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Microsomal fractions from rat small intestine contain a fatty-acid chain-elongation activity. Cofactor requirements are similar to those of the liver microsomal system, but substrate specificity is different. The polyunsaturated arachidonic and timnodonic acids were elongated at very low rates. These results suggest that the relative contents of specific chain-elongation enzymes are different in liver and small intestine.
Evaluation of the small bowel has long been hampered because of its long and multiple complex loop configurations. Yamamoto et al have developed a new method of inserting an endoscope, known as the double-balloon method of enteroscopy, the Fujinon double-balloon endoscopy system being specialised for this application. Two types of endoscope are currently available for this technique. The EN-450 P5 is a thin endoscope for regular use, whereas the EN-450 T5 is a therapeutic double-balloon endoscope with a larger accessory channel of 2.8mm in diameter. Double-balloon endoscopy enables visualisation of the entire small bowel and also allows for interventional therapy in the small intestine. This method can be used either from an oral or an anal insertion. Observation of an affected area with controlled movement of the endoscope enables interventions, including biopsies, haemostasis, balloon dilatation, stent placement, polypectomy and endoscopic mucosal resection, to be performed. In our large study series, it was demonstrated that double-balloon endoscopy permitted exploration of the small intestine with the high success rate of total enteroscopy. The procedure is safe and useful, and it provides high diagnostic yields and therapeutic capabilities.
The possible pancreatic origin of intestinal kallikrein was studied in a jejuno-ileal bypass model in the rat. The bypassed loops were made of variable lengths (2-72 cm) and samples were taken at 10 cm intervals to relate enzyme activities to adaptive changes caused by local and systemic stimulus. The kallikrein activity was dramatically reduced (mean 92.3%) in the bypassed loops while only moderately reduced (mean 35.8%) activities were found in the intestine remaining in continuity. Kallikrein was uniformly distributed throughout the functional small intestine in normal and bypass operated animals. The longitudinal distribution profiles obtained for brush border enzymes in normal animals were almost absent in the bypassed loops, but were apparent in the remaining intestine. The main adaptive growth was observed in the remaining small intestine, Both here and in the loop, the growth depended on the amount of bypassed tissue. Our observations are strongly in favour of a pancreatic origin of the glandular kallikrein activity found in the small intestine in the rat.
Twenty horses with small intestinal obstructions requiring surgery were evaluated prospectively. Ten horses lived (group 1) and 10 died (group 2). Eight of the horses in group 1 had simple obstruction and 7 of the horses in group 2 had strangulation obstruction. There was a significant difference (P less than 0.001) between the mean intraluminal hydrostatic pressure in horses of groups 1 and 2 (6.3 cm H2O and 15 cm H2O, respectively). The mean peritoneal fluid protein concentration in horses of groups 1 and 2 (2.8 mg/dl and 5.4 mg/dl, respectively) also differed significantly between groups (P less than 0.01). Histologic evaluation of the intestinal specimens from horses of group 1 (n = 3) and group 2 (n = 6) revealed more severe mucosal lesions in group 2. The measured values that were not significantly different between the 2 groups included PCV, total serum protein content, WBC count, anion gap, and duration of colic before admission. It was concluded that peritoneal fluid protein concentration and intraluminal hydrostatic pressure in small intestinal obstruction may be used as adjuncts to diagnosis and as prognostic indicators.
The deconvolution technique can be used to compute small intestinal impulse response curves from scintigraphic data. Previously suggested approaches, however, are sensitive to noise from the data. We investigated whether deconvolution based on a new simple iterative convolving technique can be recommended. Eight healthy volunteers ingested a meal that contained indium-111 diethylene triamine penta-acetic acid labelled water and technetium-99m stannous colloid labelled omelette. Imaging was performed at 30-min intervals until all radioactivity was located in the colon. A Fermi function=(1+e-alphabeta)/(1+e(t-alpha)beta) was chosen to characterize the small intestinal impulse response function. By changing only two parameters, alpha and beta, it is possible to obtain configurations from nearly a square function to nearly a monoexponential function. Small intestinal input function was obtained from the gastric emptying curve and convolved with the Fermi function. The sum of least squares was used to find alpha and beta yielding the best fit of the convolved curve to the observed small intestinal time-activity curve. Finally, a small intestinal mean transit time was calculated from the Fermi function referred to. In all cases, we found an excellent fit of the convolved curve to the observed small intestinal time-activity curve, that is the Fermi function reflected the small intestinal impulse response curve. Small intestinal mean transit time of liquid marker (median 2.02 h) was significantly shorter than that of solid marker (median 2.99 h; P<0.02). The iterative convolving technique seems to be an attractive alternative to ordinary approaches for the processing of small intestinal transit data.
