Browsing by Subject "Synaptic bodies"

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    Circadian and seasonal changes of synaptic bodies in different parts of the rabbit pineal gland
    (Murcia : F. Hernández, 1999) Martínez Soriano, F.; Hernandez-Gil de Tejadal, T.; Lopez Bigorra, M.; Ballester Carmona, S.; Vollrath, L.
    In the mammalian pineal gland, synaptic bodies (SBs) are poorly understood organelles. Previous studies in rabbits have shown that the organelles are rather heterogeneous in shape, are few in number during the day and increase in number at night. No studies are currently available on seasonal changes in this species and it is unknown whether the biological rhythms are identical in the proximal, intermediate and distal parts of the elongated pineal. To this end, a study was made of 84 rabbits kept under natural lighting conditions to examine numerical variations of the different types of SBs in the proximal, intermediate and distal regions of pineal glands procured at different timepoints of a 24- hour cycle and in each of the four annual seasons. In the present study, rod-like, sphere-like, ovoid, rectangular and triangular SB profiles were distinguished; the first two types being the most abundant. In addition to the well-known circadian changes, with low numbers of SB profiles during the day and high numbers at night, we found pronounced season-related differences as well as differences related to pineal regions. In autumn and winter, nighttime SR profile numbers were significantly higher than in spring and summer. With respect to regional differences it was found that the amplitude of the circadian rhythm increased in a proximo-distal direction in the gland. In autumn the strongly enhanced nocturnal increase was restricted to the distal region of the gland, whereas in winter it was seen in both the distal and the intermediate regions. The regional differences are probably related to the fact that the postganglionic sympathetic fibres, which regulate pineal function, enter the gland distally and proceed rostrally to the proximal region. Taken together, the results show that day- and nightlength are structurally coded in the pineal gland by means of SB numbers. Provided the SBs of the mammalian pineal gland are involved in synaptic processes, the results suggest that synaptic processes are enhanced at night as well as in autumn and winter.
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    Influence of light-dark, seasonal and lunar cycles on serum melatonin levels and synaptic bodies number of the pineal gland of the rat
    (Murcia : F. Hernández, 2002) Martínez Soriano, F.; Ruíz Torner, A.; Armañanzas, E.; Valverde-Navarro, A.A.
    Synaptic bodies (SB) are ultrastructural o rganelles observed in the pinealocytes of mammals. According to its shape, they have been classified into synaptic ribbons (SR), synaptic spherules (SS), and intermediate synaptic bodies (ISB). They have been related to the melatonin regulation and production mechanisms of the pineal gland. Circadian and circannual fluctuations of both melatonin and SB have been reported. The possibility that other external factors, apart from light-dark or seasonal cycles, might influence pineal function has been suggested. We studied the evolution of the number of SB and serum melatonin levels not only during light-dark and seasonal phases but also during lunar cycles. Forty male wistar rats were used. Experiment was first carried out in winter and repeated identically in spring. Each season, one group of animals was killed during the new-moon days and a second group during the full-moon days: half of both groups in the photophase and the other half in the scotophase. The number of SB was measured at electron microscopic level whereas serum melatonin levels were determined by radioimmunoassay techniques. Main results showed that SR number and serum melatonin levels were higher during scotophases, winter and fullmoon days. The SS only showed a light predominance during winter, whereas predominance of the ISB was found only during the scotophases. These results support the influence of the photophasic factors on the SR and ISB variations. In the case of the SS the influence of the lunar cycles is always dependent on the other factors. F i n a l l y, the serum level of melatonin is clearly influenced by the photophasic rhythms and the seasonal periods but not by the lunar cycles.