title: Quantitative morphology and environmental responses of the pineal gland in the collared lemming (Dicrostonyx groenlandicus).
abstract: Collared lemmings from Churchill, Manitoba, and their descendants were studied in captivity to define neuroendocrine and related histophsiological characteristics and responses, particularly in relation to photic and temperature conditions. Relatively great pineal size (0.1755 +/- 0.0167 mm3, or 3.08 +/- 0.30 = pineal volume in mm3 X 10(3)/body weight in gm; N = 16) shown in this arctic rodent is consistent with the suggestion that pineal size and significance may tend to be greater in more northern (higher latitude) species. Total number of nucleated cells per pineal averaged 137,000 +/- 10,500. Pinealocytes (105,000 +/- 8,700/pineal) and other cell types were present in relative numbers typical of mammalian pineal glands, and were not numerically correlated with age, sex, or location or circumstances of birth and early postnatal life. Chronic exposure to warmer (21-27 degrees C) in comparison with colder (-9 to -6 degrees C) environments, whatever the illumination, led to greater pinealocyte activity, as shown especially by nucleolar diameter, throughout most of the nine regions of the organ analyzed cytologically (all regions combined: P less than 0.001). Increased pinealocyte activity in chronic darkness was suggested by similar evidence (P less than 0.01), but in comparison with the thermal effects, was less marked and more variable in different regions of the organ. These and other findings of this study indicate that the Dicrostonyx pineal organ is morphologically unique, relatively large in size, and cytologically responsive to environmental conditions.
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000648:ultrastructure; D004777:Environment; D008029:Lighting; D008350:Manitoba; D010870:Pineal Gland / Q000166:cytology* / Q000648:ultrastructure; D012377:Rodentia / Q000033:anatomy & histology*; D013696:Temperature