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Biomedical subjects

O Hernell

Publications and source records attributed to O Hernell.

At least 109 records · Page 6Linked to original sources
PubMed1985

Sjögren-Larsson syndrome: delta 5-and delta 6-fatty acid desaturases in skin fibroblasts.

Cultured skin fibroblasts from two patients with Sjögren-Larsson syndrome (SLS) and from a normal control were analyzed for trienoic and tetraenoic fatty acids. In addition, we assayed desaturation of [1-14C]linoleic acid in cells from four patients and four controls. There was no significant effect of the disease on the composition of polyunsaturated fatty acids or on the rate of linoleic acid desaturation in fibroblasts. The results indicate the presence of delta 5- and delta 6-fatty acid desaturases in cells from SLS patients.

Adult↗
PubMed1983

Further characterization of the bile salt-stimulated lipase in human milk.

Bile salt-stimulated lipase is a milk enzyme unique to the higher primates. Its molecular and kinetic characteristics differ greatly from other lipolytic enzymes; e.g., pancreatic lipase and lipoprotein lipase. It has a much higher app. Mr, 310000 on gel filtration and 100000 after denaturation. It requires primary bile salts for optimal activity and bile salts also protect the enzyme from proteolytic and heat inactivation. It may, due to its low substrate specificity, contribute to the utilization of a variety of milk lipids. Since it lacks positional specificity, digestion of milk triglycerides should be complete, which may explain why fat absorption is more efficient in breast-fed than in formula-fed infants.

Bile Acids and Salts↗
PubMed1982

Lingual lipase. Its role in lipid digestion in infants with low birthweight and/or pancreatic insufficiency.

At birth both pancreatic lipase and carboxylic ester hydrolase, two important lipolytic enzymes secreted by the pancreas, are present in duodenal contents but the activities of these enzymes are low. Another enzyme of possible importance in lipolysis is the lingual lipase which is secreted from serous glands present at the posterior part of the tongue. The enzyme is present already at birth and has been found in gastric contents from preterm infants in the 34th gestational week. The secretion of lingual lipase is stimulated by feeding and it is resistent against acid inactivation. The activity in gastric contents increases after feeding. This lipase hydrolyzes dietary triglycerides to mainly diglycerides and free fatty acids and may serve as a complement to the poorly developed pancreatic lipase activity. Furthermore, by the formation of polar lipolytic products the digestibility of dietary lipids in the duodenum may increase. Human milk lipase contributes to the lipolysis. It is inactive in the milk but becomes activated by the bile acids in the duodenum. Balance studies in preterm infants have shown that by pasteurization of human milk fat absorption decreases by one third.

Bile Acids and Salts↗
PubMed1982

Suspected faulty essential fatty acid metabolism in Sjögren-Larsson syndrome.

The aim of the present study was to examine the fatty acid patterns of plasma phospholipids, cholesteryl esters, triglycerides and free fatty acids in patients with Sjögren-Larsson syndrome in order to detect whether absorption or metabolism is essential fatty acids may be abnormal. The fatty acid patterns were analyzed by gas liquid chromatography. The proportions of 23 fatty acids were calculated. The parameters used for assessment of the essential fatty acid metabolic status were calculated and compared with those from a group of institutionalized mentally retarded patients and from a group of healthy controls. There was no significant difference in either the fatty acid components or parameters used to evaluate the essential fatty acid metabolic study when the mentally retarded and control groups were compared. The relative concentration of linoleic acid (18:2 omega 6) in plasma phospholipids in patients with Sjögren-Larsson syndrome did not differ significantly from that of the healthy or mentally retarded controls, indicating that the Sjögren Larsson syndrome does not involve a dietary essential fatty acid deficiency or a defect in absorption of linoleate. In the phospholipids of Sjörgren-Larsson syndrome patients, the metabolites derived from linoleic acid were found to be significantly lower than in health controls, suggesting the metabolic defect. The total products of delta 6 desaturation were reduced to 3% of that in controls, whereas the products of delta 5 and delta 9 desaturation were not noticeably affected in the patients with Sjögren-Larsson syndrome. All individuals with Sjörgren-Larsson syndrome exhibited decreased products of delta 6 desaturation which also affected subsequent metabolites in the metabolite sequence.

