Biomedical subjects

P Mueller

Publications and source records attributed to P Mueller.

At least 19 recordsLinked to original sources

PubMed2005

Fine structure of the 1s3p 3PJ level in atomic 4He: theory and experiment.

The fine structure intervals in helium have been the focus of many theoretical and experimental studies in recent years with most of them concentrating on the 1s2p (3)P(J) levels. Here, we report on a theoretical calculation and an experimental determination of the 1s2p (3)P(J) fine structure intervals. The values from the theoretical calculation are 8113.730(6) and 658.801(6) MHz for the nu(01) and nu(12) intervals, respectively. The laser spectroscopic measurement reported here yields 8113.714(28) and 658.810(18) MHz for these intervals and is in excellent agreement with the theoretical calculation. Both, however, disagree significantly with the previous most precise experimental results.

Journal Article↗

PubMed2005

The long sitting screening test in elite cyclists.

Pelvic rotation during cycling is important because it influences aerodynamics, cycling efficiency and the occurrence of overuse injuries. The aim of this study was to determine whether or not pelvic position in long sitting influences pelvic position during cycling. An observational, cross sectional, within-subjects study design was used. Thirty elite international track and road cyclists participated as subjects and two measures were undertaken. In long sitting, a digital inclinometer was positioned on the lumbosacral junction to give a static measure in degrees of sacral inclination (SI) relative to the horizontal. During active cycling, video analysis of reflective surface markers over the anterior superior iliac spine and posterior superior iliac spine was used to give a measure in degrees of anterior pelvic rotation (APR), by the angle between these two landmarks and the horizontal. No significant linear relationship was found between the two testing positions (r = 0.23, p = 0.22).

Adolescent↗

PubMed2004

Laser spectroscopic determination of the 6He nuclear charge radius.

We have performed precision laser spectroscopy on individual 6He (t(1/2)=0.8 s) atoms confined and cooled in a magneto-optical trap, and measured the isotope shift between 6He and 4He to be 43 194.772+/-0.056 MHz for the 2(3)S1-3(3)P2 transition. Based on this measurement and atomic theory, the nuclear charge radius of 6He is determined for the first time in a method independent of nuclear models to be 2.054+/-0.014 fm. The result is compared with the values predicted by a number of nuclear structure calculations and tests their ability to characterize this loosely bound halo nucleus.

Journal Article↗

PubMed2004

Search for anomalously heavy isotopes of helium in the earth's atmosphere.

Our knowledge of the possible existence in nature of stable exotic particles depends solely upon experimental observation. Using a sensitive laser spectroscopy technique, we searched for a doubly charged particle accompanied by two electrons as an anomalously heavy isotope of helium in the Earth's atmosphere. The concentration of noble-gas-like atoms in the atmosphere and the subsequent very large depletion of the light (3,4)He isotopes allow stringent upper limits to be set on the abundance: 10(-12)-10(-17) per atom in the solar system over the mass range of 20-10 000 amu.

Journal Article↗

PubMed2003

Validation of an ESI-MS/MS screening method for acylcarnitine profiling in urine specimens of neonates, children, adolescents and adults.

BACKGROUND: Acylcarnitine (AC) profiling in dried blood spots by means of electrospray ionisation tandem mass spectrometry (ESI-MS/MS) has proven to be a useful method in neonatal screening, able to detect inborn errors of fatty acid oxidation, amino acid, organic acid and carnitine metabolism. Furthermore, this method is becoming increasingly applied in selective screening and in prenatal and postmortal diagnostics of inborn metabolic disorders, where urine is commonly used as specimen of interest. We therefore developed and validated a butylation method of acylcarnitine profiling in urine by ESI-MS/MS without previous chromatographic separation. METHODS: Random urine specimens were used for investigation of the analytical imprecision of the method. Recovery, precision and linearity were determined using methanolic standard solutions of free carnitine, octanoylcarnitine and palmitoylcarnitine at various concentrations. RESULTS: The mean coefficients of variation of within-run and run-to-run analysis of these analytes were found between 10% and 20% and demonstrated that the method fulfills the analytical requirements within the relevant ranges of concentration. Creatinine-related and age-related reference values of free carnitine and the ACs (C2-C18) were established. The definite discrimination was possible between patients with fatty acid oxidation disorders, organic acidurias, and healthy controls. The AC profiles from patients with various specific disorders were diagnostically helpful during acute deterioration and even during conditions of well-compensated metabolic state. CONCLUSION: The method used in this study is suitable both for selective screening and for confirmation of diagnosis with the advantage of high-throughput quantitative measurement.

