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Biomedical subjects

T Olivecrona

Publications and source records attributed to T Olivecrona.

At least 163 records · Page 9Linked to original sources
PubMed1978

The in vitro inhibition of bovine milk lipoprotein lipase by a glycoprotein preparation from human atherosclerotic intima.

Intimal tissue from human atherosclerotic aortae was collected by the Dermatome procedure. The tissue was extraved with 5 mM Tris.HCl buffer containing 0.3 M NaCl and 1 mM EDTA, pH 7.4. The ammonium sulfate precipitate between 0.4--0.8 saturation obtained from the extract was fractionated on a DEAE-cellulose column and the effluent was monitored for lipoprotein lipase inhibition employing purified bovine milk enzyme. The substrate used was an emulsion of purified olive oil and tritiated triolein. Human serum was the source of activator of the substrate. A peak of inhibitory activity was eluted between 0.15--0.17 M NaCl. The major component in the purified material had properties similar to a glycoprotein (lipolipin) which has previously been purified from porcine aorta and shown to inhibit lipoprotein lipase activity. The partially purified human inhibitor decreased both the basal and the serum-stimulated activity of milk lipoprotein lipase. The inhibition was non-competitive with respect to serum. However, high levels of triglyceride substrate appeared to relieve the inhibitory effect. It is postulated that the inhibitor may be involved in an interaction with the emulsified lipid denying the enzyme access to its substrate.

Animals↗
PubMed1978

Decrease of lipase and esterase activities in intestinal contents of newborn infants during test meals.

Both lipase and esterase activities were present in intestinal contents of all newborns studied, from the first day of life. In adults given a test meal lipase activity increased and esterase activity remained unchanged. In contrast, both activities decreased markedly in infants on feeding. During the digestion of the test meal the lipase activity in intestinal contents of the infants was much lower than in adults (ratio of median values 1:27) and the esterase activity was also several fold lower (ratio of median values 1:1.3). Speculation Newborn infants often absorb lipids less efficiently than adults. One contributing factor may be that their incompletely developed pancreas responds to feedings with comparatively low outputs of lipolytic enzymes. The newborn may be more dependent than adults on auxiliary sources of lipase activity such as the pharyngeal lipase and/or the bile-stimulated lipase in human milk.

Adult↗
PubMed1977

Interaction of lipoprotein lipase with heparin-Sepharose. Evaluation of conditions for affinity binding.

Lipoprotein lipases from a variety of sources have been shown previously to bind to heparin and some related polysaccharides. For the present studies lipoprotein lipase purified from bovine milk was used. 1. In batch experiments binding of the enzyme activity to heparin-Sepharose occurred relatively slowly, so that 30min was required for the system to come to near-equilibrium. In contrast, release of the enzyme activity from heparin-Sepharose by addition of salt to the liquid phase occurred rapidly. 2. Some binding was observed also with unsubstituted Sepharose, but this binding had a low capacity compared with that observed with heparin-Sepharose. High salt concentrations, heparin or deoxycholate decreased the binding to unsubstituted Sepharose. These factors also increase the solubility of the enzyme, which is low. 3. Addition of heparin to the liquid phase caused a concentration-dependent release of enzyme activity from the gel. These results suggested that the binding of the enzyme to heparin-Sepharose was mainly through interaction with heparin. 4. The enzyme activity was also quantitatively displaced to the liquid phase at increased concentrations of salt. Among the positive ions tested the following order of effectiveness was noted: Cs(+) approximately K(+)>Na(+)>Li(+); and among the negative the following: SCN(-)>I(-)> NO(3) (-)>Br(-) approximately Cl(-). The differences were quite large. Thus addition of 0.16m-KSCN (in addition to the 0.32m-NaCl originally present) displaced one-half of the enzyme activity to the supernatant, whereas 0.8m-LiCl only displaced one-quarter. 5. The distribution of heparin in the gel also profoundly influenced the binding. Two series of gels were studied. One series was made by mixing heparin-Sepharose with unsubstituted Sepharose. Results obtained with these gels were those expected from a series of decreasing volumes of heparin-Sepharose. In contrast, a series of heparin-Sepharoses made with different degrees of substitution gave quite different results. With these gels the amount of enzyme activity bound per amount of heparin increased markedly, whereas the salt concentration needed to displace the enzyme activity from the gel decreased markedly with decreased concentration of heparin in the gel. 6. On stepwise elution of small columns of heparin-Sepharose the enzyme activity was eluted over a remarkably wide range of salt concentrations. When enzyme eluted at one salt concentration was re-applied, it gave the same elution profile as enzyme previously eluted at other salt concentrations or the entire enzyme preparation. These and other results suggested that, whereas the enzyme preparation was rather homogeneous in its binding to heparin, the heparin preparation was polydisperse in binding of lipoprotein lipase.

