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A biophysical model for calculating the effective parameters of low-frequency magnetic fields was developed by Lednev based on summarized empirical data. According to this model, calcium ions as enzyme cofactors can be the primary target of low-frequency magnetic fields with different parameters tuned to calcium resonance. However, the effects of calcium-resonant combinations of static and alternating magnetic fields that correspond to Lednev’s model and differ by order in frequency and intensity were not studied. It does not allow for confidently discussing the primary targets of low-frequency magnetic fields in terms of the magnetic influence on ions-enzyme cofactors. To clarify this issue, we examined the response of freshwater crustaceans Daphnia magna to the impact of combinations of magnetic fields targeted to calcium ions in enzymes according to Lednev’s model that differ in order of magnitude. Life-history traits and biochemical parameters were evaluated. Exposure of daphnids to both combinations of magnetic fields led to a long-term delay of the first brood release, an increase in the brood size, a decrease in the number of broods, and the period between broods. The amylolytic activity, proteolytic activity, and sucrase activity significantly decreased in whole-body homogenates of crustaceans in response to both combinations of magnetic fields. The similarity in the sets of revealed effects assumes that different magnetic fields tuned to calcium ions in biomolecules can affect the same primary molecular target. The results suggest that the low-frequency magnetic fields with parameters corresponding to Lednev’s model of interaction between biological molecules and ions can remain effective with a significant decrease in the static magnetic background.

Porcine reproductive and respiratory syndrome (PRRSV) and porcine epidemic diarrhea (PEDV) viruses are two of the most economically significant diseases to affect the U.S. swine industry today. Yet, little is known about how they impact pig nutrient digestibility, intestinal function and feed efficiency. Therefore, the overall objective of this thesis was to determine the impact of PRRSV and PEDV viruses, alone or in combination, on grower pig performance, tissue accretion and on intestinal function and integrity. To accomplish these objectives, a series of experiments were conducted and are outlined in three research chapters (Chapter 2, 3 and 4). In Chapter 2, an experiment was conducted using growing pigs to assess the longitudinal impact of PRRSV on growth performance, feed efficiency, tissue accretion and apparent total tract digestibility (ATTD). In Chapter 3 pigs were infected with PRRSV, PEDV or a combination of both, to determine their impact on growth performance, feed efficiency, ATTD and apparent ileal digestibility (AID). The final research chapter (Chapter 4) assessed the effects of PRRS and PED viruses on intestinal integrity and function. The results from this research indicate that PRRSV significantly reduces overall growth performance and feed efficiency. It also reduces ATTD of nutrients and energy in an industry setting (Chapter 2), but did not reduce AID of nutrients (Chapter 3). Expectedly, PRRSV infection did not affect markers of intestinal health and integrity, but did improve active glucose and lysine transport in the jejunum (Chapter 4). Jejunum sucrase activity was also improved during the 21 day PRRSV infection. However, no differences in the gene abundance of nutrient transporters between PRRSV and healthy

Knowledge of factors related to caries and the possible consequences in controlling the disease may show the use of education as a relevant tool for achieving success in terms of dental health maintenance. Therefore, the aim of the present study was to investigate the relationship between acquired knowledge and salivary factors related to dental caries for freshmen students (n = 44) and trainees (n = 32) of the Piracicaba Dental School. Knowledge about dental caries was evaluated by a discursive questionnaire analyzed by the content analysis technique. Salivary flow and pH, buffer capacity, salivary sucrase activity, microbiological counts (total microorganisms, mutans, and lactobacilli) and inorganic concentration of calcium, phosphorus, and fluoride in saliva were evaluated and compared between groups using the Mann–Whitney test, with a significance of 5%. Trainees demonstrated knowledge of the disease, whereas freshmen showed unspecific and confusing concepts. Among the factors analyzed, statistically significant differences were observed for pH, buffer capacity, sucrase activity, total microorganisms, and calcium and fluoride concentrations in saliva. Knowledge about the disease increases and improves over time during the undergraduate program (highest among trainees); although the students from the final year of the program consume more sugar than those from the previous one, they try to balance this activity with greater exposure to fluorides.

