Presence of a metallothionein-like protein in the bovine pineal gland

Summary The high concentration of zinc in the bovine pineal gland prompted us to investigate the existence of a zinc-binding protein in this organ. In this study, we report that the subcellular distribution of zinc in the bovine pineal gland is nonuniform, with the crude nuclear, mitochondrial, microsomal, and supernatant fractions having 0.264±0.038, 0.160±0.019, 0.130±0.016, and 0.287±0.010 g zinc/mg protein, respectively. Furthermore, gel filtration studies using Sephadex G-75 and a 105,000 g supernatant fraction revealed two zinc binding protein peaks that bind 1.7 and 3.7 g Zn⁺⁺/mg protein, respectively. Furthermore, purification of the protein peak with an elution volume (ve/vo) of 2.06 on anion exchange chromatography (DEAE-A 25) yielded a single protein peak which binds 10 g zinc/mg protein. The comparative high performance liquid Chromatographic (HPLC) profiles of the zinc-induced hepatic metallothionein isoform I (retention time=17.39 min) and of the bovine pineal metallothionein-like protein isoform I (retention time=17.49 min) are similar. Since zinc is a potent inhibitor of sulfhydryl-containing enzymes and receptor sites, we investigated the effects of zinc and found that it inhibited the binding of [³H]glutamate (IC 50=80 M) and of [³H]spiroperidol (IC 50=0.6 mM) to the pineal membranes. The results of these studies are interpreted to indicate that the bovine pineal gland possesses an active and dynamic zinc homeostatic mechanism, whose precise function(s) remain(s) to be delineated.     

Platelet 5-HT(2A) receptors in schizophrenic patients with and without neuroleptic treatment

It has been suggested that abnormal function of the serotonergic system may be implicated in the pathophysiology of schizophrenia. In order to examine the role of this system in schizophrenia, we have determined 5-HT(2A) receptors on human platelets of 20 control subjects and 37 schizophrenic patients by using [3H]spiperone and ketanserin. The data showed that the maximum number (B(max)) of 5-HT(2A) receptors for schizophrenic patients without neuroleptic therapy was significantly higher than that for control subjects. The B(max) values for [3H]spiperone binding to platelets of schizophrenic patients on butyrophenone, phenothiazine, benzisoxazole and thioxanthene therapies were significantly lower than those obtained from the drug-free group, but were comparable to control values. The effect of various medication periods on platelet 5-HT(2A) receptors was also examined. We found that after 2-4 weeks, 1-4 months, 4-12 months and more than 1 year of neuroleptic treatments, the B(max) values were significantly decreased when compared with values in the drug-free group. The present results indicate that treatment with various types of neuroleptics decreases the hypersensitivity of platelet 5-HT(2A) receptors. Significant clinical improvements occurred in all types of neuroleptic-treated groups and for all different treatment durations in this study. The precise mechanisms of how neuroleptics achieve their therapeutic effects still need to be further delineated.     

Increased hand washing reduces influenza virus surface contamination in Bangkok households, 2009–2010

Within a hand‐washing clinical trial, we evaluated factors associated with fomite contamination in households with an influenza‐infected child. Influenza virus RNA contamination was higher in households with low absolute humidity and in control households, suggesting that hand washing reduces surface contamination.     

The presence and actions of opioid receptors in bovine pineal gland

The mammalian pineal gland and its main hormone, melatonin, working in conjunction with the hypothalamic suprachiasmatic nuclei, synchronize circadian rhythm and hence refine numerous physiological and biochemical parameters. An interaction among melatonin, opioids, and analgesia has been suspected for many years, since during nighttime, when the level of melatonin is high, the mammals are less sensitive to pain. In studying this phenomenon further, we have identified a single population of opioid receptors in the bovine pineal gland using [3H]-diprenorphine and other ligands. The receptors have a dissociation equilibrium constant (Kd) of 1.36 +/- 0.31 nM and a density (Bmax) of 17.93 +/- 5.22 fmol/mg protein. In competitive experiments, the concentration of drugs required to inhibit 50% of the [3H]-diprenorphine binding (IC50) in descending order of potency was found to be naltrexone > fentanyl > naloxone > nalbuphine > morphine > nalorphine > DAGO > dynorphin > metenkephalin. In order to delineate the function of the opioid system in the pineal gland, the effects of both opioid receptor agonists and antagonists on the basal activity of N-acetyltransferase were examined in the bovine pineal explants in culture. Morphine, an opioid receptor agonist, increased significantly the activity of N-acetyltransferase in a dose-dependent fashion. In addition, the stimulatory effect of morphine was inhibited by naloxone, an opioid receptor antagonist. The results of these studies indicate the existence of pineal opioid receptors, which play a pivotal role in the synthesis of melatonin and its action in synchronizing pineal events.     

Melatonin increases proliferation of cultured neural stem cells obtained from adult mouse subventricular zone

Abstract: Melatonin, a circadian rhythm–promoting molecule secreted mainly by the pineal gland, has a variety of biological functions and neuroprotective effects including control of sleep–wake cycle, seasonal reproduction, and body temperature as well as preventing neuronal cell death induced by neurotoxic substances. Melatonin also modulates neural stem cell (NSC) function including proliferation and differentiation in embryonic brain tissue. However, the involvement of melatonin in adult neurogenesis is still not clear. Here, we report that precursor cells from adult mouse subventricular zone (SVZ) of the lateral ventricle, the main neurogenic area of the adult brain, express melatonin receptors. In addition, precursor cells derived from this area treated with melatonin exhibited increased proliferative activity. However, when cells were treated with luzindole, a competitive inhibitor of melatonin receptors, or pertussis toxin, an uncoupler of Gi from adenylate cyclase, melatonin‐induced proliferation was reduced. Under these conditions, melatonin induced the differentiation of precursor cells to neuronal cells without an upregulation of the number of glia cells. Because stem cell replacement is thought to play an important therapeutic role in neurodegenerative diseases, melatonin might be beneficial for stimulating endogenous neural stem cells.     

