Biomedical subjects

B Danielsson

Publications and source records attributed to B Danielsson.

At least 19 recordsLinked to original sources

PubMed2000

Pharmacokinetic data support pharmacologically induced embryonic dysrhythmia as explanation to Fetal Hydantoin Syndrome in rats.

New studies suggest that the teratogenicity of phenytoin (PHT) is linked to its membrane-stabilizing pharmacological action via the rapid component of the delayed rectified potassium channel (lkr), resulting in embryonic cardiac dysrhythmia during a restricted sensitive period. In order to further elucidate this theory, PHT was administered to Sprague-Dawley rats on gestation day (GD) 11 with either a single dose of 150 or 100 mg/kg ip or 150 mg/kg po and developmental toxicity at term (GD 21) was studied. In satellite animals blood samples were withdrawn (0.5-24 h after dose) and total and free maternal plasma concentrations of PHT were measured. Pharmacokinetic data correlated well with pregnancy outcome data. At 150 mg/kg ip high concentrations of long duration (C(max) 240 microM and AUC 5300 microMhl(-1) - total) and marked developmental toxicity (embryonic death, decreased fetal weights, and orofacial clefts) were observed. After 100 mg/kg ip (C(max) 150 microM, AUC 2600 microMhl(-1) - total) only slight developmental toxicity (decreased fetal weights) was recorded and after 150 mg/kg po the plasma concentrations were even lower (C(max) 63 microM and AUC 1100 microMhl(-1) - total) and no adverse effects at all were observed. In separate experiments the effect of different concentrations of PHT on the embryonic heart was studied by adding PHT to GD 11 rat embryos cultured in vitro or by culturing GD 11 embryos from exposed dams. The decrease in heart rates was 3, 16, and 32% after culture with 50, 100, and 200 microM of PHT, respectively. After maternal administration of 150 mg/kg ip or po, the embryonic heart rate in vitro decreased by 25 and 7%, respectively, compared to controls. Altogether the results suggest that the development toxicity of PHT is caused by concentration-dependent induction of embryonic dysrhythmia and hypoxia related damage.

Abnormalities, Drug-Induced↗

PubMed1999

High-sensitivity assay for pesticide using a peroxidase as chemiluminescent label.

The application of a newly isolated transgenic tobacco peroxidase (TOP) as a chemiluminescent label for immunoassay purposes is described for the first time. The enzyme has been oxidized with m-periodate and subsequently coupled to the model compound 2,4-dichlorophenoxyacetic acid (2,4-D) using a carbodiimide method. As compared to the native horseradish peroxidase used in control experiments, the TOP enzyme showed significantly higher efficiency of coupling to the antigen and no loss of the specific activity was observed. The obtained 2,4-D-TOP conjugate demonstrated unique properties in chemiluminescent detection. The latter allowed the minimization of the conjugate concentration due to the superior chemiluminescent activity of the enzyme. A highly sensitive capillary chemiluminescent immunoassay using the 2,4-D-TOP conjugate as labeled competitor is reported. Direct competitive ELISA has been performed using a specific monoclonal antibody immobilized onto the sol-gel treated glass capillary surface. A modified photomultiplier tube with a special holder for a capillary was used for the resulting chemiluminescent signal detection. The typical standard calibration curve for the 2,4-D pesticide detection is linear between 30 pg and 500 ng/mL.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1999

Principles of enzyme thermistor systems: applications to biomedical and other measurements.

This chapter presents an overview of thermistor-based calorimetric measurements. Bioanalytical applications are emphasized from both the chemical and biomedical points of view. The introductory section elucidates the principles involved in the thermometric measurements. The following section describes in detail the evolution of the various versions of enzyme-thermistor devices. Special emphasis is laid on the description of modern "mini" and "miniaturized" versions of enzyme thermistors. Hybrid devices are also introduced in this section. In the sections on applications, the clinical/biomedical areas are dealt with separately, followed by other applications. Mention is also made of miscellaneous applications. A special section is devoted to future developments, wherein novel concepts of telemedicine and home diagnostics are highlighted. The role of communication and information technology in telemedicine is also mentioned. In the concluding sections, an attempt is made to incorporate the most recent references on specific topics based on enzyme-thermistor systems.

Biosensing Techniques↗

PubMed1999

An enzyme thermistor-based assay for total and free cholesterol.

