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Biomedical subjects

T Shimono

Publications and source records attributed to T Shimono.

At least 19 recordsLinked to original sources
PubMed1992

[Left atrial myxomas: clinical characteristics, evaluation and considerations in classifying tumors].

Eleven patients underwent surgical excision for left atrial myxomas. Clinical symptoms, coronary angiographic findings and operative procedures were evaluated. Myxomas were classified into two types based on macroscopical findings, and clinical characteristics of these two types were analyzed. Seven cases (64%) classified as "lobular-type myxomas" were seen as lobulated, gelatinous and fragile. Four cases (36%) were classified as "round-type myxomas" were round and elastic soft. Primary symptoms included dyspnea on exertion in five cases (45%) and neurological disturbances in six cases (55%). Brain emboli were found in four patients by CT scan, and were classified as lobular-type myxomas. These eleven myxomas successfully removed in all cases. Four of these myxomas, which were pedunculated with fine fibrous stalks, were shaved along the base at the atrial septum or free wall. Others were excised completely along with a portion of the adjacent septum. Microscopic examination of the operative specimens revealed that two lobular-type myxomas with broad-based attachment to left atrial septum had invaded the atrial septum. All patients are doing well and have had no signs of myxoma recurrence at postoperative periods ranging from 10 months to 12 years (mean follow-up 5.3 years). Seven patients underwent selective coronary angiography due to a diagnosis of a coronary artery disease. All coronary angiograms were normal in all cases. In five (71%) of these seven, abnormally dilated atrial branches were seen as supplying the tumor. In two cases with round-type myxomas, neovascularity was evident and was made up of clusters of tortuous vessels with tumor blush.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[Reconstructive surgery for mitral regurgitation caused by degenerative disease--indications for expansion and early clinical outcomes].

Between January 1983 and June 1990, there were 48 patients who underwent surgery for mitral regurgitation due to degenerative diseases. Among these, 20 patients received mitral valve repair. Overall operative mortality was 5% for patients who underwent valve repair, and 7.1% for those who underwent valve replacement. We standardized a maneuver for valve repair in August 1988 in an attempt to expand its indications. There were 35 patients who underwent surgery prior to that date (group 1), and 13 patients after that date (group 2). There were nine patients (25.7%) in group 1 and 2 patients (84.6%) in group 2 who underwent valve repair. Among these, one patient (11%) in group 1 died within 30 days after the operation, but there were no surgical deaths for any patients in group 2. In addition, one patient (11%) in group 1 and one (9%) in group 2 required another operation for valve replacement. Doppler echocardiographic studies performed postoperatively in 18 patients who had undergone valve repair showed that 13 (72.2%) had no regurgitation, 4 (22.2%) had trivial regurgitation, and 1 (5.6%) had mild regurgitation. Postoperative valve area as determined by continuous-wave Doppler echocardiography was 3.7 +/- 1.1 cm2 (mean +/- SD) for patients who had undergone reconstruction and 3.1 +/- 0.7 cm2 for those who had undergone replacement.

Adolescent↗
PubMed1992

[Clinical evaluation of treatment for prosthetic valve endocarditis and analysis of factors affecting outcome of surgical therapy].

We analyzed the outcome for 18 patients with prosthetic valve endocarditis (PVE) treated between 1965 and 1990, 17 of whom had undergone valve replacement with mechanical prosthetic valves and one of whom had a bioprosthesis. Two patients developed infection within 60 days after surgery, and 16 thereafter. Fifteen patients received combined medical and surgical therapy and three medical therapy. In 14 patients, surgery had been performed during active infection. Mortality rate of those who had received combined medical and surgical therapy was 27%, and that of those who had received medical therapy was 67%. At operation, para-annular abscess was around the mitral prosthesis was found in three patients and around the aortic prosthesis in eight. Seven patients required reoperation for postoperative paravalvular leakage, in six, para-annular abscess had been found at the operation for PVE, and in one para-annular abscess had been noted. One patient who had undergone reoperation had developed reinfection after the first surgery and died due to multiple organ failure after the second operation (Danielson's translocation technique). In one patient who had complete loss of supporting tissue because of severe para-annular abscess, we had performed aortic valve replacement by implanting the aortic valve prosthesis into the left ventricle with Dacron felt-supported sutures placed in the mitral annulus and the muscles of the left ventricular outflow tract. This patient showed no postoperative infection or no paravalvular leakage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1978

Electrophysiological studies of two types of thalamo-cortical neurones and their responses to stimulation of mesencephalic reticular formation.

