The influences of four types of soil on the growth, physiological and biochemical characteristics of Lycoris aurea (L' Her.) Herb.

Based on the characteristics of Lycoris aurea (L. aurea) natural distribution and local soil types, we selected four representative types of soil, including humus soil, sandy soil, garden soil and yellow-brown soil, for conducting the cultivation experiments to investigate key soil factors influencing its growth and development and to select the soil types suitable for cultivating it. We found that there existed significant differences in the contents of mineral elements and the activities of soil enzymes (urease, phosphatase, sucrase and catalase) etc. Among which, the contents of organic matters, alkali-hydrolysable nitrogen, Ca and Mg as well as the activities of soil enzymes in humus soil were the highest ones. In yellow-brown soil, except for Fe, the values of all the other items were the lowest ones. Net photosynthetic rate (Pn), biomass and lycorine content in humus soil were all the highest ones, which were increased by 31.02, 69.39 and 55.79%, respectively, as compared to those of yellow-brown soil. Stepwise multiple regression analysis and path analysis indicated that alkali-hydrolysable nitrogen, and Ca etc. were key soil factors influencing Pn, biomass and lycorine content of L. aurea. Thus, humus soil can be used as medium suitable for artificial cultivation of L. aurea.

Efecto del consumo de harina de avena (avena sativa) y frijoles negros (phaseolus vulgaris) sobre la actividad de las disacaridasas intestinales en ratas / Effect of the consumption of flour of oats (avena sativa) and black beans (phaseolus vulgaris) on the activity of intestinal disaccharidases in rats

Objetivo: En este trabajo se estudió el efecto de la ingesta crónica de harina de caraotas negras y harina de avena sobre la actividad de las disacaridasas intestinales en ratas. Metodología: 15 ratas Sprague Dawley, con un peso inicial promedio de 85g se dividieron en tres grupos, un grupo control sin fibra, un grupo alimentado con harina de caraotas negras y un grupo con harina de avena por 21 días. Los animales fueron sacrificados, el intestino delgado se dividió en tres porciones (proximal, media, y distal), y se obtuvo un homogenato por raspado de la mucosa. Resultados: La actividad de las disacaridasas se estimó mediante la determinación de glucosa por un método enzimático con peroxidasa. El orden de actividad enzimática fue Maltasa > Sacarasa > Lactasa, obteniéndose una mayor actividad en la región intestinal media para cada disacaridasa. El consumo de harina de caraotas produjo un incremento significativo en la actividad de la maltasa y sacarasa, en esta última, de más de un 100% en relación con el control. La suplementación de las dietas con avena produjo una disminución de la actividad de la sacarasa de un 40% y no produjo ningún efecto sobre la actividad de la maltasa y lactasa. Conclusiones: Estos resultados señalan que el efecto que produce la ingesta crónica de fibra dietética sobre la actividad de las disacaridasas intestinales no se puede generalizar, cada enzima reacciona de manera particular frente a cada tipo de fibra, y puede variar además, según el segmento del intestino delgado estudiado (AU)

Objective: In this work was studied the effect of chronic intake of black beans flour and oat flour on the activity of the intestinal disaccharidases in rats. Methodology: 15 Sprague Dawley rats, with an initial average weight of 85g were distributed, into three groups, a fiber free control group, a group fed with black beans flour and a group with oat flour for 21 days. Then, the rats were sacrificed and the small intestine was divided into three sections (proximal, medial, and distal). The homogenate was obtained by scraping the mucosa of each section. Results: The activity of the disaccharidases was estimated by the glucose determination using peroxidase enzymatic method. The order of enzyme activity was maltase> Sucrase > lactase, obtaining a greater activity in the middle intestinal region for each disaccharidase. The consumption of beans flour produced a significant increase in the activity of maltase and sucrase, the latter, with more than 100% in relation to control. Diets with oats supplementation resulted in a decrease of 40% sucrase activity and did not produce any effect on the activity of maltase and lactase. Conclusions: These results indicate that the effect of chronic dietary fiber intake on the activity of intestinal disaccharidases cannot be generalized, each enzyme reacts in a particular way to each type of fiber and may also vary according to the segment of the small intestine (AU)

Effects of Hull Scratching, Soaking, and Boiling on Antinutrients in Japanese Red Sword Bean (Canavalia gladiata).

