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Biomedical subjects

T Hansson

Publications and source records attributed to T Hansson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Ligand binding affinity prediction by linear interaction energy methods.

A recent method for estimating ligand binding affinities is extended. This method employs averages of interaction potential energy terms from molecular dynamics simulations or other thermal conformational sampling techniques. Incorporation of systematic deviations from electrostatic linear response, derived from free energy perturbation studies, into the absolute binding free energy expression significantly enhances the accuracy of the approach. This type of method may be useful for computational prediction of ligand binding strengths, e.g., in drug design applications.

Binding Sites↗
PubMed1998

Measurement of bone mineral using multiple-energy x-ray absorptiometry.

Our laboratory has previously reported a method of determining the amount of bone mineral using triple-energy absorptiometry with a continuous x-ray spectrum. In the present study, the experimental properties of the technique were examined. The accuracy, the influence of fat content and body thickness and the in vitro and in vivo precision were analysed. The results found in this investigation showed that despite the complexity of the technique, the amount of bone mineral can be accurately determined. The in vivo precision was determined to be 3.4%, expressed as the coefficient of variation (CV), for different skeletal parts. The in vitro precision was found to be 2.1% (CV). Neither the fat content nor the body thickness had any effect on the measured bone mineral values. Excellent linearity and a close correlation were found between the true and the measured bone mineral values.

Absorptiometry, Photon↗
PubMed1998

The feasibility of triple-energy absorptiometry for the determination of bone mineral, Ca and P in vivo.

The theoretical feasibility of triple-energy absorptiometry in general and the experimental conditions when using triple-energy absorptiometry for the determination of bone mineral, elemental calcium and phosphorus content in vivo have been investigated. A theoretical analysis of the decomposition of the mass attenuation coefficients is presented and discussed. The main obstacle to the effective use of triple-energy absorptiometry in vivo is the large number of pulses which must be detected to reduce the statistical fluctuations.

Absorptiometry, Photon↗
PubMed1998

Precompetitive mood states and performance of elite male golfers: do trait characteristics make a difference?

The relationship between preperformance mood, measured by the Profile of Mood States inventory, and subsequent athletic performance has been the focus of considerable research. Presumably, athletes with less positive mood profiles should be outperformed by those with more favorable profiles. The results presented so far in the literature are equivocal. One possible explanation is that more stable trait characteristics might medicate mood states prior to competitive situations. In the present study, 8 male golf players, all members of the Swedish National Team, completed a number of trait inventories (Eysenck's Personality Inventory, Locus of Control, Sport Competition Anxiety Test, Self-consciousness Scale) prior to the competitive season. Subsequently, they completed the Profile of Mood States before each game played. Analysis showed that the players' preperformance mood states differed significantly and that these differences were associated with their scores on the trait inventories. Furthermore, preperformance mood states were significantly related to athletic performance for some individuals but not for others. Further research should also include trait measurements to understand better the relationship between mood states and the athletic performance of individual athletes.

Adult↗
PubMed1998

Work-related low-back problems in nursing.

This scientific literature review focuses on the relation between nursing work and low-back problems. Its aim was to estimate the risk of physical, psychosocial, and work organizational exposure factors that may lead to low-back problems. In addition this paper reviews and evaluates reported ergonomic intervention, with the object of decreasing the prevalence and incidence of low-back problems among nurses. A considerable number of studies of nursing staff has shown the connection between lifts and transfers of patients on one hand and low-back problems on the other. Factors in nursing work that may be significant in this connection are staff density and work satisfaction. In this review the single individual factor that was indisputably related to low-back problems was "history of back problems". Prevention programs do not show unequivocally positive results. There is a great need to carry out prospective studies with preventive programs.

Adult↗
PubMed1998

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

Animals↗
PubMed1998

Life expectancy and cost utility after total hip replacement.

In a prospective study of 410 cemented hip replacements in 372 patients with a mean age of 71 years, mortality after 8 years was 33%. Mortality for patients with osteoarthrosis was lower than in an age matched control population, probably because of a preoperative selection of patients. An estimate of costs and adjusted quality of life has shown that total hip replacement has a good cost utility even in the elderly patient. The conclusion of this study is that the indications for hip replacement in the elderly patient can be expanded. Such patients should undergo surgery earlier in the course of their disease.

Adult↗
PubMed1998

Injuries in adolescent spine exposed to compressive loads: an experimental cadaveric study.

In a cadaveric experiment, 16 functional spinal units (FSUs) obtained from 7 subjects with a mean age of 16.3 years were tested in compression to failure. The deformation rate was 5 mm/min. The bone mineral content (BMC) in the vertebrae was determined by using dual-photon absorptiometry (DPA). In 15 of the FSUs, traumatic changes were registered. Three different types of changes were seen. In nine vertebrae, there was a rupture in the cartilaginous end plate, in 12, a separation of the end plate from the vertebral body, and in three vertebrae, a compression fracture was registered. A close relation was found between BMC and the ultimate force (r2 = 0.63), the ultimate displacement (r2 = 0.73), and the energy absorption (r2 = 0.74). The weakest part of a spinal segment in this experimental situation is the growth plate.

