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Biomedical subjects

S Meyer

Publications and source records attributed to S Meyer.

At least 73 records · Page 4Linked to original sources
PubMed2001

Psychogenic paraplegia in a patient with normal electrophysiologic findings.

STUDY DESIGN: A case report of psychogenic paraplegia following a motor vehicle accident was clinically diagnosed using median (MN) and posterior tibial nerves (PTN) somatosensory evoked potentials (SSEPs). OBJECTIVE: To report an unusual case of paraplegia in spite of normal electrophysiological and non-compromising radiographic spine findings. SUMMARY OF BACKGROUND DATA: Conversion disorder with motor system symptoms or deficit is a subtype which includes symptoms such as impaired motor coordination or balance, paraplegia, muscle weakness, difficulty in swallowing, and urinary retention. METHODS: The SSEPs were performed by each PTN at the ankle region behind the medial malleolus or the MN at the wrist using square wave pulses in 15 mA intensity. The SSEPs revealed well-developed somatosensory peaks for all extremities. RESULTS: Well-resolved MN-SSEPs were seen with stimulation of either arm. The principal peaks of N20 and P22 were 17 and 21 ms for both upper extremities. The principal peaks of P37 and N45 were 35 and 46 ms for both lower extremities. No side-to-side latency difference was noted. The MRI scan finding was a non-displaced L1 fracture without spinal canal compromise. CONCLUSIONS: In spite of an apparent paraplegia, contradictory clinical findings, normal neurophysiologic tests, and normal neuroradiologic findings are positive criteria for paraplegia/quadriplegia with psychogenic etiology.

Accidents, Traffic↗
PubMed2001

An experimental and theoretical study of the product distribution of the reaction CH2 (X 3B1) + NO.

Measurements of the product branching ratios of the reaction CH2 (X 3B1) + NO (1) are presented together with calculations of the thermal rate constant and branching ratios using unimolecular rate theory. The reaction was investigated experimentally at room temperature using FTIR spectroscopy. The yields of the main products HCNO and HCN were found to be gamma HCNO = 0.89 +/- 0.06, gamma HCN = 0.11 +/- 0.06. Other minor products could be rationalized by numerical simulations of the reaction system taking into account possible consecutive reactions. The potential energy surface for the reaction was characterized by quantum chemical calculations using ab initio and density functional methods. The proposed reaction pathways connecting reactants to products were explored by multi-channel unimolecular rate theory calculations to determine the CH2 (X) + NO capture rate constant and the rate constants for the different product channels as a function of temperature. The calculated capture rate constant of k = 2.3 x 10(13) cm3 mol-1 s-1 is in good agreement with experimental values at room temperature. Collisional stabilization of the initial H2CNO recombination complex was predicted to be negligible up to pressures of > 1 bar. For ambient pressures and temperatures up to 2000 K, HCNO + H were calculated as the dominating products, with gamma HCNO approximately 0.94 in agreement with the experiments. The channel to HCN + OH was calculated with 0.015 < or = gamma HCN < or = 0.05, only slightly below the experimental value.

Journal Article↗
PubMed2001

Continuous measurements of renal perfusion in pigs by means of intravascular Doppler.

BACKGROUND: Changes in renal blood flow are considered to play a significant role in the induction and maintenance of kidney failure, but are difficult to monitor with currently available techniques. The objective was to validate renal flow measurements with Doppler guidewires and to apply this technique to assess dose and time dependency of the renal vascular effects of norepinephrine (NE). METHODS: In 10 anesthetized pigs, flow velocity in renal arteries (FVart) and veins (FVvein) and volumetric renal blood flow (VBF) were measured before and after intravenous bolus application of incremental doses of NE (2 to 200 microg). RESULTS: FVart curves exactly reflected the changes in VBF. Beat-to-beat analysis revealed a strong linear correlation over a mean VBF range of less than 0.05 to 0.35 L/min (median correlation coefficient with FVart, r = 0.998), and significant but less close relationships were also found between VBF and FVvein. Ten seconds after the administration of 200 microg NE, FVart dropped from 71 to 6 cm/sec and was 90% reversible after 48 seconds. Similarly, the renal vascular resistance temporarily rose from 988 to 13711 mm Hg. min/L. In contrast, NE-induced increases in systemic vascular resistance were on average a maximum of 1.5-fold but persisted for more than 60 seconds. CONCLUSIONS: Doppler flow measurements in the renal artery provide an excellent surrogate of volumetric blood flow, which may be useful for continuous monitoring of renal hemodynamics. The renal vasculature is more sensitive when compared with the systemic vasculature, but also appears to evoke more efficient counter-regulatory mechanisms in response to NE.

