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Biomedical subjects

D Meier

Publications and source records attributed to D Meier.

At least 55 records · Page 3Linked to original sources
PubMed1998

Randomised double-blind placebo-controlled trial of thrombolytic therapy with intravenous alteplase in acute ischaemic stroke (ECASS II). Second European-Australasian Acute Stroke Study Investigators.

BACKGROUND: Thrombolysis for acute ischaemic stroke has been investigated in several clinical trials, with variable results. We have assessed the safety and efficacy of intravenous thrombolysis with alteplase (0.9 mg/kg bodyweight) within 6 h of stroke onset. METHODS: This non-angiographic, randomised, double-blind, trial enrolled 800 patients in Europe, Australia, and New Zealand. Computed tomography was used to exclude patients with signs of major infarction. Alteplase (n=409) and placebo (n=391) were randomly assigned with stratification for time since symptom onset (0-3 h or 3-6 h). The primary endpoint was the modified Rankin scale (mRS) at 90 days, dichotomised for favourable (score 0-1) and unfavourable (score 2-6) outcome. Analyses were by intention to treat. FINDINGS: 165 (40.3%) alteplase-group patients and 143 (36.6%) placebo-group patients had favourable mRS outcomes (absolute difference 3.7%, p=0.277). In a posthoc analysis of mRS scores dichotomised for death or dependency, 222 (54.3%) alteplase-group and 180 (46.0%) placebo-group patients had favourable outcomes (score 0-2; absolute difference 8.3%, p=0.024). Treatment differences were similar whether patients were treated within 3 h or 3-6 h. 85 (10.6%) patients died, with no difference between treatment groups at day 90+/-14 days (43 alteplase, 42 placebo). Symptomatic intracranial haemorrhage occurred in 36 (8.8%) alteplase-group patients and 13 (3.4%) placebo-group patients. INTERPRETATION: The results do not confirm a statistical benefit for alteplase. However, we believe the trend towards efficacy should be interpreted in the light of evidence from previous trials. Despite the increased risk of intracranial haemorrhage, thrombolysis with alteplase at a dose of 0.9 mg/kg in selected patients may lead to a clinically relevant improvement in outcome.

Adolescent↗
PubMed1998

Quantitative 1H MRS of the human brain in vivo based on the stimulation phantom calibration strategy.

Normal metabolite concentrations were determined in five different brain regions of healthy adult volunteers using proton magnetic resonance spectroscopy (1H MRS) in vivo. The absolute in vivo concentrations of N-acetylaspartate (NAA), creatine and phosphocreatine (Cre), and choline containing compounds (Cho) were quantified from measurements obtained with a head-shaped simulation phantom. Scanner performance and calibration accuracy were assessed by phantom experiments. Localized spectra were acquired on clinical 1.5 T systems using the PRESS localization sequence with frequency selective water suppression. Comparison of the results obtained from phantom experiments and human brain in vivo strongly suggests that reproducibility in vivo mainly depends on the topologic metabolite heterogeneity of brain tissue in combination with relative volume dislocalization.

Adolescent↗
PubMed1998

Heuristic optimization algorithms applied to the quantification of spectroscopic data.

The quantification of in vivo MR spectra imposes severe problems because of low spectral resolution and poor signal-to-noise ratio. Maximum likelihood methods are often applied. However, with conventional spectrum analysis procedures, the search for a global minimum in a multidimensional space often terminates in only a local minimum. Heuristic optimization procedures are able to circumvent this difficulty. Two approaches, the genetic algorithm and the simulated annealing, have been adapted to the quantification of MR spectra. For evaluation purposes, the procedures have been applied to synthetic and in vivo spectra with different noise levels. They both allowed a reliable spectrum quantification. The areas of most peaks were quantified reproducibly, although in some cases, the discrimination between spectroscopically almost identical metabolites (e.g., glutamate and glutamine) was not completely satisfactory. The two algorithms are found to be valuable alternative methods in the quantification of in vivo MR spectra.

Algorithms↗
PubMed1998

A new correlation-based fuzzy logic clustering algorithm for fMRI.

