低温驯化对布氏田鼠小肠黏膜结构和黏膜免疫相关细胞的影响

环境温度的变化影响野生啮齿动物的消化道形态与功能。小肠是吸收营养成分的主要部位,其结构和功能具有可塑性。为了解小肠黏膜的结构和功能对环境温度变化的响应机制,以布氏田鼠为研究对象,比较了低温组和常温组动物小肠黏膜的组织结构和小肠黏膜免疫相关细胞的数目。结果显示：（1）低温组布氏田鼠的十二指肠、空肠和回肠的绒毛长度及绒毛长度与隐窝深度的比值均高于对照组;（2）低温驯化使布氏田鼠小肠上皮内淋巴细胞的数量增加;（3）低温驯化使布氏田鼠十二指肠、空肠和回肠的杯状细胞数量均显著增加。结果表明,在低温环境下布氏田鼠的小肠黏膜结构和免疫细胞的数量发生了可塑性变化,这可能与低温环境下的高能量需求和免疫功能的变化有关。     

Cytochemical analysis of single villus peptidase activities in pig intestine during neonatal development

The present work uses a new technique of whole tissue cytochemistry and automated scanning to obtain measurements of peptidase activity and surface structure in intact villi microdissected from the jejunum of newborn and 28-day-old pigs. Intact villi from 28-day-old pigs are shown by this method to contain 30% more aminopeptidase N and 400% more dipeptidylpeptidase IV activity than is found on villi taken from newborn pig intestine. Villi taken from 28-day-old pig intestine are also half as long and twice as wide at their base as those taken from newborn animals. These changes in shape take place without significantly affecting the total surface area of the villus. Increases in peptidase activities occurring during postnatal development can be further subdivided into those dependent upon induced changes in enterocyte biochemistry and those dependent upon the changing geometry of villi. Over 90% of the total increase in peptidase activities occurring during neonatal development was shown, by this analysis, to involve enterocyte reprogramming of enzyme production. The present method of whole tissue cytochemistry appears to combine successfully the ability to measure peptidase activities at the cellular level in undisrupted tissue with a facility to relate these results to the overall shape of a single villus. These and more general applications of the method now provide new ways to analyse a variety of changes taking place in intestinal structure and function in a quantitative manner.     

Acid lipase in rat intestinal mucosa: physiological parameters

Previous studies have shown that up to a half of infused triacylglycerol does not exit the intestine via lymphatics. This suggests the presence of a mucosal lipase which could provide fatty acids for potential transport via the portal vein. The present study describes an acid-active lipase in rat intestinal mucosa. Acid lipase was assayed using a glyceryl tri[14C]oleate emulsion (pH 5.8). Mucosal homogenates were differentially centrifuged to yield cellular organelles and cytosol. Cells were sequentially released from villi using citrate and EDTA. The enzyme was found to be most active in the proximal quarter intestine and in the upper third of villi. Its greatest activity was in the lysosomal fraction. Esophageal diversion demonstrated that lingual lipase was not the precursor of the mucosal acid lipase. Bile salts stimulated activity 3- to 5-fold, but other neutral or anionic detergents were inhibitory. Of the detergents tested, taurocholate at super critical micellar concentrations could restore activity only with SDS. Sepharose 6B chromatography suggested that the enzyme partitioned into an SDS and taurocholate mixed micelle. We conclude that mucosal acid lipase is a distinct, intrinsic enzyme of the intestinal mucosa. It is predominantly lysosomal in origin. The location of its greatest activity in the villus tips of the proximal intestine suggests that it is potentially involved in mucosal triacylglycerol disposal.     

