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Biomedical subjects

K Tohyama

Publications and source records attributed to K Tohyama.

At least 109 records · Page 6Linked to original sources
PubMed1987

Nerve regeneration through cryo-treated xenogeneic nerve grafts.

Cryo-treated nerves whose Schwann cells had been killed by repeated freezing and thawing were xenogenically grafted into sciatic nerves from rats (Wistar, as donor) to mice (ddy strain, as recipient) to examine whether Schwann cell basal lamina tubes of cryo-treated xenogeneic grafts were effective conduits for regenerating axons. For comparison and evaluation of the effectiveness of this technique, experiments using grafts without the cryo-treatment were carried out. Cells in cryo-treated xenografts degraded into cell debris immediately after grafting and then were phagocytized by macrophages. After the cellular components had been removed from the graft, Schwann cell basal laminae remained intact in situ, serving as conduits for the regenerating axons. The process of nerve regeneration was almost the same as that observed in cryo-treated auto- and allografts, except that the regeneration was slightly delayed in the xenogeneic graft. In contrast, an extensive cell infiltration occurred in the non-treated grafts. It appeared that the donors Schwann cells in the graft deteriorated due to immunological reactions and were finally eliminated by macrophages, leaving their basal laminae undamaged in situ. The initiation of nerve regeneration including perineurial sheath formation in non-treated grafts was, therefore, significantly delayed, but once begun, it proceeded in the same manner as in the cryo-treated grafts. These findings strongly indicate that Schwann cell basal laminae can serve as effective pathways for regenerating axons even in the xenograft. Moreover, cryo-treated xenogeneic grafts are more desirable than non-treated ones, since dead Schwann cells in the former can be removed in the early period (4-14 days) from the graft without causing any immunological reaction, thus resulting in the facilitation of nerve regeneration.

Animals↗
PubMed1987

Carbonic anhydrase activity in axon terminals of sensory corpuscles.

The distribution of carbonic anhydrase (CA) activity was studied by electron microscopic histochemistry in rat Pacinian corpuscles, Meissner corpuscles and Merkel cell-neurite complexes using the cobalt bicarbonate method. The distribution of CA activity in these axon terminals was compared to the activity in sciatic nerve axons. An intense enzymatic CA activity was demonstrated in axon terminals of both Pacinian and Meissner corpuscles, while a weak activity was found within the axoplasm of terminals abutting Merkel cells. Some large- and medium-sized axons in sciatic nerves exhibited an intense activity. These findings indicate that large- or medium-diameter sensory axons innervating corpuscular endings have an intense CA activity extending from their somata to their sensory terminals. Axons to Merkel-neurite complexes differ in CA activity from those innervating Meissner and Pacinian corpuscular endings.

Animals↗
PubMed1987

[Real-time observation of blood flow velocity profiles in the right ventricular inflow tract by a newly-developed instantaneous B-mode and multi-channel Doppler echocardiography].

We observed the blood flow profile in the right ventricular inflow tract through the tricuspid valve using the newly-developed equipment which images by instantaneous B-mode and multi-channel Doppler echocardiography. The Doppler system had 64 sampling gates in an ultrasonic beam within a depth of 13 cm. A cursor line was set at an angle of 45 degrees to the tricuspid annulus on two-dimensional echocardiography in a parasternal long-axis view of the right atrium and right ventricle. The blood flow velocity was displayed on the vertical line on the left-side of the CRT image. All Doppler-shifted frequencies of the 64 channels were analyzed using a fast Fourier transform formula by a built-in processor. The Doppler-shifted frequency was displayed at 30 frames per sec. The study subjects consisted of 20 children without cardiac anomalies. Their ages ranged from 2 to 18 years. A typical blood velocity profile at the tricuspid valve ring during the rapid filling phase had an "M" shape, i.e., the velocity was greater at both margins than in the central portion, followed by a flat profile. A small retrograde flow was observed behind the posterior tricuspid leaflet at this time. The flow velocity decreased in mid-diastole, then increased again during the atrial contraction period, with either flat or parabolic profile. During inspiration, the velocity was greater and the shape of the flow profile throughout diastole tended to be flat. In systole, a slow antegrade flow was observed in the tricuspid valve ring area, and its flow profile was parabolic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Nerve regeneration through allogenic nerve grafts in mice.

The purpose of this study was to examine whether the basal laminae of Schwann cells in allografts could survive immunological rejection and serve as a conduit for regenerating nerves, as in the case of autogenic nerve grafts. Allografts of nerves were carried out using sciatic nerves of mice after the grafts had been repetitively frozen to kill their Schwann cells. Two mouse strains, C57BL/6N and C3H/HeN, were used, as they are known to differ in major histocompatibility complex. The mid-portion of the grafted nerve segments was examined by electron microscopy. In addition, the toe pad skin and lumbrical muscles were examined for determining whether regenerating nerves reinnervate sensory end organs and motor endplates. The process of nerve regeneration in the allograft was the same as that seen in the autograft. Cells in the graft disintegrated into cell debris and were phagocytized by macrophages, whereas the basal laminae of Schwann cells were not removed by macrophages, remaining in the form of tubes or scaffolds. Regenerating nerve fibers grew out through such basal lamina scaffolds, keeping in contact with the inner surface. Digital sensory corpuscles and motor endplates of the operated side were well reinnervated. The results indicate that the basal laminae of Schwann cells of the allograft may survive and serve as a conduit for regenerating axons in the same way as in the case of an autograft.

