Chronic systemic treatment with epidermal growth factor in the rat increases the mucosal surface of the small intestine

We examined the effects of treatment with human recombinant epidermal growth factor (EGF) on the functioning small intestine in the rat. Male Wistar rats, 7–8 weeks old, were treated with EGF administered subcutaneously in doses of 0 (n = 7) or 150 μg/kg/day (n = 8) for 4 weeks. The histological composition and mucosal surface area of the perfusion-fixed small intestine was quantified with stereological principles. The length of the gut remained unchanged. The amount of tissue and surface area per length of gut (median (ranges)) were increased from 117 (101–131) mg/cm and 2.6 (2.1–3.5) cm²/cm in the controls to 146 (138–152) mg/cm and 3.5 (2.5–3.8) cm²/cm for the complete small intestine (both comparisons p < 0.02). The weight increase was due to mucosal growth in all parts of the intestine, whereas the surface area was only increased in proximal and middle parts. It is concluded that EGF treatment in rats increases the mucosal weight and surface area of the functioning small intestine.     

Comparative allometric growth of the gastrointestinal tract of two sympatric congeners, copper rockfish (Sebastes caurinus) and quillback rockfish (S. maliger)

Allometric growth of the stomach, intestine, and caeca was compared between two sympatric congeners, the copper rockfish ( Sebastes caurinus ) and the quillback rockfish ( S. maliger ), to examine the species-specific differences in their gut tract in relation to their general feeding habits. The intestine of copper rockfish was shorter and its mass less than the intestine of quillback rockfish. Copper rockfish also had a greater stomach mass and, on average, a greater number of pyloric caeca than quillback rockfish. The differences in the gut allometry between the species were consistent with differences in their general food habits as copper rockfish consume proportionally more fish and larger crustaceans than quillback rockfish.     

玛曲渔场几种裂腹鱼类消化道的形态结构与其食性的相互关系

本文对玛曲渔场几种裂腹鱼类消化道的大体形态及显微结构进行了观察与比较,并对其结构与食性的关系作了初步探讨,结果如下:(1)这几种裂腹鱼类消化道的大体形态同林浩然(1962)报道的鲤科鱼类者一致,但显微结构差异甚大。与Mohsin(1961)报道的G.giurus鱼的显微结构相似。(2)各种硬骨鱼类分泌粘液的细胞组成不同,这种组成与食性有关。食道上皮除复层鳞形上皮外,还有复层柱状上皮。食道肌层的纤维走向与肠部者相反。(3)鱼类消化道的形态结构与其食性一致,主要表现在口腔、咽、食道和肠的长短方面。肠的显微结构,几乎没有对特有食性的适应变化。       

Regulation of digestive performance: a proposed adaptive response

Among snakes a correlation exists between feeding habits (frequent or infrequent) and the magnitude by which digestive performance is regulated (modest or large). This paper investigates whether the observed regulation of digestive performance is an adaptation to feeding habits and therefore, a product of natural selection. Using data on metabolic and intestinal responses to feeding for amphibians and reptiles, it is attempted to show the selective advantage and independent origin of either modestly or widely regulating gut performance. In an energetic model, snakes that naturally feed frequently on small meals benefit (from lower energy output) from modestly regulating gut performance as opposed to widely regulating gut performance. Likewise, the model suggests an energetic benefit for infrequently-feeding snakes secondary to the wide regulation of gut performance. This benefit is a function of long spans of fasting with a down-regulated gut (thereby incurring a lower standard metabolic rate) and the occasionally incursion of a costly up-regulation of the gut. In a comparison across several distantly-related lineages of amphibians and reptiles, frequently-feeding species all exhibit small postprandial responses in metabolism and intestinal nutrient transport capacities. In contrast, frogs and snakes that routinely fast for long periods independently experience five- to 30-fold increases in metabolism and intestinal performance with feeding. Among amphibians and reptiles the evidence presented supports the hypothesis that the extent by which the gut is regulated is an adaptive trait that evolved with divergence in feeding habits and energy budgets. In finishing, the foundations, caveats, and suggested future tests of this adaptive hypothesis are presented.     

