Biomedical subjects

B Sternby

Publications and source records attributed to B Sternby.

At least 37 records · Page 2Linked to original sources

PubMed1995

Time-course of the pancreatic changes following long-term stimulation or inhibition of the CCK-A receptor.

Cholecystokinin (CCK) reportedly induces both hyperplastic and hypertrophic changes in the pancreas. Blockade of the CCK receptor results in decreased pancreatic secretion and atrophy. The aim of this study was to evaluate the time-course of the effects of stimulation and inhibition of the CCK-A receptor in the rat exocrine pancreas. Male rats had infusion of sulfated CCK-8, the CCK-A receptor antagonist devazepide, or sodium chloride by osmotic minipumps. After 36 h, 3, 7, or 28 d the rats had ip injections of thymidine, and 1 h later they were sacrificed. The pancreas was excised, weighed, and its content of protein, DNA, water, and enzymes was analyzed. Histologic samples were prepared for autoradiography. Pancreatic weight, protein, and DNA were increased at 36 h after the start of CCK infusion and throughout the study period. CCK stimulation also increased the content of trypsin at days 3 and 28. The labeling index of pancreatic acinar cells was increased at 36 h. Blockade of endogenous CCK by the receptor antagonist devazepide led to decreased pancreatic weight from the third day of infusion, whereas the protein content was decreased from the seventh day. At day 28, the DNA content was decreased by devazepide. However, the labeling index of acinar cells decreased transiently already at 36 h. Neither CCK nor devazepide caused any changes of protein content:DNA content ratio during the study. Continuous infusion of CCK caused pancreatic hyperplasia already after 36 h. Stimulation up to 28 d did not cause any further effects. The adverse changes found after blockade of the CCK-A receptor showed much of the same time-course.

Animals↗

PubMed1995

Low doses of pentagastrin stimulate gastric lipase secretion in man.

BACKGROUND: Gastric lipase is an important enzyme for dietary triglyceride digestion in normal subjects. Its regulation is unknown, as is the relation between the quantity and activity of the enzyme. METHODS: In a dose-response study we investigated the effect of low doses of pentagastrin (less than 1000 ng/kg/h) on the output of gastric lipase measured by a kinetic assay and an enzyme-linked immunosorbent assay (ELISA). RESULTS: In five healthy volunteers stepwise intravenous pentagastrin infusions of 0, 50, 100, 500, and 1000 ng/kg/h resulted in a stepwise increase in the lipase output, as measured with ELISA. However, the lipolytic activity, measured with a kinetic assay, decreased as the pH of the gastric contents decreased. CONCLUSION: We conclude that secretion of the gastric lipase is stimulated by pentagastrin, but the simultaneous secretion of acid counteracts the lipolytic activity of the enzyme when food is not present.

Adult↗

PubMed1995

Hydrolysis of galactolipids by human pancreatic lipolytic enzymes and duodenal contents.

Monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG) and sulfoquinovosyldiacylglycerols (SQDG) are major lipids in vegetable food. Their digestion and absorption are unknown. This study examines the hydrolysis of galactolipids in vitro with human duodenal contents, pancreatic juice, and purified human pancreatic lipases. Galactolipids were incubated with human duodenal contents, pancreatic juice, pure pancreatic carboxyl ester lipase (CEL), and colipase-dependent lipase with colipase (Lip-Col). Hydrolysis was estimated as release of free fatty acids and by the use of [3H]galactose or [3H]fatty acid-labeled DGDG. Pancreatic juice and duodenal contents hydrolyzed DGDG to fatty acids, digalactosylmonoacylglycerol (DGMG) and water-soluble galactose-containing compounds. The hydrolysis of DGDG was bile salt-dependent and had a pH optimum at 6.5-7.5. Human pancreatic juice released fatty acids from MGDG, DGDG, and SQDG. Purified CEL hydrolyzed all three substrates; the hydrolysis rate was MGDG > SQDG > DGDG. Pure Lip-Col had activity toward MGDG but had little activity against DGDG. Separation of pancreatic juice by Sephadex G100 gel filtration chromatography revealed two peaks with galactolipase activity that coincided with CEL (molecular mass 100 kD) and lipase (molecular mass 50 kD) peaks. In contrast to pure Lip-Col enzymes of the latter peak were as active against DGDG as against MGDG. Thus, DGDG is hydrolyzed both by CEL and by a pancreatic enzyme(s) with a molecular mass of 40-50 kD to fatty acids and lyso DGDG. MGDG, DGDG, and SQDG are all hydrolyzed by human pancreatic juice. Pure CEL hydrolyzed all three substrates.