Melatonin attenuates methamphetamine‐induced overexpression of pro‐inflammatory cytokines in microglial cell lines

Abstract: Methamphetamine (METH), the most commonly abused drug, has long been known to induce neurotoxicity. METH causes oxidative stress and inflammation, as well as the overproduction of both reactive oxygen species (ROS) and reactive nitrogen species (RNS). The role of METH‐induced brain inflammation remains unclear. Imbroglio activation contributes to the neuronal damage that accompanies injury, disease and inflammation. METH may activate microglia to produce neuroinflammatory molecules. In highly aggressively proliferating immortalized (HAPI) cells, a rat microglial cell line, METH reduced cell viability in a concentration‐ and time‐dependent manner and initiated the expression of interleukin 1β (IL‐1β), interleukin 6 (IL‐6) and tumor necrosis factor α. METH also induced the production of both ROS and RNS in microglial cells. Pretreatment with melatonin, a major secretory product of the pineal gland, abolished METH‐induced toxicity, suppressed ROS and RNS formation and also had an inhibitory effect on cytotoxic factor gene expression. The expression of cytotoxic factors produced by microglia may contribute to central nervous system degeneration in amphetamine abusers. Melatonin attenuates METH toxicity and inhibits the expression of cytotoxic factor genes associated with ROS and RNS neutralization in HAPI microglia. Thus, melatonin might be one of the neuroprotective agents induced by METH toxicity and/or other immunogens.     

Opioidergic innervation of the tree shrew pineal gland: An immunohistochemical study

Abstract: The tree shrew ( Tupaia glis ) has been described as a missing link relating primate to insectivore stock. The pineal gland of the tree shrew consists of a superficial pineal and a deep pineal, which are connected by long and slender pineal stalk. A monoclonal antibody against leu-enkephalin was used in an immunohistochemical investigation of the tree shrew pineal gland. A moderate innervation of leu-enkephalin immunoreactive nerve fibers has been demonstrated in both superficial and deep pineal gland of the tree shrew. The density of the nerve fibers was slightly higher in the superficial pineal than that of the deep one. The number of immunoreactive nerve fibers were observed in the capsule of the pineal gland from where they entered the pineal parenchyma. Only a few immunoreactive fibers were found in the habenular area and the area rostra1 to the pineal recess, connecting the habenula and the deep pineal. Furthermore, some positive fibers were located in the pineal stalk. There was no evidence of leu-enkephalin immunoreactive intrapineal cells as seen in the other species of mammal. Therefore, the interspecies variation of opioidergic innervation among the mammals may exist. The lack of intrapineal perikarya is interpreted to indicate that the sources of leu-enkephalin nerve fibers were outside the gland. The anatomical location of the leu-enkephalin immunoreactive nerve fibers in the tree shrew pineal gland supports to both central and peripheral pinealopetal pathways in this species.     

Plaque and saliva fluoride levels after placement of fluoride releasing pit and fissure sealants

PURPOSE: The objectives of this study were to investigate the fluoride levels in plaque and saliva before and after applying fluoride-containing pit and fissure sealants, and compare the fluoride release of 2 types of sealants at the different time intervals. METHODS: Eighteen children ages 6 to 9 years were randomly divided into 2 groups: Group 1--sealant containing fluorosilicate glass (Helioseal-F); and group 2--sealant containing methacryloyl fluoride-methyl methacrylate copolymer (Teethmate-F). Saliva and plaque samples were collected before and after the sealants were placed on their 4 first permanent molars. Fluoride levels were determined using the microdiffusion method. Fluoride concentrations before and after placing the sealants were analyzed by paired t test, and the fluoride concentrations between the 2 sealants were compared by t test, with the level of significance at 0.05. RESULTS: There was no significant difference between salivary fluoride levels before and after sealant placement application in both groups. The plaque fluoride level of Helioseal-F group at 24 hours was significantly higher than the baseline level (P = .03), and was not different afterwards. The plaque fluoride levels after sealant with Teethmate-F were not significantly different when compared to the baseline. However, there were no significant differences between salivary and plaque fluoride levels of the 2 groups at different time intervals. CONCLUSIONS: The groups sealed with sealant containing fluorosilicate glass showed significant increase of plaque fluoride level only at 24 hours after sealant placement.     

The neuroprotective effect of melatonin against the induction of c-Jun phosphorylation by 6-hydroxydopamine on SK-N-SH cells

Melatonin is synthesized mainly in pineal gland. It has been suggested that melatonin has proven antioxidant effects and protective effects against neuronal cell degeneration. There are several studies indicating that c-Jun-N-terminal kinase pathways might be involved in neuronal cell death. In this study, the effects of melatonin on 6-hydroxydopamine (6-OHDA)-treated cultured SK-N-SH cells were investigated. The results showed that 6-OHDA significantly decreased cell viability as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay, and melatonin was able to reverse the toxic effects of 6-OHDA on cell viability. In addition, induction of c-Jun phosphorylation by 6-OHDA was diminished by melatonin. These results demonstrate some protective properties of melatonin against neuronal cell degeneration and its action on the inhibition of c-Jun-N terminal kinase signaling cascade.