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Biomedical subjects

S Michelsen

Publications and source records attributed to S Michelsen.

At least 19 recordsLinked to original sources
PubMed2006

Fast-ion dynamics in the TEXTOR tokamak measured by collective Thomson scattering.

Here we present the first measurements by collective Thomson scattering of the evolution of fast-ion populations in a magnetically confined fusion plasma. 150 kW and 110 Ghz radiation from a gyrotron were scattered in the TEXTOR tokamak plasma with energetic ions generated by neutral beam injection and ion cyclotron resonance heating. The temporal behavior of the spatially resolved fast-ion velocity distribution is inferred from the received scattered radiation. The fast-ion dynamics at sawteeth and the slowdown after switch off of auxiliary heating is resolved in time. The latter is shown to be in close agreement with modeling results.

Journal Article↗
PubMed2000

Residual pulmonary hypertension in children after treatment with inhaled nitric oxide: a follow-up study regarding cardiopulmonary and neurological symptoms.

UNLABELLED: Inhaled nitric oxide is a potent vasodilator in acute severe pulmonary hypertension and is increasingly used as rescue treatment in intensive care algorithms aiming at reducing severe hypoxaemia in neonates and children. Although the immediate effects may seem impressive, long-term outcome regarding residual pulmonary hypertension and other sequelae has been studied in only a very few patients. The aim of the present study was to evaluate residual pulmonary hypertension, cardiopulmonary or neurological symptoms in children after treatment with inhaled nitric oxide in severely hypoxaemic and/or pulmonary hypertensive mechanically ventilated children. The study was performed in four paediatric intensive care units in university hospitals in Sweden, Norway and Australia. Patients who had received inhaled nitric oxide as part of their intensive care treatment for severe hypoxaemia and/or pulmonary hypertension, and in whom 6 mo had elapsed since treatment, were included for evaluation. Thus 36 paediatric or neonatal patients were examined for circulatory, respiratory or neurological disorders with clinical examination, echocardiography, chest X-ray and a capillary blood sample. Four patients with congenital heart disease had residual pulmonary hypertension. Nine patients were receiving bronchodilators. Sixteen patients had minor (n = 15) or moderate (n = 1) changes on a chest X-ray. One patient had a possible delay in psychomotor development. CONCLUSIONS: In spite of the severity of their primary illness, we found that the overwhelming majority of the surviving children were asymptomatic and doing well. The few residual circulatory and respiratory symptoms could be related to the initial condition.

Administration, Inhalation↗
PubMed1999

Long-term application of extracorporeal photochemotherapy in severe atopic dermatitis.

BACKGROUND: Extracorporeal photochemotherapy (ECP) using UVA irradiation of enriched leukocytes in the presence of methoxsalen as a photoactivatable substrate has been employed for the treatment of several immunologically mediated disorders. OBJECTIVE: Our purpose was to determine the efficacy and safety of long-term ECP in the treatment of severe atopic dermatitis. METHODS: Fourteen patients with severe recalcitrant atopic dermatitis were treated with ECP in an open clinical trial at 2-week intervals. Disease activity was scored before each ECP cycle by means of a standardized protocol. RESULTS: A complete clinical remission was achieved in 4 patients (29%). Five patients (36%) experienced a substantial response with reduction of skin inflammation by at least 75%, whereas in one patient (7%) disease activity was reduced by more than 50%. Four patients were withdrawn from the study for unresponsiveness. No clinical signs of immunosuppression or other severe adverse events became evident. CONCLUSION: Long-term ECP may have significant beneficial effects on the course of atopic dermatitis and should therefore be considered as a treatment modality for patients suffering from severe and otherwise refractory atopic skin disease.

Adult↗
PubMed1998

[Pustular dermatitis after administration of a too highly concentrated dithranol ointment in seborrhea].

Seborrhoic dermatitis is an erythematosquamous condition of unknown etiology with a prevalence of approximately 2.5%. Frequently difficult to treat, it may respond to the application of low doses of dithranol, a substance which can induce a pustular dermatitis as an adverse side effect depending on the applied concentration and individual susceptibility. We describe a pustular dermatitis after the application of a preparation containing dithranol at an erroneously high concentration in a 30-year-old patient with seborrhoic dermatitis.

