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Biomedical subjects

M Miyagawa

Publications and source records attributed to M Miyagawa.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Assessment of myocardial viability by thallium-201 reinjection imaging with sublingual nitroglycerin].

Although thallium-201 (201Tl) reinjection imaging improves the detection of myocardial viability compared to standard 3-4-hr redistribution (RD) imaging, it still underestimates the extent of viable myocardium. We examined whether 201Tl reinjection SPECT with sublingual nitroglycerin (NTG) had a higher sensitivity for viability detection than reinjection alone. Eighty patients with coronary artery disease were studied, 38 of them with an old myocardial infarction. At the peak of exercise, 111 MBq 201Tl was injected and the initial and the delayed SPECT images were obtained. Then, all patients were divided randomly into two groups, and in each group, SPECT data were obtained again after the injection of 37 MBq 201Tl with (NTG(+) group) or without 0.6 mg of sublingual NTG (NTG(-) group). Among 50 segments showing fixed defects on the delayed image in the NTG(+) group, 21 (42%) were found to be reversible on the reinjection image, as compared to 16 of 51 (31%) in the NTG(-) group. Twenty-two of 44 (50%) segments showing incomplete RD were found to be reversible in the NTG(+) group, while 17 of 42 (41%) segments in the NTG(-) group. Moreover, the ratio of reversible segments seen in the reinjection images was significantly higher in the collateralized regions of the NTG(+) group than in those of the NTG(-) group (20/26 vs. 14/28, p < 0.05). Thus, 201Tl reinjection SPECT with sublingual NTG improves the detection of ischemic but viable myocardium as compared to SPECT with reinjection alone.

Administration, Sublingual↗
PubMed1993

Atypical manifestations of tuberculous meningitis.

We describe 2 patients with tuberculous meningitis who exhibited unusual changes of their cerebrospinal fluid (CSF) which led to confusion in their management. Patient 1 was a 25-year-old man who displayed persistent polymorphonuclear dominant pleocytosis in his CSF. Autopsy revealed marked hypoplasia of the thymus and T cell areas of the lymph nodes, consistent with the Nezelof syndrome, as well as disseminated tuberculosis. Patient 2 was a 39-year-old woman who demonstrated, during appropriate antituberculous chemotherapy, an atypical exacerbation consisting of prolonged fever, polymorphonuclear dominant pleocytosis in her CSF and multiple cerebral infarcts. The neurological abnormalities in the patient underwent marked improvement following oral prednisolone therapy.

Adult↗
PubMed1992

Structural details of ribonuclease H from Escherichia coli as refined to an atomic resolution.

The crystal structure of RNase H from Escherichia coli has been determined by the multiple isomorphous replacement method, and refined by the stereochemically restrained least-squares procedure to a crystallographic R-factor of 0.196 at 1.48 A resolution. In the final structure, the root-mean-square (r.m.s.) deviation for bond lengths is 0.017 A, and for angle distances 0.036 A. The structure is composed of a five-stranded beta-sheet and five alpha-helices, and reveals the details of hydrogen bonding, electrostatic and hydrophobic interactions between intra- and intermolecular residues. The refined structure allows an explanation of the particular interactions between the basic protrusion, consisting of helix alpha III and the following loop, and the remaining major domain. The beta-sheet, alpha II, alpha III and alpha IV form a central hydrophobic cleft that contains all six tryptophan residues, and presumably serves to fix the orientation of the basic protrusion. Two parallel adjacent helices, alpha I and alpha IV, are associated with a few triads of hydrophobic interactions, including many leucine residues, that are similar to the repeated leucine motif. The well-defined electron density map allows detailed discussion of amino acid residues likely to be involved in binding a DNA/RNA hybrid, and construction of a putative model of the enzyme complexed with a DNA/RNA hybrid oligomer. In this model, a protein region, from the Mg(2+)-binding site to the basic protrusion, covers roughly two turns of a DNA/RNA hybrid double helix. A segment (11-23) containing six glycine residues forms a long loop between the beta A and beta B strands. This loop, which protrudes into the solvent region, lies on the interface between the enzyme and a DNA/RNA hybrid in the model of the complex. The mean temperature factors of main-chain atoms show remarkably high values in helix alpha III that constitutes the basic protrusion, suggesting some correlation between its flexibility and the nucleic acid binding function. The Mg(2+)-binding site, surrounded by four invariant acidic residues, can now be described more precisely in conjunction with the catalytic activity. The arrangement of molecules within the crystal appears to be dominated by the cancelling out of a remarkably biased charge distribution on the molecular surface, which is derived in particular from the separation between the acidic Mg(2+)-binding site and the basic protrusion.

