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Biomedical subjects

M Kumamoto

Publications and source records attributed to M Kumamoto.

At least 37 records · Page 2Linked to original sources
PubMed1992

Endothelial function in thrombosis and thrombolysis.

The localization of tissue factor (TF) in atherosclerotic plaques of human aortas was immunohistochemically examined using rabbit anti-IgG against recombinant TF, which was expressed in E. coli. TF, the initiator of the extrinsic coagulation pathway, was ubiquitously present in atherosclerotic intima, and was expressed mainly by macrophages, but not by endothelial cells. It has been suggested that some macrophages in atherosclerotic intima co-express both molecules of TF and platelet-derived growth factor-B chain. We have developed a morphometrically quantitative in vitro assay for angiogenesis, using endothelial cultures on collagen gel incorporating plasminogen. With this method, we have obtained findings suggesting that plasminogen and plasminogen activators (PAs), especially urokinase-type PA (uPA) derived from endothelial cells, enhance angiogenic activity, probably by increasing endothelial migration. uPA was immunohistochemically observed to be primarily cell-associated on the focal contract areas, probably via its receptors on endothelial cells. These findings may support the hypothesis that the activation and regulation of the pericellular fibrinolysis system is closely related to angiogenesis.

Animals↗
PubMed1990

Sequential appearance of host-derived T cell subsets during differentiation in nude mice grafted with rat fetal thymus.

To elucidate the abnormality of T cell differentiation in nude mice grafted with rat fetal thymus that develop multiple-organ-localized autoimmune diseases, we examined sequential appearance of T cell subsets and expression of TCR genes in BALB/c nude mice after grafting with fetal F344 rat thymus. We observed progressive expression of TCR gamma/delta-alpha/beta genes in the lymph node (LN) cells from 8 to 12 wk after grafting. An appreciable number of CD4+ T cells but few CD8+ T cells were detected in the LN at 8 wk after grafting. CD8+ T cells increased slowly in number by 12 wk after grafting but remained at a low level in comparison with those in nude mice 12 wk after grafting with BALB/c thymus. In correlation with an increase in the number of T cells expressing TCR alpha/beta genes, alloreactivity as assessed by MLR was increased to a normal level. However, CTL activity against alloantigens remained at a low level in the LN cells at 12 wk. At this stage, organ-specific autoimmune diseases and a high level of anti-DNA autoantibodies were detected. In these mice host-reactive T cells such as V beta 3- or V beta 11-bearing T cells were virtually eliminated in the peripheral mature T cell pool, whereas T cells maturing in the fetal rat thymus significantly proliferated in response to donor-rat stimulator cells. These results suggest that the development of the autoimmune diseases may be ascribed to an impaired maturation of CD8+ T cells but not to failure in clonal elimination of host-reactive T cells in nude mice grafted with rat thymus.

Animals↗
PubMed1990

Sustained arterial injury and progression of atherosclerosis.

In this paper the following findings were described: 1) Murine arteriosclerosis induced by immune challenge was ultrastructurally characterized by intimal monocyte-macrophage recruitment and minor endothelial alterations; 2) Atherosclerotic lesions of human coronary arteries exhibited frequently segmental or patchy neovascularization, probably representing a response to intimal injury as an example of repair process. Newly formed blood vessels in the intima were derived from both adventitial and luminal endothelial growth; 3) Angiogenesis in vitro was related to the activation of fibrinolytic system especially via the autocrine production of u-PA from endothelial cells, and this process was modulated by cytokines and TGF beta. These findings add more evidence for the hypothesis that the chronic inflammation-repair process plays an essential role in the initiation and progression of atherosclerosis.

Animals↗
PubMed1990

Electric discharge patterns of ankle muscles during the normal gait cycle.

EMG patterns in ankle muscles were examined during normal gait cycles in 147 healthy asymptomatic adults. In all subjects, the tibialis anterior (Ta) showed marked activities around the toe-off and before the heel-strike, and the gastrocnemius lateral head (Gl) showed marked activity during the midstance phase but no activity in the early part of the swing phase. The Ta activity contributed to ground clearance, prevention of foot-drop, and shock absorption at the heel-strike. The Gl activity contributed to push-off from the ground and prevention of foot-drop. The Ta activity consisted of double bursts with (15% of subjects) or without (44%) electric silence in the midswing phase, continuous discharge (33%), and triple discharge patterns (8%). The Gl activity consisted of a single-peak (95%) pattern or double-peak (5%) patterns.