Animals↗
PubMed1986

[Mitral valve abnormalities in the hypoplastic right heart syndrome: echocardiographic observations].

Two-dimensional echocardiographic examinations were performed for 86 patients with the hypoplastic right heart syndrome (55 cases of tricuspid atresia, 9 of pure pulmonary stenosis and 22 of pure pulmonary atresia). Prolapse of the anterior mitral leaflet was detected in 14 patients (16.3%). Four of these 14 patients had mitral regurgitation. Among the patients with mitral valve prolapse, ruptured chordae tendineae of the mitral valve were detected in two, and elongation of the chordae in one. There were no significant relationships between the incidence of mitral valve prolapse and sex, age, type of tricuspid atresia, previous palliative surgery, or PaO2. However, one patient with pure pulmonary stenosis, who had had mitral valve prolapse without mitral regurgitation, developed mitral regurgitation several months after undergoing a Blalock-Taussig shunt operation. The mechanism responsible for mitral valve prolapse in the hypoplastic right heart syndrome is not clear. Multiple factors, such as long-standing left ventricular volume overload, hypoxic myocardial damage, and anatomical chordal abnormalities may cause mitral valve prolapse. The presence of a mitral valve abnormality has an important bearing on the natural history as well as the surgical procedure of choice. The need for careful echocardiographic examinations to detect mitral valve abnormalities in the hypoplastic right heart syndrome is thus underscored.

Adolescent↗
PubMed1986

[Membranous tricuspid atresia with right ventricular dysplasia and absent pulmonary valve: echocardiographic findings in three cases].

Membranous tricuspid atresia with right ventricular dysplasia and absent pulmonary valve is a very rare complex, and a unique type of tricuspid atresia. Three cases with this condition were presented with the echocardiographic evaluation. Two-dimensional echocardiography was performed in all patients, pulsed Doppler echocardiography in two, and contrast echocardiography in two patients. The echocardiographic findings characteristic of this complex were as follows: In the four chamber view, the interatrial and interventricular septa were aligned, and tricuspid valve atresia was of the membranous type. In the four-chamber view, the right ventricular wall was thin, irregular in shape, and it protruded aneurysmally into the left ventricular outflow tract. With systemic venous contrast echocardiography, the right ventricular cavity was opacified with contrast, four to five cardiac cycles after the appearance of contrast in the left ventricle. With pulsed Doppler echocardiography at the main pulmonary artery, antegrade flow was observed in ventricular systole, and retrograde flow in diastole. We conclude that these echocardiographic findings are useful in recognizing the morphology and hemodynamics of this complex.

Child↗
PubMed1985

The localization of lectin-binding sites on Schwann cell basal lamina.

Basal laminae were separated from Schwann cells of mouse sciatic nerves by sonification, and the distributions of lectin-binding sites were demonstrated by electron microscopy using ferritin-conjugated lectins. Only three out of the 11 lectins examined were bound to the basal laminae of Schwann cells: they were Ricinus communis agglutinin-I (RCA-I), Canavalia ensiformis agglutinin (ConA) and Triticum vulgaris agglutinin (wheat germ agglutinin, WGA). It was notable that WGA was bound more densely to the cellular side than to the interstitial side, whereas in the case of RCA-I and ConA there were no differences in the binding density on the two sides of the basal lamina. These results indicate that there are sugar residues such as beta-D-galactose, alpha-D-mannose, alpha-D-glucose and beta(1-4) linked N-acetyl-D-glucosamine in the Schwann cell basal laminae. The first three sugar residues are almost equally densely distributed on the cellular and interstitial sides of the basal laminae, whereas beta(1-4) linked N-acetyl-D-glucosamine is more densely distributed on the cellular than on the interstitial side. This result suggests that the basal lamina has a polarity in chemical composition between the cellular and interstitial sides. These findings are discussed in the context of the preferential attachment of regenerating axons to the cellular side of the Schwann cell basal laminae.

Animals↗
PubMed1985

Macrophages in Pacinian corpuscles.

The presence of macrophages in the outer bulb region of mouse, monkey and human Pacinian corpuscles was demonstrated by light and electron microscopy. In the normal, nontreated, Pacinian corpuscles, a few particular cells were located in the spaces between lamellae of the outer bulb. These cells contained numerous vesicles and vacuoles, and various cytoplasmic processes. When horseradish peroxidase (HRP) was injected locally or systemically, many HRP-positive cells, which were considered to be similar to the particular cells described above, were found in the outer bulb region of the corpuscles. Electron microscopy revealed that these cells contained HRP in vesicles and vacuoles, suggesting that they were macrophages vigorously taking up exogenous HRP. Macrophages in the Pacinian corpuscles are considered to work as scavengers to keep the inner environment of the corpuscles clear and constant with regard to its macromolecular content.