Amino Acid Sequence↗
PubMed1992

The prevalence and prognostic significance of arrhythmias in Duchenne type muscular dystrophy.

To investigate the prevalence and prognostic significance of cardiac arrhythmias in Duchenne type muscular dystrophy 24-hour ambulatory ECG was performed in 80 patients with Duchenne type muscular dystrophy, and they were followed up for 5 years. Various arrhythmias were observed in 63.8% (51 of 80) of the patients. Ventricular premature beats were found in 30% (24 of 80), and the incidence of ventricular premature beats increased as the clinical severity of skeletal muscle involvement advanced. Forty-seven patients survived for 5 years, but the incidence of arrhythmias increased from 38.3% (18 of 47) to 74.5% (35 of 47) (p < 0.001). During the 5-year period, four of 33 deaths were sudden. Malignant ventricular premature beats (ventricular couplets, ventricular tachycardia, and R-on-T-type ventricular premature beats) were observed in three of these four patients. It appears that cardiac arrhythmias are a common complication of Duchenne type muscular dystrophy and that the incidence of ventricular arrhythmias increases with the progression of myocardial involvement. There is an association between ventricular arrhythmias and sudden death, but the reduction of ventricular arrhythmias may not reduce the incidence of episodes of sudden death.

Adolescent↗
PubMed1992

A 10-year follow-up study by orthogonal Frank lead ECG on patients with progressive muscular dystrophy of the Duchenne type.

A 10-year follow-up study by orthogonal Frank lead electrocardiography was performed on 25 patients with progressive muscular dystrophy of the Duchenne type (DMD). With advancing age, no apparent changes were observed in the duration and amplitude of the P wave or in the PR interval, whereas the duration of the QRS complex tended to increase. The amplitudes of the R wave in lead X (Rx) and lead Y (Ry) tended to decrease from 1.75 +/- 0.90 and 1.96 +/- 0.59 mV to 0.80 +/- 0.63 and 1.39 +/- 0.62 mV (p < 0.01), whereas the amplitude of the S wave in lead X tended to increase from 0.24 +/- 0.23 mV to 0.53 +/- 0.36 mV in 10 years after initiation of the study (p < 0.01). It is noteworthy that the Ry amplitude began to decrease markedly from the seventh year after the initiation of this study, whereas the Rx amplitude showed a gradual and unceasing decline through the 10-year period. Observation of the sequential changes of the QRS loops in three planes clearly demonstrated that the electrical force tended to decrease in the leftward and inferior directions and increase in the rightward direction. It is of interest that the frequency of occurrence of the deep Q wave was found to be quite high even in the early stages of DMD and that it did not display a direct relation to the sequential evolution of this disease. It can be concluded that observation of the sequential changes in the QRS complex allows estimation of the extent and direction of myocardial involvement in DMD.

Adolescent↗
PubMed1992

In vivo-in vitro replicative DNA synthesis (RDS) test using perfused rat livers as an early prediction assay for nongenotoxic hepatocarcinogens: I. Establishment of a standard protocol.

To establish a standard protocol for an in vivo-in vitro hepatocyte replicative DNA synthesis (RDS) test using male F344 rats for screening nongenotoxic (the Ames-negative) hepatocarcinogens, experimental conditions were examined. After treatment with three model hepatocarcinogens, isolated hepatocytes showed highest RDS incidences when plated at a density of 5 x 10(4) cells/ml. Spontaneous RDS incidences in hepatocytes from rats aged 9 weeks or older showed a constant value. The use of hepatocytes from 9-week-old rats at the 5 x 10(4) cells/ml plating density was therefore determined as the standard. Based on the distribution of mean spontaneous RDS incidences over 105 additional experiments (0.4 +/- 0.18%, with SEM), an RDS incidence of over 1% was adopted as the criterion for a positive response in our rat liver RDS test.

Age Factors↗
PubMed1992

In vivo-in vitro replicative DNA synthesis (RDS) test using perfused rat livers as an early prediction assay for nongenotoxic hepatocarcinogens: II. Assessment of judgement criteria.

To better establish in vivo-in vitro hepatocyte replicative DNA synthesis (RDS) test using male F344 rats as a screening assay for nongenotoxic (the Ames-negative) hepatocarcinogens, judgement criteria were assessed after single-gavage treatment with seven model compounds. The profiles of RDS induction by the compounds were analysed in terms of both time-course and dose-dependence. Our data reveal that a value of 2% or more for RDS incidence should be judged as positive and that of less than 1% RDS incidence as negative using maximum tolerance dose (MTD) concentrations in time-course experiments at 15, 24, 39, 48 and 63 h. In the case of an incidence value between 1 and 2%, the finding of a clear dose-dependence was considered to justify the conclusion of a positive effect for 1/4 MTD, 1/2 MTD, MTD and 2 x MTD at a fixed time. The established judgement criteria are planned for introduction in detection of nongenotoxic hepatocarcinogens (the Ames-negative carcinogens) using the RDS test.

