Search PubMed⌕ Search

Biomedical subjects

C L Ralph

Publications and source records attributed to C L Ralph.

At least 37 records · Page 2Linked to original sources
PubMed1975

Parietal eyes in lizards: zoogeographical correlates.

Lizards without parietal eyes tend to be restricted to low latitudes, whereas lizards with parietal eyes are successful at higher latitudes also. These zoogeographical data, along with current theories of parietal eye physiology, strongly suggest that the overall significance of the parietal eye to lizards as a group is that it facilitates survival at higher latitudes, thus making possible the exploitation of a wider variety of habitats.

Adaptation, Biological↗
PubMed1975

Pineal and serum melatonin at midday and midnight following pinealectomy or castration in male rats.

Melatonin has been extractkd by chloroform from rat serum and quantified by the Rana pipiens tadpole bioassay. Like pineal melatonin, serum melatonin was high at mid-dark and low at mid-light. This finding suggests a diurnal rhythm of serum melatonin in the rat. Serum samples obtained at mid-dark had melatonin levels ranging from 0.02 to 0.05 ng per ml of serum. When rats were pinealectomized, melatonin activity in the serum was abolished. Thus, rat serum melatonin may originate primarily from the pineal. There was no significant change in pineal melatonin content nor in serum melatonin concentrations 7 or 12 days following orchidectomy.

Animals↗
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↗
PubMed1970

Pineal function and oviposition in Japanese quail: superior cervical ganglionectomy and photoperiod.

Bilateral ablation of the superior cervical ganglia appears to deprive the pineal body of sympathetic innervation. Although this procedure presumably interrupts the neural circuit for transmission of optic information to the pineal, oviposition rates of ganglionectomized females exposed to stimulatory (15-hour) or to nonstimulatory (4-hour) daily photoperiods do not differ from those of the controls.

Animals↗