The Study On The Distribution Of Somatostatin In The Gastrointestinal Tract And Thymus Of The African Ostrich Chick

The climatic environment and food source hase changed after the ostrich has introduced in our country from abroad, which lead to declined immunity and decreased porfermance to the ostrich. Furthermore, the ostrich, the biggest and unflyable bird living in the world, has longer brood time. During the brood time, the growth anddevelopment of the ostrich is slow, whereas its gastrointestinal disease is serious. So, in order to improve the immunity and decrease gastrointestinal disease rate for ostrich, basic research on morphological development and functional regulation should be investigated in indetail for the ostrich. Somatostatin (SS), a neuropeptide with an inhibitory role on the release of growth hormone, was first isolated in ovine hypothalamic extracts by Brazeau ea al in1973. Studies have demonstrated that in addition to the hypothalamus, SS-immunoreactive (SS-IR) cells also are distributed across other brain regions and in many peripheral organs such as the gastrointestinal tract (GIT), the pancreas and the thymus. SS is involved in a variety of activities including the regulation of neuronal function, hormonal secretion, cardiovascular function, as well as the gastrointestinal function and immune response. The anatomical and histological structure of the GIT and the thymus of the ostrich chicks has been studied and described. However, there are no studies so far on distriubtion of SS in the GIT and the thymus of this bird. The aim of the present study was to investigate the distribution, expression and age-related chanes of SS in the GIT and the thymus of the African ostrich chicks, by immunohistochemistry and RT-PCR, for a better understanding of the physiological role of SS in the GIT tract and the thymus of the ostrich. Moreover, comparative study of distribution of SS in the different animals would help clarify its evolutionary complexity. The works and the results of this study are as follows:1The distribution and expression of SS in the GIT of the African ostrich chicksThe distribution and morphological features of SS-IR cells and expression of SS mRNA were investigated in the GIT of the African ostrich chicks on day90by using immunohistochemical techniques and RT-PCR. Immunohistochemical results show that SST-IR cells were distributed in the proventriculus, duodenum, jejunum and ileum. However, no immunoreactivity was observed in the gizzard, cecum, colon and rectum. In the proventriculus, great numbers of the SS-IR cells were clustered in the base of glandular lobule. These cells had a small round or oval shape. In the small intestinal, SST-IR cells were present in the mucosal layer of whole small intestine of the ostrichs.The number of SST-IR cells were moderate in the duodenal portion but then became rare in the jejunal and ileal portions.SST-IR cells were present in the crypts and villi, which often had round and spherical shapes(closed-type cells). Spindle and pyriform shaped cells, with an apical cytoplasmic process, in contact with the lumen, were also found. The RT-PCR results confirmed the expression of SS mRNA in the proventriculus, duodenum, jejunum, ileum and colon, but no expression of that in the gizzard, cecum and rectum. There are both similarity and difference between our results on the distribution of SS-IR cells in the GIT of the ostrich and study on other animal, suggesting^the distribution of SS-IR cells in the GIT are both conservative and diverse.2The age-related changes of SS-IR cells in the proventriculur and small intestinal of the African ostrich chicksThe development changes of the SS-IR cells in the proventriculur and the small intestinal were detected by immunohistochemical SABC and Image analysis in the African ostrich chicks aged on1day,45days, and90days, and compared with that in African ostrich chicks aged on1year. The results show:The distribution density of SS-IR cells increased significantly on day1, compared with that on day45(P<0.05) in the proventriculus, peaked on day45. However, it decreased significantly on day90, which show no significant difference between these birds aged day90and year1.The distribution density of SS-IR cells increased significantly on day1to day90(P<0.05) in the duodenum, and peaked on day90, which show no significant difference between these birds aged day90and year1. In contrast, it decreased gradually from day1to day90(P <0.05), which show no significant difference between this birds aged day90and year1. There are the regular changes of the SS-IR cells dencity in the proventriculus and small intestine of the ostrich during brood time. SS may be involved in the development and function of the GIT of the ostrich chicks. 3The distribution and expression of SS in the thymus of the African ostrich chicksThe distribution and morphological features of SS-IR cells and expression of SS mRNA were investigated in the GIT of the African ostrich chicks on day90by using immunohistochemical techniques and RT-PCR. Immunohistochemical results show that immunoreative cells were sparely distributed in both the cortical and medullary regions of the thymus, but mainly in the corticomedullary junction. The SS of these cells had a small round or oval shape Spindle and pyriform shaped cells with multicellular processes were also found. Furthermore, The RT-PCR results confirmed the expression of SS mRNA in the ostrich thymus. These findings suggest that SS may play a role in T-cell development via autocrine and paracrine pathways4The age-related changes of SS-IR cells in the thymus of the African ostrich chicksThe development changes of the SS-IR cells in the thymus intestinal were detected by immunohistochemical SABC and Image analysis in the African ostrich chicks aged on1day,45days, and90days, and compared with that in African ostrich chicks aged on1year. The results show. The distribution density of SS-IR cells increased significantly on day1to day45(P<0.05); There was no significant difference after day45. These results suggest SS may play a role in T-cell development during brood time.5Molecular cloning and sequence analysis of cDNA encoding SS from African ostrichThe cDNA encoding SS from African ostrich were firstly amplified from the total RNA of the proventriculur by RT-PCR. The cDNA were cloned, Identified, sequenced and analyzed. The results show as fellow:the nucleotide sequence was348bases. The identities between the sequence of ostrich with that of chicks, zebra finch, pig, dog, cattle, goat, human, Rhesus monkey, crab-eating macaque, mouse, rat, western clawed frog and Chinese sturgeon were among95.1%-72.2%. The translation of the nucleotide sequences into the amino acids was performed using the DNASTAR software. The deduced encoded protein was116amino acids residue protein precursors in length. Compared with the amino acid sequence of other species, the mature SS-14peptide sequence of the ostrich was idenctical with the homologue of other species. SS-28peptide sequence of the ostrich was identical with the homologue of the chicks and had only a residue discrepancy at the9th site of the N-terminal with the homologue of the rodents and the Mammali. The relationship between the African ostrich SS and chicks SS gene was close in the phylogenetic tree analysis by DNASTAR software. These fingings suggest the sequence of aminao acid and nucleotide of SS is highly-conserved in the evolution of life.