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Biomedical subjects

C L Ralph

Publications and source records attributed to C L Ralph.

At least 19 recordsLinked to original sources
PubMed1986

Epithalamus of the nine-banded armadillo, Dasypus novemcinctus.

The epithalamus of embryonic, neonatal and adult nine-banded armadillo (Dasypus novemcinctus) was examined for evidence of pineal-like tissue. The evagination of the diencephalic roof (the anlage of the epiphysis) was not found in any embryonic specimens. In the adult brain, the epithalamus is dominated by the sub-commissural organ (SCO) which is surrounded entirely by the posterior commissure. At the most caudal aspect of the SCO, previous investigators have observed pineal-like tissue. Using pineal-specific staining techniques however, we found no evidence of this tissue. Because the armadillo produces melatonin in a rhythmic manner, exhibits exacting circadian rhythms, and shows altered rhythms when exposed to exogenous melatonin, we believe other organs, perhaps the retina or Harderian gland, must be involved in maintaining the coordinated melatonin titer.

Animals↗
PubMed1985

Thermoregulatory responses to photoperiod by kangaroo rats (Dipodomys ordii): influence of night lighting on nonshivering thermogenesis and resting metabolism.

The influence of photoperiod on resting oxygen consumption and nonshivering thermogenesis of winter-acclimatized kangaroo rats was determined by exposing freshly captured animals to 10-week controlled photoperiod treatments. Three treatments were employed: 1) long days (LD) = 16L:8D, 2) short days (SD) = 8L:16D, and 3) short days interrupted with 15 min light at midnight (SDL). Thermoneutral oxygen consumption was uninfluenced by treatment, and posttreatment values were not different from pretreatment values. Below thermoneutrality, mean values for oxygen consumption and norepinephrine(NE)-induced thermogenesis each were significantly greater in the SD group than they were in either the LD or SDL groups. Furthermore, oxygen consumption of LD and SDL groups, and NE-induced thermogenesis of LD and SDL groups were indistinguishable. Posttreatment oxygen consumption and NE-induced thermogenesis of the SD group were not different from pretreatment values. These results indicate that thermogenic capacities of kangaroo rats are strongly influenced by photoperiod. The similarities of responses by the LD and SDL groups indicate that the length of the dark period is of importance, and indirectly support suggestions that the pineal gland, through its nocturnal secretion of melatonin, may be involved in the transduction of photic information.

Animals↗
PubMed1982

Circadian rhythms and the effects of exogenous melatonin in the nine-banded armadillo, Dasypus novemcinctus: a mammal lacking a distinct pineal gland.

Circadian rhythms of body temperature, activity and oxygen consumption were recorded in the nine-banded armadillo, Dasypus novemcinctus, a mammal lacking a distinct pineal gland. The rhythms were entrained by light-dark cycles and appeared to be phase-coupled. Under constant illumination, the animals displayed free-running circadian rhythms with period lengths of slightly less than 24 hr. Melatonin implants caused a lengthening of the free-running period of activity and body temperature. The occurrence of a "normal" circadian rhythmicity in the armadillo indicates that the pineal organ is not necessary for the circadian organization of this animal whereas melatonin of non-pineal origin may have a role.

Animals↗
PubMed1980

Nonpineal melatonin in the alligator (Alligator mississippiensis).

All living and most fossil representatives of the reptilian subclass Archosauria lack pineal bodies. Arrhythmic, low-level, nonpineal melatonin is present, however, in the blood of Alligator mississippiensis. Although pineal bodies have been implicated in circadian phenomena, these results suggest that arrhytmic melatonin in alligators may not be involved incircadian events and indicate that the pineal is not the only source of the hormone melatonin. The evolutionary loss of the pineal in Archosauria occurred during the Mesozoic, and era noted for its seasonal stability. Arrhythmic melatonin titers inalligators and pineal loss in alligators and other archosaurs may be related to Mesozoic seasonal stability.

Alligators and Crocodiles↗
PubMed1980

Independent effects of the pineal and a bacterial pyrogen in behavioural thermoregulation in lizards.