Adolescent↗

PubMed2003

Adapting the fluoroscope to image-guided surgery.

Image-guided techniques have been well established in all surgical disciplines for years. To achieve an optimised work flow during image-guided surgery, the surgeon should be able to manipulate the visual feedback and therefore the imaging unit. C-arm fluoroscopy is the imaging modality routinely used for intraoperative imaging in orthopaedic surgery. The C-arm fluoroscope is positioned and handled by a radiographer on vocal commands, which means that the surgeon depends on external help to manipulate the visual feedback and the work flow is not optimised. The MEPUC interface adapts the C-arm fluoroscope to the needs of image-guided orthopaedic procedures. MEPUC is an acronym for Motorised Exact-Positioning Unit for C-arm. In the hardware component of the MEPUC a conventional C-arm fluoroscope is equipped with stepping motors. The software component allows the surgeon to control the motorised movements of the fluoroscope. The MEPUC interface enables the surgeon to position the C-arm fluoroscope independently in the operating room. Further advantages are achievable when the MEPUC interface is combined with surgical navigation, as this combination allows fully automatic reproduction of former projections. Clinical experience with the MEPUC interface suggests that the work flow for intraoperative imaging is improved and personal requirements reduced.

Fluoroscopy↗

PubMed2001

Metabolic rate and environmental productivity: well-provisioned animals evolved to run and idle fast.

Even among vertebrate species of the same body mass and higher-level taxonomic group, metabolic rates exhibit substantial differences, for which diverse explanatory factors-such as dietary energy content, latitude, altitude, temperature, and rainfall-have been postulated. A unifying underlying factor could be food availability, in turn controlled by net primary productivity (NPP) of the animal's natural environment. We tested this possibility by studying five North American species of Peromyscus mice, all of them similar in diet (generalist omnivores) and in gut morphology but differing by factors of up to 13 in NPP of their habitat of origin. We maintained breeding colonies of all five species in the laboratory under identical conditions and consuming identical diets. Basal metabolic rate (BMR) and daily ad libitum food intake both increased with NPP, which explained 88% and 90% of their variances, respectively. High-metabolism mouse species from high-NPP environments were behaviorally more active than were low-metabolism species from low-NPP environments. Intestinal glucose uptake capacity also increased with NPP (and with BMR and food intake), because species of high-NPP environments had larger small intestines and higher uptake rates. For metabolic rates of our five species, the driving environmental variable is environmental productivity itself (and hence food availability), rather than temporal variability of productivity. Thus, species that have evolved in the presence of abundant food run their metabolism "fast," both while active and while idling, as compared with species of less productive environments, even when all species are given access to unlimited food.

Animals↗

PubMed2001

Health effects of long-term mercury exposure among chloralkali plant workers.

BACKGROUND: Inorganic mercury is toxic to the nervous system, kidneys, and reproductive system. We studied the health effects of mercury exposure among former employees of a chloralkali plant that operated from 1955 to 1994 in Georgia. METHODS: Former plant workers and unexposed workers from nearby employers were studied. Exposure was assessed with a job-exposure matrix based on historical measurements and personnel records. Health outcomes were assessed with interviews, physical examinations, neurological and neurobehavioral testing, renal function testing, and urinary porphyrin measurements. Exposure-disease associations were assessed with multivariate modeling. RESULTS: Exposed workers reported more symptoms, and tended toward more physical examination abnormalities, than unexposed workers. Exposed workers performed worse than unexposed subjects on some quantitative tests of vibration sense, motor speed and coordination, and tremor, and on one test of cognitive function. Few findings remained significant when exposure was modeled as a continuous variable. Neither renal function nor porphyrin excretion was associated with mercury exposure. CONCLUSIONS: Mercury-exposed chloralkali plant workers reported more symptoms than unexposed controls, but no strong associations were demonstrated with neurological or renal function or with porphyrin excretion.