银鲳消化道形态与组织学结构特征及其消化酶活性

为了解银鲳(Pampus argenteus)消化道结构特点与其功能及食性的相关性, 采用解剖、石蜡切片、AB-PAS染色及酶活性检测技术对银鲳消化道的形态、组织结构、黏液细胞分布及消化酶活性进行研究。结果显示, 银鲳的消化道由口咽腔(舌)、食道侧囊、食道、胃及肠构成, 胃肠交界处有很多幽门盲囊。食道侧囊呈椭球形, 食道粗短, 胃呈U型, 肠有多个盘曲, 肠指数为2.03。舌上皮内有少量味蕾及较多黏液细胞。食道侧囊、食道、胃及肠均由黏膜层、黏膜下层、肌层及浆膜组成。食道侧囊内皱襞较发达, 被覆复层扁平上皮, 内含较多黏液细胞, 且以Ⅳ型为主, 皱襞顶端及侧面有内含角质刺的次级突起; 黏膜下层及肌层中有固定皱襞的骨质脚根; 侧囊内胃蛋白酶活性较高。食道内皱襞较高, 被覆复层扁平上皮, 内含较多黏液细胞, 且以Ⅳ型为主。胃内皱襞发达, 被覆单层柱状上皮, 未见黏液细胞分布; 胃腺发达, 胃内蛋白酶活性较高。肠道内褶襞多, 高度呈先下降后上升趋势, 黏液细胞密度前、中肠较高, 后肠较低, 且均以Ⅰ型为主; 肠道内胰蛋白酶、脂肪酶、淀粉酶及碱性磷酸酶活性较高。幽门盲囊组织结构与肠相似。银鲳的消化道结构特点、黏液细胞分布及消化酶活性与其功能及偏肉食的杂食性相适应。     

Morphometrics of the avian small intestine compared with that of nonflying mammals: a phylogenetic approach

Flying animals may experience a selective constraint on gut volume because the energetic cost of flight increases and maneuverability decreases with greater digesta load. The small intestine is the primary site of absorption of most nutrients (e.g., carbohydrates, proteins, fat) in both birds and mammals. Therefore, we used a phylogenetically informed approach to compare small intestine morphometric measurements of birds with those of nonflying mammals and to test for effects of diet within each clade. We also compared the fit of nonphylogenetic and phylogenetic models to test for phylogenetic signal after accounting for effects of body mass, clade, and/or diet. We provide a new MATLAB program (Regressionv2.m) that facilitates a flexible model-fitting approach in comparative studies. As compared with nonflying mammals, birds had 51% less nominal small intestine surface area (area of a smooth bore tube) and 32% less volume. For animals <365 g in body mass, birds also had significantly shorter small intestines (20%-33% shorter, depending on body mass). Diet was also a significant factor explaining variation in small intestine nominal surface area of both birds and nonflying mammals, small intestine mass of mammals, and small intestine volume of both birds and nonflying mammals. On the basis of the phylogenetic trees used in our analyses, small intestine length and nominal surface area exhibited statistically significant phylogenetic signal in birds but not in mammals. Thus, for birds, related species tended to be similar in small intestine length and nominal surface area, even after accounting for relations with body mass and diet. A reduced small intestine in birds may decrease the capacity for breakdown and active absorption of nutrients. Birds do not seem to compensate for reduced digestive and absorptive capacity via a longer gut retention time of food, but we found some evidence that birds have an increased mucosal surface area via a greater villus area, although not enough to compensate for reduced nominal surface area. We predict that without increased rate of enzyme hydrolysis and/or mediated transport and without increased passive absorption of water-soluble nutrients, birds may operate with a reduced digestive capacity, compared with that of nonflying mammals, to meet an increase in metabolic needs (i.e., a reduced spare capacity).     

The effects of age and chronic restricted feeding on protein synthesis and growth of the large intestine of the rat.

