Histochemical features of the Muscovy duck small intestine during development

We demonstrated for the first time the distribution and morphology of argyrophil and of goblet cells in the mucosa of the small intestine of the Muscovy duck during development using the Grimelius silver staining and alcian blue/periodic acid-Schiff (AB/PAS) staining technique. The argyrophil cells distribution was variable over the length of the small intestine from embryonic day 24 (24E) to post-hatching day 13 (13d). In the villi most argyrophil cells belonged to the open-type, while in the crypts they belonged to the closed-type. In the duodenum the density of argyrophil cells was highest at hatching, while in the jejunum and in the ileum the highest density value was at hatching and 13d. AB/PAS-positive goblet cells appeared on the villi and crypts of the duodenum and jejunum at 30E, and in the ileum at hatching. The density of AB/PAS-positive cells was the highest in the three segments at hatching. The AB-positive cells, compared with the PAS-positive cells, predominated in villi and crypts of the three segments, moreover the rate of AB-positive cells to PAS-positive cells significantly decreased from 30E to 9d. An increase in argyrophil and goblet cells number during the later incubation and at hatching, could indicate the small intestine in that period is being prepared to face a new diet.     

Systematics of Tanganyikan cichlid fishes (Teleostei: Perciformes)

The relationships among 53 genera of Tanganyikan cichlid fishes were analyzed based on internal and external morphological features. Comparison of the morphological cladistic tree with a previously proposed classification showed 5 of 12 tribes to be nonmonophyletic. Sixteen tribes were recognized, the changes in classification being that Trematocarini was treated as a junior synonym of Bathybatini; 5 new tribes were established for each of the following genera, Benthochromis, Boulengerochromis, Ctenochromis benthicola, Cyphotilapia, and Greenwoodochromis; Ctenochromis horei was transferred from Haplochromini to Tropheini; and Gnathochromis pfefferi was transferred from Limnochromini to Tropheini. The revised classification was supported by previously proposed molecular trees.     

Structure and development of first-generation teeth in the cichlid Hemichromis bimaculatus (Teleostei, Cichlidae)

In order to build a reference system to assess results of ongoing in vitro experiments on the study of epithelial-mesenchymal interactions during odontogenesis in actinopterygians, we have chosen to study the first-generation teeth of the cichlid Hemichromis bimaculatus from initiation until attachment both at the light and transmission electron microscopical level. Although their development follows the general pattern of teleost tooth formation, first-generation teeth show peculiarities compared with later tooth generations, including their size, bare emergence from the epithelium, absence of dentinal tubules and of nerves and capillaries in the pulp cavity, and organization of the outer dental epithelium. Four developmental stages (a to d) prior to attachment (stage e) have been distinguished. The oral epithelium invaginates into the underlying mesenchyme (stage a) and is later folded to form a bell-shaped dental organ (stage b) without any primordial thickening, or any other morphological indication of imminent invagination. Then, the collagenous enameloid matrix is laid down, most probably by the odontoblasts (early stage c), soon followed by predentine deposition and the beginning of enameloid mineralization (late stage c). With ongoing dentinogenesis, the enameloid matrix matures (stage d), i.e. the organic constituents are removed and the matrix further mineralizes. Finally (stage e), an annular collar of attachment bone is deposited to fix the tooth onto the underlying bone.     

Characterization of blood cells and hematological parameters in Cichlasoma dimerus (Teleostei, Perciformes)

The aim of the present study was to obtain a basic knowledge of the hematology of Cichlasoma dimerus. The morphological features of blood cells were described according to the observations made by light and electron microscopy. Erythrocytes, thrombocytes and four types of leucocytes: lymphocytes, monocytes, heterophils and eosinophils, were distinguished and characterized. Thrombocytes are the most abundant blood cells after erythrocytes and are recognized easily from lymphocytes by morphological features and size. Heterophils and eosinophils are PAS positive. Hematological indices (RBC, WBC, PCV, Hb, MCV, MCH, MCHC and leucocyte differential count) were measured in one blood sample from 30 adult fish captured in Esteros del Riachuelo, Corrientes, Argentina (27 degrees 25'S, 58 degrees 15'W). The reference interval and the mean were determined for each hematological parameter evaluated. Contrary to other species, the percent of heterophils was found to be high in relation to the percent of lymphocytes. Low lymphocyte counts occurred in C. dimerus, as compared to these found in other fishes. Compared to most teleosts, this species has similar mean values for PCV and Hb and slightly higher for RBC. Statistical analysis revealed that differences in hematological parameters between male and female fish were not significant.     