1. Thalamo-cortical (T-C) neurones projecting their axons to the motor cortex were recorded intra- or extra-cellularly in the anterior ventral and lateral ventral nuclear complex of the thalamus in lightly nembutalized cats. The T-C neurones were identified as responding antidromically to stimulation of the motor cortex, and were examined in connection with effects of stimulation of the centrum medianumparafascicular complex (CM), pallidum (Pal), cerebellar nuclei (CN) and mesencephalic reticular formation (RF). 2. The T-C neurones were classified into two groups, A and B. The A-group neurones responded neither to stimulation of CM nor to that of Pal. By contrast, the B-group neurones were activated from either CM, Pal or both. The effect of RF stimulation was facilitatory in many of the A-group neurones whereas it was mostly inhibitory in the B-group neurones. CN stimulation activated most of the T-C neurones in both A and B groups. 3. The A-group neurones were categorized as the deep T-C neurones mediating the deep T-C response of the cortex (the early surface-positive-deep-negative component of the augmenting response) and the B-group neurones as the superficial T-C neurones mediating the superficial T-C response of the cortex (the recruiting response and the late surface-negative-deep-positive component of the augmenting response). Desynchronization of electrocorticograms in response to RF stimulation was suggested to result from inhibition of the superficial T-C neurones and facilitation of the deep T-C neurones.

Action Potentials↗
PubMed1977

Immunoadjuvant activities of synthetic 6-O-acyl-N-acetylmuramyl-L-alanyl-D-isoglutamine with special reference to the effect of its administration with liposomes.

Addition of a lauroyl, stearoyl or docosanoyl group to the primary hydroxy group at the C-6 position of N-acetylmuramyl-L-alanyl-D-isoglutamine gave lipophilic derivatives that had definite adjuvancies in induction of delayed-type hypersensitivity and enhancement of antibody production against a test protein antigen, ovalbumin, when administered to guinea pigs as liposomes, that is without mineral oil. When administered as mineral oil-in-water emulsion, including Ribitype emulsions, rather than as water-in-mineral oil emulsions, N-acetylmuramyl-L-alanyl-D-isoglutamine and its 6-O-acyl derivatives showed only weak immunoadjuvancies.

Adjuvants, Immunologic↗
PubMed1976

Effects of stimulation of the midbrain reticular formation upon thalamo-cortical neurones responsible for cortical recruiting responses.

1. In lightly nembutalized cats, effects of high frequency (60-100/sec) repetitive stimulation of the midbrain reticular formation (RF) were tested upon the thalamo-cortical (T-C) neurones which project from the anterior ventral (VA) nucleus of the thalamus and its vicinities to the parietal association cortex and convey impulses responsible for cortical recruiting and spindling-like responses. 2. Tonic maintained or rhythmic grouped firings of the T-C neurones recorded as extracellular units with microelectrode in the thalamus were in the majority suppressed by high frequency RF stimulation during and often for a short time after the stimulation, and they showed later tonic discharges for many seconds or minutes. Intracellular recording from the T-C neurones revealed hyperpolarizing potential changes corresponding to the suppression on high frequency RF stimulation. Field potential analysis in the VA nucleus indicated that the hyperpolarization is ascribed at least in part to IPSPs elicited in the T-C neurones. Responses in some other types of thalamic neurones to the RF stimulation were exemplified to be compared and related with those of the T-C neurones. 3. Desynchronization of the parietal electrocorticogram coincided with the suppression of the T-C neurones and lasted for the time of the later tonic discharges, which contrasted with the rhythmic grouped discharges of the T-C neurones in association with recruiting and spindling-like responses of the cortex. Relations between the thalamo-cortical recruiting system and the ascending reticular activating system were discussed.

Animals↗
PubMed1976

Electrophysiological study on the postnatal development of neuronal mechanisms in the rat cerebellar cortex.