The White-fronted Woodpecker (Melanerpes cactorum) drills wells in living branches and trunks of trees and shrubs to feed on sap flows, providing an energy-rich food resource for other bird species diverse in ecological attributes and taxonomic affinities. The aim of this study was to explore the avian assemblage that consumes sap from sap wells drilled by the White-fronted Woodpecker in 4 regions of Argentina distributed along an aridity gradient (precipitation and temperature), reaching from humid forest of the Chaco in the north to scrublands and open forest of the Monte in the south. We classified sap-feeding species according to the importance of nectar in their diet (specialist, facultative, or occasional nectarivores) and their efficiency in assimilation of sucrose (the main sugar in sap). We also compared the proportion of observed sap-feeding species with diversity of potential sap-feeding birds along the geographical aridity gradient. Forty-six bird species were recorded feeding at sap wells drilled by the White-fronted Woodpecker. Proportion of sap-feeding species was similar along the aridity gradient, and the type of diet and sucrase activity were not associated with the geographical aridity gradient. However, the proportion of occasional nectarivores with a low rate of sucrose assimilation was higher in Arid Monte (the most arid region) than in regions of lower aridity. Sap-feeding species could supplement their diets with sap, in varying degrees, during periods of scarcity of food resources, and White-fronted Woodpeckers through their sap wells could contribute to the persistence of this assemblage of sap-feeding bird species. Nevertheless, sap consumption by sapfeeding birds depends ultimately on the physiological and behavioral characteristics of each species. Fil: Nuñez Montellano, Maria Gabriela. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Blendinger, Pedro Gerardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Bodrati, Alejandro. Proyecto Selva de Pino Paraná; Argentina Fil: Salvador, Sergio A.. No especifíca

Study on the effect of different nitrogen treatment on cv.Huangguogan soil peroxidase, urease, phosphatase, sucrase activity. The amount of nitrogen was 3 treatments: conventional nitrogen application rate (N1), 125% conventional nitrogen application rate (N2) and 150% conventional nitrogen application rate (N3). The results showed that proper amount of nitrogen fertilizer was beneficial to improve soil enzyme activity, but the soil enzyme activity was decreased when the amount of nitrogen was increased or too much.

The goal of growth factor treatment in patients with short bowel syndrome (SBS) is to facilitate transition from parenteral to enteral feedings. Ideal use of growth factors would be acute treatment that produces sustained effects. We investigated the ability of acute insulin-like growth factor I (IGF-I) treatment to facilitate weaning from total parenteral nutrition (TPN) to enteral feeding in a rat model of SBS. After a 60% jejunoileal resection + cecectomy, rats treated with IGF-I or vehicle were maintained exclusively with TPN for 4 days and transitioned to oral feeding. TPN and IGF-I were stopped 7 days after resection, and rats were maintained with oral feeding for 10 more days. In IGF-I-treated rats, serum concentration of IGF-I and final body weight were significantly greater because of a proportionate increase in carcass lean body mass than in vehicle-treated rats. Acute IGF-I treatment induced sustained jejunal hyperplasia on the basis of significantly greater concentrations of jejunal mucosal protein and DNA without a change in histology or sucrase activity. These results demonstrate that acute IGF-I facilitates weaning from parenteral to enteral nutrition in association with maintenance of a greater body weight and serum IGF-I concentration in rats with SBS.

The total amylolitic activity and sucrase activity in the Amur sleeper intestine are similar to those in typical and facultative benthophages. The optimal temperature of starch hydrolysis is 50 °C. The sleeper’s carbohydrases are more tolerant to the increase in water temperature during winter than similar enzymes in cyprinids.

The purpose of this study was to determine if sacrosidase, a liquid produced from Saccharomyces cerevisiae containing 6000 IU of sucrase activity per mg protein, prevented symptoms of diarrhea, abdominal cramps, gas, and bloating in patients with congenital sucrase-isomaltase deficiency (CSID) consuming a normal sucrose and carbohydrate-containing diet.Twenty-eight children (aged 5 months to 11 years) underwent a randomized, double-blind trial consisting of two phases: 1) three sucrose breath H2 tests with three single-dose treatments (placebo, sacrosidase, and sacrosidase plus milk), and 2) a dose-response phase consisting of four multidose treatments, each for 10 days of full-strength sacrosidase, 1:10 dilution, 1:100 dilution, and 1:1000 dilution. Patients who weighed less than or equal to 15 kg received a dose of sacrosidase and those who weighed more than 15 kg received 2 ml. For the dose-response phase each patient consumed a normal diet. The number of stools and severity of symptoms were recorded daily for each concentration of sacrosidase administered and compared to a baseline period during which the patient took no sacrosidase and consumed a sucrose/starch-free diet. Data were analyzed using an ANOVA model and the nonparameter Wilcoxon signed-rank test.Breath H2 excretion decreased significantly when patients received sacrosidase or sacrosidase plus milk compared to placebo during sucrose breath tests. During the dose-response phase significant treatment differences were observed between the two higher concentrations and the two lower concentrations of sacrosidase for both total stools (p0.001) and total symptom score (p = 0.003). Higher concentrations of sacrosidase were associated with fewer stools and a greater number of formed or hard stools compared to lower concentrations and compared to the baseline period. Higher concentrations were also associated with fewer symptoms of gas, abdominal cramps, or bloating, but no differences in vomiting. The only significant adverse event was wheezing in one child with a history of asthma.Sacrosidase is a safe, effective, well-accepted treatment to prevent gastrointestinal symptoms in patients with CSID consuming a normal diet.

