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Biomedical subjects

M Magnusson

Publications and source records attributed to M Magnusson.

At least 19 recordsLinked to original sources
PubMed1992

A comparative serological study of antigenic glycolipids from Mycobacterium tuberculosis.

Two fractions of antigenic diacyl trehaloses (DAT1 and DAT2) were isolated from the type strain of Mycobacterium tuberculosis (H37Rv). Phenolic glycolipid (PGL) and polar glycolipid antigens (C1-C4) were isolated from an unusual smooth so-called 'Canetti' strain of M. tuberculosis. These lipids were analyzed by enzyme-linked immunosorbent assay (ELISA) using antisera against a range of mycobacteria and sera from 50 tuberculosis patients and 25 healthy blood donors. All the lipids gave strong reactions with homologous mycobacterial antisera, except the least polar 'Canetti' polar glycolipid (C4). The phenolic glycolipid (PGL) from the 'Canetti' strain gave only a very weak response with antisera against M. tuberculosis H37Rv. The diacyl trehaloses (DAT) from H37Rv gave only weak reactions with the antisera against the 2 Canetti strains of M. tuberculosis. The 3 most polar glycolipid antigens (C1-C3) from the Canetti strain gave strong responses with serum against M. tuberculosis H37Rv. None of the lipids was able to discriminate between patient and control sera at a level suitable for a serodiagnostic test. A combination of results from several lipids appears to be of greater value in this respect. Thus, PGL, DAT2 and C2 were the best combination, reacting with all but 4 of the patient sera and with only 1 of the control sera.

Animals↗
PubMed1992

Measurement of height loss during whole body vibrations.

An experimental, in vivo study was performed to measure height changes in subjects exposed to whole body vibrations while seated. Twelve women, with an average age of 22 years, were exposed to sinusoidal vibrations for 5 mins. The vibration frequency was 5 Hz, and the acceleration was 0.1 g Rms. The height loss stemming from vibration exposure was compared with that experienced while sitting without being subjected to vibrations. The height losses that always occurred from the two exposures were corrected for the effect of posture change. The height loss from vibration was significantly greater than when no vibration was present. Height loss due to posture change was responsible for approximately 50% of the total height loss. From this study it was concluded that whole body vibrations cause increased height loss.

Adult↗
PubMed1992

Monoclonal antibodies specific for elongation factor Tu and complete nucleotide sequence of the tuf gene in Mycobacterium tuberculosis.

Monoclonal antibodies against mycobacterial antigens were produced by immunizing LOU/C rats with live Mycobacterium bovis BCG. The antibodies were characterized by an enzyme-linked immunosorbent assay and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Western blotting (immunoblotting). One antibody, MAMB 2, reactive with a 47-kDa protein was used to screen a lambda gt11 M. tuberculosis gene library (R. A. Young, B. R. Bloom, C. M. Grosskinsky, J. Ivanji, D. Thomas, and R. W. Davis, Proc. Natl. Acad. Sci. USA 82:2583-2587, 1985). Three recombinant phages reactive with MAMB 2 in plaque lysates were isolated, and part of the insert was sequenced. The mycobacterial inserts were all expressed as proteins fused with beta-galactosidase when the phages were induced as lysogens in Escherichia coli. The entire M. tuberculosis tuf gene was obtained by screening the lambda gt11 library with a DNA probe specific for the primary clones. A phage isolated from this screening was able to express the native protein in E. coli when introduced as a lysogen. A comparison of the entire gene sequence and the deduced protein sequence with the EMBL DNA and Swiss-Prot protein data libraries revealed strong homologies with elongation factors of bacteria, yeast mitochondria, and a plant chloroplast.

Amino Acid Sequence↗
PubMed1992

Reduced intestinal permeability measured by differently sized polyethylene glycols in acute uremic rats.

The effect of experimental acute renal failure on the intestinal permeability measured by differently sized polyethylene glycols (PEG) was studied in rats. The permeability was assessed by analysing the 24-hour urinary recovery of PEG molecules (size 326-1,162 D). Acute renal failure was induced by clamping the left renal artery and right-sided nephrectomy. The overall urinary recovery of PEG was decreased in the uremic rats. However, the relative recovery of larger molecules (range 590-1,162 D) was further reduced in the uremic rats. The results which are compared with a computer simulation by a multicompartment model, suggest that the intestinal permeability especially towards larger PEG is decreased in acute uremic rats.

Acute Kidney Injury↗
PubMed1992

Effect of intravenous diazepam and thiopental on voluntary saccades and pursuit eye movements.