Strongyloides ratti: Mast cell and goblet cell responses in the small intestine of infected rats

Kinetics of intestinal mast cells and goblet cells were examined in relation to worm localization at various sites in the small intestine of rats infected with 3000 filariform (stage 3) larvae of Strongyloides ratti. The most marked intestinal mastocytosis was observed on Day 20 at the anterior site of the small intestine where the majority of the worms had concentrated. The number of mast cells in the posterior small intestine increased in parallel with the posterior shift of parasites at the later stage of the infection. In contrast to the intestinal mast cell response, the number of goblet cells was not significantly affected by the infection. These results strongly suggest that intestinal mastocytosis is closely related to the presence of the worms and that mast cells may play an important role for the expulsion of S. ratti.     

Some peptide-like colocalizations in endocrine cells of the pyloric caeca and the intestine of Oncorhynchus mykiss (Teleostei)

Summary The coexistence of immunoreactivities to cholecystokinin, glucagon, glucagon-like peptide 1, salmon pancreatic polypeptide, neuropeptide tyrosine, and peptide tyrosine tyrosine was studied immunocytochemicaly, revealing for the first time in fish intestine the existence in the same cell of immunoreactivities to cholecystokinin-glucagon/glucagon-like peptide 1, cholecystokinin-salmon pancreatic polypeptide, glucagon/glucagon-like peptide 1-salmon pancreatic polypeptide, glucagon/glucagon-like peptide 1-neuropeptide tyrosine, salmon pancreatic polypeptide tyrosine tyrosine, and glucagon/glucagon-like peptide 1-peptide tyrosine tyrosine. Colocalization of cholecystokinin-salmon pancreatic polypeptide was observed only in the pyloric caeca of the rainbow trout Oncorhynchus mykiss, while the other colocalizations also occurred in proximal and middle intestinal segments. In all cases, endocrine cells immunoreactive to only one of the paired antisera were detected except for anti-glucagon and anti-glucagon-like peptide 1, which always immunostained the same cells.     

Antioxidant effects of dehydroepiandrosterone and 7alpha-hydroxy-dehydroepiandrosterone in the rat colon, intestine and liver

This study examined in healthy male Wistar rats the in vivo antioxidant effect of dehydroepiandrosterone (DHEA) and 7alpha-hydroxy-DHEA administered by intraperitoneal injections (50 mg/kg body weight) for 2 or 7 days. Markers of oxidative damage to lipids (thiobarbituric acid-reacting substances, TBARS) and to proteins (protein carbonyls) were assessed in colon, small intestine, and liver homogenates. DHEA and 7alpha-hydroxy-DHEA caused a decrease in body weight. DHEA treatment significantly increased liver, colon, and small intestine cell weights. After 7 days, DHEA exerted an antioxidant effect in all organs studied. In the colon, oxidative damage protection was accompanied by a goblet cell proliferation and increase in acidic mucus production. After 2 days, the antioxidant effect of 7alpha-hydroxy-DHEA was mainly observed in the liver. Nonprotein sulfhydryl groups (mostly glutathione levels) were altered by DHEA in the liver whereas they remained unchanged after 7alpha-hydroxy-DHEA treatment. The results indicate that in healthy animals, DHEA exerts a protective effect, particularly in the colon, by reducing the tissue susceptibility to oxidation of both lipids and proteins. This effect was not limited to a specific tissue, whereas the metabolite 7alpha-hydroxy-DHEA exerted its antioxidant effect towards the two markers of oxidative damage earlier than DHEA, and mainly in the liver.     

