Immunocytochemical demonstration of enkephalin and beta-endorphin in endocrine tumors of the rectum. A survey of 27 colo-rectal carcinoids

In a histopathological and immunocytochemical study of biopsy and/or operation specimens from 27 patients with endocrine tumors of the colon and rectum ("hind-gut carcinoids") enkephalin-immunoreactive tumor cells were observed in two cases. Both patients were obese women, about 50 years of age, with a history of constipation. The tumors were situated near the anus in the dorsal wall of the rectum. One tumor had metastasized to a lymph node, and the other showed vascular invasion. The tumor cells were non-argentaffin; some were argyrophil. One tumor contained only few enkephalin-immunoreactive cells but had numerous beta-endorphin-immunoreactive cells, which were distinct from the former. The other contained large numbers of enkephalin-immunoreactive cells but no beta-endorphin cells. Both tumors also harboured glucagon-immunoreactive cells; in one there were also cells containing immunoreactive pancreatic polypeptide. These cells were distinct from the enkephalin-storing ones. No 5-hydroxytryptamine could be detected in the two tumors.

Gut-islet endocrinology-some evolutionary aspects

Immunological and biological studies have shown that many of the mammalian gastroenteropancreatic (GEP) hormones have counterparts in lower vertebrates. Hormonal localization in cyclostomes and fishes suggests that insulin was phylogenetically the first islet hormone, followed by somatostatin, glucagon and, last, pancreatic polypeptide (PP). Some of the GEP peptides are present in the central and peripheral nervous system of lower vertebrates as well as mammals. GEP hormone-like substances resembling insulin, somatostatin, glucagon, PP, gastrin, secretin, VIP, substance P and enkephalin also occur in protostomian invertebrates (Annelida, Arthropoda, Mollusca), particularly in their nervous system. These findings indicate that the vertebrate hormones may have originated in neural tissue before the development of the vertebrate line of evolution.

Immunocytochemical studies of the evolution of islet hormones

By using both immunofluorescence and peroxidase-anti-peroxidase procedures to detect cells producing the four islet hormones, supplemented by biochemical, biological, and radioimmunological assays of tissue extracts, it has been shown that insulin seems to be the most original hormone, apparently occurring already in invertebrates in cells of open type in the alimentary tract mucosa. Insulin cells also predominate in the first islet organ, namely that of the cyclostomes. The order of appearance in the endocrine pancreas during the subsequent evolution is: somatostatin; glucagon; and the pancreatic polypeptide. Even in lower vertebrates pancreatic polypeptide cells occur in those parts of the pancreas situated in close proximity to the gut.

The insulin receptor and insulin of the Atlantic hagfish. Extraordinary conservation of binding specificity and negative cooperativity in the most primitive vertebrate

The North Atlantic hagfish, a cyclostome that is representative of the most primitive vertebrates still alive, diverged from the other vertebrates about 500 million years ago. Hagfish insulin, which differs from porcine insulin in 18 (38%) of its amino acids, had a potency of 5-10% that of porcine insulin in stimulating glucose oxidation and deoxyglucose transport in rat adipocytes and was 5-10% as potent as porcine insulin in binding to insulin receptors on rat adipocytes and human (IM-9) lymphocytes. Like all other naturally occurring insulins, hagfish insulin accelerated the dissociation of 125I-porcine insulin from insulin receptors and the degree of the acceleration was related to its occupancy of the receptor. The insulin receptor of the hagfish erythrocyte showed the time, temperature, and pH dependence of binding and the negative cooperativity that are characteristic of all other insulin receptors. That the negative cooperativity is fully conserved in such an ancient insulin and receptor suggests that it is an important functional feature of this hormone-receptor system.

The hagfish receptor showed the same absolute affinity and rank order of preference for insulins and insulin analogues (chicken > pork > proinsulin > guinea pig > desoctapeptide) found with other receptors of less primitive vertebrates, which supports the conclusion that the receptor for insulin is functionally better conserved evolutionary than the hormone. However, uniquely, hagfish insulin was more potent in binding to hagfish receptors than to mammalianreceptors; with all other species of insulins studied, the affinity of the hormone for homologous receptor was the same as for receptors of heterologous species.

