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Biomedical subjects

J K Thomsen

Publications and source records attributed to J K Thomsen.

At least 19 recordsLinked to original sources
PubMed2005

Use of a hydrocapillary dressing in the management of highly exuding ulcers: a comparative study.

OBJECTIVE: To evaluate the safety and performance of Alione Hydrocapillary dressing (Coloplast A/S) in the management of highly exuding chronic venous leg ulcers and compare it with two hydropolymer dressings,Tielle and Tielle Plus (Johnson & Johnson). METHOD: A comparative clinical trial was conducted on 97 patients with an ankle brachial pressure index > or = 0.8 and a highly exuding leg ulcer. Ulcer duration was at least four weeks. Treatment continued until healing or for a maximum of 12 months. RESULTS: There was no statistically significant difference in healing time or wound area reduction between the two treatment protocols. The test dressing (Alione Hydrocapillary) had better absorption capacity and was more comfortable for the patients than the comparator dressings (Tielle/Tielle Plus) and adhered less to the wound bed.Also, more patients preferred the test dressing to their previous treatment. Although severe leakage and maceration were observed more frequently in the comparator group compared with the test group, this was not statistically significant. CONCLUSION: Both treatment protocols were safe and effective in treating highly exuding chronic venous leg ulcers. The test dressing performed as well as or better than the comparator dressings for all study parameters and more patients preferred the test dressing to their previous dressing compared with the comparator dressings.

Adult↗
PubMed2004

Safety and performance of a new non-adhesive foam dressing for the treatment of diabetic foot ulcers.

OBJECTIVE: This study aimed to document the safety and performance of a new non-adhesive foam dressing (Biatain Non-adhesive Dressing, Coloplast A/S) in the treatment of established foot ulcers in patients with diabetes. METHOD: This was an open non-comparative prospective study. Participants had an ankle brachial pressure index score of over 0.4 (neuro-ischaemic) and an ulcer bigger than 1 cm2 and less than 8 cm2 in any direction. The treatment period was six weeks. RESULTS: Thirty-five out of 37 patients completed the study. The mean wound area reduced from 5.4 cm2 to 2.5 cm2. Relative wound area reduced from 100% at baseline to 40% at week 6. 'Wearing comfort' improved throughout the study (p = 0.039). Maceration remained stable or improved. None of the four reported adverse events were device related. CONCLUSION: This study demonstrates that treatment of diabetic foot ulcers with Biatain Non-adhesive Dressing results in considerable wound area reduction and prevents any deterioration in maceration. The dressing is safe and effective in the management of these ulcers.

Activities of Daily Living↗
PubMed2001

Conformation of alamethicin in oriented phospholipid bilayers determined by (15)N solid-state nuclear magnetic resonance.

The conformation of the 20-residue antibiotic ionophore alamethicin in macroscopically oriented phospholipid bilayers has been studied using (15)N solid-state nuclear magnetic resonance (NMR) spectroscopy in combination with molecular modeling and molecular dynamics simulations. Differently (15)N-labeled variants of alamethicin and an analog with three of the alpha-amino-isobutyric acid residues replaced by alanines have been investigated to establish experimental structural constraints and determine the orientation of alamethicin in hydrated phospholipid (dimyristoylphosphatidylcholine) bilayers and to investigate the potential for a major kink in the region of the central Pro(14) residue. From the anisotropic (15)N chemical shifts and (1)H-(15)N dipolar couplings determined for alamethicin with (15)N-labeling on the Ala(6), Val(9), and Val(15) residues and incorporated into phospholipid bilayer with a peptide:lipid molar ratio of 1:8, we deduce that alamethicin has a largely linear alpha-helical structure spanning the membrane with the molecular axis tilted by 10-20 degrees relative to the bilayer normal. In particular, we find compatibility with a straight alpha-helix tilted by 17 degrees and a slightly kinked molecular dynamics structure tilted by 11 degrees relative to the bilayer normal. In contrast, the structural constraints derived by solid-state NMR appear not to be compatible with any of several model structures crossing the membrane with vanishing tilt angle or the earlier reported x-ray diffraction structure (Fox and Richards, Nature. 300:325-330, 1982). The solid-state NMR-compatible structures may support the formation of a left-handed and parallel multimeric ion channel.

