Non-specific carboxylic esterase activity in the digestive tract of the perch, Perca fluviatilis L.

The distribution of non-specific carboxylic esterases (Ec 3.1.1) in the digestive tract of perch, Perca fluviatilis L., was investigated histochemically using 1-naphthyl acetate as the substrate. Strong enzymatic activity was present in the gastric glands and surface cells of the stomach, intestinal mucosa of the pyloric caeca, upper and middle intestine, pancreas (exocrine cells) and liver. The enzymatic activity in the lower intestine and rectum was weak. The activity was not demonstrated in the oesophagus or pyloric sphincter. In the intestine, the activity was localized in the columnar cells especially in the supranuclear cytoplasm. The enzymatic activity demonstrated in the digestive tract of perch using 1 -naphthyl acetate represents combined esterolytic and lipoproteolytic activity.     

Temperature dependent characteristics of intestinal glycyl-L-leucine dipeptidase in boreal zone fish

Three kinds of boreal zone fish were investigated for gastrointestinal glycyl-L-leucine (GL) dipeptide cleaving activity as a function of feeding stage and seasonal changes. The enzyme activity tested in the perch (Perca fluviatilis L.) intestine increased steadily during digestion and rapidly disappeared after completion. The temperature characteristics and the seasonal changes in dipeptide cleaving activity in pike perch (Stizostedion lucioperca L.) and bream (Abramis brama L.) were studied. In summer, the maximal activities in the pike perch and the bream were found at temperatures of 40 and 30 degrees C, respectively. In winter, the temperature of maximal activity in pike perch fell to only 30 degrees C, whereas no changes were observed in bream. The activation energies in bream and pike perch were several times lower in winter than in summer. Seasonal changes in the dipeptide cleaving activity at low temperature relative to that at the temperature of maximal activity were found. At high temperatures, the stability of the enzyme decreases in winter and increases in summer, but in the presence of a substrate the thermal stability of the enzyme increases both in winter and in summer. In our experiments, we found that in these fish, GL dipeptidase was unstable at 0 and -10 degrees C.     

Influence of diurnal rhythms of feeding during intestine total amylolytic activity and activity of alkaline phosphatase in juvenile fish

The total amylolytic activity and activity of alkaline phosphatase in the intestine mucosa of larvae and fries of roach, blue bream, and perch change both during the process of individual development and during the day. Maximal intensities of juvenile feeding was observed primarily in the morning and evening hours. The pattern of diurnal alkaline phosphatase activity correlates to a greater extent to intensity of juvenile feeding, in comparison to the pattern of total amylolytic activity. In planktivorous blue bream, such regularity is more pronounced than in benthivorous roach. The total amylolytic activity in fries of roach, blue bream and perch correlates to fish type of feeding.     

Seasonal variations of the localization of the Bunodera luciopercae marites (Trematoda: Bunoderidae) in three species of perch fishes

Distribution of Bunodera luciopercae marites in the intestine of the fuff, sande and perch were studied in the Rybinsk Reservoir. For the fuff and perch fry, except three summer months, the more proportion of helminths was observed in the posterior region of the intestine. Because of a continuous passage of B. luciopercae in predatory fishes (sanders and adult perches), more proportion of trematodes was always observed in anterior region of the intestine. In all groups of hosts, 20-30% of total parasite number was registered in the middle intestine.     

禁食与胰岛素处理对鳜血糖和leptin-A基因表达的影响

为研究硬骨鱼类leptin基因表达与血糖之间的关系, 研究在禁食与胰岛素处理后, 检测鳜血糖和肝脏、肠道和脂肪组织leptin-A基因表达水平。在禁食实验中, 鳜被禁食10d, 并分别于禁食后0、4h、2d、6d和10d取样。禁食后6d鳜血糖开始降低, 禁食后10d鳜血糖显著降低。同时, 禁食后6d鳜肝脏leptin-A基因mRNA表达水平显著升高, 禁食后4h鳜肠道和脂肪组织leptin-A基因mRNA表达水平均显著升高。在胰岛素处理实验中, 分别于注射后12h和36h取样。腹腔注射胰岛素后12h, 鳜血糖显著降低, 而鳜肝脏、肠道和脂肪组织leptin-A基因mRNA表达水平无明显变化。腹腔注射insulin后36h, 鳜肠道leptin-A基因mRNA表达水平显著升高。研究结果表明, 长期禁食或胰岛素处理均能够降低鳜血糖水平, 且影响消化器官和脂肪储存器官leptin-A基因表达。     

