Analysis of bovine lactoferrin in whey using capillary electrophoresis (CE) and micellar electrokinetic chromatography (MEKC).
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Animals↗
Biomedical subjects
T Weiss
Publications and source records attributed to T Weiss.
Brain electrical correlates of pain processing.
Pain is the result of complex neuronal activities within the brain and not simply the result of peripheral activities of the nociceptive system. Pain results from an interaction of many neuronal modules located in different brain areas. This interaction is modified by anticipation, learning, and perception. Electrophysiological phenomena allow the characterization of the information processing associated with pain. This characterization is important for theoretical purposes and for the evaluation of different therapeutic strategies. Furthermore, electrophysiological phenomena support the investigation of functional plasticity in the brain as one of the consequences of chronic pain processing. It is expected that new methods of cortical source analysis will contribute considerably to our understanding of different aspects of pain processing and of the management of pain.
Animals↗
[Starling resister and stability of sleep ventilation].
The upper airway can be described as a collapsible segment (the pharynx) interposed between two rigid bony (the cavum) or cartilaginous (the trachea) segments. Due to this structure, the pharynx behaves as a collapsible tube, in which airflow does not depend on the downstream pressure, but is limited to a maximum value which depends only on the upstream pressure and on the pressure surrounding the collapsible segment; this behavior, known as a Starling resistor can be modeled by the waterfall effect. Thus, the upper airways can be in three different conditions: an occluded condition, in which no flow is possible, a patent condition, in which flow depends on the difference between upstream and downstream pressures (according to Poiseuille's law), and a situation in which flow is limited. The behavior of the upper airway is largely dependent on its anatomic structure, but functional factors play a critical role. Among these sleep state is both a determinant of the collapsibility of the pharynx, and determined by the simulation of upper airway mechanoreceptors whose activity depends on the activity of respiratory muscles. Thus the interplay of three factors: ventilatory drive, upper airway collapsibility, and arousal threshold can predict most of the situations of stable and unstable ventilatory behavior during sleep. The level of the arousal threshold governs the stability of the ventilatory pattern, as it determines whether a combination of slow, respiratory effort, and blood gases can be maintained or is interrupted by an arousal.
Airway Resistance↗
Acute effects of haemodialysis on cutaneous microcirculation in patients with peripheral arterial occlusive disease.
BACKGROUND: Peripheral arterial occlusive disease (PAOD) is an increasing problem in patients on maintenance haemodialysis. Alterations in microvascular perfusion accompany and complicate arteriosclerosis of large vessels and might contribute to the disease process. The aim of the study was to investigate the acute effects of haemodialysis on the cutaneous microcirculation in 26 patients with and without intermittent claudication. METHODS: Cutaneous perfusion was assessed by measuring transcutaneous oxygen pressure (tcPO2) and skin temperature at the dorsum of the foot. After standardized cooling to 15 degrees C of a 2cm2 skin area, the time to reach baseline skin temperature was evaluated as an indirect parameter of reactive hyperaemia. RESULTS: During haemodialysis, tcPO2 dropped significantly in both groups. The decrease in tcPO2 was more pronounced in patients with PAOD (20% vs 15% n.s.). The reactive hyperaemia response was reduced significantly in patients with intermittent claudication indicated by a prolonged time to reach baseline skin temperature after cooling. Values of tcPO2 and reactive hyperaemia did not reach baseline values at the end of haemodialysis in either group. CONCLUSIONS: Nutritive skin perfusion is impaired during haemodialysis. These changes are more pronounced in patients with PAOD and persist after dialysis. These findings are relevant for the treatment of patients with vascular disease on maintenance haemodialysis.
Adult↗
The use of improved radiochromic film for in vivo quality assurance of high dose rate brachytherapy.
