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Biomedical subjects

W B Quay

Publications and source records attributed to W B Quay.

At least 37 records · Page 2Linked to original sources
PubMed1984

Seasonal changes in glycogen level and size of pinealocytes of the white-footed mouse, Peromyscus leucopus: a semiquantitative histochemical study.

Glycogen level in and size of pinealocytes of the feral, white-footed mouse Peromyscus leucopus, were studied by a semiquantitative histochemical method to determine whether seasonal changes exist in them under natural conditions, what temporal pattern they exhibit, and whether 24-hour changes in these parameters exist in different seasons, as shown in the laboratory dd-mice. Marked seasonal changes were seen in both glycogen levels and nuclear densities (ANOVA p less than 0.005). The size of pinealocytes at 09:00 to 10:00 showed one peak (and nadir) seasonal change, with the smallest size in winter (December and February) and a larger size in warmer seasons, with the maximum value in July. Glycogen level in pinealocytes at 09:00 to 10:00 showed bimodal seasonal changes, with lower levels in fall and spring and higher levels in winter and summer. In fall, a circadian trend in glycogen level in pinealocytes was seen, with a higher level at the end of the light period. In winter, the glycogen levels were very high at 09:00, 13:00, 17:00, and 21:00 examined and showed dampening of time-of-day differences. On the other hand, the size of pinealocytes followed a time-of-day change (P less than 0.005), being largest at 13:00 and smallest at 21:00. Thus, marked changes in quantitative structure and chemical activities, suggesting changes in functional activity, in pinealocytes were noted especially in severe, cold winter.

Acclimatization↗
PubMed1982

The pinealocyte nucleolus. Ultrastructural and stereological analysis of twenty-four-hour changes.

An ultrastructural and morphometric analysis was made of the nucleolar components in pinealocytes of 40 male Fischer rats sampled at eight times in an LD 12:12 photoperiod cycle. Comparisons of results from the eight times showed variation in estimated mean volume of the granular component of +/- 29%, and of the fibrillar component +/- 11%, in relation to daily means. Peaks in mean volume of total nucleolus and its granular component occurred at 1 h of light. Near maximal and minimal mean volumes of the fibrillar component both occurred during both light and dark. Fibrillar centers (nucleolar organizer regions) of different sizes were found at all sampling times. It is concluded that temporal patterns in 24-h changes in the nucleolar components are most prominent in the granular component, and are more complex than suggested by changes in total nucleolar size or mean dimensions, and than represented by a simple biphasic circadian rhythm. Examples of different stages in the migration of the granular component, and of possible sites of nucleo-cytoplasmic transfer of nucleolar material, are described.

Animals↗
PubMed1982

Stimulatory effects of melatonin on ependymal epithelium of choroid plexuses in golden hamsters.

Ependymal epithelial cells from the choroid plexuses (CPs) separately of lateral (I + II), IIIrd and IVth ventricles of male Golden Hamsters were studied by electron microscopy and morphometry. The 16 hamsters were distributed between three injections groups: vehicle only, 25 micrograms and 2500 micrograms melatonin (M) by subcutaneous injection daily at L11 to L11.75 in a LD 14:10 daily photoperiod. After 28 consecutive daily injections, animals were killed and the CPs were dissected, fixed and prepared for electronmicroscopy. Thirteen measures of the CP ependymal cells were made, by planimetry, morphometry or direct counting or linear measurement on the EM prints. Effects of melatonin occurred only on the cells from the lateral ventricles. Here M at high dosage caused cell swelling (averaging 50% increase in area), and other cellular changes were graded in relation to M dosage. These were increased (to 26%) in mitochondrial area per cell, and increased (to 50%) in length of apical microvilli. Since in other work the latter form a major locus of ouabain-sensitive Na+, K+-ATPase, it is suggested that M may possibly have a stimulatory effects on transport and related CSF secretory activities by these cells.

Animals↗
PubMed1982

Melatonin's inhibition of pituitary, adrenal, testicular and accessory gland growth in male golden hamsters: pineal dependence and organ differences with shielding and intracranial surgery.

