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Biomedical subjects

Y Fukuda

Publications and source records attributed to Y Fukuda.

At least 1,081 records · Page 60Linked to original sources
PubMed1977

Effect of H+ on spontaneous neuronal activity in the surface layer of the rat medulla oblongata in vitro.

The effect of changing extracellular pH (pHe) on the spontaneous activity of neurons in brain slices taken from the ventral layer of the rat medulla oblongata was compared to the response of neurons in dorsal slices. In the ventral medulla, more than 50% of the neurons were excited by H+. These neurons were found just lateral to the pyramidal tract between the root of the hypoglossal nerve and the trapezoid body. In the dorsal medulla, low pHe caused an inhibition of activity in most neurons, although a few were excited. The fact that H+ elicted excitation predominantly in the ventral medullary substrate to respond to pHe changes. Depression of synaptic transmission within the neuronal network in the slice by reducing the [Ca2+]e and increasing the [Mg2+]e altered the nature of responses of neurons to H+: In the ventral medulla, the majority of neurons were inhibited by H+, whereas in the dorsal medulla more than 50% of neurons were excited. Therefore, "specificity" of the ventral medullary neurons seemed to be dependent upon intact synaptic connections. A possible role of acetylcholine-acetylcholinesterase system in the response of ventral medullary neurons to H+ is discussed.

Action Potentials↗
PubMed1977

A three-group classification of rat retinal ganglion cells: histological and physiological studies.

In a whole mount preparation of the hooded rat retina, stained with methylene blue, the ganglion cell density was counted over the retina. The density ranged from 6200-6500/sq.mm to 1000-1500/sq.mm. The area with a density higher than 6000/sq.mm was called the central area and was centered at about 1 mm (20 degrees) away from the center of the optic disc, in the upper temporal quadrant. Based upon soma diameter histograms made for several locations with different eccentricities, ganglion cells were classified into three groups; large (L), medium-sized (M) and small (S). Relative frequencies of the three groups, on average, were 5, 28 and 67%, respectively. The absolute densities of S- and M-cells increase sharply towards the central area whereas the L-cells show a relatively flat distribution over the retina. The three-group classification of the retinal ganglion cells was supported by measuring their axonal conduction velocities. Single unit recordings were made from the retina and the lateral geniculate nucleus. In each case, two sites were chosen in the optic pathway for electrical stimulation: the optic chiasm and the superior coliculus in the retinal study, and the distal end of the optic nerve and the optic chiasm in the geniculate study. From differences of response latency to the two stimulating sites, conduction velocities of the optic nerve fibers were estimated. The average velocities for the L-, M- and S-axons determined by retinal recordings were 16.8, 11.4 and 6.3 m/sec and those determined by geniculate recordings 18.6, 12.0 and 5.2 m/sec.

Animals↗
PubMed1977

[Two autopsy cases of adult central nervous system toxoplasmosis: light and electron microscopic studies (author's transl)].

Two autopsy cases of adult central nervous system toxoplasmosis were reported. Two cases treated with immunosuppressive agents and corticosteroids under a diagnosis of Hodgkin's disease were considered to be an acquired CNS toxoplasmosis associated with the underlying diseases. The first case, a 73 year old woman with Hodgkin's disease, showed toxoplasma lesions in the cerebrum. The second case, a 22 year old man with pulmonary tuberculosis, showed toxoplasma lesions in the cerebrum, basal ganglion, thalamus, cerebellum, pons, and medulla oblongatta. Each toxoplasma lesion showed small hemonecrotic softening. Toxoplasma cysts were seen around the hemonecrotic lesion. Encysted toxoplasma organisms were examined in detail with electron microscope.

Adult↗
PubMed1976

pH sensitivity of cells located at the ventrolateral surface of the cat medulla oblongata in vitro.

pH sensitivity of cells located at the ventral surface of the medulla oblongata was examined in a thin brain slice of the cat in vitro and the following results were obtained: (1) Transmembrane potential of the surface cells located in the area medial to the XIIth cranial nerve was reduced slightly by application of low pH solution; (2) In the rostral part of the area medial to the XIIth cranial nerve regular neuronal discharges could be observed extracellularly. The rate of firing of these cells was increased by lowering the external pH. These results were considered to support the idea the H+ receptor cells may exist in the surface layer of the ventral medulla.

Animals↗