The measurement of villus cell population size in the mouse small intestine in normal and abnormal states: a comparison of absolute measurements with morphometric estimators in sectioned immersion-fixed material

Abstract From a functional viewpoint, the most important part of the small intestinal mucosa is the villus epithelium; in the experimental study of intestinal adaptation it is often necessary to estimate the size of the population. For these reasons, a systematic study of methods of measuring the size of the villus cell population was undertaken in villi of normal morphology from control animals, and in villi of abnormal morphology as produced by treatment of mice with cytosine arabinoside (Ara-C).
The villus cell population can be measured with precision and accuracy in both normal and abnormal mucosal states, with a relative standard error usually less than 5%, with good reproducibility, and with very low counting errors. In the mouse a practically linear relationship between the villus cell population size and position in the small intestine can be shown. In normal, control animals, linear estimates of villus population, for example the villus height, the villus core height, and the villus row count measured in sections of immersion-fixed material, were found to be rough approximations as indicators of the villus cell population, and were highly correlated with it. Product variables, comprising the products of a height with a width measurement, show a large improvement over the linear variables as estimators of villus cell population. In populations of abnormally shaped villi produced by Ara-C, both linear and product variables showed a considerable decrease in correlation with the villus cell population. Consequently, indirect, linear measurements of the villus population size do not accurately reflect the size of the villus population in abnormal villi.
Finally, a method comparing theoretical and measured surface: volume indices was used to indicate that the most appropriate shape for normal mouse villi is a simple cylinder; this method would also be applicable for other villus cell populations.     

The measurement of villus cell population size in the mouse small intestine in normal and abnormal states: a comparison of absolute measurements with morphometric estimators in sectioned immersion-fixed material

From a functional viewpoint, the most important part of the small intestinal mucosa is the villus epithelium; in the experimental study of intestinal adaptation it is often necessary to estimate the size of the population. For these reasons, a systematic study of methods of measuring the size of the villus cell population was undertaken in villi of normal morphology from control animals, and in villi of abnormal morphology as produced by treatment of mice with cytosine arabinoside (Ara-C). The villus cell population can be measured with precision and accuracy in both normal and abnormal mucosal states, with a relative standard error usually less than 5%, with good reproducibility, and with very low counting errors. In the mouse a practically linear relationship between the villus cell population size and position in the small intestine can be shown. In normal, control animals, linear estimates of villus population, for example the villus height, the villus core height, and the villus row count measured in sections of immersion-fixed material, were found to be rough approximations as indicators of the villus cell population, and were highly correlated with it. Product variables, comprising the products of a height with a width measurement, show a large improvement over the linear variables as estimators of villus cell population. In populations of abnormally shaped villi produced by Ara-C, both linear and product variables showed a considerable decrease in correlation with the villus cell population. Consequently, indirect, linear measurements of the villus population size do not accurately reflect the size of the villus population in abnormal villi. Finally, a method comparing theoretical and measured surface: volume indices was used to indicate that the most appropriate shape for normal mouse villi is a simple cylinder; this method would also be applicable for other villus cell populations.     

Fish oil prevents effect of high cholesterol diet on active intestinal transport of galactose

We tested the hypothesis that diets containing fish oils prevent the effects of a high cholesterol diet on the morphology and nutrient uptake of the intestine. Isocaloric semisynthetic diets were supplemented with beef tallow or fish oil containing low or high amounts of cholesterol and were fed to growing female Wistar rats for 14 days, after which the in vitro jejunal and ileal uptake of glucose, galactose, long-chain fatty acids, and cholesterol was determined. Feeding cholesterol with beef tallow was associated with a 12% decrease in the jejunal mucosal surface area. Feeding fish oil decreased jejunal mucosal surface area by 24%, as compared with the beef tallow diet, but the reduction was increased to 42% when fish oil and cholesterol were fed together. Ileal surface area was unaffected by varying the major source of dietary lipid, or by adding cholesterol. Despite the effect of fish oil on the mucosal surface area, the jejunal and ileal uptake of saturated as well as unsaturated long-chain fatty acids and cholesterol was similar in the four diet groups. Cholesterol supplementation enhanced the jejunal uptake of high concentrations of galactose only when fed with beef tallow, i.e., feeding fish oil prevented the enhancing effect of cholesterol on galactose uptake observed when beef tallow was fed. Thus, (i) a fish oil diet prevents the enhancing effect of cholesterol on jejunal active transport of galactose, an effect not explained by the reduction in jejunal mucosal surface area observed with the fish oil diet; (ii) these dietary manipulations result in a clear dissociation of the morphological from the transport adaptation of the intestine; and (iii) substitution of fish oil for beef tallow as the major source of lipid in the diet prevents the influence of cholesterol on the active intestinal transport of galactose.     