GAFChromic film has become increasingly popular for radiation dosimetry. In this study we explore the use of GAFChromic film as an in vivo dosimeter for quality assurance (QA) of fractionated high dose rate 192Ir treatments. Accuracy of dose distribution is explored for the simple vaginal cylinder geometry for which the dose can be easily calculated for comparison. Source dwell times for several patients were optimized to deliver 500 cGy at 0.5 cm from the surface of the vaginal cylinder applicator using a commercial treatment planning system. GAFChromic film was taped to the vaginal cylinder applicator and was enclosed in a leak proof rubber sleeve prior to its insertion. Optical densities were measured along the film at 2 mm spacing, using a densitometer with filtered red light. Density corrections for transient film darkening effects were made and optical densities were converted to absorbed dose in cGy. In vivo patient dose distribution measured for different patients and different fractions were compared with the calculated values along the applicator surface. The variation between the calculated and measured dose was +/- 10%. the reproducibility of dose measurement for different fraction was within +/- 5%. This study demonstrates the potential usefulness of the film as an in vivo for brachytherapy QA.
Administration, Intravaginal↗
Is urodilatin the missing link in exercise-dependent renal sodium retention?
The purpose of the present study was to investigate the behavior of plasma atrial natriuretic peptide [ANP-(99-126)] concentration ([ANP]) and renal urodilatin [Uro; ANP-(95-126)] excretion during and after exercise and their possible effects on renal Na+ retention. Ten male subjects performed a cycle ergometer test for 60 min at 60% of maximum workload. Blood and urine samples were collected before, during, and up to 24 h after exercise. During exercise, plasma [ANP] and renal Uro excretion were oppositely affected: whereas [ANP] increased from 46.5 +/- 5.1 to 124.1 +/- 10.6 pg/ml, urinary Uro excretion decreased from 120.8 +/- 16.0 to 49.5 +/- 9.8 fmol/min and remained at a lower level until 1 h after exercise. Glomerular filtration rate showed lowest values during exercise (from 164.9 +/- 15.3 to 75.8 +/- 10.1 ml/min), and urine flow and the fractional excretion rate of Na+ (FENa+) and Cl- (FECl-) had their nadir during the first hour after exercise. Positive relationships were observed between Uro excretion and FENa+ (P < 0.05) and FECl-, whereas a tendency toward a negative correlation was obtained between [ANP] and FENa+. It seems possible that Uro may be, among other factors, involved in the exercise-related regulation of renal Na+ retention. The specific roles Uro and ANP play during exercise, however, remain to be investigated.
Adult↗
Neutrophil function in peripheral arterial occlusive disease: the effects of prostaglandin E1.
The role of polymorph nuclear neutrophils (PMN) in limb ischemia and reperfusion has been recognized only in recent years. The present study aimed to investigate the systemic and local (in femoral venous blood) effects of intra-arterially or intravenously applied prostaglandin E1 (PGE1) on systemic and ischemia-induced local changes in neutrophil function. Thirty patients with intermittent claudication were randomly assigned to intra-arterial or intravenous infusion of prostaglandin E1 (10 microg i.a. or 15 microg i.v. over 30 min). Prior to infusion femoral arterial and venous blood samples were obtained from the predominantly affected leg under resting conditions and immediately after a 3-min period of ischemia induced by suprasystolic thigh compression. After 24 h additional blood samples were obtained at baseline, following infusion of prostaglandin E1, and again after another 3-min period of ischemia following the prostaglandin E1 infusion. Intra-arterially administered prostaglandin E1 caused an increase in the PMN count by 3.5 +/- 2% (p<0.05) and a decrease in free oxygen radical production by 13 +/- 8% (p<0.05) measured by whole blood chemiluminescence. Additionally, a trend for lower PMN filterabilities (9 +/- 12%, NS) was observed. Intra-arterially infused prostaglandin E1 significantly reduced the ischemia-induced decrease in neutrophil filterability (arterial and venous blood difference after ischemia -- control: 22 +/- 17% (p<0.05); IA PGE1: 8 +/- 11% (NS), each compared to baseline). Intravenously administered prostaglandin E1 showed similar systemic effects as the intra-arterial application, but did not affect the ischemia-induced changes in neutrophil filterability. In conclusion, prostaglandin E1 reduces PMN activation in patients with peripheral arterial occlusive disease.