Metallo-protease activity increases prior to ovulation in brook trout (Salvelinus fontinalis) and yellow perch (Perca flavescens) follicle walls

Proteolytic activity was measured in the follicle wall surrounding oocytes from brook trout (Salvelinus fontinalis) and yellow perch (Perca flavescens) by use of two different protease assays: sodium dodecyl sulfate-polyacrylamide gel electrophoresis (substrate-SDS-PAGE) and a chromogenic synthetic peptide for type I collagen. In brook trout follicle walls, substrate-SDS-PAGE studies demonstrated that the activity of two proteolytic enzymes (80 kDa and 66 kDa) increased significantly before ovulation. The 80 kDa enzyme decreased significantly after ovulation whereas the 66 kDa enzyme remained elevated following ovulation. In yellow perch follicle walls, substrate-SDS-PAGE studies demonstrated that the activity of the major protease (66 kDa) increased before ovulation and remained elevated after ovulation. A chromogenic synthetic peptide was used to assay collagenolytic activity in follicle walls of brook trout and yellow perch. This assay revealed that collagenolytic activity increased significantly in both species before ovulation and remained elevated after ovulation. These findings suggest that metallo-proteases are involved in digesting the follicle wall in teleosts before and after ovulation.     

小鼠小肠四种消化酶活力的胎后发育模式

为明确晚成型小鼠胎后发育肠道消化酶活力的建立过程和发育模式,探讨其与适应性调节假说的关系,测定了从出生后至27日龄小鼠小肠前、中、后段的乳糖酶、蔗糖酶、麦芽糖酶和氨基肽酶的酶活力。结果发现单位组织酶活力方面,乳糖酶活力先增后降,小肠前段在9日龄而中后段在12日龄达到最高,至27日龄时仅中段有微弱的酶活力;蔗糖酶活力12日龄始出现,前段和后段自15日龄迅速升高,至18日龄达最高,但随后显著降低,而中段在15日龄后持续升高至21日龄达到最高,此后维持在较高水平;麦芽糖酶出生时已具有活力,但在15日龄前维持较低水平,此后迅速升高,前后段在18日龄,中段在21日龄达到峰值,此后下降;小肠前段的氨基肽酶活力出生后至27日龄持续下降,而后段和中段从出生到断乳前则持续升高,断乳后略有下降。除乳糖酶总酶活力先增后降,在15日龄达峰值外,其余3种酶的总酶活力均持续增加。在小肠不同位置4种酶活力的分布具有显著差异,且日龄对不同位置酶活力的影响趋势不同。总之,小鼠小肠4种消化酶的酶活力随时间的变化能够与其食物转变的消化需求相匹配,部分地支持适应性调节假说。     

Synthesis of phosphatidylcholine by two distinct methyltransferases in rat colonic brush-border membranes: evidence for extrinsic and intrinsic membrane activities

The enzymatic synthesis of phosphatidylcholine from phosphatidylethanolamine via a transmethylation pathway has not been shown to occur in the small intestine and has been assumed to be absent from the entire gut. The existence of this pathway, however, has not been investigated in the large intestine. Utilizing a recently developed method for the isolation of brush-border membranes from rat colonocytes, the present studies were designed to determine whether phospholipid methylation activity was present in the large intestine. The results demonstrate that this pathway for synthesis of phosphatidylcholine exists in rat colonic plasma membranes and involves at least two distinct methyltransferases. The predominant product of the first enzyme (methyltransferase I) is phosphatidyl-N-monomethylethanolamine; phosphatidylcholine and phosphatidyl-N-monomethylethanolamine are the principal products of the second enzyme (methyltransferase II). Methyltransferase I has an apparent Km for S-adenosyl-L-methionine of 100.0 microM and a pH optimum of 8.0, while methyltransferase II has an apparent Km of 0.3 microM and a pH optimum of 6.0. Additional evidence to support the presence of two distinct enzymes includes the differential effects of ATP, Triton X-100, trypsin treatment, and temperature on their activities.     

Regional variability in circadian rhythmicity of intestinal digestive-absorptive functions.