The effects of hull processing, soaking, and boiling on the content or activity of antinutrients in the red sword bean (RSB; Canavalia gladiata) were investigated. RSB seeds were compared with kidney bean (KB; Phaseolus vulgaris) seeds that are starch based and often used as processed products in Japan. RSB seeds had higher weight, thicker hull, and higher protein content, but lower moisture content compared with KB seeds. Because of the strong and thick hull, the relative water absorption of untreated RSB seeds was very low after soaking. Seeds were soaked after dehulling, scratching, and roasting. The results showed that hull scratching was the optimal method for increasing water absorption during soaking compared with dehulling and roasting. After soaking, the water used for soaking was discarded, since it had a high content of polyphenols and bitter taste, and RSB seeds were boiled in fresh water for 20, 40, and 60 min. The results showed that polyphenol and tannin contents, antioxidant activity, and hemagglutinating activity, as well as maltase, sucrase, and trypsin inhibitor activities in scratched RSB seeds decreased significantly after boiling compared with those in raw seeds, whereas amylase inhibitor activity showed no significant change. Overall, it was concluded that the combination of hull scratching, soaking, and boiling in fresh water can reduce thermal-stable or sensitive antinutrients in RSB and thus, significantly improve its nutritional value.

[Effects of heavy metals pollution on soil microbial communities metabolism and soil enzyme activities in coal mining area of Tongchuan, Shaanxi Province of Northwest China].

This paper studied the metabolism of soil microbes, functions of soil microbial communities, and activities of soil enzymes in a coal mining area of Tongchuan. In the coal mining area, the concentrations of soil Cu, Zn, Cd, and Pb were significantly higher than those in the non-mining area, of which, Cd contributed most to the heavy metals pollution. By adopting Biolog method combining with principal component analysis (PCA) and cluster analysis, it was found that the metabolic characteristics of different soil microbial communities varied significantly with increasing soil heavy metals pollution, and the variation was mainly manifested in the metabolic patterns of carbon sources such as saccharides and amino acids. In slightly and moderately polluted soils, the utilization of carbon sources by soil microbial communities was activated; while in heavily polluted soils, the carbon sources utilization was inhibited. The activities of soil urease, protease, alkaline phosphatase, and catalase all tended to decline with intensifying soil heavy metals pollution. The soil urease, protease, alkaline phosphatase, and catalase activities in the coal mining area were 50.5%-65.1%, 19.1%-57.1%, 87.2%-97.5%, and 77.3%-86.0% higher than those in the non-mining area, respectively. The activities of soil sucrase and cellulase were activated in slightly and moderately polluted soils, but inhibited in heavily polluted soils.

Restoration of mechanically lengthened jejunum into intestinal continuity in rats.

PURPOSE: Prior studies demonstrated the feasibility of lengthening intestinal segments with mechanical force, but no previous studies have restored the lengthened segment back into intestinal continuity. METHODS: A 1-cm segment of isolated rat jejunum was lengthened using a Nitinol spring. After lengthening, this segment was restored into intestinal continuity via a transection of the intact small intestine. Rats were euthanized 2 weeks later to retrieve the restored intestinal segment for histologic and enzymatic analyses. RESULTS: The isolated jejunal segments were initially lengthened to 3.3 ± 0.9 cm. After the lengthened segments were restored into intestinal continuity for 2 weeks, the final length of the restored segment was 1.9 ± 0.7 cm. All rats continued to gain weight, and the intestine proximal to the restored jejunal segment remained normal 2 weeks later. The restored jejunal segment had an increase in crypt depth and no difference in villus height compared with normal jejunum. Sucrase activity in the restored segment was not different from that in normal jejunum. CONCLUSION: Mechanically lengthened jejunum can be restored into intestinal continuity and appears to have normal function. This further demonstrates the feasibility of mechanical enterogenesis as a potential therapy for short bowel syndrome.

