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Biomedical subjects

G Johansson

Publications and source records attributed to G Johansson.

At least 91 records · Page 5Linked to original sources
PubMed1998

An immunological interleukine-6 capacitive biosensor using perturbation with a potentiostatic step.

An instrument for potentiostatic capacitance measurements, based on perturbation with a potentiostatic step was used. The capacitive sensor consisted of self-assembled sulfur compounds on gold to which antibodies towards Interleukine 6, Il-6, had been immobilized. The biosensor was part of a potentiostatic three-electrode system with an extra reference electrode. Two different methods using epoxy- or carbodiimide coupling of the polyclonal antibodies were compared. The antigen Il-6 could be detected from 5 x 10(-16) to 5 x 10(-13) M with one immobilization method and to more than 5 x 10(-9) M with the other. No labels were necessary since the binding of the antigen was detected directly. The insulating properties of the different layers of the biosensor were investigated.

Biosensing Techniques↗
PubMed1998

Detection of heavy metal ions at femtomolar levels using protein-based biosensors.

Sensors based on proteins (GST-SmtA and MerR) with distinct binding sites for heavy metal ions were developed and characterized. A capacitive signal transducer was used to measure the conformational change following binding. The proteins were overexpressed in Escherichia coli, purified, and immobilized in different ways to a self-assembled thiol layer on a gold electrode placed as the working electrode in a potentiostatic arrangement in a flow analysis system. The selectivity and the sensitivity of the two protein-based biosensors were measured and compared for copper, cadmium, mercury, and zinc ions. The GST-SmtA electrodes displayed a broader selectivity (sensing all four heavy metal ions) compared with the MerR-based ones, which showed an accentuated selectivity for mercury ions. Metal ions could be detected with both electrode types down to femtomolar concentration. The upper measuring limits, presumably due to near saturation of the proteins' binding sites, were around 10(-10) M. Control electrodes similarly constructed but based on bovine serum albumin or urease did not yield any signals. The electrodes could be regenerated with EDTA and used for more than 2 weeks with about 40% reduction in sensitivity.

Amino Acid Sequence↗
PubMed1998

Concentration and purification of beta-glucosidase from Aspergillus niger by using aqueous two-phase partitioning.

The extracellular enzyme beta-glucosidase, present in a culture filtrate and produced by Aspergillus niger, was concentrated up to 700 times by two-phase partitioning. The two-phase systems were achieved by dissolving dextran and poly(ethylene glycol) in the culture filtrate in such proportions that the lower phase, containing the enzyme, consisted of a very small volume compared with the upper phase. The enzyme had high affinity for the lower phase when the system contained 100 mM KSCN at pH 8.0, and the recoveries of beta-glucosidase were in the range of 85 95% with a concentrating factor of 60-720 times. At the same time, the enzyme was purified 2-3 times.

Aspergillus niger↗
PubMed1998

Fractionation of wheat gliadins by counter-current distribution using an organic two-phase system.

A liquid liquid two-phase system based on N,N-dimethylformamide and the two polymers, poly(ethyleneglycol) and Ficoll, useful for partitioning of hydrophobic proteins, has been developed. The system has been applied to a counter-current distribution process in 56 steps for analysing the heterogeneity of proteins extracted with N,N-dimethylformamide from wheat flour. The counter-current distribution patterns of proteins, extracted from eight kinds of wheat, have been analysed. The minimum number of hypothetical proteins necessary to describe the patterns was found to be seven. The relative amount of these hypothetical components varied among the wheats.

Chemical Fractionation↗
PubMed1998

Salt-steered partitioning of proteins in polymeric two-phase systems based on N,N-dimethylformamide.

The polymeric two-phase (liquid liquid) system, based on N,N-dimethylformamide (DMFA) and the two polymers Ficoll and poly(ethylene glycol). has been investigated. The partitioning of the water-insoluble protein fraction, zein (from corn), was affected by the addition of various salts that were soluble in DMFA. The effect of the salts has been correlated to their partition coefficients. The data have been fitted to a theory for partitioning of polyelectrolytes in aqueous two-phase systems. The two-phase system has been used for partial fractionation of zein by counter-current distribution.

