C and APUD cells and endocrine tumours. Pearse's laboratory in the years 1965-1969: a personal recollection.

This paper is a personal recollection of the studies, conducted in Prof. Pearse's laboratory in London in the years 1965-1969, which led to the discovery of production of calcitonin by parafollicular C cells and medullary carcinomas of the thyroid. The author's intention is to underline the combination of technical excellence, brilliant intuition, dedication and serendipity which led to a series of major discoveries and, historically, established the pivotal role to be played by immunohistochemistry in endocrine research and diagnosis. The formulation of Pearse's APUD cell theory gave a formal credence to the existence of common endocrine mechanisms, molecular markers and structural features in dispersed cells, all belonging to a diffuse endocrine system. This represented a major breakthrough which primed, in the following years, the studies on polypeptide hormone-producing cells and tumours, thus paving the way to the endocrine histology and pathology as we know, and practice them today.

[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.

Evolution of the diffuse neuroendocrine system--clear cells and cloudy origins.

As early as the 2nd century, Galen proposed that 'vital spirits' in the blood regulated human bodily functions. However, the concept of hormonal activity required a further 18 centuries to develop and relied upon the identification of 'ductless glands', Schwann's cell and the recognition by Bayliss and Starling of chemical messengers. Bernard's introduction of 'internal secretion' and its role in homeostasis laid a physiological basis for the development of endocrinology. Kocher and Addison recognized the consequences of ablation of glands by disease or surgery and identified their necessary role in life. Detailed descriptions of the endocrine cells of the gut and pancreas and their putative function were provided by Heidenhain, Langerhans, Laguesse and Sharpey-Schafer. Despite the dominant 19th century concept of nervism (Pavlov), in 1902, Starling and Bayliss using Hardy's term 'hormonos' described secretin and in so doing, established the gut as an endocrine organ. Thus, nervism was supplanted by hormonal regulation of function and thereafter numerous bioactive gut peptides and amines were identified. At virtually the same time (1892), Ramón y Cajal of Madrid reported the existence of a group of specialized intestinal cells that he referred to as 'interstitial cells'. Cajal postulated that they might function as an interface between the neural system and the smooth muscles of the gut. Some 22 years later, Keith suggested that their function might be analogous to the electroconductive system of the heart and proposed their role as components of an intestinal pacemaker system. This prescient hypothesis was subsequently confirmed in 1982 by Thuneberg and a decade later Maede identified c-Kit as a critical molecular regulator in the development and function of the interstitial cells of Cajal and further confirmed the commonality of neural and endocrine cells. The additional characterization of the endocrine regulatory system of the GI tract was implemented when Feyrter (1938) using Masson's staining techniques, identified 'helle Zellen' within the pancreatic ductal system and the intestinal epithelium and proposed the concept of a diffuse neuroendocrine system. Pearse subsequently grouped the various cells belonging to that system under the rubric of a unifying APUD series. Currently, the gut neuroendocrine system is viewed as a syncytium of neural and endocrine cells sharing a common cell lineage whose phenotypic regulation is as yet unclear. Their key role in the regulation of gastrointestinal function is, however, indubitable.

[Morphofunctional regeneration of epithelial cells in the colon and apudocytes in the pathogenesis and prognosis of the course of non-specific ulcerous colitis].

One hundred twenty patients with nonspecific ulcerative colitis (NUC) were examined. The patients were divided into three groups equal in number according to the severity of the disease. The controls were 24 practically healthy individuals, 64 patients with irritated bowel syndrome (IBS) without pathological changes in the colon mucosa, and 64 IBS patients with atrophic or inflammatory changes in the colon mucosa. The study showed that the development of NUC was associated with an abrupt decrease in the level of proliferation markers (cycline D, and proliferating cell nuclear antigen - PCNA) in the epithelial cells of the sigmoid colon. Their number progressively decreases in more severe cases, while cell apoptosis intensifies. Such changes in cell renewal are closely connected with the functional and structural rebuilding of the diffuse endocrine system, which manifests in an increase of the total number of apudocytes as well as serotonin- and melatonin-producing cells together with a decrease in the number of VIP-producing cells.

Immunohistochemical and electron-microscopic identification of neuroendocrine cells in the stomach of uremic rats.

Many disturbances in electrolyte and hormonal balance in the body induced by functional impairment of renal parenchyma may affect the activity of amine precursor uptake and decarboxylation (APUD) cells, which constitute a very important link in the regulation of homeostasis. The aim of the present study was the morphological, immunohistochemical and ultrastructural estimation of enteroendocrine cells in the stomach of uremic rats. Fragments of gastric pylorus were collected 1, 2 and 4 weeks after nephrectomy. Paraffin embedded sections were stained with H + E and by silver impregnation. For identification of neuroendocrine cells, immunohistochemical reactions were performed using specific antibodies against somatostatin, synaptophysin, neuron-specific enolase and anti-calcitonin gene related peptide. The analysis showed an increased number of APUD cells in the stomach of uremic rats compared to control rats, which may be a morphological expression of their hyperfunction in the functional impairment of renal parenchyma. These results suggest that chronic renal failure can modulate the secretory processes of APUD cells.

