PubMed Health⌕ Search

Biomedical subjects

M Mayer

Publications and source records attributed to M Mayer.

At least 37 records · Page 2Linked to original sources
PubMed2001

Group epitope mapping by saturation transfer difference NMR to identify segments of a ligand in direct contact with a protein receptor.

A protocol based on saturation transfer difference (STD) NMR spectra was developed to characterize the binding interactions at an atom level, termed group epitope mapping (GEM). As an example we chose the well-studied system of galactose binding to the 120-kDa lectin Ricinus communis agglutinin I (RCA(120)). As ligands we used methyl beta-D-galactoside and a biantennary decasaccharide. Analysis of the saturation transfer effects of methyl beta-D-galactoside showed that the H2, H3, and H4 protons are saturated to the highest degree, giving evidence of their close proximity to protons of the RCA(120) lectin. The direct interaction of the lectin with this region of the galactose is in excellent agreement with results obtained from the analysis of the binding specificities of many chemically modified galactose derivatives (Bhattacharyya, L.; Brewer, C. F. Eur. J. Biochem. 1988, 176, 207-212). This new NMR technique can identify the binding epitope of even complex ligands very quickly, which is a great improvement over time-consuming chemical modifications. Efficient GEM benefits from a relatively high off rate of the ligand and a large excess of the ligand over the receptor. Even for a ligand like the biantennary decasaccharide with micromolar binding affinity, the binding epitopes could easily be mapped to the terminal beta-D-Gal-(1-4)-beta-D-GlcNAc (beta-D-GlcNAc = N-acetyl-D-glucosamine) residues located at the nonreducing end of the two carbohydrate chains. The binding contribution of the terminal galactose residue is stronger than those of the penultimate GlcNAc residues. We could show that the GlcNAc residues bind "edge-on" with the region from H2 to H4, making contact with the protein. Analysis of STD NMR experiments performed under competitive conditions proved that the two saccharides studied bind at the same receptor site, thereby ruling out unspecific binding.

Acetylglucosamine↗
PubMed2001

[Rehabilitation of patients with multiple sclerosis].

BACKGROUND: During the last decades a significant progress in rehabilitation of patients with multiple sclerosis (MS) has been achieved. This pilot study aims to study effect of weeks-lasting rehabilitation programme of MS patients in conditions of non-profiled inpatient rehabilitation unit. METHODS AND RESULTS: The rehabilitation program of 25 hospitalised patients was mostly aimed at complex kinesitherapy and physical therapy, partly also at ergotherapy and orthetics. Functional status of patients was evaluated at the beginning of the hospital stay and before dismission. Spasticity of lower limbs was scored using Global Assessment of Spasticity Scale (GSA) and modified Ashwort's scale. Motor subscore of Functional Independence Measure (FIM) was used to assess the patient's disability. In interval of 5 to 6 months a questionnaire was distributed among the patients to evaluate the rehabilitation stay. During the rehabilitation none of the studied patients got worse. At the beginning of hospitalisation average EDSS was 6.7 (median 6.5) +/- 1.0, before the demission it was 6.5 (6.5) +/- 0.9. Among the parameters studied statistically significant improvement came in the modified Ashwort's scale (from 2.5 +/- 0.8 to 1.8 +/- 0.6) and in the motor subscore of Functional Independence Measure (from 59 +/- 15 to 64 +/- 14). No statistically significant difference was found when the Global Assessment of Spasticity Scale was used--the improvement score of the group was 1.0 +/- 0.7. Not all of questionnaires returned. The results obtained from responders showed positive evaluation of the rehabilitation program, which lasted for several months. CONCLUSION: Results of the study correspond to the literary data both in immediate effects of the treatment and in its persistence after dismission. As important reveals the fact that most of the patients has primary or secondary progressive MS. It can be reasonably presumed that further improvement of the rehabilitation of patients with neurological diseases could be achieved in specialised neurorehabilitation centres.