Disaccharidase deficiency in pediatric patients with celiac disease and intact villi.

BACKGROUND AND AIMS: The "gold standard" for the diagnosis of celiac disease (CD) is the small intestinal biopsy. A significant number of biopsies are inadequate for interpretation. Furthermore, the labeling of a biopsy as a Marsh I or II is somewhat subjective and may vary with the experience of the pathologist. Our hypothesis is that patients with intact villi undergoing biopsies frequently have associated disaccharidase deficiencies (DSD). METHODS: We reviewed 220 charts of pediatric patients with CD and selected those with a duodenal biopsy Marsh score of I/II. The disaccharidase (DS) levels of these patients were compared with a randomly selected, age-matched control group. DSD is defined as levels below the lower limits of normal. RESULTS: Lactase (mean lactase = 18.8 in the control group vs. 4.2 in the diseased group, p = 0.004); sucrase (mean sucrase = 46.4 in the control group vs. 21.4 in the diseased group, p = 0.001); maltase (mean maltase = 138 in the control group vs. 52.5 in the diseased group, p = 0.001); palatinase (mean palatinase = 9.6 in the control group vs. 3.3 in the diseased group, p < 0.001). CONCLUSION: There is a profound deficiency of DS levels in pediatric patients with CD who have intact villi.

Effect of andrographolide on cysteamine-induced duodenal ulcer in rats.

The aim of this study was to evaluate the gastroprotective efficacy of andrographolide isolated from Andrographis paniculata in rats induced with duodenal ulcers. Duodenal ulcers were induced by cysteamine administration in rats pretreated with 3 mg kg⁻¹ BW day⁻¹ of andrographolide for 30 days. Ulcer score, myeloperoxidase activity, TBARS level, GSH/GSSG ratio and enzyme antioxidants were measured in the duodenal tissue. Brush border and basolateral membranes were isolated to assay sucrase, maltase, alkaline phosphatase and total ATPases. Ulcer score was significantly minimised in rats pretreated with andrographolide. Elevation in myeloperoxidase and TBARS levels were found to be minimised significantly due to andrographolide treatment. Membrane-bound enzyme activities and the thiol redox status of glutathione were significantly maintained in duodenal mucosa of rats that received andrographolide. This study reveals that the major component of A. paniculata, andrographolide, has potent antiulcer properties that are most likely caused by minimising inflammatory changes, counteracting free radical formation and maintaining the thiol redox status in the duodenum.

High-throughput tissue homogenization method and tissue-based quality control materials for a clinical assay of the intestinal disaccharidases.

BACKGROUND: The definitive biochemical test for the diagnosis of disaccharidase deficiencies is the determination of enzyme activities in small bowel mucosa. Traditional methods of tissue homogenization are limited by low throughput. Lack of tissue-based quality control materials is a limitation for clinical laboratories that perform tests of the intestinal disaccharidases. The objectives of this study were to develop a method for determining disaccharidase activities using a high-throughput homogenization method and to create matrix-appropriate quality control materials. METHODS: Intestinal mucosa was homogenized using three different methods. Activities of lactase, maltase, palatinase, and sucrase were determined by measuring glucose liberated from a hydrolysis reaction with disaccharide substrates and normalized to total protein concentration. Tissue-based quality control materials were developed from pig intestine and pooled clinical specimens. RESULTS: A high-throughput homogenization method processed 24 specimens in 2 min compared to 1 specimen per 2 min for traditional methods. There were no significant differences (p>0.90) in enzyme activities as a function of the homogenization method used. 92 determinations of enzyme activities from 23 clinical specimens showed acceptable agreement (y=1.13x-6.6) and were highly correlated (r=0.95) as compared to results obtained by an external laboratory. Enzyme activities were variably inactivated by temperatures > or = 60 degrees C. Pig intestinal mucosa produced non-deficient enzyme activities while deficient activities were produced by combining equal volumes of unheated and heat-inactivated homogenates pooled from clinical specimens. CONCLUSIONS: A high-throughput method of tissue homogenization was more efficient than traditional methods and did not affect enzyme activities. Matrix-appropriate quality control materials can be created from pig intestine and pooled human homogenates.

