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S Masuko

Publications and source records attributed to S Masuko.

68 records · Page 4Linked to original sources
PubMed1986

Freeze-fracture study of the large myelinated club ending synapse on the goldfish Mauthner cell: special reference to the quantitative analysis of gap junctions.

The large myelinated club endings (LMCEs) of primary eighth nerve afferents form mixed synapses on the lateral dendrite of the giant Mauthner cell. The double replica freeze-fracture technique was employed to examine the intramembrane fine structure of these LMCE synapses. Morphological correlates of both chemical and electrical transmission were found at the LMCE synapses. Electrical synaptic junctions, or gap junctions, were located over much (10-20%) of the synaptic contact. These were seen in both pre-and postsynaptic membrane as tightly packed P face particle aggregates and corresponding aggregates of E face pits. Specializations characteristic of chemical synaptic junctions were most prominent at the periphery of the synaptic contact. These specializations consisted of postsynaptic E face particle aggregates which were subjacent to presynaptic active zones. The active zones were distinguishable as regions with an increased density of large particles and vesicle attachment sites represented by P face depressions and E face protuberances. Quantitative analysis of gap junction particle (connexon) number at five LMCEs revealed 24,000-106,000 connexons per LMCE. Comparison with data from electrophysiological studies of single LMCEs indicates that only a small fraction of the connexon channels are open at any given time during electrotonic transmission at an LMCE synapse.

Animals↗
PubMed1986

Correlation of mitochondrial swelling after capsaicin treatment and substance P and somatostatin immunoreactivity in small neurons of dorsal root ganglion in the rat.

Capsaicin injections into adult rats produced swelling of mitochondria in a population of small neurons of the dorsal root ganglia. Large neurons did not show the mitochondrial change. The mitochondrial swelling was confirmed to be a specific change produced by capsaicin treatment by the examination of different fixation conditions in both control and capsaicin-treated materials. Whether or not these mitochondrial changes occur in a subpopulation of small neurons which contain particular neurotransmitters was examined. The swelling of mitochondria was found in most substance P- or somatostatin-immunoreactive neurons and also in some non-immunoreactive small neurons. The present results indicate that the swelling of mitochondria is a specific change which may correlate with long-lasting desensitization of nociceptive neurons in the dorsal root ganglion after capsaicin treatment.

Animals↗
PubMed1986

Noradrenergic neurons from the locus ceruleus in dissociated cell culture: culture methods, morphology, and electrophysiology.

We have developed a dissociated primary cell culture of noradrenergic neurons from the locus ceruleus of postnatal (1- to 5-d-old) mice or rats. Slices of the brain stem were made on a Vibratome. Then the region of locus ceruleus, which was identified by observing the slices under a dissecting microscope, was dissected out from the slices. The removed fragments of brain slices were dissociated and cultured up to 3 weeks on a non-neuronal feeder layer, which consisted predominantly of astroglial cells, or on a fibronectin-treated collagen substratum. After 2 weeks of culture, about 70% of total neuronlike cells revealed positive catecholamine histofluorescence, indicating that they were probably noradrenergic neurons. About 98% of large- and medium-sized cultured neurons (soma diameter greater than or equal to 20 microns) was histofluorescence positive. The fluorescence-positive cells had long processes rich in varicosities, and the shape of their soma was either multipolar or fusiform. Electron microscopy using permanganate fixation revealed that the varicosities along their processes had small granular vesicles, which may contain norepinephrine. Physiological properties of these noradrenergic neurons were investigated with intracellular microelectrodes or with the whole-cell version of the patch clamp. We observed that many cells were producing spontaneous firing. Many of these spontaneously firing cells had no obvious contact with neighboring cells. The neurons were depolarized when glutamate was applied by pressure ejection. They also responded to GABA and glycine with either hyperpolarization or depolarization, and these responses were antagonized by picrotoxin and strychnine. Application of substance P generally produced depolarization with an increase in input resistance. The neurons responded with hyperpolarization to somatostatin, beta-endorphin, and enkephalin. This culture system will become a useful tool for elucidating the cellular and molecular properties of the central noradrenergic neurons.