Chemistry Techniques, Analytical↗
PubMed1998

The initial kinetics of hydrolysis by cellobiohydrolases I and II is consistent with a cellulose surface-erosion model.

Introduction of a novel method for the quantification of the cellobiose released made it possible to follow the initial stage of hydrolysis of bacterial microcrystalline cellulose (BMCC) by cellobiohydrolases 1,4-beta-D-glucan-cellobiohydrolase I (CBH I) and 1,4-beta-D-glucan-cellobiohydrolase II (CBH II) from Trichoderma reesei. A drastic retardation of the rate of the hydrolysis was observed already at a very low degree of conversion. Earlier-suggested retardation factors, such as product inhibition by cellobiose or enzyme inactivation, could be discounted as primary causes for the pattern. A model including steric hindrance by non-productive binding and erosion of the cellulose surface during the processive action of exoenzymes was proposed to describe the rate retardation observed. Simultaneous action of CBH I and CBH II on cellulose was not a prerequisite for synergy between them.

Binding, Competitive↗
PubMed1998

Substrate specificity of cellobiose dehydrogenase from Phanerochaete chrysosporium.

Substrate structural mapping suggests that the catalytic site of cellobiose dehydrogenase from Phanerochaete chrysosporium forms a narrow cave with two hexose binding subsites. Kinetic data also show that beta-di or oligosaccharides are favored electron donors with respect to both KM and kcat. Surprisingly, thiocellobiose showed an even higher kcat than cellobiose, although the KM value was somewhat higher. The CDH was purified using an updated protocol.

Basidiomycota↗
PubMed1998

Stereoisomers of 3-(2,3-dihydrobenzofuran-2-yl)quinuclidine: preparation and muscarinic receptor affinities.

The four stereoisomers of the antimuscarinic 3-(2,3-dihydrobenzofuran-2-yl)quinuclidine have been prepared by a method involving chromatographic separation of the racemic diastereoisomers as borane complexes. The relative and absolute configurations of the stereoisomers were determined by X-ray crystallographic methods. The crystal structure of (2'R,3R)-3-(2,3-dihydrobenzofuran-2-yl)quinuclidine.HCl.H2O contains two independent molecules with different conformations of both the quinuclidine moiety and the dihydrofuran ring.

Animals↗
PubMed1998

Evaluation of a workplace redesign of a grocery checkout system.

The aim of this study was to evaluate the effects on the working postures and movements of a cashier when two different locations of the scales (one to the left of the cashier, the other under the conveyer belt in front of the cashier) were used in a grocery checkout system. Two cashiers (of average stature and short stature) were videotaped while working, in both sitting and standing working positions. Analysis of the video tapes was performed using the WOPALAS method and video observations. The results of the study show that the design of the checkout system with the scales under the conveyer belt provides a more favourable working position for both the taller and the shorter cashier. Additionally, the results indicate that a standing position is more favourable than a sitting one for the taller cashier while for the shorter cashier the sitting position is better.

Ergonomics↗
PubMed1998

The human side of the road: improving the working conditions of urban bus drivers.

This study evaluated how urban bus drivers' well-being was affected by technical interventions designed to improve the traffic environment of an urban bus route. Three questionnaires were distributed; 8 drivers at the intervention route (mean age 43 years) and 13 demographically matched comparison drivers (mean age 39 years) participated at all occasions. Field studies at work were conducted twice, with 10 intervention route drivers (mean age 43 years) and 31 comparison drivers (mean age 42 years). The authors hypothesized that during the course of the intervention, the initially elevated indexes of occupational stress in the intervention group would be reduced to levels equivalent to those of the comparison group. The hypothesis was confirmed for perceived workload in the questionnaire, observer-rated job hassles, systolic blood pressure and heart rate at work, and perceived distress after work in the field study.

Adult↗
PubMed1998

Supported liquid membrane coupled on-line to potentiometric stripping analysis at a mercury-coated reticulated vitreous carbon electrode for trace metal determinations in urine.