Animals↗
PubMed1977

Protein components of very low density lipoproteins from hen's egg yolk.

Egg yolk lipoproteins of very low density were found to contain proteins with cofactor activity for lipoprotein lipase. When delipidated very low density lipoproteins were dissolved in 10 mM HCl and fractionated by gel filtration about two thirds of the protein were in several components with estimated molecular weights of 60000 to more than 170000. The major low-molecular-weight proteins were the dimeric and monomeric forms of a previously characterized 9000-dalton peptide. The cofactor activity was not associated with any of these major proteins. A large-scale fractionation method was developed by which two proteins fractions with cofactor activity for lipoprotein lipase were purified more than thousand-fold. One fraction had a molecular size of about 9000 daltons and the other had a size of about 5000 daltons. Both these fractions could be further separated on the basis of charge into several fractions with cofactor activity. The cofactor proteins were relatively soluble both at high and at low pH. The retained their cofactor activity after denaturation in guanidinium hydrochloride and after reduction. During the initial steps in the purification of the cofactor proteins another low-molecular-weight protein followed the cofactors. It had a single 17500-dalton peptide chain and was present in four variants, three of which contained carbohydrate.

Amino Acids↗
PubMed1977

Breast milk composition in Ethiopian and Swedish mothers. IV. Milk lipases.

The (potential) activities of the two lipases in human milk were determined in breast milk samples collected from Ethiopian and Swedish mothers. The major lipase in human milk is dependent on bile salts for activity and probably participates in intestinal digestion of milk lipids in the newborn. The level of this lipase in the milk did not change with time after parturition, but differed between the groups so that it was higher in the privileged Ethopian mothers than in the nonprivileged Ethiopian mothers, who in turn had a higher level than the Swedish mothers. The other lipase is a serum-stimulated lipase (lipoprotein lipase). The level of this lipase varied between samples from different mothers as well as between different samples from the same mother. It tended to be lower in samples obtained at 4 to 5 days after parturition (Swedish mothers) than in later samples. There were in this case no significant differences between nonprivileged and privileged Ethiopian mothers or between them and Swedish mothers.

Adolescent↗
PubMed1976

Very low density lipoprotein. Dissociation of apolipoprotein C during lipoprotein lipase induced lipolysis.

The fate of apo C in rat plasma very low density lipoprotein (VLDL) during lipolysis was studied using VLDL labeled specifically with 125I-labeled apo C and purified bovine milk lipoprotein lipase. Incubations were carried out in vitro and included serum-containing systems and albumin containing systems. Free fatty acids generation proceeded with time of incubation in the two systems. It, however, was enhanced 1.5--2 fold by the presence of serum. 125I-labeled apo C equilibrated between very low and high density lipoprotein (HDL) in both systems even when enzyme was not present in the incubation medium, or when the incubation was carried out at 0 degrees C. Upon initiation of lipolysis, more 125I-labeled apo C was transferred to HDL and the transfer was proportional to the magnitude of free fatty acids release. 125I-labeled apo C was also progressively removed from VLDL in the albumin-containing system, although no known lipoprotein acceptor to apo C was present in the medium. The 125I-labeled apo C was recovered predominantly with the medium fraction of d greater than 1.21 g/ml (60--70%), and to a lesser degree with that of d= 1.019--1.21 g/ml. However, the relationship between lipolysis (measured as free fatty acids release) and removal of 125I-labeled apo C from VLDL were indistinguinshable in the albumin containing system and the serum containing system. On the basis of these observations, it is postulated that the removal of apo C during lipolysis of VLDL reflects the nature of the partially degraded VLDL particles, and is independent of the presence of a lipoprotein acceptor to apo C.

Albumins↗
PubMed1976

Metabolism of liver triacylglycerols in rats tube-fed a threonine-devoid diet.

Rats tube-fed a diet devoid of threonine accumulated triacylglycerols in their livers, starting on the third day of the diet. The fatty acid composition of the accumulated lipid and the contribution of novo synthesized fatty acids to the lipid accumulation, as determined with tritiated water as a radioactive precursor for fatty acid synthesis, suggested that an increased hepatic de novo synthesis of fatty acids is not a major factor for the development of this liver lipid accumulation. The metabolism of intravenous injected 3H-oleic acid, the Triton-induced hyperlipemia and the activity of lipoprotein lipase in adipose tissue was also studied. None of these studies revealed any significant difference between the threonine-deficient and control rats. It is concluded that the hepatic triacylglycerol accumulation in the threonine-deficient rats does not result from any gross abnormality in the rate of liver triacylglycerol formation or secretion to the plasma. It is suggested that a possible causative mechanism is a derangement in the metabolism of the storage pool of liver triacylglycerols.

