Biomedical subjects

J Meyer

Publications and source records attributed to J Meyer.

At least 127 records · Page 7Linked to original sources

PubMed2001

Effects of warning validity and proximity on responses to warnings.

The effects of a warning's validity and display characteristics on the responses to binary warnings were studied in a categorization task that resembled the control of a simulated production environment. Students performed a visual signal detection task and were aided by a binary warning indicator. Experimental conditions differed in the validity of the warning and its proximity to the judged stimulus. Participants' performance improved over the course of the experiment, and they partly adjusted their responses to the validity of the warnings but continued to respond to nonvalid warnings throughout the experiment. It was particularly difficult to ignore the nonvalid information when it was integrated with the continuous information. There was evidence for nonoptimal use of the information from the warning system, whether it was valid or not valid. The results indicate a possible distinction between two dimensions of users' trust in warning systems: compliance and reliance. Actual or potential implications of this research include improved warning design based on analysis of system and operator characteristics.

Analysis of Variance↗

PubMed2001

Use of warnings in an attentionally demanding detection task.

The study assessed the use of binary warnings in a detection task with high attentional demands. Participants in the experiment had to decide whether to continue or halt production based on a briefly displayed number that indicated a temperature level. The short time that the number was displayed required that participants focus on the display area. Participants were rewarded for production when the system was intact and were heavily penalized for decisions to produce under dangerous temperature levels. Color-coded warning cues (green for safe, red for danger) were displayed to the participants prior to number presentation. The experimental conditions differed in the validity of the cue and in the probability of red cues. Results showed significant learning for all conditions. Participants tended to ignore the nonvalid and low-validity cues and rely only on highly valid cues. However, the mere existence of cues affected participants' general tendency to take risks. Actual or potential applications of this research include improving systems that require operators to devote attention to complex tasks while receiving and responding to warnings.

Adolescent↗

PubMed2001

A gene conferring susceptibility to type 2 diabetes in conjunction with obesity is located on chromosome 18p11.

Genome-wide nonparametric linkage analysis of 480 sib-pairs affected with type 2 diabetes revealed linkage to a previously unreported susceptibility locus on chromosome 18p11. This result improved with stringent subphenotyping using age- and sex-adjusted BMI, ultimately reaching a logarithm of odds of 3.82 (allele sharing 0.6654) at a point between markers D18S976 and D18S391 when the most obese 20% of the sample was analyzed. Several genes on chromosome 18 have been suggested as metabolic disease candidates, but none of these colocalize with our linkage result. We conclude that our results provide support for the presence of a currently uncharacterized gene on chromosome 18p, certain alleles of which confer increased susceptibility to type 2 diabetes in conjunction with obesity. We additionally observed moderate evidence for linkage to chromosome 1, near marker D1S3462; chromosome 4, near marker D4S2361; chromosome 5, near marker D5S1505; and chromosome 17, near marker D17S1301.

Adult↗

PubMed2001

A genome scan for type 2 diabetes susceptibility loci in a genetically isolated population.

A total of 896 individuals of Ashkenazi Jewish descent were ascertained in Israel from 267 multiplex families, including 472 sib-pairs affected with type 2 diabetes. A genome-wide scan with average marker spacing of 9.5 cM revealed five regions on four chromosomes (4q, 8q, 14q, and 20q) that exhibited nominal evidence for linkage (P < 0.05). The highest observed nonparametric linkage Z score was 2.41 (equivalent to a logarithm of odds score of 1.26) at marker D4S1501. A maximal signal, with a Z score of 2.05, was observed on chromosome 20 near marker D20S195, and another on 20p near marker D20S103 (Z 1.80). A single marker on chromosome 8 (D8S593) and two adjacent markers on chromosome 14 (D14S749 and D14S605) also attained evidence of linkage. To explore the hypothesis that the signals on chromosomes 4 and 20 are differentially attributable to variation in BMI or age of onset, an ordered subset analysis was conducted. This analysis revealed that only when the families were ranked by BMI (in increasing order) did a subset attain nominal significance, and only for chromosome 4. The findings reported here lend credence to the hypothesis, now supported by four studies of Caucasian populations and most recently by a combined analysis of 1,852 pedigrees, that a type 2 diabetes susceptibility locus resides on chromosome 20q. This population, because of its unique genetic attributes, may facilitate identification of this and other genes contributing to type 2 diabetes.

Body Mass Index↗

PubMed2001

Training of acute confusion resource nurses. Knowledge, perceived confidence, and role.