Humans↗
PubMed2001

The MetaFam Server: a comprehensive protein family resource.

MetaFam is a comprehensive relational database of protein family information. This web-accessible resource integrates data from several primary sequence and secondary protein family databases. By pooling together the information from these disparate sources, MetaFam is able to provide the most complete protein family sets available. Users are able to explore the interrelationships among these primary and secondary databases using a powerful graphical visualization tool, MetaFamView. Additionally, users can identify corresponding sequence entries among the sequence databases, obtain a quick summary of corresponding families (and their sequence members) among the family databases, and even attempt to classify their own unassigned sequences. Hypertext links to the appropriate source databases are provided at every level of navigation. Global family database statistics and information are also provided. Public access to the data is available at http://metafam.ahc.umn.edu/.

Computational Biology↗
PubMed2001

Percutaneous absorption of the montoterperne carvone: implication of stereoselective metabolism on blood levels.

The purpose of this study was to determine whether an enantioselective difference in the metabolism of topically applied R-(-)- and S-(+)-carvone could be observed in man. In a previous investigation we found that R-(-)- and S-(+)-carvone are stereoselectively biotransformed by human liver microsomes to 4R,6S-(-)- and 45,6S-(+)-carveol, respectively, and 4R,6S-(-)-carveol is further glucuronidated. We therefore investigated the metabolism and pharmacokinetics of R-(-)- and S-(+)-carvone in four healthy subjects using chiral gas chromatography as the analytical method. Following separate topical applications at a dose of 300 mg, R-(-)- and S-(+)-carvone were rapidly absorbed, resulting in significantly higher Cmax levels for S-(+)-carvone (88.0 vs 23.9 ng mL(-1)) and longer distribution half-lives (t(1/2alpha)) (19.4 vs 7.8 min), resulting in 3.4-fold higher areas under the blood concentration-time curves (5420 vs 1611 ng min mL(-1)). The biotransformation products for both enantiomers in plasma were below detection limit. Analysis of control- and beta-glucuronidase pretreated urine samples, however, revealed a stereoselective metabolism of R-(-)-carvone to 4R,6S-(-)-carveol and 4R,6S-(-)-carveol glucuronide. No metabolites could be found in urine samples after S-(+)-carvone application. These data indicate that stereoselectivity in phase-I and phase-II metabolism has significant effects on R-(-)- and S-(+)-carvone pharmacokinetics. This might serve to explain the increased blood levels of S-(+)-carvone.

Administration, Cutaneous↗
PubMed2001

Unit-independent reporting of laboratory test results.

A variety of laboratory measurement units, assay systems, and reference values are presently being used in different clinical environments. There is therefore a challenge in provision of tools for presentation of laboratory data in harmonized forms that reduce the information load and reinforce clinical perception of test results. This paper describes the use of standard deviation (SD) units and logarithmic time graphical displays to improve presentation of laboratory test results. The SD concept employs strength of the change from normality as a diagnostic indicator, and the logarithmic time scale enables long-term overview of patient results. The suggested format is expected to promote effective transfer of test result information between laboratories, clinicians and hospitals.

Chemistry, Clinical↗
PubMed2001

[Sciatic paralysis after a buttock intramuscular injection in children: an ongoing risk factor].

Intramuscular injections are regularly recommended for the administration of certain drugs in children. This article underlines the fact that buttock intramuscular injection risks injury to the sciatic nerve, which may lead to lower limb palsy, most often presenting as paralytic drop foot. This condition rarely results from direct traumatic lesion of the sciatic nerve, but usually from the caustic effect of the injected drug. It may occur in older children and adolescents, as well as in infants and younger children. Therefore, the buttocks should not be used as an intramuscular injection site in children whatever their age. In the case of sciatic nerve injury following intramuscular injection, extrafascicular neurolysis may prevent the occurrence of paralysis.