Hepatomas and other neoplasms in the atlantic hagfish (Myxine glutinosa): a histopathologic and chemical study

M. glutinosa is a cyclostome, living in the mud in seawater of high salinity. It probably is a stationary scavenger feeder. About 28,000 hagfish from the Gullmar Fjord were examined during a 5-year period for the occurrence of tumors. Hepatomas were found to be predominant neoplasm, observed at a frequency that decreased from 5.8% in 1972 to 2.9% in 1973 and finally to 0.6% in 1974--76. Islet cell hamartomas and frank neoplasms decreased from 0.5% in 1972 to less than 0.1% in 1973--76. Occasional subcutaneous and mesenterial neoplasms were also observed during 1972--74. In hagfish caught 12 km out in the open sea, the hepatoma incidence decreased from 2.8% in 1972 to 0.9% in 1974. Given this background, it is possible that pollution of the Gullmar Fjord by carcinogenic substances with low biodegradability has occurred until 1972, and this pollution could be of etiologic significance for these hagfish tumors. In fact, the use of PCBs became prohibited by law in Sweden in 1971--72. Severe restrictions were also introduced for the use of chlorinated pesticides, notably DDT, and associated substances (DDD, DDE). Preliminary analyses for the presence of PCBs, DDT (and its metabolites), and aflatoxins (the notorious hepatocarcinogen) were performed by gas chromatography and thin-layer chromatography. Livers (with and without neoplasms) from hagfish caught inside the threshold of the fjord contained about 5 mg/kg of wet weight of PCBs and about 0.1--0.4 mg/kg of dry weight of DDT, DDD, or DDE, whereas those from hagfish caught in the open sea had a much lower PCB concentration (about 0.2 mg/kg of wet weight). No PCBs and no chlorinated pesticides were found in analyses of the mud at the catching site. High PCB concentrations (3 mg/kg of wet weight) were, however, observed in livers from cod living in the Gullmar Fjord, and it was proposed that bony fish may be the source of hagfish liver PCBs. PCB chromatograms of hagfish livers differed from those of PCB standards and cod liver. This strange pattern, which was not seen in livers from hagfish caught in the open sea, might be explained by an unusual mode of metabolization. The assays for aflatoxins gave completely negative results.

[Immunofluorescent demonstration of pancreatic polypeptide (PP) in pancreas and digestive tube of bony and cartilaginous fish]

When antisera specific against bovine PP (BPP) were used, immunoreactive parenchymal cells were observed in the endocrine pancreas and in the gastro-intestinal tract of the teleost bony fish Cottus scorpius, as well as in the pancreas of the elasmobranchian cartilaginous fish Squalus acanthias. Of the two principal islets of Cottus, PP-cells were located selectively to that in the pyloric region.

Phylogeny of insulin. Some evolutionary aspects of insulin production with particular regard to the biosynthesis of insulin in Myxine glutinosa

Preceding phylogenetic studies on the occurrence of insulin have shown--e.g. by bioassays and immunocytochemical procedures--that insulin producing B-cells are present in all vertebrates and even in several invertebrates, both protostomian and deuterostomian. The most original B-cells are obviously endocrine cells of open type, situated in the mucosa of the alimentary tract. Moreover, the results of these studies show that insulin is not only a polypeptide hormone of considerable age but also that the insulin molecule seems to have been kept surprisingly stable during evolution. Best known of all non-mammalian insulins is that from the hagfish, Myxine glutinosa. It is probably the most original insulin of all in the vertebrate series. Both the amino-acid sequence and the three-dimensional structure of the dimer of hagfish insulin differ only little from those of pig insulin. The biosynthesis occurs via proinsulin and is also in most respects similar to mammalian insulin biosynthesis. There are, however, some differences. Although it readily crystallizes as tetragonal bipyramids, hagfish insulin does not form hexamers. In a test system, with isolated rat fat cells, its binding affinity is 23% and its potency 5% of that of pig insulin, a discrepancy indicating a "partial antagonism" on the receptors. Although the conversion of proinsulin to insulin seems to occur in the secretion granules, they contain no crystalline cores. Since a strictly tryptic-like enzyme was found to destroy hagfish insulin rapidly, the enzyme converting proinsulin to insulin must--in addition to a carboxy-peptidase-B-like activity--have a different specificity in Myxine.