The development of biological soil crusts (BSCs) is widely recognized as beneficial to soil fertility due to their contribution to the stabilization of soils and to the increase in their carbon and moisture content. An important role in these processes is played by the extracellular polysaccharidic (EPS) matrix embedding microbial cells and soil particles in BSCs. The present study was aimed at investigating the molecular and chemical features of the EPSs and the degradation processes of the polysaccharidic matrix (i.e. dehy-drogenase and sucrase activities) in induced biological soil crusts (IBSCs) of different ages displayed within an investigation area in Hobq Desert (Dalatequi County, Inner Mongolia, China). Two operationally defined EPS fractions, the colloidal (C-EPS) and the EDTA extractable (tightly bound, TB-EPS) fractions, were analyzed. In BSCs, C-EPSs are loosely bound to cells and sediments while TB-EPSsare tightly bound to the crustal biotic and abiotic constituents of the crusts. In this study, the C-EPSand TB-EPS fractions extracted from the IBSCs of different age (4-, 6- and 8-years old IBSCs) were foundpresent in comparable amounts but showed marked differences in terms of their molecular size distribution and monosaccharidic composition. C-EPS showed to be mostly constituted by sugar fractions with molecular weight (MW) distributed in the range 2000 e 76 kDa and in the range 64 E 0.34 kDa. Conversely, the TB-EPSs showed to be prominently constituted by one fraction having a MW in the range 2000 e 76 kDa. While the chemical and macromolecular characteristics of TB-EPSs did not show significant changes with the age of the crusts, the older IBSCs showed a lower content of low MW C-EPSs, as well a higher number of different types of monosaccharides constituting the C-EPS. Moving from these results, it can be hypothesized that C-EPSs, which are dispersed in the soil and thus more accessible, have been rather easily degraded by the heterotrophic microorganisms dwelling in mature IBSCs and reduced to low MW carbohydrates that are easily metabolized by chemoheterotrophs. This hypothesis is supported by the higher activity observed in older IBSCs of the two enzymes associated with sugar degradation in the soil, dehydrogenases and sucrases, that is consistent with an increased release of low MW carbohydrates in the crusts. The results obtained suggest that the colloidal fraction of the EPSs, which is more dispersed in the soil, is more easily degradable by the microflora, while the EPS fraction tightly bound to the soil particles, which is characterized by a high MW, plays a key role in giving a structural stability to the crusts and in affecting the hydrological behavior of the soil covered by IBSCs.

An in vitro influence of temperature and season on some carbohydrase activity and kinetic characteristics of intestinal mucosa enzymes in six species of freshwater teleosts were investigated. Significant correlation between the level of total amylolytic and sucrase activity of the intestinal mucosa and the carbohydrate content in fish food as well as intensity of fish feeding were demonstrated. Values of kinetic characteristics increased (the enzyme-substrate affinity decreased) with temperature. The lipid matrix of the enterocyte membranes influenced the values of these parameters.

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.

Codeine is a common drug widely used in some countries as a pain reliever. The effect of codeine on yeast sucrase activity was studied in this report. Non-competitive inhibition was observed using double reciprocal plot. The Km of enzyme did not change in the presence of different concentrations of codeine (0.5- 1.5 mM) and was determined about 11.5 mM. The Vmax of enzyme was determined about 8.8 mM/min, and the Vmax decreased in the presence of codeine. The Ki of codeine was measured by using the reaction rate and the initial concentration of the inhibitor according to the Dixon plot. The Ki was found to be 0.42 mM and the IC50 of codeine was determined about 0.875 mM.

