MORPHOGENESIS OF THE WALL OF GLANDULAR PART OF THE STOMACH IN CHICKENS DURING POSTNATAL PERIOD OF ONTOGENESIS

Knowledge about the morphological features of the structure and functions of the digestive organs provide the basis for rational and effective use of feed, prevention and treatment of gastrointestinal diseases in poultry. In this regard, the study of the morphogenesis of the digestive system in birds and the mechanisms of their regulation is of great importance. The object of the study was the glandular part of the stomach (proventriculus) in chickens of Shaver 579 strain. The material for macro- and microscopic examinations was selected from birds at age of 1, 30, 60, 90, 120, 150, 180, 210, 240, 270, and 300 days and 1, 2, and 3 years; it was fixed in a 10% neutral formalin solution and embedded into paraffin according to conventional methods. For submicroscopic examinations, the material was selected from hens of this strain at age of 180 days. The structure of epitheliocytes in the superficial epithelium and secretory cells of the deep glands was studied in ultrathin sections. Digital indicators of research results were statistically processed by a personal computer using Microsoft Excel program. The glandular stomach in chickens is a direct extension of the esophagus and has the form of a thick-walled tube, the wall of which is formed by mucous, muscular, and serous membranes. The superficial epithelium of the mucosa is represented by cylindrical epithelial cells that are located within the basal membrane. They are linked to each other by different types of contacts and have a well-defined polar differentiation. The lobules of the deep glands are formed by cells with well-developed synthesizing organelles and secretory granules. The morphogenesis of the glandular part of the stomach in chickens according to age aspect is manifested by changes in morphometric parameters of the thickness and the area of the membranes of its wall. The wall thickness increases (between the folds 4223.23 ± 189.25 and in the area of the folds 5561.32 ± 45.01 μm) unevenly in chickens up to age of 240 days. The most developed membrane of the wall of the glandular stomach is the mucosa. Its area increases (by 82.14 ± 0.56%) in chickens up to age of 180 days, and area of muscular and serous membranes decreases (by 15.54 ± 0.65 and 2.32 ± 0.33%, respectively). In older birds, the thickness of the wall and the area of the membranes of the glandular stomach do not change significantly.

Mouse Spexin: (III) Differential Regulation by Glucose and Insulin in Glandular Stomach and Functional Implication in Feeding Control

Spexin (SPX), a neuropeptide with diverse functions, is a novel satiety factor in fish models and its role in feeding control has been recently confirmed in mammals. In mouse, food intake was shown to trigger SPX expression in glandular stomach with parallel rise in serum SPX and these SPX signals could inhibit feeding via central actions within the hypothalamus. However, the mechanisms for SPX regulation by food intake are still unclear. To examine the role of insulin signal caused by glucose uptake in SPX regulation, the mice were IP injected with glucose and insulin, respectively. In this case, serum SPX was elevated by glucose but not altered by insulin. Meanwhile, SPX transcript expression in the glandular stomach was up-regulated by glucose but the opposite was true for insulin treatment. Using in situ hybridization, the differential effects on SPX gene expression were located in the gastric mucosa of glandular stomach. Co-injection experiments also revealed that glucose stimulation on serum SPX and SPX mRNA expressed in glandular stomach could be blocked by insulin. In gastric mucosal cells prepared from glandular stomach, the opposite effects on SPX transcript expression by glucose and insulin could still be noted with similar blockade of the stimulatory effects of glucose by insulin. In this cell model, SPX gene expression induced by glucose was mediated by glucose uptake via GLUT, ATP synthesis by glycolysis/respiratory chain, and subsequent modulation of KATP channel activity, but the voltage-sensitive Ca2+ channels were not involved. The corresponding inhibition by insulin, however, was mediated by PI3K/Akt, MEK1/2/ERK1/2, and P38MAPK cascades coupled to insulin receptor but not IGF-1 receptor. Apparently, glucose uptake in mice can induce SPX expression in the glandular stomach through ATP synthesis via glucose metabolism and subsequent modification of KATP channel activity, which may contribute to SPX release into circulation to act as the satiety signal after food intake. The insulin rise caused by glucose uptake, presumably originated from the pancreas, may serve as a negative feedback to inhibit the SPX response by activating MAPK and PI3K/Akt pathways in the stomach.

Spexin as a Satiety Factor in Mouse via Regulatory Actions Within the Hypothalamus

Spexin (SPX) is a pleiotropic peptide with highly conserved protein sequence from fish to mammals and its biological actions are mediated by GalR2/GalR3 receptors expressed in target tissues. Recently, SPX was found to be a novel satiety factor in fish models but whether the peptide has a similar function in mammals is still unknown. Using the mouse as a model for mammalian species, the functional role of SPX in feeding control and the mechanisms involved were investigated. After food intake, serum SPX could be up-regulated in mice with parallel elevations of transcript expression and tissue content of SPX in the glandular stomach but not in other tissues examined. As revealed by immunostaining, food intake also intensified SPX signals in different cell types within the gastric mucosa of glandular stomach. Furthermore, IP injection of SPX was effective in reducing food consumption with parallel drops in transcript expression of NPY, AgRP, NPY type 5 receptor (NPY5R) and ghrelin receptor (GHSR) in the hypothalamus, and these inhibitory effects could be blocked by GalR3 but not GalR2 antagonism. In agreement with the central actions of SPX, similar inhibition on food intake and hypothalamic expression of NPY, AgRP, NPY5R and GHSR could be observed with ICV injection of SPX. In the same study, parallel rises of transcript expression of leptin receptor (LepR) and melanocortin 4 receptor (MC4R) were also observed in the hypothalamus. These findings, taken together, suggest that the role of SPX as a satiety factor is well-conserved in the mouse. Probably, food consumption can induce SPX production in glandular stomach and contribute to the postprandial rise of SPX in circulation. Through GalR3 activation, this SPX signal can act within the hypothalamus to trigger feedback inhibition on food intake by differential modulation of the feeding regulators (NPY & AgRP) and their receptors (NPY5R, GHSR, LepR & MC4R) involved in the feeding circuitry of the brain.

Analysis of proportion of nucleic acids and proteins in glandular stomach wall in chickens during experimental escherichiosis

A method for spectral analysis of the ratios of organic substances in a cell using the "Stains all" metachromatic luminescent dye (in its own modification) has been developed. This method is used to establish the ratio of nucleic acids and proteins in the integumentary epithelium of the mucous membrane and in the interlobular connective tissue of the submucosa tissue of the glandular stomach of chickens. Using the developed biophysical method, we studied the ratios of these organic substances in the glandular stomach of healthy and infected with E. coli chickens. The dynamics of the ratios of nucleic acids and proteins detected in the wall of the glandular stomach of the control group chicks fits into the picture of a moderate and uniform increase in the values of these indicators, corresponding to an age increase of the chickens. In chickens affected by Escherichiosis, a curve that reflects the dynamics of the ratios includes a three-fold increase in their values. The results obtained using the developed method indicate the possibility of using it to detect early metabolic changes in the glandular stomach of chickens before the appearance of a characteristic pathomorphological and clinical picture. Thus, this method can provide invaluable assistance in developing a fundamentally new approach in creation of modern technologies for the diagnosis, prevention and treatment of widespread disease Escherichiosis.