The circadian rhythms of sucrase, maltase, isomaltase, trehalase, lactase, gamma-glutamyltransferase, leucylnaphthylamide hydrolyzing activity, alkaline phosphatase and monosaccharide transport were assessed in each fifth of the small intestine of the rat in order to determine if an entire enzyme or transport system population responded in a similar manner or if there were regional differences. Animals were maintained under a light-dark cycle and fed from 1400-1800, EST for 7 days. Functional activities were assessed every 4 h for 24 h, inclusively. Quantitative, and in a few instances, qualitative differences in different areas of the intestine were found for all functions. There were portions of the lactase and alkaline phosphatase populations which displayed no rhythmicity in activity. When rhythmicity was observed there were differences in the activity patterns along the intestine for all functions. Thus, the rhythm patterns obtained from homogenates of the entire small intestine are a composite of the patterns in regions of high average activity. Also, there appears to be a reasonable amount of local control of the various functions.     

The dynamics of proteinases activity in fish chyme and intestine mucosa upon exposure to fresh and brackish water in vitro

The dynamics of activities of proteinases in roach and perch chyme and in bream intestine mucosa upon exposure to water with various salinities for 96-216 h were studied. Irrespective of the water salinity and source of the enzymes, the proteolytic activities in chyme and intestine mucosa may rise considerably during exposure. This rise is presumably provided by the intestine microflora. This noted phenomenon is least typical for the ichthyophage-facultative benthophage perch when compared to typical benthophages. This is most likely determined by the lower species diversity of the enteral microbiota in perch.     

Intestinal arginase in vertebrates and invertebrates.

1. Arginase was found to be present in the intestine in all species of Annelida, Arthropoda and Chordata studied. 2. The activity of intestinal arginase differs from species to species, the differences reaching two orders of magnitude (100 x). 3. The highest activity of intestinal arginase was observed in the rodents (mouse, rat, hamster). 4. In animals in which the enzyme activity was high or moderately high, arginase activity showed topographical differentiation along the long axis of the intestine.     

The effect of seasonal changes on the activity of intestinal alkaline phosphatase of pike perch, Lucioperka lucioperka and of bream, Abramis brama

The effect of seasonal changes on the activity of intestinal alkaline phosphatase was evaluated in two types of fish grown in the Kurshskii bay of the Baltic sea. With the pike perch, Lucioperka lucioperka , higher enzyme activity and optimal temperature of activity were observed in the summer compared to winter, whereas with the bream, Abramis brama , essentially no difference in enzyme activity and in optimal temperature of activity was found between the two seasons. In both fish, the thermal stability of the enzyme and the activation energy of enzyme activity decreased in winter. The different biological nature of the two fish appears to be reflected in the response of the intestinal alkaline phosphatase to seasonal changes.     

Indirect effects of metal contamination on energetics of yellow perch (Perca flavescens) resulting from food web simplification

1. Benthic invertebrate community composition and yellow perch (Perca flavescens) diet, growth and activity levels from lakes along a metal‐contamination gradient were used to assess the importance of a naturally diverse prey base for maintaining energy transfer to growing fish, and how this transfer is disrupted by metal contamination. 2. Zoobenthic communities had lower diversity in metal‐contaminated lakes, with a notable absence of large bodied invertebrate taxa. 3. The average mass of non‐zooplankton prey items was significantly greater for 2+ and 3+ perch from the reference lake, and increased significantly with age in all except the most contaminated lakes where prey choice was limited. 4. Benthivorous perch from all contaminated lakes exhibited slowed growth. Perch from one of the contaminated lakes exhibited faster growth during piscivory, indicating slowed growth only while benthivorous. 5. Estimates of fish activity, using the activity of the glycolytic enzyme Lactate dehydrogenase in perch white muscle tissue as a proxy, suggested that shifts in diet to larger prey (in reference and intermediately contaminated lakes) lowered activity costs, which may explain how diet shifts maintain growth efficiency as perch grow larger.     

Variations in enzyme activity in stomach and pancreatic tissue and digesta in piglets around weaning

A study was performed to investigate the effect of weaning at 4 weeks of age on the activity of digestive enzymes in the stomach and pancreatic tissue and in digesta from 3 days prior to weaning to 9 days postweaning in 64 piglets. In stomach tissue the activity of pepsin and gastric lipase was determined. Pepsin activity declined abruptly after weaning but 5 days postweaning the weaning level was regained and in the gastric contents no change in pepsin activity was observed. Weaning did not influence the activity of gastric lipase. The activity of eight enzymes and a cofactor was measured in pancreatic tissue. The effect of weaning on the enzyme activity was highly significant for all enzymes except elastase. The activity of all enzymes remained at the weaning level during day 1-2 postweaning followed by a reduction of the activity. The activity of trypsin, carboxypeptidase A, amylase and lipase exhibited minimum activity 5 days postweaning. Trypsin activity increased to the preweaning level on day 7-9 whereas the activity of the others increased but did not reach the preweaning level. The activity of chymotrypsin, carboxypeptidase B and carboxyl ester hydrolase decreased during the entire experimental period. In digesta no effect of weaning was observed on the activity of amylase and trypsin. The activity of chymotrypsin was reduced after weaning in the proximal third of the small intestine and lipase and carboxyl ester hydrolase activity was reduced in the middle and distal parts of the small intestine after weaning. The present study shows that the activities of the digestive enzymes in the pancreatic tissue are affected by weaning. Even though the pancreatic secretion cannot be judged from these results they show that the enzymes respond differently to weaning. In general the activity of the digestive enzymes in pancreatic tissue is low on day 5 postweaning which in interaction with other factors may increase the risk of developing postweaning diarrhoea.     