Most nurses function as generalists; however, some function in "expert" roles based on informal training as Resource Nurses. Training usually focuses on assessment and management of a specific problem, with the goal of creating a readily available "expert" for every unit. The primary activity of the Resource Nurse is to provide expert care, education, and consultation for patients, families, and staff. The Iowa-Veterans Affairs Nursing Research Consortium (IVANRC) addressed the need to manage acutely confused/delirious clients by training staff nurse volunteers (N = 129) from all units of the four Iowa Veterans Affairs facilities to act as unit-based acute confusion Resource Nurses (ACRNs). A day-long workshop included didactic content addressing etiology and presentation of acute confusion (AC), use of the IVANRC protocol to assess for AC, and basic information on treatment and management of AC. The nurses also participated in an efficacy-based experiential learning program on AC assessment that involved demonstrating assessment of AC and role enactment practice exercises in which ACRNs practiced the assessment. A test of knowledge of AC and perceived level of confidence in assessing acutely confused patients was administered before and after completion of the program. Paired t tests comparing pre- and posttest scores showed that knowledge and confidence significantly increased for the nurses as a result of their participation in the educational program. Eighteen months later, a second program was conducted to update current ACRNs and train additional RNs to enact this role. Pre- and posttest scores were obtained, with paired t tests showing a significant increase in knowledge for the participants. Twenty-four (49%) of the second program attendees had attended the first program. These participants had significantly higher scores on the second program pretest than those participants who had not attended the previous program, indicating a retention of knowledge from the first program.

Acute Disease↗

PubMed2001

Segregation patterns and heteroplasmy prevalence in Leber's hereditary optic neuropathy.

PURPOSE: To investigate the segregation pattern of the mitochondrial DNA mutation at nucleotide position 3460 responsible for Leber's hereditary optic neuropathy (LHON) and to determine the prevalence of heteroplasmy for the three primary LHON mutations at positions 11778, 3460, and 14484. METHODS: Segregation analysis was performed in a cross-sectional study by determining the level of heteroplasmy in blood leukocytes of 23 LHON patients and unaffected carriers from four unrelated families. One family comprising two affected and three unaffected carriers was followed over 5.5 years for a longitudinal segregation analysis of heteroplasmy. The percentage of mutant mtDNA was determined using a novel procedure of fluorescence-based primer extension and restriction fragment length polymorphism analysis. The prevalence of heteroplasmy was assessed by determining the number of genealogically unrelated LHON pedigrees with heteroplasmic maternal family members from the LHON patient records of the Department of Ophthalmology, University of Tübingen, Germany. RESULTS: The authors observed a marked variability in the degree of heteroplasmy levels within each pedigree and a tendency toward a higher mutant allele frequency in offspring generations. Disease expression was correlated with higher levels of mutant mtDNA molecules. Longitudinal analysis revealed no statistically significant decrease in the heteroplasmy level in the family studied but a reduction of 11% and 12% in one affected and one unaffected individual, respectively. In 167 genealogically unrelated LHON families the prevalence of heteroplasmy was 5.6%, 40%, and 36.4% for the 11778, 3460, and 14484 LHON mutations, respectively. CONCLUSIONS: Cross-sectional studies of heteroplasmy for the 3460 LHON mutation suggest that the genotype shifts toward a higher mutational load in offspring generations. Long-term decrease in the blood mutant load in single cases indicates negative selection of the mutant allele in the hematopoietic cell system. The prevalence of heteroplasmy varies significantly between the different primary LHON mutations, suggesting genotypical differences in disease expression.

Chromosome Segregation↗

PubMed2001

Newspaper advertising by health maintenance organizations during the reform of healthcare services in Israel.

BACKGROUND: On 1 January 1995 a new mandatory National Health Insurance Law was enacted in Israel. The new law fostered competition among the four major Israeli healthcare providers (HMOs or sick funds) already operating in the market due to the possibility that an unlimited number of patients and the relative budget share would shift among the HMOs. This led them to launch advertising campaigns to attract new members. OBJECTIVES: To examine newspaper advertising activities during the early stages of healthcare market reform in Israel. METHODS: Advertising efforts were reviewed during a study period of 24 months (July 1994 to June 1996). Advertisements were analyzed in terms of marketing strategy, costs and quality of information. RESULTS: During the study period 412 newspaper advertisements were collected. The total advertising costs by all HMOs was approximately US$4 million in 1996 prices. Differences were found in marketing strategy, relative advertising costs, contents and priorities among the HMOs. CONCLUSIONS: The content of HMOs' newspaper advertising was consistent with their marketing strategy. The messages met the criteria of persuasive advertising in that they cultivated interest in the HMOs but did not provide meaningful information about them. Future developments in this area should include consensus guidelines for advertising activities of HMOs in Israel, instruction concerning the content of messages, and standardization of criteria to report on HMO performance.