Alamethicin↗
PubMed2000

Solid-state 13 C and 31 P NMR analysis of urinary stones.

PURPOSE: We investigated the applicability of solid-state nuclear magnetic resonance (NMR) spectroscopy to obtain information about the structure and composition of renal calculi. MATERIALS AND METHODS: Various types urinary and bladder stones as well as a variety of presumed constituents were investigated using 13C and 31P magic-angle spinning (MAS) solid-state NMR. Different experimental methods were applied to differentiate resonances from crystalline/amorphous (immobile/mobile) as well as protonated/non-protonated moieties. The NMR spectra were analyzed using multiple-component numerical simulations and iterative fitting to identify and quantify the major amorphous or crystalline organic and inorganic components. RESULTS: By comparison of the NMR spectra for the various renal calculi with those obtained under similar conditions for various presumed components, it is demonstrated possible to unambiguously distinguish and quantify the major amorphous or crystalline organic and inorganic components. The components are identified in terms of their isotropic and anisotropic chemical shielding parameters, protonation or proximity of protons, and the degree of crystallinity/mobility. For the calculi investigated we have detected and quantified calcium oxalate, uric acid, struvite, and calcium phosphates that closely resemble brushite and calcium hydroxyapatite. CONCLUSIONS: Using 13C and 31P MAS NMR spectroscopy we have been able to account for 60 to 85% (by weight) of the constituents in the calculi investigated. The ability to identify and quantify both crystalline and amorphous components makes solid-state NMR an interesting new method for the compositional analysis of renal calculi.

Calcium Oxalate↗
PubMed1997

Prevalence of carcinoma in situ of the testis in 207 oligozoospermic men from infertile couples: prospective study of testicular biopsies.

OBJECTIVE: To investigate the prevalence of carcinoma in situ of the testis in a group of oligozoospermic men from infertile couples. DESIGN: A consecutive group of oligozoospermic men from infertile couples were offered bilateral testicular biopsy. The observed prevalence of carcinoma in situ was compared with the expected prevalence of testicular cancer in a corresponding age matched population of Danish men, assuming all untreated cases of carcinoma in situ progress to tumour stage. This calculation was based on data from the Danish Cancer Registry. SUBJECTS: 207 men aged 18-50 years who had sperm density below 10 million/ml in two samples within the previous 2 years or sperm density below 20 million/ml in two samples within the previous 2 years and a history of cryptorchidism or one or two atrophic testicles (orchidometer volume less than 15 cm3), or both. INTERVENTIONS: Bilateral testicular biopsies. MAIN OUTCOME MEASURES: Carcinoma in situ in the biopsy specimen. RESULTS: No case of carcinoma in situ was found among the 207 men. The expected number in a normal age matched population of corresponding size was 0.8. CONCLUSIONS: There is no increase in risk of carcinoma in situ of the testis in moderately oligozoospermic men of couples referred because of infertility.

Adolescent↗
PubMed1997

Characterization of phosphate sites in native ovine, caprine, and bovine casein micelles and their caseinomacropeptides: a solid-state phosphorus-31 nuclear magnetic resonance and sequence and mass spectrometric study.

The phosphate sites in native ovine, caprine, and bovine casein micelles have been analyzed using sequence analysis, mass spectrometric analysis, and solid-state 31P nuclear magnetic resonance spectroscopy. Using a combination of S-ethylcysteine derivatization, sequence analysis, and mass spectrometric analysis, the phosphorylation sites of ovine (SerP151 and SerP168), caprine (SerP151 and SerP168), and bovine (SerP149) caseinomacropeptides have been localized. Various solid-state 31P methods using magic angle spinning have been applied to ascertain the local structure and dynamics of the phosphorylated serine residues and the inorganic calcium phosphates within the micelles. Contributions from the phosphorylated serine residues of kappa-CN, located in the C-terminal portion of the molecule, to the mobile constituents of the micelles were assigned by comparison with 31P nuclear magnetic resonance spectra of purified caseinomacropeptides from the various species in the dissolved state. Comparison of the 31P magic angle spinning nuclear magnetic resonance spectra of ovine, caprine, and bovine casein micelles indicates that the micelles from these species are very similar but not identical.

