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At least 19 recordsLinked to original sources
PubMed1994

Mesenchymal regulation of epithelial gene expression in developing avian stomach: 5'-flanking region of pepsinogen gene can mediate mesenchymal influence on its expression.

The expression of a gene encoding an embryonic chick pepsinogen was investigated in developing avian gut. Expression is restricted to the epithelial layer of the embryonic proventriculus (glandular stomach). We can therefore regard this gene as a marker gene for proventricular epithelial differentiation. There is some considerable evidence in favour of epithelial-mesenchymal interactions being important during the development of the gastrointestinal system; for example, pepsinogen expression is induced in proventricular and gizzard (muscular stomach) epithelial by the proventricular mesenchyme but is suppressed by the gizzard mesenchyme. In the present paper, we studied how the mesenchymes influence this gene expression pattern. For this we produced constructs containing various portions of the 5'-flanking region of the embryonic chick pepsinogen gene, driving reporter sequences (beta-galactocidase or luciferase), and these constructs were transfected into dissociated epithelial cells either from the proventriculus or gizzard. We then recombined these cells with mesenchymal cells and cultured them as cell aggregates. In this way, we were able to dissect the timing and other requirements of the epithelial-mesenchymal interactions for expression of embryonic chick pepsinogen gene. We also report that 1.1 kb of 5'-flanking sequence is sufficient to drive correct expression of embryonic chick pepsinogen gene, although further enhancement was seen if the constructs contained 3.2 kb of upstream sequence.

Animals↗
PubMed1983

[Histochemical characteristics of the epitheliocytes of the avian glandular stomach].

A complex histochemical investigation has been undertaken to study the epithelial lining of the glandular stomach in birds having various types of nutrition. The protective barrier of the avian stomach has been found to be characterized as a resistant (mucosal) barrier, with neutral glycoproteins, sialo- and sulphoglycoproteins as its components. Differences in histochemical properties of the epitheliocyte secretion have been described in birds with different types of nutrition. They are connected with various correlation of carbohydrates and proteins in the composition of the micromolecular glycoprotein complex. The data obtained are compared with those concerning the histochemical properties of the stomach in amphibia and reptiles which have the mucous membrane structure similar to that in the avian stomach.

Animals↗
PubMed1977

[Histochemical characteristics of the epithelial secretions of the avian muscular stomach].

The work was devoted to a histochemical studying of the covering lamina and other epithelial secretions of the avian muscular stomach. It has been shown that in its histochemical properties the secreted mucin is similar to mucous secretions of the enterodermal lining of the mammalian stomach and contains neutral polysaccharides, sulfo- and slilosaccharides. The protein component is represented by aminoacid residues of lysin, cystine, cystein. Formation of the mechanically firm structure--lamina is based on the substances of carbohydrate--protein nature secreted by the epithelial lining of the stomach.

Amino Acids↗
PubMed2001

Gizzard formation and the role of Bapx1.

The anterior-posterior gut pattern is formed from three broad domains: fore-, mid-, and hindgut that have distinct functional, morphological, and molecular boundaries. The stomach demarcates the posterior boundary of the foregut. Avian stomachs are composed of two chambers: the anterior chamber (proventriculus) and the thick muscular posterior chamber (gizzard). Expression of candidate pattern formation control factors are restricted in the chick stomach regions such that Bmp4 and Wnt5a are not expressed in the gizzard. We previously implicated Bmp4 as controlling growth and differentiation of the gut musculature. Bmp4 is not expressed in the developing gizzard but is expressed in the rest of the gut including the adjacent proventriculus and midgut. Bapx1 (Nkx3.2) is expressed in the gizzard musculature but not in the proventriculus or midgut. We show ectopic expression of Bapx1 in the proventriculus results in a gizzard-like morphology and inhibits the normal proventricular expression of Bmp4 and Wnt5a. Overexpression of a reverse-function Bapx1 construct can result in a small stomach and ectopic extension of Bmp4 and Wnt5a expression into the gizzard. We suggest the role of Bapx1 is to regulate the expression of Bmp4 and Wnt5a to pattern the avian stomach.

Animals↗
PubMed1979

Comparative cytology of hydrochloric acid secreting cells.