Adult↗
PubMed1989

Computer system and software of POSITOLOGICA II: a whole body positron emission tomograph.

Since a whole body PET-scanner POSITOLOGICA II was installed at the National Institute of Radiological Sciences (NIRS) in 1982, improvements of the computer system and developments of new software have been continuously made to correspond to clinical requirements. As the result, POSITOLOGICA II possesses one of the most powerful systems and sophisticated software in Japan. This report describes the present status of the computer system and software of POSITOLOGICA II. It also discusses problems which still exist and proposes a future computer system for the PET study.

Brain↗
PubMed1984

[Two cases of malignant cardiac tumors attached on the anterior mitral valve].

Two cases were reported in which malignant cardiac tumors attached to the mitral valve were diagnosed during their lifetimes using two-dimensional echocardiography. Case 1 was a 29-year-old man with speech disturbance and left hemiparesis. Histological examination of the specimen excised from the cardiac tumor during the operation revealed mesenchymal chondrosarcoma, which is extremely rare etiologically and has never been reported so far. Case 2 was a 62-year-old woman complaining of paroxysmal nocturnal dyspnea and chest pain. The diagnosis of malignant histiocytosis was made from the pathological examination of biopsy specimen taken from the rib metastasis. Using two-dimensional echocardiography, characteristic findings for the cardiac tumor were obtained. The tumor echo in Case 1 showed, unlike to that reported for myxoma, two different echogenic layers; the outer dense and the inner light in the echo density. On surgery, tumor echo was revealed to reflect the cystic lesion. In Case 2, two-dimensional echocardiography on admission revealed two separate tumor echoes which attached to the mitral valve and left atrial wall region, respectively. Within two months, they grew rapidly and finally fused into one mass resulting in so-called ball valve syndrome. Phonocardiographically, the tumor plop in Case 1 was high-pitched in quality, and was extinguished completely after the tumor was resected. The tumor plop in Case 2 was not audible on admission, but became evident after fusion of the tumor echoes and was associated with a presystolic murmur.

Adult↗
PubMed1978

Effects of conditioning polarization on the membrane ionic currents in rat myometrium.

Membrane ionic currents were measured in pregnant rat uterine smooth muscle under voltage clamp conditions by utilizing the double sucrose gap method, and the effects of conditioning pre-pulses on these currents were investigated. With depolarizing pulses, the early inward current was followed by a late outward current. Cobalt (1 mM) abolished the inward current and did not affect the late outward current per se, but produced changes in the current pattern, suggesting that the inward current overlaps with the initial part of the late outward current. After correction for this overlap, the inward current reached is maximum at about +10 mV and its reversal potential was estimated to be +62 mV. Tetraethylammonium (TEA) suppressed the outward currents and increased the apparent inward current. The increase in the inward current by TEA thus could be due to a suppression of the outward current. The reversal potential for the outward current was estimated to be -87 mV. Conditioning depolarization and hyperpolarization both produced a decrease in the inward current. Complete depolarization block occurred at membrane potential of -20 mV. Conditioning hyperpolarization experiments in the presence of cobalt and/or TEA revealed that the decrease in the inward current caused by conditioning hyperpolarization was a result of an increase in the outward current overlaping with the inward current. It appears that a part of the potassium channel population is inactivated at the resting membrane potential and that this inactivation is removed by hyperpolarization.

Action Potentials↗
PubMed1976

An electromyographic study on training to pronounce English consonants unfamilar to Japanese.

This paper is concerned with the electromyographic analyses of the pronunciation of English consonants as pronounced by a native speaker, a well-trained Japanese, and an untrained Japanese. Six muscles related to movement of the lips and the mandible were tested. The three-paired English words (right--light, she--see, and thank--sank) were selected, as they include consonants that are very difficult for Japanese to pronounce or distinguish correctly when heard. Electromyographic results obtained for the native speaker and the well-trained Japanese indicated light pouting of the lips during the preparatory period for pronouncing [r], raising of the upper lip from the preparatory period in the pronouncing of [sh] and [th], and a downward spreading of the lower lip from the preparatory period in the pronouncing of [l] and [s]. The untrained Japanese subject was given individual and intensive training for several hours with a technique based on electromyographic observation results. Following this, the subject showed improvement in pronouncing the consonants, with the exception of [sh] which the subject had learned to pronounce at a language school. The electromyograms of the subject approached those of the native speaker and the well-trained Japanese.

Adult↗