In this study we introduce the use of tunable diode laser absorption spectroscopy (TDLAS) as a technique for making measurements of the delta13C of animal 'breath' in near real time. The carbon isotope ratios (delta13C) of breath CO2 trace the carbon source of the materials being metabolized, which can provide insight into the use of specific food resources, e.g. those derived from plants using C3 versus C4 or CAM photosynthetic pathways. For physiological studies, labeled substrates and breath analyses provide direct evidence of specific physiological (e.g. fermentative digestion) or enzymatic (e.g. sucrase activity) processes. Although potentially very informative, this approach has rarely been taken in animal physiological or ecological research. In this study we quantify the utilization of different plant resources (photosynthetic types--C3 or C4) in arthropod herbivores by measuring the delta13C of their 'breath' and comparing it with bulk tissue values. We show that breath delta13C values are highly correlated with bulk tissues and for insect herbivores reflect their dietary guild, in our case C3-specialists, C4-specialists, or generalists. TDLAS has a number of advantages that will make it an important tool for physiologists, ecologists and behaviorists: it is non-invasive, fast, very sensitive, accurate, works on animals of a wide range of body sizes, per-sample costs are small, and it is potentially field-deployable.

Mucopolysaccharidosis type IIIA (MPS IIIA) is a lysosomal storage disorder caused by a deficiency in sulphamidase (NS), a lysosomal enzyme required for the degradation of heparan sulphate glycosaminoglycans (gags). The MPS IIIA mouse is a naturally occurring model that accurately reflects the human pathology and disease course. It displays primarily central nervous system pathology accompanied by widespread accumulation of gag in somatic tissues. MPS IIIA mice exhibit greater bodyweight gain than normal littermates and attain a higher mature bodyweight. In this study, gastrointestinal morphology and function was characterised in the IIIA mouse. Stomach and duodenum weight increased in MPS IIIA mice and duodenum length also increased. An increased submucosal thickness was observed in MPS IIIA intestine compared to normal mice and lysosomal storage of gag was observed in this region. Storage was also observed in the lamina propria of the villus tip. All other morphometric measurements including villus height and crypt depth fell within the normal range. The gastric emptying half-life of solid and liquid meals decreased with age in normal mice whereas the T½ of solid meals did not alter with age in MPS IIA mice such that they were elevated above normal by 38 weeks of age. Sucrase activity was higher than normal in MPS IIIA at all ages tested. These abnormalities in GI structure and function observed in MPS IIIA may contribute to weight gain in this disorder. Refereed/Peer-reviewed

The sucrase and levansucrase activities of Zymomonas mobilis cells were characterized. The kinetics of production of sucrase activity was growth associated and the activity was constitutively expressed in cells grown on sucrose, glucose, or fructose media. Most of the sucrase activity (about 80%) was soluble and extracellular, while the cellular activity (about 20%) was demonstrated to be mostly membrane bound. The occurrence of sucrase activity in culture medium seemed to result from a secretory mechanism rather than from cell lysis. Like sucrase activity, levansucrase activity was mainly extracellular and was present in fermentations run with the above three carbon sources. These results demonstrated that both sucrase and levansucrase activities were present in cellular and extracellular extracts of cells grown on different sugars. Key words: Zymomonas mobilis, levansucrase, sucrase, localization.

Samples of stimulated whole saliva were collected from 176 dental students, and their teeth were examined both clinically and radiographically. Salivary flow; buffering capacity; numbers of lactobacilli, yeasts, and Streptococcus mutans; and DMFS and DS values were correlated to sucrase activity. The high flow-rate group had a lower (p = 0.0201*) sucrase activity than the low flow-rate group. The proportion of high (greater than or equal to 10 mumol/min x mg x 10(-3] sucrase activities among the highest density category of lactobacilli was 67%, whereas the corresponding proportion in the whole material was only 28%. Men had significantly (p = 0.0169*) higher sucrase activities than women. The other variables measured did not seem to have any significant effect on the sucrase activity values. In addition to sucrose consumption, other factors like the rate of salivary flow and the density of lactobacilli seem to influence the level of salivary sucrase activity.

