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Biomedical subjects

J Meyer

Publications and source records attributed to J Meyer.

At least 19 recordsLinked to original sources
PubMed2007

No evidence for preferential transmission of common valine allele of the Val66Met polymorphism of the brain-derived neurotrophic factor gene (BDNF) in ADHD.

Attention deficit/hyperactivity disorder (ADHD) is a highly heritable common neurodevelopmental disorder with onset in childhood. A coding SNP (rs6265, Val66Met) of the brain-derived neurotrophic factor gene (BDNF) has recently been associated with ADHD. More specifically, paternal over-transmission of the common Val66 allele to affected children had been observed. We aimed to confirm these findings in a large, sufficiently powered, and well characterized German ADHD family sample. The Val66Met polymorphism of BDNF was genotyped in 294 families comprising one or more affected sibs (468 children). Contrary to previous reports, we did not observe over-transmission of the common Val66 allele, from either parent to affected children. We did not find support for an involvement of the Val66 allele of the Val66Met polymorphism of BDNF in the pathogenesis of ADHD in our sample.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

Thiol and thiolate bond formation of ferrocene-1,1-dithiol to a Ag(111) surface.

Using density functional calculations, we show that the adsorption of ferrocene dithiol on the Ag(111) surface is remarkably flexible, i.e., a large number of different configurations have binding energies that differ by less than 0.1 eV per molecule. The thiolate bond is slightly favored over the thiol bond (by less than 0.1 eV) but may not be formed due to considerable activation barriers. Electronically, we found that the thiolate bound molecule is conducting, whereas thiol bonds turn it into semiconducting.

Journal Article↗
PubMed2006

Bacterial contamination of filtered intraoral bone chips.

Intraoral bony defects can be filled with bony particles that are collected in a titanium filter. The aim of this study was to determine quantitatively and qualitatively the degree of this contamination. Over a period of 3 months, bony particles were collected from 50 patients undergoing oral surgery. The bony particles were scraped off the filter, resuspended, and incubated aerobically and anaerobically on human blood agar media. Colony forming units (CFU) were determined as well as the most common species of bacteria. All samples showed anaerobic and aerobic growth. After anaerobic incubation in 44 samples the number of bacteria was higher (38) or equal (six) to that after aerobic incubation. On average, 435,000 CFU (aerobic) and 1,013,000 CFU (anaerobic) per sample were found. The most frequently identified bacteria belonged to Veillonella spp. in the anaerobic and to Streptococcus oralis in the aerobic cultures. In 43 samples black-pigmented colonies were detected. Only bacteria common in the oral cavity were identified. Prophylactic antibiotic therapy may be indicated when using filtered bony particles for intraoral augmentation procedures.

Adolescent↗
PubMed2006

High-throughput sample handling and data collection at synchrotrons: embedding the ESRF into the high-throughput gene-to-structure pipeline.

An automatic data-collection system has been implemented and installed on seven insertion-device beamlines and a bending-magnet beamline at the ESRF (European Synchrotron Radiation Facility) as part of the SPINE (Structural Proteomics In Europe) development of an automated structure-determination pipeline. The system allows remote interaction with beamline-control systems and automatic sample mounting, alignment, characterization, data collection and processing. Reports of all actions taken are available for inspection via database modules and web services.

Data Collection↗
PubMed2006

[Acetylsalicylic acid does not alter the mechanoelectrical transduction of mammalian outer hair cells in vitro].

BACKGROUND: High doses of acetylsalicylic acid (ASS) induce tinnitus and hearing loss. This ototoxic side effect of ASS is characterized by a decrease in spontaneous and evoked otoacoustic emissions. A decrease in otoacoustic emissions is found not only in mammals, but also in non-mammalian ears without electromotile outer hair cells. The molecular mechanism underlying ASS ototoxicity seems to be competitive binding to and a block of the motor molecule prestin. In non-mammalian species, ASS ototoxicity is possibly explained by an effect on the hair bundle. RESULTS: The present data from the outer hair cells of the adult guinea pig cochlea show a reduction in the membrane capacitance by maximally 42%, probably as a result of ASS binding competitively to the motor molecule. However, spontaneous and evoked receptor currents were not modulated by ASS. CONCLUSION: The results suggest an influence of ASS on outer hair cell somatic electromotility, without a concomitant effect on hair-bundle function.