Aged↗
Simplified diagnostic procedure for obstructive sleep apnoea syndrome: lower subsequent compliance with CPAP.
The aim of this study was to investigate whether a simplified diagnostic procedure based on ambulatory monitoring with MESAM IV altered subsequent compliance with continuous positive airway pressure (CPAP) in obstructive sleep apnoea (OSA) patients. During a period of 16 months, 60 patients with symptoms evocative of OSA and positive MESAM recording were prescribed CPAP after titration with standard polysomnography. Compliance was followed during 2 yrs based on built-in time counters and was compared with the compliance in two comparison groups: an equal number of equally severely affected patients diagnosed with standard polysomnography during the 18 months (8 months before and 8 months after) preceding and following the study period and a group of 48 patients with an estimated similar apnoea/hypopnoea index but less typical clinical and/or MESAM features, diagnosed as having OSA based on polysomnography during the study period. The three groups were not different by age, body mass index, or sleepiness score. Patients diagnosed with the ambulatory procedure had higher drop-out rates (21.7% versus 10% and 6.25%; p<0.05) and lower rates of use of their CPAP (43+/-0.3 h x night(-1)) than any of the control groups (53+/-0.2 and 5.6+/-0.2 h x night(-1), p<0.05). In conclusion, there is a risk that ambulatory diagnostic procedures alter the relationship of patients to their disease and/or the medical staff so that subsequent compliance with treatment may be decreased. The greatest care concerning compliance should be taken before an ambulatory-based diagnostic procedure is implemented.
Ambulatory Care↗
[Fully implantable in vivo microdialysis system for glucose monitoring. Total system concept and implantable prototype system].
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Blood Glucose Self-Monitoring↗
A bioadaptive approach for experimental pain research in humans using laser-evoked brain potentials.
In order to find an experimental approach counteracting habituation in experimental pain research using short infrared laser stimulation in humans we developed a bioadaptive method based on subject's report on painfulness of stimulation (pain report; PR). After determination of the initial relationship between the energy of the laser stimulus and the corresponding PRs, the approach continuously adjusts the intensity of noxious stimuli so that PR is kept constant across time. Each difference between the PR evoked by the actual laser stimulus and the desired PR leads to an increase or decrease of the laser output energy value for the next stimulation with the desired PR proportional to the PR difference as well as to the slope of the initial correlation function between laser energy and corresponding PRs. This method has been applied in a study with nine volunteers. Results show that the approach leads to a constant PR by increasing the laser output energy by 0.01 mJ/s per mm2 on the average. Furthermore, an analysis of the laser-evoked brain potentials (LEPs) recorded from Cz was performed for the first and second half of stimuli. However, no significant changes in latencies or amplitudes of the main LEP components recorded at 210 ms (N210) and 350 ms (P350) were found. The method seems to be useful for different approaches in experimental and clinical pain research.
Adult↗
High-resolution reversed-phase high-performance liquid chromatography analysis of polyamines and their monoacetyl conjugates by fluorescence detection after derivatization with N-hydroxysuccinimidyl 6-quinolinyl carbamate.