Adolescent↗
PubMed2001

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: decrease in regional cerebral blood volume in hyperintense subcortical lesions inversely correlates with disability and cognitive performance.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathic syndrome related to a genetic defect on chromosome 19. Characteristic changes in CADASIL can be observed onT2-weighted MR images in the subcortical white matter. The purpose of this study was to measure changes of regional cerebral blood volume (rCBV) with dynamic contrast-enhanced MR imaging and to correlate the changes to disability and cognitive performance. METHODS: We obtained rCBV measurements of 24 individuals with proven CADASIL on a 1.5-T MR imaging unit. A susceptibility-weighted MR imaging sequence was used for bolus tracking. Principles of the indicator dilution theory were applied to estimate values of absolute rCBV (mL/100 g). Disability was determined by using the Rankin scale, and overall cognitive performance was assessed by using the Mini-Mental State Examination. RESULTS: The mean rCBV in the subcortical white matter that was hyperintense on the T2-weighted images (2.7 +/- 0.8 mL/100 g) was significantly lower than the rCBV in the white matter that appeared normal on the T2-weighted images (4.4 +/- 1.3 mL/100 g) (P <.05). The mean rCBV in the gray matter was within the normal range (8.3 +/- 1.7 mL/100 g). Both cognitive impairment and disability negatively correlated with rCBV in the subcortical white matter that was hyperintense (P <.05) but not with rCBV in the normal appearing white matter. rCBV did not correlate with age. CONCLUSION: rCBV measured in the hyperintense subcortical white matter in individuals with CADASIL was decreased and inversely correlated with disability and cognitive impairment.

Adult↗
PubMed2000

BiP and PDI cooperate in the oxidative folding of antibodies in vitro.

Immunoglobulin heavy chain binding protein (BiP), a member of the Hsp70 chaperone family, and the oxidoreductase protein-disulfide isomerase (PDI) play an important role in the folding and oxidation of proteins in the endoplasmic reticulum. However, it was not clear whether both cooperate in this process. We show here that BiP and PDI act synergistically in the in vitro folding of the denatured and reduced Fab fragment. Several ATP-dependent cycles of binding, release, and rebinding of the unfolded antibody chains by BiP are required for efficient reactivation. Our data suggest that in the absence of BiP unfolded antibody chains collapse rapidly upon refolding, rendering cysteine side chains inaccessible for PDI. BiP binds the unfolded polypeptide chains and keeps them in a conformation in which the cysteine residues are accessible for PDI. These findings support the idea of a network of folding helper proteins in the endoplasmic reticulum, which makes this organelle a dedicated protein-processing compartment.

Carrier Proteins↗
PubMed2000

A Chip-Based Biosensor for the Functional Analysis of Single Ion Channels We thank E. Ermanntraut, L. Giovangrandi, T. Wohland, A. Brecht, M. Köhler, C. Bieri, D. Stamou, and R. Hovius for advice. This work was supported by the Swiss National Science Foundation (Priority Program for Biotechnology) and by an interdepartmental grant of the Swiss Federal Institute of Technology Lausanne (EPFL, Project Microtechnique 96).

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

Triose phosphate isomerase deficiency in 3 French families: two novel null alleles, a frameshift mutation (TPI Alfortville) and an alteration in the initiation codon (TPI Paris).