Animals↗
PubMed2006

Structural variation of the monoamine oxidase A gene promoter repeat polymorphism in nonhuman primates.

By conferring allele-specific transcriptional activity on the monoamine oxidase A (MAOA) gene in humans, length variation of a repetitive sequence [(variable number of tandem repeat (VNTR)] in the MAOA promoter influences a constellation of personality traits related to aggressive and antisocial behavior and increases the risk of neurodevelopmental and psychiatric disorders. Here, we have analyzed the presence and variability of this MAOA promoter repeat in several species of nonhuman primates. Sequence analysis of MAOA's transcriptional control region revealed the presence of the VNTR in chimpanzee (Pan troglodytes), bonobo (Pan paniscus), gorilla (Gorilla gorilla), orangutan (Pongo pygmaeus), rhesus macaque (Macaca mulatta) and Gelada baboon (Theropithecus gelada). The majority of P. troglodytes and P. paniscus showed a single repeat with a sequence identical to the VNTR sequence in humans. In contrast, analyses of the remaining species revealed shorter sequences similar to the first 18 bp of human VNTR. Compared with other nonhuman primates, the VNTR sequence of M. mulatta showed the highest length variability with allele frequencies of 35, 25 and 40% for the five, six and seven repeat variants, respectively. The extent of variability of the MAOA promoter repeat in both rhesus monkeys and humans supports the notion that there may be a relationship between functional MAOA expression and aggression-related traits in humans and rhesus macaque populations.

Animals↗
PubMed2006

Clinical, laboratory, and histopathologic features of equine lymphoma.

Clinical, laboratory and tissue findings from 37 horses with lymphoma were investigated. Horses ranged in age from 0.3 to 20.5 years (median 5.0 years) and included 18 females and 19 males. Weight loss (n = 25) and ventral edema (n = 21) were the most common historical and physical abnormalities. The most common laboratory abnormalities were hyperfibrinogenemia (n = 26), hypoalbuminemia (n = 19), anemia (n = 19), leukemia (n = 14), hyperglobulinemia (n = 13), and thrombocytopenia (n = 13). Thirty-four tumors involved multiple lymphoid tissues and abdominal or thoracic organs, and 3 tumors were restricted to cutaneous and subcutaneous sites. Histopathologically, all tumors diffusely effaced normal lymph node architecture. Tumor cell morphology was heterogeneous in 17 tumors, and 8 tumors had marked histiocytic and multinucleated giant cell infiltrates. Extensive necrosis or focal fibrosis was present in 22 and 4 lymphomas, respectively. Staining of tumor sections with antibodies against CD3 and CD79alpha molecules resulted in classification of T-cell (n = 26) or B-cell (n = 7) origin. Four tumors could not be classified. Most T-cell tumors comprised small to medium CD3(+) lymphocytes, whereas 5 of 7 B-cell tumors were infiltrated by numerous small T lymphocytes and classified as T-cell-rich B-cell lymphoma. Neither estrogen nor progesterone receptor expression was consistently identified by immunochemical assessment of tumor tissues. Fresh tumor cells from 6 horses bound antibodies reactive with equine CD4, CD5, CD8, CD21, or major histocompatibility class II molecules, confirming T-cell (n = 5) or B-cell origin (n = 1). These findings suggest that T-cell lymphoma is more common than B-cell lymphoma in horses and that inflammation, possibly from tumor cytokine production, is frequent.

Animals↗
PubMed2006

Efficacy of intramammary infusion of ceftiofur hydrochloride at drying off for treatment and prevention of bovine mastitis during the nonlactating period.

