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Biomedical subjects

T Yamamura

Publications and source records attributed to T Yamamura.

At least 451 records · Page 25Linked to original sources
PubMed1978

Controlled locomotion in the mesencephalic cat: distribution of facilitatory and inhibitory regions within pontine tegmentum.

1. The contribution of postural tonus to controlled locomotion elicited by the stimulation of mesencephalic locomotor region (MLR) was studied in the acute precolicular-postmammillary decerebrate (mesencephalic) cat. 2. A microelectrode was placed in the unilateral MLR and another was placed systematically at 1-mm increments throughout the pons (H--4 to H--1O) at level ranging from P2 to P11 dorsoventrally and mediolaterally from 0 to L or R6. Depending on the general condition of the animal, stimuli through this second electrode were delivered preceding, succeeding, or simultaneous with the MLR stimulation. 3. Stimulation of the ventral part of the caudal tegmental field (P3 to P9, H--6 to H--8) increased extensor tonus of the hindlimbs, as assessed by recording muscle activity. Concomitant stimulation of this region converted MLR-elicited hindlimb stepping to coordinated four-legged locomotion and also elicited locomotion even when stimulation of the MLR alone failed to elicit locomotion. Stimulation of this ventral tegmental region alone at a larger stimulus intensity elicited spastic locomotor movements associated with a substantial increase in extensor tonus. 4. Stimulation of the lateral tegmented field surrounding the pontine locomotor region (PLR) also facilitated MLR effects, but had a relatively weaker facilitatory effect on postural tonus then stimulation of the ventrocaudal tegmental field. PLR stimulation alone was also ineffective when postural tonus was not well maintained. 5 Stimulation of the dorsal part of caudal tegmental field (P3 to P9, H--4 to H--6) in its midline dramatically decreased extensor tonus of the hindlimbs. MLR-elicited controlled locomotion was completely suppressed during concomitant stimulation of this inhibitory region. 6. These results indicated clearly that the degree of existing postural tonus greatly affects MLR-elicited locomotor movements and that an increase in postural tonus and an activation of the spinal stepping generator are not separate phenomenia.

Animals↗
PubMed1977

Functional properties of peripheral sensory units in hairy skin of a cat's forelimb.

The properties of peripheral cutaneous units in the hairy skin of cat's forelimb were studied by single-fiber recordings with tungsten microelectrodes. The response properties and receptive field (RFs) of total 193 units in superficial branch of radial nerve (SRN) were studied. The SRN sample included the following five major types of mechanoreceptive units; two types of low-threshold units (type I and II, slowly adapting), two types of hair units (G and D, rapidly adapting) and field units (F, responding principally to slow skin movement). Afferent conduction velocities of these units ranged from 9.0 to 56.0 m/sec. D hair fibers conducted much slower than other types of afferents and their conduction velocities were between 9.0 and 23.3 m/sec. Most of the smaller RFs of G, D and F units were found in the paw and digits. The disto-proximal increase of the mean size of RFs was marked in D hair units. The distributions of the RFs of simultaneously recorded paired units, which were supposed to be adjacent fibers, were examined. Among 23 paired units, more than half of them were homonymous combinations of unit types and there were no marked prevalence of particular types in heteronymous combinations. The RFs of paired units were close to each other, but showed little overlaps and some were separated by up to several cm over the skin surface. Some functional properties of cutaneous afferents from the forelimb were discussed.

Animals↗
PubMed1975

An experimental study of intraoral carcinogenesis in rats.

A new method has been devised for preparing artificial cecal pouches lined with mucous epithelium in the lower lips of Wistar and Sprague-Dawley rats in order to make carcinogens act continuously for a long time in the oral mucosa. When a 0.5 per cent mineral oil solution of DMBA, a crystal of MC, and a crystal of NG were administered, squamous-cell carcinoma, carcinoma in situ, papilloma, adenoma sebaceum. neurofibroma, fibroma, hemangiosarcoma, hemangiosarcoma, hemangioma, and lymphangioma were successfully produced in the oral mucosa of rats. In addition, interesting findings were obtained concerning tissue changes in the process of carcinogensis in the mucous epithelium.

Animals↗