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Biomedical subjects

N Andersson

Publications and source records attributed to N Andersson.

At least 19 recordsLinked to original sources
PubMed2001

Two computerized methods used to analyze intracranial pressure B waves: comparison with traditional visual interpretation.

OBJECT: Slow and rhythmic oscillations in intracranial pressure (ICP), also known as B waves, have been claimed to be one of the best preoperative predictive factors in idiopathic adult hydrocephalus syndrome (IAHS). Definitions of B waves vary widely, and previously reported results must be treated with caution. The aims of the present study were to develop a definition of B waves, to develop a method to estimate the B-wave content in an ICP recording by using computer algorithms, and to validate these procedures by comparison with the traditional visual interpretation. METHODS: In eight patients with IAHS, ICP was continuously monitored for approximately 20 hours. The ICP B-wave activity as a percentage of total monitoring time (B%) was estimated by using visual estimation according to the definition given by Lundberg, and also by using two computer algorithms (Methods I and II). In Method I each individual wave was classified as a B wave or not, whereas Method II was used to estimate the B-wave content by evaluating the B-wave power in 10-minute blocks of ICP recordings. CONCLUSIONS: The two computerized algorithms produced similar results. However, with the amplitude set to 1 mm Hg, Method I yielded the highest correlation with the visual analysis (r = 0.74). At least 5 hours of monitoring time was needed for an acceptable approximation of the B% in an overnight ICP recording. The advantages of using modern technology in the analysis of B-wave content of ICP are obvious and these methods should be used in future studies.

Aged↗
PubMed2000

Superradiance resonance cavity outside rapidly rotating black holes

We discuss the late-time behavior of a dynamically perturbed Kerr black hole. We present analytic results for near-extreme Kerr black holes that show that the large number of virtually undamped quasinormal modes that exist for nonzero values of the azimuthal eigenvalue m combine in such a way that the field oscillates with an amplitude that decays as 1/t at late times. This prediction is verified using numerical time evolutions of the Teukolsky equation. We argue that the observed behavior can be understood in terms of the presence of a "superradiance resonance cavity" immediately outside the black hole, and discuss whether it may be relevant for astrophysical black holes.

Journal Article↗
PubMed2000

r-Mode Runaway and Rapidly Rotating Neutron Stars.

We present a simple spin-evolution model that predicts that rapidly rotating accreting neutron stars will be confined mainly to a narrow range of spin frequencies: P=1.5-5 ms. This is in agreement with current observations of neutron stars in both the low-mass X-ray binaries and the millisecond radio pulsars. The main ingredients in the model are (1) the instability of r-modes above a critical spin rate, (2) the thermal runaway that is due to the heat released as viscous damping mechanisms counteract the r-mode growth, and (3) a revised estimate of the strength of the dissipation that is due to the presence of a viscous boundary layer at the base of the crust in an old and relatively cold neutron star. We discuss the gravitational waves that are radiated during the brief r-mode-driven spin-down phase. We also briefly touch on how the new estimates affect the predicted initial spin periods of hot young neutron stars.

Journal Article↗
PubMed1999

Gastrin effects on isolated rat enterochromaffin-like cells following long-term hypergastrinaemia in vivo.

The enterochromaffin-like (ECL) cells play an important role in the regulation of gastric acid secretion. They respond to gastrin by a prompt increase in histamine secretion, an effect which is mediated by the CCK-(B)/gastrin receptor acting through the IP(3)/DAG pathway. In the rat, long-term treatment with acid secretion inhibitors induces hypergastrinaemia which, in turn, results in ECL cell hypertrophy and hyperplasia. The aim of the present study was to evaluate various functional parameters in acutely isolated rat ECL cells, following long-term hypergastrinaemia in vivo. Rats were treated with vehicle or a supramaximal daily dose of omeprazole for more than 10 weeks to ensure ECL cell hyperplasia. ECL cells were isolated from vehicle-treated animals and 24, 72 and 120 h after the last dose of omeprazole. The functional activity of the acutely isolated ECL cells was determined by measuring gastrin-and forskolin-induced histamine secretion. Changes in cytosolic free calcium upon gastrin stimulation were monitored by digital video imaging. ECL cells successively regained their ability to respond to gastrin following long-term hypergastrinaemia, reaching close to vehicle-treated levels 120 h after the last dose of omeprazole. In the rat, the response pattern of the ECL cells appears to normalise in parallel with the normalisation of plasma gastrin levels.