Fuzzy logic clustering algorithms are a new class of processing strategies for functional MRI (fMRI). In this study, the ability of such methods to detect brain activation on application of a stimulus task is demonstrated. An optimization of the selected algorithm with regard to different parameters is proposed. These parameters include (a) those defining the pre-processing procedure of the data set; (b) the definition of the distance between two time courses, considered as p-dimensional vectors, where p is the number of sequential images in the fMRI data set; and (c) the number of clusters to be considered. Based on the assumption that such a clustering algorithm should cluster the pixel time courses according to their similarity and not their proximity (in terms of distance), cross-correlation-based distances are defined. A clear mathematical description of the algorithm is proposed, and its convergence is proven when similarity measures are used instead of conventional Euclidean distance. The differences between the membership function given by the algorithm and the probability are clearly exposed. The algorithm was tested on artificial data sets, as well as on data sets from six volunteers undergoing stimulation of the primary visual cortex. The fMRI maps provided by the fuzzy logic algorithm are compared to those achieved by the well established cross-correlation technique.

Algorithms↗
PubMed1998

Quantitative 1H MRS in the evaluation of mesial temporal lobe epilepsy in vivo.

Hippocampal metabolite concentrations were determined by localized in vivo proton magnetic resonance spectroscopy (1H MRS) in eleven patients suffering from refractory mesial temporal lobe epilepsy (MTLE), as well as in eleven age-matched healthy volunteers, and compared with patient history, postoperative outcome and histopathology. Main results are: 1) In patients, the decrease in N-acetylaspartate (NAA) concentrations was highly significant ipsilateral, and less but still significant contralateral to the electroencephalogram-defined focus, as compared to controls. 2) The decrease in ipsilateral NAA measured preoperatively correlates with the degree of hippocampal sclerosis but 3) does not reliably predict postoperative outcome, although there is a trend toward better outcome in patients with a marked decrease of NAA. 4) Hippocampal NAA decrease (ipsi- and contralateral) is highly correlated with early onset age of epileptic seizures. 5) Among patients with similar onset age in early childhood, there is a strong association between duration of the disease and contralateral (and, though less clear-cut, ipsilateral) NAA loss. These results are concordant with the notion of a generally progressive worsening and complicating course of symptoms in poorly controlled MTLE.

Adult↗
PubMed1998

Pathology of mitral valve in regularly slaughtered pigs: an abattoir survey on the occurrence of myxoid degeneration (endocardiosis), fibrosis and valvulitis.

The aim of this study was to report the prevalence of degenerative and early inflammatory lesions and to discuss some histological aspects of normal and pathological mitral valve leaflets in healthy, normally slaughtered pigs. Mitral valves were collected from 112, 6 month-old, pigs reared under different conditions. Histological examination revealed the presence of myxoid degeneration in 29.5% of the valves with no significantly different prevalence according to rearing conditions; fibrosis was present in 12.5%; inflammation (non-vegetative valvulitis) occurred in 20 (17.9%) macroscopically normal valves. No vegetative endocarditis could be observed. A significantly higher degree of inflammation was observed in valves affected by myxoid degeneration (P < 0.05) and Anitschkow cells were prevalent in all the pathological valves (P < 0.01). Capillaries were observed in a wide majority of the valves (86.5%), but small arterioles were related to fibrotic thickening of the leaflets (P < 0.01). The following conclusions are discussed: (1) environmental factors seem not to influence the prevalence of endocardiosis; (2) inflammatory foci in myxoid valves are a reaction to both abnormal friction and products of degraded collagen and extracellular matrix; (3) the authors consider the presence of capillaries in pig valves a normal finding whereas proliferation of the vessels occurs under pathological conditions; (4) non vegetative valvulitis can be related to the presence of vessels in the valve and may have a role in both infectious endocarditis and fibrosis; (5) Anitschkow cells are normally observed in pig valves and are not specifically related to pathological lesions.

Abattoirs↗
PubMed1998

Dichotomized efficacy end points and global end-point analysis applied to the ECASS intention-to-treat data set: post hoc analysis of ECASS I.