Advertising↗

PubMed2001

Successful cardiac transplantation after Novacor implantation in a HIT II-patient using heparin.

The anticoagulative management of patients tested positive for heparin-induced thrombocytopenia type II (HIT II) and requiring cardiac surgery has been difficult until now. A special challenge arises, when left ventricular assist devices have to be implanted for bridging to cardiac transplantation. We report on the anticoagulative management of such a patient, based on the consideration of HIT II-pathophysiology and using heparin for Novacor LVAD implantation and cardiac transplantation.

Adult↗

PubMed2000

Protective effect of amifostine on dental health after radiotherapy of the head and neck.

PURPOSE: The cytoprotective agent amifostine has been shown to reduce the radiation-induced acute and chronic xerostomia in head and neck cancer patients. The purpose of this study was to evaluate whether or not amifostine also reduces the incidence of dental caries associated with the radiation-induced xerostomia. METHODS AND MATERIALS: The dental status before and 1 year after radiotherapy was retrospectively compared in 35 unselected patients treated as part of the prospective randomized and multicenter open-label Phase III study (WR-38) at the University Hospitals of Heidelberg, Freiburg, and Erlangen. The WR-38 study compared radiotherapy in head and neck cancer with and without concomitant administration of amifostine. RESULTS: Patient and treatment characteristics (particularly the radiation dose and percentage of parotids included in the treatment volume) were equally distributed between the patients who received (n = 17) or did not receive (n = 18) amifostine. Fifteen patients of the amifostine group showed no deterioration of the dental status 1 year after radiotherapy as compared to 7 patients who did not receive the cytoprotector (p = 0. 015, two-tailed Fisher exact test). CONCLUSION: Our data suggest a protective effect of amifostine on the dental health after radiotherapy of the head and neck. The dental status should be used as a primary endpoint in future studies on amifostine.

Adult↗

PubMed2000

Arteriovenous carboxyhemoglobin gradient is a technical artifact that is eliminated by special calibration (SAT 100).

Pulmonary enzyme heme oxygenase, which catalyses carbon monoxide production, may be responsible for arteriovenous carboxyhemoglobin (COHb) differences measured in humans. Unspecific inflammatory stimuli have been shown to induce pulmonary heme oxygenase possibly leading to increased pulmonary carbon monoxide production and elevated arterial COHb. Arteriovenous COHb gradients may therefore be a measurable parameter of lung injury severity. To exclude a technical artefact, we repeated measurements of central venous COHb and arterial COHb in healthy humans (ASA I-II) undergoing elective surgery with the ABL 625 and the updated version, ABL 725 (Radiometer, Copenhagen). In addition to the standard calibration, an especially accurate adjustment of the spectrophotometer wavelengths (SAT100) was performed. This adjustment eliminates the FCOHb dependency on the oxygen saturation. No significant differences were detectable between central venous and arterial COHb concentrations with either blood gas analyzer. The difference between central venous COHb and arterial COHb was 0.09 with the ABL 625 and -0.03 with the ABL 725. Therefore, we conclude that previously reported arteriovenous COHb differences are artifactual and may be eliminated by SAT 100 adjustment, as is possible with the ABL 725.

Arteries↗

PubMed2000

Antiphase oscillation of the left and right suprachiasmatic nuclei.

An unusual property of the circadian timekeeping systems of animals is rhythm "splitting," in which a single daily period of physical activity (usually measured as wheel running) dissociates into two stably coupled components about 12 hours apart; this behavior has been ascribed to a clock composed of two circadian oscillators cycling in antiphase. We analyzed gene expression in the hypothalamic circadian clock, the suprachiasmatic nucleus (SCN), of behaviorally "split" hamsters housed in constant light. The results show that the two oscillators underlying the split condition correspond to the left and right sides of the bilaterally paired SCN.

ARNTL Transcription Factors↗

PubMed2000

Fitness in soil and rhizosphere of Pseudomonas fluorescens C7R12 compared with a C7R12 mutant affected in pyoverdine synthesis and uptake.

