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Biomedical subjects

B Danielsson

Publications and source records attributed to B Danielsson.

At least 73 records · Page 4Linked to original sources
PubMed1982

Calorimetric analysis of sugars and sugar derivatives with aid of an enzyme thermistor.

Enzymic determination of L-ascorbic acid, D-galactose, D-glucose, cellobiose, lactose, and sucrose with an enzyme thermistor is described. The enzyme thermistor is a simple flow-calorimeter designed for routine analysis and measures metabolites by the heat produced in a small column with immobilized enzyme. This instrument may be used for determination of discrete samples as well as for continuous monitoring. As the change of enthalpy produced by the primary reaction is usually large enough to make the measurement sufficiently accurate, simple assay procedures can be designed, an advantage of great importance when the samples are crude and complex.

Ascorbate Oxidase↗
PubMed1981

Enzyme thermistor analysis of penicillin in standard solutions and in fermentation broth.

Immobilized penicillinase was applied in an enzyme thermistor for calorimetric analysis of samples containing penicillin G. Standard solutions as well as extracts from fermentation broth were analyzed. The enzyme was applied bound either to porous glass or, when dealing with crude preparations, to the inner surface of nylon tubing. In the fermentation system studied, high concentrations of penicillin were present, thus allowing dilution to reduce the influence of the composition of the medium on the analysis. The useful linear concentration range was from 0.1 to 100 mM. The coefficient of correlation between analytical results obtained with the present method and those from conventional assays was 0.997.

Journal Article↗
PubMed1979

Use of an enzyme thermistor in continuous measurements and enzyme reactor control.

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We decribe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containing immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.

Calorimetry↗
PubMed1978

Plasma lipoprotein separations by zonal ultracentrifugation.

Procedures for the separation of plasma lipoprotein classes and subclasses by zonal ultracentrifugation are described. The main density classes, very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL), in plasma can be separated in a single run for 20 hours. For the isolation of VLDL-LDL a centrifugation time of only 90 minutes is needed. Separations can be performed on plasma volumes varying from 10 to 400 ml in the Ti-14 rotor used; VLDL can in this way be isolated from 400 ml plasma in 30 minutes. The advantages and disadvantages of zonal ultracentrifugation in comparison with the commonly employed differential ultracentrifugation for separation of lipoproteins are discussed.

Centrifugation, Zonal↗
PubMed1978

Changes in plasma high density lipoproteins in chronic male alcoholics during and after abuse.

Alterations in plasma high density lipoproteins (HDL) were studied in thirty-eight male chronic alcoholics. Twenty-four (63%) of the patients had increased HDL protein (measured immunochemically) and twenty-five (66%) had increased HDL cholesterol (determined after polyanion precipitation of very low density lipoproteins (VLDL) and low density lipoproteins (LDL)). A statistically significant correlation was found between HDL protein and HDL cholesterol (r = 0.39). gamma-Glutamyltransferase (GT) was elevated in eighteen (47%) of the alcoholics. No significant correlations were found between GT and HDL protein or HDL cholesterol. The increase in HDL, as studied by rate zonal ultracentrifugation, was heterogeneous with changes in the HDL2 as well as HDL3 subfractions. It is suggested that determination of HDL total cholesterol, in combination with GT, may represent a valuable and sensitive test for detection of alcoholism.

Adult↗
PubMed1978

Lipoproteins in plasma from patients with low LCAT activity due to biliary obstruction.

A high density lipoprotein (HDL) fraction, designated cholestatic HDL1, has been isolated by zonal ultracentrifugation from patients with long-standing biliary obstruction. This lipoprotein fraction consists exclusively of disc-shaped particles rich in phospholipid and unesterified cholesterol. The fatty acid composition of the minor cholesteryl ester fraction was characterized by a low content of linoleic acid. Apoprotein E was the dominating protein' component, while only small amounts of apolipoprotein A-I were found. Immunochemical studies of cholestatic HDL1 indicate that a considerable proportion of the particles contained apo E as its only protein constituent. All patients had a markedly reduced endogenous cholesterol-esterifying ability. The finding of apparently primary LpE particles in biliary obstruction may be related to this secondary LCAT deficiency.

Apoproteins↗
PubMed1977

Enzyme thermistor determination of glucose in serum using immobilized glucose oxidase.

An enzyme thermistor assay for serum glucose is described. The glucose present in the sample is reacted in a small column containing glucose oxidase immobilized to controlled pore glass (single thermistor device). The heat produced in the primary reaction is measured directly in the column without any need for coupling reactions. The useful linear range is 0.01-0.45 mM glucose, permitting 50-fold dilution of serum samples. Advantages are low enzyme cost, due to the immobilization, insensitivity for the color or any turbidity of the sample, and no requirement for coenzyme or any ancillary reaction. Improved sensitivity and extended linear range (0.01--0.9 mM) can be attained through a secondary reaction using catalase. The application to glucose analysis of a split-flow enzyme thermistor equipped with a reference column to eliminate unspecific heat effects is also described. The enzyme thermistor determinations were also compared with a spectrophotometric continuous flow technique using a small column with immobilized glucose oxidase and 4-aminoantipyrine and phenol as color reagents.

Blood Glucose↗
PubMed1977

Plasma lipoprotein changes in experimental cholestasis in the dog.

Plasma lipoproteins were compared before and after surgical induction of extrahepatic biliary obstruction in dogs by immunochemical techniques, zonal ultracentrifugation and gel filtration. A considerable increase in LDL was found one week after operation, with a zonal ultracentrifugal pattern which was more complex than that found before operation. The lipid composition was characterized by an increase of phospholipids and a decrease of triglycerides in cholestatic LDL fractions. None of the fractions displayed the inverse cholesterol-cholesterol ester ratio, characteristic for human LP-X. The apoprotein composition of cholestatic LDL was also markedly changed. Apoprotein A I, already present in the normal LDL2 subclass, increased and two apoproteins with apparent molecular weight of 35000-40000 appeared in considerable amounts. The amount of HDL was decreased during cholestasis without any appreciable changes in composition.

Animals↗