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Biomedical subjects

B Müller

Publications and source records attributed to B Müller.

At least 145 records · Page 8Linked to original sources
PubMed2000

HLA-DRB1 genes, rheumatoid factor, and elevated C-reactive protein: independent risk factors of radiographic progression in early rheumatoid arthritis. Berlin Collaborating Rheumatological Study Group.

OBJECTIVE: To evaluate the prognostic value of HLA-DRB1 antigens, rheumatoid factor (RF), and C-reactive protein (CRP) with the radiographic outcome of rheumatoid arthritis (RA). METHODS: In total, 139 patients with early RA (< 2 years) were followed up. At the end of 3 year treatment with disease modifying antirheumatic drugs (DMARD) HLA genotyping and external radiographic scoring were performed. The time up to the first development of erosive disease [Ratingen radiographic score (RS) > 0, > 5, > 10] was compared by methods of survival analysis. RESULTS: At 4 years' disease duration, DRB1*04 or DRB1*01 positive patients had RS > 0 or > 10 (73% and 27%, respectively) significantly more frequently than DRB1*04 or DRB1*01 negative patients (37% and 7%, respectively). Nearly independently of the genetic predisposition, RF and elevated CRP at the start of DMARD treatment were predictive for erosive RA at 4 years. Elevated CRP (> or = 15 mg/l) increased the probability of erosive RA in DRB1*04 or DRB1*01 positive patients from 64.0% (in patients with CRP < 15 mg/l) to 83.9%, and in DRB1*04 and DRB1*01 negative patients from 18.8% to 70.1%. The corresponding figures for RF+ and RF- patients were 58.2% and 82.5% in HLA predisposed patients and 23.5% and 60.2% in those who were negative for DRB1*04 and DRB1*01. The probability of a RS > 10 was 40.9% for HLA predisposed patients with elevated CRP. In contrast, no case with RS > 10 was found in 43 patients who had neither of these 2 risk factors. CONCLUSION: Our findings support that HLA predisposition plays an important role with regard to radiographic progression. However, this effect is modified by RF serum concentration and disease activity.

Arthritis, Rheumatoid↗
PubMed1999

Characterization of the gltF gene product of Escherichia coli.

The glt operon of Escherichia coli comprises the structural genes for the glutamate synthase subunits (gltB and gltD) and gltF, whose product was previously suggested to have regulatory functions. The A/T-rich region between gltD and gltF contains a weak promoter and a translation initiation site for gltF. The GltF protein is preceded by a signal peptide, which is cleaved off during export into the periplasmic space. A gltF::Km(R) insertion mutant was constructed and shown here to have no detectable phenotype with respect to amino acid utilization or ammonium transport. Thus, GltF is apparently not involved in regulation of nitrogen catabolism.

AT Rich Sequence↗
PubMed1999

[What is the value of determining immunoreactive GHRH in acromegaly?].

Acromegaly is usually due to autonomous, excessive secretion of growth hormone from a pituitary adenoma. One would expect growth hormone-releasing factor (GHRH) in these patients to be suppressed. In the available literature referring to acromegaly, immunoreactive GHRH levels were determined in 259 acromegalic patients. When growth hormone was measured simultaneously, no correlation was found between serum growth hormone and plasma GHRH concentrations, irrespective of whether the acromegalic patients were treated or not. A possible explanation for this finding might be the lack of a feedback regulation between plasma growth hormone and GHRH. Also, since growth hormone is secreted in a pulsatile fashion the interpretation of single growth hormone values can be difficult. IGF I, which correlates well with mean growth hormone production, may therefore represent a more valuable criterion for the assessment of activity and GHRH plasma levels in acromegalics. However, no study has yet been performed to elucidate the relationship between GHRH and IGF I in acromegaly. To examine this relationship we measured the concentration of plasma GHRH and IGF I in 18 treated patients with acromegaly (age range 32-64 years median 50.5 years; median follow-up 6.5 years, range 3 months to 33 years). All immunoreactive GHRH levels were within the limits described as normal in the literature (mean +/- SD 22.89 +/- 2.72 pg/ml, range 19-28 pg/ml). The IGFI level was 396.78 +/- 224.26 ng/ml (mean +/- SD, range 71-876 ng/ml; reference ranges, age group 25-39 years: 114-492 ng/ml; 40-54 years: 90-360 ng/ml; > 55 years: 71-290 ng/ml). We found no correlation between IGF I and GHRH concentrations (r = 0.17). We therefore conclude that measuring plasma GHRH is not useful in the evaluation of the activity or therapy of acromegaly but may be helpful in its differential diagnosis since a massive elevation of GHRH is typically associated with the ectopic GHRH syndrome, a rare cause of acromegaly.

