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Biomedical subjects

M Itaya

Publications and source records attributed to M Itaya.

At least 55 records · Page 3Linked to original sources
PubMed1991

Molecular cloning of a ribonuclease H (RNase HI) gene from an extreme thermophile Thermus thermophilus HB8: a thermostable RNase H can functionally replace the Escherichia coli enzyme in vivo.

A DNA fragment encoding Ribonuclease H (EC 3. 1.26.4) was isolated from an extreme thermophilic bacterium, Thermus thermophilus HB8, by its ability to complement the temperature-sensitive growth of an Escherichia coli rnhA deficient mutant. The primary amino acid sequence showed 56% similarity to that of E. coli RNase HI but little or no homology to E. coli RNase HII. Enzymes derived from thermophilic organisms tend to have fewer cysteines than their bacterial counterparts. However, T. thermophilus RNase H has one more cysteine than its E. coli homologue. Stability of the RNase H in extracts of T. thermophilus to elevated temperatures was the same for the protein expressed in E. coli. T. thermophilus RNase H should, therefore, be a useful tool for editing RNA-DNA hybrid molecules at higher temperatures and may also be stable enough to be used in a cyclical process. It was suggested that regulation of expression of the RNase H may be different from that of E. coli. RNase HI.

Amino Acid Sequence↗
PubMed1991

Complete physical map of the Bacillus subtilis 168 chromosome constructed by a gene-directed mutagenesis method.

All the SfiI sites and most of the NotI sites were located precisely on the chromosome of Bacillus subtilis 168 by a novel method, termed gene-directed mutagenesis. The stepwise elimination of these restriction sites by this method allowed not only the physical connection of the restriction fragments but also the accurate determination of the position of the restriction sites themselves. The resulting physical map of the 4165 x 10(3) base-pair B. subtilis chromosome has been correlated with the genetic map by determination of the exact location of known genes. The complete physical map provides a rapid and accurate way for mapping of new genes as well as analysis of large DNA rearrangements on the chromosome. The novel strategy is, in principle, applicable to the analysis of the genome of other organisms.

Bacillus subtilis↗
PubMed1991

A combination of RNase H (rnh) and recBCD or sbcB mutations in Escherichia coli K12 adversely affects growth.

Colony forming ability of Escherichia coli strains carrying the rnh-339::cat mutant allele is strongly dependent on the recBCD and sbcB genes. A mutation inactivating either the RecBCD nuclease or exonuclease I (sbcB) is sufficient to restrict severely the efficiency of plating of strains carrying the rnh-339::cat mutation. Combining a non-lethal temperature-sensitive mutation in the RecBCD nuclease, recB270 (Ts) or recC271 (Ts), with rnh-339::cat renders strains temperature sensitive for growth, even though rnh+ strains with the recB270 (Ts) or recC271 (Ts) alleles are viable at 42 degrees C. The recombinational functions of the RecBCD nuclease can be excluded as the source of lethality on the basis of the following observations. Introduction of a recombination proficient, exonuclease defective recD1009 allele or production of the phage lambda GamS protein (an inhibitor of the RecBCD exonuclease activity) in an rnh-339::cat strain dramatically delays or impairs the ability of such strains to form colonies. Restoration of recombination proficiency by inclusion of an sbcB15 mutation with recB21 recC22 mutations does not restore the ability of the rnh-339::cat mutant strains to plate normally. A recBCD+ strain bearing the rnh-339::cat and sbcB15 mutations forms very few visible colonies after 24 h but forms colonies at normal frequencies after 48 h of incubation. Finally, plating efficiencies of strains are unaffected when the RecBCD recombination pathway is inactivated by introduction of recA56 into an rnh-339::cat strain. These results imply that the defective growth of rnh-339::cat recBCD strains is due to a defect in repair and not recombination mediated by either the RecBCD or the RecF pathway.

Alleles↗
PubMed1991

Correlation of activity with phenotypes of Escherichia coli partial function mutants of rnh, the gene encoding RNase H.