Possible mechanisms of panic attack and schizophrenia via APUD system.

Psilocybin poisoning produces biphasic reactions composed of a schizophrenic phase and a panic attack-like phase. There is a time lag of several hours between phases, which may be considered an accumulation time in certain sites between the gut and the brain. So far as 5-hydroxytryptamine (5-HT) congeners are concerned, no sites are to be found except the amine precursor uptake and decarboxylation (APUD) system. It is postulated that argyrophil cells (AC) in the foregut, neuroepithelial bodies (NEB) in the lung, and raphe nuclei (RN) in the brainstem axis are relevant to mental disorders. Schizophrenia might be due to the massive destruction of APUD cells, and the paroxysmal release of 5-HT with peptides and panneuroendocrine markers from NEB might be the cause of panic attack.

[Effect of pineal peptides on neuroendocrine system after pinealectomy]. / Vliianie peptidov pineal'noi zhelezy na neiroéndokrinnye vzaimosviazi posle pinealéktomii.

Removal of the pineal gland leads to structural and functional rearrangement of gastric endocrine cells and thyroid C-cells in albino rats, as was shown by immunohistological methods and morphometry. Injection of pineal peptides epithalone and epithalamine eliminated these changes. Biological activity of epithalone is believed to be higher than that of epithalamine.

[APUD- and RAA- regulatory systems in acute radiation injury]. / APUD- i RAA-sistemy reguliatsii pri ostrom radiatsionnom porazhenii.

An experimental morpho-functional assessment of rat APUD and RAA systems status in acute radiation injury (cerebral form) was performed. The named regulatory systems were found to display an actual momentary post-exposure reaction, followed by subsequent functional changes of a distinct phase character. The latter were shown to determine in many respects the clinical picture and in some cases the outcome of the disease.

[Importance of the morphofunctional status of APUD cells in the prognosis of duodenal ulcer hemorrhage]. / Znachenie morfofunktsional'nogo sostoianiia apudotsitov dlia prognoza krovotecheniia pri iazvennoi bolezni dvenadtsatiperstnoi kishki.

In 24 patients with uncomplicated duodenal ulcer and 40 patients with acute bleeding duodenal ulcer morphofunctional status of the local paraendocrine adjusting system of the duodenal mucous membrane in the periulcer, ulcer and remote zones was studied with histochemical and electron-microscopic techniques. It is established, that ECL- and G-apudocytes hyperplasia and hyperfunction and vice versa D-cells reduction of the number and suppression of the secretory activity are reliable prognostic criteria of duodenal ulcer bleeding.

[The APUD-system function of the intestines and the morphological changes in the internal organs of adult rabbits infected with toxigenic Vibrio cholerae]. / Sostoianie APUD-sistemy kishechnika i morfologicheskie izmeneniia vo vnutrennikh organakh vzroslykh krolikov, zarazhennykh toksigennymi kholernymi vibrionami.

V. cholerae infection with clearly pronounced diarrhea was reproduced in adult rabbits with the use of the RITARD system. The state of the APUD system of the intestine of the animals and morphological changes in internal organs in experimental cholera were described. As noted in this study, the manifestation of changes in the intestine and other organs, as well as the reaction of apudocytes to V. cholerae infection, were linked with the intensity of diarrhea and the time of the death of the animals.

[Differentiation and cytogenesis of endocrine elements of the rat duodenum in ontogenesis]. / Differentsirovka i tsitogenez éndokrinnykh élementov dvenadtsatiperstnoi kishki krysy v ontogeneze.

Duodenal endocrine apparatus was studied in rat during individual development using electron microscopy. Endocrinocyte differentiation was demonstrated to occur in embryonic period and it is characterised by fast cytotype number growth. During embryogenesis processes of endocrinocyte differentiation occur more intensely than in adult animals which is manifested by higher incidence of different types of incretory elements in embryos. By the moment of birth EC-, L-, S-, D-, D1-, P and I-cells can be identified in the duodenal epithelium at different stages of differentiation as well as "mixed" exo-endocrine cells. The presence of transitory cellular forms from agranular elements up to mature differentiated endocrinocytes and "mixed" exo-endocrine cells reflects cytogenetic processes in population of endocrine cells and allows to consider duodenal epithelium both structurally and functionally as a tissue with common histogenetic basis.