The effect of diets containing soybean meal, soybean protein concentrate, and soybean protein isolate of different oligosaccharide content on growth performance and gut function of young turkeys.

An experiment was conducted to investigate the effects of diets containing soybean meal (SBM), soybean protein concentrate (SPC), and soybean protein isolate (SPI) on growth performance and gut function of the young turkey. A total of 812 one-day-old male turkey poults were randomly assigned to 4 dietary treatments, with 7 pens per treatment and 29 birds per pen. The 4 experimental diets contained SBM, SBM-SPC, SPC, and SPI and were fed throughout the two 4-wk experimental periods. In each period, the diets were isonitrogenous and isocaloric and contained similar amounts of total and water-soluble nonstarch polysaccharides. The content of oligosaccharides differed among the diets and averaged 2.4, 1.9, 0.9, and 0.1% for SBM, SBM-SPC, SPC, and SPI, respectively. When compared with SBM, birds consuming the SBM-SPC and SPC diets had higher (P<0.05) final BW (4.32 vs. 4.45 and 4.46 kg, respectively). Incorporation of SPI as a substitute for SBM resulted in improved (P<0.05) feed utilization (from 1.76 to 1.67) but did not affect the final BW. Significant changes in cecal concentrations of short-chain fatty acids were observed and averaged 130, 103, and 89 micromol/g of digesta for the SBM, SBM-SPC, and SPC diets, respectively. This coincided with the proportional decrease in dietary oligosaccharide content (from 2.4 to 0.9%) and was further substantiated by a significant decrease in ileum weights. Feeding the SPI diet resulted in the lowest ileal and cecal tissue weights as well as the lowest cecal short-chain fatty acids concentration. There was no effect of diet on digesta pH, viscosity, and mucosal sucrase and maltase activities. Bacterial beta-glucuronidase activity was decreased (P=0.08) in the cecum (from 0.98 to 0.60 U/g) with decreased dietary oligosaccharide content. In conclusion, partial or almost complete substitution of SBM with SPC suppressed the fermentation processes in the ceca but enhanced the growth rate. Substitution of SBM with SPI significantly improved feed utilization but decreased BW of 4-wk-old turkeys with no effect on growth rate of older 8-wk-old birds.

Oral administration of potassium dichromate inhibits brush border membrane enzymes and alters anti-oxidant status of rat intestine.

Potassium dichromate (K2Cr2O7) is a soluble hexavalent chromium compound that is widely used in several industries. In the present work the effect of administration of K2Cr2O7 on rat intestinal brush border membrane(BBM) enzymes and anti-oxidant system was studied. Rats were given a single oral dose of K2Cr2O7 (100 mg/kg bodyweight) and sacrificed 6, 12, 24, 48 and 96 h after the treatment.Control animals were not given K2Cr2O7. The administration of K2Cr2O7 resulted in a reversible decline in the specific activities of several BBM enzymes. The decrease in the activities of these enzymes was due to changes in the maximum velocity while their affinities for the substrates remained unchanged. Lipid peroxidation increased while total SH groups decreased in K2Cr2O7-treated rats as compared to controls indicating increased oxidative stress in the intestinal mucosa. The activities of superoxide dismutase and glutathione-S-transferase increased while those of catalase, glutathione reductase, thioredoxin reductase and glucose-6-phosphate dehydrogenase decreased. The maximum changes in all the parameters studied above were 24 h after administration of K2Cr2O7 after which recovery took place,in most cases almost to control values after 96 h. These results show that oral administration of K2Cr2O7 to decrease in the activities of BBM enzymes, increase in oxidative stress and alters the activities of anti-oxidant enzymes in rat intestine.

GLP-2 administration results in increased proliferation but paradoxically an adverse outcome in a juvenile piglet model of short bowel syndrome.

