Light and electron microscopic identification of several types of endocrine cells in the gastrointestinal mucosa of the cat

Cell proliferation in pathogenesis of esophagogastric lesions in pigs

Esophagogastric ulcer is an independent disease in swine that is characterized by ulcerous autodigestion of the cutaneous mucosa, which does not exhibit a tendency to recover, but, on the contrary, a tendency toward severe hemorrhaging, with a predominantly lethal outcome. Since it develops in the part of the stomach that is morphologically and functionally different from other glandular mucosa, it was questioned earlier whether it could be a peptic ulcer based on its nature. Spontaneous ulcers, usually of the stomach, commonly occur in many domestic animals. Some of these lesions are chronic and they may occur in either the glandular or squamous-lined regions of the stomach. As with the human disease, the pathogenesis in domestic animals is multifactorial, poorly understood, and variable between and within species. Environmental stress and dietary factors are very important in the ulcer disease in swine. It has been shown that the Helicobacter spp. is strongly associated with naturally occurring ulcer and preulcer lesions of the pars esophagea in swine, which raises the possibility that Helicobacter spp. is an important factor in the pathogenesis of these lesions. The dynamics of the development of esophagogastric ulcers imply hyperplastic lesions (parakeratosis and hyperkeratosis), keratolysis, erosions, peptic necrosis, and the development of ulcers with all the characteristics of peptic ulcerations in other localities. In addition, K6 is expressed in association with the mucosal changes. The pattern of the intermediate filaments of keratin suggests that epithelial proliferation, which leads to visible hyperkeratosis, constitutes the essence of gastric ulcers in swine.

Immunocytochemical and ultrastructural characterization of endocrine cells in the larval stomach of the frog Rana temporaria tadpoles: a comparison with adult specimens

According to immunostaining and ultrastructural patterns, Rana temporaria tadpole stomach displays a well-differentiated endocrine population comprising, at least, six cellular types: ECL, EC [serotonin], D [somatostatin] - all three of them abundant -, P [bombesin] - less numerous -, CCK-8 [cholecystokinin/gastrin] and A [glucagon/glicentin] - both very scarce. Larval endocrine cells are mainly located in the surface epithelium and show open or closed morphologies. Cellular diversity is similar in tadpoles and frogs, with the exception of immunoreactivity for gastrin-17, found in adults in numerous cells. Larval cells display mature ultrastructural traits, although with smaller secretory granules. The different distribution of endocrine cells, which in adults are preferentially located in the glands, probably refers to different functional requirements. However, the rich vascular plexus present in larval mucosa may be an efficient transport medium of surface hormones to-gastric targets. The enhancement in adults of endocrine population and correlative increase in hormonal secretion indicates a more active functional role, probably related to the shift from herbivorous to carnivorous habits. In summary, the tadpole gastric endocrine population, although not as numerous as that of adult frogs, displays histological traits that indicate a relevant (immunoreactive and ultrastructural properties, cellular diversity) and specific (surface location, relative abundance of open-type cells) role of local regulatory factors in amphibian larval gastric function.

Gastric endocrine cells: types, function and growth

The history of gastric endocrine cells identification and functional characterization is briefly outlined. An up to date classification of such cells is given. Present status of histopathological, histochemical, ultrastructural and molecular investigations on gastric endocrine hyperplasia and neoplasia is summarized and briefly discussed.

[Development of the gastric glands of cats (Felis silvestris catus)]

There are five stages in the development of the cat's gastric glands: 1. During the stage of the indifferent epithelium from day 19 to day 24, the anlage of the stomach develops with all layers; 2. The stage of gland formation from day 24 to day 41 is the beginning of the gland buds. They develop in connection with endocrine cells on day 34 into primitive oxyntic and primitive mucous cells. The latter form the basis for all other cells, including the surface mucous cells; 3. During the stage of gland evagination from day 42 to 55, the anlagen are separated into primitive pits and tubules, while the cells continue to differentiate and the first intermediate cells are seen; 4. The stage of gland branching from day 56 to birth is characterized by the formation of additional glands at the bottom of the pits which change the ordinary anlagen into branched glands. During this stage, the cardiac glands are formed; 5. In the stage of gland maturation from birth to the 9th week, the peptic cells are formed and the glands start functioning. The oxyntic cells show carbonic-anhydrase activity and signs of acid secretion, and, between the weeks 4 and 8, the peptic cells contain pepsinogen, producing a negative reaction to PAS and a positive reaction to HID. Mucous cells and mucous neck cells produce PAS- and AB-positive mucin.

