Rola szyszynki w rozwoju i dojrzewaniu gonad karpia (Cyprinus carpio L.)
AbstractA total of 646 fishes (from one- to six-year-old) were used. Experiments were conducted in different periods of the year using artificial light and variable water temperature corresponding with natural conditions. Part of fish were pinealectomized and on the rest a sham operation was performed. In order to determine the blood levels of estradiol and gonadotropin and some steroid hormones in culture medium after 24 h incubation (in vitro) of oocyte samples with various concentrations of melatonin, routine radioimmunoassay methods were used. The rate of catecholamine metabolism in two aminergic nuclei in the hypothalamus was evaluated using a Falck-Hillarp's histological-fluorescence method. For determining maturation stages of oocytes, ovarian fragments were taken using biopsy. Studies revealed that in immature carp the absence of the pineal glad had no effect on differentiation, and development of gonads. During the process of reaching sexual maturation, pinealectomy causes a slowing down of the last stage of oacyte maturation and inhibits a break-down of the anatomical structure of the germinal vesicle (01/13D). In this time a significant decrease in blood estradiol level was observed. These results have shown that the pineal gland in the period of "long day light" (L:0-16:8), which coincides with the breeding season in carp, can synchronize with the last stage of oocyte maturation and stimulate vitellogenesis in the postovulatory period. In vitro incubation has shown that melatonin had no effect on the carp oocytes maturation. A subsequent conclusion can be drawn that melatonin does not affect directly the ofacyte but rather at a hypothalamus-hypophysis level where it can block a dopamine release (hypothalamic factor blocking GnRB release) and in this way stimulate the blood gonadotropin level. It seems that the pineal gland can constitute an additional factor stimulating a gonadotropic function of the pituitary during a long day light.
|Other language title versions||Role of pineal gland in development and gonad maturation in common carp|
|Publisher||Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW |
|Publishing place (Publisher address)||Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)|
|Publication size in sheets||4.7|
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