The effects of diazepam and thiopental on voluntary saccades and pursuit eye movements were tested in 9 volunteers, with an interval of at least 2 weeks between tests. One, 4 and 8 h after intravenous injection of diazepam (0.3 mg/kg) or thiopental (6.0 mg/kg), voluntary saccades and pursuit eye movements were tested and blood samples taken for analysis of drug concentration. As compared to results of tests without drugs, a significant reduction both of saccadic peak velocity and gain of pursuit eye movements was found 1 h after injection of either drug, but not after 4 and 8 h. The amplitude of saccades elicited with the 60 degrees stimulus was significantly reduced 1 h after injection of diazepam. Latency of saccades increased significantly up to 4 h after injection of either drug. No significant correlation was found between peak velocity of saccades and blood concentration of either thiopental or diazepam 1 h after administration. The present results confirm that in man saccades and pursuit eye movements are reduced by benzodiazepines and barbiturates, but provide no support for the previously described efficacy of saccades in monitoring the effect of benzodiazepines. It is hypothesized that diazepam and thiopental also induce reduction of voluntary saccades and pursuit eye movements via a general sedation of the central nervous system (CNS), besides having specific effects on CNS structures important to the performance of voluntary eye movements.

Adult↗
PubMed1992

Reduced voluntary non-visual suppression of the vestibulo-ocular reflex gain during nitrous oxide narcosis.

The effect of subanesthetic nitrous oxide (N2O) narcosis (21%) on the vestibulo-ocular reflex (VOR) and on voluntary non-visual suppression of the VOR was studied in 12 subjects, using a velocity step rotational test. Gain and time constant of the VOR were calculated by computer. During tests, the subjects were required either to perform mental arithmetic or to attempt to follow an imaginary target rotating with them in the dark. Voluntary non-visual suppression of gain was significantly reduced during exposure to N2O, though there was no statistically significant effect of N2O on gain per se. The time constant was unaffected either by voluntary suppression or by N2O. The reducing effect of N2O on voluntary non-visual suppression of VOR gain is assumed to be due to reduced alertness. Reduced voluntary non-visual suppression of VOR may imply reduced visual-vestibular interaction, which might be one explanation of the complaints of dizziness associated with fatigue or with ingestion of certain sedatives.

Adult↗
PubMed1992

Impaired gut barrier in experimental chronic uremic rats.

The intestinal permeability in chronic uremic rats on a high- and a low-protein diet was measured with a mixture of differently sized polyethylene glycols (PEG 400 and PEG 1000). The permeability was assessed by the 24-hour urinary recovery of PEG molecules (range 326-1,162 Da) administrated orally or intravenously. The urinary recovery after oral load, when corrected with the recovery after intravenous administration, was significantly enhanced in the uremic rats. A decreased urinary recovery was observed in the groups on the low-protein feed diet. There was also decreased selectivity towards larger PEGs in uremia. The results thus suggest that (i) the intestinal permeability is increased in chronic uremic rats, and (ii) the intestinal permeability is influenced by a low-protein diet.

Animals↗
PubMed1992

Sensitivity to sensitins and tuberculin in Swedish children. IV. The influence of BCG-vaccination.

BCG-vaccinated schoolchildren, 8-9 yrs of age, were simultaneously tested on separate arms with tuberculin and a sensitin. Using the 6 mm cut-off they reacted in 49% to two tuberculin units purified protein derivative (PPD RT23), in 67% to 0.1 micrograms Mycobacterium avium sensitin RS10, and in 58% to 0.1 micrograms M. scrofulaceum sensitin RS95. The corresponding figures for non-BCG-vaccinated schoolchildren of the same age tested at the same time were 3, 25 and 32%, respectively. The results indicate a stimulating influence of BCG-vaccination on tuberculin and sensitin reactivity. Since the sensitin reactions were the larger ones, these reactions were not only due to the vaccination. The BCG-vaccinated schoolchildren seem to have acquired infections by atypical mycobacteria despite vaccination.

Antigens↗
PubMed1991

Optimal coordination and control of posture and locomotion.

This paper presents a theoretical model of stability and coordination of posture and locomotion, together with algorithms for continuous-time quadratic optimization of motion control. Explicit solutions to the Hamilton-Jacobi equation for optimal control of rigid-body motion are obtained by solving an algebraic matrix equation. The stability is investigated with Lyapunov function theory, and it is shown that global asymptotic stability holds. It is also shown how optimal control and adaptive control may act in concert in the case of unknown or uncertain system parameters. The solution describes motion strategies of minimum effort and variance. The proposed optimal control is formulated to be suitable as a posture and stance model for experimental validation and verification. The combination of adaptive and optimal control makes this algorithm a candidate for coordination and control of functional neuromuscular stimulation as well as of prostheses.

