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R Okada

Publications and source records attributed to R Okada.

At least 163 records · Page 9Linked to original sources
PubMed1986

Age-related substantia nigra-mediated seizure facilitation.

We investigated the role of the GABAergic system of the substantia nigra in seizures of rat pups. Rat pups had bilateral cannulae implanted chronically either in the substantia nigra or 1.5 mm dorsal to it. At age 16 to 17 days, seizures were induced in the cannulated rats and naive (intact) controls by exposure to flurothyl following pretreatment with the GABA agonist, muscimol, or vehicle. Naive rats were the most resistant to flurothyl seizures. Bilateral nigral infusions of muscimol markedly facilitated the development of flurothyl seizures in a dose-response manner and differed significantly from the vehicle controls or rats infused with muscimol dorsally to the substantia nigra. In contrast, bilateral nigral muscimol infusions protected adult rats against the development of flurothyl seizures. Our data indicate that the effects of nigral GABA agonist infusions on seizures are age-dependent; the altered responsivity of the GABAergic nigral system in immature rats may be responsible in part for the increased seizure susceptibility of the developing central nervous system.

Animals↗
PubMed1986

Should the intent of testing influence its interpretation?

A test is often interpreted as "normal" or "abnormal" by a single criterion, regardless of the intent of testing. The discriminate accuracy of this convention was critically analyzed using information content (I), likelihood ratio and the area under the receiver-operating characteristic curve. Three ejection fraction variables were assessed--ejection fraction at rest, exercise ejection fraction and the change in ejection fraction from rest to exercise--each relative to three intentional goals: diagnosis of coronary artery disease in 929 patients without previous myocardial infarction, prediction of multivessel disease in these same 929 patients and prediction of multivessel disease in 507 patients with previous myocardial infarction. The information content of exercise ejection fraction (IEX) was higher than for ejection fraction at rest (IR) or for the change from rest to exercise (IEX-R), and was relatively constant regardless of the goal of testing. In contrast, neither IR nor IEX-R was constant. IR was lowest for diagnosis of coronary artery disease, whereas IEX-R was highest for this same goal. These empiric observations are consistent with the quantitative relation predicted by information theory: IEX = IR + IEX-R. Thus, ejection fraction at rest has little discriminate value relative to the diagnosis of coronary artery disease, but does have value in evaluating the extent of disease in patients after myocardial infarction. Exercise ejection fraction and change in ejection fraction are nearly equally useful for purposes of diagnosis, whereas the former is most useful for functional evaluation in postinfarction patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Histopathological study on the effects of aging in myocardium of hypertrophied hearts.

To clarify the effects of aging in myocardium of hypertrophied hearts, 555 autopsied hearts were studied histopathologically. Degrees of myocyte hypertrophy, disarrangement and fibrosis and lipofuscin deposits were estimated light-microscopically in tissue specimens taken from the anterior wall of the left ventricle. Myocyte hypertrophy was assigned to one of four classes from 0 to 3+ according to size. Other findings were estimated using the conventional three classes. All cases were divided according to heart weight, into the following groups: severe hypertrophy (Group I; more than 450 g for males and 400 g for females), mild hypertrophy (Group II; 450 greater than HW greater than 350 g for males and 400 greater than HW greater than 300 g for females) and no hypertrophy (Group III: less than 350 g for males and 300 g for females). Lipofuscin deposits increased with aging, but in Group I the increase was delayed in comparison to that in other groups. As a rule, myocyte size in the outer layer was equal to or smaller than that in the inner layer (outer-layer-selective atrophy). This was particularly true in pressure-overloaded hypertrophy and less so in volume-overloaded hypertrophy. Myocyte disarrangement was observed in the inner and median layers in the oldest group. Peri-vascular fibrosis became thick with aging, and perimysial fibrosis increased with age. The fibrotic process was accelerated in hypertrophied myocardium. As to the mode of hypertrophy, aging appears to result in a kind of myocardial asymmetry of layer-selective atrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Twenty year autopsy statistics of myocarditis incidence in Japan.