Bile Acids and Salts↗

PubMed1994

Digestion of triacylglycerols containing long-chain polyenoic fatty acids in vitro by colipase-dependent pancreatic lipase and human milk bile salt-stimulated lipase.

To assess the role of human milk bile salt-stimulated lipase (BSSL) in the digestion of polyunsaturated ester bonds of triacylglycerols, hydrolysis of docosahexaenoic acid (22:6(n-3)) ester bonds was compared to that of oleic acid (18:1(n-9)) or arachidonic acid (20:4(n-6)) esters. As model substrates, we used rat chylomicrons obtained after feeding human milk fat globules and radiolabeled fatty acids. Radiolabeled chylomicrons were incubated with colipase-dependent pancreatic lipase, with BSSL, or with both enzymes in combination. Both enzymes hydrolyzed 18:1 more efficiently than 22:6 esters. With colipase-dependent lipase there was a large accumulation of 22:6 in diacylglycerol whereas with BSSL it accumulated mainly in monoacylglycerol. Esters containing 20:4 were hydrolyzed by BSSL as efficiently as 18:1 but this fatty acid also accumulated as diacylglycerol with colipase-dependent lipase. At low bile salt concentrations, as found in duodenal contents of newborns, colipase-dependent lipase was virtually unable to hydrolyze esters of 20:4 and 22:6 whereas BSSL hydrolyzed these esters at appreciable rates. Combining the two enzymes gave the most efficient hydrolysis of all fatty acids tested regardless of bile salt concentrations. BSSL may thus have a physiological role in completing duodenal hydrolysis of milk triacylglycerols containing 22:6- or 20:4-esters to free fatty acids and monoacylglycerol.

Arachidonic Acid↗

PubMed1994

Hydrolysis of phosphatidylethanolamine by human pancreatic phospholipase A2. Effect of bile salts.

The 2-ester bond of 14C-2-arachidonyl phosphatidylethanolamine (PE) was hydrolyzed faster than that of 3H-2-arachidonyl phosphatidylcholine (PC) by human pancreatic phospholipase A2 (PLA2) with mixed PE-PC (1:9 w/w) liposomes of pure sonicated PE or PC as substrate. The PC portion of the mixed PE-PC liposomes was more readily attacked by PLA2 than the PC of pure PC liposomes. At different bile salt concentrations (sodium taurocholate (NaTC), 0-3 mM, and sodium taurodeoxycholate (NaTDC), 0-4 mM) the rates of hydrolysis varied with similar patterns for both phospholipids of the mixed liposomes. The rate of hydrolysis was optimal at a bile salt concentration of 0.75-1.5 mM NaTC and 1.0-2.0 mM NaTDC and decreased at higher concentrations. The pure PE substrate was efficiently hydrolyzed also without bile salts. This may have implications for the absorption of polyunsaturated phospholipid fatty acids in patients with bile salt deficiency. Separation of phospholipid classes from human bile by high-performance liquid chromatography and analysis of fatty acid composition indicated that PE contained 5.3% of the phospholipid arachidonic acid and 9.8% of the docosahexaenoic acid mass, but only 1.7% of the total phospholipid mass. Bile and dietary PE should not be overlooked as sources of arachidonic and docosahexaenoic acid for the small intestine.

Bile↗

PubMed1993

Does the bile salt-stimulated lipase of human milk have a role in the use of the milk long-chain polyunsaturated fatty acids?