It has been hypothesized that species belonging to the Sturnidae-Muscicapidae lineage, despite having generalist diets comprising fruits with sugars of diverse kinds, do not express intestinal sucrase. In order to increase the taxonomical range of species for which sucrase intestinal activity has been investigated, we analyzed the relationship between enzymatic activity (sugar digestion) and feeding preference for native fruits containing sucrose, in two South American members of the superfamily Muscicapoidea, the Austral thrush (Turdus falcklandii) and the Chilean mockingbird (Mimus thenca). We hypothesized that these birds would lack intestinal sucrase activity and that in preference tests they would reject sucrose solutions. Both thrushes and mockingbirds lacked significant intestinal sucrase activity. Considering the phylogenetic constraint hypothesis for sucrose digestion in the Muscicapoidea superfamily, our results support the notion that lack of sucrase activity is a shared derived-character only for the Cinclidae-Sturnidae-Turdinae lineage, and suggests that the selective pressure that these birds can exert on the plants whose seeds they disperse and whose flowers they visit are consistent across world hemispheres. Food preference by thrushes was significantly biased toward glucose and fructose, showing scant to nil consumption of sucrose, thus corroborating a positive relationship between digestion capabilities and food preference for different sugar types Se ha planteado que el linaje Sturnidae-Muscicapidae no expresa sacarasa intestinal. Con el fin de aumentar el rango taxonómico para el cual se ha investigado la actividad de sacarasa intestinal, analizamos la relación entre la actividad enzimática (digestión de azúcar) y preferencias dietarias por itemes que contienen sacarosa, en dos miembros Sudamericanos de la superfamilia Muscicapoidea, el zorzal (Turdus falcklandii) y la tenca (Mimus thenca). Hipotetizamos que estas aves no debieran presentar sacarasa intestinal y que debieran rechazar soluciones de sacarosa en pruebas de preferencia. Ninguna de las especies presentó una actividad significativa de sacarasa intestinal. A la luz de los nuevos antecedentes de la relación filogenética del grupo Muscicapoidea, nuestros resultados apoyan la hipótesis respecto que la pérdida de la sacarasa intestinal es un carácter derivado y compartido sólo por el linaje Cinclidae-Sturnidae-Turdinae y sugiere que las presiones selectivas que esas aves ejercen sobre las plantas cuyas semillas dispersan y cuyas flores visitan, son consistentes entre ambos hemisferios. La preferencia de alimentación de zorzales fue significativamente sesgada hacia el consumo de glucosa y fructosa, mostrando un escaso a nulo consumo de sacarosa, corroborando así, una relación positiva entre la capacidad de digestión y preferencias de alimentación por diferentes tipos de azúcares

Quantitation of salivary sucrase activity has been proposed as a method for the estimation of the level of sucrose consumption. The purpose of the present study was to investigate the physiologic variability of the sucrase activity and microbial counts in paraffin-wax-stimulated saliva of subjects with sound sucrose consumption habits. Variation was analyzed by repeated sampling studies. Intraday variability was investigated by serial analyses of 16 individuals who gave eight samples at 2-h intervals on a single day. Interday variation was studied by analyzing the morning value of 24 individuals on three consecutive days. Interday variability of salivary mutans streptococci, lactobacilli, and yeasts was tested using semiquantitative commercial test kits. The diurnal variation of sucrase activity revealed that the activity in the morning was significantly higher than at noon or at later sampling times of the day. Interday variation was considerable in subjects with high sucrase values. The day-to-day variability of the salivary microbes was considerable for lactobacilli and relatively small for yeasts. A weak positive correlation ranging from 0.732 to 0.741 was found between high sucrase activity values and salivary lactobacilli. Salivary samples should be collected in the morning to differentiate between subjects with high and low sucrase activities.

1. The effects of EGF administered subcutaneously on the intestinal cessation of macromolecular transmission and sucrase development were investigated in suckling rats and compared with those on hydrocortisone-treated pups. 2. In the EGF-treated pups, intestinal absorptive response of IgG was suppressed 50% whereas, the sucrase activity was not affected. In the hydrocortisone-treated pups, the absorptive response was inhibited completely, while sucrase activity was induced precociously. 3. The characteristics of intestinal cessation was morphologically observed at the jejunal epithelial cells in EGF and hydrocortisone-treated pups. 4. These results suggest that EGF affects the maturation of gastrointestinal function in a manner different from that of glucocorticoid hormones.

