reflow was earlier and the incidence of the scintigraphic overlap on Dual SPECT image of 99mTc-PYP/201TlCl in the acute phase was more frequent in Group r-RD than in Group PD. A decrease in thallium defect size of patients with r-RD from the acute phase to one month after the onset represented improvement more significantly than that with PD. Initial %Tl uptake of the infarcted region of Group r-RD was greater than that of Group PD. The degree of stenosis of the infarct-related coronary artery in Group r-RD was less severe than that in Group PD. And corresponding regional wall motion of Group r-RD was less impaired. The Thallium-201 washout in the infarcted region with r-RD was significantly faster than that in the normal region. It is concluded that the r-RD pattern at rest in the 1st month after the onset of AMI may be a sign of viable myocardium.

Aged↗

PubMed1991

[A prominent retrograde flow in coronary artery in patients with hypertrophic cardiomyopathy].

Pathophysiology and clinical significance of a systolic backward flow in the epicardial coronary artery have not been elucidated. Using a 20 MHz Doppler catheter, we assessed coronary flow velocity waveforms in the left anterior descending coronary artery in 19 patients with hypertrophic cardiomyopathy (HCM) and 11 patients without apparent cardiac abnormalities as control subjects. Systolic flow fraction was smaller in HCM than in controls. Only 4 patients with HCM showed a prominent retrograde flow persisting during almost the entire systole. All the 4 had marked cavity obliteration and two of them had systolic intraventricular pressure gradients of 80 and 110 mmHg respectively. Exercise thallium-201 ECT revealed that myocardial hypoperfusion was more frequent in those 4 patients. Through these observations, it is concluded that a high intramyocardial systolic pressure combined with a relatively low coronary perfusing pressure may result in a large systolic retrograde flow in the left epicardial coronary artery, and that it may be related to myocardial ischemia in patients with HCM.

Adult↗

PubMed1991

[Structure and expression of rig].

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Amino Acid Sequence↗

PubMed1990

Isolation and characterization of the human homologue of rig and its pseudogenes: the functional gene has features characteristic of housekeeping genes.

rig (rat insulinoma gene) was first isolated from a cDNA library of rat insulinomas and has been found to be activated in various human tumors such as insulinomas, esophageal cancers, and colon cancers. Here we isolated the human homologue of rig from a genomic DNA library constructed from a human esophageal carcinoma and determined its complete nucleotide sequence. The gene is composed of about 3000 nucleotides and divided into four exons separated by three introns: exon 3 encodes the nuclear location signal and the DNA-binding domain of the RIG protein. The transcription initiation site was located at -46 base pairs upstream from the first ATG codon. The 5'-flanking region of the gene has no apparent TATA-box or CAAT-box sequence. However, two GC boxes are found at -189 and -30 base pairs upstream from the transcription initiation site and five GC boxes are also found in introns 1 and 2. The gene is bounded in the 5' region by CpG islands, regions of DNA with a high GC content and a high frequency of CpG dinucleotides relative to the bulk genome. Furthermore, the human genome contains at least six copies of RIG pseudogenes, and four of them have the characteristics of processed pseudogenes. From these results together with the finding that RIG is expressed in a wide variety of tissues and cells, we speculate that RIG belongs to the class of "housekeeping" genes, whose products are necessary for the growth of all cell types.

Adenoma, Islet Cell↗