Differentiation Of Gastric Glands Research Articles

Individual variation in post-metamorphic changes in feeding incidence, digestive organ tissues and enzyme gene expression in Japanese eel Anguilla japonica glass eels

Temporal changes of feeding incidences, digestive organ tissues, and mRNA expression of digestive enzymes were investigated in artificially reared Anguilla japonica glass eels. Incidences of daily feeding and cumulative first feeding exceeded 50% at day 40 and 33, respectively, but tended to increase gradually. Time until first feeding varied from day 11–61 among individuals. Glass eels without food after metamorphosis showed notable developmental changes in their digestive system that included increases in esophagus goblet cells and blood vessel diameters, elongation of the stomach, differentiation and increased number of gastric glands, and increases in gall bladder sizes. A distinct qualitative change, which was gastric gland differentiation, occurred in all eels until week 2 after metamorphosis. All quantitative character values showed trends of gradual changes in their averages and had high coefficients of variation, especially for goblet cell numbers. Few deaths and no histological features related to severe starvation such as notably more hepatocyte necrosis or desquamation of intestinal epithelial cells were observed even after 9 weeks. Hepatocyte-vacuole stored glycogens and pancreatic zymogen granules were also found, suggesting that they were not expressing symptoms of starvation. Relative expressions of five digestive enzymes were lowest at week 0 and increased gradually in their averages with the passage of weeks, along with large variations among fish. This study found that half of the post-metamorphic glass eels began feeding after 4 weeks, but that there were large individual variations in the timing of feeding onset, the degree of developmental of their digestive organs, and in digestive enzyme expressions.

Disruption of the Tff1 gene in mice using CRISPR/Cas9 promotes body weight reduction and gastric tumorigenesis

Trefoil factor 1 (TFF1, also known as pS2) is strongly expressed in the gastrointestinal mucosa and plays a critical role in the differentiation of gastric glands. Since approximately 50% of all human gastric cancers are associated with decreased TFF1 expression, it is considered a tumor suppressor gene. Tff1 deficiency in mice results in histological changes in the antral and pyloric gastric mucosa, with severe hyperplasia and dysplasia of epithelial cells, resulting in the development of antropyloric adenoma. Here, we generated Tff1-knockout (KO) mice, without a neomycin resistant (NeoR) cassette, using the clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9 (CRSIPR/Cas9) system. Though our Tff1-KO mice showed phenotypes very similar to the previous embryonic stem (ES)-cell-based KO mice, they differed from the previous reports in that a reduction in body weight was observed in males. These results demonstrate that these newly established Tff1-KO mice are useful tools for investigating genetic and environmental factors influencing gastric cancer, without the effects of artificial gene insertion. Furthermore, these findings suggest a novel hypothesis that Tff1 expression influences gender differences.

Histological Aspects of the Early Development of the Digestive System of Burbot Lota lota L. (Lotidae, Gadiformes).

The ontogeny of the digestive tract was studied histologically in burbot, Lota lota L., from hatching to 42 days post-hatch (dph). At hatching, the digestive tract consisted of a straight tube with discernible digestive accessory glands (the liver and the pancreas) dorsally attached to the yolk sac. Most of the yolk sac reserves were consumed during the first 12 days and were completely depleted by 17 dph. The first PAS-positive goblet cells appeared at 6 dph, dispersed within the epithelium of the oesophagus and increasing substantially in number and distribution as development progressed. At 12 dph, the first vacuoles (neutral lipids) appeared in the intestine, indicating the functional absorption of nutrients from food. Differentiation of gastric glands was first noticed at 17 dph and was extensive by 27 dph. L. lota larvae have a morphologically complete digestive tract by 32 dph. These findings on the development of the digestive system in L. lota may contribute to a better understanding of its ontogeny and can be useful for improvement of the larval rearing techniques of this promising species for freshwater aquaculture diversification.