OBJECTIVE: The objective of the present study was to examine the effect of glucagon-like peptide-2 (GLP-2) administration in a piglet, juvenile model of short bowel syndrome. MATERIALS AND METHODS: Four-week-old piglets underwent either a sham operation or 75% small bowel resection. Postoperatively, piglets received either polymeric infant formula diet or the diet and subcutaneous human recombinant GLP-2 (1600 microg/day for 7 days, 800 microg/day thereafter). Food intake was monitored throughout the experiment, and stool and serum samples obtained fortnightly. After the piglets were killed, tissues were obtained from the duodenum, jejunum, ileum, and terminal ileum, and used for morphological and functional analysis. RESULTS: Treatment with GLP-2 resulted in significantly increased numbers of proliferating and apoptotic cells in the ileum of sham and small bowel resection piglets (P < 0.05). GLP-2 administration resulted in decreased weight gain, serum albumin, and disaccharidases in both sham and small bowel resection piglets (P < 0.001 compared with polymeric infant formula diet alone). CONCLUSIONS: This is the first study to our knowledge to examine the effect of GLP-2 administration in a juvenile short bowel syndrome model. Contrary to adult rodent studies, administration of GLP-2 resulted in adverse outcomes including reduced ability to gain weight; decreased serum albumin, tissue maltase, and sucrase; and villous atrophy. We anticipate this information will have important implications for future paediatric clinical trials.

Effect of bacterial monoassociation on brush-border enzyme activities in ex-germ-free piglets: comparison of commensal and pathogenic Escherichia coli strains.

This study was designed to investigate the effect of monoassociation of germ-free piglets with Escherichia coli strains on the development of intestinal brush-border enzyme activities. Piglets were delivered by hysterectomy, reared for seven days under germ-free conditions and fed milk formula diet. One group was maintained germ-free, the other four groups were monoassociated on day eight with one of four E. coli strains: non-pathogenic O86 or O83 and G58-1, or pathogenic 933D. The development of brush-border digestive enzyme functions in the small intestine was evaluated after 15 days. Germ-free controls exhibited slower developmental declines of lactase, gamma-glutamyltranspeptidase and alkaline phosphatase, and delayed increases of sucrase and glucoamylase compared to conventionally grown animals. Association of germ-free piglets with the non-pathogenic E. coli strains O86 and O83 resulted in increased enterocyte differentiation along the length of the small intestine, accompanied by declining activities of lactase, gamma-glutamyltranspeptidase and alkaline phosphatase, and elevated activities of maturational markers such as sucrase and glucoamylase. Maturational changes also occurred along the villus-crypt axis, as revealed by histochemical localization of aminopeptidase N on the villi tips in piglets colonized with E. coli O83. Interestingly, colonization with the pathogenic E. coli strain 933D stimulated changes in the main differentiation enzyme markers lactase, sucrase and glucoamylase to an extent comparable with those produced by the non-pathogenic and probiotic E. coli strains. In conclusion, germ-free piglets represent a valuable tool to study the consequences of colonization of the immature sterile gut with defined strains of bacteria.

Relationship between protein deficiency in the ration of rats during early ontogeny and function of enzyme systems of digestive and non-digestive organs in adult life.

Low protein content in the ration of rat pups during transfer from mixed to definitive nutrition (days 21-30 of life) has a negative impact on digestive function of the small intestine and trophic and barrier functions of the large intestine, liver, and kidneys and increases (sucrase, glycyl-L-leucin dipeptidase) or decreases (alkaline phosphatase, aminopeptidase M, glycyl-L-leucine dipeptidase) enzyme activities in these organs in 6-month-old rats. Protein deficiency during the early ontogeny modulates functioning of the enzyme systems in digestive and non-digestive organs in adult life, which can lead to the development of not only gastrointestinal, but other visceral diseases.

Trophic status of the small intestine in young and aged rats: modulation by a yogurt-supplemented diet.