Fluorescent pseudomonads have evolved an efficient strategy of iron uptake based on the synthesis of the siderophore pyoverdine and its relevant outer membrane receptor. The possible implication of pyoverdine synthesis and uptake on the ecological competence of a model strain (Pseudomonas fluorescens C7R12) in soil habitats was evaluated using a pyoverdine minus mutant (PL1) obtained by random insertion of the transposon Tn5. The Tn5 flanking DNA was amplified by inverse PCR and sequenced. The nucleotide sequence was found to show a high level of identity with pvsB, a pyoverdine synthetase. As expected, the mutant PL1 was significantly more susceptible to iron starvation than the wild-type strain despite its ability to produce another unknown siderophore. As with the wild-type strain, the mutant PL1 was able to incorporate the wild-type pyoverdine and five pyoverdines of foreign origin, but at a significantly lower rate despite the similarity of the outer membrane protein patterns of the two strains. The survival kinetics of the wild-type and of the pyoverdine minus mutant, in bulk and rhizosphere soil, were compared under gnotobiotic and non-gnotobiotic conditions. In gnotobiotic model systems, both strains, when inoculated separately, showed a similar survival in soil and rhizosphere, suggesting that iron was not a limiting factor. In contrast, when inoculated together, the bacterial competition was favorable to the pyoverdine producer C7R12. The efficient fitness of PL1 in the presence of the indigenous microflora, even when coinoculated with C7R12, is assumed to be related to its ability to uptake heterologous pyoverdines. Altogether, these results suggest that pyoverdine-mediated iron uptake is involved in the ecological competence of the strain P. fluorescens C7R12.

Journal Article↗

PubMed2000

Purification, characterisation, cloning and sequencing of the gene encoding oligopeptidase PepO from Streptococcus thermophilus A.

The oligopeptidase PepO from Streptococcus thermophilus A was purified to protein homogeneity by a five-step chromatography procedure. It was estimated to be a serine metallopeptidase of 70 kDa, with maximal activity at pH 6.5 and 41 degrees C. PepO has endopeptidase activity on oligopeptides composed of between five and 30 amino acids. PepO was demonstrated to be active and stable at the pH, temperature and salt concentrations found in Swiss-type cheese during ripening. Using a battery of PCR techniques, the pepO gene was amplified, subcloned and sequenced, revealing an open reading frame of 1893 nucleotides. The amino acid sequence analysis of the pepO gene-translation product shows homology with PepO enzymes from other lactic acid bacteria and contains the signature sequence of the metallopeptidase family.

Amino Acid Sequence↗

PubMed2000

Splitting schizophrenia: periodic catatonia-susceptibility locus on chromosome 15q15.

The nature of subtypes in schizophrenia and the meaning of heterogeneity in schizophrenia have been considered a principal controversy in psychiatric research. We addressed these issues in periodic catatonia, a clinical entity derived from Leonhard's classification of schizophrenias, in a genomewide linkage scan. Periodic catatonia is characterized by qualitative psychomotor disturbances during acute psychotic outbursts and by long-term outcome. On the basis of our previous findings of a lifetime morbidity risk of 26.9% of periodic catatonia in first-degree relatives, we conducted a genome scan in 12 multiplex pedigrees with 135 individuals, using 356 markers with an average spacing of 11 cM. In nonparametric multipoint linkage analyses (by GENEHUNTER-PLUS), significant evidence for linkage was obtained on chromosome 15q15 (P = 2.6 x 10(-5); nonparametric LOD score [LOD*] 3.57). A further locus on chromosome 22q13 with suggestive evidence for linkage (P = 1.8 x 10(-3); LOD* 1.85) was detected, which indicated genetic heterogeneity. Parametric linkage analysis under an autosomal dominant model (affecteds-only analysis) provided independent confirmation of nonparametric linkage results, with maximum LOD scores 2.75 (recombination fraction [theta].04; two-point analysis) and 2.89 (theta =.029; four-point analysis), at the chromosome 15q candidate region. Splitting the complex group of schizophrenias on the basis of clinical observation and genetic analysis, we identified periodic catatonia as a valid nosological entity. Our findings provide evidence that periodic catatonia is associated with a major disease locus, which maps to chromosome 15q15.

Catatonia↗

PubMed2000

Surface coating with cyclic RGD peptides stimulates osteoblast adhesion and proliferation as well as bone formation.