Variations in enzyme activity in stomach and pancreatic tissue and digesta in piglets around weaning

A study was performed to investigate the effect of weaning at 4 weeks of age on the activity of digestive enzymes in the stomach and pancreatic tissue and in digesta from 3 days prior to weaning to 9 days postweaning in 64 piglets. In stomach tissue the activity of pepsin and gastric lipase was determined. Pepsin activity declined abruptly after weaning but 5 days postweaning the weaning level was regained and in the gastric contents no change in pepsin activity was observed. Weaning did not influence the activity of gastric lipase. The activity of eight enzymes and a cofactor was measured in pancreatic tissue. The effect of weaning on the enzyme activity was highly significant for all enzymes except elastase. The activity of all enzymes remained at the weaning level during day 1–2 postweaning followed by a reduction of the activity. The activity of trypsin, carboxypeptidase A, amylase and lipase exhibited minimum activity 5 days postweaning. Trypsin activity increased to the preweaning level on day 7–9 whereas the activity of the others increased but did not reach the preweaning level. The activity of chymotrypsin, carboxypeptidase B and carboxyl ester hydrolase decreased during the entire experimental period. In digesta no effect of weaning was observed on the activity of amylase and trypsin. The activity of chymotrypsin was reduced after weaning in the proximal third of the small intestine and lipase and carboxyl ester hydrolase activity was reduced in the middle and distal parts of the small intestine after weaning. The present study shows that the activities of the digestive enzymes in the pancreatic tissue are affected by weaning. Even though the pancreatic secretion cannot be judged from these results they show that the enzymes respond differently to weaning. In general the activity of the digestive enzymes in pancreatic tissue is low on day 5 postweaning which in interaction with other factors may increase the risk of developing postweaning diarrhoea.     

Influence of biogenic metals (Cu,Zn) on the activity of carbohydrases in juvenile fish in vitro

It was revealed that intestine and whole-body amylolytic activity (AA) in juvenile fish serving as potential feeding items for piscivores significantly decreases in the presence of Cu and Zn ions within a wide range (0.1–25 mg/l) of concentrations in vitro. In most of the studied fish species, Cu and Zn decrease the activities of carbohydrases in the intestine mucosa stronger than in the whole-body. On the other hand, in piscivore-facultative benthivore perch, which have the least AA, the inhibiting effect of Cu and Zn ions is 1.5 to 2 times higher in the whole body than in the intestine. The study data suggest that Cu and Zn ions at concentrations found in organisms that serve as fish food may not only reduce the rate of initial stages of carbohydrates hydrolysis in the juvenile fish intestine, but also considerably decrease the potential contribution of the food objects to the digestion processes in typical and facultative piscivores.     

Localization and origin of the intestinal peroxidase--effect of adrenal glucocorticoids

Peroxidase activity in rat intestine is stimulated two-fold after bilateral adrenalectomy and is reversed by dexamethasone (9-fluoro-11 beta,17,21-trihydroxy-16 alpha-methyl-1-4-pregnadiene-3,20-dione). The enzyme activity is inhibited on administration of various glucocorticoids of which dexamethasone acts as the most potent inhibitor of the enzyme in vivo. The change of enzyme activity results neither from alteration of the apparent Km of the enzyme nor from enzyme synthesis. Although a small amount of peroxidase is located in the intestinal epithelial cells, a large amount is present in the rest of the intestine. Histochemical studies indicate the presence of peroxidase in the lamina propria, the core of the intestinal villi which contains eosinophil. The peroxidase isolated from the epithelial cell-free intestine is similar to the peroxidase obtained from the pure eosinophil in terms of various physicochemical properties. Dexamethasone also inhibits the eosinophil peroxidase and decreases the number of both circulating and intestinal eosinophil. Studies indicate that a large part of the peroxidase of the intestine is contributed by invading eosinophil and dexamethasone inhibits the enzyme by sequestration of eosinophil both from intestine and blood possibly to the peripheral lymph nodes.     