A method to evaluate the free (FC) and total cholesterol (TC) in human serum, bile and gallstone extract using an enzyme thermistor (ET)-based flow injection analysis (FIA) is presented. The cholesterol in high-density (HDL-C) and low density lipoprotein (LDL-C) have also been evaluated. A heparin functionalized Sepharose column was employed for the isolation of HDL and LDL fractions from serum. The estimation of cholesterol and its esters was based on their reaction with cholesterol oxidase (CO), cholesterol esterase (CE) and catalase (CAT). Three different enzyme columns, i.e. co-immobilized CO/CAT (column A), only CE (column B) and co-immobilized CO/CE/CAT (column C) were prepared by cross-linking the enzymes on glass beads using glutaraldehyde. Column A was used for estimating FC and column C was used for estimating total cholesterol (cholesterol plus esterified cholesterol). Column B was used as a pre-column which could be switched 'in' or 'out' in conjunction with column A for the estimation of TC or FC, respectively. A calibration between 1.0 and 8.0 mmol/l for FC and 0. 25 and 4.0 mmol/l for TC was obtained. For more than 2000 assays with the ET device a C.V. of less than 4% was obtained. The assay time was approximately 4 min per assay. The cholesterol estimations on the ET correlated well with similar estimations using a commercially available cholesterol diagnostic kit.

Biosensing Techniques↗

PubMed1999

The development and applications of thermal biosensors for bioprocess monitoring.

Enzyme thermistors are biosensors that use thermal resistors to measure the heat change caused by an enzymatic reaction. They combine the selectivity of enzymes with the sensitivity of biosensors and allow continuous analysis in a flow-injection mode. They can be used to monitor fermentation systems, biocatalysis, enzyme-catalysed synthesis and clinical and food technology. This article gives an overview of the general principles of enzyme thermistors, the sampling process and the ongoing developments in the field of bioprocess monitoring.

Automation↗

PubMed1998

[Did glucan in indoor environment cause respiratory tract inflammation?].

Three children living in a house affected by mould manifested severe airways and general symptoms indicative of non-specific airways inflammation. Measurement of airborne (1-->3)-beta-D-glucan, a cell wall constituent in moulds, yielded values ranging from 22 to 115 ng/m3, as compared to normal values of some few ng/m3. On moving to relatives, all three children improved and could terminate medication after 2-3 weeks. The findings are consistent with previous reports of symptoms induced by exposure to mould, and suggest that quantification of viable organisms may not adequately reflect the exposure risk.

Adult↗

PubMed1998

Human hormone-sensitive lipase: expression and large-scale purification from a baculovirus/insect cell system.

Hormone-sensitive lipase (HSL) is a key enzyme in lipid metabolism and overall energy homeostasis in mammals. It catalyzes the rate-limiting step in the hydrolysis of triglyceride stores in the adipocytes, delivering free fatty acids for their use as energy substrates. HSL activity is under acute hormonal and neural control, mediated through reversible phosphorylation of the enzyme. Emerging data from clinical studies indicate that HSL deficiency or malfunction is associated with several pathological situations in humans. In order to perform a biochemical characterization of human HSL, and to elucidate its molecular properties, purification of homogeneous protein in large amounts is required. Here, we describe the expression and purification of a catalytically active recombinant human HSL. The process allows the purification of milligram amounts of homogeneous protein, and should provide a valuable tool for a thorough molecular characterization of the enzyme.

Amino Acid Sequence↗

PubMed1998

Hyperlipidaemia: differences in management practices and attitudes in two regions in Europe--Sicily and the Stockholm area.

In order to compare attitudes and management concerning hyperlipidaemia and risk factors for coronary heart disease among doctors in northern and in southern Europe, a questionnaire study was undertaken among doctors in primary health care and departments of internal medicine in Sicily and Stockholm. The regions differed in culture and health-care structure. Guidelines were similar, but screening of healthy individuals was recommended in Sicily, and not in Sweden. One hundred and fifty-three general practitioners in Sicily and 120 in Stockholm, 211 internists in Sicily and 83 in Stockholm participated. Main outcome measures were management policies for investigation and treatment and also attitudes. Routine lipid checks at first visits were done by few doctors in Stockholm but by a majority in Sicily (p < 0.001); in the presence of general cardiovascular risk factors (other than heredity, diabetes, cardiovascular disease and hypertension), routine checks were carried out more often by both general practitioners (p < 0.001) and internists (p < 0.005) in Stockholm. Drug treatment was initiated at lower cholesterol levels for secondary and primary intervention, cardiovascular disease, cardiovascular risk factors and hereditary hyperlipidaemia by both groups in Sicily (p < 0.001), as was dietary treatment. Secondary prevention was considered important by all groups, but primary prevention only by Sicilian doctors. We concluded that there were differences in views and management practice between doctors in Sicily and in Stockholm on the investigation and treatment of patients with hyperlipidaemia. Doctors tested lipids at first visits in Sicily but not in Stockholm. Treatment was initiated at lower levels of cholesterol in Sicily.