Animals↗
PubMed1997

Evaluation of single-dose inhaled corticosteroid activity with an allergen challenge model.

BACKGROUND: Inhaled corticosteroids are the most commonly used antiinflammatory agents for asthma. There is no simple way to compare objectively the relative potency of inhaled corticosteroids. The allergen-induced late asthmatic response (LAR) can be suppressed by a single dose of inhaled corticosteroid. OBJECTIVE: This study was undertaken to evaluate LAR as a model for the determination of the relative potency of single doses of inhaled corticosteroids. METHODS: We compared doses of 200 and 800 microg of a highly active inhaled corticosteroid (budesonide) with placebo and a marginally active investigational inhaled corticosteroid (D5159). Ten atopic patients with asthma completed a randomized, double-blind, double-dummy, multicenter, four-way, crossover trial. A standardized allergen challenge with the identical dose of allergen was performed 10 minutes after each of four blinded, single-dose treatments: 200 microg of budesonide, 800 microg of budesonide, 8 mg of D5159, and placebo, all administered from Turbuhaler. The LAR was recorded as the maximum percent fall in FEV1 between 4 and 7 hours, and the allergen-induced increase in methacholine airway responsiveness at 24 hours was recorded as the A log PC20 from the day before to the day after allergen challenge. RESULTS: There were no significant differences in the early asthmatic responses during the 4 days; the mean maximum percent in FEV1 fall ranged between 19.5% and 22%. D5159 produced a slight inhibition of the LAR with maximum percent fall in FEV1 recorded as 28.8% +/- 5.0% for D5159 versus 34.1% +/- 4.8% for placebo (p < 0.05). There was a greater reduction recorded after administration of the two doses of budesonide. The mean LAR was 15.1% +/- 3.8% for 200 microg of budesonide and 11.2% +/- 2.3% for 800 microg of budesonide (p < 0.01 compared with placebo and D5159). The two doses of budesonide were not statistically different. Airway responsiveness to methacholine increased by 1.07 doubling doses 24 hours after allergen challenge. This increased airway responsiveness was slightly, but not significantly, reduced by the three active treatments (0.6 to 0.91 doubling doses). CONCLUSION: The allergen-induced LAR model was able to differentiate a single dose of an active inhaled corticosteroid from placebo and a highly potent inhaled corticosteroid from a weak inhaled corticosteroid. The model did not differentiate between 2 fourfold doses of the highly active inhaled corticosteroid (at the doses used in this study), neither for the fall in FEV1 nor for the increase in airway hyperresponsiveness.

Administration, Inhalation↗
PubMed1996

Effect of inclination on the results of the maximal anaerobic running test.

This study investigated the effect of treadmill inclination on the maximal anaerobic running test (MART). Ten male subjects ran a 20-m speed test on a track to determine the maximal running velocity (V20m) and performed three MARTs at the grades of 1 degree, 4 degrees and 7 degrees in a random order. Each MART included n 20-s sprints at gradually increased velocity and counter-movement jumps (CMJ) which were performed before and after the exhausting sprints. At each grade, the power (oxygen demand) of the sprints was determined by extrapolating the individual steady state oxygen uptake of three submaximal running velocities measured separately at the corresponding grades. Maximal power (Pmax), power at 10mM (P10mM) and 5 mM (P5mM) blood lactate levels as well as peak blood lactate concentration (peak BLa) were determined at each MART. The Pmax increased from 94.1 +/- 8.8 and 110.0 +/- 10.2 to 119.5 +/- 8.0 ml.kg-1.min-1 when the treadmill inclination increased from 1 degree and 4 degrees to 7 degrees, respectively (p < 0.001). P10mM and P5mM also increased with the inclination (p < 0.001). Correlation coefficients of the Pmax with CMJrest and V20m were 0.77 and 0.69 at the grade of 1 degree, 0.75 and 0.59 at the grade of 4 degrees, and 0.62 and 0.42 at the grade of 7 degrees, respectively. The increased peak BLa (p < 0.01) with the treadmill inclination suggests that lactic capacity was not completely used at the grades of 1 degree and 4 degrees. In conclusion, the maximal power increased with the grade of uphill running in the MART. Furthermore, the present results suggest that the importance of force and velocity components of the neuromuscular system decreased and the importance of metabolic component increased with the increased grade of the uphill running.