Small intestinal absorptive function can be disturbed in iron deficiency. We examined the permeability behavior of the small intestinal mucosa toward lactulose and rhamnose in 26 otherwise healthy children with iron deficiency. Their (mean +/- SD) age was 21 +/- 8.6 months; hemoglobin 7.9 +/- 0.9 g/dl, mean corpuscular volume (MCV) 60.1 +/- 3.4 fl, serum iron 2.72 +/- 0.66 mumol/L, serum ferritin 7.3 +/- 1.6 micrograms/L. After an isotonic oral load of both sugars, their 5-h urinary excretion was measured by gas-liquid chromatography/mass spectrometry. The ratio of the percentage of urinary recovery of the sugars [lactulose/rhamnose (%)] was determined as the permeability index. The tests were repeated in the same subjects after 3 months of iron supplementation, and achievement of an iron sufficient state. In the iron-deficient state, the permeability index was significantly higher than the standard normal value (0.15 +/- 0.05 versus less than 0.07; p less than 0.01), but was not different from normal when the children had attained a normal iron status. The major factor for the alteration of the permeability index in the children with iron deficiency was a significantly lower urinary recovery of rhamnose (which passes the small intestinal epithelium by a transcellular route); the recovery of lactulose (which passes through a paracellular route) was not affected by iron deficiency. Our study indicates that iron deficiency in infants and young children can alter permeability characteristics of the small intestinal mucosa. Iron status should therefore be considered when interpreting permeability tests in the young.
BACKGROUND: The crypt lamina propria of the mouse small intestine has been shown to harbor multiple tiny clusters filled with c-kit- and interleukin 7 receptor (IL-7R)-positive lympho-hemopoietic cells (cryptopatches; CPs). However, it has remained an open question whether similar lymphoid tissue are present in the gastrointesitinal tract in other animals. In the present study, we investigated whether the small intestine of rats harbored lymphoid tissues similar to mouse CPs. METHODS: Immunohistochemical and flow cytometric analyses were carried out using various antibodies, including those to c-kit and IL-7R molecules. RESULTS: Lymphocyte-filled villi (LFVs), populated predominantly with c-kit- and IL-7 receptor (IL-7R)-positive cells and less with T cell receptor (TCR)-alphabeta T cells were found throughout the small intestine of young adult rats. Although LFVs were absent from fetal rat intestine, they were first detected at around 2 weeks after birth. Notably, in most LFVs that settled in the antimesenteric wall of the small intestine in young adult rats, immunoglobulin M-positive B cells were also detectable at the bottom of the LFVs. In aged rats, lymphocytes in some LFVs displayed a different phenotype, comprising a large B-cell area that included a germinal center. Thus, these clusters represent the first description of isolated lymphoid follicles (ILFs) in the rat small intestine. CONCLUSIONS: The present study provides the first evidence for c-kit- and IL-7R-positive lymphocyte clusters in the rat small intestine. Our data also indicating that LFVs and ILFs may constitute novel organized gut-associated lymphoid tissues in lamina propria of the rat small intestine.
BACKGROUND: The small-intestinal epithelium, a rapidly proliferating tissue, is highly sensitive to cycle-specific agents such as radiation. Macrophage inflammatory protein (MIP)-1 alpha has been shown to reduce cell proliferation in bone marrow, seminiferous epithelium, and skin. The current work investigates the activity of an MIP-1 alpha variant, BB-10010, in the gut. METHODS: A single dose of either 0.4 microg/kg or 200 microg/kg was administered to mice 2, 4, 6, 8, 10, 12, or 14 h before animal death. Fifteen crypts from the midpoint of the small intestine were dissected from each animal and squashed, and the numbers of vincristine-arrested metaphases was counted for each fifth of the crypts. RESULTS: A 40%-50% reduction of accumulated metaphases throughout all crypt segments was observed in animals injected with 200 microg/kg of BB-10010 2 h and 4 h before death (P < 0.0001). The animals that received 0.4 microg/kg showed a similar effect at 4 h (P < 0.0001). CONCLUSIONS: The results provide evidence of a significant reduction in numbers of intestinal cryptal cells passing through mitosis at specific time periods after a single administration of BB-10010. By putting these cells temporarily out of the mitotic phase of the cell cycle this protein might reduce the side effects of radiation therapy to patients undergoing abdominal or pelvic treatments.