Histopathological changes caused by Enteromyxum leei infection in farmed sea bream Sparus aurata

Histological examinations were carried out on the stomach, pyloric caeca and 4 different parts of the intestine, as well as the rectum, hepatopancreas, gall bladder and spleen of 52 sea bream Sparus aurata spontaneously infected by Enteromyxum leei. Fifteen fish from a non-infected farm were included as a control. Clinical signs appeared only in extensively and severely infected fish. We observed Enteromyxum leei almost exclusively in the intestinal tract, and very rarely in the intrahepatic biliary ducts or gall bladder. We observed heavily infected intestinal villi adjacent to parasite-free villi. Histological changes indicated a parasite infection gradually extending from villus to villus, originating from an initial limited infected area probably located in the rectum. The parasite forms were exclusively pansporoblasts located along the epithelial basement membrane. Periodic acid-Schiff (PAS)-Alcian blue was the most useful histological stain for identifying the parasite and characterising the degree of intestinal infection. We observed severe enteritis in infected fish, with inflammatory cell infiltration and sclerosis of the lamina propria. The number of goblet cells was considerably and significantly decreased in heavily infected fish. The intestines of 4 of the 5 survivor fish were totally free of parasites and showed severe chronic enteritis with a regenerative epithelium, suggesting that an acquired immune process may spontaneously eliminate parasites.     

Changes in the small intestine of Schistosoma mansoni-infected mice fed a high-fat diet

The consumption of a high-fat diet modifies both the morphology of the small intestine and experimentally tested effects of schistosomiasis mansoni. However, whether a schistosomiasis infection associated with a high-fat diet causes injury to the small intestine has never been investigated. Mice were fed either a high-fat or a standard-fat diet for 6 months and were then infected with Schistosoma mansoni cercariae. Physical characteristics of the intestinal tissue (mucosal thickness, small intestinal villi length and height, and abundance of goblet cells and enterocytes on the villous surface) and the distribution of granulomas along the intestinal segments and their developmental stage were measured at the time of sacrifice (9 or 17 weeks post-infection). The group fed a high-fat diet exhibited different granuloma stages, whereas the control group possessed only exudative granulomas. The chronically infected mice fed a high-fat diet exhibited higher granuloma and egg numbers than the acutely infected group. Exudative, exudative/exudative-productive and exudative-productive granulomas were present irrespective of diet. Computer-aided morphometric analysis confirmed that villus length, villus width, muscular height and submucosal height of the duodenal and jejunal segments were affected by diet and infection. In conclusion, a high-fat diet and infection had a significant impact on the small intestine morphology and morphometry among the animals tested.     

Effect of external abdominal irradiation on intestinal morphology and brush border membrane enzyme and lipid composition

