Pinealocyte

About: Pinealocyte is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 55609 citations.

Influence of Pineal Body on Melanoma of Hamsters

Abstract: JORDAN1,2 described the presence of melanic granules in pineal gland of sheep and del Rio-Hortega3–5 found pigment granules in the pinealocytes of human pineal as well as in other mammals. Santamarina and Meyer Arndt6 have more recently shown that the pigment in bovine pineal was true melanin. Ultra-violet spectral curves of bovine pineal melanin showed the same characteristics as those obtained from tyrosine melanin7,8. Pineal melanin differs slightly, however, from the melanin obtained from the choroid of the ox eye. Administration of pineal extract to tadpoles9,10, to toads10 and to fishes11 produces alteration in pigmentation. Thus it is possible that pineal body not only contains melanic pigment but is also capable of inducing some form of change in pigmentation. The hamster pineal body contains pigment granules in abundance (Fig. 1). On the basis of the investigations by Santamarina and Meyer Arndt, these can be assumed to be melanic granules. No data are available at present for the effects of pineal ablation or administration of pineal extract on pigmentation of hamsters. Isolated observations in other species have suggested a possible association between pineal body and pigmentation, however, and therefore a study was undertaken to observe the effect of pineal ablation on the growth and spread of a highly pigmented and spontaneously occurring neoplasm in hamsters.

The effect of continuous darkness and illumination on the function and the morphology of the pineal gland in the domestic pig. Part II: The effect on pinealocyte ultrastructure.

Abstract: OBJECTIVES: The characteristic feature of the pig pinealocytes is the presence of numerous membrane bounded bodies (MBB), which according to our previous results may be involved in the secretory activity. The present study was undertaken to analyze the effect of continuous darkness and illumination on the ultrastructure of the pig pinealocytes. MATERIAL AND METHODS: The study was performed on three groups of gilts. The first group (control) was kept under a cycle of 14hrs light (500 lx) and 10hrs dark per day. The second group was exposed to continuous illumination (500 lx). The third group was kept under red light with intensity less than 1 lx, which was considered as darkness. The pigs were kept for 14 days under above reported conditions and then slaughtered at 08:00. The point count analysis was used in quantitative studies of pinealocyte substructures. RESULTS: The exposition of pigs to continuous illumination resulted in the decrease in the relative volume of mitochondria and in the numerical density of multivesicular bodies as well as in the increase in the relative volume of MBB in pinealocyte cell bodies. The exposition to continuous darkness led to the increase in the relative volume of mitochondria and the numerical density of dense core vesicles as well as induced some changes in smooth endoplasmic reticulum in pinealocyte cell bodies. CONCLUSIONS: The obtained results point to mitochondria, MBB, multivesicular bodies, dense core vesicles and smooth endoplasmic reticulum as the structures of the pig pinealocyte, which are controlled by environmental light conditions.

d‐Aspartate Oxidase Localisation in Pituitary and Pineal Glands of the Female Pig

Abstract: Recent evidence has shown that d-aspartate modulates hormone secretion in the vertebral neuroendocrine system. Because only d-aspartate oxidase (DDO) can degrade d-aspartate, we determined DDO localisation in the pituitary and pineal glands to elucidate the control mechanisms of local d-aspartate concentration. Brain tissues and pituitary and pineal glands of the female pigs contained a similar DDO activity of 0.38–0.66 U/g protein. However, approximately ten-fold higher concentrations of d-aspartate (0.27–0.35 μmol/g protein) were found in both glands. To determine the distribution of immunoreactive DDO, we made a rabbit polyclonal antibody specific to porcine DDO using a recombinant porcine enzyme. DDO immunoreactivity was found in the cytoplasm of a subgroup of cells in the anterior and intermediate lobes, in a part of nerve processes and terminals in the posterior lobe, and in the cytoplasm of a small group of pinealocytes. We used dual-label immunocytochemistry to determine which pituitary hormones colocalise with DDO, and whether DDO and d-aspartate immunoreactivity is reciprocal. In the pituitary gland, almost all proopiomelanocortin-positive cells colocalised DDO, whereas only growth hormone-positive cells colocalised d-aspartate. d-Aspartate immunoreactivity was not detected where DDO immunoreactivity was found. The present study suggests that DDO plays important roles to prevent undesirable off-target action of d-aspartate by strictly controlling local d-aspartate concentration in the pituitary and pineal glands.

Leptin modulates norepinephrine-mediated melatonin synthesis in cultured rat pineal gland.

Abstract: Pineal melatonin synthesis can be modulated by many peptides, including insulin. Because melatonin appears to alter leptin synthesis, in this work we aimed to investigate whether leptin would have a role on norepinephrine- (NE-)mediated melatonin synthesis in cultured rat pineal glands. According to our data, cultured rat pineal glands express leptin receptor isoform b (Ob-Rb). Pineal expression of Ob-Rb mRNA was also observed in vivo. Administration of leptin (1 nM) associated with NE (1 µM) reduced melatonin content as well as arylalkylamine-N-acetyl transferase (AANAT) activity and expression in cultured pineal glands. Leptin treatment per se induced the expression of STAT3 in cultured pineal glands, but STAT3 does not participate in the leptin modulation of NE-mediated pineal melatonin synthesis. In addition, the expression of inducible cAMP early repressor (ICER) was further induced by leptin challenge when associated with NE. In conclusion, leptin inhibition of pineal melatonin synthesis appears to be mediated by a reduction in AANAT activity and expression as well as by increased expression of Icer mRNA. Peptidergic signaling within the pineal gland appears to be one of the most important signals which modulates melatonin synthesis; leptin, as a member of this system, is not an exception.

Light-Induced Changes in Pineal Gland N-Acetyltransferase Activity: Developmental Aspects

Abstract: In adult rats, light acting via a retino-pineal gland neural pathway influences pineal gland biochemistry in two ways: (1) it entrains endogenous circadian rhythms in melatonin biosynthesis to the environmental photoperiod and (2) exposure to even very brief periods of light during the nighttime rapidly suppresses the high levels of nocturnal melatonin production. The present studies were undertaken to determine precisely when photic stimulation first influences the enzymic activity of N-acetyltransferase (NAT), the pineal gland enzyme which rate-limits the overall biosynthesis of the hormone melatonin, and to examine some of the cellular mechanisms which might mediate light-induced effects in neonatal animals. Rats of different ages were either killed during the light phase or were exposed to darkness or light for 1 min during the dark phase of the lighting cycle, returned to their litters in darkness for 30 min and then killed. Pineal gland NAT activity in animals nocturnally exposed to 1 min of light was suppressed in animals 6 days of age or older. Nocturnal light exposure did not suppress enzyme activity in 3- to 5-day-old rats, even though these animals displayed clear light:dark differences in pineal gland NAT activity. Nocturnal light exposure also did not suppress nighttime levels of NAT activity in 7-day-old animals who had been bilaterally enucleated, suggesting that this effect is retinally mediated. Pretreatment of 7-day-old animals with the beta-noradrenoceptor agonist drug, isoproterenol, prevented the nocturnal light-induced suppression of NAT activity.(ABSTRACT TRUNCATED AT 250 WORDS)