A comparative study of the oxyntic cells of the stomach of Vertebrates is presented. A system of membranous tubules which is apparently inter-convertible with the luminal plasma membrane is described as an important structural feature in all classes. In all Vertebrates with the sole exception of Mammals, this system shares a common cell with the structures involved in the secretion of zymogen. In Mammals it becomes segregated into a specialized cell type, the parietal cell, characterized in addition by the presence of a long tortuous intracellular canaliculus, which serves as its secretory pole. The hypothesis is presented and discussed that the parietal cell is capable of achieving a higher efficiency in hydrochloric acid secretion by the existence of the intracellular canaliculus which makes the immediate surroundings of the secretory pole independent of the contents of the gastic lumen. In Birds (whose gastric glands do not possess parietal cells) a corresponding effect can be achieved only by complex structures such as the compound gastric glands. An explanation is hereby offered for the unique features of the Avian stomach.

Amphibians↗
PubMed1992

Development and birthdates of vasoactive intestinal peptide immunoreactive neurons in the chick proventriculus.

To gain insight into the mechanisms regulating expression of transmitter phenotypes in the enteric nervous system, we have studied the development and birthdate of vasoactive intestinal peptide immunoreactive (VIP-IR) myenteric neurons in the chicken proventriculus (secretory portion of the avian stomach) by a combination of immunocytochemistry and radioautography. The appearance and numbers of VIP-IR neurons in whole mounts of the myenteric plexus from chick embryos and chickens were examined. We found that VIP-IR neurons first appeared at embryonic day (E) 5.5-6.5 in the distal part of the proventriculus. At E7.5, VIP-IR neurons were found singly, in pairs, or in small groups, which together with unlabeled cells formed primitive myenteric ganglia. VIP-IR fibers were found within the developing fiber tracts which connected the ganglia. The number of VIP-IR neurons was found to be maximum in the E15.5 embryo and to decline to 68% of maximum in the 4 week old chicken. Birthdate studies were performed by application of either single pulses or cumulative doses of [3H]-thymidine to embryos between E3 and E14. Whole mounts of the myenteric plexus from the proventriculus of these embryos were immunostained for VIP at E10 or E17. The whole mounts were subsequently sectioned and processed for radioautography. We found that VIP-IR myenteric neurons were born between E3 and E10 with a peak at E7. Most cells underwent terminal division between E5 and E9. These data will be useful in determining the time and conditions when cells make decisions about transmitter phenotypes.

Aging↗
PubMed1981

Intranuclear filamentous inclusions in the gastro-entero-pancreatic (GEP) endocrine cells of birds.

Intranuclear filamentous inclusions were found in the normal endocrine cells of the avian stomach and pancreas. These inclusions were composed of a bundle of closely packed filaments (6-8 nm in diameter), being ultrastructurally similar to those found in the nucleus of various neurons. Most of them appeared as single rod- or spindle-shaped bodies; aggregations of two or more inclusions were rarely seen within a single nucleus. Cells with an intranuclear inclusion often contained a cytoplasmic fibrillar bundle similar to the intranuclear inclusion.

Animals↗
PubMed2006

Changes in ghrelin levels of plasma and proventriculus and ghrelin mRNA of proventriculus in fasted and refed layer chicks.

This is a test-report of ghrelin levels in plasma and proventriculus, the glandular portion of the avian stomach, by using a specific radioimmunoassay for acylated ghrelin, as well as the expression of the ghrelin gene in the proventriculus after a 12-h fasting period followed by a 6-h feeding period with 6-day-old layer chicks. After fasting, the plasma ghrelin levels increased from 21.3+/-4.5 to 32.9+/-5.0 fmol/ml, but once refed it returned to the control value. After fasting, the ghrelin mRNA and the peptide levels in the proventriculus increased, and ghrelin mRNA levels remained high but once refed the ghrelin content returned to the control level. Furthermore, in order to examine the effect of increased circulating ghrelin on food intake, a bolus intravenous injection of 500 pmol of chicken ghrelin was given to 8-day-old chicks. The ghrelin injection did not cause any significant changes in food intake. These results indicate that the levels of ghrelin and its mRNA with layer chicks are altered according to the feeding state and this in a similar manner as has been observed in mammals. Unlike in mammals, an increase in circulating ghrelin does not cause the promotion of food intake in chicks.

Analysis of Variance↗
PubMed1991

Hormonal control of avian pancreas by gastrin-releasing peptide from the proventriculus.