Scale morphology and squamation patterns in cichlids (Teleostei, Perciformes): A comparative study

Problems in cichlid systematics call for new characteristics to be exploited. Scale surface morphology and squamation patterns could provide novel and useful information. A comparative study comprising 105 African, 10 American, and eight outgroup species was conducted to identify the most useful scale and squamation characters within the family and to clarify their phylogenetic significance. A great number of obviously genetically fixed characters were established. At least IS scale granulation types could be identified, proving to be ofparticular value for systematic purposes. Squamation patterns on the head, breast and fins were also found to be of interest in this context. Different character states are described and their distribution is reviewed, together with a discussion of their plesiomorphic status. From the results it can be concluded that for the Cichlidae scale and squamation studies can be valuable tools in investigating phylogenetic relationships.     

Aquaporin-9 is expressed in a mucus-secreting goblet cell subset in the small intestine

We analyzed the expression of aquaporins (AQPs) in the small intestine to elucidate their functions, and found that AQP9, which had not previously been detected there, is present in duodenum, jejunum, and ileum. AQP9 is expressed in colon as well, but not in stomach. Also, its expression in these intestinal sections is limited to the basolateral membranes of a goblet cell subset. Our finding that AQP9 is present specifically in goblet cells as mucus-secreting cells suggests its involvement in the synthesis and/or secretion of a certain kind of mucus which may protect the intestinal surface and smooth the flow of intestinal contents.     

Cytochemical and immunofluorescence investigations on insulin-like producing cells in the intestine of Mytilus edulis L. (Bivalvia)

Summary Insulin-like immunoreactivity can be localized to cells of the intestine in the-area of the hepatopancreas of Mytilus edulis L. No cross-reactivity can be obtained with anti-glucagon, anti-gastrin, anti-pentagastrin or anticaerulin. The cells containing the substance immunoreactive to mammalian anti-insulin, can be restained with paraldehyde-fuchsin.I thank Prof. A.G.E. Pearse for the opportunity to carry out this work in the Department of Histochemistry, Royal Postgraduate Medical School, London, England. The work was carried out with the aid of a grant from the Studienstiftung des Deutschen Volkes e.V., Germany (FRG).Dedicated to Prof. Dr. Drs. h.c. W. Bargmann at his 70th birthday.     

The distribution of endocrine cells along the mouse small intestine

The topographical distribution and incidence of endocrine cells in the crypt and villus epithelium and along the length of the mouse intestine was studied. Cells containing somatostatin and bombesin like reactivity were stained by immunocytochemical techniques using polyclonal antiserum. Most of the somatostatin cells were found in the duodenum, jejunum and ileum, and these cells were generally more frequent on the villus compared to the crypts. This may indicate that the somatostatin cells develop late in the endocrine cell lineage. Bombesin like cells were rare in occurence, and were only present in measureable numbers in the ileum, where they were observed in the crypt and villi. The application of ELISA assays to determine the specificity of the antisera for these peptides is also discussed.     

Responses of the PAS-positive pars intermedia cells in the cichlid fish Sarotherodon mossambicus to ambient calcium and background adaptation

Summary The function of the PAS-positive pars intermedia cells in fish has been connected with control of background adaptation and of plasma calcium levels. Since background reflectivity and illumination influence calcium metabolism in S. mossambicus, we have tested the hypothesis that the effects of background reflectivity on the PAS-positive cells are mediated by changes in plasma calcium. However, total plasma calcium does not correlate with the activity of the PAS-positive cells as estimated by morphometrical criteria. Transfer of S. mossambicus to a white background leads to a drop in plasma calcium, and a marked reduction of the activity of the PAS-positive cells. Adaptation to low-calcium freshwater, on a neutral background, has the same effect on plasma calcium but has no effect on the PAS-positive cells. The characteristic structural features of highly active PAS-positive cells in fish from a black background are not due to the slight hypocalcemia that occurs in these fish, since addition of calcium to the water in concentrations that fully prevent the drop in plasma calcium does not suppress the PAS-positive cells. These findings make it very unlikely that these cells produce a hypercalcemie factor in S. mossambicus.     