1. In vivo rates of protein synthesis and growth of the large intestine were studied in ad libitum fed control and chronic diet restricted rats between 3 and 149 weeks post partum. 2. Restricted feeding (50% reduced intake) when imposed from weaning significantly extends the life span of rodents through an unknown biochemical mechanism. 3. The change in nutritional status slows the accumulation of RNA, DNA and protein in the large intestine but does not modify the fractional rate of protein synthesis. 4. It was therefore deduced, that intracellular protein degradation, or the rate of mucosal cell extrusion into the gut lumen, is accelerated by chronic restricted feeding.     

Bacteria,phages and pigs: the effects of in-feed antibiotics on the microbiome at different gut locations

Disturbance of the beneficial gut microbial community is a potential collateral effect of antibiotics, which have many uses in animal agriculture (disease treatment or prevention and feed efficiency improvement). Understanding antibiotic effects on bacterial communities at different intestinal locations is essential to realize the full benefits and consequences of in-feed antibiotics. In this study, we defined the lumenal and mucosal bacterial communities from the small intestine (ileum) and large intestine (cecum and colon) plus feces, and characterized the effects of in-feed antibiotics (chlortetracycline, sulfamethazine and penicillin (ASP250)) on these communities. 16S rRNA gene sequence and metagenomic analyses of bacterial membership and functions revealed dramatic differences between small and large intestinal locations, including enrichment of Firmicutes and phage-encoding genes in the ileum. The large intestinal microbiota encoded numerous genes to degrade plant cell wall components, and these genes were lacking in the ileum. The mucosa-associated ileal microbiota harbored greater bacterial diversity than the lumen but similar membership to the mucosa of the large intestine, suggesting that most gut microbes can associate with the mucosa and might serve as an inoculum for the lumen. The collateral effects on the microbiota of antibiotic-fed animals caused divergence from that of control animals, with notable changes being increases in Escherichia coli populations in the ileum, Lachnobacterium spp. in all gut locations, and resistance genes to antibiotics not administered. Characterizing the differential metabolic capacities and response to perturbation at distinct intestinal locations will inform strategies to improve gut health and food safety.     

三种鲤科鱼类肠道内分泌细胞的初探

使用Grimelius嗜银染色法对草鱼,鲤,翘嘴红鳇3种不同食性的鲤科鱼的肠道内分泌细胞进行了研究,在3种鱼的整个肠道上均发现有内分泌细胞的分布。在前肠前段中,内分泌细胞分布最多,愈向后分布愈少,在肠褶各处均有内分泌细胞分布,以基部分布最密,内分泌细胞几乎都为开放型,位于上皮细胞和杯状细胞之间,将胞突伸向肠腔,有极少数内分泌细胞兼有开放型和封闭型细胞的特点,在它们顶端胞突伸向腔的同时,基部也伸出突起将分泌物送入邻近细胞或细胞间隙中,肠上皮中还发现一种与内分泌细胞具有同样嗜银特性的圆形颗粒。     

Effect of early antibiotic intervention on specific bacterial communities and immune parameters in the small intestine of growing pigs fed different protein level diets

Antibiotics are designed to affect gut microbiota and subsequently gut homeostasis. However, limited information exists about short- and long-term effects of early antibiotic intervention (EAI) on gut homeostasis (especially for the small intestine) of pigs following antibiotic withdrawal. We investigated the impact of EAI on specific bacterial communities, microbial metabolites and mucosal immune parameters in the small intestine of later-growth-stage pigs fed with diets differing in CP levels. Eighteen litters of piglets were fed creep feed with or without antibiotics from day 7 to day 42. At day 42, pigs within each group were offered a normal- or low-CP diet. Five pigs per group were slaughtered at days 77 and 120. At day 77, EAI increased Enterobacteriaceae counts in the jejunum and ileum and decreased Bifidobacterium counts in the jejunum and ileum (P < 0.05). Moreover, tryptamine, putrescine, secretory immunoglobulin (Ig) A and IgG concentrations in the ileum and interleukin-10 (IL-10) mRNA and protein levels in the jejunum and ileum were decreased in pigs with EAI (P < 0.05). At day 120, EAI only suppressed Clostridium cluster XIVa counts in the jejunum and ileum (P < 0.05). These results suggest that EAI has a short-term effect on specific bacterial communities, amino acid decarboxylation and mucosal immune parameters in the small intestine (particularly in the ileum). At days 77 and 120, feeding a low-CP diet affected Bifidobacterium, Clostridium cluster IV, Clostridium cluster XIVa and Enterobacteriaceae counts in the jejunum or ileum (P < 0.05). Moreover, feeding a low-CP diet increased the concentrations of Igs in the jejunum and decreased pro-inflammatory cytokines levels in the jejunum and ileum (P < 0.05). At day 120, feeding a low-CP diet increased short-chain fatty acid concentrations, reduced ammonia and spermidine concentrations and up-regulated genes related to barrier function in the jejunum and ileum (P < 0.05). These results suggest that feeding a low-CP diet changes specific bacterial communities and intestinal metabolite concentrations and modifies mucosal immune parameters. These findings contribute to our understanding on the duration of the impact of EAI on gut homeostasis and may provide basis data for nutritional modification in young pigs after antibiotic treatment.     