A highly sensitive, accurate, and reproducible HPLC method for the determination of all natural polyamines and their monoacetyl conjugates is described. The presented method is based on precolumn derivatization with N-hydroxysuccinimidyl 6-quinolinyl carbamate (HSQC) followed by C18-HPLC separation using a ternary gradient and fluorescence detection (lambda Ex = 248 nm, lambda Em = 398 nm). The derivatives of the four main polyamines (putrescine, cadaverine, spermidine, and spermine) and the internal standard were synthesized on a preparative scale and characterized, especially with respect to their molar absorptivities and fluorescence quantum yields. The limits of detection of the highly stable derivatives ranged from 30 to 130 fmol (injection volume 10 microliters) for putrescine and N-acetylcadaverine, respectively (signal to noise ratio = 10), with excellent linearity within the range from 1 to 100 microM. High reproducibility for both retention times and peak areas, with coefficients of variation ranging from 0.14 to 0.88% and from 1.83 to 3.80%, respectively, were achieved. Provided that deproteinization of the samples was carried out immediately, recoveries of the analytes from homogenates of pancreatic cancer xenografts were high and reproducible. The optimized method was applied to the determination of the polyamine content of cultured pancreatic cancer cells and of tissue from colorectal adenocarcinoma, proving precise and reproducible quantification in these complex biological matrices.
Acetylation↗
Enhancement of TNF receptor p60-mediated cytotoxicity by TNF receptor p80: requirement of the TNF receptor-associated factor-2 binding site.
TNFR p60 (TNFR60) is the main mediator of TNF-induced apoptosis, although in some cells TNFR80 is also involved. TNFR80-dependent induction or enhancement of cytotoxicity has been explained by intracellular signaling, "ligand passing," or induction of endogenous TNF. Using HeLa transfectants expressing wild-type TNFR80 and deletion mutants derived from them, we have investigated the mechanism of TNFR80-mediated cytotoxicity. TNFR80 induces no cytotoxicity on its own, but is functional in these transfectants, as selective stimulation activates nuclear factor-kappaB (NF-kappaB) and induces NF-kappaB-dependent cellular responses (IL-6 and manganese superoxide dismutase). TNFR60-induced cytotoxicity, however, is enhanced about 1000-fold by costimulation of TNFR80, whereas only additive responses are observed with regard to NF-kappaB-dependent responses. Ligand passing is not critically involved, because a similar potentiation of TNFR60-mediated cytotoxicity was observed when agonistic Abs were used for stimulation of both receptors. In addition, in HeLa cells overexpressing a truncated form of TNFR80 lacking the cytoplasmic domain, no TNFR80-dependent potentiation of TNFR60-mediated cytotoxicity was detectable, emphasizing that intracellular signaling of TNFR80 is required for synergistic activity. The involvement of endogenously produced TNF can be ruled out by the use of TNF-neutralizing Abs. The ability of TNFR80 to cooperate with TNFR60 could be mapped to the binding site for the TNF receptor-associated factor-2. These results are in agreement with a differential cooperation of both TNFR; an additive effect is obtained in those responses that are initiated by both receptors via identical pathways, i.e., activation of NF-kappaB, whereas induction of cytotoxicity is most likely mediated by distinct signaling pathways, allowing positive cooperativity.
Binding Sites↗
Efficacy of a new prostaglandin E1 regimen in outpatients with severe intermittent claudication: results of a multicenter placebo-controlled double-blind trial.
For the first time efficacy and safety of a new prostaglandin E1 (PGE1) regimen in the treatment of intermittent claudication were evaluated in a randomized, double-blind, placebo-controlled multicenter clinical trial. The study involved 213 outpatients with a maximum walking distance of 50 to 200 m measured on the treadmill (3 km/hr, 12% grade). After a 2-week run-in phase they received a 2-hour intravenous infusion of 60 micrograms PGE1 or placebo 5 days a week for 4 weeks. It was followed by a 4-week interval treatment with the same medication administered only twice a week. Patients were monitored for 3 months when they received no study medication. In the PGE1 group the intention-to-treat analysis (n = 208) revealed an increase in walking distance after 4 weeks of 75% (placebo, 43%). At the end of the interval treatment the walking distance had improved to 101% (placebo, 60%). The results remained virtually constant during follow-up (PGE1, 104%, placebo, 63%). Between-group comparisons showed significant differences in favor of PGE1 for all three time points of measurement (p < 0.05, p < 0.01, and p < 0.05). PGE1 was well tolerated; the rate of adverse reactions related to the treatment was 12.8% (placebo, 7.7%). In summary, these results show that the new PGE1 regimen is effective and safe in the treatment of outpatients with intermittent claudication.