Zinc and manganese contents of micro-dissected pancreatic islets of some rodents. A microchemical study in adult and newborn guinea pigs, rats, Chinese hamsters and spiny mice

By a flameless atomic absorption spectrophotometry procedure, using a graphite furnace, it was possible to assay the contents of zinc and managanese in micro-dissected pancreatic islets of several rodents. Interest was focused upon the islets of guinea-pigs, due to the fact that guinea-pig insulin lacks a histidine residue in the B10 position of the molecule which normally binds zinc (or other heavy metals) in the hexamer formation, probably involved in the storage of insulin. Both the zinc and manganese contents were too low in the guinea-pig islet parenchyma to be reasonably involved in the storage of insulin in the beta-granules. Instead, it was suggested that guinea-pig insulin, like hagfish insulin, might crystallize without access to zinc or other heavy metals. Low zinc and manganese contents were also observed in newborn and diabetic guinea-pigs. The islet zinc content was high in the Wistar rat, the Chinese hamster, and the spiny mouse. No significant amounts of manganese were found in any of these kinds of islet parenchyma.

Microchemical assays of glutathione, zinc, cobalt and manganese in micro-dissected areas of the endocrine pancreas in the hagfish, Myxine glutinosa

In hagfish islet parenchyma, consisting practically only of insulin-producing B-cells and agranular B-cell precursors, the contents of glutathione (GSH) and total protein-free thiols (NPSH) were determined on micro-dissected islet lobules. GSH was found to be of the same order of magnitude (22-25 mg/100 g wet weight) as in the islet parenchyma of a previously studied teleost fish and of some mammals, including man. However, the NPSH was found to be considerably higher in the islet lobules of the hagfish than in the teleostean islet parachyma. As in both teleost fish and mammals, GSH made up most of the NPSH in the hagfish erythrocytes, myocardium, and skeletal musculature. This discrepancy between hagfish islet parenchyma and other tissues indicates that the non-GSH portion of NPSH may be of particular significance for the insulin-producing B-cells. By means of flameless atomic absorption spectrophotometry the contents of zinc, cobalt, and manganese were determined in micro-dissected hagfish islet lobules. Neither zinc, nor cobalt, occurred in significantly higher concentrations in the islet parenchyma than in the liver or the skeletal musculature. Only manganese was found in somewhat higher amounts in the islet lobules than in the other tissues, but the contents were still low. The results indicate that none of the three heavy metals play any important role in the synthesis, storage, or release of insulin in the hagfish. The significance of this in relation to the prevailing hypotheses regarding the pathogenesis of alloxan diabetes is discussed.

Structural analysis of the molecular evolution of some gastro-entero-pancreatic hormones

By means of a statistical analysis of the occurrence of amino-acid residues in the polypeptide chains of several gastro-entero-pancreatic (GEP) hormones an investigation was undertaken to determine whether any of these hormones might be related to each other--possibly from an evolutionary point of view. Particular interest was paid to the occurrence of small charged segments, i.e. those with acidic or basic amino acid residues, since such segments can be presumed to play a role in hormonal receptor binding mechanisms. By this method hormonal relationships were suggested by the observation that these small charged amino-acid sequences, contained in the hormonal structures, match as a result of non-randomness. It was found that hagfish and human insulin were related on a molecular level not only to the newly discovered (avian, bovine, human) pancreatic polypeptide (PP) but also to some other GEP hormones (VIP, GIP, glucagon) as well as to calcitonin and to the alpha-subunit of the glycoprotein hormones. Interpretation of the statistical data suggests that all these peptide hormones are related by a common hexapeptide sequence which contributed, at an evolutionary point, to their molecular architecture. A hexapeptide segment of APP is statistically related to a sequence of equal size in the carboxy terminal region of the A-chain of both hagfish and human insulin, providing the first instance of their structural similarity. Correlations between PP, insulin, glucagon, VIP, and calcitonin provide a tentative basis for predicting the production of one or more of these peptide hormones by immature or de-differentiated cells of neoplasms and non-neoplastic pathologic lesions of the GEP endocrine system.