Animals↗
PubMed2001

Different expression of cytokine and membrane molecules by circulating lymphocytes on acute mental stress in patients with atopic dermatitis in comparison with healthy controls.

BACKGROUND: Mental stress is believed to induce an exacerbation of atopic dermatitis (AD). Until now, however, only few psychoneuroendocrinologic mechanisms underlying the link between psychological stress and exacerbation or maintenance of AD have been described. OBJECTIVE: Our purpose was to conduct an investigation of immunologic parameters in the form of membrane molecules and cytokines with potential relevance for the cutaneous inflammation in an established psychological laboratory stress model. METHODS: Patients with AD (n = 15) and healthy controls (n = 15) were exposed to mental stress, as described in a previous report. In vitro analyses were completed 1 hour before, immediately after, and 1 hour after mental stress exposure. Lymphocyte subpopulations, the cutaneous lymphocyte-associated antigen (CLA), the membrane molecule CD69(+) (early activation antigen), and intracellular IL-4, IL-5, and IFN-gamma in blood-derived lymphocytes were analyzed by flow cytometry. IL-4 in the supernatant of concanavalin-A-stimulated PBMCs was determined by ELISA. RESULTS: An increase in heart rate and blood pressure was demonstrated during psychological stress in patients with AD and healthy volunteers. We found significantly higher stress-induced increase of CLA(+) lymphocytes, T helper cells expressing IL-5, and both CD4(+) and CD8(+) lymphocytes expressing IFN-gamma on mitogenic stimulation in patients with AD in comparison with healthy controls. In addition, we observed an earlier increase in the secretion of IL-4 in the supernatant of mitogen-stimulated lymphocytes during psychological stress in patients with AD in comparison with healthy volunteers. CONCLUSION: A higher stress-induced increase of CLA(+) cells in the circulation in patients with AD compared to healthy controls might indicate an increased ability of T lymphocytes in AD to migrate to the skin during this psychological condition. In addition, the data of this study suggest a different stress-induced cytokine profile in circulating lymphocytes in patients with AD compared to healthy controls.

Adolescent↗
PubMed2001

Overwintering cost associated with resistance to transgenic cotton in the pink bollworm (Lepidoptera: Gelechiidae).

Fitness costs associated with resistance to transgenic crops producing toxins from Bacillus thuringiensis (Bt) may have important effects on the evolution of resistance. We investigated overwintering costs in pink bollworm, Pectinophora gosypiella (Saunders), strains with different degrees of resistance to Bt cotton. Frequency of resistant individuals in a strain was not associated with induction of diapause or emergence from diapause in early winter. Emergence from diapause in the spring was 71% lower in three highly resistant strains than in two heterogeneous strains from which the resistant strains were derived. This underestimates the overwintering cost because the frequency of the resistance allele was relatively high in the heterogeneous strains. Emergence in the spring in hybrid progeny from crosses between the resistant and heterogeneous strains was greater than in resistant strains but did not differ from susceptible strains, showing that the overwintering cost was recessive to some extent.

Animals↗
PubMed2001

Effects of receptor-selective retinoids on CYP26 gene expression and metabolism of all-trans-retinoic acid in intestinal cells.