The rnh gene of Escherichia coli encodes RNase H. rnh mutants display at least two phenotypes: (1) they require functional RecBCD enzyme for growth; thus rnh-339::cat recB270 (Ts) and rnh-339::cat recC271 (Ts) strains are temperature sensitive for growth; (2) rnh mutants permit replication that is independent of the chromosomal origin, presumably by failing to remove RNA-DNA hybrids from which extra-original replication can be primed. We report here that manifestation of these two phenotypes occurs at different levels of RNase H function; we have examined partially functional rnh mutants for their in vitro RNase H activity, their ability to rescue viability in recB or recC cells and their ability to permit growth of mutants incapable of using oriC [dnaA (Ts)].

Alleles↗
PubMed1991

Selective cloning of genes encoding RNase H from Salmonella typhimurium, Saccharomyces cerevisiae and Escherichia coli rnh mutant.

We have cloned genes encoding RNase H from Escherichia coli rnh mutants, Salmonella typhimurium and Saccharomyces cerevisiae. Selection was accomplished by suppression of the temperature-sensitive growth phenotype of Escherichia coli strains containing the rnh-339::cat and either recB270 (Ts) or recC271 (Ts) mutations. RNases H from E. coli and S. typhimurium contained 155 amino acid residues and differed at only 11 positions. The S. cerevisiae and E. coli RNases H were about 30% homologous. A comparison of the amino acid sequences of several RNases H from cellular and retroviral sources revealed some strongly conserved regions as well as variable regions; the carboxyl-terminus was particularly variable. The overlapping, divergent promoter gene organization found in E. coli was observed to be present in S. typhimurium.

Amino Acid Sequence↗
PubMed1990

Gene-directed mutagenesis on the chromosome of Bacillus subtilis 168.

We have devised a method whereby any mutagenized cloned DNA from Bacillus subtilis can be reinserted at the original site on the B. subtilis chromosome. The procedure depends on the accuracy and high frequency of homologous recombination between the B. subtilis chromosome and the DNA taken up by the cell. The method makes use of two drug resistance selection markers (the chloramphenicol resistance gene and the neomycin resistance gene) and a marker gene which functions as a catalyst. The utility of the method has been demonstrated using leuB and pro of B. subtilis as target gene and catalyst, respectively, and mutations such as leuB::cat, leuB-, and pro::neo constructed in vitro on the cloned DNA fragments. Transformation in sequential steps as (leuB+ pro+)----(leuB::cat pro+)----(leuB- pro::neo)----(leuB- pro+) resulted in a leuB- single mutant without affecting other regions of the B. subtilis chromosome (gene-directed mutagenesis). We also demonstrate that other single mutations such as metD- and pro-, as well as the double mutation leuB- pro- can be introduced by the same procedure. In principle, true isogenies with multiple mutations can be constructed by the method described in this paper. Furthermore, the procedure should be generally applicable to any organisms in which homologous recombination is proficient.

Bacillus subtilis↗
PubMed1990

Isolation and characterization of a second RNase H (RNase HII) of Escherichia coli K-12 encoded by the rnhB gene.

An additional RNase H (EC 3.1.26.4), RNase HII, has been isolated from Escherichia coli K-12. By screening a library of E. coli DNA for clones that suppressed RNase H deficiency of an E. coli rnh mutant, a clone was obtained that produced a protein with RNase H activity. The overexpressed RNase HIII protein in E. coli was purified to near homogeneity and exhibited a strong preference for the ribonucleotide moiety of RNA-DNA hybrid as substrate. The terminal 11 amino acids were determined and were identical to those predicted from the nucleotide sequence. The rnhB gene, which encodes RNase HII, was distinct from rnhA by its map position (4.5 min on E. coli genetic map, between lpxB and dnaE) and by the lack of significant amino acid sequence similarity. The presence of a second RNase H in E. coli indicates that multiple RNase H genes per genome is a general feature of a general feature of a wide variety of organisms.

Amino Acid Sequence↗
PubMed1990

The blasticidin S resistance gene (bsr) selectable in a single copy state in the Bacillus subtilis chromosome.

The blasticidin S resistance gene (bsr), originally isolated from Bacillus cereus, was studied in Bacillus subtilis. It was found that a 617 bp fragment including the intact bsr gene and its 5' flanking region could confer BS resistance on B. subtilis when integrated in its chromosome, even in a single copy state. The construction of a bsr gene cassette and its practical application as a novel selection marker for B. subtilis are reported.