Drug Utilization↗

PubMed1998

Postmortem changes in blood concentrations of phenytoin and carbamazepine: an experimental study.

Observations of low postmortem blood concentrations of antiepileptic drugs in cases of sudden unexpected death in epilepsy (SUDEP) have led to the assumption that noncompliance may play a role in SUDEP. However, the reliability of postmortem drug levels has been questioned. The purpose of this study was to analyze possible postmortem changes in blood concentrations of carbamazepine (CBZ) and phenytoin (PHT). New Zealand white rabbits were fed with PHT or CBZ until assumed steady state. A blood sample was then drawn for determination of serum and whole blood concentrations of CBZ and PHT, after which the rabbits were killed and stored at 6 degrees C. A further blood sample for drug analysis was obtained 72 hours after death. Antemortem serum concentrations of CBZ were not significantly different from whole blood concentration 72 hours after death. In contrast, antemortem whole blood concentrations of PHT were only 65% of the corresponding serum concentrations, and postmortem PHT blood levels were even lower, being 35% of antemortem serum concentrations. In conclusion, blood concentrations of CBZ seem to be stable during 72 hours after death under these experimental conditions. However, postmortem PHT concentrations should be interpreted with caution and low postmortem concentrations do not necessarily imply a poor compliance.

Animals↗

PubMed1997

Evaluation of a miniaturized thermal biosensor for the determination of glucose in whole blood.

A miniaturized thermal biosensor has been evaluated as part of a flow-injection analysis system for the determination of glucose in whole blood. Glucose was determined by measuring the heat evolved when samples containing glucose passed through a small column with immobilized glucose oxidase and catalase. Samples of whole blood (1 microliter) can be measured directly, without any pretreatment. The correlation in the response between the thermal biosensor, the Reflolux S meter (Boehringer Mannheim), the Granutest 100 glucose test kit (Merck Diagnostica) and the Ektachem (Kodak) instrument was evaluated. The influence of the hematocrit value and of possible interferences is reported. The correlation measurements show that the thermal biosensor calibrated with aqueous glucose standards generally gives lower values on blood glucose than the reference methods calibrated for serum or blood measurements. Mean negative biases range from 0.53 to 1.16 mmol/l. Differences in sample treatment clearly complicate comparisons and the proper choice of reference method. There was no influence from substances such as ascorbic acid (0.11 mmol/l), uric acid (0.48 mmol/l), urea (4.3 mmol/l) and acetaminophen (0.17 mmol/l) on the response to 5 mmol/l glucose. The hematocrit value does not influence the glucose determination, for hematocrit values of between 13 and 53%.

Biosensing Techniques↗

PubMed1997

Thermistor-based biosensing.

In this review a universal thermistor-based biosensor system is described with examples from clinical chemistry, bioprocess monitoring and environmental control. The technique is based on the measurement of the small temperature changes associated with enzymatic reactions occurring in a microreactor with immobilized enzyme. The system has good operational stability and a sensitivity that permits measurements down to 1 microM concentrations. Current developments include devices constructed by micromachining for multisensing purposes and miniaturised instrumentation intended for use in portable monitoring. With use of special supports for enzyme immobilisation even untreated whole blood samples can be applied. Another current line of investigation involves hybrid biosensors, such as combinations of electrochemistry and calorimetry into bioelectrocalorimetric devices with interesting new properties.

Alcohols↗

PubMed1996

Domain-structure analysis of recombinant rat hormone-sensitive lipase.

