PubMed Health⌕ Search

Biomedical subjects

A Fiorentini

Publications and source records attributed to A Fiorentini.

At least 37 records · Page 2Linked to original sources
PubMed1985

Pattern ERG in the monkey after section of the optic nerve.

Electroretinographic responses (ERG) to homogeneous light flashes and to alternating gratings were recorded from either eye of monkeys in which one optic nerve had been previously sectioned. Three weeks after optic nerve section the ERG response of the operated eye to alternating gratings was drastically reduced in amplitude and 5 weeks after surgery it was reduced to noise level. The uniform field ERG was unaffected. Histological examination of whole-mounted retinas of monkeys sacrificed 6 and 8 weeks after optic nerve section showed a loss of ganglion cells in the operated eye. It is concluded that the integrity of ganglion cells is essential for the generation of a normal ERG response to gratings.

Animals↗
PubMed1985

Dopaminergic drugs improve human visual contrast sensitivity.

Effects of dopaminergic drugs (L-dopa plus benserazide, or nomifensine) on human visual function have been tested in healthy volunteers by measuring the psychophysical contrast sensitivity for sinusoidal gratings of various spatial frequencies. After drug administration the contrast sensitivity improved in all subjects over a limited range of medium to high spatial frequencies.

Adult↗
PubMed1978

Selective impairment of contrast sensitivity in kittens exposed to periodic gratings.

1. Kittens were exposed to a periodic grating orientated vertically during the critical period of their life. 2. At the end of the critical period the amplitude of the response to drifting gratings was found to be reduced at the spatial frequency of exposure in multi-unit and in some single unit recordings at lateral geniculate level. 3. The contrast sensitivity measured with behavioural methods also showed a depression at the spatial frequency of exposure. 4. An analysis of the preferred stimulus orientation of cortical units in area 17 showed that all orientations were represented.

Action Potentials↗
PubMed1978

Binocular vision tested with visual evoked potentials in children and infants.

Evoked potentials (EP's) in response to phase-alternating gratings were recorded from normal and stereoblind or stereodefective subjects (adults and children) under monocular and binocular viewing conditions. The amplitude of the binocular EP was found to exceed the larger monocular EP in normal but not in stereodefective subjects, no matter whether the amplitudes of the two monocular EP's were the same or not. This finding provides an objective method for screening out defects of binocular vision. EP's recorded from a group of infants 2 to 18 months old suggest that a larger amplitude of the binocular EP, as compared with the monocular EP's, is the norm even in the earliest period of life.

Adult↗
PubMed1976

Asymmetry of motility of the eyes and change of binocular properties of cortical cells in adult cats.

Immobilization of one eye in the adult cat following section of the oculomotor cranial nerves causes a decrease of the proportion of binocularly activated cells in the striate cortex. This change in the binocular properties of cortical cells also takes place if the animal is deprived of vision from the day on which the nerves are cut to the day of the electrophysiological recording. No similar change in the proportion of binocular cortical cells is observed in cats where both eyes have been immobilized.

Animals↗
PubMed1975

Sensitivity of central chemoreceptors controlling blood glucose and body temperature during glucose deprivation.

1. The rise in blood glucose and the fall in body temperature which follows the injection of a glucose analogue, 2-deoxy-D-glucose (2-DG) into the lateral cerebral ventricle (I.C.V) of unanaesthetized rats were studied and found to be dose-dependent. These 2-DG induced responses are elicited by the impairment of glucose metabolism within central "glucoreceptors'. 2. 2DG induced hyperglycaemia and hypothermia were completely prevented and even the converse effects occurred when fivefold equimolar amounts of D-fructose were simultaneously injected I.C.V.; fructose, at equimolar doses, did not modify the effects of 2-DG. 3. D-xylose and D-ribose, even at high doses, did not influence 2-DG hyperglycaemia, but increased slightly the 2-DG induced hypothermia. This suggests that the pentose phosphate pathway is unable to support the metabolism within the glucoreceptors. 4. Pyruvate suppressed the 2-DG induced hyperglycaemia with a marked delay, while acetate (as ethyl ester) and a mixture of malate plus oxaloacetate did not prevent 2-DG induced effects. These results may be accounted for by the low dosage used. 5. Acetoacetate and 3-hydroxybutyrate did not prevent 2-DG hypothermia and hyperglycaemia. 6. An effective prevention of the 2-DG induced hyperglycaemia and hypothermia was achieved with fumarate and glutamate, indicating that the stimulation of the Krebs cycle within "glucoreceptors' removes the glucoprivic effects. 7. The results indicate that prevention of 2-DG induced effects occurred only with alternate source of metabolic fuel which can support high respiratory rates in brain tissue. It is concluded that central chemoreceptors are not specifically responsive to glucose, or hexoses, but to the rate of oxidative metabolism.

Acetates↗