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Biomedical subjects

I Nishikawa

Publications and source records attributed to I Nishikawa.

6 recordsLinked to original sources
PubMed1993

A model for feature linking via collective oscillations in the primary visual cortex.

A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex is proposed. In our model, the basic functional unit is an orientation column which is represented by a large homogeneous population of neurons modeled as integrate-and-fire type excitable elements. The orientation column exhibits spontaneous collective oscillations in activity in response to suitable visual stimuli. Such oscillations are caused by mutual synchronization among the neurons within the column. Numerical simulation for various stimulus patterns shows that as a result of activity correlations between different columns, the amplitude and the phase of the oscillation in each column depend strongly on the global feature of the stimulus pattern. These results satisfactorily account for experimental observations.

Animals↗
PubMed1993

Changes in cell proliferative activity in granulation tissue invading the root canal.

Root canal models were implanted in rats in order to investigate histologically the movement of granulation tissue invading apical canals and dead spaces and changes in cell proliferative activity as indicated by 3H-thymidine. The models were prepared to have 1, 2, and 3 mm apical canals, with and without dead spaces, to simulate preparations short of the apex and obturation to several levels. After 12 wks implantation of the models without dead spaces, granulation tissue invading 1 mm apical canals did not degenerate and cell proliferative activity remained high. However, tissue invading the 2 and 3 mm apical canals tended to be necrotic and cell proliferative activity was decreased. In the models with dead spaces, the tissue in the 1 and 2 mm apical canals developed and invaded the dead spaces, and still possessed proliferative activity 12 wks after implantation. In contrast, the tissue in the 3 mm apical canals did not invade the dead spaces, even after 12 wks, and no proliferative activity was observed.

Animals↗
PubMed1989

Systemic distribution of 14C-labeled formaldehyde applied in the root canal following pulpectomy.

The systemic distribution of 14C-labeled formaldehyde which had been placed in the root canals of the canines of cats following pulpectomies was studied using liquid scintillation counting and wholebody autoradiographic technique. Radioactive 14C which had been placed in the canals was found in the plasma 30 min after the root canal procedure. The recovery of systemic 14C radioactivity increased with time. In addition, it seemed that approximately 3% of the dose placed in the teeth was excreted in the urine within 36 h. Whole-body autoradiograms indicated extensive concentration of 14C radioactivity in tissues other than those analyzed with the liquid scintillation technique.

Animals↗
PubMed1976

Chemical composition of cynomolgus monkey milk.

Milk samples from eight cynomolgus monkeys whose lactation period ranged 44-119 days were investigated for their gross chemical composition such as total solids, crude protein, lipids, lactose and ash. Nitrogen distribution, compositions of fatty acids, amino acids and triglycerides as well as major minerals were also determined. These analytical data were compared with those reported for man, simian and cow, and cynomolgus monkey milk was found to have close similarities to human milk.

Amino Acids↗