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Biomedical subjects

A Andrew

Publications and source records attributed to A Andrew.

53 records · Page 3Linked to original sources
PubMed1976

Pancreatic APUD cells in older chick embryos, with special reference to their identity.

Pancreatic APUD cells showing formaldehyde-induced fluorescence in Black Australorp chick embryos of nine to eighteen days of incubation, proved, on subsequent staining and silver impregnation, to be A, B, D and, from sixteen days, enterochromaffin (EC) cells. EC and D cells were scattered in the exocrine parenchyma, the latter cells increasing with time. Some group of B cells were associated with large A islets from the ninth day of incubation onwards. The composition of A islets (A and some D cells) and B islets (B and some D cells) and the distribution attained (A islets in the splenic and third lobes; B islets in all lobes), accords with the situation reported for adults.

Age Factors↗
PubMed1976

Intestinal endocrine cells of chicks around the time of hatching.

The duodenum of 16-day Black Australorp chick embryos, and the duodenum, ileum, large intestine and caeca of 18-day embryos and of chicks within 30 h of hatching, have been studied by electron microscopy. Cells were found with secretory granules resembling those in mammalian EC, S, A-like, EG and D cells (terminology of Solcia et al., 1973), and were on this basis tentatively identified accordingly. The distribution and frequency of the chick cells in different parts of the tract correspond well to the situation in mammals.

Animals↗
PubMed1976

Endocrine cells of the stomach of chicks around the time of hatching.

The proventriculus, gizzard and pyloric antrum (region between the gizzard and the duodenum) of 18-day Black Australorp chick embryos and of chicks within 30 h of hatching have been studied by electron microscopy. D and EC cells, and putative G, D1 and A-like cells were identified (terminology of Solcia et al., 1973) but no ECL cells. No endocrine cells of any kind were revealed in the gizzard.

Animals↗
PubMed1976

APUD cells, apudomas and the neural crest.

The most characteristic feature of the APUD cell series is the ability to take up and decarboxylate amine precursors. Other features, regarded as characteristic by Pearse, are the secretion of polypeptide hormones and their origin from the neural crest. An increasing number of APUD cells is being shown to elaborate polypeptide hormones. It is acknowledged that some members are derived from the neural crest, but there is a good reason to believe that others are not, and no good reason to believe that yet others are so derived. It is therefore suggested that the common factor sought in the genesis of the APUD cell, and perhaps other tumours, may be the biochemical, rather than the embryological, relationship of the progenitor cell types.

Animals↗
PubMed1976

An experimental investigation into the possible neural crest origin of pancreatic APUD (islet) cells.

It has recently been contended that pancreatic APUD cells are neural crest derivatives. In an experimental investigation, isotopic grafts of neural tube containing neural crest cells were transplanted from chick and quail embryos labelled with tritiated thymidine, and from unlabelled quail embryos, to host chick embryos at the same stage of development. Transplantations were performed at various levels between somites 5 and 24 in embryos at 6- to 24-somite stages. In operated embryos at 3 3/4 days of incubation, the pancreatic APUD cells were not labelled; nor did their nuclei show quail features. Migration of cells from the graft was evidenced by the presence of quail nuclei and/or radioactive label in autoradiographs, in spinal and sympathetic ganglia in the operated region. It is concluded that the pancreatic APUD cells of the 3 3/4-day-old chick embryo are not derived from the trunk neural crest up the level of somite 24. It is unlikely that more caudal levels contribute, because APUD cells are already concentrated in the dorsal pancreatic bud region at the 24-somite stage, by which time no migration of crest cells has occurred caudal to somite 24. This conclusion probably concerns A, B and D pancreatic endocrine cells.

Animals↗
PubMedDate not supplied

Development of embryonic chick insulin cells in culture: beneficial effects of serum-free medium, raised nutrients, and biomatrix.

A previous finding that insulin cells do not survive or differentiate in explants of embryonic avian pancreas cultured in collagen gel with a serum-containing medium has provided a model system for identification of conditions favorable for development of these cells. To this end, we here modify the substrate and the medium. The epithelial component of dorsal pancreatic buds of 5-d chick embryos was cultured for 7 d on Matrigel in serum-containing and in serum-free medium, the latter incorporating insulin, transferrin, and selenium. Endocrine cell types were distinguished by immunocytochemistry; insulin cell counts were expressed as a proportion of insulin plus glucagon cells. With serum-containing medium, Matrigel stimulated a significant increase in this proportion as compared with collagen gel--3.1% as against 0.2%; the serum-free medium further increased this proportion to 17.3%. Raising the level of essential amino acids approximately fivefold increased the latter figure somewhat (to 18.9%), but it was more than doubled (to 37.4%) by raising the glucose concentration from 10 mM to 20 mM. Raising the levels of amino acids and glucose simultaneously yielded a lesser increase (to 31.8%). Some cultures grown in collagen gel and serum-containing medium for 7 d were transferred to Matrigel and serum-free medium for a further 7 d. Insulin cell development recovered, indicating that progenitor cells had survived and were stimulated to develop by the improved conditions. This study indicates that components of the biomatrix and the medium (in particular, a raised glucose concentration) are important for the survival and differentiation of embryonic insulin cells.

Amino Acids, Essential↗
PubMedDate not supplied

Biologically active gastrin/CCK-related peptides in the stomach of a reptile, Crocodylus niloticus; identified and characterized by immunochemical methods.

We have used immunochemical, chromatographic, and bioassay techniques to characterize peptides related to gastrin and CCK, from the stomach of the reptile Crocodylus niloticus. By immunocytochemistry gastrin/CCK-like peptides were localized in specific mucosal cells of the pylorus and in the duodenum. Boiling water extracts of pyloric antrum cross reacted with four antisera specific for the C-terminal region of gastrin or CCK, but estimates of concentration varied between antisera. Antisera specific for the N-terminus of heptadecapeptide gastrin (G17), intact G17, or the amphibian CCK-like peptide caerulein did not cross react with the crocodile extracts. Gel filtration of the extracts on Sephadex G50 resolved one major peak eluting significantly before G17 or CCK8, suggesting larger molecular size, whereas ion exchange on DE52 cellulose resolved two major immunoreactive peaks, both eluting before G17, indicating that they are less acidic. The more acidic of the two peptides stimulated gastric acid secretion in the rat, but had no CCK-like actions on the rat pancreas. Thus crocodile antrum contains gastrin-like peptides, which are however clearly distinguishable from any of the known mammalian forms of gastrin and CCK.

Alligators and Crocodiles↗