Aged↗
Circulating vascular cell adhesion molecule-1 correlates with the extent of human atherosclerosis in contrast to circulating intercellular adhesion molecule-1, E-selectin, P-selectin, and thrombomodulin.
Secondary prevention of atherosclerosis, especially before the onset of symptoms, appears desirable and could be possible with a serum marker detecting atherosclerosis. Circulating, shedded forms of adhesion molecules may serve as such because their expression is upregulated in atherosclerotic plaques. In 52 patients with peripheral arterial vascular disease (Fontaine class IIa, 7 patients; class IIb, 29 patients; and class III, 16 patients), the extent of atherosclerosis was evaluated on the basis of angiograms of a large portion of the arterial system. The area diseased by atherosclerosis was determined by the percentage of vessel wall irregularities of the following calculated segments: aorta (distal from the kidney arteries), common iliac artery, external iliac artery, common femoral artery, lateral circumflex femoral artery, and popliteal artery. The maximal surface area that could exhibit atherosclerotic changes was 250 cm2. The serum concentration of circulating vascular cell adhesion molecule-1 (VCAM-1) correlated with the extent of atherosclerosis (r = .8, P < .001). In contrast, circulating intercellular adhesion molecule-1, E-selectin, P-selectin, and thrombomodulin (as markers for endothelial cell damage) did not correlate with the extent of atherosclerosis. Furthermore, circulating VCAM-1 could be used to indicate stages of atherosclerosis with a high degree of statistical significance. The potential bias of factors such as age, diabetes mellitus, hypercholesterolemia, arterial hypertension, renal failure, and history of myocardial infarction on the correlation of circulating VCAM-1 with the extent of atherosclerosis could be excluded by multivariate analysis. These findings suggest an important role of VCAM-1 in atherosclerosis and may serve as the basis for further evaluation of circulating VCAM-1 as a potential serum marker for atherosclerosis.
Adult↗
Reliability of dipole localization for the movement-evoked field component MEF I.
The movement-evoked field I (MEF I) component is the largest and most stable neuromagnetic component accompanying self-paced movements. In order to use MEG for studying dynamic changes in the cortical organization of movements, data about the reliability and variability of these neuromagnetic components for individual subjects must be established during different sessions. For this aim, three male subjects were requested to perform self-paced flexions of their index finger and thumb in repeated sessions while the MEG was recorded by a 31 channel system. The MEF I was identified for each session and a single equivalent dipole was calculated for this component. The dipole localizations of the various sessions were compared. The standard deviation of the localization for all persons and all values amounts to 4.0-5.2 mm for the three spatial dimensions. Our data suggest that the spatial distance between two single focal sources fitted to the MEF I must be greater than 14 mm to be interpreted as distinct. However, the neuromagnetic field structure and the resulting dipole localization of the MEF I component are quite stable and could be used for the evaluation of cortical plasticity.
Adult↗
Assessment of isometric contractions performed with maximal subjective effort: corresponding results for EEG changes and force measurements.
In order to find a parameter or parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were taken in connection with isometric muscle contractions performed with 80% of the subjective maximal force (IMC80) or with maximal subjective effort (IMC100). Criteria based on EEG recordings and force measurements have been considered as indicators for maximal subjective effort in a given movement. The following criteria were selected: A. If the mean spectral theta amplitude across the parieto-occipital area decreases from IMC80 to IMC100 then the isometric contraction is taken to be performed with maximal effort; B. If the obtained force values can be fitted to a switch function and if the achieved forces are only a predetermined percentage lower than the maximal force value obtained over all trials then this isometric contraction is accepted to be performed with maximal effort. 18 out of 24 cases fulfill the EEG criterion whereas the criterion for force measurements is fulfilled in 16 out of 24 trials. The comparison between the results obtained by means of the EEG criterion and by means of criterion for force measurement shows that the results are in agreement in 22 out of 24 cases (p < .001). The high correspondence of the assessments allows us to suspect that both criteria specify the same phenomenon, namely the performance of a motor task with maximal subjective effort.
