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Biomedical subjects

S Binkley

Publications and source records attributed to S Binkley.

54 records · Page 3Linked to original sources
PubMed1981

Circadian rhythm in pineal N-acetyltransferase activity: phase shifting by light pulses (I).

N-Acetyltransferase activity (NAT) in the pineal gland has a circadian rhythm which is responsive to environmental light-dark cycles. The rhythm entrains to (synchronizes with or is phased by) light-dark cycles. To assess the means by which phase resetting is accomplished, the phase response of the pineal NAT rhythm to light pulses was examined using chicks (Gallus domesticus). When 4-h light pulses were imposed on chicks at intervals over a 24-h period of darkness and the time of the next rise in NAT was determined in darkness, it was found that: (1) pulses early in the subjective dark time delayed the rise in NAT, (2) pulses late in the subjective dark time advanced the rise in NAT, and (3) pulses in the subjective light time were relatively ineffective. These results are typical of a circadian phase response curve and show that an enzyme with a circadian rhythm is similar to other circadian rhythms studied.

Acetyltransferases↗
PubMed1977

Timekeeping by the pineal gland.

N-Acetyltransferase, an enzyme involved in melatonin production in the pineal gland, exhibits a circadian rhythm in chickens with peak values in the dark-time and low values during the light-time, commencing at lights-on. When pineal glands of chickens killed during the dark-time (with high N-acetyltransferase activity) were organ-cultured, there was a decline in enzyme activity to light-time values. Regardless of the time of the dark at which the chickens were killed, the enzyme activity reached light-time levels at precisely the same time.

Acetyltransferases↗
PubMed1977

Cultivation of mammalian pineal cells: retention of organization and function in tissue culture.

By means of a newly developed method of cultivating pineal tissue in vitro, the types of cells which comprise rat pineal glands have been identified. Previous in vitro studies have involved short-term culture more suitably called "organ culture" and provide no means of assessing the contribution of a putative "pineal" cell versus any other cell type found in the cultures. Short-term outgrowths of minced rat pineal glands provided a reproducible and easily dissociated source of pineal-derived cells. In monolayer culture these cells continued to have pineal enzyme activities which were sensitive to pineal-activating substances, and the cells aggregated to mimic the lobular organization of intact glands. Two types of aggregates were found, each composed of a single morphological cell type. In addition to the transient appearance of skeletal muscle straps, connective tissue and neural/glial tissue was consistently found. The cell types are discussed in relation to their in vivo counterparts.

Acetylserotonin O-Methyltransferase↗
PubMed1976

Pineal gland biorhythms: N-acetyltransferase in chickens and rats.

Circadian rhythms have been identified in chemical factors involved in the metabolism of serotonin in the pineal gland. The rhythms are reviewed with respect to their characteristics and regulation by environmental lighting in vertebrates. Special emphasis has been given to the rhythm in pineal N-acetyltransferase activity in rats and chickens. This rhythm is not only apparent in a light-dark cycle in some birds and mammals, it also persists in constant dark. In constant light the rhythm is lost. The action of light is via the eyes in rats but extraretinal photoreceptors are involved in chickens. The details of the N-acetyltransferase activity rhythm include the presence of a refractory period for the rise in dark-time enzyme activity and the rapid turnoff of high dark-time activity by light. The N-acetyltransferase clock can be reset with a period of constant light in the chicken. Neural regulation of the rhythm in rats involves the suprachiasmatic nucleus and the superior cervical ganglion; in chickens, the ganglion is not necessary for the rhythm in light-dark cycles and the suprachiasmatic nucleus has not been studied.

Acetylserotonin O-Methyltransferase↗
PubMed1975

Regulation of pineal rhythms in chickens: refractory period and nonvisual light perception.

Pineal serotonin N-acetyltransferase activity and melatonin content exhibit marked daily rhythms in chickens; peak values occur during the period of low locomotor activity which coincides with dark in a 24-h light-dark regime. We studied the regulation of these daily rhythms by measuring pineal serotonin N-acetyltransferase activity, hydroxyindole-O-methyltransferase (HIOMT) activity, and melatonin content in experiments in which birds were exposed to light-to-dark and dark-to-light transitions at atypical times. We observed that there is a refractory period for dark-initiation of the increase in pineal N-acetyltransferase activity and melatonin content. We also learned that a dark-to-light transition causes a rapid decrease in dark-elevated pineal N-acetyltransferase activity and melatonin content. The rapid decrease occurs in blinded chickens as well as sighted ones. HIOMT activity did not change consistently in any of the experimental treatments.

Acetyltransferases↗
PubMed1975

Regulation of pineal rhythms in chickens: effects of blinding, constant light, constant dark, and superior cervical ganglionectomy.

Pineal serotonin N-acetyltransferase activity and melatonin content exhibit marked daily changes in chickens; peak values occur during the period of low locomotor activity which coincides with dark in a 24-hour light-dark cycle. The photic and neural regulation of these daily changes were studied by measuring pineal serotonin N-acetyl-transferase activity, hydroxyindole-O-methyltransferase (HIOMT) activity, and melatonin content in experiments in which chickens were subjected to light-dark cycles, constant light, and constant dark and were surgically blinded or superior cervical ganglionectomized. It was found that: 1) The daily changes in N-acetyltransferase activity and melatonin content appear to persist in constant dark, and they disappear in constant light. 2) The eyes are not necessary for photic control of the daily changes, and the effect of constant light on N-acetyltransferase activity and melatonin content may be non-visual, that is, the eyes not being necessary. 3) The occurrence of the daily change in N-acetyltransferase activity and melatonin content does not require the superior cervical ganglia; the persistence of the changes in constant dark, however, may require the ganglia. 4) HIOMT activity was lower in constant light than in light-dark cycles and lower still in constant dark than in constant light. Neither the presence of the eyes nor the superior cervical ganglia affected HIOMT activity, as previously reported.

Acetylserotonin O-Methyltransferase↗
PubMed1971

Pineal function in sparrows: circadian rhythms and body temperature.

Deep body temperature of the house sparrow, Passer domesticus, was monitored continuously by radio telemetry. Pinealectomy abolished the normal circadian rhythm of body temperature in constant darkness, and significantly altered the amplitude of body temperature rhythms entrained to light cycles. The body temperature minima of pinealectomized birds never fell as low as those of unoperated birds regardless of the light conditions; the temperature maxima of both normal and pinealectomized birds were higher in light than in darkness. In sparrows the pineal organ is essential to the normal function of the biological clock controlling both activity and body temperature rhythms and may be directly involved in thermoregulation.

Animals↗