Animals↗
PubMed1985

[Evaluations of regional cerebral blood flow (rCBF) by 133Xenon i.v. method in patients with occlusions of bilateral internal carotid arteries].

The studies of changes in regional blood flow (rCBF) have been reported on different clinical courses in the five cases (mean 57.4 y.o.) showing bilateral occlusion or stenosis of internal carotid arteries. Values of rCBF using Fg (fast component in gray matter) were closely correlated with their clinical courses. The three patients (2 males and 1 female) showed bilateral focal decreased patterns of rCBF and their uneventful clinical courses except for mild attacks of transient cerebral ischemia. However, the rest two male patients showed bilateral decreased pattern of rCBF and moderate hemiparesis including attacks of loss of consciousness. The one died suddenly because of the thalamic hemorrhage and the other died also suddenly from the unknown etiology. Such differences between the classification of clinical course and hemodynamics evaluated by rCBF was discriminated more clearly by Fg (fast component in gray matter) than by F mean (mean rCBF). The authors concluded that the evaluation by Fg may be valuable to estimate prognosis of patients with bilateral occlusion of internal carotid artery. There are two patterns of decreased rCBF in our study. The patients with bilateral diffuse decreased patterns of rCBF should be followed up more carefully because of the sudden death from cerebral hemorrhage.

Aged↗
PubMed1984

The localization of laminin and fibronectin on the Schwann cell basal lamina.

The localization of laminin and fibronectin was examined on the basal laminae of Schwann cells. Basal laminae from sciatic nerves were isolated by sonication, and the localization of laminin and fibronectin on such isolated basal laminae was studied by immunoferritin histochemistry. Laminin was localized mainly on the cellular side (i.e. the side originally facing the Schwann cell plasma membrane) of the basal laminae. On the other hand, fibronectin was found to be present as aggregates only on the interstitial side (i.e., the side originally facing the endoneurial connective tissue) of the basal laminae. Thus, the locations of laminin and fibronectin were distinctly different. It is presumed that laminin might be involved in the attachment of axons and Schwann cells to the basal laminae, while fibronectin mediates the adhesion of the basal laminae to connective tissue elements, including the collagen fibrils. These findings are discussed from a standpoint of nerve regeneration through the basal laminae scaffolds of Schwann cells.

Animals↗
PubMed1983

Schwann cell basal lamina and nerve regeneration.

Nerve segments approximately 7 mm long were excised from the predegenerated sciatic nerves of mice, and treated 5 times by repetitive freezing and thawing to kill the Schwann cells. Such treated nerve segments were grafted into the original places so as to be in contact with the proximal stumps. The animals were sacrificed 1, 2, 3, 5, 7 and 10 days after the grafting. The grafts were examined by electron microscopy in the middle part of the graft, i.e. 3-4 mm distal to the proximal end and/or near the proximal and distal ends of the graft. In other instances, the predegenerated nerve segments were minced with a razor blade after repetitive freezing and thawing. Such minced nerves were placed in contact with the proximal stumps of the same nerves. The animals were sacrificed 10 days after the grafting. Within 1-2 days after grafting, the dead Schwann cells had disintegrated into fragments. They were then gradually phagocytosed by macrophages. The basal laminae of Schwann cells, which were not attacked by macrophages, remained as empty tubes (basal lamina scaffolds). In the grafts we examined, no Schwann cells survived the freezing and thawing process. The regenerating axons always grew out through such basal lamina scaffolds, being in contact with the inner surface of the basal lamina (i.e. the side originally facing the Schwann cell plasma membrane). No axons were found outside of the scaffolds. One to two days after grafting, the regenerating axons were not associated with Schwann cells, but after 5-7 days they were accompanied by Schwann cells which were presumed to be migrating along axons from the proximal stumps. Ten days after grafting, proliferating Schwann cells observed in the middle part of the grafts had begun to sort out axons. In the grafts of minced nerves, the fragmented basal laminae of the Schwann cells re-arranged themselves into thicker strands or small aggregations of basal laminae. The regenerating axons, without exception, attached to one side of such modified basal laminae. Collagen fibrils were in contact with the other side, indicating that these modified basal laminae had the same polarity in terms of cell attachment as seen in the ordinary basal laminae of the scaffolds.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Distribution of anionic sites on the basal lamina of Schwann cells.

Basal laminae (BL) were separated from Schwann cells of rat sciatic nerves by means of weak sonication, and the anionic sites of the BL were demonstrated by using cationized ferritin (CF) or ruthenium red (RR). CF particles were deposited in clusters at intervals of 100-150 nm on the interstitial side of the BL facing the connective tissue, while the cellular side facing the Schwann cell plasmalemma showed only an occasional deposition of CF particles. RR-positive sites were found only on the interstitial side with a pattern of distribution comparable to that of CF-binding sites. These results indicate that the patterns of anionic site distribution are different between the inner and outer surfaces of the Schwann cell BL.

Animals↗