Summary: This study was designed to determine the critical difference between rat milk and rat chow with respect to their effects on jejunal sucrase activity during the fourth postnatal wk. Rats were weaned onto special diets on postnatal day 17, and jejunal sucrase was assayed on day 28. A pelleted diet containing lactose as sole carbohydrate did not cause depression of sucrase activity. Sucrase values (μmoles/hr/mg protein) were 10.49 ± 0.81 (n = 15) for the lactose chow and 6.65 ± 0.29 (n = 16) for the sucrose chow. This indicates that the nature of the dietary carbohydrate does not account for the sucrase differences of weaned and nonweaned animals. Likewise, the physical consistency of the diet is unimportant because sucrase values were just as high on a liquid diet (10.91 ± 0.77 μmoles/hr/mg protein; n = 8) as on the solid diets. However, when the relative proportions of carbohydrate and fat in the diet were varied, there were significant effects on sucrase activity; values on a low carbohydrate diet (4.30 ± 0.33 μmoles/hr/mg protein; n = 8) being less than one-half those on a high carbohydrate diet (10.91 ± 0.77 μmoles/hr/mg protein; n = 8). Speculation: The terminal maturation of jejunal sucrase is dependent on the normal process of weaning. The critical feature of the weanling diet is that it is a high-carbohydrate, low-fat diet. In the absence of this dietary transition, intestinal development remains incomplete.

ラット小腸で, in vivoでのsucrase活性とin vivoでのショ糖の減少速度との対応関係を, 離乳前後および昼夜で検討し, 以下の結果を得た。1. 授乳期から離乳期にかけて, sucrase活性は10数倍に増加し, それに比例的に対応して, in vivoでのショ糖の減少速度も増加した。2. 成熟ラットにおいて, sucrase活性は著明な日周期変動を示し, 夜高く, 昼低い値となるが, in vivoでのショ糖の減少速度も, それにご対応した変動が認められた。3. 幅広い生理的条件下において測定されたin vivoでのsucrase活性と, in vivoでのショ糖の減少速度との間に比例関係が認められ, さらにショ糖由来のブドウ糖の吸収速度との間にも比例関係が見られた。ここで, ブドウ糖の吸収量は, ショ糖減少量の約80%であった。以上の結果から, ショ糖の分解・吸収はsucraseによって規定されており, in vivoでのsucrase活性を測定することにより, 生理的条件下でのショ糖の分解のみならず, 吸収をも予測しうることが明らかとなった。

Daily administration of L-thyroxine (20 micrograms or 200 micrograms/100 g body weight) to adult male rats decreased jejunal lactase activity by 35% after 2-, 3-, 4- and 10 days. Four days of injections of D-thyroxine (200 micrograms/100 g body weight/day) produced a similar decrease of lactase activity. Sucrase activity was uninfluenced except for a 30% increase after daily injections of L-thyroxine (200 micrograms/100 g body weight) for 10 days. Acid beta-galactosidase activity was unaffected by either D- or L-thyroxine.

Sucrose consumption data of the sucrose group (n = 33) of a 2-yr longitudinal study was plotted against salivary sucrase activity values obtained during this 2-yr period. The correlation coefficients varied between 0.194 and 0.551. The subjects were divided into high (greater than or equal to 10 mumol x min-1 x (10(-3)) and low (less than 10) sucrase activity subgroups. There were significant differences in the sucrose consumption and in intake frequency between these two subgroups. These findings give further support for the possibility of using sucrase activity for the estimation of the level of individual sugar consumption.

sucrase活性におよぼす高果糖食の影響をしらべるために, 白ネズミを高果糖食群, 高ブドウ糖食群, 高澱粉食群および飢餓群に分け, いずれも1日3時間のmeal-feedingで4日間または2週間飼育した。1) 高果糖食群のみが, とくに4日間のmeal-feedingにおいて, 小腸粘膜が著しく増加していた。2) Brush borderの重量も, 4日間のmeal-feedingで高果糖食群のみが飢餓群にくらべて有意な増加を示した。3) 小腸粘膜の増加傾向に対応してsucrase活性は上昇していた。高果糖食群のsucrase活性は小腸粘膜の重量あたりでもたん白質あたりでも他の群よりも大きかった。4) brush borderのsucrase比活性は各群の間に差がみられなかった。すなわち, 食餌中糖質源のちがいによる差は認められなかった。