Among the multifactorial causes of undernutrition in old age, gastrointestinal mucosa altered function and resulting specific malabsorption are the most relevant. Despite numerous studies that have dealt with the effects of aging on the digestive tract of mammals, results showed discrepancies in terms of proliferation and biochemical aging small intestine events. However, the slowing-down of the maturation process and the poor adaptation of metabolism and intestinal function are obvious and there is evidence that protective mechanisms are impaired with age and contribute to affecting the trophic activity and related systemic homeostasis. Good prospects to improve gastrointestinal function in the elderly are essential and research on nutritional intervention to limit and counteract age-related impairments must be extensive. Probiotics are good candidates and fermented milks might be of great interest. In the present study we first show the main structural and functional variations between 3- and 23-month-old rat small intestines. The trophic consequences of aging and nutritional adaptation under basal conditions are also analyzed and discussed after 20 days of a yogurt-supplemented specific diet in both young and aged rats. The main variations that occur with aging and yogurt diet are located in the proximal small intestine. The present findings indicate a slight improvement of morphological trophic parameters in both young and aged rats by yogurt, whereas enzymatic changes are more discrete. Despite the obvious age-related decrease in trophicity, we suggest that assessment of probiotic potentials on trophicity requires a more altered model than normal, healthy aging animals.

A new continuous automated assay for the determination of intestinal lactase.

BACKGROUND: A reliable, sensitive and practicable method for the measurement of intestinal lactase activity is needed. METHOD: The assay is based on the continuous measurement of released glucose by a coupled hexokinase/glucose-6-phosphate dehydrogenase (HK/G6PDH) reagent. RESULTS: The procedure was first optimized for lactase from rat intestinal mucosa. The optimum pH is 6.5 and apparent Km was 17 mmol/l for lactose. The procedure was also adapted on a Cobas Mira automated analyzer; progress curves of the reaction rate can be continuously monitored. The automated assay correlated strongly with the conventional method of Dahlqvist (r(2) = 0.996). The described method has also been applied to human intestinal mucosa biopsies after determination of the catalytic properties of human enzyme (optimum pH 6.0 and apparent Km 34 mmol/l). CONCLUSION: The HK/G6PDH method is reliable, rapid, sensitive and easy to perform both manually as well as in the automated version. It is optimized for human and rat intestinal lactase.

Randomized controlled study of digestive enzyme activity following trophic feeding.

UNLABELLED: A randomized, controlled, prospective study of 80 preterm infants of birthweight less than 1750 g requiring ventilatory support was performed. While ventilatory support was required group TF (39 infants) received trophic feeding (0.5-1 ml h(-1)) along with parenteral nutrition, whereas group C (41 infants) received parenteral nutrition alone. When ventilatory support was no longer required milk feeds were started in group C and then increased in both groups until full milk feeds were established. The ratio of lactase to sucrase activity (L:S ratio) was measured in aspirated proximal intestinal fluid on 3 occasions: immediately after ventilatory support was withdrawn (T0), 7 days later (T7) and 14 days later (T14). On the same 3 occasions faecal chymotrypsin activity was measured. The mean difference (95% confidence interval) L:S ratio was significantly higher in group TF at both T0 and T14, 1.8 (0.03, 3.57) and 0.78 (0.2, 1.35) U l(-1), respectively. There was no significant difference in faecal chymotrypsin concentration. CONCLUSION: Trophic feeding alters relative intestinal disaccharidase activity, probably by inducing lactase production, but has no effect on pancreatic chymotrypsin activity.

Bifidobacterium bifidum monoassociation of gnotobiotic mice: effect on enterocyte brush-border enzymes.

The effect of intestinal colonization with Bifidobacterium bifidum (Gram-positive anaerobic bacterium colonizing the intestine of healthy new-born mammals, exhibiting a probiotic effect, protecting the intestinal mucosa against colonization by pathogenic microflora) on enterocyte brush-border enzymes was examined in weaned 23-d- and in 2-month-old gnotobiotic inbred mice and compared with that in corresponding germ-free (GF) and conventional (CV) controls. The two groups of GF mice were associated with human B. bifidum 11 d before the end of the experiment. Specific activity of enterocyte brush-border enzymes--lactase, alkaline phosphatase and gamma-glutamyltranspeptidase was significantly higher in both age groups of GF mice in comparison with CV ones; on the other hand, sucrase and glucoamylase activities were higher in CV mice. Monoassociation with B. bifidum accelerates biochemical maturation of enterocytes resulting in a shift of specific activities of brush-border enzymes between the values found for GF and CV mice. This effect of B. bifidum supplementation was less pronounced for alkaline phosphatase, sucrase, glucoamylase and dipeptidyl peptidase i.v. in immature gut of weaned mice than of 2-month-old ones.

