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Biomedical subjects

K Hirosawa

Publications and source records attributed to K Hirosawa.

At least 163 records · Page 9Linked to original sources
PubMed1982

Detection of mitral ring abscess by two-dimensional echocardiography.

M-mode and two-dimensional echocardiographic features of mitral ring abscess are described. A round, dense echo mass between the posterior mitral leaflet and left ventricular posterior wall was demonstrated in long- and short-axis views of the left ventricle. The diagnosis of mitral ring abscess was confirmed at surgery. The superiority of two-dimensional echocardiography over M-mode echocardiography for evaluating patients with mitral ring abscess is also discussed.

Abscess↗
PubMed1982

Long-term follow-up of electrocardiographic findings in patients with acute myocarditis proven by endomyocardial biopsy.

Sixteen cases of acute myocarditis, proven by endomyocardial biopsy, of possible viral origin which were described in a previous paper have been followed up for up to 5 years. The cases were divided into 3 groups according to the electrocardiographic (ECG) patterns: with conduction disturbance at the early stage (Group I, 9 cases), without conduction disturbance (Group II, 4 cases); early death cases in which the follow-up could not be carried out (Group III, 3 cases). In Group I, 2 cases revealed persistent complete A-V block, 4 showed incomplete recovery of right bundle branch and/or fascicular blocks, and 3 showed complete recovery of the ECG abnormalities. In Group II, all 4 cases showed a pseudoinfarction pattern which consisted of abnormal Q waves, poor R wave progression and ST elevation. These findings disappeared during the follow-up period. All patients of Groups I and II are still alive after a follow-up period of up to 5 years.

Acute Disease↗
PubMed1982

Spectrum of the infective endocarditis in the past five years.

One hundred and thirty patients at our Heart Institute with infectious endocarditis during the past 5 years were reviewed to provide an overview of the spectrum of infective endocarditis and to assess the accuracy of echocardiography in detecting the infective valvular and endocardial lesions. Of the 130 patients, 36 (28%) had the previous cardiovascular surgery. The mean age of the patients was 34 years, and only 11% of the patients were over 50 years of age. Of the 94 patients who had no cardiovascular surgery before developing infective endocarditis, 6 underwent urgent surgery, 49 had elective surgery and the remaining 39 were followed up with medical treatment. The mortality rate of the 55 patients who were operated on was 5.5% as against 18.0% in 39 without surgery. Half of the 36 patients who had been operated on before developing endocarditis had prosthetic valves inserted. Of the 5 patients with bioprosthetic valve endocarditis, only one survived as a result of prompt medical and surgical treatment. Streptococci were still commonly found, about 75% in the group without surgery and 50% in the group with surgery. Gram-negative bacilli and fungi were found in patients with prosthetic valve endocarditis. In 61 patients, morphologic abnormalities confirmed at surgery or necropsy were compared with the preoperative echocardiograms. Vegetations were identified preoperatively in 50 (95%) of the 53 valves involved, and valve destruction was correctly predicted in all 23 cases. Mycotic aneurysm was detected preoperatively in only 3 of the 12 patients in whom it occurred. Thirteen patients, in whom vegetation was recorded, were treated successfully with antibiotics alone and they needed no surgical intervention during the 2-year follow up period. The presence of a vegetation in an echocardiography does not necessarily require surgical intervention in itself or predict the ultimate course.

Adolescent↗
PubMed1981

Ultrastructure of the crayfish stretch receptor in relation to its function.

The crayfish slow-adapting abdominal stretch receptor was fixed under the relaxed or stretched condition. During this procedure action potentials of the sensory neuron were recorded by a suction electrode. The receptor organ consists of a receptor muscle and a sensory neurons with its dendrites embedded in the connective tissue zone in the receptor muscle. From the cell body of the neuron, several "primary dendrites" arise, branch successively into "dendritic branches", and finally terminate as "dendritic tips," which are cylindrical processes of fairly uniform diameter. In contrast to the primary dendrites and the dendritic branches, the dendritic tips have neither mitochondria nor sheaths and are embedded in the connective tissue zone or apposed to the receptor muscle with a gap of about 15 nm. Microtubules and smooth ER are seen in all parts of the dendrites. When the receptor is stretched and then fixed with 1.6% glutaraldehyde in 0.12 M phosphate buffer (total osmolarity of this solution is isosmotic with the physiological solution), dendritic tips became more parallel to the long axis of the receptor muscle and showed marked deformation consisting of alternate regions of swelling and shrinkage, resulting in a bead-like appearance. When fixed with 1.6% glutaraldehyde in 0.2 M phosphate buffer (total osmolarity of this solution is hyperosmotic), the dendritic tips showed less tendency toward such deformation. These results suggest that the dendritic tip membrane is susceptible to stretch and might be the region where the generator potential is produced.

Animals↗
PubMed1981

Freeze-fracture study of the crayfish stretch receptor.