The distribution of endocrine cells along the mouse intestine: A quantitative immunocytochemical study

The topographical distribution of endocrine cells in the crypt and villus epithelium along the length of the mouse intestine was studied. Argyrophil reactivity using the Grimelius stain was used to estimate the total endocrine population of the intestine. Comparisons were then made with the fraction of endocrine cells containing glucagon like material, stained immunocytochemically using rabbit anti-glucagon antisera. A highly significant reduction in the incidence of endocrine cells (argyrophil reactive) from the proximal to distal end of the intestine was noted. However, only 10-30% of these cells contained glucagon like material in the crypts of the duodenum, jejunum and ileum, compared to 30–60% in the crypts of the colon and rectum. The distribution of endocrine cells (argyrophil reactive) was maximal in the lower regions of the proliferative zone of the crypts but showed no significant variation along the length of the villi. Cells containing glucagon like material were also most frequent in the lower regions of the proliferative zone of the crypts, but were not generally found above the botom third of the villi. Each crypt in the small intestine contains between 3 and 5 endocrine cells one of which contained glucagon like immunoreactive material. In the colon and rectum each crypt contains about 6-8 endocrine cells, of which 3–4 contained glucagon like immunoreactive material. These results indicate that a sub-set of cells containing glucagon like material, differentiate early in the lineage of endocrine cells within the proliferative zone of the intestinal crypts.     

Spatial and temporal variations in densities of small fishes across different temporary floodplain types of the lower Okavango Delta,Botswana

Small-sized and juvenile fishes as well as physicochemical water parameters in various primary, secondary and rarely flooded temporary floodplains of the Okavango Delta were assessed during the different hydrological phases of the 2009–2010 flooding season. Small fishes were sampled in the marginal zone of the floodplains using a throw-trap net and a suite of physicochemical properties were measured. Both physicochemical water quality parameters and densities of small fishes showed spatiotemporal variations across the temporary floodplain types. Turbidity, dissolved oxygen, conductivity, woody debris and chlorophyll a were all highest in rarely flooded floodplains compared to both primary and secondary floodplains (ANOVA, p < 0.05). Fish from 38 fish taxa belonging to 11 families were identified and classified during the study. The fish families Cichlidae (dominated by tilapias), Poeciliidae (Aplocheilichthys spp.) and Cyprinidae (Barbus spp.), were the most abundant across the study floodplains. The poeciliids were most abundant in frequently flooded primary and secondary floodplains, whereas juvenile cichlids dominated in rarely flooded floodplains. During high floods the rarely flooded portions of the delta function as important nursery habitats for juvenile cichlids, implying that a significant reduction in flooding may have negative effects on the delta's tilapia stocks due to reduced recruitment success.     

An histological and immunocytochemical study of the neuroendocrine cells in the intestine of Podarcis hispanica Steindachner, 1870 (Lacertidae)

Summary Numerous endocrine cells can be observed in the gut of the lizard Podarcis hispanica after application of the Grimelius silver nitrate technique. The argyrophilic endocrine cells are usually tall and thin in the small intestine but short, basal, and round in the large intestine. Eleven types of immunoreactive endocrine cells have been identified by immunocytochemical methods. Numerous serotonin-, caerulein/gastrin/cholecystokinin octapeptide-and peptide tyrosine-tyrosine-immunoreactive cells; a moderate number of pancreatic polypeptide-, neurotensin-, somatostatin-, glucagon-like peptide-1-and glucagon-immunoreactive cells, and few cholecystokinin N-terminal-and bombesin-immunoreactive cells were found in the epithelium of the small intestine. Coexistence of glucagon with GLP-1 or PP/PYY has been observed in some cells. In the large intestine a small number of serotonin-, peptide tyrosine-tyrosine-, pancreatic polypeptide-, neurotensin-, somatostatin-and glucagon-like peptide-1-immunoreactive cells were detected. Vasoactive intestinal peptide immunoreactivity was found in nerve fibers of the muscular layer. Substance P-immunoreactive nerve fibers were detected in lamina propria, submucosa and muscular layer. Chromogranin A-immunoreactive cells were observed throughout the intestine, although in lower numbers than argyrophilic cells.     

