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      Probable effect of photoperiod on seasonal variation in the nuclear volume of the adrenal cortex of viscacha (Lagostomus maximus maximus)

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          Abstract

          The neuroendocrine system regulates several organic functions such as reproduction, metabolism and adaptation to the environment. This system shows seasonal changes linked to the environment. The experimental model used in the present study was Lagostomus maximus maximus (viscacha). The reproduction of males of this species is photoperiod dependent. Twenty-four adult male viscachas were captured in their habitat at different times during one year. The adrenal glands were processed for light microscopy. Serial cuts were stained with hematoxylin-eosin for the morphometric study, and 100 nuclei of each zone of the adrenal cortex were counted per animal. Data were analyzed statistically by ANOVA and the Tukey test. The cells of the glomerulosa zone are arranged in a tube-shaped structure. The fasciculata zone has large cells with central nuclei and clearly visible nucleoli and with a vacuolar cytoplasm. In the reticularis zone there are two of types of cells, one with a nucleus of fine chromatin and a clearly visible nucleolus and the other with nuclear pycnosis. Morphometric analysis showed maximum nuclear volumes during the February-March period with values of 133 ± 7.3 µm3 for the glomerulosa, 286.4 ± 14.72 µm3 for the fasciculata, and 126.3 ± 9.49 µm3 for the reticularis. Minimum nuclear volumes were observed in August with values of 88.24 ± 9.9 µm3 for the glomerulosa, 163.7 ± 7.78 µm3 for the fasciculata and 64.58 ± 4.53 µm3 for the reticularis. The short winter photoperiod to which viscacha is subjected could inhibit the adrenal cortex through a melatonin increase which reduces the nuclear volume as well as the cellular activity.

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          Most cited references 36

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          Melatonin: a coordinating signal for mammalian reproduction?

          There is a daily rhythm in the production of the pineal hormone melatonin in all mammalian species. Production is stimulated by darkness and inhibited by light. This provides a signal reflecting the changing environmental lighting cycle. In seasonally breeding mammals that use changes in the photoperiod to time their reproductive cycles, temporal signals to the reproductive system are controlled by the daily rhythm in melatonin production.
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            Desert Ecosystems: Environment and Producers

             I Noy-Meir (1973)
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              MELATONIN

               J Arendt (1988)
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                Author and article information

                Journal
                bjmbr
                Brazilian Journal of Medical and Biological Research
                Braz J Med Biol Res
                Associação Brasileira de Divulgação Científica (Ribeirão Preto, SP, Brazil )
                0100-879X
                1414-431X
                September 1999
                : 32
                : 9
                : 1115-1120
                Affiliations
                Mendoza orgnameUniversidad Nacional de Cuyo orgdiv1 Cátedra de Histología y Embriología Argentina
                San Luis orgnameUniversidad Nacional de San Luis orgdiv1 Cátedra de Histología y Embriología, Facultad de Química, Bioquímica y Farmacia Argentina
                Article
                S0100-879X1999000900010 S0100-879X(99)03200910
                10.1590/S0100-879X1999000900010

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 26, Pages: 6
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                Categories
                Neurosciences and behavior

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