Adipose Tissue↗
PubMed1976

Human milk lipases and their possible role in fat digestion.

Human milk contains two lipases. One is a lipoprotein lipase with properties similar to the lipoprotein lipases that participate in the metabolism of blood plasma lipoproteins in several tissues. This enzyme is present in high activity in the lactating mammary gland where it facilitates the uptake of triglyceride fatty acids from the blood lipoproteins for production of milk lipids in the gland. The high activity of this enzyme in milk probably represent leakage of enzyme from the gland. This lipase is not stable at pH below 5 or in intestinal contents and it is unlikely that it participates in intestinal fat digestion. Its activity varies widely between individual milk samples, and there is a high correlation between its activity and the development of hydrolytic rancidity in the milk on storage. The other lipase is present in the milk in an inactive form which is activated by bile salts. This lipase is present in milk from primates but not in milk from lower animals. Human milk contains enough of this lipase to hydrolyze the milk lipids almost completely in less than half an hour at the pH and the bile acid and salt concentrations found in the small intestine of the human infant. It is probable that it increases the efficiency of milk fat absorption. The enzyme has a rather wide substrate specificity and may also act on other lipid substrates than triglycerides. In contrast to pancreatic lipase it hydrolyses all three ester bonds in a triglyceride. This may affect the physical chemistry of the lipids in the intestinal contents as well as their absorption and further metabolism in the musoca.

Bile Acids and Salts↗
PubMed1975

Serum-stimulated lipases (lipoprotein lipases). Immunological crossreaction between the bovine and the human enzymes.

A rabbit antiserum prepared against the serum-stimulated lipase (lipoprotein lipase) from bovine milk crossreacted with serum-stimulated lipases from human milk and from human postheparin plasma, but not with bile salt-stimulated lipase from human milk or with salt-resistant lipase from human postheparin plasma. Thus, the serum-stimulated lipase in bovine milk has immunological determinants in common with the serum-stimulated lipases in human milk and in human postheparin plasma. The time-courses for the appearance of serum-stimulated lipase and salt-resistant lipase activities in human plasma after heparin injection were different. The two activities were separated by heparin-Sepharose chromatography. After treatment of postheparin plasma with the antiserum only the salt-resistant lipase activity could be eluted from the column. Thus, these two enzyme activities in postheparin plasma reside in two different enzyme molecules.

Animals↗
PubMed1975

Effect of ethanol on utilization of plasma free fatty acids for liver triacylglycerol synthesis and its relation to hepatic triacylglycerol accumulation in rats.

The effect of 3 different single doses of ethanol on the liver triacylglycerol concentration and on the metabolism of intravenously injected 14C-oleic acid in fasted rats was studied. All 3 doses (2, 3.75, and 6 g ethanol/kg body wt) caused a rapid increase in the liver triacylglycerol concentration during the first 5-6 hr after the ethanol was given. Until the plasma ethanol concentration had fallen to low values, the high liver triacylglycerol levels were raised and were independent of the ethanol dose given. The incorporation of radioactivity from intravenously injected 14C-oleic acid into liver triacylglycerols was increased over control values to the same extent in all rats given ethanol as long as the plasma ethanol concentration was above a low level. High rates of ethanol oxidation and increased utilization of plasma free fatty acids for liver triacylglycerol synthesis were closely correlated with the development and maintenance of the ethanol induced liver triacylglycerol accumulation.

Animals↗
PubMed1975

Lipases in bovine milk and the relationship between the lipoprotein lipase and tributyrate hydrolysing activities in cream and skim-milk.

The lipoprotein lipase and tributyrate hydrolysing activities were found to be similarly distributed in the fractions obtained when whole milk was separated into skim-milk and cream, and when the cream was washed and freed from lipid. These enzyme activities in skim-milks and in extracts of lipid-free cream could not be separated by affinity chromatography on heparin-Sepharose. The enzymes were inactivated to the same degree when incubated at 37 degrees C in the presence of 1-5 M-NaCl, pH 8-5, and both showed marked decrease in stability at 4 degrees C in UV-light caused the same decrease in both lipoprotein lipase and tributyrate hydrolysing activities. An antiserum against a highly purified skim-milk lipoprotein lipase caused total inhibition of the lipoprotein lipase and tributyrate hydrolysing activities in skim-milk and in extracts of lipid-free cream. It is suggested that in bovine milk there is only one major lipase and that it is identical to lipoprotein lipase.

Animals↗