Previous studies have shown that external abdominal irradiation is associated with alterations in intestinal morphology and function. The activity of the jejunal brush border membrane (BBM) enzyme markers sucrase (S) and alkaline phosphate (AP) were not altered by 600 rad irradiation in the rat. In contrast, ileal BBM, AP, and AP/S were increased 3, 7/8, and 28 days postirradiation. The total lipid composition of the jejunal BBM was lower than in control animals only at 3 days postirradiation; this was due to a decrease in the total free fatty acid content. In addition to a lower total free fatty acid content, the ileal BBM contained an increased amount of total phospholipid (PL) which resulted in an increased phospholipid/cholesterol ratio at 3 days following irradiation. Variations in the BBM phospholipid composition occurred in both jejunum and ileum. In the jejunal BBM, the phospholipid composition changes did not alter the choline or amine phospholipid content; therefore, the choline/amine phospholipid ratio was unaffected by irradiation at 600 rad. In the ileal BBM, the phosphatidyl ethanolamine was increased at 3, 7/8, 14, and 28 days following irradiation. The choline/amine phospholipid ratio was not altered in the ileal BBM due to concomitant increases in lecithin content. Jejunal villus height, villus surface area, and the number of cells per villus were decreased at 3 days postirradiation, but increased by day 7/8 and 14 postirradiation to levels much higher than observed in control jejunal villi. The mucosal surface area was decreased at 3 and 7/8 days following irradiation but returned to control values by Day 14. Jejunal microvillus morphology was unaffected by irradiation. Few significant changes were observed in ileal villus morphology following irradiation at 600 rad. Ileal villus height, villus surface area, and mucosal surface area did not change, but the number of cells per villus initially decreased at 3 days and then increased beyond control values at 7/8 and 14 days postirradiation. Ileal microvillus height was significantly decreased only at 7 days postirradiation, while the number of microvilli per micron was increased only at 3 days postirradiation. This study suggests that changes in intestinal morphology and brush border composition may contribute to the altered passive permeation toward lipids which has been reported following abdominal radiation.     

Cell migration pathway in the intestinal epithelium: an in situ marker system using mouse aggregation chimeras

The cell migration pathway in the intestinal epithelium of DDK in equilibrium C57BL/6JLac mouse chimeras is demonstrated using Dolichos biflorus agglutinin-peroxidase as strain-specific marker. Cell sheets of one genotype extend in relatively straight lines from crypt to villus apex. Narrow sheets are mostly interrupted in the distal two-thirds of duodenal but not ileal villi, suggesting that in the duodenum cell loss occurs below the apical extrusion zone. These differences between duodenum and ileum correspond to differences in villus shape. The pattern of cell migration in Peyer's patch epithelium is consistent with that of the duodenum. In chimeric colon, sharply demarcated territories of crypts with a narrow cuff of surface epithelium represent the counterpart of the villus/crypt unit of the small intestine.     

Histological effects of cyanide, stress and starvation on the intestinal mucosa of Pomacentrus coelestis, a marine aquarium fish species

The histological effects of cyanide, stress and starvation on the gastrointestinal tract of Pomacentrus coelestis , a common marine aquarium fish species, were investigated. Neither anaesthetic cyanide nor stress were found to have any detectable effects on the mucosal lining of the intestine. However, starvation resulted in a significant reduction in the intestine length, the surface area of the intestinal mucosa and the mucosal thickness, all occurring within 13 days.     

Glucagon-like peptide-2 induces intestinal adaptation in parenterally fed rats with short bowel syndrome

Glucagon-like peptide-2 (GLP-2) is an intestinal trophic enteroendocrine peptide that is associated with intestinal adaptation following resection. Herein, we investigate the effects of GLP-2 in a total parenteral nutrition (TPN)-supported model of experimental short bowel syndrome. Juvenile Sprague-Dawley rats underwent a 90% small intestinal resection and jugular catheter insertion. Rats were randomized to three groups: enteral diet and intravenous saline infusion, TPN only, or TPN + 10 microg.kg(-1).h(-1) GLP-2. Nutritional maintenance was isocaloric and isonitrogenous. After 7 days, intestinal permeability was assessed by quantifying the urinary recovery of gavaged carbohydrate probes. The following day, animals were euthanized, and intestinal tissue was processed for morphological and crypt cell proliferation (CCP) analysis, apoptosis (caspase-3), and expression of SGLT-1 and GLUT-5 transport proteins. TPN plus GLP-2 treatment resulted in increased bowel and body weight, villus height, intestinal mucosal surface area, CCP, and reduced intestinal permeability compared with the TPN alone animals (P < 0.05). GLP-2 treatment induced increases in serum GLP-2 levels and intestinal SGLT-1 expression (P < 0.01) compared with either TPN or enteral groups. No differences were seen in the villus apoptotic index between resection groups. Enterally fed resected animals had a significant decrease in crypt apoptotic indexes compared with nontreated animals. This study demonstrates that GLP-2 alone, without enteral feeding, stimulates indexes of intestinal adaptation. Secondly, villus hypertrophy associated with adaptation was predominantly due to an increase in CCP and not to changes in apoptotic rates. Further studies are warranted to establish the mechanisms of action and therapeutic potential of GLP-2.     