Ultrastructural classification of the endocrine cells of the large intestine of the calf. Cytochemical evidence of the presence of Viallis's pre-EC cells

GEP (Gastro-Entero-Pancreatic) endocrine cells were very numerous in the mucosal layer of the large intestine of the calf. Their frequence appeared to increase towards the distal portions of the gut. Endocrine cells were dispersed among epithelial cells lining intestinal glands and were frequently grouped together. Cellular shape was pyramidal or elongated; the cytoplasm was electron-lucent and contained highly characteristic secretory granules. Six different types of endocrine cells were identified on the basis of the ultrastructural aspect and cytochemical characteristics (silver-reactivity) of their secretory granules: EC, L, PP, A, D1 and D cells. EC and L cells were the most abundant in all localisations. They were especially numerous in the rectum. A subpopulation of EC cells was negative to Masson-Singh's reaction showing that they lack 5-HT. This observation enabled us to refer this latter cellular type to the "pre-EC" cells, described by Vialli as an earlier evolutive step of the EC cells population. Their presence in the calf gut might be linked to its possible "immaturity", due either to the age or to the alimentary diet.

Development of the bovine duodenum with reference to enterochromaffin cells

The present light microscopic study describes the morphological changes which occur in the duodenal mucosa of the bovine fetus from the third month of gestation until birth with regard to the sequence of appearance and morphology of enterochromaffin cells. The mucosa of the duodenum is prepared for digestive activity during the first months of development. This becomes obvious in the early differentiation of the fetal intestinal mucosa. The enterocytes in villus epithelium contain glycogen in the early months. These glycogen pools seem to shrink during the following months. They may provide a metabolic reserve for the fetus, which derives all of its nutrition from carbohydrates. Enterochromaffin cells appear in the three month old bovine fetus with two cell-types situated in the epithelial lining of crypts and villi. The density of enterochromaffin cells increases during gestation. There were no findings to indicate that the fetal enterochromaffin cells did not originate from endoderm. The early appearance from enterochromaffin cells (which are the producers of serotonin, 5-hydroxytryptamine) correlates with first gastrointestinal movements, which are known to commence in the first third of gestation, leading us to believe that 5-HT represents the chemical inducer of muscular motility in the developing intestine.

Ultrastructural identification of human secretin cells by the immunogold technique. Their costorage of chromogranin A and serotonin

We have localized secretin in a morphologically distinctive endocrine cell scattered in the epithelium covering the villi and uppermost crypts of the human duodenum and jejunum. The human secretin cell was characterized by relatively large (mean diameter 299 nm +/- 69 SD), fairly irregular granules, the majority of which showed homogeneous distribution of secretin and chromogranin A immunolabelling in a structurally homogeneous core. Other granules had a targetoid pattern due to an inner, argyrophobe, secretin-immunoreactive body surrounded by an argyrophil, chromogranin A immunoreactive mantle. These targetoid granules represent a distinctive ultrastructural marker of the secretin cell. Secretin cell granules have been shown to react with chromogranin A antibodies and Grimelius' silver, while lacking chromogranin B immunoreactivity. About 1/3 of secretin cells also showed serotonin immunostaining.

Effect of scorpion toxin on the enterochromaffin-like cells in normal and Trypanosoma cruzi-infected rats: a morphological study

Intravenous injection of scorpion toxin (Tityus serrulatus) in normal and Trypanosoma cruzi infected rats did not cause ultrastructural morphologic changes on enterochromaffin-like (ECL) cells of the stomach, although it induced a significant increase of the gastric secretion. Our data seem to indicate that gastric ECL cells structure is not affected by stimulation with scorpion toxin or by acute infection with T. cruzi in the rat.