Testes, accessory glands, pituitaries and adrenal glands from 101 male Golden Hamsters (55-65 days old) were weighed after 4 weeks of daily injections of vehicle or 25 microgram or 2500 microgram of melatonin, and 32-33 days after surgery. The surgical groups within each injection group were: (1) nonoperated (NO), (2) sham-pinealectomized (S), (3) sham-pinealectomized with black plastic shielding of the pineal region (S + Pl), (4) pinealectomized (PX), and (5) pinealectomized with black plastic shielding of the pineal region (PX + Pl). All injections were made between L11 and L11.75 in a fixed LD14:10 daily photoperiod. Absolute and relative organ weights were significantly depressed by 25 but not 2500 microgram melatonin. This effect of low dose melatonin was blocked by pinealectomy (PX, PX + Pl) in all four organ groups, but was blocked as well by the sham-operation (S, S + Pl) only in the case of the adrenal glands. Effects and organ weights in S animals were not modified in the S + Pl animals. But in vehicle-injected groups the S + Pl animals had significantly lower accessory organ weights in comparison with those of NO and S groups. These results aid in the further definition of the mechanisms of melatonin's physiological actions as a chemical mediator within neuroendocrine timing controls, and show that the mechanisms for melatonin's actions can differ in relation to eventual endpoint target tissue or organ studied.

Adrenal Glands↗
PubMed1981

Pineal atrophy and other neuroendocrine and circumventricular features of the naked mole-rat, Heterocephalus glaber (Rüppell), a fossorial, equatorial rodent.

Quantitative aspects of the microanatomy of the pineal gland and other neuroendocrine and circumventricular structures were studied in a small, reproductively suppressed, female Naked Mole-rat from central Kenya, Africa. The atrophic pineal is the smallest in absolute size (0.002135 mm3) of any so far described in a species of rodent, and in size relative to body weight is second only to that of another tropical species. The subcommissural organ and posterior collicular recess are also relatively small and less well differentiated than those in most other examined rodent species. In contrast, the subfornical organ, OVLT and median eminence are large and well vascularized. It is concluded that the pineal in this species follows the previously described trend among rodents of relatively smaller size in species whose centers of distribution are in lower latitudes. Although the pineal is atrophic, the Naked Mole-rat still exhibits 24-hour and seasonally timed patterns of behavior and seasonal reproduction. However, in this species these events are probably cued by moisture, temperature and social factors rather than by photic information.

Adaptation, Physiological↗
PubMed1980

Effect of methionine, glycine and serine on serine hydroxymethyltransferase activity in rat glioma and human neuroblastoma cells.

Human neuroblastoma SK-N-SH-SY5Y (5Y) and rat glioma (C6) cells were cultured with supplemental methionine, glycine, or serine for three to six days. Serine hydroxmethyltransferase (SHMT: L-serine: tetrahydrofolate 5, 10-hydroxymethyltransferase, EC 2.12.1) was assayed radiometrically in whole cell homogenates, crude supernatant fractions and crude particulate fractions. No significant changes in specific activity or cellular morphology were noted at methionine, glycine, or serine concentrations up to 16 mM. Serine concentrations of 20 and 40 mM led to significantly lower gliomal enzyme specific activities. This activity was unevenly distributed between soluble and particulate fractions, with 190 and 398 nmoles of HCHO formed per mg of protein per hour, respectively. Growth stage and time of incubation were major determinants of enzyme specific activity. C6 cells' specific activity rose slowly with increasing time in culture until cellular confluence. At this time there was a pronounced elevation in specific activity, occurring more rapidly in cells grown in 1.2 mM methionine. Intracellular amino acid analysis of C6 cells demonstrated a significant rise in methionine after four days in media containing 0.2 mM methionine. No appreciable diminution in the intracellular levels of glycine or serine occurred following incubation in excess methionine. It is concluded that SHMT-specific activity in C6 and 5Y cells is not regulated by glycine, serine, or methionine levels and that high concentrations of these amino acids (> 30 mM) are not detrimental to these cells derived from the CNS.

Animals↗
PubMed1980

Adrenal and hypothalamic dopamine-beta-hydroxylase activity in the hamster: evidence for species-distinctive day-night and post-pinealectomy differences in activity.