mRNA prepared from rat small intestine was injected into Xenopus oocytes. The injected oocytes showed a clear electrical response to D-glucose (Glu) in the form of membrane depolarization and conductance increase, while none was shown to D-fructose. The membrane electrical response of the injected oocytes evoked by Glu followed the Michaelis-Menten type kinetics and was dependent on the membrane potential of the oocyte. Replacing the Na+ of the bathing buffer with choline+ resulted in no response to Glu. Thus, a Glu transport system coupled to a Na+ gradient was expressed in Xenopus oocytes by injecting mRNA from rat small intestine.
In the small intestine cell differentiation from immature crypt cells to mature absorptive cells localized along the villi is accompanied by alterations in the organization of the trans Golgi side. In immature crypt cells the transmost Golgi cisterna is usually located closely adjacent to the other cisternae thus being a component of the stack. Concomitantly with cell differentiation the transmost cisterna of an increasing number of Golgi stacks sets off from the other cisternae being then located at various distances to the stacks. This transmost cisterna has, as in several other cell types, been interpreted as "GERL" (Golgi associated endoplasmic reticulum lysosomes [20, 28]) and thus, has been postulated to represent a specialized region of the endoplasmic reticulum. Our results, however, have shown that the cytochemical staining pattern which has been used as a basis for the differentiation of GERL from Golgi components is not present in crypt cells nor in mature absorptive cells of the proximal small intestine: identical cisternae react for thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase. Thiamine pyrophosphatase and inosine diphosphatase--enzymes characteristic for Golgi cisternae--are apparent over transmost cisternae defined as GERL, too, and in addition, acid phosphatase--postulated as GERL-marker--is demonstrable over stacked Golgi cisternae. This overlapping cytochemical reaction, as well as the alterations during cell differentiation, indicate that those structures which have been described as GERL are to be interpreted as Golgi components rather than as endoplasmic reticulum. On the other hand, endoplasmic reticulum is a constant component of the trans Golgi face in undifferentiated crypt-base cells and in maturing cells of the crypt-top region. From its localization closely adjacent to trans Golgi cisternae it may be termed "Golgi-associated endoplasmic reticulum"; however, these cisternae of endoplasmic reticulum are constantly devoid of acid phosphatase. No indications exist for continuities with the thiamine pyrophosphatase-, inosine diphosphatase-, and acid phosphatase-positive transmost Golgi cisternae, and for an engagement in production of lysosomes.
Proximal and distal rat small intestine was cut into strips measuring 6.0 X 10.0 mm. Strips cut along the oral-caudal axis were called longitudinal strips, whereas those cut 90 degrees to that axis were called circular strips. Stress in circular and longitudinal muscle strips was measured continuously as they were superfused with acetylcholine, carbamylcholine, methacholine, bethanechol, or physostigmine. Resting stress during stretch, acetylcholine-stimulated active stress, and total stress were determined. Proximal circular muscle was five times as sensitive to acetylcholine as distal circular muscle (p less than 0.05); proximal longitudinal muscle was 2.8 times as sensitive to bethanechol as distal muscle (p less than 0.05). Resting, active, and total stress were similar in proximal and distal muscle, but circular muscle showed nearly twice the resting stress of longitudinal muscle at either proximal or distal sites (p less than 0.05). Physostigmine (10(-6) M) increased acetylcholine-stimulated active stress in proximal and distal circular muscle by 29% and 70%, respectively (p less than 0.05), but not in longitudinal muscle (p greater than 0.05). This difference between proximal and distal circular muscle (41%) was also significant (p less than 0.05). Thus, the proximal and distal muscle of the rat small intestine differs in its sensitivity to various cholinergic agonists, but not in its length-stress properties.