Abortion, Spontaneous↗

PubMed2001

The vascular-associated lymphoid tissue: a new site of local immunity.

Recent data suggest that atherosclerosis might be a systemic (auto)immune reaction against heat shock protein 60, first occurring at notorious local predilection sites, i.e. the intima at arterial branching points. The local infiltration of mononuclear cells, mainly macrophage-derived foam cells, T cells and smooth-muscle cells in atheromatous plaques, have long been described. During the past few years, research has been concentrated on the early stages in the development of atherosclerosis, and on healthy arteries from young individuals unaffected by arterial disease. In this review, we summarize data characterizing pre-existing mononuclear cell infiltrations in healthy arteries from children and teenagers. These arterial accumulations at regions known to be predilection sites for the later development of atherosclerosis consist mostly of activated T cells, macrophages and dendritic cells, with only a few mast cells and virtually no B or natural killer cells. In analogy to the mucosa-associated lymphoid tissue, we termed these accumulations 'vascular-associated lymphoid tissue', and assumed a similar function as a local immunosurveillance system, monitoring the bloodstream for potentially harmful endogenous or exogenous antigens. In addition to the remarkable accumulation of mononuclear cells, the vascular-associated lymphoid tissue regions are characterized by a typical distribution of extracellular matrix proteins: collagen type I, collagen type III, fibronectin and tenascin are expressed preferentially in the vascular-associated lymphoid tissue region, whereas collagen type IV, collagen type V, collagen type VI and laminin show a homogenous distribution throughout all regions of the intima. Vascular adhesion molecules type 1, intercellular adhesion molecules type 1 and P-selectin are already present on the healthy endothelial cells of young children. Interactions between adhesion molecules, extracellular matrix components and cellular elements of the vascular-associated lymphoid tissue may provide the basis for the cellular accumulations in the vascular-associated lymphoid tissue regions and the possible development of atherosclerotic lesions later in life.

Animals↗

PubMed2001

Acoustic-phonetic features for the automatic classification of fricatives.

In this article, the acoustic-phonetic characteristics of the American English fricative consonants are investigated from the automatic classification standpoint. The features studied in the literature are evaluated and new features are proposed. To test the value of the extracted features, a statistically guided, knowledge-based, acoustic-phonetic system for the automatic classification of fricatives in speaker-independent continuous speech is proposed. The system uses an auditory-based front-end processing system and incorporates new algorithms for the extraction and manipulation of the acoustic-phonetic features that proved to be rich in their information content. Classification experiments are performed using hard-decision algorithms on fricatives extracted from the TIMIT database continuous speech of 60 speakers (not used in the design/training process) from seven different dialects of American English. An accuracy of 93% is obtained for voicing detection, 91% for place of articulation detection, and 87% for the overall classification of fricatives.

Algorithms↗

PubMed2001

Development of peak performance in track cycling.