The endocrine cells in the gut of Mugil saliens Risso, 1810 (Teleostei): an immunocytochemical and ultrastructural study

The endocrine cells in the gut of Mugil saliens Risso, 1810 (leaping grey mullet) were investigated by immunocytochemical and electron microscopic techniques. Gastrin-, glucagon-, and somatostatin-immunoreactive cells were identified in the cardiac and cecal stomach regions, located mainly in the lower part of the gastric folds and in the upper part of the glands. Substance P-, somatostatin-, and pancreatic polypeptide (PP)-immunoreactive cells were found between epithelial cells in the pyloric stomach region. Gastrin-, cholecystokinin (CCK)-, gastric inhibitory polypeptide (GIP)-, substance P-, Met-enkephalin- and PP-immunoreactive cells were observed throughout the intestine while only the last three of these appeared in the posterior intestine. Nine types of gastroenteroendocrine cells were ultrastructurally characterized; some of them were related to the cell types immunocytochemically identified.

Endocrine pancreas of Testudo graeca L. (Chelonia) in summer and winter: an immunocytochemical and ultrastructural study

Insulin-, glucagon-, somatostatin-, and PP-immunoreactive cells were identified immunocytochemically using antisera raised against mammalian hormones in the pancreas of Testudo graeca in both winter and summer. The endocrine cells were present throughout the gland, forming scarce islets except in the splenic region. The insulin cell islets were larger and more numerous in the splenic region than in the duodenal one. Winter glucagon-immunoreactive cells were found mainly in isolation while the summer ones occurred in groups which showed no immunoreactive central area; in both seasons these cells were more numerous in the splenic region than in the duodenal one. Somatostatin-immunoreactive cells were found isolated or grouped together more frequently in the splenic region in the summer specimens. No PP-immunoreactive cells were found in the splenic region, although they were numerous and isolated in the duodenal zone. Four cell types (B, A, D, and PP cells) were ultrastructurally characterized by the shape, size, and electron density of their respective secretory granules. Certain ultrastructural differences were detected in the summer and winter endocrine pancreatic cells. In summer specimens a fifth cellular type was observed. The presence of B, D, and PP cells among the epithelial pancreatic duct cells may confirm the comparatively primitive organization of the T. graeca endocrine pancreas.

Ultrastructural studies of endocrine cell populations showing an argentaffin reaction and/or serotonin immunoreactivity in the rat antral mucosa

On the basis of staining results in closely related semi-thin sections from rat antral mucosa immunostained with polyclonal serotonin antibodies and silver-stained for the argentaffin reaction, respectively, three different cell populations could be distinguished. One of these cell populations showed both serotonin immunoreactivity and an argentaffin reaction, a second one serotonin immunoreactivity alone, and a third one only an argentaffin reaction. These cell populations were studied electron microscopically in ultra-thin sections located between the stained semi-thin sections. The cell population displaying an agentaffin reaction and serotonin immunoreactivity showed secretory granules of the enterochromaffin cell type. A similar granular appearance was observed in cells which only exhibited an argentaffin reaction. Serotonin immunoreactivity in the absence of an argentaffin reaction was evident in some G (gastrin) cells, and in some D1 and possibly also some D (somatostatin) cells; but not all the endocrine cells of the non-enterochromaffin type displayed serotonin immunoreactivity. The significance of the different reactions in the three cell populations is discussed.

Application of Grimelius argyrophil staining to the study of tumour ultrastructure. I. Effects of fixatives

Two methods have so far been proposed for staining samples by the argyrophil technique of Grimelius for electron microscopy. For Håkanson glutaraldehyde prevented argyrophilia, so the author stained sections from samples previously fixed by double formaldehyde/osmium tetroxide treatment and embedding. Vassallo used en bloc staining after fixation with glutaraldehyde-formaldehyde mixtures. We examined each factor which could directly interfere in argyrophil staining en bloc and on section. In the present experiment we compared effects of fixatives after staining en bloc. Glutaraldehyde prevented argyrophilia in 1 case out of 15, that of A-like cells in the oxyntic gland of the rat positivity was maintained in EC-like cells of this gland and adrenalin cells of the adrenal gland contrary to the previous description.