Adult↗
PubMed1996

Assessment of the relative systemic potency of inhaled fluticasone and budesonide.

Studies using dry powder devices have suggested that fluticasone propionate (FP) has a greater systemic effect than budesonide (BUD). The aim of the present study was to investigate and compare the relative systemic potency of FP and BUD from their respective pressurized metered-dose inhalers (pMDIs). A placebo-controlled, open, randomized, cross-over study was conducted in 21 healthy male volunteers. Placebo, BUD (200, 400 and 1,000 micrograms b.i.d.) and FP (200, 375 and 1,000 micrograms b.i.d.) were inhaled for 4 days, with a wash-out period of at least 3 days between treatments. Blood samples for cortisol analysis were drawn during the last 24 h of each treatment period. Cortisol levels, measured as 24 h pooled plasma cortisol, were statistically significantly lower (p = 0.0001) for all dose levels during FP pMDI treatment (21, 39 and 84% suppression from placebo) than during BUD pMDI treatment (1, 3 and 27% suppression from placebo). The relative systemic potency FP:BUD was 3.7:1 (95% confidence interval (95% CI) 2.9-4.8)). The relative systemic potency based on the single 08:00 h samples was 5.2:1 (95% CI 3.0-9.3). In conclusion, in healthy male volunteers using pressurized metered-dose inhalers, fluticasone propionate was shown to have a stronger systemic effect than budesonide.

Administration, Inhalation↗
PubMed1995

Social cost of land mines in four countries: Afghanistan, Bosnia, Cambodia, and Mozambique.

OBJECTIVES: To document the effects of land mines on the health and social conditions of communities in four affected countries. DESIGN: A cross design of cluster survey and rapid appraisal methods including a household questionnaire and qualitative data from key informants, institutional reviews, and focus groups of survivors of land mines from the same communities. SETTING: 206 communities, 37 in Afghanistan, 66 in Bosnia, 38 in Cambodia, and 65 in Mozambique. SUBJECTS: 174,489 people living in 32,904 households in the selected communities. MAIN OUTCOME MEASURES: Effects of land mines on food security, residence, livestock, and land use; risk factors: extent of individual land mine injuries; physical, psychological, social, and economic costs of injuries during medical care and rehabilitation. RESULTS: Between 25% and 87% of households had daily activities affected by land mines. Based on expected production without the mines, agricultural production could increase by 88-200% in different regions of Afghanistan, 11% in Bosnia, 135% in Cambodia, and 3.6% in Mozambique. A total of 54,554 animals was lost because of land mines, with a minimum cash value of $6.5m, or nearly $200 per household. Overall, 6% of households (1964) reported a land mine victim; a third of victims died in the blast. One in 10 of the victims was a child. The most frequent activities associated with land mine incidents were agricultural or pastoral, except in Bosnia where more than half resulted from military activities, usually during patrols. Incidences have more than doubled between 1980-3 and 1990-3, excluding the incidents in Bosnia. Some 22% of victims (455/2100) were from households reporting attempts to remove land mines; in these households there was a greatly increased risk of injury (odds ratio 4.2 and risk difference 19% across the four countries). Lethality of the mines varied; in Bosnia each blast killed an average of 0.54 people and injured 1.4, whereas in Mozambique each blast killed 1.45 people and wounded 1.27. Households with a land mine victim were 40% more likely to experience difficulty in providing food for the family. Family relationships were affected for around one in every four victims and relationships with colleagues in 40%. CONCLUSIONS: Land mines seriously undermine the economy and food security in affected countries; they kill and maim civilians at an increasing rate. The expense of medical care and rehabilitation add economic disability to the physical burden. Awareness of land mines can be targeted at high risk attitudes, such as those associated with tampering with mines.

Adolescent↗