Dopamine-beta-hydroxylase (DBH) activities were measured in the adrenal gland and hypothalamus of the golden hamster (Mesocricetus auratus) by means of a sensitive radioenzymatic method. Groups of unoperated control (C), sham pinealectomized (SPX), and pinealectomized (PX) adult males were sacrificed shortly before (09:00 h) and after (11:00 h) the onset of darkness of the daily photoperiod of LD 12:12 (lights on 22:00 h to 10:00 h). In neither adrenal gland nor the hypothalamus were there any day-night changes in the C groups. Pinealectomy led to no significant differences in hypothalamic DBH activity either in light or in dark. However, intracranial surgery resulted in increased DBH activity in the adrenal gland, evident in both light and dark. Although this increase was greatest in the PX groups, intracranial surgery in SPX groups also showed a trend of increase in adrenal DBH, evident even one month after surgery. Such an increase, however, was not found in hypothalamic DBH in the same SPX groups. In both the adrenal gland and the hypothalamus, copper-sensitive endogenous inhibitors of DBH did not show any notable change in concentration, either in relation to the daily light-to-dark change or as a consequence of intracranial surgery. These and related results suggest that important interspecies variations exist in DBH activities in relation to diurnal changes, and also in control or modulation by pineal and other factors.

Adrenal Glands↗
PubMed1980

Experimental and spontaneous pineal tumors: findings relating to endocrine and oncogenic factors and mechanisms.

Pineocytomas have been induced in a high percentage of hamsters inoculated intracerebrally within 24 hours after birth with particular strains of a human papovavirus. Studies on biochemical and ultrastructural charactertistics and transformation of such experimentally induced pineal tumors have led to important conclusions and implications: (1) Many of the differentiated pineocytoma cells contained organelles and related structures that are characteristic of hamster pineocytes, and others that are reminiscent of possible phylogenetic precursors, including pineal photoreceptor cells. (2) An inverse relationship was noted between degree of cytological differentiation and level of hydroxyindole-O-methyltransferase (HIOMT) activity in the pineocytomas. (3) It is therefore apparent that even when pineal tumor formation leads to great increase in pinealocyte-like cells, their enzymatic capacity for synthesis fo melatonin, and possibly of other humoral products, may be only 4 to 7% of that of normal pinealocytes if they are of a relatively less differentiated type. A number of important and basic questions are accessible and remain to be investigated via experimental pineocytomas, such as: (1) nature and significance of cytological interactions within the pineal; (2) probable occurrences, correlations and transformations of other pineal biosynthetic and hormonal processes; (3) degree and nature of environmental (photic, circadian and circannual factors) and physiologic controls; and (4) kinds of modifications of pineal-related functions.

Acetylserotonin O-Methyltransferase↗
PubMed1980

Pineal effects on metabolism and glucose homeostasis: evidence for lines of humoral mediation of pineal influences on tumor growth.

Results from animal experiments support the hypothesis that pineal gland function can influence some aspects of tissue metabolism and glucose homeostasis. Evidence of pineal effects on particular endocrine and sympatheto-adrenal targets contributes to an understanding of indirect routes by which pineal activity can possibly affect the growth and activity of some kinds of tumors, in part through nutrient and metabolic effects in the tissue environment of the tumor cells.

Adrenal Medulla↗
PubMed1980

The invagination complex in nerve endings on adrenomedullary adrenaline cells: quantitative ultrastructural description, and analysis of changes with time-of-day and their modification by sham-surgery and pinealectomy.

This work describes a special ultrastructural feature, the invagination complex (IC), involving the plasma membrane of nerve endings on adrenomedullary adrenaline cells. Quantitative characteristics of the IC and their changes were studied in 122 male albino (Holtzman strain) rats in 3 surgical groups: normal (non-operated, NO) sham-operated (SO) and pinealectomized (PX), all maintained in a standardized daily photoperiod (light : dark 12 : 12 h). Animals were decapitated 14 days postsurgery and at 8 specific times during the light : dark cycle. Left adrenal glands were removed, dn strain) rats in 3 surgical groups: normal (non-operated, NO) sham-operated (SO) and pinealectomized (PX), all maintained in a standardized daily photoperiod (light : dark 12 : 12 h). Animals were decapitated 14 days postsurgery and at 8 specific times during the light : dark cycle. Left adrenal glands were removed, dn strain) rats in 3 surgical groups: normal (non-operated, NO) sham-operated (SO) and pinealectomized (PX), all maintained in a standardized daily photoperiod (light : dark 12 : 12 h). Animals were decapitated 14 days postsurgery and at 8 specific times during the light : dark cycle. Left adrenal glands were removed, dissected and prepared for electron microscopy. In section profiles the diameter of each IC was usually 0.12-0.40 micrometers, and the depth 0.2-1.0 micrometers. They were frequently seen to be located near the synaptic complex (or the active zone). Coated pits, about 50 nm wide and 60 nm deep, often opened near the bottom of the invaginations of the IC. In NO animals, relative number and depth of the ICs showed daily rhythmic changes with minimal values about 1 h after onset and maximal (acrophase) values 3--5 h later (P less than 0.02 to less than 0.005, depending on index or measure). These changes occurred 3--5 h earlier, but less apparently, in SO animals, and appeared to be more greatly modified and dampened in PX animals. Two-way analysis of variance (ANOVA) and t-tests applied to 11 kinds of indices derived from counts and measurements of the ICs, support the differences between surgical groups, at least in many instances (P less than 0.05 to less than 0.001). It is concluded that the IC is a characteristic and dynamic feature of the nerve terminals and that it may possibly have a role in such phenomena as recycling of synaptic vesicles or related membrane constituents. It is also concluded that significant time-of-day and neuroendocrine effects are demonstrable in these structures, and that the time-of-day effects shown in these chronic studies have importance in the design of acute experiments designed to further test the functional relations and importance of ICs.