The feeding ecology of the Central American cichlid Cichlasoma urophthalmus (Gunther)

The feeding habits of the cichlid Cichlasoma urophthalmus were studied in a brackish-water lagoon in Yucatan Peninsula, Mexico, from spring 1985 to spring 1986. The strong mandibular, maxillary and pharyngeal teeth, and the short intestine strongly suggest that C. urophthalmus is primarily a carnivore. Subsequent gut contents analysis revealed that this species feeds principally on invertebrates throughout the year and that there were few differences between the five seasons studied. The algal material found in some stomachs may be consumed as a consequence of predation on small invertebrates, but the feeding structures and short intestine makes this species unable to digest vegetable materials efficiently. Differences with other cichlids used in aquaculture are discussed.     

The influence of feeding habits on whole-body metal concentrations in aquatic insects

SUMMARY.

• 1 Concentrations of seven metals in forty taxa of aquatic insects were determined in order to examine the influence of the insects’ feeding habits on their whole-body metal content. Species were grouped into five feeding categories which reflected both the type of material the organisms ingested and their contact with sediments during feeding.
• 2 Species such as the burrowing mayflies (Ephemeridae) and some of the Chironomidae, which indiscriminately ingest sediment along with detritus, had the highest concentrations of most metals. Filter feeders (e.g. Hydropsychidae) had the next highest concentrations, followed by species which to some degree selectively ingest detritus and periphyton (e.g. many Ephemeroptera, Plecoptera and Trichoptera). Carnivores and surface feeding species, such as the Gerridae and Gyrinidae, had the lowest metal concentrations.
• 3 Analysis of metal concentrations of both gut contents and bodies of individuals from each of these feeding types explain these differences. Gut material was enriched in most metals (Co, Cr, Fe, Sb, Sc) relative to their concentrations in the organism's body and it often constituted a major proportion of an organism's whole-body burden of a metal.
• 4 Both the concentrations of metals in the gut material and the proportion of the whole-body burden of a metal that was associated with gut contents varied with the feeding habit of a species. This was because of differences in the amount of inorganic material ingested by the species in each feeding category, higher concentrations occurring in organisms which ingested relatively greater amounts of sediment.
• 5 Organism concentrations of K and Na were less affected by feeding habits since the majority of the whole-body burden of these metals was associated with an organism's tissue and surface rather than with gut material.

     

Seasonality in Dietary Shifts in Size-Structured Freshwater Fish Assemblages in Three Reservoirs of Sri Lanka