Antifungal Agents↗
PubMed1986

[Left ventricular function in hypertrophic cardiomyopathy: a Tc-99m radionuclide angiographic study during exercise].

Hypertrophic cardiomyopathy (HCM) generally shows increased systolic function of the left ventricle at rest, although patients with HCM often have decreased exercise tolerance and develop dyspnea or chest pain. The present study was to investigate of left ventricular (LV) function during exercise in 26 patients with HCM using Tc-99m equilibrium angiocardiography, and to elucidate the mechanism of impaired functional reserve during exercise. Controls consisted of 11 normal volunteers and 12 patients with chest pain syndrome who had no abnormality on coronary arteriography or left ventriculography. In patients with HCM, LV ejection fraction decreased from 65 +/- 8 (mean +/- SD)% at rest to 59 +/- 18% at peak exercise, in contrast to an increase among controls (from 56 +/- 9% to 64 +/- 9%). As compared with resting values, cardiac output increased to 168 +/- 24% at peak exercise in HCM, but the increase was significantly less than that in controls (215 +/- 47%). Stroke volume decreased gradually to 83 +/- 16% during exercise in HCM, while it increased to 114 +/- 10% at an exercise level of half intensity, and it decreased slightly to 106 +/- 16% at peak exercise. LV end-systolic volume decreased among controls to 78 +/- 27% at peak exercise, but remained unchanged in HCM (118 +/- 58%). An increase in peak ejection rate at peak exercise was less in HCM than in controls (143 +/- 26% vs 170 +/- 42%). No significant differences were observed between the two groups concerning changes in indices of LV diastolic function including LV end-diastolic volume, peak filling rate or 1/3 filling rate during exercise. In the analysis of LV function curves, pulmonary arterial diastolic pressure increased to a greater extent in HCM than in controls (19 +/- 6 mmHg vs 11 +/- 6 mmHg); whereas, an increase in the stroke work index was less in HCM (80 +/- 26 g.m/m2/beat vs 121 +/- 21 g.m/m2/beat) at peak exercise. Thus, the LV function curve shifted downward and to the right in patients with HCM. The above findings indicate that LV functional reserve during exercise is impaired, especially as to systolic function in patients with HCM, while deterioration of diastolic function may be partly compromised by elevated filling pressure.

Cardiomyopathy, Hypertrophic↗
PubMed1985

Increased cardiovascular response to epinephrine in hypertrophic cardiomyopathy.

To study the role of catecholamines in the pathogenesis of hypertrophic cardiomyopathy (HCM), hemodynamic responses to low and high dose infusions of epinephrine (0.037 and 0.074 micrograms/Kg/min) were compared between 21 patients with nonobstructive HCM and 21 healthy controls, matched for age and sex. During low dose infusion, patients with HCM showed significantly greater responses (p less than 0.05) than controls in echocardiographic left ventricular (LV) end-systolic dimension (-8 +/- 1% vs -4 +/- 1%, mean +/- SEM), fractional shortening (12 +/- 2% vs 7 +/- 1%) and peak systolic velocity of the LV posterior wall (32 +/- 5% vs 15 +/- 4%), but the differences disappeared during high dose infusion. Thus, patients with HCM started to respond to epinephrine earlier than controls and seemed to have an increased sensitivity of beta-adrenergic receptors in the cardiovascular system. As the augmented responses were more evident in younger patients (less than 35 years) who manifested frequent familial occurrences of HCM, the increased sensitivity to catecholamine was postulated to be genetically determined and to be related to the abnormal myocardial hypertrophy of HCM.

Adolescent↗
PubMed1985

[Dysfunction of Carpentier-Edwards porcine mitral bioprosthesis causing a musical systolic murmur: a report of two cases].