Administration, Topical↗
PubMed1998

Thyroid function during and after cardiopulmonary bypass in children.

BACKGROUND: The aim of the study was to elucidate the changes in thyroid function during and after cardiopulmonary bypass (CPB) in children. METHODS: Triiodothronine (T3), thyroxine (T4), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were determined preoperatively, at specific times throughout CPB, and serially up to 48 h postoperatively, in 10 children (median age 35, range 23-68 months) undergoing elective surgery for congenital heart disease. RESULTS: T3 decreased from 2.01 +/- 0.08 preoperatively to 0.94 +/- 0.10 nmol/l 24 h postoperatively (P < 0.05). T4 levels followed a pattern similar to changes in T3. FT4 increased from 17.4 +/- 0.7 preoperatively to 30.0 +/- 0.4 pmol/l after 30 min of CPB (P < 0.05). TSH decreased from 2.44 +/- 0.43 preoperatively to 0.93 +/- 0.21 24 h postoperatively (P < 0.05). CONCLUSION: T3, T4 and TSH are significantly depressed after open heart surgery in children.

Cardiopulmonary Bypass↗
PubMed1996

Release of interleukin 6 and activation of complement during and after paediatric cardiopulmonary bypass. Effect of autotransfusion of shed mediastinal blood and ultrafiltration.

Interleukin-6 (IL-6) and the complement activation products C3bc and terminal complement complex (TCC) were measured in three groups of children undergoing open heart surgery. One group was treated with intraoperative extracorporeal ultrafiltration and postoperative autotransfusion of shed mediastinal blood, one group was subjected to autotransfusion only and in one group none of these procedures were performed. No differences between the groups were observed concerning the degree of complement activation. Peak and total accumulated level of IL-6 was significantly higher in the group subjected to ultrafiltration and autotransfusion compared to the group treated conventionally with no interventions. IL-6 may be a sensitive marker of maneuvres increasing the inflammatory load during and after open heart surgery in children.

Biomarkers↗
PubMed1996

Release of soluble tumour necrosis factor alpha receptors during and after paediatric cardiopulmonary bypass. Correlation with haemodynamic and clinical variables.

The release of cytokines during cardiopulmonary bypass (CPB) may contribute to haemodynamic alternations encountered after open heart surgery. Regulatory mechanisms exist and include soluble cytokine receptors. We have measured blood levels of tumour necrosis factor (TNF) and its soluble receptor (TNFsr) during and after open heart surgery in children. Correlation analysis to haemodynamic and clinical variables was performed. Using immunoassays the authors registered a significant increase in plasma levels of TNFsr with peak levels 2 h post-operatively at a level of 1702 +/- 170 pg/ml. The concentration of TNFsr remained significantly elevated until 48 h postoperatively but TNF was not significantly elevated. An inverse correlation existed between peak TNFsr and mean arterial pressure (rho = -0.827, P < 0.05), between TNFsr and cardiac index (rho = -0.8, P < 0.05), between TNFsr and left ventricular stroke work index (rho = -0.983, P < 0.01), between TNFsr and weight (rho = -0.85, P < 0.05) and between TNFsr and body surface area (rho = -0.867, P < 0.05). The authors demonstrate that the smallest children experienced the highest TNFsr concentration post-operatively. Furthermore cardiac performance, expressed as cardiac index and left ventricular stroke work index, correlated inversely to peak TNFsr level post-operatively.

Cardiopulmonary Bypass↗
PubMed1996

Release of interleukin-8 and calprotectin during and after paediatric cardiopulmonary bypass with and without ultrafiltration.

