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Biomedical subjects

R Okada

Publications and source records attributed to R Okada.

At least 109 records · Page 6Linked to original sources
PubMed1992

[Vagal innervation in the human atrioventricular valves].

Innervation of the human atrioventricular (AV) valves is microscopically studied by histopathological methods. The tricuspid and mitral valves of 4 autopsied hearts of adult men (age range from 50 to 74 years old) without any cardiovascular diseases were stained for acetylcholine-esterase by histochemical method in the medium containing acetylthiocholine iodide. Acetylcholine-esterase positive nerve fibers of 2 to 50 microns in diameter were widely distributed in the subepicardial space of the atrial of the AV valve. They formed a coarse network of the nerve elements from the valve base to the anatomical edge. The nerve network was more dense at the valve ring and base, as well as at the commissure, than at the edge and body. Some thick nerve fibers ran in the chordae tendineae. The thick fibers were intercalated with varicose-like special structures at several places in the leaflets, which seemed to be a kind of sensory apparatus. The thin nerve fibers ended, as usual, at small dot or brush-like apparatus. It is widely accepted that the acetylcholine-esterase positive nerve fibers are identical with vagal nerves which are insisted on participating in development of mitral valve prolapse syndrome. We suggest that the vagal innervation in the AV valves could play an important role for valvular function.

Acetylcholinesterase↗
PubMed1991

Loss of dendritic synapses in the medial amygdala associated with kindling.

Kindling stimulation was given in the basolateral amygdala (BLA), the septal area or the corpus callosum in the right hemisphere of adult rats. The density of dendritic synapses was electron microscopically studied in the medial amygdaloid nucleus (MAN) ipsi- and contralateral to the stimulation side. The number of dendritic synapses was markedly decreased in both sides of the MAN of 3 groups of kindled rats. Such reduction occurred in both dendritic shaft and spine synapses. The most remarkable decrease was obtained in the BLA kindling. These results suggest that a decrease of synapses may provide a morphological basis for kindling.

Amygdala↗
PubMed1991

A histopathological study of age-related changes of the left bundle branch in the human heart.

To study age-related changes in the left bundle branch (LBB), 32 autopsied hearts were examined histopathologically using serial sections according to the method of Lev. Each division of LBB was carefully studied, i.e., the anterior and posterior radiations and the proximal, middle, and distal portions of radiations. An increase of fibrosis and fatty infiltration were observed in the LBB with aging. There was a tendency for fibrosis to be more prominent in the proximal LBB at the site of transition from bundle branch cells to Purkinje cells.

Adipose Tissue↗
PubMed1991

[Pathology of the cardiac valves].

The cardiac valves develop from the endocardial cushions of the fetus. Some congenital anomalies such as the 21-trisomy syndrome (Down syndrome) show poorly differentiated immature valves similar to those under development. The normally mature valves have four layers of the connective tissue, i.e., proximalis, spongiosa, fibrosa and distalis. Gargoylism promotes abnormal thickening of collagen fibers in the fibrosa via acid-mucopolysaccharide (aMPS) overproduction, but Marfan syndrome weakens the valves in spite of increased aMPS. The reversed conditions could be caused by the difference of increased aMPS; i.e., dermatan sulfate B or heparitin sulfate in gargoylism, on the contrary, dermatan sulfate A and C or hyaluronic acid in Marfan syndrome. Hemodynamic changes in the valves consist of diffuse hypertrophy of the proximalis and fibrosa in high flow cases and focal thickening of the proximalis at the line of closure and of the spongiosa at the anatomical edge in high pressure cases. Aging of the valves simulates partly the hemodynamic changes but degeneration of collagen fibers in the fibrosa after consumption of the spongiosa is more prominent than the latter. So-called myxomatous degeneration in the mitral valve prolapse cases seems reactive hypertrophy of the spongiosa replacing the interrupted fibrosa. Spontaneous chordal rupture is partly related to myxomatous change, but that in the elderly cases shows only simple disruption of collagen fibers with loss of the spongiosa tissue. Calcification of the valvular rings and bodies often observed in the elderly cases with parallelism to degeneration of the connective tissue produces mitral regurgitation, aortic stenosis or both, showing a preponderance of females.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1991

[Evaluation of myocarditis using T1-201 myocardial scintigraphy with bull's eye functional map].

In order to evaluate myocardial damage in a patient with myocarditis, rest thallium-201 myocardial single photon emission computed tomography (SPECT) was performed in 15 patients with myocarditis. For qualitative and semiquantitative analysis, Bull's eye functional maps were made up with SPECT images. In the functional map, the abnormal area, where T1 uptake is less than mean-2SD of the T1 uptake of normal subjects, is generally distributed in the myocarditis group. But focal and sequential abnormal areas were recognized more often in the clinically severe cases. Abnormal area tended to be observed commonly at the antero-septal wall, but it was uncommon at the lateral wall. Extent score, i.e. degree of extension of abnormal area, and severity score, i.e. degree of abnormality, were in good negative correlation with left ventricular ejection fraction (r = 0.6, r = 0.7). Furthermore, existence of abnormal area was in good correlation with the left ventricular regional wall motion. Abnormal area existed 100% in the akinetic region, 71% in the region of severe hypokinesis, and 27% in the region of hypokinesis. Abnormal area occupied 30% of the normokinetic region in the myocarditis group, which was a higher rate than in the normal control group (p less than 0.05). It was suggested that latent myocardial damage existed in the normokinetic myocardium with myocarditis. Thus, rest T1-201 SPECT with Bull's eye map is useful for clinical diagnosis in patients with myocarditis.

Adolescent↗