Three French families with triose phosphate isomerase (TPI) deficiency were studied, and 2 new mutations giving rise to null alleles were observed: a frameshift mutation with deletion of the 86-87 TG dinucleotide in codon 29 (TPI Alfortville) and a T-->A transversion in nucleotide 2 of the initiation codon (TPI Paris). The first mutation occurred in compound heterozygosity with the frequent E105D mutation. The second mutation occurred in association with the 2-nucleotide promoter variant (-43G,-46A). In a third family, the propositus was an E105D homozygote. In the TPI Paris family, the coinheritance of the -43,-46 promoter variant appeared to exert little, if any, effect on TPI enzyme activity, a finding consistent with 2 previous reports that questioned the putative role of the promoter polymorphism as a true deficiency variant. Similarly, the further coinheritance of glucose-6-phosphate dehydrogenase (G6PD) A- (202 G-->A/376 A-->G) appeared to have little effect on the observed phenotype. Compound heterozygosity for the E105D mutation with the null allele TPI Alfortville appeared to lead to a more severe clinical syndrome than did E105D homozygosity, suggesting that compound heterozygosity with null alleles may lead to more profound clinical abnormalities than homozygosity with missense alleles. A simple, rapid polymerase chain reaction and restriction enzyme procedure for the E105D mutation was developed for prenatal diagnosis in one family and subsequently used for screening in the other families.

Adult↗
PubMed2000

Mapping the active site of angiotensin-converting enzyme by transferred NOE spectroscopy.

The interaction of five furylacryloyl (fa)-amino acid derivatives, fa-Phe, fa-Phe-Phe, fa-Gly-Leu-NH(2), fa-Ala-Lys, and fa-Trp, with angiotensin-converting enzyme (ACE), a protein of MW = 130 kDa, was studied by transferred NOESY experiments. Identification of fa derivatives binding to ACE as well as determination of their relative affinities could be accomplished directly from the compound mixtures. Of the five fa derivatives we found that fa-Phe, fa-Trp, and fa-Gly-Leu-NH(2) bind more strongly to ACE than the other two. The dissociation constant of fa-Phe was determined from NMR spectra to 5 x 10(-4) M. A large excess of dipeptides competitively displaced fa-Trp and fa-Phe-Phe from the receptor pocket, allowing the binding site to be mapped. Also, the relative affinities of the fa-Phe, fa-Ala-Lys, and fa-Gly-Leu-NH(2) changed after addition of the dipeptides with fa-Gly-Leu-NH(2) showing the strongest binding. In addition, the presence of a strong inhibitor of the S1' and S2' sites, namely captopril, resulted in the same transferred NOE intensities of fa-Phe, indicating that it binds solely to the S1 and S2 subsites. A rapid screening of binding specificity from mixtures is possible by using a large excess of ligand(s) in transferred NOE studies, even when relatively small amounts of protein are present.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

tRNA 3' processing in plants: nuclear and mitochondrial activities differ.

The nuclear tRNA 3' processing activity from wheat has been characterized and partially purified. Several characteristics of the wheat nuclear 3' processing enzyme now allow this activity to be distinguished from its mitochondrial counterpart. The nuclear enzyme is an endonuclease, which we termed nuclear RNase Z. The enzyme cleaves at the discriminator base and seems to consist only of protein subunits, since essential RNA subunits could not be detected. RNase Z leaves 5' terminal phosphoryl and 3' terminal hydroxyl groups at the processing products. It is a stable enzyme being active over broad temperature and pH ranges, with the highest activity at 35 degrees C and pH 8.4. The apparent molecular mass according to gel filtration chromatography is 122 kDa. The nuclear RNase Z does process 5' extended pretRNAs but with a much lower efficiency than 5' matured pretRNAs. Nuclear intron-containing precursor tRNAs as well as mitochondrial precursor tRNAs are efficiently cleaved by the nuclear RNase Z. Mitochondrial pretRNA(His) is processed by the nuclear RNase Z, generating a mature tRNA(His) containing an 8 base pair acceptor stem. The edited mitochondrial pretRNA(Phe) is cleaved easily, while the unedited version having a mismatch in the acceptor stem is not cleaved. Thus, an intact acceptor stem seems to be required for processing. Experiments with precursors containing mutated tRNAs showed that a completely intact anticodon arm is not necessary for processing by RNase Z. Comparison of the plant nuclear tRNA 3' processing enzyme with the plant mitochondrial one suggests that both activities are different enzymes.