The crayfish slow-adapting stretch receptor was fixed under relaxed or stretched conditions (twice the relaxed length) and then processed for freeze-fracture study. The sensory neuron membrane had evenly distributed intramembrane particles mostly on its P face. The density of these particles was higher in the cell body than in the dendritic tips, which are the terminal portions of the dendrites. The dendritic tips were cylindrical under the relaxed condition and showed deformations with stretch stimuli. When they were fixed under the stretched condition with 1.6% glutaraldehyde in 0.12 M phosphate buffer (the total osmolarity of this fixative is isosmotic with the physiological solution), the dendritic tips showed regional swelling and shrinkage. The intramembrane particle density of the swollen parts decreased and there were particle-free patches of membrane, whereas the particle density of the shrunken parts increased. On the other hand when the receptor was fixed with 1.6% glutaraldehyde in 0.2 M phosphate buffer (the total osmolarity is hyperosmotic but buffer osmolarity is isosmotic), the diameter of the dendritic tips became smaller, and their membrane particle densities were almost the same as that under the relaxed condition. The sheath cells covering the sensory neuron were characterized by their sheet-like profiles, gap junctions, and crater-like protrusions. The receptor muscle membrane had longitudinal foldings, occasional invaginations, peripheral couplings, string-shaped particle aggregates, and band-shaped particle aggregates.

Animals↗
PubMed1981

Thin-section and freeze-fracture studies of crayfish stretch receptor synapses including the reciprocal inhibitory synapse.

The crayfish slow-adapting abdominal stretch receptor organ is innervated by three inhibitory and several excitatory axons. A previous study by Tisdale and Nakajima ('76) showed that under certain fixation conditions inhibitory and excitatory synapses can be distinguished on the basis of synaptic vesicle structure. Using this morphological criterion we describe six types of synapses in the receptor: (1) the inhibitory axo-dendritic synapse, (2) the excitatory neuromuscular synapse, (3) the inhibitory neuromuscular synapse, (4) the axo-axonic synapse which suggests presynaptic inhibition of the excitatory synapse, (5) the axo-axonic synapse which suggests presynaptic inhibition on the inhibitory synapse, (6) the reciprocal inhibitory axo-axonic synapse, which is a new type of synapse. The presence of these six types of synapse suggest that inhibitory and excitatory axons interact synaptically in a complicated manner, resulting in a delicate control of receptor function. In freeze fracture we have observed the presynaptic membrane structures of inhibitory and excitatory synapses. The active zone of the inhibitory synapse has ridges with loosely aggregated particles on the tops of the ridges and indentations (vesicle attachment sites) along their sides. The active zone of the excitatory neuromuscular synapse consists of bands of particle aggregates which are situated on slightly elevated membrane regions and surrounded by wide, relatively particle-free, flat membrane areas.

Animals↗
PubMed1981

Localization of tritiated vitamin A in lymph nodes of the mouse: an autoradiographic study of vitamin A-storing cells.

Localization of tritiated vitamin A in lymph nodes of the mouse was investigated by the use of light- and electron-microscopic autoradiography. Young male mice were fed a diet containing 3H-vitamin A acetate for a week. Lymph nodes were removed and prepared for autoradiography. Lipid droplets in fibroblast-like cells showed high concentrations of radioactivity. These cells were distributed around lymphatic sinuses and blood vessels. The cells can, therefore, be classified as "vitamin A-storing cells" according to criteria proposed earlier by Yamada and Hirosawa (1976). Control animals from the same litter were maintained on ordinary laboratory food for the same period and examined by electron microscopy. Lipid-droplet-containing cells were found in the same areas as in the experimental animals but in fewer numbers. This suggests that the increased number of vitamin A-containing lipid droplets is due to hypervitaminosis A in the experimental animals. The presence of some cells containing these droplets in the control animals would imply that even under normal feeding conditions the animals ingested excess amounts of vitamin A, which was retained in lipid droplets. The stored vitamin A probably participates in metabolic processes such as the formation of glycoproteins in ground substance.

Animals↗
PubMed1981

Early clinical profiles of cases with histopathologically proven acute idiopathic myocarditis and a proposal for diagnostic criteria.

The early clinical features, primary care, treatment and short-term prognosis in 15 cases of acute myocarditis where diagnostic confirmation was made by endomyocardial biopsy or autopsy were analyzed. Characteristically, idiopathic myocarditis of possible viral etiology revealed preceding symptoms which consisted of flu-like symptoms, i.e., fever, upper respiratory infection (sore throat, cough), myalgia or arthralgia, general malaise, and gastrointestinal disorders (vomiting, anorexia, nausea, abdominal pain and soft stool). A severe cardiac or generalized disease condition may follow. Depending upon the progress of intensive medical and cardiac care, the patients' prognosis is not always poor. Diagnostic criteria based upon our own experience have been constructed as a proposal.

Acute Disease↗