Adolescent↗
PubMed1982

Digestion of human milk lipids: physiologic significance of sn-2 monoacylglycerol hydrolysis by bile salt-stimulated lipase.

The bile salt-stimulated lipase secreted with human milk was found to be devoid of positional specificity, i.e., it hydrolyzed emulsified triacylglycerols to glycerol and fatty acids. It also hydrolyzed micellar sn-2 monoacylglycerols. This is in contrast to pancreatic lipase which has a pronounced preference for hydrolysis of sn-1 and sn-3 ester bonds. When the two enzymes were operating together, as in the intestine of the infant fed raw human milk, the sn-2 monoacylglycerols formed by pancreatic lipase served as an excellent substrate for bile salt-stimulated lipase. Thus, the end products of triacylglycerol hydrolysis became glycerol and fatty acids and not sn-2 monoacylglycerol and fatty acids. The bile salt-stimulated lipase also catalyzed incorporation of fatty acids into acylglycerols to a much lesser extent than did pancreatic lipase. Together these two effects of bile salt-stimulated lipase have a promoting effect on the overall process of intraluminal lipolysis. In newborn infants, with low intraduodenal bile salt concentrations, glycerol and fatty acids also should be more readily absorbed than monoacylglycerol and fatty acids. Thus, by serving as a complement to pancreatic lipase, bile salt-stimulated lipase can ensure efficient utilization of milk lipids also in infants with immature endogenous mechanisms for fat digestion and absorption.

Animals↗
PubMed1981

The bile-salt-stimulated lipase in human milk. Purification and characterization.

The bile-salt-stimulated lipase was purified from human whey by chromatography on heparin-Sepharose and Affi-Gel blue. The purified enzyme gave a single band with a molecular weight of 90 000 on dodecylsulphate/polyacrylamide gels and this band accounted for at least 98% of the protein on the gel. An antiserum to the purified lipase completely inhibited the enzyme activity and gave a single precipitate against human whey and purified lipase. The bile-salt-stimulated lipase was inhibited by diisopropylfluorophosphate, which bound to the purified enzyme in a molar ratio of 0.85 mol/mol. The lipase is a glycoprotein with a high content of acidic amino acid residues and an isoelectric point of around 4. Proline constitutes more than 10% of the total amino acid residues. The purified lipase has a turnover number of around 150 S-1.

Amino Acids↗
PubMed1981

Hydrolysis of human milk fat globules by pancreatic lipase: role of colipase, phospholipase A2, and bile salts.

Human milk fat globules were used to explore how dietary triglycerides are hydrolyzed by pancreatic lipase. These triglycerides were hydrolyzed very slowly by lipase alone as if the surface layer of proteins and phospholipids impeded the action of the enzyme. The inhibition of lipase activity could be overcome by addition either of colipase or of pancreatic phospholipase A2. Colipase enhanced triglyceride hydrolysis in a dose-dependent manner whether bile salts were present or not. Bile salts had no effect on the activity of pancreatic lipase alone but further enhanced the activity at all concentrations of colipase tested. Bile salts were a prerequisite to relieve inhibition of lipase activity by phospholipase A2. Human milk fat globules exposed to phospholipase A2 should be representative of a physiological substrate for pancreatic lipase. A major new observation was that bile salts, even at high concentrations, stimulated triglyceride hydrolysis of such phospholipase-treated globules by pancreatic lipase also in the absence of colipase.

Bile Acids and Salts↗
PubMed1980

Collecting and banking human milk: to heat or not to heat?