Ontogenic and longitudinal activity of Na(+)-nucleoside transporters in the human intestine

The objectives of our study were to identify the types of nucleoside transporters present in the human fetal small intestine and to characterize their developmental activity, longitudinal distribution, and transport kinetics compared with those present in the adult intestine. Nucleoside uptake by intestinal brush-border membrane vesicles was measured by an inhibitor-stop rapid filtration technique. Only the purine-specific (N1; hCNT2) and the pyrimidine-specific (N2; hCNT1) Na(+)-dependent nucleoside transporters were found to be present on the brush-border membranes of the enterocytes along the entire length of the fetal and adult small intestines. The activity of these transporters was higher in the proximal than in the distal small intestine. Both the N1 and N2 transporters found in the fetal intestine shared similar kinetic properties (Michaelis-Menten constant and Na(+)-nucleoside stoichiometry) to those in the adult intestine. During the period of rapid morphogenesis (11-15 wk gestation), no temporal differences were apparent in the activity of the N1 and N2 transporters in the fetal small intestine. These findings have implications for the absorption of drugs from the amniotic fluid by the fetus after maternal drug administration of nucleoside drugs such as the antivirals zidovudine and didanosine.     

Distribution and biosynthesis of aminopeptidase N and dipeptidyl aminopeptidase IV in rat small intestine

The regional, cellular and subcellular distribution patterns of aminopeptidase N and dipeptidyl aminopeptidase IV were examined in rat small intestine. Aminopeptidase N of brush border membrane had maximal activity in the upper and middle intestine, while dipeptidyl aminopeptidase IV had a more uniform distribution profile with relatively high activity in the ileum. Along the villus and crypt cell gradient, the activity of both enzymes was maximally expressed in the mid-villus cells. However there was substantial dipeptidyl aminopeptidase IV activity in the crypt cells. Both enzymes were primarily associated with brush border membranes in all segments, however, in the proximal intestine, a significant amount of dipeptidyl aminopeptidase IV activity was associated with the cytosol fraction. The cytosol and brush border membrane forms of dipeptidyl aminopeptidase IV were immunologically identical and had the same electrophoretic mobility on disc gels. In contrast, the soluble and brush border membrane-bound forms of aminopeptidase N were immunologically distinct. When the total amount of aminopeptidase N and dipeptidyl aminopeptidase IV was determined by competitive radioimmunoassay, there were no regional or cellular differences in specific activity (enzyme activity/mg of enzyme protein) of either enzyme in brush border membrane and homogenate. The specific activity of both enzymes in a purified Golgi membrane fraction as measured by radioimmunoassay was about half that of the brush border membrane fraction. These results suggest that (1) aminopeptidase N and dipeptidyl aminopeptidase IV have different regional, cellular and subcellular distribution patterns; (2) there are enzymatically inactive forms of both enzymes present in a constant proportion to active molecules and that (3) a two-fold activation of precursor enzyme forms occurs during transfer from the Golgi membranes to the brush border membranes.     

Studies on L-arginase in developing rat small intestine, brain, and kidney. I. Ontogenic evolution of arginase isoenzymes

The adult patterns of arginase isoenzymes in rat intestine, kidney, and brain are nearly identical and consist of two forms, cationic A1 and anionic A4. In this paper, the organ-specific maturation of the enzyme equipment in these tissues is reported. The activity of arginase in all tissues studied could be detected on the 13th to 16th days of gestation. In fetal intestine and kidney the arginase activity is low, and persists up to the weaning time when the rapid, 10-fold rise of the enzyme activity occurs. However, the adult pattern of arginase isoenzymes in these tissues is accomplished in different ways. In the intestine, arginase A1 appears in fetal life and is the only form of the enzyme till the 19th to 21st days of postnatal life when the second form of arginase, A4, appears and rapidly accumulates, being exclusively responsible for the rise of the total enzyme activity at the time of weaning. In kidney, arginase A1 alone is present in the early fetal period. Arginase A4 appears 3-4 days before birth and its activity persists unchanged within the first 2 weeks of postnatal life. The intensive rise in total specific activity of kidney arginase at weaning is due to the accumulation of preexisting arginase A4. In brain, the adult pattern of arginase isoenzymes is achieved earlier than in other tissues. Both forms, A1 and A4, occur on Days 13-14 of gestation.