We studied seasonal changes in feeding habits of size-structured fish assemblages in three freshwater reservoirs in Sri Lanka. We obtained fish samples for diet analysis from three reservoirs during the months of rising water level (RIWL) and receding water level (REWL). During RIWL, peripheral areas with terrestrial/semi-terrestrial macrophytes get inundated, which resulted in increased food availability for macrophyte feeding fish. During REWL, detrital food sources increase due to decaying terrestrial plant material, which has inundated. Based on the dietary habits of individual species in the three reservoirs during RIWL and REWL, it is evident that detritivorous and phytoplanktivorous fish species, which belong to low trophic levels do not show significant variation in dietary habits between the two seasons (e.g. Oreochromis mossambicus, Oreochromis niloticus and Amblypharyngodon melettinus). Stenophagous species such as benthic invertebrate predators (Puntius chola and Puntius dorsalis), macrophytophagous species (Etroplus suratensis and Tilapia rendalli) and zooplanktivorous Hemirhamphus limbatus do not exhibit significant variation in dietary habits between seasons. Also their feeding habits do not vary with body size. Euryphagous species such as Puntius filamentosus on the other hand, exhibit variations in dietary habits between seasons as well as with body size. Stenophagous species, which feed on detritus and phytoplankton and euryphagous species, which exhibit temporal dietary plasticity, are therefore abundant in fish assemblages of these reservoirs.     

Comparative morphology and ecomorphology of the gut in European cyprinids (Telostei)

The patterns of coiling of the gut were compared in 22 species of Eurasian Cyprinidae. In selected species, also the length of gut and mucosal surface structure were compared. Piscivorous ( Aspius aspius ), planktivorous ( Abramis ballerus ) fishes as well as species feeding mainly on plankton and wind-borne' drift'( Alburnus alhurnus, Pelecus cultratus ) have the relatively shortest guts, with only a single loop. The same simple arrangement of a short gut is present in many euryphagous species with more or less carnivorous tendencies ( Abramis sapa, Alburnoides bipunctalus, Abramis brama, Blicca bjoerkna, Chalcalburnus chalcoides memo, Gobio gobio, Leuciscus cephalus, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus. Tinea tinea, Vimba vimba ). Some benthivorous winnowers (oropharyngeal sorters) and species with herbivorous feeding tendencies have relatively long guts showing a more complex pattern of loops and coils ( Barbus barbus, Carassius carassius, Chondrostoma nasus, Ctenopharyngodon idella, Cyprinus carpio ). The goldfish, Carassius auratus , has the most complex coils. Scanning electron microscopy of the mucosal surface revealed five types of folding in the intestinal bulb which were only loosely related to feeding: 1, smooth surface ( Aspius aspius, Leuciscus cephalus, Vimba vimba ); 2, irregularly branching folds ( Alhurnus alburnus, Barbus barbus, Blicca bjoerkna, Chalcalburnus chalcoides memo, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus ); 3, curl-like folds ( Tinea tinea ); 4, net-like folding pattern ( Abramis brama ); 5, honeycomb-like mucosal structure ( Cyprinus carpio ).     

山溪鲵消化道粘膜上皮的扫描电镜研究

用扫描电镜观察了山溪鲵的咽、食管、胃、怕和大肠粘膜上皮表面细微结构及断面的结构特征。发现咽和食道上皮表面有比较宾微脊;胃粘膜上皮表面有微绒毛,周转的长 密集,顶部的短而稀少;胃粘膜上皮表面的微绒毛似苔葡状覆盖在细胞的表面;杯状细胞分布在上皮细胞之间。同时,还讨论了这些结构与机能的关系。     

Gut morphology and morphometry in the epauletted Wahlberg's fruit bat (Epomophorus wahlbergi, Sundevall, 1846)

The morphological adaptations of the fruit bat small intestine to which the high functional efficiency could be related and the possible landmarks delineating the various parts of the gut were examined. The stomach was the carnivorous type with large rugae spanning the entire luminal aspect down to the pyloric sphincter, which was reflected internally as a prominent fold. Externally, the intestine was a continuous tube uninterrupted by any structures. The cranial fifth of the small gut had long, branching and anastomosing villi, which caudally turned to finger-like discrete structures that became rather short and stumpy and diminished at the beginning of the colon. The colon had longitudinal folds that were macroscopically discernible from the mucosal aspect of the opened intestine and that continued into the rectum. The small gut formed 94% of the whole intestinal length, the colon and the rectum taking 4 and 2%, respectively. Ultrastructurally, the enterocyte showed a prominent brush border and the lateral membranes were modified into numerous tortuous interdigitating processes. Adjacent enterocytes were joined by these processes through desmosomes. The processes also participated in pinocytotic fluid uptake from the intercellular spaces with resultant numerous intracellular vacuoles of varied sizes. Solutes absorbed into the cells were probably first passed into the intercellular compartment to create a concentration gradient thus enhancing further absorption into the cell. We conclude that the uniquely elaborate ultrastructure of the enteric epithelium coupled with the vast microvillous surface areas reported elsewhere are partly responsible for the very high absorption rates reported in the fruit bat small intestine.     