Amino Acid Sequence↗
PubMed1995

Solid-state magic-angle spinning 31P-NMR studies of native casein micelles.

Solid-state magic-angle spinning 31P-NMR spectroscopy was used to characterize the structure and composition of native casein micelles. The features of the magic-angle spinning 31P-NMR spectra, including overlapping resonances from mobile/immobile phosphorylated serine residues and inorganic calcium phosphates, have been determined using different experimental techniques and assigned by comparison with spectra of the presumed constituents within the casein micelle. Comparison with 31P-NMR spectra of alpha s1-, alpha s2-, and beta-caseins in dissolved and freeze-dried forms demonstrated that a major fraction of the phosphoserines in these proteins was in an immobilized state within the micelle. Likewise, from 31P-NMR spectra of the C-terminal part of kappa-casein, it was shown that this region of the micelle has a considerable conformational mobility. Finally, magic-angle spinning 31P-NMR spectra for a series of inorganic calcium phosphates and mineralized bone tissue revealed that the micellar inorganic calcium phosphates exhibit structural similarities to hydroxyapatite and hence resemble mineralized bone tissue.

Caseins↗
PubMed1995

Comparison of cardiac output measurement techniques: thermodilution, Doppler, CO2-rebreathing and the direct Fick method.

Simultaneously measured cardiac output obtained by thermodilution (TD), transcutaneous suprasternal ultrasonic Doppler (DOP), CO2-rebreathing (CR) and the direct Fick method (FI) were compared in eleven healthy subjects in a supine position (SU), a sitting position (SI), and during sitting exercise at a workload of 50 W (EX). The agreements between the techniques, two by two, were expressed as the bias calculated as the averaged differences between the techniques. Precision was expressed as the standard deviation of the bias. The overall agreement (bias +/- precision) between TD, DOP and CR respectively and FI were 2.3 +/- 1.6, -0.1 +/- 1.4, and -0.2 +/- 1.1 l/min. TD overestimated cardiac output consistently in SU, SI and EX. DOP was in-accurate during EX and agreed well with FI in SU and SI. CR agreed closely with FI in SI and EX, but values were underestimated in SU. The overall agreement between DOP and CR, respectively, and TD were 2.5 +/- 2.2 and 2.6 +/- 1.6 l/min. The overall agreement between DOP and CR was 0.1 +/- 1.6 l/min. In conclusion, TD overestimated cardiac output compared to the other techniques and the poor agreement has to be taken into consideration especially in measures of low values. The precision of DOP and CR against FI seems to be within clinically acceptable limits, and these methods may provide interchangeable alternatives to the invasive Fick method.

Adult↗
PubMed1994

Ultrasonic texture and volume of testicles in infertile men.

Ultrasound scanning of the testes and surgical biopsy were performed in 95 infertile men to evaluate the use of ultrasound in male infertility. Ultrasonic testicular volume was calculated using three measurements and the formula of an ellipsoid, and the ultrasonic texture was evaluated and given a score from 1 to 5, indicating increasing degrees of irregularity. The median score was 3 (range 1-5), which was higher than previously found in normal men (median score 2; range 1-5; P < 0.0001). The ultrasonic texture score was lower in testes with a uniform pattern of 100% spermatogenic tubules compared with the rest, both for the right (P < 0.001) and for the left (P < 0.0005) testis. Texture score was correlated with the number of obliterated tubules for both testes (P < 0.001). The mean ultrasonic testicular volume of the right testis was 10.30 ml, and that of the left 10.26 ml. Both were smaller compared with the findings in normal men (P < 0.0001). Ultrasonic testicular volume was negatively correlated with texture score (P < 0.001). A positive correlation between ultrasonic volume and sperm count was seen (P < 0.001). Sperm count was negatively correlated with texture score if calculated together with data from 119 men from the general population (P < 0.001). The study shows that ultrasonic volume and texture are valuable parameters in the evaluation of infertile men.