Cell Nucleus↗
PubMed2000

Genotype determination at the survival motor neuron locus in a normal population and SMA carriers using competitive PCR and primer extension.

Precise quantitation of SMN1 copy number is of great interest in many clinical applications such as direct detection of SMA carriers or detection of an SMA-affected patient with a hemizygous deletion of the SMN1 gene. We describe a method that combines two independent nonradioactive PCR assays: determination of the relative ratio of the SMN1 and SMN2 genes using a primer extension assay and of the total SMN copy number using competitive PCR. Consistency of the results of two independent approaches ensures the reliability of the deduced genotype and thus avoids false interpretation of borderline results that can occur in quantitative assays. In all, 135 subjects were tested, including 91 normal controls and 44 SMA-affected children or SMA carriers. Two main genotypes were observed in controls: 2T/2C (45%) and 2T/1C (32%). A wide variability at the SMN locus is observed with nine different genotypes and up to six SMN genes. SMA carriers showed three frequent genotypes, 1T/2C (50%), 1T/3C (29%), and 1T/1C (18%). Normal chromosomes with two SMN1 genes per chromosome are not infrequent and thus, about 3% of SMA carriers are not detected using SMN1 copy number quantitation. Finally, as this method does not detect point mutations (4% of SMN1 gene mutations), reliability ranges from 93% to 100% depending on data available from the propositus.

Child, Preschool↗
PubMed2000

Neurotransmitters of the sympathetic nerve terminal are powerful chemoattractants for monocytes.

Macrophages in lymphoid organs are in close contact to nerve terminals of the sympathetic nervous system. Hence, these cells could be targets of neuronal modulation. We studied sympathetic neurotransmitters as chemoattractants enabling the aggregation of macrophages and nerve terminals. Norepinephrine (NE), neuropeptide Y (NPY), isoproterenol (beta-adrenergic), p-aminoclonidine (alpha2-adrenergic), methoxamine (alpha1-adrenergic), and adenosine triphosphate (ATP) were used to study human monocyte and macrophage migration in 48-well Boyden chambers. NE stimulated chemotaxis of monocytes and macrophages at an optimal concentration of 10-(10) M (P < 0.025). Isoproterenol, but not p-aminoclonidine or methoxamine, induced chemotaxis of monocytes (10(-10) M, P < 0.05). In these studies, elevation of cAMP is a critical step in NE-induced chemotaxis of monocytes. NPY (10(-11) M, P < 0.05) stimulated monocyte chemotaxis as well. ATP at 10(-4) and 10(-5) M stimulated undirected cell mobility (P < 0.05). All tested neurotransmitters of the sympathetic nerve terminal were potent chemoattractants. These findings may explain the close association of nerves and macrophages in tissue and lymphoid organs and may thus be of functional relevance in neuroimmunomodulation.

Chemotactic Factors↗
PubMed2000

Pre- and postnatal oral toxicity of vinclozolin in Wistar and Long-Evans rats.

Vinclozolin administered to pregnant Wistar and Long-Evans rats from day 14 postcoitum to day 3 postpartum at 200 mg/kg body wt/day was maternally toxic (reduced food consumption and body weight gain) and increased perinatal mortality; major adverse effects on sex-specific organs in male offspring were seen (reduced anogenital distance and index; persistence of nipples/areolas into adulthood; hypospadic penis; penile hypoplasia or development of a vaginal pouch; transient paraphimosis; hypoplasia and chronic inflammation of epididymides, prostate, seminal vesicles, and coagulating glands; and also testicular tubular atrophy and chronic inflammation of the urinary bladder in some Long-Evans) with isolated inflammation-related deaths due to pyelonephritis. At 12 mg/kg, prevalence of female areola/nipple anlagen in immature (preweaning) male offspring was increased in both strains; these persisted to adulthood in a few treated Long-Evans but not Wistar offspring. Adult Long-Evans but not Wistar at this dose also had hypoplasia of prostate, seminal vesicles, and coagulating glands, and a minority had testicular tubular atrophy. The no-observed-adverse-effect levels (NOAEL) were 12 and 6 mg/kg body wt in Wistar and Long-Evans rats, respectively, in these studies. The data suggest that both the Long-Evans and the Wistar rats are comparably sensitive to the antiandrogenic effects of vinclozolin. At dose levels below the NOAEL (1 and 3 mg/kg, respectively), there were no indications of any test-substance-related effects.