Release of calprotectin and interleukin-8 (IL-8), changes in leukocyte counts and subsets and influence of extracorporeal ultrafiltration were evaluated during and after cardiopulmonary bypass (CPB) in 18 children undergoing open-heart surgery for congenital heart anomalies. Ultrafiltration was used in nine cases and nine were controls. Calprotectin concentration rose after start of CPB, peaking 48 hours postoperatively, with no significant intergroup difference. Positive correlation was found between duration of CPB and calprotectin (peak level and accumulated total). Circulating IL-8 was detected in all patients perioperatively, peaking at wound closure in the ultrafiltration group and at termination of bypass in the controls. CPB duration correlated significantly to peak level and accumulated total of IL-8. Seven of nine ultrafiltrate samples contained IL-8 at levels similar to the plasma concentration. Changes in white cell counts were mainly attributable to neutrophils. The two subgroups did not differ significantly in neutrophil counts. Neutropenia found after 10 minutes of CPB was replaced by neutrophilia, with maximal values postoperatively. Calprotectin and IL-8 thus were released into the circulation during CPB in children. Ultrafiltration did not affect the plasma concentrations of these substances, and only IL-8 was detected in the ultrafiltrate.

Calcium-Binding Proteins↗
PubMed1996

Ultrafiltration after cardiopulmonary bypass in children: effects on hemodynamics, cytokines and complement.

OBJECTIVES: The purpose of the study was to evaluate the clinical and hemodynamic effect of intraoperative extracorporeal ultrafiltration (UF) and its potential in reducing the plasma concentration of circulating cytokines and complement activation products following open heart surgery in children. METHODS: Eighteen children with congenital heart disease were prospectively randomized into a control group (n = 9) and a group who underwent UF (n = 9). Serial plasma samples for measurements of circulating cytokines (interleukin 6 (IL-6), tumor necrosis factor alpha (TNF), and its soluble receptor (sTNF receptor)), and complement factors (C3 activation products (C3a and C3bc) and terminal complement complex (TCC)) were obtained before, during and up to 48 h after cardiopulmonary bypass (CPB). A pulmonary artery thermodilution catheter was introduced preoperatively for hemodynamic monitoring. RESULTS: Postoperative hemodynamics were similar in both groups. Plasma levels of IL-6, sTNF receptors, C3a, C3bc and TCC increased significantly perioperatively (P < 0.01) in both groups. TNF was detected transiently in 16 patients perioperatively and in 4 of the 9 ultrafiltrate samples in concentrations similar to the plasma levels. Complement activating products were not detected in the ultrafiltration samples except for small amounts of C3a in two cases. Compared to the control group the plasma levels of C3a, C3bc and TCC were unaffected by the ultrafiltration procedure. The level of IL-6 and sTNF receptors increased significantly after 15 min of UF but there was no significant difference between the two groups postoperatively. CONCLUSIONS: In this study no clinical or hemodynamic effect was registered after UF. TNF and C3a were occasionally detected in the ultrafiltrate but we were unable to demonstrate reduction of these or any of the other markers tested in the group subjected to ultrafiltration.

Cardiopulmonary Bypass↗
PubMed1995

Complement activation and release of tumour necrosis factor alpha, interleukin-2, interleukin-6 and soluble tumour necrosis factor and interleukin-2 receptors during and after cardiopulmonary bypass in children.

C3 activation products, terminal complement complex (TCC), and cytokines including interleukins 6 and 2 (IL-6, IL-2) and tumour necrosis factor-alpha (TNF), and the soluble IL-2 and TNF receptors were determined serially during and up to 48 h after open heart surgery in children. Significant increases were noted in soluble TNF and IL-2 receptor levels postoperatively (p < 0.05). No significant increase over preoperative levels was seen in the cytokines, except for IL-6 which was significantly increased postoperatively (p < 0.01), reaching a maximum 2 h postoperatively. C3 activation products and TCC levels increased significantly after weaning from cardiopulmonary bypass (p < 0.05). The IL-6 response lagged behind the complement activation. We found a significant correlation between duration of cardiopulmonary bypass and IL-6 levels 48 h postoperatively (r = 0.852, p < 0.05). We conclude that the concentration of complement activation products, IL-6 and the soluble TNF and IL-2 receptors are significantly increased after open heart surgery in children. The cytokine receptor response probably reflects some sort of regulatory mechanism.

Cardiopulmonary Bypass↗
PubMed1995

Activation of the fibrinolytic, coagulation and plasma kallikrein-kinin systems during and after open heart surgery in children.