Adult↗
PubMed1994

Effects of acute beta-adrenoceptor blockade with metoprolol on the renal response to dopamine in normal humans.

The present study investigated the contribution of adrenergic beta 1-receptor stimulation to the cardiovascular and renal effects of low-dose dopamine in eight normal, water-loaded humans. Metoprolol (100 mg) or placebo was administered orally at 08.00 h in a randomized, double-blind fashion on two different days. Renal clearance studies were performed during a 1 h baseline period, two 1 h periods with dopamine infusion (3 micrograms kg-1 min-1), and a 1 h recovery period. Cardiac output was measured by an ultrasonic Doppler method, and lithium clearance (CLLi) was used to estimate proximal tubular outflow. Baseline values of heart rate, systolic pressure and mean arterial pressure decreased with metoprolol compared with placebo, but cardiac output, effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were not significantly changed. Metoprolol significantly decreased baseline CLLi and sodium clearance (CLNa) by 19% (P < 0.01) and 34% (P < 0.01), respectively. Metoprolol blunted the dopamine-induced increases in heart rate and systolic pressure, but cardiac output increased to the same extent on both study days by 26% (placebo, P < 0.05) and by 31% (metoprolol, P < 0.01), respectively. With and without metoprolol, dopamine did not significantly change GFR, and the percentage increases in ERPF were similar on the two study days (40% (P < 0.001) and 42% (P < 0.001), respectively). Dopamine increased CLLi and CLNa by 31% (P < 0.01) and 114% (P < 0.01), respectively, with placebo, and by 36% (P < 0.01) and 114% (P < 0.01), respectively, with metoprolol. Values during infusion remained significantly lower with metoprolol compared with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Mass Spectrometric Studies of the Effect of pH on the Accumulation of Intermediates in Denitrification by Paracoccus denitrificans.

We have used a quadrupole mass spectrometer with a gas-permeable membrane inlet for continuous measurements of the production of N(2)O and N(2) from nitrate or nitrite by cell suspensions of Paracoccus denitrificans. The use of nitrate and nitrite labeled with N was shown to simplify the interpretation of the results when these gases were measured. This approach was used to study the effect of pH on the production of denitrification intermediates from nitrate and nitrite under anoxic conditions. The kinetic patterns observed were quite different at acidic and alkaline pH values. At pH 5.5, first nitrate was converted to nitrite, then nitrite was converted to N(2)O, and finally N(2)O was converted to N(2). At pH 8.5, nitrate was converted directly to N(2), and the intermediates accumulated to only low steady-state concentrations. The sequential usage of nitrate, nitrite, and nitrous oxide observed at pH 5.5 was simulated by using a kinetic model of a branched electron transport chain in which alternative terminal reductases compete for a common reductant.

Journal Article↗
PubMed1994

Atrial natriuretic peptide, blood volume, aldosterone, and sodium excretion during twin pregnancy.