Animals↗
PubMed1992

Optic nerve glioma in Japanese patients with neurofibromatosis 1. Case reports and literature review.

Case 1, a 6-year-old boy, had multiple café-au-lait spots, no light perception OS, Lisch nodules OU, pale optic disc OS, enlarged left optic nerve on computed tomographic scan and magnetic resonance imaging, and histopathologically verified pilocytic astrocytoma (glioma). The patient's mother had neurofibromatosis 1 (NF-1). Case 2, a 12-year-old boy, had multiple café-au-lait spots, decreased visual acuity OU, Lisch nodules OU, pale optic discs OU, enlarged optic nerves and chiasm on computed tomographic scan, and histopathologically verified pilocytic astrocytoma. We also examined 38 Japanese patients with NF-1 and found Lisch nodules in 95% and optic nerve glioma in 5%. After reviewing the recent literature, we found that the association of optic nerve glioma and NF-1 in the Japanese population was less than that reported in North America.

Adolescent↗
PubMed1991

Effects of chemical stimulation and lesion of the rostral ventrolateral medulla in spontaneously hypertensive rats.

We investigated whether or not the rostral ventrolateral medulla (RVL) participates in maintaining a higher arterial pressure of spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats (WKY) were anesthetized with chloralose, paralyzed with tubocurarine, and artificially ventilated. Chemical excitation of the RVL neurons by microinjection of excitatory amino acids (L-glutamate) elicited a dose-dependent pressor response in both the SHR and WKY groups. The magnitude of increase in the arterial pressure (AP) was similar in both groups, but the present increase of AP was higher in WKY than in SHR. Chemical lesions of the bilateral RVL produced by the microinjection of tetrodotoxin decreased the AP to the spinal level, which was similar in both groups. The results indicate that the RVL functions as the sole sympathetic output of the brain in SHR, and suggest that the RVL neurons may be tonically overactive to maintain hypertension in SHR.

Animals↗
PubMed1991

Dieulafoy's ulcer associated with the tortuous caliber persistent arteries: report of three cases.

Many papers have reported that Dieulafoy's ulcer is one of the notorious causes of gastric hemorrhage. Three cases of shallow subfundic ulcers with massive bleeding are reported. The resected specimens have demonstrated that elevated caliber-persistent artery (CPA), a branch of the left gastric artery with few anastomoses, in the base of the ulcer has tortuous penetration from the serosa to submucosa, showing patchy, eccentric intimal fibroelastosis. These findings of CPA are almost the same in both anterior and posterior walls, namely both the ruptured and contralateral sides. Thus, morphogenesis of the ulcer may have originated from anatomical deviation, which is related to regional hypertension aggravated by longterm peristalsis, as well as aging.

Aged↗
PubMed1991

Scintigraphic evaluation of myocardial uptake of thallium 201 and technetium 99m pyrophosphate utilizing a rat model of chronic doxorubicin cardiotoxicity.

To evaluate the usefulness of myocardial scintigraphy as a monitoring tool for chronic doxorubicin (DXR) cardiotoxicity, a rat model was used to investigate the relationship between the myocardial uptake of thallium 201 (Tl) or rechnetium 99m pyrophosphate (99mTc-PPi) and histological changes of the heart. Although there was no significant difference in myocardial Tl uptake between control and DXR-treated rats at an early phase after Tl injection, late-phase Tl uptake was significantly higher in the DXR-treated rats than in the control rats, indicating a slow wash-out of Tl from the myocardium. The wash-out rate calculated from scintigraphic examination of DXR-treated rats was significantly decreased with increasing degree of cardiomyopathy. Since the Tl wash-out rate was sharply decreased even in animals with minimal histological changes, it may be a possible monitoring tool for the early detection of chronic DXR cardiotoxicity. On the other hand, myocardial 99mTc-PPi images could be obtained only in rats with severe myocardial changes and hence would not useful for early detection.

Animals↗
PubMed1991

ECG-gated thallium-201 myocardial SPECT in patients with old myocardial infarction compared with ECG-gated blood pool SPECT.