Retinoids mediate most of their function via interaction with retinoid receptors [retinoic acid receptors (RARs) and retinoid X receptors (RXRs)], which act as ligand-activated transcription factors controlling the expression of a number of target genes. The complex mechanistic pattern of retinoid-induced effects on gene expression of CYP26 and intestinal metabolism of all-trans-retinoic acid (RA) was investigated here by studying the effects of retinoid ligands with relative selectivity for binding and transactivation of the retinoid acid receptors, RARs and RXRs, in human intestinal Caco-2 cells. We show here that CYP26 is expressed in human duodenum and colon. In Caco-2 cells not only all-trans-RA but also synthetic agonists of the RAR induced intestinal CYP26 gene expression and all-trans-RA metabolism as well. The RARalpha ligand Am580 induced the CYP26 gene expression more than the RARbeta ligand CD2019 or the RARgamma ligand CD437 suggesting the highest specificity for RARalpha on intestinal CYP26 gene regulation. RXR ligands alone did not induce CYP26 gene expression or RA metabolism in Caco-2 cells at all. But together with the RARalpha ligand, Am580, there were enhanced effects on the induction of CYP26 gene expression and on the induction of the metabolism of all-trans-RA. We conclude that gene regulation of CYP26 and the metabolism of all-trans-RA in intestinal cells is regulated through RXR and RAR heterodimerization. When coadministered, RAR agonists showed the highest potency for CYP26 gene regulation. Receptor-selective retinoids showed enhanced effects on induction of CYP26 gene expression and all-trans-retinoic acid metabolism.

Caco-2 Cells↗
PubMed2001

Novel short-acting A2A adenosine receptor agonists for coronary vasodilation: inverse relationship between affinity and duration of action of A2A agonists.

Several potent and selective A2A adenosine receptor agonists are currently available. These compounds have a high affinity for the A2A receptor and a long duration of action. However, in situations where a short duration of action is desired, currently available A2A receptor agonists are less than ideal. From a series of recently synthesized A2A receptor agonists, two agonists (CVT-3146 and CVT-3033) with low affinity were selected for further characterization as selective and short-acting coronary vasodilators. Both compounds were selective for the A2A adenosine receptor (AdoR) versus the A1, A2B, and A3AdoR in binding and functional studies. CVT-3146 and CVT-3033 appeared to be weak partial agonists to cause cAMP accumulation in PC12 cells, but were full and potent agonists to cause coronary vasodilation, a response that has a very large A2A receptor reserve. However, the durations of action of CVT-3146 and CVT-3033 were remarkably shorter than those of the high-affinity agonists CGS21680 or WRC0470, presumably due to the relative lower affinity of CVT-3146 and CVT-3033 for the A2A receptor. Indeed, an inverse relationship was found between the affinity of the various agonists for the A2A receptor and the duration of their actions. These data indicate that low-affinity agonists can produce a response that is of equivalent magnitude but more rapid in termination than that caused by a high-affinity agonist. Hence, the low-affinity A2A agonists CVT-3146 and CVT-3033 may prove to be superior to currently available high-affinity agonists as coronary vasodilators during myocardial imaging with radionuclide agents.

Adenosine↗
PubMed2000

Potent in vitro methicillin-resistant Staphylococcus aureus activity of 2-(1H-indol-3-yl)quinoline derivatives.

A novel structural class of antibacterials, 2-(1H-indol-3-yl)quinolines, effective against methicillin-resistant Staphylococcus aureus (MRSA), was discovered from a combinatorial library. A structure-activity relationship (SAR) study was conducted to determine the pharmacophore and increase the potency of these compounds. Compounds were prepared that had minimum inhibitory concentrations (MICs) < 1.0 microg/mL against MRSA and retained activity against two strains of glycopeptide intermediate-resistant S. aureus (GISA).

Anti-Bacterial Agents↗
PubMed2000

Effect of seated posture on interface pressure in children who are able-bodied and who have myelomeningocele.

