[Disperse endocrine system and APUD concept].

This review describes the problems of disperse endocrine system and APUD-system morphology, summarizes some debatable issues of single endocrine cell biology. The data presented refer to the history of both systems discovery, morphological methods of their study, developmental sources, their structural organization and physiological roles of their cells. The significance of single endocrine cells in the regulation of the organism functions is discussed.

[The ultrastructure of the epithelial endocrinocytes of the appendiceal mucosa in the human fetus]. / Ul'trastruktura éndokrinotsitov épiteliia slizistoi obolochki cherveobraznogo otrostka ploda cheloveka.

An electron microscope study of the epithelium of vermiform processes of 11-26 week old human fetuses showed seven types of endocrinocytes differing in ultrastructure and dimensions of secretory granules. In addition to the six known types of endocrinocytes (EC, D, D1, I, L and P), endocrinocytes of a 7th type were discovered which are beyond the International classification of endocrinocytes of the gastroenteropancreatic system. The overwhelming majority of endocrinocytes of the vermiform process epithelium form EC-cells. Besides, cells of a "mixed" type, both exo-endocrine and endo-endocrine cells, were revealed.

[APUD and mast cells of the gastrointestinal system: immunohistochemical and ultrastructural identification]. / Apudotsity i tuchnye kletki zheludochno-kishechnogo trakta: immunogistokhimicheskaia i ul'trastrukturnaia identifikatsiia.

A rationale for sequential immunohistochemical studies of the endocrine function of APUD cells is described, as exemplified by a study of serotonin-containing cells in rat small intestine, involving preparation of paraffin and semithin sections of epoxide resin-embedded tissue, followed by electron-microscopic examination of cells detected by the immunoperoxidase technique. With the approach described, it has been shown that a positive immunohistochemical reaction to antiserotonin antiserum is given, along with EC cells, by those mast cells disposed in groups near the EC cells as well as among connective-tissue cells of villi under the basement membrane. It is suggested that by collecting and accumulating the serotonin synthesized by specialized EC cells, mast cells transport it to sites of utilization as required by the specific arrangement.

The endocrine cells of the digestive tract. General concepts and historic perspective.

The chromaffin cells of the digestive mucosa were discovered by Heidenhain in 1870, long before the hormone concept was formulated. Following the discovery of the first hormone, secretin, by Bayliss and Starling in 1902, the study of the cells producing such messengers acquired new impetus. After Masson, in 1914, showed that the digestive chromaffin cells were argentaffin and suggested their endocrine nature, a series of technological advances led to the gradual characterization of diverse cell types, their classification, and the discovery of their function. Histochemistry, including silver impregnations, fluorescence microscopy, and aniline stains, exposed the complexity of the digestive endocrine cells. Electron microscopy provided structural markers for their characterization and the basis for the formulation of the first universally accepted classifications. Light- and electron-microscopic immunocytochemistry contributed to the understanding of the function of many of these cells, thus opening the way for modern classifications. Many unsolved problems still remain. These include the existence of cells without defined function, of chemical messengers without known cell of origin, and the presence of multiple messengers in some cell types. Answers are expected to emerge from further application of immunocytochemistry and from the introduction of modern approaches, such as in-situ hybridization histochemistry.

Human prostatic endocrine-paracrine (APUD) cells. Distributional analysis with a comparison of serotonin and neuron-specific enolase immunoreactivity and silver stains.

Prostatic endocrine-paracrine (PEP) cells from the prostates of 25 radical cystectomy specimens were studied using serotonin and neuron-specific enolase immunocytochemistry and argyrophil and argentaffin silver stains. Three populations of PEP cells were identified as follows: (1) serotonin-positive only, (2) serotonin-positive and argyrophil-positive (the largest population), and (3) serotonin-positive, argyrophil-positive, and argentaffin-positive. Neuron-specific enolase immunoreactivity correlated closely with serotonin immunoreactivity. The entire PEP cell cytoplasm was serotonin and neuron-specific enolase immunoreactive, while the silver stains only stained the granulated cytoplasm. The PEP cells were present in all areas of all prostates with a surprisingly large number in the large periurethral ducts with somewhat fewer PEP cells in the prostatic urethra and smaller ducts and ductules. The peripheral acini generally contained the smallest number of PEP cells. Prostatic endocrine-paracrine cells were of the open (luminal extension), closed, and dendritic types.

[Identification of endocrine cells in the gastrointestinal tract]. / Ob identifikatsii éndokrinnykh kletok zheludochno-kishechnogo trakta.

The gastric and duodenal endocrine cells (apudocytes) of children and immature rats were studied by electron microscopy. It is shown that every cell type has its own morphological peculiarities of secretory granules formation, maturation and disintegration. This feature together with the size and morphology of mature granules is recommended to be used as a classification criterion for the identification of apudocyte types.