Hormone-sensitive lipase (HSL) plays a key role in lipid metabolism and overall energy homoeostasis, by controlling the release of fatty acids from stored triglycerides in adipose tissue. Lipases and esterases form a protein superfamily with a common structural fold, called the alpha/beta-hydrolase fold, and a catalytic triad of serine, aspartic or glutamic acid and histidine. Previous alignments between HSL and lipase 2 of Moraxella TA144 have been extended to cover a much larger part of the HSL sequence. From these extended alignments, possible sites for the catalytic triad and alpha/beta-hydrolase fold are suggested. Furthermore, it is proposed that HSL contains a structural domain with catalytic capacity and a regulatory module attached, as well as a structural N-terminal domain unique to this enzyme. In order to test the proposed domain structure, rat HSL was overexpressed and purified to homogeneity using a baculovirus/insect-cell expression system. The purification, resulting in > 99% purity, involved detergent solubilization followed by anion-exchange chromatography and hydrophobic-interaction chromatography. The purified recombinant enzyme was identical to rat adipose-tissue HSL with regard to specific activity, substrate specificity and ability to serve as a substrate for cAMP-dependent protein kinase. The recombinant HSL was subjected to denaturation by guanidine hydrochloride and limited proteolysis. These treatments resulted in more extensive loss of activity against phospholipid-stabilized lipid substrates than against water-soluble substrates, suggesting that the hydrolytic activity can be separated from recognition of lipid substrates. These data support the concept that HSL has at least two major domains.

Amino Acid Sequence↗

PubMed1996

Use of an enzyme thermistor for semi-continuous blood glucose measurements.

A method to monitor glucose in whole blood is presented. The aim of the project was to develop a prototype for a bedside monitor system for semi-continuous monitoring of the blood glucose concentration, requiring only one calibration. This was made possible by using the special advantage of the thermal sensor technique in combination with the adjustment of flow. The glucose concentration was determined from the difference between the sensor response and an estimated background signal. Using standard addition technique, calibration factors for background and sensitivity were set and remained unchanged during the monitoring. The background signal was 45 +/- 8 mV (mean +/- S.D., n = 8) and the sensitivity was 28 +/- 1 mV/mmol (mean +/- S.D., n = 4). Recovery in whole blood was 90-98% (mean 94%, n = 12). With an injection interval of 3 min the precision with the sensor was < 3% over more than 100 blood samples. Response time was about 60 s. The calculated glucose values correlated, r = 0.98, with the values obtained with an YSI glucose analyser (Yellow Springs Instruments. Yellow Springs, OH, USA), over the range 2-20 mmol/l.

Biocompatible Materials↗

PubMed1995

On-line monitoring of ethanol, acetaldehyde and glycerol during industrial fermentations with Saccharomyces cerevisiae.

Industrial fermentations carried out in a 500-l bioreactor were monitored on-line by a prototype of a split-flow modified thermal biosensor. Acetaldehyde and glycerol in the extracellular broth were monitored over the first 48 h of fed-batch fermentations. The aim was to determine the usefulness of these secondary metabolites for on-line monitoring and control. When fermentation of the 13-16 g/l batch sugar was monitored, using immobilised aldehyde dehydrogenase, the acetaldehyde reached a peak value of 0.3 g/l. With immobilised alcohol oxidase a much larger peak of 3.5 g/l ethanol was seen immediately after the acetaldehyde peak. When glycerokinase was used a delayed peak of 1 g/l glycerol was monitored. Of the three metabolites monitored, the ethanol proved the most valuable indicator of suitable timing for the start of the feeding phase and later for controlling and preventing overfeed using the on-line biosensor system.

Acetaldehyde↗

PubMed1995

The public view on cardiovascular risk factors and changes in lifestyle.

OBJECTIVE: To investigate the public knowledge of cardiovascular risk factors including hyperlipidaemia, and attitudes to changes in lifestyle and to the role of the primary health care in preventive work. DESIGN: Postal questionnaire. SETTING: A physically defined area in south-western Stockholm. SUBJECTS: 1000 randomly selected individuals of both sexes 40 to 64 years, stratified into 5-year groups. MAIN OUTCOME MEASURES: Knowledge of and attitudes to cardiovascular risk factors. Contact with the primary health care and expectancy of physicians' interest in patients' lifestyles. RESULTS: Response rate was 75%. The awareness of cardiovascular risk factors was high, but only 51% knew what constitutes healthy food, and two thirds doubted that they could change their eating habits. Forty-eight percent had visited the primary health care during the previous year. Eighty-four percent thought that the physicians should know about their patients' smoking, 83% about drinking habits, and 75% about eating habits. Physicians were expected to spend 40% of their time on preventive work. Only 26% believed that press information about hyperlipidaemia and heart disease did more good than harm. CONCLUSION: Knowledge was good about causative cardiovascular risk factors, but poor about healthy eating. Physicians were expected to have an interest in patients' lifestyle and in prevention. This type of knowledge is important for preventive work.