Adult↗
Positive association of the beta fibrinogen H1/H2 gene variation to basal fibrinogen levels and to the increase in fibrinogen concentration during acute phase reaction but not to coronary artery disease and myocardial infarction.
BACKGROUND: Fibrinogen has been demonstrated to be an independent risk factor of cardiovascular disease. The absence of the HaeIII cutting site (H2 allele) of an H1/H2 gene variation in the promoter region of the beta fibrinogen gene was associated with increased levels of fibrinogen. METHODS AND RESULTS: In the present study, the effects of the H1/H2 gene variation not only on plasma fibrinogen concentrations but also on coronary artery disease (CAD) and myocardial infarction (MI) were investigated in 923 individuals who underwent coronary angiography for diagnostic purposes. Relation of the H1/H2 genotype to fibrinogen plasma levels: A strong association was observed between the H1/H2 gene variation and fibrinogen levels. The differences in fibrinogen plasma levels between H2H2 and H1H1 homozygotes were almost threefold more pronounced within subjects with clinical chemical signs of an acute phase reaction (CRP > or = 7.5 mg/l) than within a subgroup of subjects without these signs (CRP < 7.5 mg/l) (median of CRP distribution: 7.5 mg/l). In 207 patients who underwent aortocoronary bypass surgery plasma fibrinogen levels were almost identical directly after surgery. Two days after operation fibrinogen increased to clearly higher levels in H2H2 homozygotes than in H1H2 and H1H1 genotypes, whereas almost the same maximal increases in fibrinogen concentrations were reached 3-4 days after surgery in all individuals. Relation of the H1/H2 genotype to CAD and MI. Whereas in the total population the plasma fibrinogen concentrations were strongly associated with smoking, CAD and MI, an association of the H1/H2 gene variation to CAD and MI was not detected. However, mean age at first MI of H2H2 individuals (62.9 years) was clearly higher than of H1H2 genotypes (56.9 years) and of H1H1 subjects (56.4 years). In addition, in a subgroup of individuals with a higher risk of MI by either high apoB and/or low apoA1 plasma levels the portion of MI patients was clearly smaller within H2H2 homozygotes than within H1H2 or H1H1 genotypes, although-also in these high risk groups-mean age at first MI of H2H2 individuals were higher than of the other two genotypes. CONCLUSIONS: Obviously, the H2 allele of the fibrinogen H1/H2 genotype does not only influence basal fibrinogen concentrations, but particularly also the extent of fibrinogen level increase during acute phase reaction. Whereas the fibrinogen plasma level is positively associated with coronary artery disease and myocardial infarction, the H2 allele-although exhibiting an association with elevated fibrinogen levels-was not positively associated with CAD and MI.
Acute-Phase Reaction↗
Internal consistency of dipole localizations for the human movement-evoked magnetic field component 1 (MEF 1).
The present magnetoencephalographic study was conducted in order to assess the accuracy of dipole localizations for the movement-evoked field component 1 (MEF 1). Three male subjects were requested to perform self-paced flexions of their index finger and thumb in repeated sessions of 60 trials while the neuromagnetic field was recorded by a 31 channel system. Single moving dipole localizations were performed for the MEF 1. The error within single sessions was calculated by split-half reliability and window-homogeneity in a total of 61 sessions. The mean spatial deviation between both halves amounted to 3.8 mm. The window-homogeneity was found to be 2 mm deviation/10 ms.
Adult↗