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Biomedical subjects

R Granit

Publications and source records attributed to R Granit.

At least 19 recordsLinked to original sources
PubMed1992

Nitric oxide, an inhibitor of lipid oxidation by lipoxygenase, cyclooxygenase and hemoglobin.

The present study demonstrated that nitric oxide, which is an important mammalian metabolite, can inhibit oxidation by lipoxygenase, cyclooxygenase and hemoglobin. The inhibition is manifested as a lag-phase that is reversible. The inhibitory effect of nitric oxide on lipoxygenase and cyclooxygenase seems to derive from i) the capability of .NO to reduce the ferric enzyme to the ferrous form, which is inactive; ii) competition for the iron site available for exogenous ligands; and iii) the radical scavenging ability of the nitroxide radical. Nitric oxide may act as a modulator of the arachidonic acid cascade and in the generation of oxygen-active species.

Animals↗
PubMed1991

Nitric oxide as an antioxidant.

Benzoate monohydroxy compounds, and in particular salicylate, were produced during interaction of ferrous complexes with hydrogen peroxide (Fenton reaction) in a N2 environment. These reactions were inhibited when Fe complexes were flushed, prior to the addition in the model system, by nitric oxide. Methionine oxidation to ethylene by Fenton reagents was also inhibited by nitric oxide. Myoglobin in several forms such as metmyoglobin, oxymyoglobin, and nitric oxide-myoglobin were interacted with an equimolar concentration of hydrogen peroxide. Spectra changes in the visible region and the changes in membrane (microsomes) lipid peroxidation by the accumulation of thiobarbituric acid-reactive substances (TBA-RS) were determined. The results showed that metmyoglobin and oxymyoglobin were activated by H2O2 to ferryl myoglobin, which initiates membrane lipid peroxidation; but not nitric oxide-myoglobin, which, during interaction with H2O2, did not form ferryl but metmyoglobin which only poorly affected lipid peroxidation. It is assumed that nitric oxide, liganded to ferrous complexes, acts to prevent the prooxidative reaction of these complexes with H2O2.

Antioxidants↗
PubMed1978

The significance of antidromic potentiation and induced activity in the retina.

It is argued that "The significance of antidromic potentiation and induced activity in the retina" (the title of this article) concerns two identical effects and that both are the outward sign of the existence of a specific organization in the retina. For this reason they can serve as a valuable criterion for identifying activity in this organization. This activity is assumed to be in the nature of a self-excitation by positive feedback in the amacrine circuits of certain Y-cells. Relevant literature has been reviewed. These Y-cells, whose spectral response curve is of the dominator type, play a prominent role in stimulation by intermittent light and in the perception of luminosity. Several properties of intermittent stimulation are mentioned and held to motivate a renewal of the attention of visual experimenters to 'flicker' and its after-effects.

Action Potentials↗
PubMed1975

The functional role of the muscle spindles--facts and hypotheses.

A review is given of recent work on the functional role of muscle spindles in the control of movement. The fusimotor neurons (gamma motoneurons) maintain the spindles in a state of responsiveness to length and to rate of change of length of muscle. Centrifugal control of muscle spindles takes two forms: first, a steady or slowly fluctuating tonic firing of fusimotor neurons, as a part of general states of arousal or readiness-to-move, independent of the firing of skeletomotor neurons (alpha motoneurons), and not related in time to specific movements; secondly, a precise coactivation of skeletomotor and fusimotor neurons (alpha-gamma linkage) which is related to the time-course of specific movements. Both types are likely to be important in man. Recent work on the connexions at the segmental level between spindle inputs, descending pathways, interneurons, gamma motoneurons and alpha motoneurons is reviewed and discussed, with special attention to work on man. These segmental circuits, rather than their individual components, are the units which are operated by reflexes and by central programmes for movemenst.

Action Potentials↗