Histology and histopathology Vol. 7, nº 4 (1992)

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Circadian and seasonal cortico-medullary variations in pinealocyte nuclear size. A comparative statistical analysis
(Murcia : F. Hernández, 1992) Cimas García, C.; Martínez Soriano, F.; Ruíz Torner, A.
Circadian and seasonal variations were observed in the karyometric index of pinealocytes in the cortical and medullary regions of the dista1 pineal body. The study involved 70 Wistar rats over a 24-hour interval(0:6, 10:00, 14:00, 18:00, 22:00,02:00,06:00 h) during two natural photoluminous periods, i.e. late summer (Long photoperiod) and Winter (Short photoperiod). The results show a difference between the high and low points of both photoperiods. Corticomedullary differences are found at different times of day during long photoperiod (0:6; 10:OO; 14:00 and 18:OO h.) and short photoperiod (14:OO; 22:OO and 02:OO h.). The varianza annalysse between nuclear volume and pointtime and between nuclear volume, point-time and location are significative. A high correlation between circadian rhythms and volumetric variations in both layers and photoperiod are found. The results also show significant differences in cortico-medullary karyometric indices between both seasons as well as between the diurna1 and nocturna1 hours of both photoperiods. It is suggested that the pineal body of the rat is influenced by circadian and seasonal photoperiod and may have groups of cells with different functional characteristics, depending on their location within the gland