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M Azuma

Publications and source records attributed to M Azuma.

At least 415 records · Page 23Linked to original sources
PubMed1979

Stimulus and behavioral factors contributing to the activation of monkey prefrontal neurons during gazing.

Many neurons in the inferior dorsolateral area of the monkey prefrontal cortex showed sustained increases in discharge rates during continuous gazing at a tiny light spot that had a reward significance. These increases might depend upon stimulus factors (light target), behavioral factors (gazing) or both. In this report, we tried to separate these factors and to test the extent to which each factor might contribute to the neuronal reaction. Monkeys were trained to exhibit two kinds of behavior: 1) maintained gazing at a light target and 2) "gazing" behavior without a clear target. We then examined neuronal behavior in these two kinds of gazing behavior. During "gazing at target," many prefrontal neurons showed tonic activation; thus the previous findings were confirmed. These neurons behaved in various ways in "gazing without target": 1) some of the neurons were activated to the same extent as in "gazing at target"; 2) many others also showed activation but with lower discharge rates; and 3) the rest of the neurons completely ceased activation. Such variation in discharge patterns may be interpreted as meaning that there is a continous and graded difference among individual neurons in the dependence of their gaze-related activation upon a visible target. Then it seems that the stimulus factors are involved in a graded manner in generation of the activation, and further that other factors, probably behavioral ones, also contribute in part to it.

Action Potentials↗
PubMed1978

Regulation of interferon production by dibutyryl cyclic GMP in serum-free human diploid cell cultures.

The mechanism for regulating interferon production was investigated in relation to accentuation of production in serum-free human diploid cells (strain WI-38) treated with N2,O2-dibutyryl guanosine 3',5'-cyclic monophosphate (db-cyclic GMP). Interferon production in serum-free WI-38 cell cultures in response to Newcastle disease virus (NDV) was greatly reduced. In these cells, there was decreased incorporation of 5-3H-uridine into the acid-insoluble fraction, but unimpaired incorporation of U-14C-L-leucine, as compared with serum-containing cultures. When serum-free cell cultures were treated with 0.2 mM-db-cyclic GMP, incorporation of both 5-3H-uridine and U-14C-L-leucine was increased and there was an 8-fold enhancement in the yield of interferon in response to NDV. Induction of db-cyclic GMP-treated cells by NDV in the presence of cycloheximide and actinomycin D suggests that db-cyclic GMP enhances transcription of the interferon gene, and thereby augments interferon production.

Blood↗
PubMed1978

Interferon synthesis in human diploid cells pretreated with insulin.

Interferon production by Newcastle disease virus in human diploid (WI-38) cells was greatly reduced in the absence of serum. Pretreatment of the serum-free cells with insulin in excess of 1.2 IU/ml for 2 h before induction considerably increased the amount of interferon produced. No enhancement of interferon production was seen when the cells were exposed to insulin 2 h after induction or later. The insulin's effect persisted for at least 6 h after its removal, but not for 24 h. A possible mechanism of insulin action is discussed.

Animals↗
PubMed1977

Reversible changes in circular dichroism spectra of cattle rhodopsin and isorhodopsin.

When the disk membrane of rod outer segment is treated with detergents, the alpha-band CD of rhodopsin decreases and the gamma-band CD increases. This tendency of CD change is most prominent in the purified rhodopsin in cholic acid obtained by the ammonium sulfate fractionation of disk membranes, and the gamma-band CD is three times larger than the alpha-band CD. The beta-band CD of rhodopsin is only slightly influenced by detergents. The gamma-band of isorhodopsin shows two CD bands, one negative and one positive. Both in rhodopsin and isorhodopsin the gamma-band CD is lost by light irradiation. It is supposed that both chromophore retinal and aromatic amino acid residues of opsin are responsible for the gamma-band CD. When ammonium sulfate is added to the sonicated disk membranes suspended in cholic acid solution, the alpha-band CD of rhodopsin decreases to about a third and the gamma-band CD increases remarkably. The CD spectrum goes back to the original one on eliminating ammonium sulfate from the solution with dialysis. However, the purified rhodopsin recovers native CD spectrum on addition of lipids extracted from disk membranes. The retinal-opsin interaction that induces optical activity depends upon the property of a local environment formed by lipid and detergent.

Animals↗
PubMed1977

Prefrontal neuronal activity during gazing at a light spot in the monkey.

We trained monkeys to make rapid key-release when a tiny light spot dimmed, so that they gazed at the spot until it dimmed. While the animal was performing the gaze task, we recorded unit activity in the prefrontal cortex and found that many neurons increased in discharge rate during the gaze trial (G neuron) with a variety of discharge patterns: many units were activated continuously during the gaze period; others were activated phasically only in an earlier portion of the gaze period. The activation of the G neurons was little influenced by stimulus parameters, such as the size, intensity and position of the light spot. However, it was dependent on behavioral state of the animal: error trials with delayed key-release showed a weak activation while extinction procedure induced enhanced activation in the initial several trials. The dependence of the activation on the behavioral state may suggest that the activation is at least involved in attentional process during gazing at a behavioral cue.

Animals↗
PubMed1977

Regeneration of rhodopsin in frog rod outer segments.

1. Bleaching/regeneration cycles were performed in perfused frog retina while the optical transmittance at suitable wave-lengths was measured continously. Rhodopsin was identified from its spectral absorbance, its photosensitivity and from the kinetics of its regeneration. 2. In the absence of the pigment epithelium regeneration was complete when not more than 2-5% of the rhodopsin initially present had been bleached. However, the cycles could be repeated to a total of regenerated rhodopsin exceeding that explicable on the utilization of stored chromophores. The rate of regeneration was fast, with 0-12 min-1 rate constant, following first order reaction kinetics. Under these conditions the cycle does not seem to involve stages beyond metarhodopsin II. With the moderate bleaching intensities used, half-time 53 min, the Bunsen-Roscoe law was obeyed up to 15 min, indicating a capacity for the photoproducts to be accomondated in situ for subsequent regeneration. 3. It is concluded that only substantial bleaches, which exceed that capacity, result in hydrolysed chromophores. These surplus chromophores become esterified and are temporarily taken up by the pigment epithelium to be re-entered into the visual cycle as fast as they can be processed by the regenerative machinery of the rod outer segments.

Animals↗