Studies on L-arginase of the small intestine. I. Topographical distribution and some properties of the small intestine L-arginase in the rat.
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Animals↗
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Characterization of small intestinal neuroendocrine tumorlets.
Small intestine neuroendocrine tumors (SI-NETs) frequently present as multifocal primaries. We commonly observe microscopic lesions in the superficial layer of the small intestine of SI-NET patients. We aimed to define them as small intestinal neuroendocrine tumorlets (SINTs) and explore their clinical and biological significance. Twenty multifocal and twenty unifocal SI-NETs patients who received resection at a single institution were retrospectively reviewed. Four hundred and forty six archived pathological slides were examined for microscopic lesions located in the lamina propria, muscularis mucosa, and superficial submucosa. Clinicopathological associations and progression-free survival were analyzed. Previously published genomic data were re-analyzed. SINTs were identified in 50% of multifocal and 30% of unifocal SI-NET patients. Median SINT size was 95 μm, with a median distance of 2.2 mm from the nearest mass. Compared to the 'true unifocal' group (unifocal without SINT), the 'multifocal-spectrum' group (multifocal or unifocal with SINT) had higher BMI (median: 27.6 vs 22.8, P = 0.0060), higher rates of perineural invasion (OR: 5.5, P = 0.044), larger mesenteric mass (median: 2.6 vs 1.6 cm, P = 0.034), and more advanced pT stage (pT3 or pT4, OR: 7.2, P = 0.018). Genomic re-analysis suggested that 13% of cells in multifocal primary tumors could share clonal origins, possibly indicating clonal spread via SINTs. SINTs may serve as a new biomarker for multifocal spectrum with local aggressiveness. The actual frequency of multifocal SI-NET may be higher than currently recognized in clinical practice. Further studies are needed to validate their prognostic and biological significance.
Humans↗
The assay and partial characterization of macromolecular heparin depolymerase activity in rat small intestine.
Homogenates of rat small intestine can depolymerize macromolecular rat skin heparin (RS heparin) to products similar in size to commercial heparin [Horner (1972) Proc. Natl. Acad. Sci. U.S.A. 69, 3469--3473]. This activity is attributed to an enzyme provisionally named 'macromolecular heparin depolymerase'. An assay for macromolecular heparin depolymerase activity in rat small intestine has been developed, based on the action of the enzyme on 35S-labelled macromolecular RS heparin. The depolymerized products are separated into two peaks by gel chromatography through columns of Bio-Gel A-15m. The amount of label in the second peak, expressed as a percentage of the total radioactivity, is the index of enzyme activity. The pH optimum was found to be 6.0 and the temperature optimum 45 degrees C. The enzyme was shown to be most stable in 50mM-Tris/maleate buffer containing 1 mM-EDTA. Macromolecular heparin depolymerase activity measured as a function of time and substrate concentration produced curves typical of an enzymic reaction. Evidence was obtained demonstrating that the activity did not originate from bacteria in the intestine. Macromolecular heparin depolymerase activity was increased by dilution and storage at 7 degrees C for 24 h. This suggests that homogenates of rat small intestine contain an unstable inhibitor of the enzyme.
Animals↗
Biochemical properties of some microsomal xenobiotic-metabolizing enzymes in rabbit small intestine.
Comparison of xenobiotic-metabolizing enzymes in rabbit small intestinal and hepatic microsomal fractions showed mainly quantitative differences; most of the activities were two to seven times higher in liver than in intestine. However, UDP-glucuronyltransferase activity was higher in intestine than in liver. The apparent absence of benzene hydroxylase in small intestine was the only qualitative difference noticed. Aniline hydroxylase, aminopyrine N-demethylase, and aryl hydrocarbon dydroxylase were characterized in intestinal microsomes and compared to those of liver. Distribution of these enzymes along the entire length of small intestine showed that maximum activities of the enzymes were present in the proximal 60 cm of the intestine. All the enzymes in both tissues required NADPH and O2 for maximum activity and were inhibited by cytochrome c, SKF 525-A, and CO. The in vitro addition of drug substrates to microsomal fractions of both tissues produced typical type I and type II binding spectra. Comparison of the relationships between activities and pH, duration of incubation, and substrate and protein concentration suggested that the rabbit intestinal and hepatic xenobiotic-metabolizing enzymes studied have similar characteristics.