Two patients with disruption of Carpentier-Edwards porcine mitral bioprosthesis presenting with a musical systolic murmur were reported. The two patients noted sudden development of a loud musical murmur 4 (Case 1) and 6.5 (Case 2) years after surgery. Case 1 had associated heart failure. Phonocardiogram disclosed a loud musical systolic murmur with regular vibrations at 230-240 Hz in Case 1, and 250-260 Hz in Case 2. In Case 1, echocardiography demonstrated fine fluttering of the porcine mitral valve at the same frequency as the murmur. Doppler echocardiography revealed characteristic Doppler signals from the porcine valves at a frequency of 250-300 Hz with several harmonics above and below the baseline. In addition, in Case 2, similar Doppler signals were obtained from the aortic walls, ventricular septum and posterior wall of the left ventricle. In both cases, left ventriculograms demonstrated grade 3 mitral regurgitation without paravalvular leakage, and at surgery, the porcine bioprosthesis showed a tear in one of markedly thinned cusps, without evidence of calcification. It was considered that a torn cusp was the source of the murmur, and this, in association with the resonance of the entire heart, produced the loud musical murmur. Thus, a musical systolic murmur is suggested to be one of important signs of dysfunction of porcine bioprosthesis.

Adult↗
PubMed1985

[Apical hypertrophy and its genetic and acquired factors].

Although apical hypertrophy is characterized by a spade-like configuration of the left ventricle and giant negative T waves on electrocardiograms, the identity of apical hypertrophy in the disease spectrum of hypertrophic cardiomyopathy (HCM) is not fully established. The present study compared the demography, familial occurrence, and acquired factors of 43 patients who had apical hypertrophy with those of 104 patients who had asymmetric septal hypertrophy (ASH). Demographically, apical hypertrophy occurred predominantly in middle-aged males (86%). Family surveys showed that 13% of siblings of apical hypertrophy were affected, significantly less than in obstructive (31%) or non-obstructive (29%) HCM with ASH. Thirty-eight percent of siblings of ASH patients less than 35 years of age were affected, with a male/female ratio of 4/5, suggesting an autosomal dominant inheritance. The acquired factors associated with apical hypertrophy were assessed in a case-control study. Relative risk (odds ratio) of the condition was 3.46 (p less than 0.05) in those with histories of hypertension, and increased further to 8.09 (p less than 0.001) in those who were often hypertensive according to their physician's evaluations. Thus a strong association of hypertension with apical hypertrophy was suggested. However, hypertension in this condition was usually mild and labile, the blood pressure reverted to the normal range within several days of hospital admission, implying that transient hypertension during daily activity is associated with apical hypertrophy. Therefore, blood pressure response during exercise stress tests of 25 patients with apical hypertrophy was compared with that of age- and sex-matched controls. Slopes of linear regression between systolic blood pressure and heart rate and oxygen consumption during exercise, were used as indices of blood pressure response. They were significantly greater in apical hypertrophy than in the controls (1.2 +/- 0.4 vs 0.9 +/- 0.3, p less than 0.01 and 4.3 +/- 1.7 vs 2.8 +/- 0.8, p less than 0.001). This trend was observed even in patients without histories of hypertension. These findings suggested that apical hypertrophy has an inheritance pattern different from that of ASH, and has a possible association with acquired factors such as hypertension. Therefore, apical hypertrophy seemed to be a disease entity distinct from HCM with ASH, though it might be included in the disease spectrum of HCM.

Adult↗
PubMed1984

[Mechanism of exercise-induced ST segment deviation in myocardial infarction: a 201T1-myocardial scintigraphic study].

Exercise-induced ST segment deviation was investigated using thallium-201 myocardial scintigraphy and correlated with coronary artery lesions in 25 patients with old myocardial infarction. Seven of eight patients without ST deviation showed no reversible perfusion defect by near maximal exercise, and six had no significant stenosis in the coronary arteries perfusing the non-infarcted area. During exercise, ST segment depression was induced in 12 patients and six of them developed a reversible perfusion defect in the non-infarcted area, associated with significant stenosis of the corresponding coronary arteries. Remaining six patients, however, did not show a reversible perfusion defect and four of them had no significant stenosis of the coronary arteries perfusing the non-infarcted area. In nine patients with exercise-induced ST segment elevation in leads with Q waves, a reversible perfusion defect was not detected in seven (78%) and five (71%) of them had no significant coronary artery stenosis as well. Four patients developed both ST segment elevation in leads with Q waves and ST segment depression in other leads. One patient who had significant coronary artery stenosis in the non-infarcted area and showed a reversible perfusion defect developed 1.5 mm ST elevation in II, III, a VF leads and 4 mm ST depression in precordial leads. In the remaining three patients who did not show a reversible perfusion defect and significant coronary artery stenosis in the non-infarcted area, ST depressions were less than 2 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Abnormal septal motion following non-surgical closure of the patent ductus arteriosus].