Innervation of the adrenal cortex, its physiological relevance, with primary focus on the noradrenergic transmission.

The current knowledge of the catecholaminergic innervation of the mammalian adrenal cortex is summarized, and macro- and microscopic neuromorphology, including the central nervous system connections of the adrenal cortex, is briefly discussed. Morphological and functional data on the catecholaminergic (i.e., noradrenergic) innervation of the adrenal cortex are reviewed. Experimental data suggest that in addition to the regulation of adrenal blood flow, the noradrenergic innervation has a primary influence on zona glomerulosa cells possibly via beta 1 adrenergic and dopaminergic receptors (DA2 subtype via inhibiting T-type Ca2+ channels) It is concluded that the local, modulatory effect of noradrenergic nerve fibres, terminating in the close vicinity of the zona glomerulosa cells, on the systemic renin-angiotensin-aldosterone and other peptide cascade may be influenced by neuropeptides, particularly neuropeptide Y and vasoactive intestinal peptide.

Diffuse neuroendocrine system: structural and functional effects of radiation injury to amine precursor uptake and decarboxylation (APUD) cells.

The paper presents a review of the results obtained by the authors on the study of external (gamma) and internal (I-131) radiation effects on the functional morphology and linkage of the diffuse neuroendocrine system (DNES) and amine precursor uptake and decarboxylation (APUD) cells of the stomach and duodenum. The investigations performed enabled us to determine that the morphological changes noted in APUD cells had a dose and time dependency. The present study supports the point of view that the radiation initiates serotonin release from APUD cells, which appears to initiate the mechanism of early postirradiation dysfunctions of the gastrointestinal tract and the subsequent adaptive response of DNES. Analysis of our results, together with a review of the literature, indicates that APUD cells actively participate both in pathogenesis of radiation injury and development of organ and tissue radiosensitivity.

The prostatic endocrine-paracrine (neuroendocrine) regulatory system and neuroendocrine differentiation in prostatic carcinoma: a review and future directions in basic research.

Endocrine-paracrine (neuroendocrine, amine precursor uptake and decarboxylation [APUD]) cells of the prostato-urethral region are serotonin and peptide containing regulatory cells, which are part of a dispersed neuroendocrine regulatory system also known as the APUD system. These cells most likely regulate growth and differentiation, as well as the secretory functions of the prostate. Prostatic carcinoma exhibits neuroendocrine differentiation in 3 forms: 1) small cell neuroendocrine carcinoma, 2) carcinoid-like tumors and 3) conventional prostatic adenocarcinoma with focal neuroendocrine differentiation. Small cell carcinoma and carcinoid-like tumors are rather rare (1 to 2% of all prostatic malignancies) and generally pursue an aggressive course. Focal neuroendocrine differentiation in adenocarcinoma is extensive in 10% of the cases and may be present in virtually all adenocarcinomas to a minor degree. There are conflicting studies on the prognostic significance of focal neuroendocrine differentiation in prostatic carcinoma, although several suggest a poor prognosis. The finding that serum neuroendocrine markers predict initial insensitivity to or the development of resistance to hormonal suppression therapy, coupled with the recent observation that androgen receptor is not expressed in neoplastic neuroendocrine cells suggests that neuroendocrine differentiation directly results in resistance to hormonal manipulation therapy. Neuroendocrine differentiation in prostatic carcinoma raises the possibility of innovative modes of treatment. Future directions of research should concentrate on the quantitative analysis of serotonin and various peptides in prostatic malignancy, since high levels of constitutive secretion may not be appreciated by immunocytochemistry, as well as analysis of tumors for receptors to neuroendocrine products, which are necessary for these products to have a functional role. Finally, specific subtypes of neoplastic cells with neuroendocrine differentiation based on serotonin and peptide profiles should be analyzed.

Morphological aspects of endocrine cells in human fetal gastrointestinal mucosa. Microscopical, electronmicroscopical and immunohistochemical studies.

This paper describes the morphological features and distribution of endocrine cells in the human fetal gastrointestinal mucosa between the 8-9th and the 36th the weeks of gestation. We used techniques of argentic impregnation, techniques with chromogranine and neuron specific enolase, electronmicroscopical techniques and immunohistochemical techniques as well (PAP and ABC) with antibodies for G cells, EG cells, D cells, S cells CCK (I) cells and EC cells. The first argyrophilic and/or argentaffin cells appear in the fetal gut of 8-9 weeks old. We describe the appearance, distribution, morphology of the identified endocrine cells with immunohistochemical techniques and we discuss the possible morphofunctional interrelations between them, but also with the neighbouring structures like lymphoid tissue in ileum, colon and appendix in embryofetal period.