BACKGROUND AND PURPOSE: It is not yet known which end points are the most suitable for evaluation of the effects of acute stroke intervention. The European Cooperative Acute Stroke Study (ECASS) I study used 2 primary end points. The study was powered to detect a 15% improvement of the median of each primary end point. The study failed to show this effect and was negative in the intention-to-treat analysis. The National Institute of Neurological Disorders and Stroke (NINDS) study used 4 dichotomized end points and applied a global end-point analysis. This study was positive and led to FDA approval of thrombolytic therapy for acute ischemic stroke. This study was undertaken to answer the question of whether a different statistical design may have shown a positive results of the ECASS I trial. METHODS: We performed a retrospective analysis of the ECASS I intention-to-treat data set (615 randomized and treated patients, rtPA treatment versus placebo) and post hoc application of the NINDS trial statistical methodology (global end-point analysis). The scores of the modified Rankin Scale (mRS), Barthel Index (BI), and the National Institutes of Health Stroke Scale (NIHSS) were dichotomized according to the criteria used in the NINDS trial. Favorable outcome was defined as a score of 0 or 1 on mRS, a score of 95 or 100 on BI, and a score of 0 or 1 on NIHSS. RESULTS: The number of patients reaching favorable outcome were higher in all 3 end points in the rtPA-treated group. The effect sizes were 8% for mRS, 6% for BI, and 14% for NIHSS, respectively. The differences are statistically significant for the mRS (P=0.044; odds ratio [OR], 1. 4; 95% confidence interval [CI], 1.0 to 2.0) and the NIHSS (P=0.001; OR, 1.9; 95% CI, 1.4 to 2.8), while for the BI significance was missed (P=0.102; OR, 1.3; 95% CI, 0.9 to 1.8). The global end-point statistics, however, shows a significant increase (P=0.008; OR, 1.5; 95% CI, 1.1 to 2.0) of favorable outcome in the rtPA-treated patient group. CONCLUSIONS: Using the global end-point analysis, ECASS is positive in the intention-to-treat analysis. This may indicate that the time window for thrombolysis may be as long as 6 hours. Looking at the 3 dichotomized end points, the effect sizes for 2 end points, mRS and BI, are smaller in the ECASS 6-hour intention-to-treat population compared with the NINDS trial, whereas the effect size for the NIHSS is larger. While in the NINDS trial all 3 end points reveal statistically significant results, in ECASS only 2 of the 3 corresponding end points, mRS and NIHSS, were statistically significant. This finding underlines an important difference of a global end-point approach: it may show a positive overall result although one of the end points is not positive.

Cerebrovascular Disorders↗
PubMed1998

Memory Clinics in Switzerland. Collaborative Group of Swiss Memory Clinics.

Currently, eleven Memory Clinics (MC) in Switzerland offer their services to patients, caregivers and family doctors. Their primary goal is the early diagnosis and management of dementia in elderly outpatients. Special emphasis is put on the detection of reversible causes of dementing disorders. Diagnoses and medical, pharmacological, neuropsychological and social treatment recommendations are established in a multidisciplinary consensus conference and communicated back to the referring physicians. The psychosocial therapies and supportive activities include counseling, memory training for patients, neuropsychological rehabilitation, caregiver groups, relaxation and biofeedback training, day care centers, Alzheimer's Tanzcafé, and special vacations for dementia patients. These activities vary from MC to MC according to the availability of resources. Research activities are an integral part of all MCs and range from the attempt to identify preclinical markers of Alzheimer's disease to studies of neuropathological correlates of cognitive disturbances. Moreover, patients are encouraged to participate in studies investigating new medications. MCs play an important role in the education and training of health care professionals and in raising awareness and support in the general population.

Aged↗
PubMed1998

[Greenish discolorations of beef musculature and their assessment according the meat hygiene regulations. A case report].

In muscular tissue samples from two cows of different origin numerous greenish, spotlike tissue discolourations were diagnosed as eosinophilic myositis. Sarcosporidiosis is being suspected as the most likely cause. Factors leading to such cases of myositis due to sarcosporidiosis which is wide-spread in cattle and normally inapparent are largely unknown. According to Swiss and German meat inspection directives beef carcasses with these discolourations have to be declared as unfit for human consumption. However, during meat inspection such cases of myositis are problematic to diagnose, because the lesions are only visible on the cut end of muscle tissue. Hence, they can pass unnoticed through carcass inspection.

Animal Husbandry↗
PubMed1997

Histomorphometric assessment of bone mass, structure, and remodeling: a comparison between healthy black and white premenopausal women.