The physiological inertness of synthetic implant materials often results in insufficient implant integration and limited acceptance of implants in tissues. After implantation the implant surface is often separated from the surrounding healthy and regenerating tissue, for example by a fibrous capsule. To avoid this host-versus-graft reaction, a strong mechanical contact between tissue and implant must be ensured. An enhanced contact between graft and the surrounding tissue can be provided by coating the implant with cell-adhesive molecules. The highly active and alpha(v)beta(3)- and alpha(v)beta(5)-integrin-selective peptide c(-RGDfK-) (f=D-phenylalanine) was functionalized with various linker molecules containing an acrylamide end group by using the lysine side chain of c(-RGDfK-). The acrylamide group can be used to bind the peptide covalently to poly(methyl methacrylate) (PMMA) surfaces. The coated surfaces effectively bind to murine osteoblasts as well as human osteoblasts in vitro when a minimum distance of 3.5 nm between surface and the constrained RGD sequence is provided. In contrast to osteoblasts in cell suspension, surface-bound osteoblasts show no apoptosis but proliferate by a factor of 10 over a 22 d period. Coating of inert implant surfaces with highly active and alpha(v)-selective peptides affords a marked improvement in osteoblast binding over current technologies. In vivo studies show that peptide-coated PMMA pellets implanted into the patella groove of rabbits are integrated into the regenerating bone tissue faster and more strongly than uncoated pellets.

Animals↗

PubMed2000

Structure of a thioredoxin-like [2Fe-2S] ferredoxin from Aquifex aeolicus.

The 2.3 A resolution crystal structure of a [2Fe-2S] cluster containing ferredoxin from Aquifex aeolicus reveals a thioredoxin-like fold that is novel among iron-sulfur proteins. The [2Fe-2S] cluster is located near the surface of the protein, at a site corresponding to that of the active-site disulfide bridge in thioredoxin. The four cysteine ligands are located near the ends of two surface loops. Two of these ligands can be substituted by non-native cysteine residues introduced throughout a stretch of the polypeptide chain that forms a protruding loop extending away from the cluster. The presence of homologs of this ferredoxin as components of more complex anaerobic and aerobic electron transfer systems indicates that this is a versatile fold for biological redox processes.

Amino Acid Sequence↗

PubMed2000

Linkage and family-based association study of schizophrenia and the synapsin III locus that maps to chromosome 22q13.

The human synapsin III gene (synapsin III) is a member of a neuron-specific phosphoprotein gene family involved in short-term neurotransmitter release. We mapped synapsin III to chromosomal region 22q13 (13.1-13.31) by fluorescence in situ hybridization, a region that has been identified as a potential schizophrenia susceptibility locus. The dinucleotide repeat marker D22S280 located in intron 5 of synapsin III was genotyped in a linkage and family-based association study to assess the role of the synapsin III locus in the etiology of schizophrenia. In 12 pedigrees with periodic catatonia comprising 135 individuals, we found exclusion of linkage of marker D22S280 using lod score analysis with autosomal dominant/recessive models as well as affected only LOD score methods with dominant/recessive models. In a family-based association study of 61 unrelated parent-offspring trios with schizophrenia (according to the the Diagnostic and Statistical Manual of Mental Disorders, fourth edition [DSM-IV, American Psychiatric Association, 1994]), we found no association of individual D22S280 alleles to disease. Results of a multiallelic transmission/disequilibrium test (TDT(max) = 3.00; P = 0.55) challenged the possibility that D22S280 alleles appear with DSM-IV schizophrenia more frequently than expected. In addition, no evidence for gender differences or parent-of-origin effects were found. Thus, the synapsin III locus at chromosome 22q13 is not likely to contain a schizophrenia susceptibility gene.

Adult↗

PubMed2000

Rhinoviruses infect the lower airways.

Rhinoviruses are the major cause of the common cold and a trigger of acute asthma exacerbations. Whether these exacerbations result from direct infection of the lower airway or from indirect mechanisms consequent on infection of the upper airway alone is currently unknown. Lower respiratory infection was investigated in vitro by exposing primary human bronchial epithelial cells to rhinoviruses and in vivo after experimental upper respiratory infection of human volunteers. Bronchial infection was confirmed by both approaches. Furthermore, rhinoviruses induced production of interleukin-6, -8, and -16 and RANTES and were cytotoxic to cultured respiratory epithelium. This evidence strongly supports a direct lower respiratory epithelial reaction as the initial event in the induction of rhinovirus-mediated asthma exacerbations. The frequency of infection and the nature of the inflammatory response observed are similar to those of the upper respiratory tract, suggesting that rhinovirus infections may be one of the most important causes of lower in addition to upper respiratory disease.

Bronchi↗