Long-chain polyunsaturated (LCP) fatty acids derived from linoleic (18:2 n-6) and alpha-linolenic (18:3 n-3) acids are considered essential nutrients in preterm infants. The efficiency by which such fatty acids are released as absorbable products from triacylglycerol was explored in vitro using rat chylomicron triacylglycerol as substrate. When incubated with purified human pancreatic colipase-dependent lipase and colipase, arachidonic acid (20:4 n-6) was released less efficiently than linoleic acid from such triacylglycerol. This difference was not seen when purified human milk bile salt-stimulated lipase (BSSL) was incubated with the triacylglycerol substrate, and it was almost abolished when colipase-dependent lipase (with colipase) and BSSL acted simultaneously, as they do in breast-fed infants. There was no difference in arachidonic acid and eicosapentaenoic acid (20:5 n-3) release rates with either colipase-dependent lipase or BSSL, albeit the release was more rapid with the milk enzyme than with colipase-dependent lipase. Again, the most efficient release as absorbable free fatty acids was achieved when the two lipases operated together. The relative resistance to hydrolysis of arachidonic acid and eicosapentaenoic acid by colipase-dependent lipase was best explained by the localization of the first double bond to the delta-5 position of the respective fatty acid. The results obtained suggest that BSSL is of importance for the efficient use of human milk LCP fatty acids.

Animals↗

PubMed1993

Purification of lipase and other lipolytic enzymes from the human pancreas.

A pure lipase has been isolated from extracts of the human pancreas. The purification process includes centrifugation, two ion-exchange chromatography steps, and one gel filtration step. Compared with other reports, a high recovery, large amounts, and a high specific activity were obtained. Lipase is present at 1-2 mg/g in the pancreatic gland. In the absence of colipase and bile salts with tributyrine as substrate, the specific activity at room temperature and at pH 7.0 is 4000 mumol/min/mg. It increases to 8000-10,000 in the presence of colipase and bile salts at a temperature of 37 degrees C. The fate of the other human lipolytic proteins during the different purification steps is also indicated. Lipase purified by this method has been used for crystallization.

Chromatography, Agarose↗

PubMed1993

Decrease in contents of pancreatic carboxyl ester lipase, phospholipase A2, and lingual lipase in rats with streptozotocin-induced diabetes.

The changes in contents of pancreatic carboxyl ester lipase, phospholipase A2, and lingual lipase in rats with streptozotocin (STZ)-induced diabetes have been studied. The contents of pancreatic carboxyl ester lipase and phospholipase A2 decreased by 40% and 45%, respectively, 5 days after injection of STZ, whereas pancreatic lipase steadily increased to 100% over control. The content of lingual lipase decreased sharply by more than 90% 2 days after STZ injection, followed by a tendency to recover slightly. Insulin treatment at a dose abolishing the urine glucose in diabetic rats for 3 days restored the contents of pancreatic lipase, carboxyl ester lipase, and lingual lipase but not pancreatic phospholipase A2. The results indicate that lack of insulin action induces an anticoordinate change in gastrointestinal lipolytic enzymes, with decreases in pancreatic carboxyl ester lipase, phospholipase A2, and lingual lipase contents and an increase in pancreatic lipase content.

Animals↗

PubMed1992

Hyperphospholipasemia A2 in human volunteers challenged with intravenous endotoxin.

Phospholipase A2 (PLA2) activity was measured in the serum of 23 individuals infused intravenously with endotoxin (EN) at a dose of 4 ng/kg body weight. A marked increase in PLA2 was noted 3 h after EN challenge (mean 828 +/- 513 units/ml), reached its maximum at 24 h after the challenge (mean 2667 +/- 2442 units/ml), and was still evident at 48 h (mean 763 +/- 366 units/ml). In contrast, TNF levels were maximal (mean 712 +/- 375 pg/ml) 90 min after the EN challenge and subsided to very low values (5 +/- 5 pg/ml) 5 h after the challenge. There was a positive correlation between the maximum response of TNF and that of PLA2 (r = 0.82, P < 0.01). Administration of ibuprofen or pentoxifylline did not alter the PLA2 response. EN challenge did not affect serum pancreatic PLA2 concentration or that of the lysosomal cationic enzyme, lysozyme. Neutralizing antibody against human recombinant (synovial type) PLA2 completely abolished PLA2 activity in the sera tested. We conclude that EN infusions cause marked intravascular release of nonpancreatic secretory PLA2 and that the magnitude of this response seems to be related to the prior generation of TNF.

Endotoxins↗

PubMed1991

How to protect human pancreatic enzyme activities in frozen duodenal juice.