Intestinal intraepithelial lymphocyte gamma delta-T cell-derived keratinocyte growth factor modulates epithelial growth in the mouse

Keratinocyte growth factor (KGF) promotes intestinal epithelial growth. To understand the relevance of intraepithelial lymphocyte (IEL)-derived KGF expression on epithelial growth, we used a mouse model of villus atrophy by the administration of total parenteral nutrition, and a model of villus hypertrophy by the creation of a short bowel syndrome. KGF expression was confined to gammadelta-TCR(+) IELs. IEL-derived KGF expression was highest in the crypts, somewhat less in the lower portion of villi, and markedly lower in the upper portion of villi. Total parenteral nutrition administration was associated with a down-regulation of IEL-derived KGF expression, and short bowel syndrome was associated with an up-regulation of IEL-derived KGF expression. In the absence of gammadelta-TCR(+) IEL, using gammadelta(-/-) mice, intestinal epithelial cell proliferation decreased in control, and in both mucosal atrophy (22% decline) and mucosal hypertrophy (14%) models. These results show that KGF from IELs is an important factor for maintenance of intestinal epithelial cell proliferation and villus growth.     

Vergleich verschiedener morphometrischer Methoden zur Erfassung der Schleimhautoberfläche des Rattendünndarms und deren Beziehung zur Funktion

Zusammenfassung In der vorliegenden Untersuchung werden am Rattendünndarm die Oberflächen einzelner Zotten mit verschiedenen Methoden ermittelt sowie die Oberfläche des Resorptionsepithels pro Darmareal bestimmt. Die gefundenen Meßergebnisse der Zottenoberflächenbestimmung werden mit der am Schnitt vermessenen Zottenhöhe verglichen und mit Resorptionsgrößen und enzymatischen Aktivitäten der Dünndarmschleimhaut in Beziehung gesetzt. Dabei zeigt sich, daß unter den Bedingungen eines Schleimhautumbaus vom hyperregeneratorischen Typ an der Ratte die Gesamtzottenoberfläche pro Darmareal besser mit den Funktionsparametern der Schleimhaut korreliert als die Zottenhöhe.

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Comparison of different morphometric methods to estimate the surface of the rat intestinal mucosa. Their relationship to intestinal function

Summary In contrast to the human small intestine with predominantly fingerlike villi, trapezoid forms are encountered in the small bowel of the rat. For this reason, it is doubtful whether it is sufficient to measure the villus height alone as a representative parameter for the assessment of the villus surface.In this study, the method developed by Clarke is employed to calculate the villus surface per unit area of intestine. The data obtained by this method are compared with those estimated planimetrically. Correlations were then established between the absorptive capacity and enzymatic activity of the intestinal mucosa on the one hand, and the villus height or the villus area obtained by each method on the other hand. Under our experimental conditions — a hyperregenerative transformation of the intestinal mucosa caused by chronic exposure to glucagon—the results indicate that the calculated villus surface per unit area of small intestine correlates better than the villus height with the functional parameters of the intestinal mucosa.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft (Ri 136/10)     

Correlation of structural changes at different levels of the jejunal villus with positive net water transport in vivo and in vitro.