Data on human breast milk and its handling when fed to babies who cannot be breast-fed were reviewed to determine whether the method of processing and storage affected the properties of the milk. Breast milk is normally contaminated by potential pathogens, which seem to produce no ill effects, but it also contains antimicrobial properties which protect against infection. The evidence suggests that pasteurisation not only eliminates pathogenic bacteria but also damages bacteriostatic mechanisms, so making the milk more susceptible to later contamination. Pasteurisation also affects the nutritional properties of milk. Freezing has little effect on milk proteins, while a study on the effect of refrigeration showed that there was little bacterial growth at temperatures below 8 degrees C. Several years' experience of feeding donated raw milk to newborn infants has confirmed that it produces no ill effects. These findings suggest that pasteurisation of donated breastmilk is unnecessary, and it is not recommended, while the decision whether or not to freeze the milk may be made on practical grounds. Raw breast milk can be safely stored at 4-6 degrees C for 72 hours.

Bacteria↗
PubMed1979

Colipase enhances hydrolysis of dietary triglycerides in the absence of bile salts.

This study explores how dietary lipids are digested when intraduodenal bile salts are low or absent. Long-chain triglycerides emulsified with phosphatidylcholine were found to be hydrolyzed very slowly by pancreatic lipase alone, as if the surface layer of phospholipids enveloping the triglycerides impeded the action of the enzyme. Colipase enhanced triglyceride hydrolysis severalfold, both when added before or after the lipase. Hydrolysis became even more rapid when the emulsion was first incubated with pancreatic phospholipase. Hydrolysis of long-chain triglycerides was also severely impeded when other proteins were added to the system, probably because they adsorbed to the oil-water interface of the emulsion droplets. It was previously known that bile salts can relieve such inhibition, presumably by desorbing the adsorbed proteins. Colipase was found to enhance hydrolysis severalfold in a dose-dependent manner even in the absence of bile salts, i.e., it could partially or completely relieve the inhibition depending upon the amount and the type of inhibitory protein added to the system. Prior exposure of a protein-coated triglyceride emulsion to another lipase also enhanced the rate at which pancreatic lipase could then hydrolyze the lipids. Most dietary triglycerides are probably presented for intestinal digestion in emulsions covered by proteins and/or phospholipids. These emulsions would be hydrolyzed slowly by pancreatic lipase alone. However, through the action of the lipase in stomach contents and of pancreatic phospholipase and through the lipolysis-promoting effects of collipase, these triglycerices can be rather efficiently hydrolyzed, even in the absence of bile salts.

Animals↗
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↗
PubMed1977

On the source of lipase activity in gastric contents.

--A convenient assay procedure for determination of the activity of pharyngeal lipase (gastric content lipase), using a long chain triglyceride as substrate, is described. Lipase activity in extracts of rat tongue, salivas collected from the upper esophageal pouch from two human newborns with congenital esophageal atresia and in gastric content obtained from an infant with pyloric stenosis were studied. Optimal lipase activities of the three enzyme sources were found in the same pH-range. During hydrolysis the composition of the products formed were also similar. The data presented indicate that at least some of the lipase activity which is responsible for lipolysis in the stomach of the newborn, originates in pregastric tissues.

Animals↗
PubMed1977

Role of feeding on lipase activity in gastric contents.

Lipase activity was recorded in gastric contents collected from healthy term and preterm neonates. In contrast to pancreatic lipase activity this lipase activity was higher at pH 5.5 than at pH 8.0 and it was more resistent to acid inactivation. Lipase activity was found in gastric contents from all infants who were regularly fed, but was not present in gastric contents from some infants when collected before regular feeding was established. During test meals lipase activity in gastric contents increased considerably in all infants studied. During such a test meal there was a progressive relative decrease in triglycerides whilst diglycerides showed a relative increase suggesting an active lipolytic process in the stomach. An assay procedure for determination of lipase activity in gastric contents is also described.

Diglycerides↗