Endocrine cells in the acid-secreting part of the avian stomach, the proventriculus, contain two forms of gastrin-releasing peptide (GRP) of 27 and 6 residues, respectively. We have examined the actions of exogenous GRP-27 and GRP-6 and endogenously released GRP in the control of pancreatic secretion in urethan-anesthetized turkeys. Chicken GRP-27 and the structurally related amphibian peptide bombesin were potent stimulants of fluid and protein output from the pancreas (at 6-100 pmol/kg, iv). GRP-6 had no significant effect at doses up to 1,000 times higher. A bombesin antagonist, (CH3)2-CHCO-[D-Ala24]GRP-20--26-NHCH3, inhibited the action of exogenous chicken GRP-27 but did not inhibit intravenous cholecystokinin octapeptide (CCK-8). Distension of the proventriculus with a solution of peptone produced an increase in the flow of pancreatic juice and an increase in protein output, which was not reduced by atropine. The bombesin antagonist produced a reversible inhibition of this response. A CCK-gastrin antagonist, BOC-beta-Ala-Trp-Leu-Asp-O(CH2)2- phenyl(4F), which inhibited the action of exogenous CCK, had no effect on the pancreatic response to exogenous GRP-27 or to distension of the proventriculus with peptone. We suggest that protein-rich solutions in the proventriculus release GRP, which in turn acts directly on the pancreas to stimulate enzyme secretion.

Amino Acid Sequence↗
PubMed1985

Generation of xenopsin-related peptides during acid extraction of gastric tissues.

Biologically active xenopsin-related peptide(s) were shown by radioimmunoassay to be liberated in nearly micromolar concentrations from substrate(s) with Mr greater than 70,000 during acid extraction of mammalian and avian stomach. The reaction displayed an enzyme-like temperature sensitivity, had a pH optimum of 2, and was fully inhibited in the presence of pepstatin A. Treatment of a stabilized gastric substrate with hog pepsin was found to mimic the reaction, producing immunoreactive xenopsin(s) which behaved similarly during high pressure liquid chromatography. Although some of the generated immunoreactivity co-chromatographed with xenopsin, it differed immunochemically when examined with a battery of region-specific antisera. Highly purified rat gastric immunoreactive xenopsin displayed xenopsin-like biologic effects, producing hypotension in the anesthetized rat and contracting the isolated guinea pig ileum. These findings suggest that there may be a renin/angiotensin-like system for the generation of xenopsin-related peptides in the stomach.

Amino Acid Sequence↗
PubMedDate not supplied

Evolutionary relationships between the amphibian, avian, and mammalian stomachs.

Although the gut is homologous among different vertebrates, morphological differences exist between different species. The most obvious variation in the guts of extant vertebrates appears in the stomach. To investigate the evolution of this structure, we compared the histology of the stomach and gastrointestinal tract in amphibian (Xenopus laevis), avian (Gallus gallus), and mammalian (Mus musculus) organisms, and defined the expression patterns of several genes within the developing guts of these lineages. In all three groups, we find that the anterior portion of the stomach has a similar glandular histology as well as a common embryonic expression of the secreted factors Wnt5a and BMP-4. Likewise, within the amniote lineages, the posterior nonglandular stomach and pyloric sphincter regions are also comparable in both histological and molecular phenotypes. The posterior stomach expresses Six2, BMPR1B, and Barx1, whereas the pyloric sphincter expresses Nkx2.5. Although the adult Xenopus stomach exhibits both glandular and aglandular regions and a distinct pyloric sphincter similar to that of the amniotic vertebrates, the histology of the Xenopus tadpole gut shows less distinct variation in differentiation in this region, which is most likely a derived condition. The molecular signature of the embryonic Xenopus gut correlates with the more derived morphology of the larval phase. We conclude that the global patterning of the gut is remarkably similar among the different vertebrate lineages. The distinct compartments of gene expression that we find in the gut be necessary for the unique morphological specializations that distinguish the stomachs from terrestrial vertebrates.

Animals↗
PubMedDate not supplied

Traumatic ventriculitis in chickens.

Nine cases of traumatic ventriculitis in chickens, with associated complications, are reported. The findings suggest that chickens with traumatic ventriculitis may die either from extreme emaciation or from toxemia.

Animals↗