Experiments were done for indentification and localization of certain structural changes at different levels of jejunal villus of the hamster during positive and negative water transport across the intestine in vivo and in vitro. Positive transport occurred when the mucosal surface of the intestine was bathed (in vitro experiments) or perfused (in vivo experiments) with isotonic Krebs-Ringer bicarbonate solution containing 10 mM glucose, and negative water transport was achieved by rendering this solution hypertonic with 150 mM mannitol. Results indicate that during positive net water transport the intestine in vivo transported more fluid and exhibited a more conspicuous dilatation of the lateral intercellular spaces (L.I.S.) than did the in vitro preparation. Dilatation of the L.I.S. in both preparations was present only in the apical part of the villus, suggesting that this is the principal site of water absorption. When the mucosal solution was made hypertonic with mannitol, the L.I.S. in the in vivo intestine totally collapsed, whereas in the in vitro intestine these spaces remained open very slightly. These morphological changes correspond well with our finding that in the presence of the hypertonic mucosal solution there was a greater net negative water transport in vivo than in vitro. Incubation of the intestine in the isotonic mucosal solution produced subnuclear swelling of the mid-villus epithelial cells, and this morphological change was associated with an increase in the water content of the tissue. Perfusion of the in vivo intestine with the isotonic solution produced neither the swellings nor the increase in water content of the tissue. In the presence of hypertonic mucosal solution there was a water loss from the tissue both in vivo and in vitro, and these swellings were not observed. These results are discussed in relation to intestinal sugar transport and to the maturity of the epithelial cells, and it is concluded that transport studies on in vitro preparations may provide valid information on a qualitative basis, if not on a strictly quantitative basis.     

Expression of glucocorticoid receptor in the intestine of a euryhaline teleost, the Mozambique tilapia (Oreochromis mossambicus): effect of seawater exposure and cortisol treatment

Cortisol plays an important role in controlling intestinal water and ion transport in teleosts possibly through glucocorticoid receptor (GR) and/or mineralocorticoid receptor. To better understand the role of GR in the teleost intestine, in a euryhaline tilapia, Oreochromis mossambicus, we examined (1) the intestinal localizations of GR; (2) the effects of environmental salinity challenge and cortisol treatment on GR mRNA expression. The mRNA abundance of GR in the posterior intestinal region of tilapia was found to be higher than that in the anterior and middle intestine. In the posterior intestine, GR appears to be localized in the mucosal layer. GR mRNA levels in the posterior intestine were elevated after exposure of freshwater fish to seawater for 7 days following an increase in plasma cortisol. Similarly, cortisol implantation in freshwater tilapia for 7 days elevated the intestinal GR mRNA. These results indicate that seawater acclimation is accompanied by upregulation of GR mRNA abundance in intestinal tissue, possibly as a consequence of the elevation of cortisol levels. In contrast, a single intraperitoneal injection of cortisol into freshwater tilapia decreased intestinal GR mRNA. This downregulation of the GR mRNA by cortisol suggests a dual mode of autoregulation of GR expression by cortisol.     

Postprandial morphological response of the intestinal epithelium of the Burmese python (Python molurus)

The postprandial morphological changes of the intestinal epithelium of Burmese pythons were examined using fasting pythons and at eight time points after feeding. In fasting pythons, tightly packed enterocytes possess very short microvilli and are arranged in a pseudostratified fashion. Enterocyte width increases by 23% within 24 h postfeeding, inducing significant increases in villus length and intestinal mass. By 6 days postfeeding, enterocyte volume had peaked, following as much as an 80% increase. Contributing to enterocyte hypertrophy is the cellular accumulation of lipid droplets at the tips and edges of the villi of the proximal and middle small intestine, but which were absent in the distal small intestine. At 3 days postfeeding, conventional and environmental scanning electron microscopy revealed cracks and lipid extrusion along the narrow edges of the villi and at the villus tips. Transmission electron microscopy demonstrated the rapid postprandial lengthening of enterocyte microvilli, increasing 4.8-fold in length within 24 h, and the maintaining of that length through digestion. Beginning at 24 h postfeeding, spherical particles were found embedded apically within enterocytes of the proximal and middle small intestine. These particles possessed an annular-like construction and were stained with the calcium-stain Alizarine red S suggesting that they were bone in origin. Following the completion of digestion, many of the postprandial responses were reversed, as observed by the atrophy of enterocytes, the shortening of villi, and the retraction of the microvilli. Further exploration of the python intestine will reveal the underlying mechanisms of these trophic responses and the origin and fate of the engulfed particles.     