Effects of portacaval shunt on the rat stomach

In portacaval-shunted rats, basal but not pentagastrin-stimulated acid secretion was higher than in sham-operated controls. The basal serum gastrin concentration was unchanged and the postprandial serum gastrin concentration lowered following portacaval shunt. Thus, gastrin is not responsible for the elevated basal acid secretion. The present study provides evidence that there is no trophic effect on the oxyntic mucosa as a whole and that there is no change in parietal cell-associated gastrin receptors after portacaval shunting. Interestingly, however, endocrine cells in the oxyntic mucosa (the histamine-containing ECL cells) proliferated greatly and the pentagastrin- and cholecystokinin octapeptide-induced activation of the histamine-forming enzyme, histidine decarboxylase, in these cells was much greater than in control rats. Analysis of the dose-response curves for the enzyme-activating effect of pentagastrin and cholecystokinin-octapeptide indicated that the D50 values for these two stimulants were not altered by shunting but that the maximal enzyme activation was greatly elevated. The enhanced enzyme activation can be partly, but not fully, explained by the fact that the ECL cells were increased in number. The enhanced response following portacaval shunt probably reflects also an increased number of gastrin receptors per ECL cell. The effect of portacaval shunting on gastric ECL cells can perhaps be explained by impaired degradation in the liver of intestinal substance(s) exerting a highly specific trophic effect on the ECL cells or, alternatively, causing an enrichment of gastrin receptors on these cells, thereby making them more sensitive to the trophic effect of gastrin. The ECL cell hyperplasia is manifest about 4 weeks after the shunting. A modified procedure for portacaval shunting which left the gastroduodenal vein (otherwise ligated) drained to the liver produced the same trophic effect as conventional portacaval shunt, suggesting an intestinal rather than gastroduodenal origin of the agent(s) responsible for the trophic action.

Ultrastructural localization of cholecystokinin in endocrine cells of the dog duodenum by the immunogold technique

Cholecystokinin (CCK) has been localized by the immunogold technique in a type of endocrine cell of the dog duodenum characterized by small (166 +/- 38 nm) secretory granules with fairly dense, homogeneous core separated from its enveloping membrane by a thin clear space. The CCK cell is immunocytochemically distinct and cytologically different from other types of endocrine cells, as the secretin, GIP and motilin cells, already identified in the dog duodenum.

Light microscopic histochemistry on plastic sections

As compared with conventional paraffin, celloidin, and frozen sections, semithin plastic sections offer a superior quality of the light microscopic image in terms of better resolution, absence of distortion and shrinkage artifacts, and suitability for calcified tissues. Application of histochemical methods to such sections often encounters, however, serious difficulties resulting from a considerably reduced reactivity of plastic-embedded biological material. Factors involved include a poor penetration of reagents into plastic embedding media due to a steric or hydrophobic hindrance, as well as a blockade of the reactive chemical groups in the sample due to interactions with fixatives and plastics. Embedding in polar (hydrophilic) plastics, such as glycol methacrylate, permits carrying out a large number of histochemical reactions, including the demonstration of enzymatic activities, directly on sections, but is less suitable for combined light/electron microscopic studies because of an imperfect ultrastructural preservation of tissues. Embedding in nonpolar epoxy resins, particularly if combined with a double aldehyde-osmium fixation, results in a high quality ultrastructure but almost fully inhibits the histochemical reactivity of the embedded material. In order to restore this reactivity, i.e. to unmask chemical groups bound by the polymerized resin, semithin epoxy sections require the removal of the embedding matrix by alkoxides prior to the histochemical procedure. Additional steps are also often necessary: treatment of osmium-fixed sections with oxidative agents, e.g., hydrogen peroxide or periodate which reoxidize the bound osmium and remove it from tissue, and a controlled proteolytic digestion, especially useful in immunocytochemical studies, which probably cleaves the bonds between the primary aldehyde fixative, and the reactive sites. This article reviews histochemical methods which have been successfully applied to plastic-embedded material. Using polar methacrylates and/or nonpolar epoxy resins as embedding media, it has been possible to demonstrate proteins and aminoacid residues, carbohydrates, lipids, nucleic acids, biogenic amines, inorganic ions, and some enzymes, although the spectrum of methods found as suitable for plastic-embedded material is far narrower than that available for paraffin or frozen sections.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocrine cell populations in the colon and rectum of cat, dog, and monkey: fine structure, immunocytochemistry, and distribution