BACKGROUND: Retrospective analysis of peak performances can be a usefull tool for the estimation of future trends in high performance sports. The purpose of this study was to investigate the evolution of performance in track cycling from 1979 to 1999 and to asses age- and gender-related differences. METHODS: We studied the results of the world track cycling championships for this period in 200 m, 1000 m, individual and team pursuit races for elite and junior athletes. Overall trends, performance differences between rank 1 and 5, gender- and age-related differences were calculated. RESULTS: They show a significant (p<0.01) improvement in 1000 m, individual and team pursuit times for men and individual pursuit times for women. No significant evolution was seen in 200 m performance. In junior riders, only male athletes showed a continuous, significant improvement of average race speed in individual and team pursuit over the study period. Gender difference was 11+/-1.8% in all disciplines at all ages. Difference between elite and junior riders ranged between 5+/-2.1% for male and 6.1+/-2.2% for female athletes. The gap between rank 1 and 5 remained constant (2-3%) over the study period. CONCLUSIONS: A continuous improvement of performance over the last 20 years is visible in track cycling endurance disciplines. New technical developments show no statistical significant impact. The performance gap between male and female athletes is constant, independent of discipline or race distance and comparable to observations in other sports. Age-related differences in performance is most visible in disciplines requiring short, high intensity power output. Based on these data, estimation of possible winning times and adaptation of training programs for future track cycling competitions might be facilitated.

Adolescent↗

PubMed2000

5'-Methoxyhydnocarpin-D and pheophorbide A: Berberis species components that potentiate berberine growth inhibition of resistant Staphylococcus aureus.

A new method of bioactivity-directed fractionation, based on multidrug resistant pump (MDR) inhibition in Staphylococcus aureus, was demonstrated. This resulted in the isolation, from berberine-containing Berberis species, of two compounds that are themselves devoid of S. aureus antibacterial activity, but that form potent synergistic couples with a subinhibitory concentration of berberine. The bacterial MDR pump inhibitors were identified as the flavonolignan 2 and the porphyrin 3. Another natural flavonolignan, silybin (8) from Silybum marianum, was also shown to be a bacterial MDR pump inhibitor.

Berberine↗

PubMed2000

Exercise training and myocardial remodeling in patients with reduced ventricular function: one-year follow-up with magnetic resonance imaging.

BACKGROUND: Exercise training is now an accepted therapeutic intervention in patients with reduced ventricular function after a myocardial infarction. However, there are conflicting reports on the effects of training on the remodeling process of the heart, and previous studies have only assessed short-term effects of training. METHODS AND RESULTS: Twenty-five patients with reduced ventricular function after myocardial infarction were randomly assigned to an intensive 2-month exercise training program or to a control group (control group: n = 13, aged 55 +/- 7 years, ejection fraction 33.3% +/- 6%; exercise group: n = 12, aged 56 +/- 5 years, ejection fraction 31.5% +/- 7%) and followed up for 1 year. Measures of left ventricular size, function, and wall thickness in the infarct and noninfarct areas were made by magnetic resonance imaging at baseline, after the 2-month training period, and 1 year later. Maximal oxygen uptake increased in the trained group, from 19.7 +/- 3 mL/kg per minute at baseline to 25.1 +/- 5 and 24.2 +/- 5 mL/kg per minute after 2 months and 1 year, respectively (P <.05 vs baseline for both), whereas the control group did not change significantly. Ejection fraction, end-diastolic volumes, and end-systolic volumes did not change at any measurement point throughout the study period in either the trained or control groups. Myocardial wall thickness measurements at end-diastole and end-systole and their differences determined by magnetic resonance imaging yielded no significant interactions between groups. When myocardial wall thickness measurements were classified by infarct or noninfarct areas, no differences were observed between groups over the study period. CONCLUSIONS: Intensive exercise training in patients with reduced ventricular function resulted in a significant improvement in exercise capacity after 2 months, and this improvement was sustained over 1 year. In contrast to some recent reports, training had no deleterious effects on left ventricular volume, function, or wall thickness regardless of infarct area.

Exercise Test↗

PubMed2000

Modeling of potential power plant plume impacts on Dallas-Fort Worth visibility.