While noninvasive studies of bone mass and turnover in blacks and whites abound, histologic evaluations are very rare. We have performed a comparative bone histomorphometric study of iliac biopsies from 55 healthy, premenopausal women including 21 blacks (mean age 33.4 + 1.2 years) and 34 whites (mean age 32.5 + 0.8 years) of comparable age, weight, body composition, education, and lifestyle. Biochemical indices of mineral metabolism: parathyroid hormone, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, serum ionized calcium, serum phosphorus, and urinary calcium/creatinine were measured in the fasting state. Blacks had lower 25-hydroxyvitamin D (315 +/- 3.36 vs. 63.21 +/- 3.79 nmol/l, p = 0.0001). Histomorphometric indices of bone volume, structure, and connectivity were not different between groups. The following indices of bone remodeling were also similar in both groups: eroded perimeter, osteoid width, mineralizing perimeter, tissue-based bone formation rate, osteoid maturation time, active formation period, and activation frequency. However, osteoid perimeter (black [B] = 15.85 +/- 1.30 vs. white [W] = 9.49 +/- 0.70%, p = 0.0002), osteoid area (B = 2.55 +/- 0.32 vs. W = 1.39 +/- 0.12%, p = 0.003), single-labeled perimeter (B = 5.46 +/- 0.54 vs. W = 4.04 +/- 0.33%, p = 0.03), mineralization lag time (B = 38.18 +/- 4.04 vs. W = 21.83 +/- 1.60 days, p < 0.009), and total formation period (B = 148.15 +/- 19.70 vs. W = 84.04 +/- 7.62 days, p = 0.0056) were higher in blacks than in whites. The quiescent perimeter (B = 76.91 +/- 1.40 vs. W = 84.25 +/- 0.91%, p = 0.0001), mineral apposition rate (B = 0.70 +/- 0.02 vs. W = 0.75 +/- 0.02 micron/day, p = 0.066), mineralizing osteoid perimeter (B = 0.49 +/- 0.04 vs. W = 0.75 +/- 0.04%, p = 0.0001) and adjusted apposition rate (B = 0.35 +/- 0.04 vs. W = 0.58 +/- 0.04 micron3/micron2/day, p = 0.0001) were all lower in blacks than in whites. These results indicate that there are no differences in bone volume, microstructure, or turnover between black and white premenopausal women. However, there are significant differences in the mechanism of bone formation between the two groups, with a lower rate of mineralized matrix apposition within each remodeling unit and a longer total formation period in blacks than in whites. The differences appear to the result of more frequent and/or longer inactive periods in the life span of the bone formation units in blacks. These differences may allow a greater overall deposition of bone mineral in black women and therefore help explain a higher bone mass and perhaps better bone quality in black than white women.

Adult↗
PubMed1997

[A case of cutaneous epitheliotropic malignant lymphoma (mycosis fungoides) in a horse].

This article describes an eleven year old mare with apathy, fever, enlarged mandibular lymph nodes, skin lesions on the upper lip and edematous, grey-red mucous membranes in the nose, mouth and vulva. Histopathology revealed infiltrates with atypical lymphocytes forming Pautrier's microabscesses. The neoplastic cells had large, often indented nuclei. Immunohistology showed that some cells were CD3-positive (Pan T-cell-marker). The diagnosis of cutaneous epitheliotropic malignant lymphoma (Mycosis fungoides) was made. The etiology in the horse is unknown.

Animals↗
PubMed1997

[Assessment of the quality of life].

Assessment of quality of life (qol) is becoming increasingly important, particularly as an outcome variable in assessing the impact of disease, illness and treatment. However, considerable problems exists in formulation, measurement and interpretation of qol. There is as yet no agreed-upon definition of qol nor is there a gold standard measure what complicates the selection of an appropriate assessment scale. The various aspects for the selection of a scale are described.

Activities of Daily Living↗
PubMed1997

Detection of hidden metabolites by localized proton magnetic resonance spectroscopy in vivo.

Magnetic resonance spectroscopy (MRS) allows the assessment of chemical substances in living tissue and the detection of biochemical changes associated with certain diseases. In vivo MRS, however, is usually limited in sensitivity and spectral resolution. Many resonance lines originating from metabolites of interest are overlapped by signals of other metabolites and are therefore not visible in conventional MR spectra. In order to overcome this limitation, three localized methods, a technique making use of a spectral difference, a multiple quantum filter technique, and a two-dimensional J-resolved technique, were evaluated theoretically and experimentally for the detection of gamma-aminobutyric acid (GABA) both in vitro and in vivo. All three methods are able to produce the desired results at high metabolite concentrations in vitro. For in vivo measurements the spectral difference method proofed to be most appropriate due to its relatively high sensitivity and its short acquisition time.