This study evaluated the efficacy of intramammary infusion of ceftiofur hydrochloride for the treatment of intramammary infections present at the last milking of lactation and for prevention of new intramammary infections during the nonlactating period. Cows were randomly assigned to five treatments (untreated negative control, 125, 250, and 500 mg of ceftiofur, and a positive control group receiving 300 mg cephapirin benzathine). A dose of 125 mg of ceftiofur per mammary quarter was effective for treatment of existing infections present at the time of milk cessation, but only the 500-mg dose of ceftiofur per mammary quarter was effective for both treatment of existing intramammary infections at the time of milk cessation and for prevention of new intramammary infections during the nonlactating period.

Animals↗
PubMed2005

No causative DLL4 mutations in periodic catatonia patients from 15q15 linked families.

Two well-supported theories of schizophrenia pathogenesis are the neurotransmitter theory and the neurodevelopmental theory, suggesting, respectively, that dysregulation of neurotransmitter signaling and abnormal brain development are causative in this disease. The strongest evidence of neurotransmitter involvement are suggestions of abnormal dopamine signaling in the prefrontal cortex and one of the strongest indications of developmental abnormalities contributing to this disease is an inverse layering of the prefrontal cortex. These two theories of schizophrenia pathogenesis can be united by their involvement of the prefrontal cortex, where structural abnormalities could lead to neurochemical abnormalities. Accordingly, any gene expressed in the prefrontal cortex of developing brains is a functional candidate for schizophrenia. We have previously reported strong linkage to 15q15 (LOD = 3. 57; P = 2.6 x 10(-5)) in a collection of German multiplex families segregating the periodic catatonia subtype of schizophrenia in a nearly Mendelian fashion. A gene within our 15q15 linkage region, DLL4, is expressed in developing forebrain and produces a NOTCH4 ligand. Variants of NOTCH4 are associated with schizophrenia, thus DLL4 is both a functional as well as a positional candidate for schizophrenia. We screened this gene for mutations in three affected individuals and two unrelated controls and found two previously unreported SNPs, one non-synonymous polymorphism that changed an arganine to a histadine in Exon 7 and one synonymous polymorphism in exons. The non-synonymous SNP is a rare variant in that it was not found in 100 control chromosomes; however, it did not cosegregate with the disease in the extended family so it is not causative in this pedigree. It is unlikely that mutations in DLL4 are causative in this collection of families with linkage to 15q15.

Adaptor Proteins, Signal Transducing↗
PubMed2005

[Resection arthroplasty of the carpometacarpal joint of the thumb - results of 132 cases].

BACKGROUND: Resection arthroplasty of the carpometacarpal joint of the thumb is considered to be the most frequently used surgical treatment for arthrosis of the trapeziometacarpal joint. To avoid proximalisation and to improve stability of the first metacarpal, tendon-sling resectional arthroplasties have gained general approvement. To further simplify surgery, we have used a surgical technique since 1995, that consists in a fixation of the first metacarpal with local capsular tissue. METHOD AND CLINICAL MATERIAL: From 2000 to 2001, 152 resections of the trapezium were performed in 147 patients with arthrosis of the first carpometacarpal joint. 48 surgical procedures included a tendon-sling arthroplasty; in 104 cases stabilisations of the first metacarpal were achieved by fixing local radiopalmar capsular tissue to the flexor-carpi-radialis tendon. After a mean follow-up of 30 months (18 to 41 months), patients were asked to complete a questionnaire concerning pain, physical strength, practical skills, maximal physical capacity and aesthetic result. The general surgical result had to be scored and the recovery time until the thumb could be used for activities of daily living had to be recorded. RESULTS: 132 of 152 questionnaires, 43 of the patients with tendon-sling arthroplasty and 89 of the patients with arthroplasty with local radiopalmar capsular tissue, were returned. After tendon-sling arthroplasty, 69.8 % of the patients judged their results to be good or very good, after stabilisation with radiopalmar capsular tissue 69.7 % of the patients valued their surgical results good or very good. Unsatisfactory results were found in 18.6 % of the patients after tendon-sling arthroplasty and in 19.1 % of the patients after stabilisation with radiopalmar capsular tissue. The thumb could be used for every-day life after a mean time of 6.7 months. There was no significant difference between the operative procedures. CONCLUSION: The collected data implies that resection-arthroplasty of the carpometacarpal joint of the thumb with stabilisation by radiopalmar capsular tissue yields similar results compared to tendon-sling arthroplasty.