Three groups of rats were fed, respectively, a chemically defined diet intragastrically (IG), an equivalent diet intravenously (IV) and solid food orally (CH) for 8 days, and their small intestines and colons compared. All received equal calories. The small intestine was divided into equal proximal (A), middle (B), and distal (C) segments for measurements. Mucosal weight per cm in segments A and B of IG were, respectively, 65 and 38% higher than in IV (P less than 0.01), but 27 and 33% lower than in CH (P less than 0.01). However, in the distal segment, C, mucosal weight in IG was similar to IV and CH was 79% higher (P less than 0.01). DNA and protein followed the same pattern. Segment A sucrase activities were similar in CH and IG and were much higher than in IV (P less than 0.01). Sucrase in IG dropped very rapidly distally so that it became much lower than in CH (P less than 0.05) and similar to IV. Mucosal weight, DNA, and protein in the colon were not significantly different in IG and IV, which were both significantly lower than in CH (P less than 0.01). The results indicate that a chemically defined diet maintains intestinal mass well in the proximal small intestine, but the effect diminishes rapidly in a distal direction so that distal small intestine and colon become atrophied and similar to those in intravenous feeding.

To clarify the physiological significance of circadian rhythmic changes in the activity of intestinal sucrase, the activity of digestion and absorption of sucrose in vivo were assessed during the daytime and the nighttime in rats fed ad libitum. When the jejunum was perfused at night with a solution containing sucrose in situ, the disappearance rate of sucrose from the lumen was higher than when perfused during the daytime, in parallel with the day/night difference in sucrase activity. The early response of plasma glucose to oral sucrose load in unanesthetized free-moving rats was also greater during the nighttime than the daytime. It was concluded that the digestion and absorption rate of sucrose shows circadian fluctuations under normal physiological conditions.

The sites of stimulation of dietary sucrose-mediated changes in jejunal sucrase activity was investigated in rats refed on 5 g of a high sucrose diet following a 2-day fast. Actinomycin D was injected into rats 7.5 hr prior to, just before or 15 hr after the beginning of refeeding. Regardless of actinomycin D injection and respective periods, jejunal sucrase specific activity (sucrase activity per mg of mucosa protein) of rats 24 hr after the beginning of refeeding was significantly increased, but the significant increase in the segmental sucrase activity, sucrase activity per 15 cm segment, was remarkably inhibited by actinomycin D injection 7.5 hr prior to and just before refeeding. There was no difference in time-course changes in the sucrase specific activity after the beginning of refeeding between rats receiving actinomycin D injection 7.5 hr prior to refeeding and treated with saline injection in the same period. However, the significant rise of the segmental sucrase activity between 15 and 24 hr after the beginning of refeeding was remarkably inhibited by the actinomycin D injection. Hydroxyurea (a karyorrhexis agent) injection just before the beginning of refeeding affected neither the increase in jejunal sucrase specific activity nor that in the segmental sucrase activity, but the hydroxyurea injection 3 hr prior to refeeding caused a significant reduction of increases in the sucrase specific activity and the segmental sucrase activity. The significant increase in segmental sucrase activity 24 hr after the beginning of refeeding was not affected by a massive addition of surface-active agents into the refed diet and drinking water during the initial period of refeeding. These experimental results lent strong support to the idea that the stimulation of the response of jejunal sucrase activity to dietary sucrose in rats was produced in the crypt cell during the initial period of refeeding.

Intestinal sucrase activity of the rat varies with the age, but not the sex, of the animal. Sucrase activity of rats 23 days of age was approximately two-thirds that of adults.Sucrase activity of adult rats was significantly decreased by several days of fasting. The decrease was rapid during the first 2 to 4 days of the fast, but became negligible thereafter.Diets containing large (70%) amounts of sucrose, galactose, melizitose, or α-methyl-D-glucoside produced highly significant increases in intestinal sucrase levels (compared with a carbohydrate-free, high-casein control diet) when fed ad libitum for 24 hours to adult male rats previously fasted for 3 days. Similar diets containing fructose, fructose plus glucose in equimolar amounts, or maltose significantly increased sucrase activity, but diets containing glucose, mannose, xylose, or lactose were not stimulatory. A 70% raffinose diet significantly decreased sucrase activity. Normal male rats which were fed the 70% sucrose diet for 4 weeks had sucrase activities similar to those of controls fed Purina fox checkers, but animals fed the carbohydrate-free, high-casein diet for 1 day or longer had sucrase activities significantly lower than those of controls. The significance of these observations in regard to enzyme "adaptation" is discussed.

Guinea pigs subjected to fasting for 2 days were compared with controls subjected to fasting for 1 day and fed for 1 day. Weight, protein content and sucrase activity of intestinal mucosa were found l