We evaluated one of the merits of ECG-gated thallium-201 single photon emission computed tomography (g-T1 SPECT), i.e., the ability to appreciate left ventricular (LV) wall motion. LV wall motion assessed by g-T1 SPECT and by ECG-gated Blood Pool SPECT (g-BP SPECT) was classified into three grades and compared segment by segment. T1-201 uptake by g-T1 SPECT was also classified into three grades and compared with those of wall motion in g-BP SPECT. Fifty patients with prior myocardial infarction were injected intravenously at rest with 111 to 185 M Bq (3 to 5 mCi) of Tl-201. The left ventricular regions were divided into anterior, septal, inferior and lateral segments (50 patients X 4 segments = 200 segments in total). The grades of wall motion and Tl-201 uptake detected by g-Tl SPECT correlated well with those of wall motion in g-BP SPECT (94.5% and 85%, respectively). With g-Tl SPECT it was possible to evaluate left ventricular wall motion, providing clear perfusion images.

Adult↗
PubMed1991

Dietary sodium concentration modifies catecholamine release with stress in spontaneously hypertensive rats.

A high sodium diet increased the plasma norepinephrine (PNE) only in resting spontaneously hypertensive rats (SHR). SHR on either a high or low sodium diet showed a greater increase in arterial pressure (AP) than Wistar-Kyoto rats (WKY) with foot shock (FS). However, neither a high nor low sodium diet enhanced the increment of AP in both SHR and WKY with FS. Only a low sodium diet enhanced the increment of PNE and plasma epinephrine in SHR with FS. Extreme restriction of sodium intake might thus enhance the response of sympathetic activation with stressful stimuli.

Animals↗
PubMed1991

[Two cases of cardiac injuries due to nonpenetrating trauma of the chest].

Successful repair of nonpenetrating traumatic cardiac injury is uncommon. Two cases of nonpenetrating traumatic cardiac injuries from accident are reported. Case 1. Seventy eight year old man with shock was admitted to Iida City Hospital four hours after getting a bruise by a wood block on the anterior chest wall. Soon after his arrival ultrasonic cardiography was performed because of a doubt of cardiac trauma. And it revealed cardiac tamponade. Then the emergency operation was performed. After pericardial effusion was drained, rupture on the out-flow tract of the right ventricle was found and was successfully repaired without the aid of cardiopulmonary bypass. Case 2. Sixty five year old man with left heart failure was admitted to Iida City Hospital four months after getting a bruise on left chest and back from falling. Chest and back pain was reduced three weeks after the accident, however, shortness of breath was getting worse. Ultrasonic cardiography and aortography showed aortic regurgitation. Under cardiopulmonary bypass aortic valve replacement was performed. His aortic regurgitation was caused by perforation of non-coronary cuspid due to accident. Ultrasonic cardiography is useful to make a diagnosis of nonpenetrating traumatic cardiac injury. It is necessary to operate as soon as possible in cardiac rupture, and to select valve replacement for aortic regurgitation.

Accidents↗
PubMed1990

Three-dimensional structure of ribonuclease H from E. coli.

The three-dimensional structure of RNase H from Escherichia coli was determined at 1.8 A resolution by X-ray crystallography. The enzyme was found to belong to the alpha + beta class of structures, consisting of two distinct domains. The structure implies a possible region interacting with a DNA-RNA hybrid. The Mg2(+)-binding site essential for activity is located near a cluster of four acidic amino acids--one glutamic and three aspartic acid residues. These residues are completely conserved in the homology alignment of sequences of RNase H and reverse transcriptases from retroviruses and retrovirus-like entities. The structural motif of beta strands around the Mg2(+)-binding site has similarities to that in DNase I.

Amino Acid Sequence↗
PubMed1990

Plasma levels of atrial natriuretic peptide in patients with Duchenne's progressive muscular dystrophy.

To study the relationship between plasma alpha-atrial natriuretic peptide (alpha-ANP) and cardiac function in patients with Duchenne's progressive muscular dystrophy (DMD), we measured plasma alpha-ANP levels in 51 patients with DMD and evaluated them according to the clinical severity of the disease and the echocardiographic left ventricular function. In many of the patients with DMD, plasma alpha-ANP levels were mildly elevated, but no clear correlation was observed between alpha-ANP levels and wall motion abnormalities of the left ventricle. The alpha-ANP level was moderately or markedly elevated (81 to 120 pg/ml) in 3 of the 16 patients with respiratory failure and extremely high (1208 pg/ml) in the one patient with congestive heart failure. Two patients with respiratory failure and one with congestive heart failure, in whom alpha-ANP levels were elevated, died within 2 months. Elevation of left atrial pressure as a result of left ventricular dysfunction caused by impairment of the myocardium and elevation of right atrial pressure as a result of pulmonary hypertension caused by impairment of the respiratory muscles are considered to be involved in the mechanism of increased plasma alpha-ANP levels in patients with DMD. It can be concluded that a moderate or marked elevation in plasma alpha-ANP levels in patients with terminal DMD is a sign of a poor prognosis and may be a useful index for the management of the disease.

Adolescent↗