Algorithms↗
PubMed1991

Sensitivity to sensitins and tuberculin in Swedish children. III. Sequential versus simultaneous skin testing.

The aim of this study was to determine whether simultaneous and sequential skin testing with tuberculin and sensitins give consistent results. A total of 475 8- or 9-year-old schoolchildren were skin tested sequentially, at an interval of 3 days, with PPD tuberculin and with either Mycobacterium scrofulaceum or M. avium sensitin. The results were compared with those of 470 simultaneously tested children chosen from the same living area. There were no statistically significant differences between the frequencies of the reactions of sequentially and simultaneously tested children. When the sequential testing procedure was employed, 3.1% reacted to tuberculin, 19% to M. avium sensitin and 30% to M. scrofulaceum sensitin, taking a 6 mm cut-off. The corresponding figures for the simultaneously tested children were 4.7, 21 and 36%, respectively. Thus, there was no indication that the simultaneous testing procedure in itself influenced the results, neither was there any sign of a booster effect when testing in sequence with an interval of 3 days in non-BCG-vaccinated children.

Antigens↗
PubMed1991

Sensitivity to sensitins and tuberculin in Swedish children. I. A study of schoolchildren in an urban area.

Non-BCG-vaccinated schoolchildren (8 or 9 years of age) were simultaneously tested on separate arms with 2 IU PPD RT23 and 0.1 microgram Mycobacterium avium sensitin RS10 or 0.1 microgram Mycobacterium scrofulaceum sensitin RS95. None of the 2819 analysed children had any known exposure to tuberculosis. A total of 3.4% reacted with an induration greater than or equal to 6 mm to PPD RT23. Half the number of children were tested with M. avium sensitin and 25.4% reacted while the remaining were tested with M. scrofulaceum sensitin and 32.4% reacted when the cut-off was 6 mm. For about 90% of the children the sensitin reaction was larger than or equal to the tuberculin (PPD RT23) reaction. Correlation analyses showed that moderate and high PPD RT23 values were combined with still higher sensitin values, indicating that the tuberculin reactions were mainly cross-reactions due to the antigenic similarity between tuberculin and sensitins. The presence of birds, dogs and cats in the homes was combined with an increased frequency of children reacting to the sensitins used. The children with reactions to PPD RT23 greater than or equal to 6 mm were examined and chest X-rays were performed. None of them showed any signs or symptoms of mycobacterial disease. In non-BCG-vaccinated Swedish schoolchildren without clinical signs of tuberculosis and without known contact with a contagious tuberculous person, indurations less than 12 to 14 mm on tuberculin testing are probably caused by atypical mycobacteria. In such cases sensitin tests should be performed to verify the suspicion.

Animals↗
PubMed1991

Sensitivity to sensitins and tuberculin in Swedish children. II. A study of preschool children.

Non-BCG-vaccinated preschool children (4 or 5 years of age) were simultaneously tested on separate arms with a 2 IU PPD RT23 and 0.1 microgram Mycobacterium avium sensitin RS10 or 0.1 microgram Mycobacterium scrofulaceum sensitin RS95. None of the 762 children had any known exposure to tuberculosis. A total of 8.8% reacted with an induration (greater than or equal to 3 mm to PPD RT23 while 2% reacted with greater than or equal to 6 mm. Half the children were tested with M. avium sensitin: 18.9 and 7.8% reacted when 3 and 6 mm cut-off points, respectively, were taken. The remaining children were tested with M. scrofulaceum sensitin: 18.4 and 6.3%, respectively, reacted. In a previous study of schoolchildren aged 8 or 9 years, reactions to sensitins were considerably more frequent. Thus, sensitisation by atypical mycobacteria seems to increase from the preschool to the early school age. This finding probably reflects a continuous exposure of the children to atypical mycobacteria from various sources. The preschool children with a reaction to PPD RT23 greater than or equal to 6 mm were examined and chest X-rays were performed. All children were healthy but one child had enlarged lymph nodes in the mediastinum and abdomen. It cannot be excluded that these pathological findings were caused by atypical mycobacteria.

Age Factors↗
PubMed1991

Impaired intestinal barrier function measured by differently sized polyethylene glycols in patients with chronic renal failure.

The intestinal mucosa plays a fundamental role as the site for absorption of nutrients, and as an important barrier from potentially harmful agents in the intestinal lumen. Little is known of the permeability properties of the intestinal mucosa in uraemic patients. The intestinal permeability to differently sized polyethylene glycols (PEGs; range 326-1254 daltons) was studied in nine patients with chronic renal failure (24 hour endogeneous creatinine clearance 5-24 ml/minute). The maximum 24 hour urinary recovery of PEGs was decreased in the uraemic patients but relatively more of the larger than the smaller PEGs were found in these patients. The results suggest a reduced urinary recovery of PEGs caused by renal dysfunction but also a relatively increased intestinal permeability to larger PEGs in the uraemic patients.