Isoosmotic transport of fluid across the hamster small intestine in the presence of phlorizin-induced inhibition of sugar transport.

Experiments were performed to investigate whether the fluid transported across the small intestine is isoosmotic with the mucosal solution when the active transport of glucose is partially inhibited. Everted hamster mid small intestine was incubated in one of the following four mucosal solutions: (1) Isotonic control, Krebs-Ringer bicarbonate solution containing 10 mM glucose (KRBSG), (2) Isotonic with phlorizin, KRBSG + 5X10-5 M phlorizin, (3) Hypertonic control, KRBSG + 50 mM mannitol, (4) Hypertonic with phlorizin, KRBSG + 50 MM mannitol + 5x10-5 M phlorizin. The serosal surface of the intestine was not bathed. Results indicate that the transported fluid was always isoosmotic with any of the mucosal solutions used. When the mucosal solution was made hypertonic with mannitol, the concentration of glucose and electrolytes in the absorbate increased, and as a result, the absorbate became hypertonic and isoosmotic with the mucosal solution. The presence of phlorizin either in the isotonic or in the hypertonic mucosal solution decreased the glucose concentration of the absorbate, but the transported fluid became isoosmotic with the mucosal solution due to a higher concentration of Na, K, and their associated anions. Phlorizin caused a decrease in the transmural potential difference. In spite of this, the presence of this glucoside in the mucosal solution increased the transport of sodium in relation to glucose transport. It is suggested that, at the concentrations used, phlorizin inhibits sodium movement through the electrogenic pathway, but increases the transport of this ion through the non-electrogenic route. This increase in neutral sodium transport seems to compensate for the low concentration of glucose in the absorbate, so that the absorbate becomes isoosmotic with the mucosal solution whether the latter is isotonic or hypertonic. It is suggested further that isoosmotic transport of fluid is an inherent property of the small intestine and that there may be an osmoregulatory mechanism in the gut which controls this process.     

Size and shape in the phylum Phoronida

The lophophorate phylum Phoronida consists of about 13 species, which differ in body length and width, number of longitudinal muscles, lophophore geometry and number of lophophore tentacles. In absolute terms large species have a larger body width, more tentacles, more longitudinal muscles and greater coiling of the lophophore than small species. However, size and shape analyses suggest that with increasing size: (I) the body surface area to volume ratio increases because body length increases faster than body width; (2) the relative number longitudinal muscles decreases, and (3) the relative feeding surface area of the lophophore decreases because tentacle diameter is constant while tentacle number increases at the same rate as body length and tentacle length increases more slowly than tentacle number. Coiling and spiraling of the lophophore in large species may be an attempt to compensate for this last relationship. We suggest that the habits, mode of growth and feeding mechanism of phoronids constrain size-related changes in shape.     

Feeding of Perla grandis nymphs (Plecoptera: Perlidae) in an Apennine first order stream (Rio Berga,NW Italy)

Feeding habits of Perla grandis (Rambur) nymphs have been investigated in the Rio Berga, an Apenninic stream of Northwestern Italy. In this study, we analysed gut contents of 50 nymphs of this species, with the aim to investigate feeding preferences. Nymphs were collected from a single riffle, of which benthic coenosis was also determined. We detected a change in the diet during ontogenesis, with small instars feeding mainly on detritus and large instars strictly carnivorous. We also detected the existence of an evident trophic selection: diet was almost entirely dominated by Chironomidae, independently from their availability on the substratum. This finding is discussed on the basis of ecological and ethological considerations.