Adult↗

PubMed1994

Induction of rhythm abnormalities in the fetal rat heart. A tentative mechanism for the embryotoxic effect of the class III antiarrhythmic agent almokalant.

OBJECTIVES: The aim was to test the hypothesis that the recently reported embryotoxic effect of class III antiarrhythmic agents may be a result of electrophysiological disturbances induced by these agents. METHODS: Comparative studies of drug effects in the adult and fetal rat were performed using three experimental models: (1) effects of almokalant upon pregnancy and fetal mortality in rats given daily doses of 0, 10, 50, 100, or 400 mumol.kg-1 orally in the diet on days 6-15 of pregnancy; (2) effects of d-sotalol (1-1000 microM), almokalant (0.1-100 microM) and dofetilide (0.01-10 microM) on the adult and fetal cardiac action potential in vitro; (3) voltage clamp recordings in single fetal and adult ventricular myocytes superfused with almokalant (0.5 microM). RESULTS: In the groups of rats treated with 100 and 400 mumol.kg-1, respectively, the body weight gain was decreased from day 12 of gestation, and there were no viable fetuses at termination of pregnancy. In atrial as well as ventricular tissue, the class III agents induced a concentration dependent prolongation of the fetal action potential duration, accompanied by a reduction in heart rate and eventually the appearance of rhythm abnormalities and/or early afterdepolarisations. The adult action potential duration remained unaffected. An almokalant sensitive current (probably the delayed rectifier, IK) could be evoked both in the fetal and in the adult ventricular cells. CONCLUSIONS: Class III antiarrhythmic agents were shown to induce fetal mortality and rhythm abnormalities in the rat heart. Although they do not prove a causal relationship between these effects, our observations may have implications for the clinical use of class III antiarrhythmic agents in women of childbearing potential.

Action Potentials↗

PubMed1994

Urea and lactate determined in 1-microL whole-blood samples with a miniaturized thermal biosensor.

A miniaturized flow-injected thermal biosensor was developed for the determination of urea and L-lactate in undiluted blood in 1-microL samples. The sensor employed a small enzyme column constructed of stainless steel tubing and microbead thermistors. Urease and lactate oxidase/catalase were separately immobilized onto controlled-pore glass beads, which, in turn, were charged into the enzyme column. With a flow rate of 70 microL/min, linear analytical ranges from 0.2 to at least 50 mmol/L and 0.2 to 14 mmol/L were obtained for urea and lactate, respectively. The relative standard deviations (CVs) for measurements of analyte in buffer were 0.91% for urea and 1.84% for lactate. For urea in whole blood, the CV for 50 determinations was 4.1%. Contrived samples containing various concentrations of urea and L-lactate in whole blood were determined with this sensor and with a spectrophotometric method. Comparisons of the results gave correlation coefficients of 0.989 and 0.984 for 30 blood urea and 30 blood lactate assays in concentrations ranging from 4 to 20.9 mmol/L and from 1.7 to 12.7 mmol/L, respectively.

Biosensing Techniques↗

PubMed1994

24-hour ambulatory blood pressure monitoring in elderly normotensive individuals and its reproducibility after one year.

To study ambulatory blood pressure (ABP) and its reproducibility in healthy normotensive elderly subjects, 34 individuals were randomly selected. Their ages were 65 years (n = 10), 70 years (n = 10), 75 years (n = 8) and 80 years (n = 6). SpaceLabs 90207 system was used and one initial and a follow-up measurement after one year was performed. It was found that 24h ABP easily could be recorded in elderly subjects. A mean of 97% of the measurements were successful and only two of 34 subjects dropped out because of measurement failures. Nocturnal blood pressures were lower in all age groups and in both sexes. The standard deviations of the differences between the baseline and one year measurements were for the daytime period 8/4 mmHg and for the nighttime period 12/8 mmHg. In conclusion, ABP is easily accepted as a clinical method in normotensive elderly subjects. In all subjects there is a reduction of the nocturnal blood pressure and the reproducibility of ABP after one year is good.

Aged↗