Absorptiometry, Photon↗
PubMed1997

Dynamic effects on the lumbar spinal canal: axially loaded CT-myelography and MRI in patients with sciatica and/or neurogenic claudication.

STUDY DESIGN: In patients with sciatica or neurogenic claudication, the structures in and adjacent to the lumbar spinal canal were observed by computed tomographic myelography or magnetic resonance imaging in psoas-relaxed position and during axial compression in slight extension of the lumbar spine. OBJECTIVES: To determine the mechanical effects on the lumbar spinal canal in a simulated upright position. SUMMARY OF BACKGROUND DATA: For years, functional myelographic investigation techniques were shown to be of value in the evaluation of suspected encroachment of the spinal canal. Since the advent of computed tomography and magnetic resonance imaging, there have been few clinical and experimental attempts that have imitated these techniques. The data indicate that the space within the canal is posture dependent. METHODS: Portable devices for axial loading of the lumbar spine in computed tomographic and magnetic resonance examinations were developed. Fifty patients (94 sites) were studied with computed tomographic myelography, and 34 patients (80 sites) with magnetic resonance in psoas-relaxed position followed by axial compression in slight extension. The dural sac cross-sectional area at L2 to S1, the deformation of the dural sac and the nerve roots, and the changes of the tissues surrounding the canal were observed. RESULTS: In 66 of the investigated 84 patients, there was a statistically significant reduction of the dural sac cross-sectional area in at least one site during axial compression in slight extension. Of the investigated patients, 29 passed the borderlines for relative (100 mm2) or absolute stenosis (75 mm2) in 40 sites. In 30 patients, there was deformation of the dural sac in 46 sites. In 11 of the patients investigated with magnetic resonance imaging, there was a narrowing of the lateral recess in 13 sites, during axial compression in slight extension. CONCLUSIONS: Axial loading of the lumbar spine in computed tomographic scanning and magnetic resonance imaging is recommended in patients with sciatica or neurogenic claudication when the dural sac cross-sectional area at any disc location is below 130 mm2 in conventional psoas-relaxed position and when there is a suspected narrowing of the dural sac or the nerve roots, especially in the ventrolateral part of the spinal canal in psoas-relaxed position. The diagnostic specificity of the spinal stenosis will increase considerably when the patient is subjected to an axial load.

Adult↗
PubMed1997

Cyclic HIV-1 protease inhibitors derived from mannitol: synthesis, inhibitory potencies, and computational predictions of binding affinities.

Ten C2-symmetric cyclic urea and sulfamide derivatives have been synthesized from L-mannonic gamma-lactone and D-mannitol. The results of experimental measurement of their inhibitory potencies against HIV-1 protease were compared to calculated free energies of binding derived from molecular dynamics (MD) simulations. The compounds were selected, firstly, to enable elucidation of the role of stereochemistry for binding affinity (1a-d) and, secondly, to allow evaluation of the effects of variation in the link to the P1 and P1' phenyl groups on affinity (1a and 2-5). Thirdly, compounds with hydrogen bond-accepting or-donating groups attached to the phenyl groups in the P2 and P2' side chains (6 and 7) were selected. Binding free energies were estimated by a linear response method, whose predictive power for estimating binding affinities from MD simulations was demonstrated.

Anti-HIV Agents↗
PubMed1997

Energetics of nucleophile activation in a protein tyrosine phosphatase.

The nucleophilic attack by cysteine 12 in the low-molecular-weight protein tyrosine phosphatase is believed to be carried out by the thiolate anion form of this residue. We here study the energetics of proton transfer between the thiol group of cysteine 12 and a substrate phosphate oxygen atom, to examine the effects of the enzymic environment on the stability of the thiolate nucleophile. This is done by molecular dynamics and free energy perturbation simulations, utilizing the empirical valence bond method to describe the potential surface of the system. The calculations show that the protein environment significantly stabilizes the thiolate ion, thereby setting the stage for the nucleophilic attack. We compare these results with those from further simulations of a mutant enzyme, and demonstrate the importance of serine 19 in thiolate stabilization.

Computer Simulation↗
PubMed1997

The upper extremity attenuates intermediate frequency vibrations.

Vibration is related to reports of low back pain; however the biomechanics of vibration transmission through the hand-arm system has not been previously studied. Vibration was recorded on an accelerometer mounted to a pin percutaneously imbedded in the spinous process of L4 of five human subjects. The energy was applied through an impact via a pendulum. The subjects adopted an erect, relaxed or bent knee posture. The first resonance was 4-6 Hz and the second at 9-14 Hz. With the knee bent, the signal was almost completely attenuated. If the impact was applied through a handle and the hand-arm system there was complete attenuation.

Acceleration↗
PubMed1997

Production of antibodies to gliadin by peripheral blood lymphocytes in children with celiac disease: the use of an enzyme-linked immunospot technique for screening and follow-up.