Jejunal brush border microvillous alterations in Giardia muris-infected mice: role of T lymphocytes and interleukin-6.

Intestinal colonization with the protozoan Giardia causes diffuse brush border microvillous alterations and disaccharidase deficiencies, which in turn are responsible for intestinal malabsorption and maldigestion. The role of T cells and/or cytokines in the pathogenesis of Giardia-induced microvillous injury remains unclear. The aim of this study was to assess the role of T cells and interleukin-6 (IL-6) in the brush border pathophysiology of acute murine giardiasis in vivo. Athymic nude (nu(-)/nu(-)) CD-1 mice and isogenic immunocompetent (nu(+)/nu(+)) CD-1 mice (4 weeks old) received an axenic Giardia muris trophozoite inoculum or vehicle (control) via orogastric gavage. Weight gain and food intake were assessed daily. On day 6, segments of jejunum were assessed for parasite load, brush border ultrastructure, IL-6 content, maltase and sucrase activities, villus-crypt architecture, and intraepithelial lymphocyte (IEL) infiltration. Despite similar parasitic loads on day 6, infected immunocompetent animals, but not infected nude mice, showed a diffuse loss of brush border microvillous surface area, which was correlated with a significant reduction in maltase and sucrase activities and a decrease in jejunal IL-6 concentration. In both athymic control and infected mice, jejunal brush border surface area and disaccharidases were high, but levels of tissue IL-6 were low and comparable to the concentration measured in immunocompetent infected animals. In both immunocompetent and nude mice, infection caused a small but significant increase in the numbers of IELs. These findings suggest that the enterocyte brush border injury and malfunction seen in giardiasis is, at least in part, mediated by thymus-derived T lymphocytes and that suppressed jejunal IL-6 does not necessarily accompany microvillous shortening.

Modification of disaccharidase activity measurement in rat bowel.

This study describes a modification of the existing disaccharidase assay in rat small bowel in which whole bowel, rather than mucosa, is utilized. In addition, the use of total vs. specific activity as a more accurate unit of measurement of disaccharidase activity is discussed.

Evidence for an intracellular barrier to cadmium transport through Caco-2 cell monolayers.

109Cd transport was studied in the highly differentiated TC7 clone of the enterocytic-like Caco-2 cells grown on filters. Accumulation curves for 0.3 microM 109Cd over 12 h from the apical (AP) or the basal (BL) sides revealed a three-step mechanism involving: 1) a zero-time accumulation Ao; 2) a fast process Af(t1/2 < or = 10 min); and 3) a slow process of uptake As (5 h < or = t1/2 < or = 10 h) responsible for the major cellular levels of 109Cd. The relative contribution of adsorption to total accumulation is greater for short exposure times (< or = 35%), but is no longer significant after the exposure times needed to reach equilibrium. Transepithelial transport was less than 4% of the cellular level at 12 h. A negligible but specific binding onto the BL surface of the filters was characterized. Saturable systems of accumulation with comparable affinities (Km = 2.5+/-0.5 and 5.4+/-0.4 microM) but distinct capacities (Vmax = 8.9+/-1.2 and 312+/-22 pmol/min/mg protein) were identified at the AP and BL cell membranes, respectively. Efflux studies revealed that Cd accumulation is only partially reversible, with an exclusive metal release at the same side. A 2-h exposure on both sides simultaneously failed to demonstrate any competition for cellular accumulation: uptake was additive relative to AP and BL uptake values. These data suggest that Af leads to an accumulation of loosely bound Cd, whereas As represents irreversible intracellular binding processes. We conclude that Cd transport occurs exclusively by a transcellular route and that saturation of the intracellular high-capacity binding sites is the rate-limiting step in Cd absorption.