The effect of water acidification on prolactin cells and pars intermedia PAS-positive cells in the teleost fish Oreochromis (formerly Sarotherodon) mossambicus and Carassius auratus

Summary Although exposure to acid water (pH 3.5) induces severe and prolonged reduction in plasma osmolarity and total plasma calcium concentration in tilapia (Oreochromis mossambicus) and goldfish (Carassius auratus), the responses of the hypophyseal cells are clearly different. In tilapia, the size of the rostral pars distalis of the pituitary gland is enlarged as a result of the increase in size and number of prolactin cells. The pars intermedia PAS-positive (PIPAS) cells are not noticeably changed. Conversely, in goldfish, prolactin cells are unaffected, whereas the number of enlarged PIPAS cells increases markedly. Stimulation of prolactin secretion may be responsible for the partial restoration of plasma osmolarity and calcium levels observed in tilapia after two weeks exposure to acid water. Prolactin cells apparently play a role in the adaptation to acid stress by counteracting osmoregulatory disturbances. Goldfish show no restoration of plasma osmolarity during the course of the experiment. Plasma calcium levels tend to increase. Although prolactin may have an osmoregulatory function in goldfish under steady state conditions, goldfish prolactin cells do not seem to participate in the physiological adaptation to environmental changes that disturb water and ion homeostasis. The function of PIPAS cells in tilapia remains unclear and is apparently unconnected with ion regulation. The observations on these cells in goldfish are consistent with the hypercalcemic activity suggested for them.     

Character- and tree-based delimitation of species in the 'Cichlasoma' facetum group (Teleostei, Cichlidae) with the description of a new genus

The 'Cichlasoma' facetum group is part of the taxonomically complex group of Neotropical cichlid fishes of the tribe Heroini. Many species groups and unplaced species of heroines are still left without a generic name following the revision of the genus Cichlasoma . We describe here the 'Cichlasoma' facetum group as a new genus, Australoheros , and provide evidence for its monophyly based on phylogenetic analyses of morphological and mtDNA characters. Australoheros is morphologically characterized by the lowest values in meristic characters among heroines and by three apomorphic characters in coloration pattern. In addition to the three described species of Australoheros , our results of species delimitation based on a combination of tree- and character-based approaches identify seven putatively new species of Australoheros . Several coding schemes of morphological characters are used to recover the intrageneric relationships within the genus, resulting in very similar topologies. Discovery of additional species within the genus is expected once material from the whole distribution area is studied.     

Trichinella spiralis: the influence of short chain fatty acids on the proliferation of lymphocytes, the goblet cell count and apoptosis in the mouse intestine

This study was carried out to determine the influence of short chain fatty acids (SCFA) on spleen and mesenteric lymph node lymphocyte proliferation, goblet cells and apoptosis in the mouse small intestine during invasion by Trichinella spiralis. BALB/c mice were infected with 250 larvae of T. spiralis. An SCFA water solution containing acetic, propionic and butyric acids (30:15:20 mM) was administered orally starting 5 days before infection and ending 20 days post infection (dpi). Fragments of the jejunum were collected by dissection 7 and 10 dpi, and were examined for apoptotic cells in the lamina propria of the intestinal mucosa, and for goblet cells. The proliferation index of the cultured spleen and mesenteric lymph node lymphocytes with MTT test was also determined. The orally administered SCFA solution decreased the proliferation of mesenteric lymph node lymphocytes in the mice infected with T. spiralis at both examination times, but did not influence the proliferative activity of the spleen cells. Seven dpi, both in the spleen and mesenteric lymph nodes, the highest proliferation index of concanavalin A (Con A)-stimulated lymphocytes was found in the group of uninfected animals receiving SCFA animals. This tendency could still be seen 10 dpi in the mesenteric lymph nodes but not in the spleen, where the proliferation index in this group had significantly decreased. In vitro studies revealed, that butyric and propionic acids added to the cell cultures suppressed the proliferation of Con A-stimulated mesenteric lymph nodes and spleen lymphocytes taken from uninfected and T. spiralis-infected mice. Acetic acid stimulated proliferation of splenocytes taken from uninfected mice but did not affect lymphocyte proliferation in mesenteric lymph nodes from uninfected or infected mice. Orally administered SCFA increased the number of goblet cells found in the epithelium of the jejunum 7 dpi, but this number had decreased 10 dpi. The number of apoptotic cells in the lamina propria of the intestinal mucosa of animals infected with the T. spiralis and receiving SCFA was also lower, particularly 10 dpi. The above results show that SCFA can participate in the immune response during the course of trichinellosis in mice.     

Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): A fish living on the edge

Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9 + 2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.