Administration, Oral↗
PubMed2000

The decrease in serum bone-specific alkaline phosphatase predicts bone mineral density response to hormone replacement therapy in early postmenopausal women.

Hormone replacement therapy (HRT) prevents bone loss in postmenopausal women. Up to 20% of women demonstrate no increase in bone mineral density (BMD) on HRT. We examined whether early changes in serum bone alkaline phosphatase (B-ALP) predict long-term BMD changes in postmenopausal women on HRT. Ninety women within 1 year of menopause were randomly assigned to continuous or sequential estrogen/progestin (beta estradiol/norethisterone acetate) if naturally postmenopausal, or beta estradiol if within 1 month of surgical menopause. Spine, femoral neck BMD (DXA), and B-ALP were determined over 2 years. The mean percent BMD changes were 3.8%, 2.9%, 1.6% in the spine and 2.4%, 4.0%, 1.1% in the femoral neck in sequential, continuous, and estrogen alone treatment groups, respectively, significantly different from zero except for femoral neck BMD change in the estrogen alone group. HRT was associated with spine and femoral neck BMD loss in 17.4% and 25.3% of women, respectively. In estrogen/progestin-treated women, baseline B-ALP correlated with spine BMD change (r = 0.42, P < 0.01). At 3 months, B-ALP dropped significantly in the estrogen/progestin-groups with a maximal decrease at 12 months, but no change from baseline in the estrogen alone group. Using quartile analysis, women with the greatest drop in B-ALP (> or = 50%) at 6 months demonstrated the greatest gain in spine BMD at 2 years. A 40% decrease at 6 months in B-ALP had a 56% sensitivity, 83% specificity, 95% positive predictive value for spine BMD gain at 2 years. The decrease in B-ALP can be used to monitor BMD response to HRT.

Adult↗
PubMed2000

Prophylaxis of postoperative relapse in Crohn's disease with mesalamine: European Cooperative Crohn's Disease Study VI.

BACKGROUND & AIMS: This study investigated if long-term treatment with high-dose mesalamine reduces the risk of clinical relapse of Crohn's disease after surgical resection. METHODS: In a prospective, randomized, double-blind, multicenter study, 4 g of mesalamine (Pentasa; Ferring A/S, Vanlose, Denmark) daily was compared with placebo in 318 patients. Treatment was started within 10 days after resective surgery and continued for 18 months. Primary outcome parameter was clinical relapse as defined by an increase in Crohn's Disease Activity Index, reoperation, septic complication, or newly developed fistula. Risk factors for recurrence were prospectively defined to be analyzed in a stepwise proportional hazards model. RESULTS: Cumulative relapse rates (+/-SE) after 18 months were 24.5% +/- 3.6% and 31.4% +/- 3.7% in the mesalamine (n = 152) and placebo (n = 166) groups, respectively (P = 0.10, log-rank test, 1-sided). Retrospective analysis showed a significantly reduced relapse rate with mesalamine only in a subgroup of patients with isolated small bowel disease (n = 124; 21.8% +/- 5.6% vs. 39.7% +/- 6.1%; P = 0.02, log-rank test). Probability of relapse was predominantly influenced by the duration of disease (P = 0.0006) and steroid intake before surgery (additional risk, P = 0.0003). CONCLUSIONS: Eighteen months of mesalamine, 4 g daily, did not significantly affect the postoperative course of Crohn's disease. Some relapse-preventing effect was found in patients with isolated small bowel disease.

Adult↗