Acromegaly↗
PubMed1999

In vitro assembly properties of wild-type and cyclophilin-binding defective human immunodeficiency virus capsid proteins in the presence and absence of cyclophilin A.

The cellular protein cyclophilin A (CypA) binds specifically to the human immunodeficiency virus type 1 (HIV-1) capsid (CA) protein and is incorporated into HIV-1 particles at a molar ratio of 1:10 (CypA/CA). Structural analysis of a CA-CypA complex suggested that CypA may destabilize interactions in the viral capsid and thus promote uncoating. We analyzed the influence of CypA on the in vitro assembly properties of wild-type (WT) CA and derivatives containing substitutions of Gly89 in the Cyp-binding loop. All variant proteins were significantly impaired in CypA binding. In the presence of CypA at a molar ratio of 1:10 (CypA/CA), WT CA assembled into hollow cylinders that were similar to those observed in the absence of CypA but slightly longer. Higher CypA concentrations inhibited cylinder formation. Variant CA proteins G89L and G89F yielded similar cylinders as the WT protein but were significantly more resistant to CypA. Cryoelectron microscopic analysis of WT cylinders assembled in the presence of CypA revealed direct binding of CypA to the outer surface. Electron diffraction patterns generated from these cylinders indicated that CypA causes local disorder. The addition of CypA to preassembled cylinders had little effect, however, and cylinders were only disrupted when incubated with a threefold molar excess of CypA for several hours. These results suggest that CypA does not efficiently destabilize CA interactions at the molar ratio observed in the virion and therefore is unlikely to serve as an uncoating factor.

Capsid↗
PubMed1999

Enhanced transport of nanoparticle associated drugs through natural and artificial membranes--a general phenomenon?

The transport of nanoparticle associated drugs, [75Se]norcholestenol, captopril, methylene blue, hydrocortisone, doxorubicin, and dalargin was determined by permeability measurements in two chamber side by side diffusion cells using cellulose acetate, silicone rubber, pig small intestine, or hairless mice skin as membranes. Solutions of free drugs served as controls. The permeabilities depended on the physico chemical properties of the drugs which governed both, drug interaction with the nanoparticles as well as with the membranes. Consequently, the influence of dilution of the nanoparticle or free drug preparations on permeabilities was complex. With the exception of [75Se]norcholestenol the permeabilities were higher with free drugs than after binding to nanoparticles. The permeabilities of the membranes decreased in the order cellulose acetate, pig small intestine, silicone rubber, and hairless mouse skin.

Animals↗
PubMed1999

Synthesis, formation, and occurrence of contaminants in biotechnologically manufactured L-tryptophan.

The pattern of contaminants in pharmaceutical and feed grade L-tryptophan (Trp) was investigated in a market survey of 22 lots of 6 different manufacturers. To date, 5 case associated contaminants in Showa Denko tryptophan (SD-Trp) known to cause the autoimmune disease eosinophilia-myalgia syndrome (EMS) have been structurally elucidated: 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrroloindole-2-carboxylic acid (PIC), an indoline compound, is one of the most abundant degradation compounds of unbound Trp during oxidative treatment. 2-(3-indolylmethyl)-L-tryptophan (IMT) and 2-(2-hydroxyindoline)-tryptophan (HIT) are both 2-substituted Trp-derivatives. IMT was synthesized by the reaction of Trp and indole-3-methanol or indole-3-acetaldehyde, respectively. From this finding it is proposed that Trp-metabolites can decompose under formation of transitional, mesomerism-stabilized cations that react with excess Trp to yield 2-substituted Trp derivatives. The decomposition of Trp-metabolites could be induced by elevated or low pH-values that occur during the downstream processing of the Trp fermentation broth. IMT was detected in pharmaceutical-grade and feed-grade Trp in amounts of < 20-1,400 mg/kg. 1,1'-Ethylidenebis-(L-tryptophan) (EBT) is formed from acetaldehyde and Trp under acidic conditions and serves as a marker for EMS-suspicious Trp. 3-(Phenylamino)alanine (PAA) is the only not Trp derived case associated contaminant. Low amounts of PAA (20 mg/kg) could be detected in feed-grade Trp of one manufacturer. Non-EMS correlated 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acids of Trp and formaldehyde, acetaldehyde and indole-3-acetaldehyde could be detected in the examined Trp raw materials (< 10-13,500 mg/kg). In order to guarantee the safety of Trp containing drugs the amount of EBT (< 10 mg/kg Trp) and the sum of UV220 nm detectable contaminants (< 400 mg/kg Trp) are limited by the European authorities.

