Study on molecular mechanism of melanocyte-stimulating hormone system in the chicken

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1. The presence and possible physiological roles of a-MSH in the peripheral tissues of birds have not established. By a combination of RT-PCR, immunocytochemitry and in situ hybridization, we identified the expression of a-MSH in the eye, which is regulated temporally and spatially in the developing chicken. The data clearly indicated that the retinal pigment epithelial cells (RPE cells) and the cone cells are intraocular sources of a-MSH in the embryonic and postnatal life of the chicken, respectively. Embryonic expression of a-MSH in the RPE cells implies a possible role for the peptide in ocular development This is the first report demonstrating the expression of a-MSH in peripheral tissues in birds, and supports our hypothesis that avian a-MSH is a paracrine/autocrine hormone.2. Growth hormone (GH) is considered to play a role in the phatogenesis of diabetic retinopathy. RT-PCR and 5'RACE analysis identified a novel GH isoform expressed in the developing chicken eye. Immunocytochemistry revealed that the binding of the novel GH isoform, named as s-cGH, to GH receptors in the RPE cells is temporally regulated and correlates well with the production of a-MSH in the RPE cells during embryonic development, implying a possible involvement of s-CGH in the regulation of ocular development.3. The neural mechanisms involved in the compensatory hyperphagia exhibited by many vertebrate species after a fast are not fully understood but, in mammals, appear to involve neutritionally-sensitive neurons that co-express neuropeptide Y (NPY) and agouti-related protein (AGRP) in the infundibular hypothalamus. We investigated whether these neurons have been evolutionarily conserved in a non-mammalian vertebrate, the Japanese quail. Double-label in situ hybridization revealed that majority of NPY neurons in the infundibular nucleus co-express AGRP mRNA, indicating that this cell type has been neuroanatomically and functionally conserved during vertebrate evolution. .