In the annuals of autopsy records in Japan, edited by the Japanese Society of Pathology and covering 20 years, from 1958 to 1977, 377841 autopsy cases are registered with a short summary of the pathology findings. Of these, 434 cases with idiopathic, interstitial, viral, non-specific (NSM) and giant cell (GCM) myocarditis were found. The incidences of NSM and GCM were 0.11 and 0.007%, respectively. The annual incidence of NSM showed periodic fluctuations with in 5-year intervals and increased remarkably after 1974. Incidence of GCM showed a similar fluctuation but with a one to two year delay of peaks. The male to female ratio was 1.2: 1 and the age distribution had two peaked patterns for both sexes, though these peaks were scattered widely from neonate to elderly patients. The regional distribution of NSM showed a concentration in the middle portion of Honshu and its regional annual incidence had propagation waves from the central area to peripheral areas. The same tendency was observed in GCM cases. Hokkaido was characterized by a low incidence of NSM and no GCM. Complications of myocarditis included pancreatitis, pneumonitis, interstitial nephritis, meningoencephalitis, hepatitis, hepatic cirrhosis and a considerable incidence of malignancies. Antibiotics, antineoplastic agents, steroids and irradiation therapy were the main forms of treatment applied before or after the start of myocarditis.

Adolescent↗
PubMed1986

Infantile hypertrophic cardiomyopathy with QT prolongation.

An infant who died at 5 months with hypertrophic cardiomyopathy accompanied by QT prolongation was examined at autopsy. At the age of 16 days, serum IgM level was elevated (226 mg/dl). Microscopic examination revealed characteristics of hypertrophic cardiomyopathy with myocardial cell hypertrophy with disarray and healed myocarditis with patchy fibrosis and mononuclear cell infiltration. The histological findings were compatible with those of postmyocarditic cardiomegaly developing during the fetal period.

Arrhythmias, Cardiac↗
PubMed1986

[Unusual cardiac hypertrophy in neonates with congestive heart failure: report of three cases].

We experienced three cases of unusual cardiac hypertrophy of the right ventricle or interventricular septum with severe congestive heart failure in the neonatal period. One patient had congenital heart disease consisting of membranous tricuspid atresia, absent pulmonary valve, patent ductus arteriosus, left single coronary artery and a hypoplastic pouch-like right ventricle. Very marked cardiac hypertrophy was observed in the right ventricle and interventricular septum. Histologically, there was no appreciable disorganization of the cardiac muscle. The etiology of the unusual hypertrophy of cardiac muscle in this patient is uncertain. The other two patients had asymmetrical septal hypertrophy of the left ventricle evidenced by two-dimensional echocardiography. Cardiac catheterization was performed for these two patients. There was no evidence of congenital heart disease; however, one patient had a significant pressure gradient in the outflow tracts of the left and right ventricles. These two patients' faces appeared unusual and they had minor anomalies of their fingers and ears. This unusual cardiac hypertrophy associated with cardiac anomalies and minor anomalies of the face and extremities comprise a specific type of cardiomyopathy in neonates. This should be distinguished from hypertropic cardiomyopathy of older children and adults.

Cardiomegaly↗
PubMed1986

[Pathologic aspects of mitral valve prolapse syndrome].

To comprehend clinical pictures of mitral valve prolapse syndrome (MVP), specific pathoanatomical knowledge is required. There is no definite structure of the anterior mitral valve ring. The mitral valve ring is not flat; the anterior segment of the ring tilts up superiorly. The number of scallops of the posterior leaflet depends on the definition of the incisura. The term "rough zone chorda" (Lam et al., 1970) is a misnomer. From the pathological point of view, more than two subgroups of MVP are present. In isolated MVP, pathological lesions are restricted to the local ballooned segment. However, in MVP with connective tissue disorders (for example, Marfan syndrome, etc.), the lesions are principally diffuse. Mitral valve changes in hypertrophic cardiomyopathy with obstruction are caused by torsion and the relatively elongated anterior leaflet due to narrowing of the mitral orifice, septal hypertrophy and displacement of the papillary muscles. MVP in atrial septal defect is caused by the turbulence of a large shunt flow or by the torsion of the mitral ring due to right ventricular volume overload. Further investigation of surgical and necropsied cases will be required to clearly the subgroups of MVP.

Cardiomyopathy, Hypertrophic↗