Ontogeny and functional histochemistry of the digestive and visual systems and other organs during the larval development of the thick-lipped grey mullet, <em>Chelon labrosus</em>

The main ontogenetic and functional changes of the digestive and visual systems of Chelon labrosus during the first three months from fertilization until 99 days post-hatch (dph) are described. An extended slow growth pattern (3.93%) during the first three weeks of larval life was discernible. A long transitional period of mixed endo-exogenous feeding was noticeable until 13 dph. The majority of organ systems and structures (eye, digestive system, liver, pancreas, thyroid and others) were developed and functional before first feeding (mouth opening at 4 dph). First differentiation of gastric glands was detected at 16 dph, with the appearance of a noticeable pyloric muscular portion or typical gizzard and first developed pyloric caeca from 23 dph. The presence of pinocytotic supranuclear vesicles (5 dph) was still visible in the posterior intestine until the third month of life. The eyes exhibited early differentiation and functionality (pigmentation, first cone-type photoreceptors) during the lecithotrophic phase (2 dph), and development of all typical retinal layers containing different retinal cell types was progressively discernible from 16 dph onwards. From this time, rod photoreceptor precursor cells were incorporated into the basal region of the outer nuclear layer, and increases of two types of photoreceptors (cones and rods) were detected from 23 dph.

Ontogeny of the digestive tract in butter catfish Ompok bimaculatus (Bloch) larvae

The ontogeny of the digestive tract was studied histologically in butter catfish Ompok bimaculatus from hatching to 30 days post-hatching (dph). At hatching, the digestive tract of butter catfish consisted of a straight tube with a smooth lumen dorsally attached to the yolk sac. Between 1 and 2 dph, the mouth opened, oral valves were visible and canine-like teeth and taste buds were detected. During this period, intestine was differentiated into the anterior and posterior intestine, and the digestive accessory glands were also developed. Exogenous feeding started at 2 dph, and there was a 2-day mixed endogenous-exogenous feeding period. Most of the yolk sac reserves were consumed between 2 and 3 dph, and by 5 dph, the yolk sac was completely depleted and no longer visible in histological sections. Between 3 and 4 dph, several vacuoles (neutral lipids) were observed in the intestine and also in hepatocytes, indicating a functional absorption of nutrients from food. At 8 dph, differentiation of gastric glands was noticed, and by 9-11 dph, there were abundant gastric tubular glands arranged along numerous longitudinal folds. During the same period, pyloric sphincter appeared as an epithelial fold that separated the stomach from the anterior intestine. From 12 dph to the end of the study at 30 dph, no noticeable histological modifications were observed. The development of gastric glands is considered as the last major events in digestive tract development and their presence designates the end of larval period and the onset of the juvenile period. Hence, it is suggested that, butter catfish larvae have a morphologically complete digestive tract by 12 dph. These findings on the development of the digestive system in butter catfish may lead to a better understanding of the ontogeny and would be useful to improve the larval rearing techniques of this promising catfish species for freshwater aquaculture diversification.

A morphohistological and histochemical study of hatchery-reared European hake, <i>Merluccius merluccius</i> (Linnaeus, 1758), during the lecitho-exotrophic larval phase