Adult↗
PubMed1996

Striatal glucose metabolism and dopamine D2 receptor binding in asymptomatic gene carriers and patients with Huntington's disease.

We used PET scans with the tracers [18F]fluorodeoxyglucose (FDG) and [11C]raclopride (RACLO) to study glucose metabolism and dopamine D2 receptor binding in the caudate nucleus and putamen of 18 carriers of the Huntington's disease gene mutation (10 asymptomatic subjects and eight untreated symptomatic Huntington's disease patients in an early disease stage). We also performed MRI scans and measured the bicaudate ratio (BCR) in the same subjects. Data were compared with those from nine mutation-negative members of Huntington's disease families and separate groups of age matched controls. The PET scans were repeated 1.5-3 years later in six of the asymptomatic gene carriers. Symptomatic Huntington's disease patients showed a marked reduction of FDG and RACLO uptake in the caudate nucleus and putamen and a significant increase of BCR. Asymptomatic mutation carriers revealed significant hypometabolism in the caudate nucleus and putamen. The RACLO binding was significantly decreased in the putamen. Decrements of caudate nucleus tracer uptake, particularly RACLO, correlated significantly with BCR increases in both symptomatic and asymptomatic gene carriers. In asymptomatic carriers, metabolic and receptor binding decreases were also significantly associated with the CAG repeat number but not with the individual's age. Discriminant function analysis correctly classified clinical and genetic status in 24 of 27 subjects on the basis of their striatal PET values (83% sensitivity and 100% specificity). Three asymptomatic mutation carriers were classified/grouped together with mutation-negative subjects, indicating that these individuals had normal striatal RACLO and FDG uptake. Follow-up PET data from gene-positive subjects showed a significant reduction in the mean striatal RACLO binding of 6.3% per year. Striatal glucose metabolism revealed an overall non significant 2.3% decrease per year. These data indicate that asymptomatic Huntington's disease mutation carriers may show normal neuronal function for a long period of life. These findings also suggest that it may be possible to predict when an asymptomatic gene carrier will develop clinical symptoms from serial PET measurements of striatal function.

Adult↗
PubMed1995

[Cardiovascular diseases, cognitive abilities and quality of life in old age].

Dementia is the most important disorder endangering and impairing quality of life in old age. Cardiovascular diseases as well as cardiovascular risk factors raise the risk for dementia; therefore, a targeted primary and secondary prevention strategy is indicated, also in view of the maintenance of autonomy and quality of life. Consequent primary and secondary prevention comprises adequate therapy of risk factors, including pharmacotherapy, if necessary. Important general measures are regular physical and mental training, complemented by an alimentation with a favorable composition of lipids and rich in micronutrients (in particular antioxidants).

Aged↗
PubMed1995

A fluid dynamic analysis using flow visualization of the Baylor/NASA implantable axial flow blood pump for design improvement.

The Baylor/NASA Axial Blood Flow Pump has been developed for use as an implantable left ventricular assist device (LVAD). The pump is intended as an assist device for either pulmonary or systemic circulatory support for more than 3-months' duration. To date the pump provides acceptable results in terms of thrombus formation and hemolysis (IH of 0.018 g/100 L). A fluid dynamics analysis using flow visualization was performed to investigate the flow fields and to determine areas within the pump that could be improved. These studies focused upon the inflow area in front of the pump. A prototype axial flow pump assembly was constructed to facilitate the flow visualization studies. Particle image tracking velocimetry techniques were used to measure Amberlite particles suspended in a blood analog fluid composed of 63% water and 37% glycerin. This method used a pulsed (612 Hz) laser light to determine flow velocity profiles, shear stress, Reynolds numbers, and stagnant areas within the axial pump. These studies showed that the flow straightener (a vaned assembly in the pump inflow) reduced Reynolds numbers from 4,640 to 2,540 (at 8.5 L/min) and that the flow straightener exacerbates a discontinuity found between it and the impeller. Within the inflow area, a maximum of 80 N/m2 shear stress was measured, which is well below published blood damage thresholds. Design variations were investigated resulting in a smoother flow transition between flow straightener and impeller. These variations must be investigated further to establish a correlation with hemolysis and thrombus formation.

Blood Flow Velocity↗