Aminopyrine N-Demethylase↗
Electron microscopic studies on the small intestine of rats after mechanical intestinal obstruction.
The morphologic changes of the small intestine after the mechanical obstruction were studied by light and electron microscopy. After the ligation of the upper small intestine, segments of jejunum, both proximal and distal to the site of obstruction, were removed at intervals varying from 45 min to 24 h. The essential changes were found in the epithelial cells of the tips of villi, and few morphologic differences were recognized between samples proximal and distal to the site of obstruction. The most remarkable changes in the mucosa were the pseudopodlike extension of the cytoplasm, vacuolar alteration of the villus epithelial cells, desquamation of these degenerated cells, and the dilatation of the epithelial intercellular spaces. A few epithelial cells showed hypertrophy of the smooth endoplasmic reticulum. In the submucosa, vascular stasis and edema were observed throughout the course. The mechanism of fluid loss into the intestinal lumen was discussed briefly.
Animals↗
Effects of local delayed hypersensitivity on the small intestine.
There are many T and B cells in the small intestinal mucosa and local T cell immunity could have a role both in protective immunity and as a cause of disease (i.e. hypersensitivity). This latter aspect has been investigated by using several animal models to assess the effects of local delayed hypersensitivity on the structure and function of the small intestine. Heterotopically transplanted grafts of fetal small intestine in mice (isografts and allografts) have been examined by conventional histology, scanning and transmission electron microscopy, by making direct measurements of villi, crypts, and lymphoid cell infiltrate, and by counting the number of mitoses per crypt. This cell-mediated immune reaction causes lymphocyte infiltration which is most marked in the lamina propria, hyperplasia of the crypts of Lieberkühn, increased cell loss with villous atrophy and a flat surface, but the individual enterocytes appear fairly normal. Graft-versus-host disease cause exactly the same changes in structure and in cell kinetics as does rejection. However, crypt hyperplasia has been found to precede villous atrophy by several days. Preliminary experiments on local contact hypersensitivity suggest that intraluminal injection of oxazolone in the gut of sensitized mice also produces villous atrophy and crypt hyperplasia. It is postulated that these effects are likely to be produced via lymphokines: by an 'enteropathic' factor which damages the lamina propria and basement membrane, and a factor which is mitogenic for crypt stem cells. In mice infected with Giardia lamblia, crypt hyperplasia and lymphocyte infiltration of the epithelium are present and there is accelerated epithelial cell turnover. In rats infected with Nippostrongylus brasiliensis, the flat mucosa has been shown to be due to the thymus-dependent immune response and not directly to the damage produced by the parasite itself. A common factor in the variety of conditions associated with villous atrophy and crypt hyperplasia may well be a local cell-mediated immune reaction to food, microbial, parasite or other antigens which causes changes in enterocyte turnover rate and malabsorption.
Animals↗
Characteristics and postnatal development of the acid lipase activity of the rat small intestine.
Acid lipase was identified in the rat small intestine by using esters of 4-methylumbelliferone as substrates. Maximum activity towards the oleate ester was found at pH 4.0. In adult animals, the activity of acid lipase exhibited both latency and sedimentability, indicating a lyosomal localization. The activity of acid lipase was practically the same along the height of the villus, thus paralleling the distribution of acid beta-galactosidase. In adult rats, the activity of acid lipase in proximal (jejunum) and middle (mid-jejunum) sections of the small intestine was practically the same and exceeded the activity in the distal (ileum) section by a factor of 2. In suckling rats, the activity of the enzyme in the mid-jejunum exceeded that in the jejunum and ileum by 2.5- and 1.5-fold respectively. During postnatal development, the acid lipase activity of the mid-jejunum showed a peak between days 10 and 15, at which time it exceeded the adult mid-jejunum activity by 5--6-fold.