Segments of small intestine (duodenum, jejunum and ileum) from slaughtered reindeer (Rangifer tarandus tarandus) grazing natural winter pastures (n=3) and reindeer fed commercially available pellets (RF-80) in winter (n=5) were collected and immediately fixed in McDowell's fixative. Transmission electron microscopy was employed to investigate the ultrastructural features of the epithelium and lamina propria along the small intestine and to relate these to the different diets. Major differences in ultrastructural features were observed between the small intestinal enterocytes of reindeer fed the two diets. Enterocytes in reindeer fed the natural diet displayed a normal appearance with a dense cytoplasm and distinct microvilli. In contrast, reindeer fed the commercial diet showed damaged enterocytes amongst the normal cells. Abnormal changes included disintegration and loss of microvilli, cytoplasmic swelling, loss of membrane integrity and increases in the width of intercellular spaces, especially in the jejunum.
The regional small intestinal permeability to the vasopressin analogue desmopressin (dDAVP) was further characterized in proximal jejunal and distal (ileocecal) segments of the rat. Administration of the peptide to closed small intestinal loops confirmed the existence of regional absorption differences also in vivo in rats. Thus, the extent of absorption was about 4 times as high from the ileocecal part of the small intestine. The mucosal to serosal passage of dDAVP was studied in small intestinal segments from rats, mounted in Grass diffusion chambers. Increasing the mucosal concentration of dDAVP 100-fold had no effect on permeability coefficients (Papp) and the regional permeability distal:proximal ratio was maintained. Excessive amounts of unlabeled dDAVP to reduce the passage of [3H]dDAVP had no effect either. These findings make the existence of an active, receptor-mediated transport mechanism unlikely, and dDAVP probably does not affect its own transport rate. The higher ileocecal permeability could either be due to the presence of more permeable or dynamic pores in this region, where the epithelial surface area is smaller, or to an increased capacity for paracellular water flux. These results may have relevance for drug transport in the small intestine, where site-specific delivery of drug or enhancing agents may be optimized.
The adult mouse small intestinal epithelium undergoes perpetual regeneration, fueled by a population of multipotential stem cells and oligopotential daughters located at the base of crypts of Lieberkühn. Although the morphologic features of small intestinal epithelial progenitors (SiEPs) are known, their molecular features are poorly defined. Previous impediments to purification and molecular characterization of SiEPs include lack of ex vivo clonigenic assays and the difficulty of physically retrieving them from their niche where they are interspersed between their numerous differentiated Paneth cell daughters. To overcome these obstacles, we used germ-free transgenic mice lacking Paneth cells to obtain a consolidated population of SiEPs with normal proliferative activity. These cells were harvested by laser capture microdissection. Functional genomics analysis identified 163 transcripts enriched in SiEPs compared with Paneth cell-dominated normal crypt base epithelium. The dataset was validated by (i) correlation with the organellar composition of SiEPs versus Paneth cells, (ii) similarities to databases generated from recent mouse hematopoietic and neural stem cell genome anatomy projects, and (iii) laser capture microdissectionreal-time quantitative RT-PCR studies of progenitor cell-containing populations retrieved from the small intestines, colons, and stomachs of conventionally raised mice. The SiEP profile has prominent representation of genes involved in c-myc signaling and in the processing, localization, and translation of mRNAs. This dataset, together with our recent analysis of gene expression in the gastric stem cell niche, discloses a set of molecular features shared by adult mouse gut epithelial progenitors.
While prostaglandins of the E series are known to affect several small intestinal functions, their cellular mechanisms are poorly understood. The purposes of this study were to determine if there are developmental differences in the binding of PGE1, to the small intestinal enterocyte and if this binding may be affected by glucocorticoids, which are known to accelerate maturation of the small intestine. Small intestinal binding of prostaglandin E1 was significantly higher in adult rats when compared to postweaned (25-day-old) and preweaned (15- to 17-day-old) rats. Hydrocortisone administration for two days had no effect on the binding of prostaglandin E1 in either preweaned of adult rats. We conclude that a developmental change occurs in prostaglandin E1 binding to the plasma membrane of the rat small intestinal enterocyte during maturation. This binding is not affected by the administration of hydrocortisone.