Problems in the diagnosis of celiac disease are that a long time is needed between challenge with gluten and the appearance of the typical diagnostic morphologic signs in gut mucosa. Furthermore, local immunity to gliadin is only slowly and often incompletely mirrored by serum IgA anti-gliadin antibody (AGA) levels. It is known that a local IgA-associated immune response in the gut may be better and more quickly mirrored by an increase of circulating IgA-producing cells against the immunogen than by IgA serum antibodies. We have therefore used an enzyme-linked immunospot (ELISPOT) assay to enumerate IgA AGA spot-forming cells (SFC) in peripheral blood in 82 children with suspected celiac disease or with other gastrointestinal symptoms. The numbers of IgA AGA SFC/10(6) mononuclear cells were markedly increased in 17 patients with untreated (and later biopsy-verified) celiac disease compared with healthy children, children with nonceliac disease, and patients treated for celiac disease (p < 0.0001). In 20 children with celiac disease the numbers of IgA AGA SFC increased rapidly (p < 0.0001) after gluten challenge. As early as 2 wk after gluten challenge, 15/20 of these patients had abnormal levels of IgA AGA SFC, 6/20 patients had increased levels of serum IgA AGA, and 7/20 had IgA anti-endomysium antibodies. Our results indicate that analysis of IgA AGA production in peripheral blood cells may in further clinical studies provide a sensitive method for the diagnosis of celiac disease after a short time of gluten challenge.

Adolescent↗
PubMed1997

Functional regeneration of C-fibres inside a silicone tube after sciatic neurotomy in rats.

Peripheral nerve lesions are often complicated by difficulties in approximating the nerve stumps without tension. The aim of the present study was to evaluate C-fibre function after nerve regeneration in rats in which the nerve had been lengthened by leaving a 5 mm gap inside a silicone tube (n = 5). The outcome was compared with nerve regeneration after epineural end-to-end suture (n = 5). The innervated skin territory was defined by Evans blue extravasation after antidromic nerve stimulation. Five rats acted as controls. After three months, there was similar functional reinnervation in both experimental groups, which indicates that silicone tubes may reduce tension over a nerve repair with no adverse effects.

Animals↗
PubMed1996

Differential effects of neuroleptic agents on hepatic cytochrome P-450 isozymes in the male rat.

We report the effects of various dopamine receptor-blocking drugs on gene and protein expression, as well as the activity of several hepatic cytochrome P-450 (CYP) enzymes in the male Sprague-Dawley rat. At equipotent doses (with respect to receptor blockade and behavioural tests), the dopamine D2-receptor selective sulpiride and remoxipride gave a conspicuous down-regulation of CYP2C11 and its associated androstenedione 16 alpha-hydroxylation activity as well as of the CYP2C11-specific mRNA. The average immunoidentified CYP2C11 levels correlated with the CYP2C11-specific mRNA levels in all treatment groups (r = 0.994), indicating a transcriptional mechanism. The CYP3A protein was also selectively down-regulated. In contrast, androstenedione 5 alpha-reduction was significantly increased. Clozapine, a non-selective neuroleptic, gave the same effects on the steroid metabolism as sulpiride and remoxipride. In contrast, diverging effects were observed for clozapine, compared to sulpiride and remoxipride, on the immunoidentified CYP1A2, CYP2B1, and CYP3A. These proteins were elevated by clozapine, and down-regulated by sulpiride and remoxipride. Our results are of interest for the interpretation of preclinical dose ranging toxicity tests of neuroleptic agents in rats. They may also be relevant in relation to certain interactions and adverse reactions observed in the clinical use of these drugs. The down-regulation of certain CYP enzymes is most likely mediated by an interaction with the growth hormone secretion.

Androstenedione↗
PubMed1996

Inferior functional sensory regeneration after suture of sciatic neurotomy in newborns compared with mature rats.

It is generally believed that nerve injuries in children regenerate better than those which occur in adults. However, there are no functional experimental studies that support this belief. This study evaluates the functional regeneration of polymodal C-fibres after nerve regeneration in newborn and mature rats 3 months after unilateral sciatic nerve neurotomy and suture. The distribution of polymodal C-fibres was tested by measuring the Evans blue-stained area in the skin after antidromic nerve stimulation. In the newborn group of regenerated animals showed that functional C-fibres were present in a significantly (P < 0.05) smaller area than found in the adult group. We conclude that the functional regeneration of C-fibres is superior in mature rats compared with newborns, 3 months after regeneration.

Age Factors↗
PubMed1996

Does a back support have a positive biomechanical effect?

Back supports, or lifting belts, are widely used. Subjects, free of low back pain, lifted in a simulated task, meeting the 1993 NIOSH guidelines. The back support reduced the electromyographic signal in the dorsal muscles. The back support also reduced the height loss as measured by a stadiometer. In most subjects the support also gave a subjective impression of increased support and increased lifting capacity.

Journal Article↗