Aging↗
Preservation of various microsomal drug metabolizing components in tissue preparations from the livers, lungs, and small intestines of rodents.
The livers, lungs, and small intestines of untreated rabbits and the livers of control rats were stored intact, or as microsomal suspensions, under liquid nitrogen at -196 degrees C. Aniline hydroxylase, aminopyrine demethylase, benzpyrene hydroxylase, biphenyl hydroxylase, NADPH-cytochrome c reductase, UDP-glucuronyltransferase activities, the microsomal content of cytochrome P-450, and the aniline- and benzphetamine-induced spectral changes were compared in fresh and stored preparations. Few significant changes in any of the above parameters resulted from storage of rabbit tissue preparations in liquid nitrogen for periods of up to 28 days. Pretreatment of rabbits with phenobarbital did not affect the stability of their stored microsomal preparations. Enzyme activities in the livers of untreated or 3-methylcholanthrene-pretreated rats were less stable to storage than in tissue preparations from rabbits stored under identical conditions. However, when rat hepatic microsomes were resuspended in KCl-HEPES supplemented with 1 mM EDTA before storage, enzyme activities were largely unaffected by freezing in liquid nitrogen.
Aminopyrine N-Demethylase↗
Involvement of the small intestine in systemic mast cell disease.
A patient is reported with mast cell infiltration of the small intestine in the absence of the skin involvement characteristic of mast cell disease. She also had subtotal villous atrophy responsive to a gluten-free diet. Criteria for diagnosing mast cell disease of the small intestine are proposed. The literature of small intestinal mast cell disease is reviewed and the relationship to coeliac disease is discussed.
Adult↗
Symposium on pathology of the gastrointestinal tract-Part II. Small intestinal biopsy.
A practical approach to the interpretation of peroral small intestinal biopsy specimens is presented. Biopsy technique and tissure handling are described. Interpretation of normal and abnormal biopsy specimens is discussed. A practical classification of abnormal small intestinal biopsies is presented and illustrated.
Abetalipoproteinemia↗
[Glucose transport across the mucosa of the small intestine].
The rate of glucose absorption in an isolated loop of the small intestine in rats was measured. The maximum rate of absorption was registered with 3 and 5 per cent concentrations, while 1 and 10 per cent solutions are absorbed at a slower rate. The absorption rate of 5 per cent glucose solution did not materially change for one hour after a sugar load. The small intestine mucosa transports glucose from a 5 per cent solution at an equal rate in rats and rabbits, i. e. 139+/-4 and 143+/-6 gamma/cm2/min. Maximum absorption takes place with pH of 6-8. Deviation of the pH value to acidity and alkalinity is attended by steep fall in the absorption rate. At pH of 3.0 and 11.5 the absorption virtually ceases altogether. Hexobarbital anesthesia depresses absorption of glucose in the intestine by a factor of 2-3.5.
Animals↗
Postnatal development of mixed-function oxidation as measured in microsomes from the small intestine and liver of rabbits.
The postnatal development of aminopyrine N-demethylase, aniline 4-hydroxylase, benzpyrene hydroxylase, biphenyl 4-hydroxylase, 7-ethoxycoumarin 0-deethylase activities, NADPH-cytochrome c reductase, and cytochrome P-450 was compared in microsomes from the liver and small intestine of New Zealand white rabbits. Apart from hepatic aniline hydroxylase activity, all of the xenobiotic-metabolizing enzyme activities examined had a similar pattern of development in the liver and small intestine. In both tissues the ability to metabolize xenobiotics was generally undetectable at 2 days of age and remained relatively low for the first 20 days of life. Theresfter, a rapid 2- to 5-fold increase in all the enzyme activity studied was noted, and adult values were reached or exceeded by 30 days of age. Subsequent development of xenobiotic-metabolizing enzyme activities in the small intestine, but not in the liver, exhibited a transient fall at 50 days of age before adult activities were attained after 75 days of age. The developmental pattern of cytochrome P-450 in the small intestine closely resembled that of the xenobiotic-metabolizing enzyme activities, but in the liver this correlation was less exact.