During wintertime, haze episodes occur in the Dallas-Ft. Worth (DFW) urban area. Such episodes are characterized by substantial light scattering by particles and relatively low absorption, leading to so-called "white haze." The objective of this work was to assess whether reductions in the emissions of SO2 from specific coal-fired power plants located over 100 km from DFW could lead to a discernible change in the DFW white haze. To that end, the transport, dispersion, deposition, and chemistry of the plume of a major power plant were simulated using a reactive plume model (ROME). The realism of the plume model simulations was tested by comparing model calculations of plume concentrations with aircraft data of SF6 tracer concentrations and ozone concentrations. A second-order closure dispersion algorithm was shown to perform better than a first-order closure algorithm and the empirical Pasquill-Gifford-Turner algorithm. For plume impact assessment, three actual scenarios were simulated, two with clear-sky conditions and one with the presence of fog prior to the haze. The largest amount of sulfate formation was obtained for the fog episode. Therefore, a hypothetical scenario was constructed using the meteorological conditions of the fog episode with input data values adjusted to be more conducive to sulfate formation. The results of the simulations suggest that reductions in the power plant emissions lead to less than proportional reductions in sulfate concentrations in DFW for the fog scenario. Calculations of the associated effects on light scattering using Mie theory suggest that reduction in total (plume + ambient) light extinction of less than 13% would be obtained with a 44% reduction in emissions of SO2 from the modeled power plant.

Aerosols↗

PubMed1998

Low frequency epithelial cells in bone marrow aspirates from prostate carcinoma patients are cytogenetically aberrant.

BACKGROUND: Low frequency epithelial cells occur in bone marrow aspirates of 25-50% of patients with locally confined prostate carcinoma. It is assumed that bone marrow epithelial cells derive from the primary tumor; however, it has not been established unequivocally that they are tumor cells. Immunofluorescence approaches were used to quantify the frequency of epithelial cells in bone marrow aspirates from prostate carcinoma patients and genotypic analyses were used to determine whether they contained numeric aberrations of chromosomes 1, 7, and 8. METHODS: Epithelial cells in bone marrow aspirates collected after radical prostatectomy were visualized using fluorescence microscopy and fluorophore-linked antibodies against cytokeratin 8,18 (CK) and prostate specific antigen (PSA). Antibodies specific for proliferating nuclear cell antigen (PCNA) were used to evaluate the cycling status of discriminated cells. Copies of chromosomes 1, 7, and 8 in the discriminated epithelial cells were quantified using fluorescence in situ hybridization. RESULTS: CK+ cells were present in bone marrow aspirates from 30 of 66 patients (approximately 45%) at a median frequency of 1.4 CK+ cells/10(5) mononuclear cells. Few CK+ epithelial cells in the bone marrow aspirates coexpressed PSA and none of the CK+ cells expressed PCNA. Approximately 70-75% of the CK+ cells contained 7 and 8 aneusomies. Gains of chromosome 1 occurred in 42% of the CK+ cells. CONCLUSIONS: The majority of CK+ cells in bone marrow aspirates collected after surgery are cytogenetically aberrant, which is consistent with a primary tumor origin. The prevalence and frequency of CK+ cells is independent of tumor stage/grade and androgen treatment.

Aged↗

PubMed1998

Donor pretreatment with ambroxol or dexamethasone fails to ameliorate reperfusion injury in experimental lung transplantation.

Based on the known properties of ambroxol and dexamethasone to inhibit inflammation and increase endogenous surfactant levels, the potential advantage of donor pretreatment with either drug was investigated in an acute rat double-lung transplant model. Donor animals were randomly assigned to one of three treatment groups: an ambroxol group (AMB; 0.4 mg/kg), a dexamethasone group (DX; 2 mg/kg); or an untreated control group (CN). Drugs were given intraperitoneally 6 h prior to harvest. Following standard preservation and 16 h of cold ischemia, the donor double lung block was implanted into syngeneic recipients using custom-designed stents for the vascular anastomosis. During reperfusion, serial measurements of graft pulmonary vascular resistance and alveolar-arterial oxygen difference were obtained. Separate graft ventilation allowed determination of graft dynamic lung compliance. Final assessment included weight gain and histology. For phospholipid analysis, lung lavages were performed in the three study groups at the end of reperfusion and compared to levels before graft harvest. Donor pretreatment did not significantly affect preharvest phospholipid levels. Survival following graft ischemia and reperfusion was shortest after AMB (92 +/- 5 min) and longest after DX (110 +/- 5 min; DX vs AMB P < 0.03) and CN (116 +/- 4 min; CN vs AMB P < 0.02). DX pretreatment provided better compliance (P < 0.02) and lower vascular resistance (P < 0.0001) than AMB treatment. Airway resistance was lower in the AMB and DX groups than in controls (P < 0.04 and P < 0.02, respectively). The alveolar-arterial oxygen difference was markedly similar in all groups. Graft weight gain amounted to 114% +/- 10% in AMB, 88% +/- 12% in DX, and 98% +/- 13% in CN (P = NS). Thus, in this rat lung transplantation model, donor pretreatment with dexamethasone did not improve graft function compared to untreated controls and donor pretreatment with ambroxol was found to be potentially detrimental to graft function during reperfusion.

