Browsing by Subject "Gut endocrine cells"

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    Origin and differentiation of gut endocrine cells
    (Murcia : F. Hernández, 1993) Rawdon, B.B.; Andrew, A.
    The epithelium of the digestive tract contains endocrine cells which produce serotonin and an array of regulatory peptides. It is now irrefutably established that gut endocrine cells are not of neural crest nor even of neurectodermal origin. Furthermore, the proposal that they might originate from neuroendocrine-programmed epiblast has been retused by recent evidence that they share the endodermal stem cell pool with the other epithelia1 cells of the gut. Based on the available evidence, a working hypothesis for the differentiation of gut endocrine cells has been developed. It is proposed that initially the developing gut acquires an underlying tendency to differentiate into intestine: the endoderm has the potential to form a wide range of endocrine cell types. A little later, some influence operative over the length of the presumptive gut imposes a regionally specific pattern on the tract. This process concerns morphogenesis and pre-selection of the range and proportions of the endocrine cell types. Thereafter, the mesenchyme feeds to the endoderm confirmatory signals reinforcing this pre-selected regional pattern of endocrine cells. Once the different endocrine cell types have started to differentiate, their maturation is effected by circulating factors which include glucocorticoid hormone: this process is mediated by the mesenchyme. Other factors concerned at various stages of gut endocrine cell differentiation could be other hormones, growth factors and or components of extracellular matrix: such factors are still untested in this context.
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    The distribution and ontogeny of gastrin/CCK-, somatostatin- and neurotensin-immunoreactive cells in the gastrointestinal tract of the chicken
    (Murcia : F. Hernández, 1989) Alison, B. G.
    The distribution and time of appearance of cells with gastrin1CCK-, neurotensin- and somatostatinlike immunoreactivity were studied in samples from eight regions of the gastrointestinal tract of chick embryos from 11 days of incubation to hatching. No immunoreactive cells were found in any region at 11 days of incubation. Somatostatin- and neurotensinimmunoreactive cells appeared for the first time in the proventriculus, pyloric region and duodenum at 12 days of incubation with cells immunoreactive for neurotensin occurring in the rectum at the same stage. GastrinICCKimmunoreactive cells were detected in the small intestine first at 14 days and in the pyloric region two days later. Cells immunoreactive for somatostatin and neurotensin appeared in the upper and lower ileum at 14 days of incubation for the first time; neurotensin-immunoreactive cells, present in the caecum at 14 and 16 days, were rare. Cells of al1 three types were plentiful in the pyloric region by 17E days of incubation. No immunoreactive cells were detected in the gizzard at any stage studied. Endocrine cells were present in the relatively undifferentiated surface epithelium which occurs throughout the gastrointestinal tract of chick embryos at 12 days of incubation. Thereafter cells of al1 three types were detected in the glandular epithelium at or very soon after morphogenesis and differentiation of the latter had occurred.