The pineal complex of lizards is comprised of an extracranial photoreceptive structure known as the parietal eye, and an intracranial pineal organ which is homologous to the pineal gland of birds and mammals. Studies have shown that removing the parietal eye or severing the parietal nerve causes lizards to select higher temperatures when allowed to thermoregulate behaviourally in thermal or photothermal laboratory gradients. Although comparable studies involving removal of the lizard pineal organ have not previously been attempted, field data indicate that pinealectomy may have an antagonistic effect to parietalectomy. We present evidence here which shows that (1) following pinealectomy, collared lizards (Crotaphytus collaris) behaviourally select or prefer lower temperatures than their controls in thermal laboratory gradients, and (2) the effect of surgical treatment is independent of the effects of a behavioural fever-inducing substance which elevates by a fixed amount the environmental temperatures selected.

Animals↗
PubMed1979

Melatonin synthesis by the retina.

Melatonin fulfills many of the criteria for classification as a hormone. Until recently it was considered to be elaborated exclusively by pineal organs. Melatonin synthesis by other tissues has been indicated but not demonstrated unequivocally. Trout retinas in a whole-organ culture system in vitro synthesized tritiated melatonin from a substrate containing tritiated serotonin. This raises the possibility that the trout retina is an endocrine organ.

Animals↗
PubMed1978

The pineal-paraphyseal complex of sea turtles. I. Light microscopic description.

The pineal-paraphyseal complex of sea turtles is an impressively large structure which projects dorsally and anteriorly above the prosencephalon. The complex was examined by light microscopy in several age classes of green sea turtles (Chelonia mydas) and from juvenile loggerhead turtles (Caretta caretta). The paraphysis is extensively fused to the distal portion of the pineal body, suggesting an interrelated function for these two tissues. No duct or canal was observed connecting the pineal lumen to the third ventricle. Two pineal cell types are described which appear to correspond to the neuroglial supportive cells and the secretory rudimentary photoreceptor cells of other amniotic vertebrates. A possible luminal secretion in the form of apical protrusions is produced by the latter cell type. No typical photoreceptive outer segments were observed.

Animals↗
PubMed1978

Cytology of the pineal gland: changes produced by various treatments.

The cytological appearance of the pineal body is related to stage of development or age, time of day, exposure to illumination, season of the year, and reproductive state. Experimental manipulations that alter the normal cytology of the pineal include hypophysectomy, administration of any of several hormones or drugs, blinding, denervation and exposure to stressful influences such as heat or cold. The effects of blinding are similar to the effects of continuous darkness on the pineal's cytology. Ultrastructural examinations reveal a number of changes in the organelles, especially an increased number of vesicles and complex membranous whorls. These features suggest heightened activity and generally are coincident with sexual quiescence. Membranous whorls also may be induced by cold exposure. Prolonged or continuous illumination leads to a reduction in the size of pinealocytes and to changes in their organelles that suggest reduced activity. Such alterations can often be correlated with heightened sexual activity. Sympathetic denervation of pineal glands also results in atrophy of the pinealocytes. Reproductive condition is reflected in the appearance of the pinealocytes. The estrous cycle, pregnancy, castration and the administration of gonadotropins or gonadal steroids affect pinealocyte structure. A feedback system involving the gonads and pineal gland is indicated.

Aging↗
PubMed1976

Body temperature of the lizard (Anolis carolinensis): effect of parietalectomy.

Thermal behavior of parietalectomized, sham-parietalectomized or intact lizards (Anolis carolinensis) was recorded in a test chamber containing moving photothermal gradients. Following parietalectomy, animals chose significantly higher temperatures than sham-parietalectomized or intact control animals, which chose lower and statistically identical temperatures. When pre-surgical and post-surgical means are compared within groups, the eccritic temperature was 2.10 degrees C higher following parietalectomy, 0.72 degrees C higher following sham-parietalectomy, and 0.31 degrees C higher in intact controls during the post-operative measurements. The effects of parietalectomy indicate that the parietalpineal complex may be involved in behavioral thermoregulation by precisely regulating exposure to heat sources (e.g. sunlight).

Animals↗