Abnormal ventricular septal motion is usually observed after open heart surgery, but its mechanism is not fully understood. Our previous study suggested that a sudden reduction of left ventricular (LV) volume overload after corrective surgery would be one mechanism, showing that postoperative abnormal septal motion is more frequent in patients who have preoperative LV volume overload. The purpose of this study was to investigate further the direct effect of LV volume alone on the ventricular septal motion in 22 patients who underwent non-surgical closure of a patent ductus arteriosus (PDA) by the Porstmann's method. The non-surgical closure of a PDA reduced LV diastolic diameter (LVDd) from 55.7 +/- 7.3 mm to 48.1 +/- 5.2 mm (P less than 0.001), and LV systolic diameter (LVDs) from 36.3 +/- 7.0 mm to 34.1 +/- 7.0 mm (p less than 0.01). Septal motion decreased in amplitude from 8.5 +/- 2.4 mm to 3.8 +/- 3.4 mm (p less than 0.01) and eight (36%) patients developed abnormal septal motion, while LV posterior wall excursions remained unchanged. When compared these eight patients with 14 without abnormal septal motion, the magnitude of postoperative LVDd reduction (delta LVDd) and its ratio to preoperative volume (delta LVDd/pre op LVDd) were significantly greater in patients with abnormal septal motion. Thus sudden reduction in LV volume overload alone could induce abnormal septal motion without altering other factors such as adhesion of the pericardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

[Hypertrophic cardiomyopathy with ventricular septal hypertrophy localized to the apical region of the left ventricle (apical ASH)].

Clinical and morphologic features are described in a subgroup of 22 patients with hypertrophic cardiomyopathy, who showed ventricular septal hypertrophy localized to the apical region (apical asymmetric septal hypertrophy: apical ASH). All patients had ventricular septal thickness of 17 mm or less with an average of 13 +/- 3 mm in the M-mode echocardiograms. In contrast, the two-dimensional echocardiograms demonstrated septal hypertrophy localized to the apical region, with an average septal thickness of 20 +/- 3 mm at the mitral valve and papillary muscle levels. On the left ventriculogram, 82% of patients with apical ASH showed inward concavity of the right-inferior wall of the left ventricle, indicating hypertrophy of the ventricular septum. However, no patient showed spade-like appearance of the left ventricle and only two showed giant T wave inversion exceeding 10 mm. Echocardiographic examination performed in eight affected relatives revealed typical asymmetric septal hypertrophy (ASH) in four relatives, one of them showing a resting pressure gradient of 30 mmHg in the left ventricle. The remaining four relatives showed similar apical ASH. When compared with patients of typical ASH, patients with apical ASH demonstrated significantly greater cardiac size, left ventricular end-diastolic pressure, left atrial and left ventricular diameters and significantly lower percent fractional shortening. Atrial fibrillation, B bump of the mitral echogram and heart failure were more frequent in this subgroup of patients. Thus, apical ASH appeared to be a part of the morphologic spectrum of hypertrophic cardiomyopathy with ASH and to be a separate disease entity from apical hypertrophy previously described in Japan. Severely impaired diastolic performances associated with mild to moderately depressed systolic function of the left ventricle were the characteristic clinical features of the subgroup of patients with apical ASH.

Adolescent↗
PubMed1983

Increased left ventricular function as an adaptive response in vibration disease.

Vibration disease results from the long-term use of vibrating tools. Vibration, noise, and cold are stressors that impair the human body, inducing vibration disease. From echocardiographic methods, the left ventricular ejection fraction in vibration disease was 79 +/- 4%, a significantly higher value than that in control subjects (75 +/- 6%) (p less than 0.01). The increase in ejection fraction appeared to be due mainly to an increase in left ventricular end-diastolic dimension. The value of the ejection fraction was proportional to the activity of the autonomic nerves. The stroke volume index in patients with vibration disease was also significantly larger than that in the control subjects (p less than 0.001). Electrocardiograms revealed a significantly lower heart rate at rest and an increase in the ratio of T waves to R waves in precordial lead V6. These data suggest that the cardiovascular system in patients with vibration disease provides an adaptive response to the stressors.

Adaptation, Physiological↗