We determined whether activity of pancreatic enzymes could be maintained in frozen duodenal juice by diluting the specimens or by adding nutrients or a chymotrypsin inhibitor. Human duodenal juice was obtained during cholecystokinin octapeptide IV administration. Trypsin, chymotrypsin, lipolytic, lipase, and colipase activities were measured in fresh undiluted or diluted (1:4 and 1:16 with saline and T-tube bile) duodenal juice as well as after adding CaCl2, casein, triolein, or a chymotrypsin inhibitor. Subsequently, the samples were frozen at -20 degrees C, and enzyme activities were measured at 1, 2, 3, 7, 14, 28, and 56 days. Activities of chymotrypsin and colipase did not change during freezer storage. Trypsin survival was variable in juice from different subjects. By contrast, in duodenal juice to which no nutrient or only CaCl2 had been added, 90%, 65%, and 40% (P = 0.05 vs. undiluted) of lipolytic activity was lost by 56 days in undiluted and 1:4 or 1:16 diluted duodenal juice samples, respectively. The loss of lipolytic activity was prevented (P less than 0.05) by adding casein or casein and triolein to undiluted and 1:4 diluted samples and turkey egg white to undiluted samples. The loss of lipolytic activity was strongly associated with loss of lipase activity (r = 0.97) but only weakly associated with loss of colipase activity (r = 0.49). In summary, chymotrypsin and colipase are well preserved in frozen duodenal juice and can be used to accurately assess concentrations of pancreatic enzymes after thawing frozen duodenal samples. If it is necessary to measure lipolytic activity after freezing samples, lipase can be maintained by adding casein or a chymotrypsin inhibitor to juice before freezing.

Colipases↗

PubMed1991

Pancreatic lipolytic enzymes in human duodenal contents. Radioimmunoassay compared with enzyme activity.

The total pancreatic lipolytic capacity was determined in duodenal contents in healthy humans 10-120 min after a liquid test meal, by estimating the amount of pancreatic lipase, colipase, carboxyl ester lipase, and phospholipase A2 by means of radioimmunoassays and enzymatic assays. The molar concentrations of the different proteins were of the same order of magnitude. The relative specific activity (enzyme activity/milligram immunoreactive protein expressed as a percentage of the specific activity of the respective pure protein) amounted to 75-120% for lipase, 45-80% for colipase, 30-70% for carboxyl ester lipase, and 45-120% for phospholipase A2. These varied, and sometimes low values can be explained by the fact that the enzymes are inhibited or partly inactivated in the duodenal contents by surface denaturation, in which cases the products are still immunoreactive. Also, the proforms of colipase and phospholipase A2 may not always be completely activated. Furthermore, the specific activities of the pure enzymes (and thus the relative specific activities) are related to the methods used, which are not specific enough to distinguish completely the three enzymes and the cofactor in duodenal contents.

Adult↗

PubMed1991

cDNA cloning of carboxyl ester lipase from human pancreas reveals a unique proline-rich repeat unit.

We report the isolation and nucleotide sequence of the cDNA for carboxyl ester lipase (CEL) from human pancreas. CEL was purified from human pancreas and microsequence analysis was performed on the amino-terminal and internal peptides. Peptide sequence was used to design oligonucleotide probes for screening a human pancreas cDNA library. Partial length cDNAs for CEL were isolated from the library, and the 5' portion of the cDNA was obtained using the anchored polymerase chain reaction. The deduced amino acid sequence indicates that mature CEL contains 722 amino acids and is synthesized with a 20 amino acid leader peptide. The amino acid sequence is rich in proline (12.2%), with 68% of the proline residues occurring within the final 25% of protein length. This is due to the occurrence of a series of proline-rich tandem repeat units near the carboxyl terminus, and accounts for the previously observed species variation in CEL size and amino acid composition. The primary sequence of CEL shows strong similarity to members of the serine esterase family, including the identical G-E-S-A-G motif at the putative active site. A striking homology also occurs between CEL and acetylcholinesterase and cholinesterase, essential enzymes of the nervous system. Proteins with cholesteryl esterase activity have been detected in extra-pancreatic tissues including liver, intestine, kidney, aorta, macrophage, and in the milk of some species (human, gorilla, cat, dog), but not others (rat, cow). To clarify the structural relationships between these various esterases and CEL, we used the CEL cDNA to study expression in pancreas and liver. CEL mRNA was abundant in pancreas of human and rat, with the human CEL mRNA approximately 300 nucleotides larger than that from rat. CEL mRNA was not detected in human adult or fetal liver, nor in rat liver. These results indicate that CEL is not synthesized in significant amounts in liver, and suggest that the cholesterol esterase activity that has been described in liver may be due to a distinct enzyme, or may be derived from pancreas, as has been proposed for the cholesterol esterase activity in intestine.