Comparative and quantitative ultrastructural studies of endocrine cells from the large bowel of European cat, beagle dog, and the monkey Callitrix jacchus were performed. The cat and monkey exhibited a roughly similar distribution of colonic endocrine cells with a frequency increasing toward the distal. On the contrary, the highest endocrine cell frequency in the dog colon was in the cecum. In the dog and monkey, enterochromaffin (EC) cells were predominant in all segments. In the cat, non-EC cells were predominant in the proximal colon. For each colonic segment, relative percentages of EC and non-EC cells appeared on the whole to be roughly stable between individuals of the same species. Three subtypes of EC cells were distinguished in each species. Non-EC cells were characterized by large variation in size and electron densities of their granules: Mean granule size per cell extended from 210 to 850 nm in cat, 310 to 770 nm in dog, and 130 to 470 nm in monkey. In each species, statistical analyses indicated that the non-EC cell population was composed of two or more subpopulations. Some similarities were found between colonic endocrine cells of the monkey and man, whereas obvious differences appeared between the two carnivorous mammals. Immunocytochemical studies demonstrated the presence of cells containing enteroglucagon, somatostatin, or a pancreatic polypeptidelike substance in the colon of the monkey and the rectum of the three mammals. Correlative immunocytochemical and ultrastructural studies showed that the three kinds of immunostained endocrine non-EC cells in each species had rather round granules, with great electron densities. Some subpopulations, morphologically distinguished, did not react to any of the antisera used. This suggests either the existence of secretory cycle in some endocrine cells or, perhaps, the presence of peptides still unknown in this part of the gut.

Ultrastructural localization of secretin in endocrine cells of the dog duodenum by the immunogold technique. Comparison with ultrastructurally characterized S cells of various mammals

Secretin has been localized by the immunogold technique in endocrine cells of the dog duodenum--previously described as "K cells"--characterized by secretory granules with double structure consisting of a secretin-containing osmiophilic core surrounded by an argyrophil halo. Granules resembling those of dog secretin cells were also found in some ultrastructurally characterized S cells of the cat, pig, rat and rabbit duodenum, thus confirming in these species the identification of S cells with secretin cells. Conversely, the cells previously described as "S cells" in the dog lacked secretin immunoreactivity.

Dynamics of the neuroendocrine cell--regulatory peptide system in the lung. Specific overview and new results

We assessed the changes in argyrophil neuroendocrine (NE) cell numbers, intensity of 5-HT fluorescence, and arterial medial thickness in the lungs of neonatal rabbits under various oxygen treatments. NE cell numbers and 5-HT fluorescence in normoxic rabbits increased from 12 hr before to 1 day after birth, and NE cells declined thereafter to the 10th day. In acute hypoxic (520 mm Hg for 2-2.5 hr) 5-day-old rabbits, 5-HT fluorescence was decreased, whereas NE cell numbers and medial thickness were unchanged. Neonates hypoxic from birth had higher NE cell numbers and increased medial thickness at 3 and 5 days, whereas 5-HT fluorescence was decreased compared with that in normoxic controls. These chronically hypoxic neonates showed a dramatic drop in argyrophil NE cell numbers to below normal when they were exposed to normoxia for 1 hr, but cell numbers and medial thickness returned to normal at 4 and 24 hr, respectively. We also tested the effect of acute and chronic hyperoxia: 100% O2 for 2-2.5 hr caused a significant drop in detectable NE cell numbers, whereas 40% O2 in N2 caused no change; chronic 40% O2 in N2 caused a fivefold increase in argyrophil NE cells by day 5, and medial thickness was below normal; 5-HT fluorescence decreased in acute 100% and chronic 40% hyperoxia and was elevated in acute 40% O2.

Gastrin cell proliferation after chronic stimulation: effect of vagal denervation or gastric surgery in the rat

