title: Light and electron microscopic examination of pineal gland in rats exposed to constant light and constant darkness.
abstract: OBJECTIVE
  This study was aimed to examine the pineal gland of rats exposed to constant light and darkness at light and electron microscopic level.
  
  
  METHODS
  For this purpose 18 male Wistar rats were used. Animals were divided into three groups. Rats in group I (Control) were kept under 12 hrs light: 12 hrs dark conditions. Rats in group II were exposed to constant darkness, while rats in group III were exposed to constant light for 6 weeks. At the end of the experiment, all animals were killed by decapitation. The pineal glands of rats were removed, then processed for light and electron microscopy.
  
  
  RESULTS
  In our study, extensive number of pinealocytes was observed in the structure of pineal gland of rats exposed to constant darkness and some of the observed pinealocytes were determined to contain double nucleoli. Furthermore, mitochondria and lipid droplets in the cytoplasm of pinealocytes were increased and rough endoplasmic reticulum sacs were enlarged in this group. Whereas, in rats those exposed to the constant light, a decrease in pinealocyte intensity was associated with increase in the connective tissue between parenchymal cells. Additionally, mitochondria and lipid droplets in the cytoplasm of cells were decreased.
  
  
  CONCLUSIONS
  It was observed that the pinealocyte cell activity of rats exposed to constant darkness was increased but decreased in rats exposed to constant light.
authors.affiliation: Department of Anatomy, Faculty of Medicine, Firat University, Elazig, Turkey.
authors.forename: Ilter
authors.initials: I
authors.lastname: Kus
authors.forename: Mustafa
authors.initials: M
authors.lastname: Sarsilmaz
authors.forename: Oguz Aslan
authors.initials: OA
authors.lastname: Ozen
authors.forename: Aslý Ozdem
authors.initials: AO
authors.lastname: Turkoglu
authors.forename: Hidir
authors.initials: H
authors.lastname: Pekmez
authors.forename: Ahmet
authors.initials: A
authors.lastname: Songur
authors.forename: Haluk
authors.initials: H
authors.lastname: Kelestimur
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002940:Circadian Rhythm / Q000528:radiation effects; D003624:Darkness; D008027:Light; D008297:Male; D017440:Photoperiod; D010786:Photoreceptor Cells / Q000528:radiation effects / Q000648:ultrastructure; D010870:Pineal Gland / Q000528:radiation effects* / Q000648:ultrastructure*; D051381:Rats; D017208:Rats, Wistar