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Biomedical subjects

K Laasonen

Publications and source records attributed to K Laasonen.

16 recordsLinked to original sources
PubMed2001

Coadsorption of CO and NO on the Pd(111) surface: combined ab initio and Monte Carlo study.

Adsorption and coadsorption of nitric oxide (NO) and carbon monoxide (CO) on the Pd(111) surface are studied by combining first principles (FP) calculations and Monte Carlo (MC) simulations. From FP adsorption energies and molecule-molecule interactions we construct an interaction model, which is used in MC. We do several simulations with different coverages and CO/NO ratios. The simulations provide 0.75 monolayer (ML) for a saturation coverage, which is in excellent agreement with experiments. The results indicate that at 0.75 ML coverage, NO molecules take over the hollow sites and push CO molecules mainly onto bridge sites.

Journal Article↗
PubMed2000

Oxygen molecule dissociation on the Al(111) surface

The dissociative adsorption of the O2 on the Al(111) surface is studied using ab initio calculations based on density-functional theory. In the sticking probability experiments an activation barrier for the O2 dissociation exists, but our calculations predict a barrier only for one trajectory. Also our results do not support the model of charge transfer from the surface to the molecule as a bond breaking mechanism. Instead, the increasing hybridization between O2 orbitals and Al states, when the adsorbate approaches the slab, is significant for the dissociation.

Journal Article↗
PubMed1998

No relation between apolipoprotein E alleles and obstructive sleep apnea.

Apolipoprotein E (ApoE) is a genetic risk factor influencing the development of cardiovascular diseases and Alzheimer's disease. Patients with obstructive sleep apnea (OSA) suffer an excess mortality and morbidity from cardiovascular diseases. The frequencies of ApoE alleles were determined in 291 patients with OSA and 728 controls. The distribution of ApoE alleles and genotypes showed no difference between OSA and controls.

Adult↗
PubMed1998

A new beclomethasone dipropionate multidose powder inhaler in the treatment of bronchial asthma.

The clinical efficacy, tolerability and acceptability of a new multidose powder inhaler (MDPI) containing beclomethasone dipropionate (BDP) were compared with those of a BDP aerosol administered with a large volume spacer (MDI-spacer) among adult asthmatics currently receiving from 500 to 1,000 microgram/day of an inhaled corticosteroid. During the study, the dosage of BDP from both devices was 400 microgram twice daily. Ninety-one patients were randomized to the MDPI group and 42 to the MDI-spacer group. The trial was performed as an open, randomized, parallel group multicenter study. The duration of the treatment period was 12 weeks, and the study was preceded by a 2-week run-in period. During the run-in period, the mean morning peak expiratory flow (PEF) was 487 and 466 1/min in the MDPI and MDI-spacer groups, respectively. After the 12-week treatment, the morning PEF was 491 1/min in the MDPI group and 463 1/min in the MDI-spacer group. The evening values were 500 and 479 1/min during the run-in period and 496 and 476 1/min after the 12-week treatment, respectively. Asthma symptom scores and the use of rescue medication were low in both groups, indicating good efficacy of the preparations tested. The median dose of histamine required to decrease forced expiratory volume in 1 s by 15% increased during the study from 800 to 1,098 microgram in the MDPI group and from 795 to 960 microgram in the MDI-spacer group. The most frequent adverse events in both groups were hoarseness and sore throat. There were no statistically significant differences between the treatment groups in serum cortisol values or in the number of patients with thrush. Seventy-two percent of the patients regarded the MDPI easier to use while 95% considered it more portable. Over 80% of the patients felt that the MDPI was also easier to clean and as easy or easier to learn to use than the MDI-spacer. To conclude, the novel powder inhaler is well tolerated and at least equally effective as the conventional MDI-spacer combination in the treatment of asthma with BDP. However, in everyday use, patients clearly favored the powder inhaler.

Administration, Inhalation↗
PubMed1997

Circulating endothelin-1 in obstructive sleep apnea.

Endothelin (ET)-1 is a potent vasoconstrictive and mitogenic peptide produced by endothelial cells and degraded predominantly in pulmonary vasculature. We measured ET-1 in 9-normotensive and 14 hypertensive men with obstructive sleep apnea. The ET-1 levels were higher in both normotensive (mean +/- SD, 6.3 +/- 2.8 pg/ml) and hypertensive (7.8 +/- 3.0 pg/ml) groups than in 66 healthy controls (2.9 +/- 1.2 pg/ml). Ten patients were restudied after three months of nCPAP treatment. No decrease in ET-1 was observed.

Adult↗
PubMed1996

Ab initio molecular dynamics study of proton transfer in a polyglycine analog of the ion channel gramicidin A.

Proton transfer in biological systems is thought to often proceed through hydrogen-bonded chains of water molecules. The ion channel, gramicidin A (gA), houses within its helical structure just such a chain. Using the density functional theory based ab initio molecular dynamics Car-Parrinello method, the structure and dynamics of proton diffusion through a polyglycine analog of the gA ion channel has been investigated. In the channel, a proton, which is initially present as hydronium (H3O+), rapidly forms a strong hydrogen bond with a nearest neighbor water, yielding a transient H5O2+ complex. As in bulk water, strong hydrogen bonding of this complex to a second neighbor solvation shell is required for proton transfer to occur. Within gA, this second neighbor shell included not only a channel water molecule but also a carbonyl of the channel backbone. The present calculations suggest a transport mechanism in which a priori carbonyl solvation is a requirement for proton transfer.

Biophysical Phenomena↗
PubMedDate not supplied

Effect of once-a-week training program on physical fitness and metabolic control in children with IDDM.

To examine whether a physical activity program could improve physical fitness and glycemic control, 32 children and adolescents with insulin-dependent diabetes mellitus (IDDM) were examined before the program and 3 mo later. Fifty percent of the subjects (n = 16) participated in the training for 1 h/wk (exercise group), whereas the remaining subjects were engaged in nonphysical activities for an equal amount of time (nonexercise group). Age of the subjects ranged from 8.2 to 16.9 yr, (mean 11.9 yr), with mean duration of diabetes 0.6-13.1 yr (5.2 yr). During the 3-mo program peak oxygen consumption (VO2) rose from 40.0 to 43.8 ml.min-1.m-2 (P less than .01) in the exercise group but only by 1.3 ml.min-1.m-2 in the nonexercise group (NS). Metabolic control did not improve in either group, with glycosylated hemoglobin level rising from 9.8 to 10.5% (P less than .01) in the exercise group and from 9.4 to 9.7% (NS) in the control group. When subjects were stratified according to their participation, metabolic control was significantly better among diabetic subjects participating frequently (greater than or equal to 11 of 13 sessions) than among those participating infrequently (less than 11 of 13 sessions), regardless of the type of activity. It was concluded that a training program of 1 h/wk for 3 mo does improve physical fitness but not the metabolic control of diabetes. On the other hand, glycemic control appears to be best among diabetic subjects who are motivated to participate in any kind of program related to the treatment of their disease.

Adolescent↗