Adult↗
PubMed1991

Small intestinal peptidases and disaccharidases in rats with acute uremia.

Acute uremia was induced in rats with temporary clamping of the left renal pedicle and contralateral nephrectomy. Jejunal peptidase activities (aminopeptidase N, dipeptidyl peptidase IV and aminopeptidase A), disaccharidase activities (maltase, sucrase, lactase and trehalase) and morphology were studied. A significant (p less than 0.05) increase in aminopeptidase N activity and a positive correlation between aminopeptidase N activity and serum urea was found in the uremic rats. The other peptidase activities showed a slight increase in the uremic rats. A shortening of the microvilli of the small intestinal epithelial cells in the uremic rats was seen by electron microscopy. The disaccharidase activities was unaltered. This study shows the presence of functional alterations in the small intestine in rats with acute uremia. The observations are also compatible with different regulation mechanisms for the brush border peptidases and disaccharidases.

Acute Disease↗
PubMed1991

Postural compensation in children with congenital or early acquired bilateral vestibular loss.

The relative roles of different receptor systems in compensating for vestibular loss were studied in 18 children (12 to 16 years of age) with congenital or early acquired bilateral vestibular loss (BVL) and impaired hearing, and compared to that in 33 normal children (9 to 16 years of age). Postural stability was studied with posturography evaluating the velocity of anterior-posterior body sway. With closed eyes the increase of sway velocity did not differ between the groups, either with or without simultaneous proprioceptive disturbances when the subjects were standing on a bare surface. Body sway velocities were found to increase more in subjects with a BVL than in normal children when subjects were standing on foam rubber. When proprioceptive cues were disturbed, body sway velocities increased in both groups, but significantly more in children with BVL when subjects stood on foam rubber. This occurred both with and without open eyes.

Adolescent↗
PubMed1991

Intervertebral motion during vibration.

Vibration exposure is widely recognized as a risk factor for low back pain. An experimental protocol was designed to quantify the intervertebral motion response in human subjects to sinusoidal vertical vibration at 5 and 8 Hz, and at a variety of acceleration levels. Intervertebral motion in the mid-sagittal plane was measured using a transducer linkage system attached to pins placed directly into the spinous processes of adjacent vertebrae. The postures of the subjects were carefully controlled. The effects of forward flexion, arm support, gravitational load, and sitting on a cushion were evaluated. The rigid body motion of the superior vertebra with respect to the inferior vertebra was expressed in terms of relative sagittal plane rotation, axial translation, and anterior-posterior shear translation. It was found that the lumbar motion segments exhibited coupled periodic behaviour in response to sinusoidal vertical vibration, with up to 1 mm peak-to-peak displacement in the axial direction. The greatest intervertebral motion occurred when the subject was exposed to 5 Hz vibration as compared to 8 Hz. For a constant frequency of 5 Hz excitation, the peak-to-peak amplitudes of the computed motions tended to increase as the acceleration level increased. In the flexed posture, with no arm support, the active trunk musculature helped reduce the intervertebral motion. Additional gravitational load on the shoulders caused increased relative axial displacement. A polyethylene foam cushion placed on the seat reduced vibration transmission at 5 Hz excitation and consequently decreased the intervertebral motion.

Adult↗
PubMed1991

Delayed onset of ototoxic effects of gentamicin in patients with Meniére's disease.

In treatment of Meniére's disease, installations of gentamicin are continued until there are signs of disturbance of vestibular or cochlear function. However, since it has been demonstrated that gentamicin is eliminated slowly from the inner ear, a continuing ototoxic effect may be suspected. The present study aimed to investigate the delay of onset of symptoms of ototoxic effects. Five patients with Meniére's disease and disabling vertigo were treated with intratympanic installation of gentamicin. The patients received two installations at two consecutive days, after which the treatment was abated, although no patient showed any symptoms of affection of the vestibular or cochlear end organs. All patients, however, developed vertigo and nystagmus beating toward the not treated ear within 3 to 5 days after the last installation. At 3 months and 1 year later, the treated ear showed no reaction on bithermal caloric stimulation and all patients had a complete relief of attacks of vertigo but hearing levels were about the same compared to before treatment. The present findings demonstrate a delayed onset of ototoxic effects and it is suggested that gentamicin treatment should not be carried on until symptoms develop. Furthermore, extremely low dose treatment may produce loss of vestibular function with the desired relief of vertigo and with less hazards of affecting the hearing level.

Adult↗