Activation of the fibrinolytic, coagulation and plasma kallikrein-kinin systems may be responsible for some of the coagulation disorders and inflammatory sequelae seen after extracorporeal circulation. The activation pattern of these systems was studied in 10 children undergoing open heart surgery with extracorporeal circulation. Blood samples were drawn serially before, during and up to 48 h after surgery. The heparin injection induced a significant elevation of plasmin (PL) (p < 0.05) which stayed elevated during extracorporeal circulation. Antiplasmin (AP) values were reduced at wound closure, while the levels were significantly elevated 48 h postoperatively (p < 0.05). alpha 2-antiplasmin-plasmin (APP) increased significantly perioperatively peaking 10 min after the initiation of cardiopulmonary bypass (p < 0.05). The coagulation markers thrombin-antithrombin (TAT) and the prothrombin fragment F1 & 2 increased significantly, peaking at wound closure and at termination of bypass respectively (p < 0.05). Plasma kallikrein (KK) values increased significantly with subsequent decreased levels of prekallikrein (PKK) and kallikrein inhibitor (KKI) after heparin injection. The KK level stayed elevated during cardiopulmonary bypass (CPB). The proenzyme functional inhibition index (PFI index), defined as the sum of deviations from the control values for proenzyme and functional inhibition values of the coagulation, fibrinolytic and plasma kallikrein-kinin systems, correlated significantly to the duration of cardiopulmonary bypass (p < 0.05). We conclude that open heart surgery in children activates the fibrinolytic, coagulation and plasma kallikrein-kinin systems.

Antifibrinolytic Agents↗
PubMed1994

6-Hydroxy-4-sphingenine in human epidermal ceramides.

The solvent-extractable lipids of human epidermal stratum corneum consist predominantly of ceramides. In addition two non-extractable ceramides are chemically bound to the stratum corneum protein. One of the bound ceramides, constituting 50% of the bound lipids, was previously shown to consist of very long chan omega-hydroxyacids in amide linkage with sphingosine. The second bound caramide, which forms 25% of the bound lipids, was shown to contain the same hydroxyacids, but the sphingoid base was neither sphingosine nor phytosphingosine. In the present study, the undefined bound ceramide was shown by NMR and chemical procedures to be the omega-hydroxyacid derivative of a new base, 6-hydroxy-4-sphingenine. In addition, a ceramide previously known to constitute 25% of the extractable human stratum corneum ceramides has been found to contain the same novel sphingoid base, amide-linked to long-chain alpha-hydroxyacids. Finally, a new acylceramide has been isolated and identified that consists of very long chain omega-hydroxyacids in amide linkage with the novel sphingolipid, with fatty acids esterified wit the terminal hydroxyl group of the hydroxyacid.

Adult↗
PubMed1991

Validity of the ECG diagnosis of left ventricular hypertrophy in normotensive and moderately hypertensive men when using the echocardiographic assessment of left ventricular mass index as reference.

The diagnostic validity of ECG criteria for left ventricular hypertrophy (LVH) was assessed in 100 men aged 22-64 (mean 47) years with moderate hypertension (Group 1) and 95 age-matched normotensive men (Group 2) using echocardiographic recordings of LV mass index (MI) as reference. A diagnosis of LVH was made in subjects with LVMI greater than or equal to 125 g/m2. Mean LVMI was 126 +/- 34 g/m2 in Group 1 vs. 100 +/- g/m2 in Group 2 (P less than 0.001), and the prevalence of LVH was 48% and 11% respectively (P less than 0.001). The mean ECG voltage according to Sokolow-Lyon (S-L) was 28 +/- 8 mm in Group 1 and 27 +/- 7 mm in Group 2 (NS); with 19% having LVH in Group 1 and 14% in Group 2 (NS). Using the Cornell criterion Group 1 had on average 15 +/- 6 mm vs. 12 +/- 5 mm in Group 2 (P less than 0.001), but only two Group 1 patients had LVH. In Group 2 a significant negative correlation between age and S-L voltage was found (r = 0.33, P less than 0.001). LVMI was not correlated with any of the two voltage criteria using linear regression analysis whereas multiple regression analysis revealed a weak, but significant correlation between LVMI and S-L voltage in Group 1 (t = 2.06, P = 0.04). No subject had LV strain pattern or LVH according to the Romhilt Estes point score system. In the assessment of possible LVH in normal or moderately hypertensive men less than 65-70 years of age, ECG has limited value.