A method for trace metal determinations in complex matrices is presented. The method combines supported liquid membrane (SLM) sample clean-up and enrichment with potentiometric stripping analysis (PSA) in a flow system using reticulated vitreous carbon (RVC) as the electrode material. The membrane contained 40% m/m di-2-ethylhexylphosphoric acid dissolved in kerosene. Lead was used as a model substance in high-purity water and urine samples. The samples were enriched after a simple pH adjustment. The SLM enrichment time was 10 min when the last 5 min electrodeposition on the RVC electrode at -1.0 V (versus Ag/AgCl) was performed simultaneously. The influence of various experimental parameters such as deposition time, deposition potential and flow rate on the lead signal was investigated. With a 10 min SLM enrichment including a 5 min deposition time, the detection limit for lead was 0.3 microgram l-1. The relative standard deviation for lead concentrations in the range 4-20 micrograms l-1 was 0.05%. The overall SLM-PSA system was found to be stable for at least 100 urine analyses. The method was validated by running a reference urine sample. The result obtained (five replicates) was 9.7 micrograms l-1 (standard deviation 1.8 micrograms l-1) which is within the recommended range of 9.2-10.8 micrograms l-1.

Electrodes↗
PubMed1998

Validation with biological markers for food intake of a dietary assessment method used by Swedish women with three different dietary preferences.

OBJECTIVES: To validate a dietary assessment method, a 4-day food record together with a duplicate portion technique, with biological markers for food intake. DESIGN: Four days of duplicate portions were collected in parallel with food recording. A 24-h urine sample and the faeces corresponding to the food intake (using a coloured marker) were collected. Completeness of urine and faeces collections was assessed using para-aminobenzoic acid (PABA) in urine and cadmium in faeces, respectively. Biomarkers of food intake (energy, protein, fibre, sodium, potassium, calcium) were measured in urine and faeces. SETTING: Swedish west coast. SUBJECTS: Non-smoking Swedish women, 20-50 years of age, consuming a mixed diet (n = 34), a mixed diet rich in shellfish (n = 17) or a vegetarian/high-fibre diet (n = 23). RESULTS: The average ratio (food intake according to the dietary assessment methods/ biological marker) for protein, sodium, potassium and calcium was 0.86. This indicates an underestimation of the food intake by approximately 15%. The ratio of stated fibre intake to biological marker was 1.20 for the mixed diet and the vegetarian diet group, indicating an overestimation by approximately 20%. CONCLUSIONS: The underestimation of the intake of protein, sodium, potassium and calcium by all three groups and the overestimation of the fibre intake by two groups indicate that underreporting is selective to certain nutrients and foods and to various groups of people. The two dependent dietary assessment methods were equally good in measuring protein intake, which indicates that the women recorded what they actually duplicated.

4-Aminobenzoic Acid↗
PubMed1998

Aspects of teeth from archaelogic sites in Sweden and Denmark.

The purpose of this study was to examine ground sections of primary second molars and permanent first molars from the same jaws. Teeth from 11 individuals were collected from archaeologic sites in Sweden and Denmark. Longitudinal buccolingual sections were examined in a polarization light microscope and in a Philips scanning electron microscope (SEM). The seven teeth from Sweden appeared to have been subjected to environmental influences at their burial site, which had affected both the dentin and the enamel. The teeth from the Danish sites had a normal color, and no disintegration of the dentin was seen. The general morphologic appearance was normal in all primary and permanent teeth. The position of the neonatal line indicated a normal full-term gestational age. The observed accentuated incremental lines in both the primary and permanent enamel suggested periods of dietary changes, possibly related to periods of illness. SEM images of the surface area of the Swedish teeth showed an extremely porous enamel surface with severe changes in the prism structure as an effect of acid penetration. The Danish teeth did not show any marked changes in the enamel.

Acids↗
PubMed1998

Long-term effects of a change from a mixed diet to a lacto-vegetarian diet on human urinary and faecal mutagenic activity.