Aging↗
Small intestinal sugar and amino acid transport in semistarvation.
The effect of semistarvation on small intestinal transport of D-glucose, L-valine, and NaCl was studied in an in vitro system of isolated rat brush border membrane vesicles. Whereas semistarvation enhanced the transport rate for L-valine by 19-29%, there was no change in D-glucose transport. When energy in the form of a NaSCN gradient was supplied to the membrane vesicles prepared from semistarved animals, L-valine was concentrated to a greater extent than those from well-fed animals. Strain differences were observed in the manner semistarvation affected NaCl transport across the brush border membrane. Semistarvation increased the NaCl transport rate by a factor of 3.5 in one rat strain and not at all in another. These results provide a partial explanation for the cellular basis of elevated neutral amino acid absorption by the small intestine in semistarvation.
Amino Acids↗
Comparison of human membrane-bound neutral arylamidases from small intestine, lung, kidney, liver and placenta.
Human membrane-bound neutral arylamidases were solubilized from small intestinal mucosa, lung, kidney, liver and placenta with trypsin. These five membrane-bound neutral arylamidases were identified by polyacrylamide gel-disc electrophoresis. The heat sensitivity of each enzyme was in the order, liver and placenta greater than kidney greater than lung greater than small intestine. This order correlates with that of electrophoretic mobility, except for the placental membrane-bound neutral arylamidase. Five membrane-bound neutral arylamidases have the same molecular weight, 240 000, as estimated by Sephadex G-200 gel filtration. The five membrane-bound neutral arylamidase have very similar KM values (8.7 x 10(-5) M towards L-alanyl-beta-naphthylamide), optimal pH values, hydrolysis ratios towards L-alanyl-beta-naphthylamide and L-leucyl-beta-naphthylamide, and sensitivities of inhibition by chelators or amino acids. These results suggest that the multiple forms of membrane-bound neutral arylamidase found in five different human organs are organ-specific isoenzymes.
Amino Acids↗
GI absorption of beta-lactam antibiotics. III: Kinetic evidence for in situ absorption of ionized species of monobasic penicillins and cefazolin from the rat small intestine and structure-absorption rate relationships.
Absorption rates of monobasic beta-lactam antibiotics were measured as a function of lumen solution pH between 4 and 9 by utilizing the rat intestinal recirculating method in situ. Between pH 6.5 and 9, the absorption rate constants of ionized antibiotics were almost identical; but, at pH 4, the unionized species were highly absorbed, depending on their lipophilicity through the GI membrane lipoidal barrier. The structure-absorption rate relationship was established with the unstirred layer model.
Animals↗
Distribution of intrinsic nerve cell bodies and axons which take up aromatic amines and their precursors in the small intestine of the guinea-pig.
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Animals↗
Influence of exocrine pancreatic insufficiency on the intraluminal pH of the proximal small intestine.
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Adult↗
Ion permeability and strength of cell contacts: ion permeability and mechanical properties of cell contacts in small intestine epithelium.
The effects of several simple parameters (pH, concentration of bivalent cations, osmotic pressure, and temperature) on the ion permeability and mechanical properties of cell contacts have been investigated. It has been shown that the mechanical properties of a cell contact make it possible to describe it as a viscoelastic system. The main contribution to cell adhesion is made by the tight junction. Two populations of acidic centers have been identified on the cell membrane surface. One population interacts with bivalent cations to assure cell adhesion. The other population of weaker acidic centers regulating ion permeation is involved in the cell membrane's interaction of the repulsion type. An intimate correlation has been established between changes in passive transepithelial ion permeability and cell adhesion in response to changes in pH and in bivalent cation concentration. Such a correlation is possible if the tight junction is the principal contributor to the passive ion permeability and mechanical strength of the cell contacts.
Animals↗