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1

mRNA expression and immunocytochemical localization of leptin receptor in the oviduct of the laying hen (Gallus domesticus)

100%
Grzegorzewska A., Paczoska-Eliasiewicz H. E., Rzasa J.
Folia Biologica
|
2008
|
vol. 56
|
issue 3-4
179-185
EN
The role of leptin in female reproduction is fairly well established in mammals, whereas reports concerning leptin action in birds are scarce. The aim of the present study was to detect leptin receptor (LEP-R) mRNA and to localize the leptin receptor protein in the oviduct of laying hens 2h after ovulation by the RT-PCR method and immunocytochemical staining. The RT-PCR reaction demonstrated expression of the long form of leptin receptor mRNA in all examined oviductal parts (infundibulum,magnum, isthmus and shell gland) and theweakest level was found in the isthmus. The expression of the short isoform was lower than the long formin all examined tissue samples and no differences between oviductal parts were observed. Immunostaining specific for leptin receptor was found in the walls of all examined oviductal parts. The intensity of the immunopositive reaction was the strongest in the epithelium of all examined parts of the oviduct and in the endothelium and muscles of blood vessels. The weakest immunopositive reaction was observed in tubular glands, the connective tissue layer and in circular and longitudinal muscles. The results obtained in this experiment suggest that the oviductmay be a target tissue for leptin,where this polypeptide hormonmay participate in egg formation and/or its transport through the oviduct of the domestic hen.
2

Effect of 9-cis retinoic acid (RA) on sex hormone secretion and RA receptor expression in chicken ovarian follicles

88%
Pawlowska K., Sechman A., Suchanek I., Grzegorzewska A., Rzasa J.
Folia Biologica
|
2008
|
vol. 56
|
issue 1-2
65-72
EN
Several lines of evidence indicate that retinoids, derivates of vitamin A, affect reproductive function in birds, however, the mechanism of their action in the ovary is still unknown. Therefore, the present study was designed (i) to show whether in the domestic hen 9-cis retinoic acid (9-cis RA), one of the retinoids, influences steroid secretion in vitro by white and yellow chicken ovarian follicles, and (ii) to detect expression of retinoic acid RXR receptor mRNA in these follicles. The white follicles (small: 1-4 mm, medium: 4-6 mm and large 6-8 mm in diameter) and the three largest yellow preovulatory follicles (F3-F1; 25-37 mm) were isolated from the ovary 3 h before ovulation. The granulosa layer was separated from the theca layer in the preovulatory follicles, which were subsequently divided into 4 equal pieces. The isolated whole white follicles or parts of the granulosa or theca layers were incubated for 24 h at 38oC in Eagle's medium in the following 4 groups: control, ovine LH (oLH; 10 ng/ml), 9-cis RA (100 ng/ml) and 9-cis RA + oLH. After incubation, the medium was collected for estradiol (E2) and progesterone (P4) determination while tissues were saved for protein assay. It was found that 9-cis RA affects steroid secretion from chicken ovarian follicles. It decreased E2 secretion from white follicles and from the theca layer of the two largest (F2 and F1) preovulatory follicles. 9-cis RA had no effect on oLH-stimulated E2 secretion by the white follicles and yellow F2 and F1 follicles, but it diminished E2 secretion by F3 follicles. As regards P4, the effect of 9-cis RA was opposite; it increased P4 secretion from the granulosa layer of all preovulatory follicles. 9-cis RA did not change oLH-stimulated P4 secretion by granulosa layers of F3 and F2 follicles, however, it inhibited oLH-enhanced P4 secretion from the F1 granulosa layer. In a separate experiment, the presence of mRNA encoding RXR was found in the stroma and all follicles of the chicken ovary by means of the RT-PCR technique. The results indicate that retinoids, acting by specific nuclear receptors, are modulators of follicular steroidogenesis in the chicken ovary.
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