The larval development of reared European hake, Merluccius merluccius (Linnaeus, 1758), during the lecithotrophic phase, from hatching until 5 days post-hatching (dph), and throughout the endo-exotrophic feeding phase (6-10 dph) was studied by histology and histochemistry. Many crucial morphological, cellular and tissular changes were observed during both feeding phases, mostly those related to digestive and visual ontogenetic events, such as differentiation of buccopharyngeal cavity and eye development (at hatching); pigmentation and differentiation of cone-photoreceptors (4 dph); opening of the mouth and anus, appearance of intestinal valves (5-6 dph); presence of buccopharyngo-esophageal (5-6 dph) and intestinal (9 dph) mucous cells; folding of intestinal mucosa (6 dph); development of regional specific digestive musculature (6 dph); typical structure and functionality of the liver (sinusoids, biliary and pancreatic ducts, glycogen, protein and lipid reserves) (4-6 dph); and characteristic acinar distribution pattern of eosinophilic zymogen granules of the exocrine pancreas (6 dph). Between 9 and 10 dph, the hake larvae showed evident signs of lipid absorption within enterocytes of the anterior intestinal region and a remarkable process of pynocitosis and intracellular digestion was detected in the posterior intestine (supranuclear inclusions or acidophilic protein vesicles). In hake larvae at 10 dph, a proliferation of renal tubules, spleen differentiation and gill development, as well as the presence of the first thyroid follicle, were clearly distinguished. At this time, stomach gastric gland differentiation was not detected and endocrine pancreas and gill lamellae were not evidenced. However, and interestingly, swim bladder and eyes (developing rods) were well differentiated in larval development from 9 dph onwards. In summary, in European hake larval development during the endo-exogenous feeding phase and especially at 9 to 10 dph, most systems, organs and tissues were well differentiated. Particularly, digestive and visual systems were developed and physiologically functional some days before the start of the exogenous feeding phase.

Effects of weaning age and diets on ontogeny of digestive activities and structures of pikeperch (Sander lucioperca) larvae

Growth and ontogeny of digestive function were studied in pikeperch (Sander lucioperca) larvae weaned on artificial food at different ages. Three weaning treatments initiated respectively on day 9 (W9), day 15 (W15) or day 21 (W21) post-hatching (p.h.) were compared with a control group, fed Artemia nauplii from first feeding until the end of the rearing trial on day 36 p.h. The digestive enzyme activities and the ontogeny of digestive structures were investigated using enzymatic assays and histological methods. Growth of pikeperch larvae was significantly affected by precocious weaning. Pancreatic (trypsin and amylase) and intestinal (leucine-alanine peptidase, leucine aminopeptidase N and alkaline phosphatase) enzyme activities were detected from hatching onwards, increased at the moment of first feeding and then decreased. Pepsin secretion occurred at day 29 p. h. only, concurrently with the stomach development and differentiation of gastric glands. In the early weaning group (W9) the maturation process of intestinal enterocytes seems to be impaired and/or delayed and several signs of malnutrition were recorded. Except for alkaline phosphatase activity, no differences in enzyme activities and development of digestive structures were observed among the control, W21, and W15 groups. Moreover, at the end of the experiment, no differences in proteolytic activities were observed among larvae from the different treatments, indicating that, in surviving individuals, the digestive structures were properly developed and the larvae had acquired an adult mode of digestion. Based on the artificial diet used, our results suggested that pikeperch larvae can be weaned from day 15 p.h. without significant adverse effect on digestive capacities (except for alkaline phosphatase) or development of digestive tract, while earlier weaning impaired the onset of the maturation processes of the digestive system, both in terms of morphological structures and enzymatic activities.

Preliminary Observations on Development of Pacific Bluefin Tuna Thunnus thynnus (Scombridae) Larvae Reared in the Laboratory, with Special Reference to the Digestive System

Pacific bluefin tuna larvae (Thunnus thynnus) were experimentally reared from 2-day-old yolk-sac larvae through 30-day-old early juveniles in June and July 1994. The larvae initially fed on rotifers on Day 3 and Artemia nauplii, fish eggs and larvae around Day 13, and thereafter were fed Artemia larvae and an artificial diet. The larvae had transformed to the juvenile stage after 30 days. The primitive digestive system differentiated on Day 3. The gastric gland and pyloric caeca first appeared on Day 11 and 14, respectively. The pharyngeal and jaw teeth became fully functional with gastric gland differentiation. The number of gastric glands and pyloric caeca and volume of the gastric blind sac increased markedly with development to the juvenile stage. Although the external morphological development of the tuna resembles the pattern of many other marine fish larvae, the basic digestive system developed at an earlier larval stage; this precocity may relate to the early appearance of piscivory and the high growth potential of tuna larvae.