Amino Acid Sequence↗

PubMed1990

Effects of human pancreatic lipase-colipase and carboxyl ester lipase on eicosapentaenoic and arachidonic acid ester bonds of triacylglycerols rich in fish oil fatty acids.

Fish oil chylomicrons, obtained from mesenteric duct chyle of rats fed [3H]20:5 and [14C]20:4 or [3H]20:5 and [14C]18:2 in a fish oil emulsion, were incubated with human pancreatic lipase-colipase, human carboxyl ester lipase (CEL) and human duodenal contents. With duodenal contents, the triacylglycerols labelled with [3H]20:5 and [14C]20:4 were rapidly converted to free fatty acids (FFA) and monoacylglycerols. Also during incubation with lipase-colipase the [3H]- and [14C]triacylglycerols disappeared completely and at equal rates, but in this case much [3H]20:5 and [14C]20:4 accumulated in diacylglycerols. When CEL was also added, the rate of disappearance of [3H]- and [14C]triacylglycerols increased and the radioactivity of diacylglycerols decreased markedly. During incubation of chylomicrons labelled with [3H]20:5 and [14C]18:2 with lipase-colipase, the rates of hydrolysis of [3H]- and [14C]triacylglycerols were similar, but more [3H]20:5 than [14C]18:2 accumulated in diacylglycerols. The accumulation of [3H]diacylglycerol was reduced by adding CEL. Also when fatty acids were analyzed by gas chromatography, 20:5 was enriched in remaining triacylglycerol and in diacylglycerol after incubation with lipase-colipase alone. The data thus indicate that both lipase-colipase and CEL participate in the hydrolysis of 20:5 and 20:4 ester bonds of dietary triacylglycerol.

Animals↗

PubMed1990

Compartmental heterogeneity of soluble phospholipases A.

Multiple forms of soluble phospholipase A2 (PLA2) are known to coexist in venoms of individual reptilian species. While similar observations in several mammalian species suggest that this is a common phenomenon, the functional implications are not yet understood. In attempting to devise therapeutic strategies for treatment of inflammatory disorders by inhibition of PLA2, it is imperative to define the various PLA2 species in the relevant compartments. Herein, we report the presence of three PLA2 isotypes in rheumatoid arthritis serum, one pancreatic and two nonpancreatic phospholipases A2. The pancreatic and one of the nonpancreatic forms were optimally active in 7 mM calcium at pH 7.5. The other nonpancreatic form was calcium-independent and optimally active at pH 7.0. Only the calcium-dependent nonpancreatic form was observed in rheumatoid synovial fluid. Of the three serum isotypes, only the calcium-dependent nonpancreatic form correlated with markers of disease activity, such as the joint count and Landsbury index. Therefore, not all soluble or circulating phospholipases A2 are relevant to inflammatory processes. Selective inhibition of the proinflammatory form of PLA2 may prove to have some therapeutic benefit while minimizing the possible adverse effects of this form of intervention.

Arthritis, Rheumatoid↗

PubMed1990

Phospholipase A2 activity and concentration in several body fluids in patients with acute pancreatitis.

According to recent studies, phospholipase A2 (PLA2) may be an important factor in the pathogenesis and pathophysiology of acute pancreatitis. Increased serum PLA2 activities and concentrations have been measured in patients with acute pancreatitis. Serum PLA2 activities have been shown to correlate with the severity and prognosis of the disease. To study the different methods of PLA2 determination, we measured the PLA2 activity by means of an isotopic assay method and the concentration by a radioimmunologic method in several body fluids of 52 consecutive patients with acute pancreatitis. PLA2 activity and concentration were detected in all of the patient body fluids. The serum PLA2 activities were 2.5-fold higher (mean +/- SD, 7.6 +/- 6.0) than normal activities, and the concentrations were 9.6-fold higher (mean +/- SD, 41 +/- 88). The enzyme activities and concentrations correlated well in ascites, fluids from the pleural cavity, and peritoneal lavation and poorly in serum, urine, and fluid from pancreatic pseudocyst.