PURPOSE: The objective of this study was to investigate the relationship between sitting position and interface pressure distribution in seated children. METHOD: Fifteen able-bodied children and 15 children with myelomeningocele complete paraplegia, aged 7 to 18 years were included in the study. The body-seat interface pressure was measured with the QA pressure measurement system. Four sitting positions typically used to reduce body-seat interface pressure position (recline, tilt, combined and lean forward) were compared to a neutral position. RESULTS: Test/re-test Pearson correlation coefficients were greater than 0.94 for maximum pressure and greater than 0.88 for mean pressure at all test positions (p < 0.0001) and, for the risk area (defined as the percentage of sensors which recorded pressures greater than 40 mm Hg.) varied from 0.62 to 0.85 (p < 0.0005). Maximum pressures for the myelomeningocele group were significantly higher than those recorded for able-bodied subjects in the neutral, combined and lean forward positions (p < 0.001). For the able-bodied subjects, maximum pressures at the combined (p < 0.001), tilt (p < 0.05) and lean forward (p < 0.0001) positions were significantly lower than those measured at the neutral position. For the myelomeningocele subjects, maximum pressure at all tested positions was significantly lower than at the neutral position (p < 0.05). CONCLUSIONS: The results point to the importance of measuring body-seat interface pressure for each wheelchair user and of using the information to customize wheelchair utilization.

Adolescent↗
PubMed2000

Global analysis of gene expression in cells of the immune system II. Cell-free translation products and high-density filter hybridization data.

We have developed an experimental system for linking information on cell-free transcription and translation products from cDNA clones with data obtained from hybridization signals from complex probes. The work described in this paper consists of two distinct processes, one being the construction of a system of clonal addresses and the other the identification of expressed genes involved in the studied processes. We describe the use of this system to identify genes involved in thymus development. Complex probes from fetal thymuses (GD15, 17 and newborn) of Balb/c mice were used to identify genes, which are up- or downregulated during the process of differentiation. The full set of information is available in the Clone-base of the Basel Institute for Immunology and will be retrievable from the website of the collaborating laboratories.

Animals↗
PubMed2000

Torque transmission between square wire and bracket as a function of measurement, form and hardness parameters.

The aim of the study was to investigate the influence of cross section, edge geometry and structural hardness on torque transmission between square wire and bracket. For this purpose, 5 different brands of stainless steel square wire in 3 dimensions (0.016" x 0.016", 0.016" x 0.022" and 0.017" x 0.025") were inserted into edgewise brackets with a slot size of 0.018" and loaded with different torques (1 and 3 Ncm). The slot and wire geometries were analyzed by computer on ground specimens before and after loading. In addition, the Vickers hardness and micro-hardness of the unstressed and stressed metal surfaces were determined. While the slot size was very accurately maintained, the wire dimensions deviated downwards by an average of 10%. Torque transmission led to notching and bending-up phenomena on the bracket slot flanks. A torque loading of 3 Ncm increased the torque play of 0.016" x 0.022" wires by 3.6 degrees, and of 0.017" x 0.025" wires by 3.7 degrees. In the case of 0.016" x 0.016" wires, an effective torque transmission was no longer possible. The average Vickers hardness of the wires was 533 kp/mm2, and that of the brackets 145 kp/mm2. The micro-hardness in the deformation area of stressed internal slot walls increased with increasing load transmission from 204 to 338 kp/mm2. As a result of excessively small wire dimensions and plastic deformation of the brackets, a relatively large torque play occurs. Deformation and notching in the area of the internal slot walls are inconsistent with demands for recycling brackets. A standardization of bracket wire systems stating the actual torque play would be desirable.

Hardness↗
PubMed2000

Pseudosarcoma of the bladder associated with residual urachus in a 3-year-old girl.

Bladder pseudosarcoma or pseudosarcomatous myofibroblastic proliferation (PMP) is a rare but nevertheless very important differential diagnosis of any bladder mass. In childhood most such masses are usually malignant soft-tissue sarcomas, and distinction from these is therapeutically crucial. To date no aetiological factor for PMP has been identified in children, and treatment is limited to surgical intervention with no role for chemotherapy or radiotherapy. We report clinical, anatomical, and histological findings in a 3-year-old girl with a pseudosarcoma of the urinary bladder associated with a residual urachus, suggesting this as the originating tissue.

Child, Preschool↗
PubMed2000

[Technology in residences for support of a self-determined life style for the elderly. The research project "sentha" and initial results of a social science project].