Some phylogenetical aspects on the occurrence of somatostatin in the gastro-entero pancreatic endocrine system. A histological and immunocytochemical study, combined with quantitative radioimmunological assays of tissue extracts

Rodioimmunoassayable somatostatin (SRIF) was found in acid ethanol extracts from various parts of the gastro-entero-pancreatic (GEP) endocrine system in reptiles, amphibians, teleost bony fish, cartilaginous fish, and jawless fish, as well as in a deuterostomian invertebrate, the tunicate, Ciona intestinalis. The cellular sites could, as a rule, be easily visualized light-microscopically by the peroxidase-anti-peroxidase (PAP) immunocytochemical procedure, using guinea-pig and rabbit antisera against synthetic SRIF. The standard Hellerström-Hellman technique, used to detect argyrophi SRIF-storing D cells, failed to visualize the SRIF cells in teh GEP endocrine system of the tumicate and of the jaw-less fish. Moreover, the results comfirmed the previous description that this technique only exceptionally (and sometimes only after further modifications) gave positive results when applied to the GEP endocrine system of bony fish, amphibians, and reptiles. In cartilaginous fish, however, it worked adequately and confirmed the radio-immunological and immunocytochemical observations. In the mucosa of the alimentary tract and in the parenchyma of its associated glands of one echinoderm and two pelecypod molluscs and one crustacean arthropod no sgns of the occurrence of SRIF-storing cells were observed using the three correlated procedures. In several of these tissues, signs of the occurrence of insulin-producing cells had perviously been observed. Thus, SRIF seems to appear at a later evolutionary stage than insulin. The principal islets (Brockmann corpusles) of the marine teleost fish, Cottus scorpius, had the highest concentrations of radioimmunoassayable SRIF of all the GEP organs and tissues investigated, viz. about 200 ng/mg wet weight. Nevertheless, it was only 1/5 of the actual insulin content.

Onto- and phylogenetical aspects on insulin-producing islet-cell tumors

When onto- and phylogenetical aspects are taken into account when studying insulin-producing islet-cell tumors, it becomes clear that the recently discovered "type IV" islet parenchymal cells (or "delta 1" -cells) may play an important role in various states of hypoglycemia, both of neoplastic and non-neoplastic origin. Moreover, it becomes obvious that increased attention to this kind of islet cell through intensified light-microscopical, histochemical, ultrastructural and experimental investigations covering a wide range of animals, may help to clarify several unsolved problems in the cytological composition of the islets of Langerhans. The occurrence of islet-cell tumors (or hamartomas) in the most primitive vertebrate islet parenchyma known, viz. that of the hagfish, Myxine glutinosa, is reported, as well as an additional case of mixed carcinoid-islet-cell tumor in a human pancreas.

Persistent neonatal hypoglycaemia. A clinical and histopathological study of three cases treated with diazoxide and subtotal pancreatectomy

Two boys and one girl developed persisting hypoglycaemia 12, 24, and 48 hours after birth. Although there was no known history of hereditary diabetes mellitus, the birth weight was high in two cases, and some additional traits of foetopathia diabetica could not be excluded clinically. All had high serum insulin levels with frank hyperinsulinaemia in one case. Glucose tolerance tests also indicated hyperinsulinism. Diazoxide (8 to 27 mg/kg) elevated the blood glucose levels, but did not prevent severe hypoglycaemic episodes. The effects of subtotal pancreatectomy were only transient. The patients have now been kept on permanent diazoxide therapy for 2-4 years at dosages slightly lower than those used before operation. No islet-cell tumour was found at the subtotal pancreatectomy. In all 3 cases, the pancreatic islets were markedly hyperplastic and of irregular shape with the occurrence of large B-cells with giant hyperchromatic nuclei and chromophobe "agranular" or sparsely granulated cells. The predominating kind of islet cells showed tinctorial features of A2-cells but--in the absence of available material set aside for ultrastructural analysis--it could not be settled whether this was a result of a proliferation of A2-cells only or of "type IV cells" as well. Against the background of previously published reports, the present cases serve to illustrate that additional accuracy of diagnosis and classification of neonatal persistent hypoglycaemia requires quantitative information about the structural changes in the pancreatic islet cells, and that this can be obtained from conventional biopsy specimens.