Activities of Daily Living↗
PubMed2005

Automatic selection of non-coplanar beam directions for three-dimensional conformal radiotherapy.

An algorithm is described, based on ray-tracing and the beam's-eye-view, that exhaustively searches all permitted beam directions. The evaluation of the search is based on a general cost function that can be adapted to the clinical objectives by means of parameters and weighting factors. The approach takes into account the constraints of the linear accelerator by discarding beam directions that are not permitted. A sensitivity analysis was carried out to determine appropriate parameters for different sized organs, and a prostate case was used to benchmark the approach. The algorithm was also applied to two clinical cases (brain and sinus) to test the benefits of the approach compared with manual angle selection. The time to perform a beam direction search was approximately 2 min for the coplanar and 12 min for the non-coplanar beam space. The angles obtained for the prostate case compared well with reports in the literature. For the brain case, the mean dose to the right and left optic nerves was reduced by 12% and 50%, respectively, whilst the target dose uniformity was improved. For the sinus case, the mean doses to the right and left parotid glands were reduced by 54% and 46%, respectively, to the right and left optic nerves by 37% and 62%, respectively, and to the optic chiasm by 39%, whilst the target dose uniformity was also improved. For the clinical cases the plans based on optimized beam directions were simpler and resulted in better sparing of critical structures compared with plans based on manual angle selection. The approach provides a practical alternative to elaborate and time consuming beam angle optimization schemes and is suitable for routine clinical usage.

Adenocarcinoma↗
PubMed2004

[S2 guideline for infectious endocarditis].

Microbe-induced (infectious) endocarditis is an endovascular infection, caused mainly by bacteria, of cardiovascular structures. The major predilection site are the native heart valves, but involvement of implanted intracardiac foreign material is increasingly being seen. The mortality rate of infectious endocarditis depends on clinical factors and the causal agent, but also on the time of the establishment of the diagnosis and the initiation of appropriate treatment. In Germany, the current mortality rate ranges up to 18%. Between January 2003 and July 2004, with the aim of improving patient care and thus the outcome of this condition, a guideline commission worked out recommendations for the diagnosis, treatment and management of the disease for the use of general practitioners and hospital physicians, in particular microbiologists, infectiologists, cardiologists and cardiac surgeons. The basis for this guideline was the systematic search through the literature of the European guideline. On the 16th and 28th of June 2004, the entire guideline was formerly approved in a nominal group process.

Anti-Bacterial Agents↗
PubMed2004

Organophosphate flame retardants and plasticisers in wastewater treatment plants.

Previous studies have revealed that chlorinated and non-chlorinated organophosphorous flame retardants and plasticisers are important contaminants in German surface waters and it has been demonstrated that wastewater treatment plants contribute to the emission of these substances. In this study temporal development as well as elimination efficiency were determined in two wastewater treatment plants (STP) in the Ruhr/Rhine area at different stages of the wastewater treatment process. The samples were analysed for the non-chlorinated organophosphate esters tri-n-butylphosphate (TnBP), tri-iso-butylphosphate (TiBP), tris-(butoxyethyl)-phosphate (TBEP) and triphenylphosphate (TPP) and the chlorinated organophosphate esters tris-(2-chloro, 1-methylethyl)-phosphate (TCPP), tris-(2-chloro-, 1-chloromethylethyl)-phosphate (TDCP) and tris-(2-chloroethyl)-phosphate (TCEP). The study showed that there were significant differences in the elimination of chlorinated and non-chlorinated organophosphorous flame retardants. The elimination rates ranged from 57-86% for TiBP, TnBP and TBEP at both STP's. No elimination of the chlorinated flame retardants TCPP, TDCP and TCEP was observed in any of the sampled STPs. At both STPs the first treatment steps and the final filtration did not contribute to the elimination of the non-chlorinated organophosphorous flame retardants while the aeration step did. At both STPs the efficiency of the cleaning process concerning the flame retardants was comparable. Thus the type of construction of the STP was not relevant for the elimination of these substances. Additionally a strong day-to-day variation was observed, while in one STP a temporal trend for TCPP during the week was found.