BACKGROUND: The reports on plasma concentrations and physiological function of atrial natriuretic peptide (ANP) during pregnancy are conflicting. In a recent prospective study, including 40 healthy primigravidae, we found a highly significant decrease in the plasma concentration of ANP (p-ANP) during the third trimester and the results indicated that ANP takes part in regulation of blood volume and renal function during pregnancy as in the nonpregnant state. In order to test these results, a study was performed in primigravidae with twin pregnancy to test if the accentuated physiological changes here were followed by a corresponding greater decrease in p-ANP. METHODS: Ten healthy primigravidae with twin pregnancy were examined four times during pregnancy plus 12 weeks after delivery. Each time the following were measured: p-ANP, aldosterone, renin, blood volume (carbon monoxide), cardiac output (Doppler), blood pressure and sodium excretion. Interdependence of the changes in ANP and in the other parameters was tested using Spearman's rank correlation test on the delta (delta)-values (the differences in measurements between investigations). The results were compared to the results obtained during singleton pregnancy using the Mann-Whitney rank sum test. RESULTS: All pregnant values of p-ANP during twin pregnancy were lower than 12 weeks after delivery, p < 0.01. In the 20th, 28th, and 32nd week p-ANP was lower in twin pregnancy than in singleton pregnancy, p < 0.05. There was a negative correlation between changes in p-ANP and changes in: a) blood volume, R = -0.8, p < 0.0001, b) aldosterone, R = -0.66, p < 0.0001, c) renin, R = -0.52, p < 0.01, d) cardiac output, R = -0.68, p < 0.0001. There was a positive correlation between changes in p-ANP and changes in: a) fractional excretion of sodium, R = 0.73, p < 0.0001, and b) total peripheral resistance, R = 0.61, p < 0.0001. CONCLUSION: The results suggest that the competitive relationship between ANP and the renin-aldosterone system in regulating sodium balance and fluid volume is preserved during pregnancy. The vasodilation during pregnancy is not mediated by ANP.

Aldosterone↗
PubMed1993

Low dose iron supplementation does not cover the need for iron during pregnancy.

OBJECTIVE: To determine: 1) if 18 mg iron daily is sufficient to cover the iron need during normal pregnancy, and 2) if women, who will not need iron supplementation during pregnancy, can be identified by early screening. DESIGN: In a prospective study the women were randomized to receive either 18 or 100 mg iron daily from the 16th week until delivery. Investigations were performed in the 16th, 30th, and 38th week. SUBJECTS: Healthy nulliparae (n = 43) experiencing a normal singleton pregnancy. Only women with a normal hemoglobin concentration and intact iron stores (S-Ferritin > 15 micrograms/1) in the 16th week were included. VARIABLES: These measurements were done consecutively: 1) the total hemoglobin mass (with carbon monoxide). 2) S-Ferritin, 3) S-Transferrin, 4) S-Iron, 5) red cell indices (hemoglobin concentration, hematocrit, MCV, MCHC). RESULTS: Changes in red cell indices and S-Transferrin were equal in the two groups. There was no significant difference in S-Ferritin in the 16th week. In the 30th week 3 women (14%) in the 100 mg group and 11 (52%) in the 18 mg group had empty iron stores (p < 0.05). The numbers were 1 (5%) and 15 (72%) in the 38th week (p < 0.0001). The increment in total hemoglobin mass was equal in the two groups from the 16th to the 30th week (13% in the 100 mg group and 12% in the 18 mg group). From the 30th to the 38th week the increment in total hemoglobin mass was largest in the 100 mg group (8.1% versus 2.7%, p < 0.05). CONCLUSION: Despite a normal hemoglobin concentration and intact iron stores in the 16th week, an iron supplementation of 18 mg daily is not sufficient to cover the iron need in many pregnant women in the 3rd trimester.

Adult↗
PubMed1993

Atrial natriuretic peptide (ANP) decrease during normal pregnancy as related to hemodynamic changes and volume regulation.