Sentha is an interdisciplinary research team involving the Technical University Berlin, the Berlin Institute for Social Research GmbH (BIS), the German Centre for Research on Ageing at the University of Heidelberg (DZFA), the School of Fine Arts Berlin (HdK), and the Brandenburg Technical University Cottbus (BTU). Building on empirical investigations of the role of everyday household products in the everyday life of older people, product-independent design and assessment guidelines and new products are being developed in an intensive interdisciplinary process in order to better meet the needs of older people and to enhance their autonomous living. The following paper describes the contributions from the participating disciplines and presents initial results of the social sciences subproject, describing the problems arising in living independently in old age and detecting the demands on new technological solutions. Data are based on a representative survey conducted in 1999 and including a stratified sample of 1417 men and women aged 55 and older.

Activities of Daily Living↗
PubMed2000

Effects of heterocyclic PAHs (N, S, O) on the biodegradation of typical tar oil PAHs in a soil/compost mixture.

The interaction phenomena during the biodegradation of typical coal tar polycyclic aromatic hydrocarbons and their heterocyclic analogues (N, S, O) were investigated in an artificially contaminated AhA1-horizon/compost mixture. All compounds were partly or completely biodegraded. Degradation of two- to five-ring PAHs was inhibited by the presence of hetero-PAHs, whereas degradation of just some hetero-PAHs was inhibited by the presence of PAHs. Among the hetero-PAHs the sulphur-containing compounds were less susceptible to degradation than the corresponding oxygen- or nitrogen-containing analogues. The basic azaarene acridine showed an extreme persistence and strong sorption to the soil matrix proved by an increase of recovery after saponification of the soil matrix.

Biodegradation, Environmental↗
PubMed2000

Concepts of trust among patients with serious illness.

This paper examines conceptions of trust among three groups of respondents diagnosed with either breast cancer, Lyme disease or mental illness. Interviews were carried out using an open-ended interview guide to explore how patients made assessments of trust in their doctors and health care plans. The guide followed a conceptual approach that asked questions about competence, agency/fiduciary responsibility, control, disclosure and confidentiality. Respondents were given ample opportunity to raise other areas of concern. The data were organized using the NUDIST software package for the analysis of non-numerical and unstructured qualitative data. Patients viewed trust as an iterative process and commonly tested their physicians against their knowledge and expectations. Interpersonal competence, involving caring, concern and compassion, was the most common aspect of trust reported, with listening as a central focus. Most patient comments referred to learnable skills and not simply to personality characteristics. Technical competence also received high priority but was often assessed by reputation or interpersonal cues. Patients were much concerned that doctors be their agents and fight for their interests with health care plans. Disclosure and confidentiality were less common concerns; most patients anticipated that doctors would be honest with them and respect their confidences. Patients' responses also appeared to vary by their disease, their socio-demographic characteristics, their involvement with self-help groups, and how their illness conditions unfolded.

Adult↗
PubMed2000

Donor bone marrow from a sibling with inborn error of metabolism for treatment of acute leukaemia - clinical and biochemical consequences in the non-affected recipient.

Bone marrow transplantation (BMT) is increasingly used in an attempt to correct inborn errors of metabolism (IEM). However, little is known about effects of BMT from patients with IEM donating for non-affected recipients. We present data from a 8.5-year-old girl who underwent BMT in second remission for relapsed acute lymphoblastic leukaemia (ALL) at the age of 7 years from her HLA-identical brother who was severely affected by Hunter syndrome (Mucopolysaccharidosis type II, iduronate-2-sulphatase (IDS) deficiency). After BMT not only leukocyte but also plasma activity of IDS was absent. Mixing experiments and immunoadsorption suggest antibody-mediated enzyme inhibition. However, her urinary glycosaminoglycan excretion has not increased post BMT and clinical signs of mucopolysaccharidosis are absent 20 months after BMT. We conclude that patients with white cell enzyme deficiencies and other IEMs do not have to be excluded from bone marrow donation. Antibody production by the graft may occur and be reflected by a marked reduction in plasma enzyme levels but not tissue activity. Similar antibody responses resulting in enzyme inactivation might also affect other enzyme replacement strategies for individuals with IEM.

Acute Disease↗