Environmental Monitoring↗
PubMed2004

Effect of rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins in vitro.

The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation because it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins by human bone-derived cells (HBDCs) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were alpha-TCP, two materials with a crystalline phase Ca(2)KNa(PO(4))(2) and with a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9), and a calcium phosphate bone cement (material denominated Biocement D). HBDCs were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. In the presence of GB14 and Biocement D specimens cell proliferation was reduced and cell differentiation increased. At day 21, the greatest number of cells was found on GB9 expressing significantly higher levels of bone-related proteins than cells grown on all other surfaces. Because all novel materials facilitated the expression of the osteoblastic phenotype at least as much as TCP and the polystyrene control, these biomaterials can be regarded as excellent candidate bone substitute materials. GB9 induced the highest proliferation and cellular differentiation after 21 days of incubation, suggesting that this material may possess a higher potency for enhancing osteogenesis than TCP.

Adolescent↗
PubMed2004

Segmental nerve conduction velocity in vibration-exposed shipyard workers.

OBJECTIVES: Segmental sensory nerve conduction velocity (SNCV) was measured from the wrists to the hands and digits of a population of vibration-exposed shipyard workers. This study was designed to investigate whether SNCV was selectively slowed in the fingers and whether a laboratory approach could be adapted for robust field use. METHODS: Wrist-palm, palm-proximal digit, and digital segments were determined from stimulation at the wrist with recording electrodes placed distally and adjusted to individual anatomy. The cohort was selected on the basis of current use of vibratory tools. RESULTS: Wrist-palm and digital segments were slower than palm-proximal digit segments for dominant and non-dominant hands and for both ulnar and median nerves. In the dominant-hand median nerve of participants with current exposure, the SNCV was 41.4 m/s (SD 8.0) for the wrist-palm segment, 50.8 (SD 9.5) for the palm segment, and 42.1 m/s (SD 9.3) for the digital segment. Temperature had an important effect on nerve conduction velocity but not equally across segments. Other explanatory variables had modest effect on SNCV. CONCLUSIONS: Reduced SNCV in the digits may be a consequence of industrial exposure to vibration. Each sensory nerve segment appeared to have a different characteristic velocity and different pattern of association with skin temperature. There are differences between median and ulnar nerve segments, with potentially important consequences when standard distances are used to assess wrist-digit velocity.

Carpal Tunnel Syndrome↗
PubMed2004

[Carotid stenosis concomitant to coronary artery disease].

Carotid stenosis is frequent in patients with coronary artery disease (CAD). In the literature, 9-28% of patients with CAD have additional carotid artery stenosis, predictors of which are advanced age, smoking, diabetes mellitus, arterial hypertension, coronary multivessel disease, and peripheral arterial disease. Moreover, patients with unstable coronary syndromes and those with elevated inflammatory markers such as C-reactive protein or fibrinogen more often have concomitant CAD and carotid artery stenosis. The long-term prognosis of these patients is worse than with CAD only. Therefore, patients with CAD should be screened for additional carotid artery stenosis, especially if coronary artery bypass grafting is planned. Continuous wave Doppler sonography and color-coded duplex sonography are suitable methods to screen for carotid artery stenosis.

Carotid Artery, Internal↗