(1) Functional commencements of the neuronal elements in the cerebellar cortex of young rats were studied electrophysiologically by means of laminar field potential analyses in the cortex on stimulation of the cerebellar surface (Loc) and the white matter (WM). (2) The antidromic action potential of Purkinje cells on the WM stimulation was observed at one day after birth. The climbing fiber excitation of Purkinje cells on the stimulation was noted at 3 days after birth. (3) The mossy fiber-granule cell synapses were found to function at 10 days after birth and the Golgi cell inhibition of granule cells could be proved at the same time. The excitatory action of parallel fibers and the inhibitory action of basket-stellate cells on Purkinje cells appeared simultaneously at about 12 days after birth. The transverse distribution across the cerebellar folium of the basket-stellate cell inhibitory action on Purkinje cells was found to be narrow up to 60 days after birth. (4) These results concerning the dates of commencement of excitatory and inhibitory synaptic actions in the cerebellar cortex were compared with those of synaptogenesis studied morphologically, and some implications of the dates in the functional development of the cerebellar cortex were discussed.

Animals↗
PubMed1976

Preparation of various fractions from Mycobacterium smegmatis, their arthritogenicity and their preventive effect on adjuvant disease.

Cell walls of Mycobacterium smegmatis were able to produce much more severe arthritis in rats than the delipidated cells, whereas cell envelope and cell membrane fractions were unable to produce the disease. The lysozyme-solubilized product was able to produce mild disease with only 30% of incidence with an optimum dose, whereas the higher and the lower doses did not produce the disease. The rats immunized with cell envelope, cell membrane fraction and nonarthritogenic doses of lysozyme-solubilized product were protected against the subsequent homologous and heterologous challenge of delipidated cells. It was discussed that this preventative effect can be the result of antigenic competition between the arthritogenic and nonarthritogenic components of M. smegmatis. On the other hand, all the fractions separated here were able to serve as an immunoadjuvant in terms of inducing delayed hypersensitivity to ovalbumin in guinea pigs.

Animals↗
PubMed1976

Correlation between the immunoadjuvant activities and pyrogenicities of synthetic N-acetylmuramyl-peptides or -amino acids.

A total of 14 different N-acetylmuramyl-peptides or -amino acids with or without configurations inherent to bacterial cell wall peptidoglycans were synthesized and their pyrogenicities on intravenous injection into rabbits were tested. N-Acetylmuramyl-peptides, and especially N-acetylmuramyl-L-alanyl-D-isoglutamine and N-acetylmuramyl-L-alanyl-D-isoglutaminyl-L-lysine, which were previously shown to be adjuvant-active in both induction of delayed-type hypersensitivity and stimulation of increased serum antibody levels to ovalbumin in guinea pigs, exhibited distinct pyrogenicity at as low dose as 16 mug per rabbit. However, none of the adjuvant-inactive analogues or diastereomers of the above N-acetylmuramyl-dipeptide or related compounds caused any significant febrile response in rabbits, even at a dose of 250 mug per animal.

Adjuvants, Immunologic↗
PubMed1975

Electrophysiological studies of the projections from the parietal association area to the cerebellar cortex.

1. Responses evoked in the cerebellar cortex by stimulation of the parietal association cortex (rostral portions of the middle suprasylvian gyrus) were recorded and analysed in cats, and were compared with those by stimulation of the motor cortex (anterior sigmoid gyrus). 2. The parietal stimulation elicited early mossy fibre and late climbing fibre responses in the cerebellar cortex. The mossy fibre responses appeared at a latency of 2.0--2.5 msec and predominantly in the lateral (hemispherical) part of the contralateral cerebellum (mainly crus I, crus II and paramedian lobules). Cutting of the inferior cerebellar peduncle produced little or no influence upon the mossy fibre responses, which suggests that the mossy fibre responses are mediated chiefly by the pontine nuclei. 3. The climbing fibre responses were recorded at a latency of 17--19 msec and markedly in the contralateral intermediate and medial parts of IV--VI lobules. The responses were easily sppressed by anaesthesia and depended on the conditions of experimental animals. The unstable appearance of the responses and their longer latencies than those of the climbing fibre responses due to stimulation of the motor cortex imply indirect pathways from the parietal association cortex to the inferior olive. 4. The predominant projection of the parietal-induced mossy fibre responses to the lateral part of the cerebellum was compared with the mossy fibre projection from the motor cortex and was discussed as an important component in the cerebrocerebellar loops.

Animals↗