BACKGROUND: Volume regulation and hemodynamic functions change during pregnancy, leading to marked increases in blood volume and cardiac output, peripheral vasodilatation and reduced sensitivity to angiotensin. Atrial natriuretic peptide (ANP) is intimately involved in fluid and sodium homeostasis and exerts marked relaxant activity on vascular smooth muscle pre-contracted with angiotensin. This study was performed to clarify the role of ANP as a regulator of maternal physiology. METHODS: 40 normal primigravidae were examined five times during pregnancy plus 12 weeks after delivery. Each time were measured: ANP, aldosterone, renin, blood volume (carbon monoxide), cardiac output (Doppler), blood pressure and sodium excretion. Interdependence of the changes in ANP and in the other parameters was tested using Spearman's rank correlation test on the delta (delta)-values (the differences between investigations). RESULTS: P-ANP in the 20th week was 11.4 (8.5-18.9) pmol.l-1 (median, 25 and 75 percentiles), the same as 12 weeks after delivery, 11.5 (9.6-15.2) pmol.l-1, and in a non-pregnant control group, 10.4 (9.0-12.5) pmol.l-1 (n = 20). All measurements of P-ANP during the 3rd trimester were lower than in the 20th week and 12 weeks after delivery, p < 0.0001 (Wilcoxon matched-pairs test). There was a negative correlation between changes in P-ANP and changes in: a) blood volume. R = 0.69, p < 0.0001, b) aldosterone, R = 0.58, p < 0.0001, c) renin, R = -0.54, p < 0.001, d) cardiac output, R = 0.61, p < 0.001. There was a positive correlation between changes in P-ANP and changes in: a) fractional excretion of sodium, R = 0.54, p < 0.0001, and b) total peripheral resistance. R = 0.52, p < 0.0001. CONCLUSION: Decrease in p-ANP is one of the mechanisms whereby blood volume is increased and maintained during pregnancy. The competitive relationship between ANP and the renin aldosterone system in regulating sodium balance and fluid volume is preserved during pregnancy. The results substantiate the physiological importance of ANP as a regulator of blood volume. ANP does not function as a vasodilator during pregnancy.

Adolescent↗
PubMed1991

Blood and plasma volumes determined by carbon monoxide gas, 99mTc-labelled erythrocytes, 125I-albumin and the T 1824 technique.

The total amount of circulating haemoglobin was measured in 12 subjects using a direct carbon monoxide (CO)-technique. O2 plus 50 ml CO gas was rebreathed in a small closed system for 10 min. Carboxyhaemoglobin (HbCO)% was measured with a diode-array spectrophotometer before and after the rebreathing. delta HBCO% and the amount of CO in moles (nCO) were used to calculate the total amount of circulating haemoglobin. Blood volume was calculated by dividing this figure with the haemoglobin concentration and plasma volume by multiplying the blood volume with 1-haematocrit. The calculated blood and plasma volumes were compared with the simultaneously measured volumes by 99mTc-labelled erythrocytes, 125I-albumin and T 1824 (Evans Blue). Mean blood volume determined with CO was 4557 ml (3251-6576 ml) compared with 4527 ml (3390-6527 ml) with 99mTc-labelled erythrocytes (r = 0.97). Mean plasma volume by T 1824 was 2895 ml (1972-3658 ml) vs 2898 ml (1815-3714) ml using 125I-albumin, (r = 0.99). The plasma volumes calculated from the blood volumes determined by the erythrocyte-labelling methods were 5-10% lower than those measured with labelled albumin. There was a better correlation between the plasma volumes by the albumin methods and by the CO-technique (r = 0.98 and r = 0.97, respectively) than between the plasma volumes by the albumin methods and by 99mTc-erythrocytes (r = 0.90 and r = 0.87, respectively).

Aged↗
PubMed1990

pH effect on the COHb absorption spectrum: importance for calibration of the OSM3 and measurement of circulating hemoglobin and blood volume.

An easy method to measure blood volume is clinically needed. We used carbon monoxide (CO) and the OSM3 to measure circulating hemoglobin and blood volume with the indicator dilution principle. 50 mL of CO was administered into a closed rebreathing system and taken up via the lungs, and the amount of hemoglobin in the blood was calculated from the increase in carboxyhemoglobin fraction after 10 min. Blood volume was calculated by division with the concentration of hemoglobin. We observed that the absorption spectrum of carboxyhemoglobin (COHb) depends on pH and pCO2, which must be controlled when very accurate spectrophotometry is necessary. The bias is 3% COHb per pH unit during calibration of the OSM3, which may be permissible for patients with CO poisoning, but not for the present purpose. With this in mind the method is very accurate, precise and simple.

Blood Volume↗