Smooth muscle overexpression of IGF-I induces a novel adaptive response to small bowel resection

Prior studies of intestinal adaptation after massive small bowel resection (SBR) have focused on growth factors and their effects on amplification of the gut mucosa. Because adaptive changes have also been described in intestinal smooth muscle, we sought to determine the effect of targeted smooth muscle growth factor overexpression on resection-induced intestinal adaptation. Male transgenic mice with smooth muscle cell overexpression of insulin-like growth factor I (IGF-I) by virtue of an alpha-smooth muscle actin promoter were obtained. SMP8 IGF-I transgenic (IGF-I TG) and nontransgenic (NT) littermates underwent 50% proximal SBR or sham operation and were then killed after 3 or 28 days. NT mice showed the expected alterations in mucosal adaptive parameters after SBR, such as increased wet weight and villus height. The IGF-I TG mice had inherently taller villi, which did not increase significantly after SBR. In addition, IGF-I TG mice had a 50% postresection persistent increase in remnant intestinal length, which was associated with an early decline and later increase in relative mucosal surface area. These results indicate that growth factor overexpression within the muscularis layer of the bowel wall induces significant postresection adaptive intestinal lengthening and a unique mucosal response. IGF-I signaling within the muscle wall may play an important role in the pathogenesis of resection-induced adaptation.     

Effects of growth hormone on leucine absorption, intestinal morphology, and ultrastructure of the goldish intestine

The mechanisms whereby exogenous growth hormone modulates intestinal structure and function in fish were investigated. Goldfish (Carassius auratus) were fed commercial flake diet sprayed with recombinant carp growth hormone (cGH) daily for 1 month. Control animals received food sprayed with the vehicle. After 1 month of daily feedings, body mass and length were determined, and animals were sacrificed to study intestinal characteristics. Sections of foregut were removed after determination of total gut length for measurement of leucine uptake, histology, and epithelial ultrastructure. Oral administration of cGH for 1 month resulted in a 40% increase in body mass and an 8% increase in body length above controls. Gut length was 43% greater and the gut length to body length ratio was 32% greater as a result of the cGH treatment. Feeding with cGH also resulted in a significant increase in leucine uptake and increased gut mucosal thickness. Analysis of transmission electron micrographs revealed significant increases in the microvillous height and density and epithelial surface area. The findings indicate that growth hormone added to feed may increase growth in fish, in part by significantly increasing gut length, mucosal thickness, and epithelial brush border surface area, leading to enhanced epithelial absorption.     

THE EFFECT OF INTESTINAL RESECTION ON THIRY-VELLA FISTULAE OF JEJUNAL AND ILEAL ORIGIN IN THE RAT: EVIDENCE FOR A SYSTEMIC CONTROL MECHANISM OF CELL RENEWAL

Local and systemic control mechanisms have been postulated to explain the maintenance of steady state cell renewal in intestinal epithelium. Permanent alterations of cell renewal resulting in a new steady state imply alterations in control. Intestinal resection appears to cause such alterations resulting in hyper-plasia of the residual intestine. To test the hypothesis of a systemic control, the effect of 60% mid-intestinal resection on Thiry-Vella fistulae of both jejunal and ileal origin was observed in rats. Results showed that hypoplasia occurred in fistulae without resection of the remaining intestine in continuity. Cell counts of crypt and villus columns and tritiated thymidine uptake in isolated whole crypts were reduced. Scanning electron microscopy showed marked hypoplastic alterations in villi. However, when 60% of the intestine in continuity was resected, hyperplasia occurred not only in the residual intestine but in the fistulae of both jejunal and ileal origin. Cell counts of villus and crypt columns were increased along with increased tritiated thymidine uptake per crypt. Neutral cc-glucosidase and non-specific esterase activities did not change as a result of resection but the activities of both enzymes were greater in ileal fistulae than in ileum in situ. Observations on the different resection response of the jejunal versus ileal fistulae lead to a distinction between inherent and induced differences within the small intestine. This study suggests a systemic control of cell renewal. A possible mechanism involving intestinal vascular physiology is discussed.