Chronic stimulation of the antral gastrin cells by elevated antral pH was achieved by fundectomy, antrum exclusion, fundectomy plus antrum exclusion, antrocolic transposition, and vagal denervation plus pyloroplasty. For comparison we studied also the effects of pyloroplasty alone and of portacaval shunting. All operations that elevated the antral pH resulted in high gastrin concentrations in serum. Particularly high concentrations were observed in fundectomized rats. Vagal denervation of fundectomized or antrum excluded rats reduced the serum gastrin concentration slightly compared with the corresponding innervated animals. Portacaval shunting reduced the gastrin concentration in serum. The antral gastrin concentration was raised or unchanged following fundectomy and vagal denervation, and reduced following antrum exclusion, antrum exclusion plus vagotomy, fundectomy plus antrum exclusion, fundectomy plus vagotomy, antrocolic transposition and portacaval shunt. The gastrin cell density in the antral mucosa was raised following fundectomy, vagotomy, and fundectomy plus vagotomy, unchanged following fundectomy plus antrum exclusion and antrocolic transposition, and reduced following antrum exclusion and portacaval shunting. Ultrastructurally the gastrin (G) cells in the excluded antrum and in the antrum of fundectomized rats showed signs of secretory activity in that the granule volume density or the number of granules per unit cytoplasm was lowered. In the fundectomized rats moreover, the endoplasmic reticulum of the G cells was increased, the Golgi area enlarged and the proportion and volume density of electron dense granules greatly increased. The granule profile diameter was not affected by either antrum exclusion or fundectomy. The results on the excluded antrum indicate that elevated antral pH per se is not sufficient to produce gastrin cell proliferation. In the fundectomized rats, where the hyperlasia of antral gastrin cells was considerable, there is the added stimulus of ingested food. In fundectomized plus antrum excluded rats this stimulus is eliminated and no proliferation ensues. The passage of intestinal material, as in the rats subjected to antrocolic transposition, did not elicit gastrin cell proliferation which seems to suggest that the character of the luminal material is important. We propose therefore that gastrin cell proliferation is due to the combined stimulation of high antral pH and passage of food. Vagal innervation is not required.

Sequential differentiation of intestinal endocrine cells in the fetal mouse

The duodenum and ileum of 15 to 18-day old Swiss ICR mouse embryos were studied with the electron microscope to follow the differentiation of endocrine cells. Endocrine cells were classified on purely morphological characteristics. EC cells appeared at 16 days of gestation in both segments. At the same stage G cells were seen in the duodenum and K cells in the ileum. ECL, and S cells were identified in the duodenum at 17 days. Finally, D cells were seen at 18 days of gestation in the duodenum and ileum. With the electron microscope, endocrine cells were not identified in the small intestine of the mouse before the formation of villi.

[The localisation of endocrine cells in the distal esophagus (author's transl)]

At the esophago-cardiac junction squamous epithelium is intermingled with gastric epithelium. Within the lamina propria of the distal 3 cm of the esophagus we found cardiac glands with many argyrophil cells in 60% of cases. Electron microscopy revealed seven well knonwn types and two further forms which we could not identify: EC, ECL, D, D1, AL, I eg. M, S. It is supposed that these cells are modified neurotransmitters with a local activity. Their function is local regulation of the lower esophageal sphincter (LES).

Ultrastructure of the gut neurotensin cell

In mammals, neurotensin cells occur scattered in the epithelium of the jejunum-ileum. In chicken, neurotensin cells are abundant in the region of the gizzard-duodenal junction (antrum) where they occur intermingled with numerous somatostatin and gastrin cells. The neurotensin cells in chicken, dog and man were identified at the electron microscopic level by immunocytochemistry, using the consecutive semithin/ultrathin section technique. They contain numerous electron dense cytoplasmic granules, pre-dominantly in the basal portion of the cell. It was shown that these granules are the storage site for neurotensin. The neurotensin granules are round, highly electron dense and of about the same size in the different species examined (mean diameter 260--290 nm). In dog and man the granules have a tightly applied surrounding membrane while in the chicken a relatively electron lucent zone separates the electron dense core from the granule membrane. The ultrastructure of the neurotensin granules in chicken is somewhat reminiscent of that of the gastrin granules. The mean diameter of the gastrin granules in chicken antrum is 230 nm; for the somatostatin granules the mean diameter is 305 nm.

[Development and function of endocrine cells in the proventriculus of the chicken (author's transl)]

An argyrophil endocrine cell type with typical intraepithelial development is seen initially on the 8th day of incubation in the epithelium of the main lumen of the chicken-proventriculus. During the embryonic period, rapid development of these cells can be observed with a quantitative maximum on the 13th day of incubation. At this time increased digestive efficiency is necessary for the chicken embryo with the start of gastric secretion combined with the first swallowing of albumen. There is a subsequent decrease in the number of endocrine cells in the main lumen epithelium, their function in hatched or adult specimens is largely taken over by cells which appear in the epithelium of the glands of the proventriculus on the 16th and later days of incubation. On the 2nd day after hatching the adult distribution pattern of endocrine cells in the proventriculus is attained.