Action Potentials↗
PubMed1985

[Utilization of a computer using programless language for radiation protection management].

Utilization of the computer for radiation control is planned and performed in many radioisotope laboratories. But each laboratory has their own situation which makes the planning difficult with respect to the hardware and particularly to the software. What is the most important is that the practice of radiation management is different for each laboratory both in point of view and in the form of recording. Therefore, the computer program for the radiation management, especially for the management of radioisotopes is required to meet many amendments. In this standpoint, we have developed a "programless language" or "programless software" and have used in our work for several years. As the result of our experience, we have found that the programless language is quite satisfactory for the management of radioisotopes and that it has an advantage in some aspects over conventional programs. It is thought that this "programless language" is effective not only for our own works, but also applicable to other radioisotope laboratories.

Computers↗
PubMed1983

Neuronal cell-surface specific antigen(s) is expressed during the terminal mitosis of cells destined to become neuroblasts.

By immunizing mice with cells from embryonic chick motoneuron cultures, an antiserum was produced which recognizes an antigen(s) restricted to cell surfaces of most, or all, neurons. With the use of this antiserum, the appearance of neuron-specific antigenicity in cells of the embryonic spinal cord was examined by indirect immunofluorescence microscopy. The antigen or set of antigens reacting with this antiserum was first detectable in the neural tube of chick embryos at stage 15-16 (V. Hamburger and H.L. Hamilton, 1951, J. Morphol. 88, 49-92). In addition to the neuroblasts located in the mantle layer, some mitotic cells as well as some spindle-shaped cells in the germinal layer were antigen positive. Immunofluorescence microscopy combined with autoradiography revealed that none of the antigen-positive cells could be labeled with [3H]thymidine; thus they do not synthesize DNA, and none of the cells in the DNA synthetic phase expressed the antigen(s). As the neuroblasts do not synthesize DNA after they have differentiated from the germinal cells, we believe that the antigen-positive cells are differentiated elements and that the differentiation of membranes specific for neurons begins already before or during the terminal mitosis of cells which will be defined as neuroblasts.

Animals↗
PubMed1983

Preparation of microspheres of poly(glycidyl methacrylate) and its derivatives as carriers for immobilized proteins.

Microspheres of poly(glycidyl methacrylate) and its derivatives have been prepared. The diameter can be varied in the range from 0.5 to 5 micron. Proteins were immobilized on the microspheres by various processes. The maximum amount of covalently immobilized gamma-globulin on the microspheres was found to be about 6 mg/m2. It was shown that dyed microspheres with a diameter of 2-4 micron are applicable to immunological agglutination tests on a microplate as carrier particles substituting for red blood cells.

Acrylates↗
PubMed1979

Isolation and culture of motoneurons from embryonic chicken spinal cords.

A method is described for isolating cholinergic alpha motoneurons from the spinal cord of chicken embryos at stage 17-18 (Hamburger and Hamilton numbering), at the time when it has been shown that motoneurons withdraw from the mitotic cycle but neurons of other types and glia are still mitotic. Fragments of the ventral half of the spinal cord are incubated for 24 hr in the presence of 10 microM 1-beta-D-arabinofuranosylcytosine in order to eliminate dividing cells and are subsequently dissociated into a suspension of single cells. The following evidence has been obtained and suggests that these cells are neuronal and appear to be alpha motoneurons: (i) they are resistant to the lethal effect of arabinofuranosylcytosine, and thus are postmitotic at stage 17-18; (ii) when grown in vitro, they exhibit morphological characteristics similar to those of ventral spinal neurons, which include the ability to be stained with silver, Nissl, methylene blue vital stain at pH 6.5-7.0, and choline acetyltransferase histochemistry; (iii) they have high choline acetyltransferase activity; (iv) they are capable of forming functional synapses with muscle.

Animals↗