Ambroxol↗

PubMed1997

Donor treatment with the lazeroid U74389G reduces ischemia-reperfusion injury in a rat lung transplant model.

BACKGROUND: Antioxidant treatment with lazeroids has proven beneficial for the amelioration of reperfusion injury in experimental lung transplantation. This study compares the effect of donor versus recipient treatment on immediate postoperative graft function. METHODS: A model of acute double-lung transplantation in rats was used to assess graft function. Transplanted controls after 2 (group I) and 16 hours of ischemia (group II) were compared to a recipient (group III; 16-hour ischemia) and a donor treatment group (group IV; 16-hour ischemia) using the lazeroid U74389G (6 mg/kg). Serial assessment of alveolar-arterial oxygen difference, dynamic lung compliance, airway and pulmonary vascular resistance was obtained during a 2-hour reperfusion period. Final analysis included survival, weight gain, and histologic examination. RESULTS: Graft function was significantly better after 2 hours of ischemia than in any of the three 16-hour ischemia groups (II, III, IV). After 16 hours of ischemia, donor treatment provided superior graft function with respect to dynamic lung compliance, airway resistance, and alveolar-arterial oxygen difference when compared with groups II and III. The pulmonary vascular resistance was significantly higher in group III when compared with groups II and IV. Graft weight increase reflecting edema was highest in groups III (104%) and II (98%). CONCLUSIONS: After prolonged ischemia only donor treatment with the lazeroid U74389G was able to significantly reduce ischemia-reperfusion-related graft dysfunction.

Airway Resistance↗

PubMed1997

Multicenter evaluation of the Micral-Test II test strip, an immunologic rapid test for the detection of microalbuminuria.

OBJECTIVE: To assess the performance of the Micral-Test II immunologic test strip for the detection of microalbuminuria, a multicenter evaluation in eight European study sites was performed. RESEARCH DESIGN AND METHODS: Using both the Micral-Test II test strip and the routine method for the determination of albumin concentration, we investigated 2,228 urine samples from diabetic patients. Additionally, interperson variability, color stability, and possible interfering factors (temperature, pH, leucocyturia, erythrocyturia, and drugs) were tested. RESULTS: For a cutoff concentration of 20 mg/l with respect to the routine methods, a sensitivity of 96.7% and a specificity of 71% were calculated for the Micral-Test II test strip. The negative predictive value was 0.95, and the positive predictive value was 0.78, with a prevalence of positive samples (laboratory method) of 52%. The interperson variability of color interpretation showed 93% concordant readings. The interference study showed an influence of oxytetracycline, leading to higher readings. There was no interference from pH. A sample temperature of < 10 degrees C led to lower readings. In the case of samples with massive leucocyturia and erythrocyturia that may delete the chromatographic process, waiting an additional 1-2 min is needed before reading. CONCLUSIONS: The results of the multicenter evaluation show that the Micral-Test II test strip permits an immediate and reliable semiquantitative determination of low albumin concentrations in urine samples with an almost user-independent color interpretation.

Albuminuria↗