Histology, innervation and histochemistry of the UB gland in the Mexican cave fish Anoptichthys jordani Hubbs et Innes (Teleostei: Characidae)

The histomorphological investigations carried out on the ultimobranchial body of the Teleost Anoptichthys jordani Hubbs and Innes have enabled us to establish that it is an epithelial multifollicular body which lies within the transverse septum, beneath the musculature of the oesophagus and caudal to the Sinus venosus. Its parenchyma is surrounded by an extensive nerve network revealed by the Bodian silver technique. This nerve network and the occurrence of MAO activity in the ultimobranchial tissue indicate that it possesses a sympathetic innervation. The follicular epithelium sometimes acquire a pseudostratified condition in some follicles and sometimes in multistratified in others. In this latter case the presence of two main types of cell was noticed (light cells and dark cells). In these cells by the fluorescence microscopic analysis was revealed an intensely green fluorescence due to the presence of an aromatic monoamine, dopamine. This conclusion was further confirmed by the agreement between the argyrophilic cells and the fluorescent cells after silver staining. The possible partecipation of dopamine in the elaboration of polypeptide factor (calcitonin) is suggested. A notable analogy from the structural point of view to the calcitonin-producing cells of higher Vertebrates is also confirmed by the markedly argyrophilia of the main cells.

Serotonin containing and histamine containing cells in human stomach. Identification of these cells by fluorescent microscope and electron microscope

Paraformaldehyde (PF) treatment of epithelial cells of human stomach revealed intense yellow fluorescent granules within the cells. These granules were identified as serotonin on microspectrofluorometry. Serotonin containing cells were also identified as enterochromaffin cells (EC cells) under electron microscope and by the histochemical analysis. O-phthalaldehyde treatment (OPT) of epithelial cells in human stomach demonstrated whitish blue intracellular granules under fluorescence microscope. The cells containing these granules were identified as histamine containing cells on microspectrofluorometry, because of accordance in excitation and emission spectra with authentic histamine. Histamine-containing cells were considered to be identical to the mast cells, because of metachromatic property on toluidine blue staining and of close structural similarities under electron microscope.

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.

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.

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.

Identification of glucagon-producing cells (A cells) in dog gastric mucosa

An immunocytochemical technique using specific antiglucagon serum reveals the presence of glucagon-containing cells situated exclusively in the oxyntic glandular mucosa of the dog stomach. Electron microscope examination of the mucosa demonstrated endocrine cells containing secretory granules with a round dense core surrounded by a clear halo, indistinguishable from secretory granules of pancreatic A cells. Like the alpha granules of pancreatic A cells, the granules of these gastric endocrine cells exhibited a peripheral distribution of silver grains after Grimelius silver staining. Moreover, the granules of these cells were found to be specifically labeled with reaction product, using the peroxidase immunocytochemical technique at the ultrastructural level. Accordingly, these cells were named gastric A cells. These data suggest that the gastric oxyntic mucosa contains cells indistinguishable cytologically, cytochemically, and immunocytochemically from pancreatic A cells. It is believed that gastric A cells are responsible for the secretion of the gastric glucagon.

Cytochemical and ultrastructural differentiation of enteroglucagon and pancreatic-type glucagon cells of the gastrointestinal tract

Coordinated studies have been carried out on the glucagon immunoreactive cells of the mammalian gastrointestinal tract (man, dog, rat), using electron microscopy, silver staining and immunocytochemistry. Parallel ultrastructural and immunocytochemical studies have been made with the semithin-thin serial section technique. The results indicate that while the glucagon cells of the oxyntic portion of the stomach are virtually indistinguishable from those of the pancreatic islets (A cells) those of the intestine (EG cells) are completely different. Proper identification of glucagon immunoreactive cells requires the application of morphological and silver staining techniques, at the ultrastructural level.

Glucagon: role in the hyperglycemia of diabetes mellitus

Glucagon suppression by somatostatin reduces or abolishes hyperglycemia in dogs made insulin-deficient by somatostatin, alloxan, or total pancreatectomy. This suggests that the development of severe diabetic hyperglycemia requires the presence of glucagon, whether secreted by pancreatic or newly identified gastrointestinal A cells, as well as a lack of insulin. Glucagon suppression could improve therapeutic glucoregulation in diabetes.