Adrenal Medulla↗
PubMed1979

Cystathionine synthase in rat brain: regional and time-of-day differences and their metabolic implications.

In relation to concern for probable interrelations of cystathionine synthase (CS, EC 4.2.1.21) and methionine, one-carbon, and 5-hydroxytryptamine metabolism, we have investigated tissue and time-of-day differences in CS activity in the laboratory rat under standardized conditions. Liver, kidney, and pancreas had highest CS activities; nine regions of the CNS had mean activities ranging from 4.5% (lumbosacral cord) to 24.5% (hypothalamus) of mean hepatic activity; pituitary and adrenal glands lacked detectable CS activity. Although significantly lower CS activity occurred in liver (9%, P less than 0.050) and kidney (13%, P less than 0.025) during the interval two hours before to two hours after the daily onset of darkness, no significant changes were found in hypothalamus, cerebellum, or medulla oblongata. Regional CNS differences in CS activity appeared to be without correlation in relation to published data on relative contents of 5-hydroxytryptamine, tryptophan 5-hydroxylase (EC 1.14.16.4), 5,10-Methylene reductase (N5-methyltetrahydrofolate-NAD-oxidoreductase, (EC 1.1.1.78), or 5-methyltetrahydrofolate. Therefore, among CNS regions examined, a critical deficiency in ability to metabolize a homocysteine load is considered to be unlikely under normal conditions.

Animals↗
PubMed1979

Effects of pinealectomy and pineal incubation medium and sonicates on insulin release by isolated pancreatic islets in vitro.

The present studies were designed to investigate the mechanism of previously-reported nocturnal hyperinsulinemia in the pinealectomized rat. Isolated islets were obtained from anesthetized control, sham-pinealectomized and pinealectomized rats, with 5 rats per surgical groups, during the early dark phase of the daily lightdark cycle. Batches of 3 islets each were incubated in various combinations of 2, 10 or 30 mM glucose with control buffer, medium in which cerebral cortex or pineal glands had previously been incubated for 2 hours, or sonicates of these same tissues. Insulin released into the culture medium was measured by radioimmunoassay. A significant hypersecretion of insulin was demonstrable in the islets from the pinealectomized animals. A stimulatory effect of both pineal medium and sonicates upon insulin release was similarly observed. Neither of these effects displayed an interaction with the concentration of glucose in the islet incubation medium and they, therefore, appear to be mediated by a mechanism which operates independently of stimulation by glucose. These results indicate that the rat pineal gland can exert direct effects upon insulin release from the islets, possibly through a humoral route. Further studies are in progress to characterize the nature and mode of action of the insulinotropic agent present in and released from the pineal gland.

Animals↗
PubMed1979

Androgens and brain differentiation. Effects of testosterone on protein synthesis in neonatal rat hypothalamic and cerebral slices.

Protein synthetic activity of anterior hypothalamic and neocortical brain slices from androgenized neonatal female rats was studied in vitro in an attempt to clarify the mechanism of action of testosterone on the developing hypothalamus. The short-term effects of testosterone propionate injections of the animals on the protein synthetic activity of the slices were assayed by means of incorporation of 14C-leucine into acid-insoluble protein. Although a high dose (1 mg/animal) of testosterone propionate stimulated increased incorporation in neocortical and anterior hypothalamic slices, a lower dose and other approaches failed to demonstrate a stimulation regionally specific to the anterior hypothalamus. It is concluded that if testosterone has specific stimulatory effects on protein synthesis in the anterior hypothalamus of neonatally androgenized rats, these are not readily demonstrable by methods used with other steroid target tissues.

Animals↗