This is an investigation of the long-term effects of a shift from a mixed diet to a lacto-vegetarian diet and of a return to a mixed diet on the mutagenic activity in urine and faeces. The participants were 20 normal weight, non-smoking subjects. Dietary surveys and urinary and faecal samples were collected before and 3, 6 and 12 months after the dietary shift as well as 3 years after termination of the lacto-vegetarian diet period. The faecal samples were assayed for direct acting mutagens with the fluctuation test for weak mutagens and the urinary samples were assayed with the same assay but with a metabolic activation system, the so-called S9 fraction. The dietary data showed an increase in consumption of fruits, vegetables and dairy products and a decrease in meat, fish, eggs, sweets and biscuits during the vegetarian diet period. These changes led to an increase in total carbohydrates, fibre, vitamin C and calcium and a decrease in fat and protein intake. Mutagenic activity in both urine and faeces decreased after shift to the vegetarian diet and mutagenic activity in faeces increased when the volunteers returned to a mixed diet (P = 0.025 and 0.035 respectively when comparing the diets). These data indicate that dietary factors may effect mutagenic activity in urine and faeces. However, it is still not clear whether a decrease in animal products, a change in other nutritional factors or a decrease in frying are the main contributors to this change.

Adult↗
PubMed1998

The effects of desflurane on cardiac function as measured by conductance volumetry in swine.

UNLABELLED: The purpose of the investigation was to assess the effects of desflurane (DES) on left ventricular heart function during basal barbiturate anesthesia in a closed-pericardium, closed-chest acute swine model. The study was performed in 11 normoventilated adult pigs. Hemodynamic measurements were obtained using arterial, central venous, and pulmonary artery catheters, as well as a conductance volumetry and tip manometry catheter placed in the left ventricle. Hemodynamic measurements were recorded during basal pentobarbital anesthesia and with the addition of 1%, 2%, 4%, and 6% DES. DES dose-dependently decreased mean arterial pressure, systemic vascular resistance, left ventricular end-systolic pressure, dP/dtMAX and dP/dtMIN. At doses >1%, decreases in CO, stroke volume, ejection fraction, end-systolic elastance, preload recruitable stroke work, preload adjusted maximal power, and peak filling rate were observed. Heart rate decreased at 4% and 6% DES. Isovolumetric relaxation time increased only at 6% DES. We conclude that smaller doses of DES have a significant cardiodepressive effect in the setting of barbiturate infusion, as measured by conductance volumetry. IMPLICATIONS: Desflurane, in very small doses, depressed cardiac function during pentobarbital anesthesia with ketamine and benzodiazepine premedication in swine, as assessed by conductance volumetry and left ventricular pressure and volume relationship analysis. These results suggest that desflurane, in combination with certain anesthetics, can be cardiodepressive even in very small doses.

Anesthetics, Inhalation↗
PubMed1998

Job hassles and cardiovascular reaction patterns among urban bus drivers.

Forty-six bus drivers took pan in a longitudinal field study of cardiovascular reactions to urban driving. "Job hassles" were recorded by observers using a standardized list of stress-related events in traffic and on the bus. Measures of blood pressure, heart rate, and ratings of perceived mental strain were obtained after each route segment. Intraindividual correlations between psychophysiological recordings and job hassles were calculated and submitted to cluster analysis. Two reaction patterns were identified, 1 characterized by consistently, although modestly, positive associations between the frequency of job hassles and psychophysiological reactions, the other characterized by a low association between the frequency of hassles and indicators or psychophysiological arousal. The former group displayed significantly higher blood pressure and mental strain ratings in the unwinding phase after work than did the latter group of workers. The results are discussed in terms of rate or "unwinding" after exposure to stressful conditions.

Journal Article↗
PubMed1998

Visual bridging of empty gaps in the optic flow.

This is a study of perception of bending motion and jointed rigid motions over large invisible segments of a bending line. In this project, we investigated the visual perception of changing form of lines, built up by a series of dots and presented under highly reduced pictorial conditions. The changing form was indicated by one or two moving and continuously changing visible fragments of the line. The most extreme condition studied was the perception of the bending of an initially vertical 24-dot line, visually represented only by the stationary base dot and the two moving dots at its top. In this experiment, nearly all subjects reported experiencing a smooth bending connection over the 21-dot empty gap. Three experiments are described and analyzed. The results suggest that the human visual system is astonishingly well adapted for derivation of relevant figural information from such severely reduced, continuously changing optical presentation. An explanation in terms of automatic sensory mechanisms related to the physiological receptive field effect is proposed.

Humans↗