Acute Disease↗

PubMed1990

Hydrolysis of phosphatidylinositol by human pancreatic phospholipase A2.

Pure human pancreatic phospholipase A2 efficiently hydrolyzed the 2-ester bond of 14C-2-linoleoyl and 14C-2-arachidonyl phosphatidylinositol (PI). The rate of hydrolysis varied markedly with the bile salt (sodium taurocholate to sodium taurodeoxycholate, 3:4 mol/mol) concentration, the hydrolysis being decreased with increasing bile salt to PI ratio. The influence of bile salts was thus similar to that which has earlier been described for the hydrolysis of phosphatidylcholine (PC) with pig pancreatic phospholipase A2. When 2-3H-arachidonyl PC and 2-14C-arachidonyl PI were incorporated into a mixed substrate, PI was hydrolyzed even faster than PC, the hydrolysis of both phospholipids varying in the same manner with bile salt concentration. 2-14C-arachidonyl PI was also efficiently hydrolyzed by human duodenal content, although at a somewhat slower rate than 2-3H-arachidonyl PC. It is concluded that PI is a good substrate for human phospholipase A2. This minor but arachidonate-rich dietary phospholipid may thus be digested and absorbed by pathways similar to those of the major dietary and bile phospholipid, phosphatidylcholine.

Bile Acids and Salts↗

PubMed1990

Hypophospholipasemia A2 in systemic sclerosis.

Phospholipase A2 (PLA2), total and pancreatic, were quantitated in 91 sera of patients with systemic sclerosis (SSc). The mean total PLA2 of 216 +/- 161 U/ml (SD) was significantly lower (p less than 0.001) than in controls (317 +/- 128 U/ml). In 55 of 91 patients (60%) PLA2 was more than 1 SD and in 6 (7%) more than 2 SD below the normal mean. Serum pancreatic PLA2 was also significantly lower in SSc. The prevalence of low serum total PLA2 was significantly greater (p less than 0.001) than in healthy adults, or in patients with rheumatoid arthritis, systemic lupus erythematosus or vasculitis. Repeat assays of PLA2 activity in 10 patients with SSc documented persistence of low PLA2. Among 76 patients with SSc with complete clinical and laboratory assessment, there were 48 with low and 28 with normal (or slightly elevated) PLA2. These 2 groups showed no differences in disease manifestation or therapy. The group with low serum PLA2 had lower erythrocyte sedimentation rates (p less than 0.0005) and lower neutrophil (p less than 0.05) and monocyte counts (p less than 0.025) in the peripheral blood. The finding of low serum PLA2 activity adds to the spectrum of arachidonic acid pathway abnormalities associated with SSc, and may in part be related to the paucity of inflammatory changes observed in this disease.

Adult↗

PubMed1989

Hydrolysis of triacylglycerol arachidonic and linoleic acid ester bonds by human pancreatic lipase and carboxyl ester lipase.

The hydrolysis of polyenoic fatty acid ester bonds with pure human colipase-dependent lipase, with carboxyl ester lipase (CEL) and with these enzymes in combination was studied, using [3H]arachidonic- and [14C]linoleic acid-labelled rat chylomicrons as a model substrate. During the hydrolysis with colipase-dependent lipase, the amount of 3H appearing in 1,2-X-diacylglycerol (DG) markedly exceeded that of 14C. When CEL was added in addition this [3H]DG was efficiently hydrolyzed. CEL alone hydrolyzed the triacylglycerol (TG) at a low rate. The hydrolysis pattern with human duodenal content was similar to that seen with colipase-dependent lipase and CEL in combination. Increasing the concentration of taurodeoxycholate (TDC) and taurocholate (TC) or of TDC alone stimulated the hydrolysis of [3H]- and [14C]TG, but increased the accumulation of labelled DG that could act as substrate for CEL. It is suggested that very-long-chain polyenoic fatty acids of DG formed during the action of the colipase-dependent lipase on TG containing these fatty acids may be a physiological substrate for CEL.

Arachidonic Acid↗