Effects of IFN-gamma on mammalian small intestinal ion transport were studied in vitro using incubated sheets of murine small intestine in Ussing chambers. In oxygenated standard culture medium containing hydrocortisone and antibiotics, they maintained their short-circuit current (I(sc)) responses to glucose and theophylline for 48 h. Histological examination revealed a 50% diminution of villus height over 36 h but no change in crypts. Height was better maintained during a 36-h incubation of small intestine from SCID mice, suggesting a role for B or T lymphocytes in villus atrophy. Exposure of small intestine to 100 U/ml IFN-gamma for 36 h decreased basal I(sc) by 40% and I(sc) responses to glucose and theophylline by approximately 70%; at 1,000 U/ml for 36 h, IFN-gamma inhibited these I(sc) responses by 90%. An inhibitor of inducible NO synthase did not reverse these effects, suggesting that they are not mediated by NO. Tissue resistance, mucosal K(+) content, and epithelial morphology were not affected. Ouabain-sensitive ATPase activity in homogenates was inhibited 60% by IFN-gamma (100 U/ml for 36 h). IFN-gamma inhibition of I(sc) responses to glucose and theophylline also occurred in SCID mouse small intestine. Thus murine small intestinal sheets can be maintained viable in vitro for at least 48 h, although villus blunting develops (but less so in SCID mouse small intestine). Also, prolonged exposure to IFN-gamma downregulates Na(+)-coupled glucose absorption, active Cl(-) secretion, and Na(+)-K(+)-ATPase activity, effects unlikely to be mediated by enhanced NO.
The motility of the small intestine in unanesthetized rats receiving berberine sulfate (0.2, 2.0, and 20.0 mg/kg i.p.) was investigated. Motility was determined by two methods: myoelectric activity was monitored with indwelling bipolar electrodes, and intestinal transit was measured by the movement of radiochromium (Na51CrO4). The 20.0-mg/kg dose caused a marked inhibition of spike activity for 21.8 +/- 7.0 min and disrupted activity fronts of the migrating myoelectric complex for 212.3 min. Berberine, 2.0 mg/kg i.p., disrupted migrating myoelectric complexes for 64.6 min but spike inhibition was not observed. Transit of the small intestine was significantly (p less than 0.001) delayed at 15 and 100 min after the highest dose of berberine. Naloxone blocked the spike inhibition noted with 20.0 mg/kg of berberine but failed to improve transit. Phentolamine blocked spike inhibition and was associated with a significantly earlier return of activity fronts of the migrating myoelectric complex. Animals pretreated with this antagonist tended toward a higher geometric center in transit studies than those injected with berberine alone. Berberine was also administered by various routes (intraperitoneal injection, intravenous injection, orogastric gavage, and intraluminal injection). An intraperitoneal injection was 10-fold more potent than an intravenous injection. Orogastric gavage and intraluminal administration of berberine did not alter intestinal motility. In summary, berberine sulfate significantly inhibits myoelectric activity and transit of the small intestine. This appears to be partially mediated by opioid and alpha-adrenergic receptors. The antidiarrheal properties of berberine may be mediated, at least in part, by its ability to delay small intestinal transit.
Small intestinal resection (SIR) is not uncommonly done in surgical treatment of equine colic, but little is known about the long-term effects of SIR on horses and ponies. Twelve ponies, fed maintenance amounts of pelleted feed, were divided randomly into 4 treatment groups. D-Xylose absorption curves were recorded for each pony before surgical treatments were performed. Treatments consisted of control (ileal bypass) and 40%, 60%, or 80% SIR. D-Xylose absorption, serum electrolyte, and enzyme profiles for each animal were recorded once every 30 days for 180 days after surgical treatment, and the ponies were weighed every 2 weeks. The ponies then were necropsied and the remaining small and large intestine were examined. D-Xylose absorption values were depressed (P less than 0.05) in the ponies subjected to 40%, 60%, and 80% SIR as compared with the absorption values of the controls. The ponies with the 60% and 80% SIR lost body weight throughout the experimental period, whereas the controls and the ponies with 40% SIR maintained their base-line (presurgical manipulation) weight. Serum alkaline phosphatase activity was increased (P less than 0.05) in the ponies subjected to 60% and 80% SIR and significant biliary hyperplasia was present in those with 80% SIR. Extensive (greater than or equal to 60%) SIR severely compromised the capability of ponies to absorb nutrients and to derive adequate nutrition from a maintenance diet, resulting in changes in hepatic parenchyma and elevations in serum alkaline phosphatase. These changes are consistent with those reported in other species following SIR.