Adult↗
PubMed1991

Correlations between left ventricular mass and systolic blood pressure at rest and during maximal exercise in moderately hypertensive men.

We examined 87 men with moderate hypertension (diastolic blood pressure, DPB, greater than or equal to 95 and less than 110 mmHg) (mean age 45, range 22-64, years) with echocardiography and maximal ergometer bicycle test. Left ventricular mass index (LVMI) was calculated according to the Penn convention. Mean LVMI was 126 (60-210) g/m2. The maximal systolic blood pressure (SBP) during exercise was on average 217 (155-260) mmHg. Linear regression analysis revealed a significant correlation between LVMI and SBP at rest (r = 0.48, P less than 0.001) and during exercise (r = 0.39, P less than 0.001). Multiple regression analysis correcting for differences in age, cumulative work and cholesterol level revealed a significant correlation between LVMI and SBP at rest (t = 4.07, P less than 0.0001) and during exercise (t = 3.25, P = 0.002). Thus in patients with established, moderate hypertension exercise SBP is not more predictable for LVMI than is SBP at rest.

Adult↗
PubMed1990

Is left ventricular mass in apparently healthy, normotensive men correlated to maximal blood pressure during exercise?

In 95 apparently healthy normotensive men aged 21-69 (mean 44) years with supine blood pressure (BP) less than 150/90 mmHg when less than 50 years, and less than 160/95 when greater than or equal to 50 years of age, left ventricular mass (LVM) was measured by M-mode echocardiography and related to maximal BP during a symptom-limited ergometer bicycle test. Mean LVM was 195 (+/- 43) g and LVM index (I) 101 (+/- 20) g m-2 body surface area (BSA). The subjects were subdivided into two groups: Group 1 = 28 subjects (29%) with LVM greater than or equal to 220 g, and Group 2 = 67 subjects (71%) with LVM less than 220 g. Group 1 had a slightly larger BSA (P less than 0.05), weight (P less than 0.05) and resting systolic BP (P less than 0.05). A higher prevalence of smokers (P less than 0.01) and serum cholesterol levels (P less than 0.05) were also noted among Group 1 subjects, who had a higher maximal systolic BP during exercise (P less than 0.0001). Using linear regression analysis, significant positive correlations were observed between LVM and systolic BP at rest (r = 0.20, P less than 0.05), and maximal exercise systolic BP (r = 0.32, P less than 0.001). When correcting for differences in age, weight, body surface area, physical performance, smoking and hours of exercise per week, multiple regression analysis revealed a significant between LVM and maximal systolic BP (t = 2.38, P = 0.020, Partial F = 5.64).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Blood pressure response during maximal exercise in apparently healthy men and women.

The blood pressure (BP) response during a maximal ergometer bicycle test was studied in 190 apparently healthy subjects (95 men and 95 women) aged 21-70 years. The starting load was 50 W and was increased by 50 W every 4 min until exhaustion. Mean physical performance expressed as cumulative work was 2276 +/- 789 W in men and 1109 +/- 276 W in women (P less than 0.0001). The maximum heart rate was similar in men and women and declined significantly with age (r = -0.78, P less than 0.001 for men and r = -0.64, P less than 0.0001 for women). The mean maximal systolic blood pressure (MSBP) was 193 +/- 23 mmHg in men and 171 +/- 21 mmHg in women (P less than 0.0001). Men aged greater than or equal to 50 years had a MSBP of 201 +/- 22 mmHg, compared to 188 +/- 22 mmHg in those aged less than 50 years (P less than 0.01). Women aged greater than or equal to 60 years had a MSBP of 190 +/- 21 mmHg compared to 166 +/- 19 mmHg in their younger counterparts (P less than 0.001). The diastolic BP showed a similar modest increase at all ages and in both sexes. SBP is dependent on age and gender and this must be taken into consideration when assessing a normal response in individual patients.

Adult↗