Animal Feed↗
PubMed1999

Synthesis and formation of an EMS correlated contaminant in biotechnologically manufactured L-tryptophan.

Contaminants in biotechnologically manufactured L-Tryptophan (Trp) are suspected to be responsible for the outbreak of an unknown autoimmune disease in 1989. The contaminants, found in Trp-lots of a Japanese manufacturer, are classified in EMS-correlated and non EMS-correlated substances. Up to now six EMS-correlated substances are known. One of these compounds is 2-(3'-indolylmethyl)-indole (IMT). IMT was detected as a major contaminant in two investigated EMS-associated trp-samples. In a seven step chemical synthesis IMT was obtained for use as a reference substance. A model system to investigate the formation of IMT was created using Trp and 3-indolylmethanol (IM). IMT formation was observed at acidic and alkaline pH-values and the optimal molar ratio of Trp to IM is 100:1. In addition an IMT formation was observed from indole, formaldehyde and Trp as well as from Trp and 3-indolylacetaldehyde.

Biotechnology↗
PubMed1999

Natural and induced regulation of Th1/Th2 balance.

Because Th1/Th2 balance is perturbed during immunological disease, the design of strategies aiming at its rectification has become a priority. The alteration of the balance in pregnancy so as to promote survival of the fetal allograft lends credibility to this aim. Attenuation of the activation signal delivered through the T cell receptor (TCR) represents a promising approach. It is supported by the high level of polymorphism in the MHC class II promoter, which regulates the natural TCR signal and thus modulates Th1/Th2 differentiation. Further support comes from the Th2 shift that occurs in JNK knockout mice, and with kinase inhibitors and anti-CD4 monoclonal antibodies applied in vitro. The approach has implications for nasal tolerance and inhibition of IL-12 production. The further range of options for Th1/Th2 modulation, which are presented throughout this issue of the journal, are here summarised and evaluated.

Animals↗
PubMed1999

[Indication for and performance of articular cartilage drilling using the Pridie method].

Articular cartilage has only a small capacity for regneration. This makes the repair of articular surfaces difficult. In 1959 Pridie described his method of resurfacing osteoarthritic knee joints. This operation is still in widespread use today. Pridie introduced the principle of drilling exposed subchondral bone with the objective of encouraging a fibro-cartilaginous repair. The newly formed fibrocartilaginous layer that develops over the lesion in osteoarthritis may be enough to decrease patients symptoms. Bone drilling into the subchondral layer is also effective in promoting healing of osteochondrosis dissecans. The choice of the treatment should be based on factors such as age of the patient, serverity of symptoms, activity level and functional demands on the joint, site and stage of the lesion. The drilling operation remains useful in osteoathritis and osteochondrosis dissecans.

Bone Regeneration↗
PubMed1999

Differential surface expression of HLA-DRB1 and HLA-DRB4 among peripheral blood cells of DR4 positive individuals.

Increasing interest in the functional consequences of differential expression of MHC class II molecules prompted us to examine the surface expression of HLA class II molecules on fresh peripheral blood mononuclear cells. Differential regulation of DR4 and DRB4 was shown for peripheral blood monocytes. In addition, DR4 expression is upregulated on B cells of patients suffering from chronic inflammation and is reduced under prednisolone-treatment. The expression levels of total DR molecules on a given cell type are almost identical comparing different haplotypes among non-RA controls, suggesting that the alpha-chain determines the level of surface expression. The present findings fit the hypothesis that the differential expression of HLA class II molecules is involved in regulation of the immune response and may thus contribute to determining susceptibility to immunological diseases.

Arthritis, Rheumatoid↗
PubMed1999

Effects of nitrogen dioxide exposure on Clara cell proliferation and morphology.

The present study was performed to relate Clara cell proliferation and Clara cell morphology to duration and intensity of nitrogen dioxide (NO2) exposure as a model of lung injury in rats. Male Sprague-Dawley rats were exposed to 5, 10 and 20 ppm NO2 for three (short term exposure) and 25 days (long term exposure). Epithelial proliferation was immunohistochemically assessed by BrdU-incorporation into the bronchial and bronchiolar epithelium. Clara cell specific 10 kD protein was detected using an antibody versus recombinant protein. Following short term exposure Clara cells showed a significant alteration of their morphology: the cells lost the apical intraluminal projections, and the damaged epithelium was covered by a layer of CC10 reactive material. After long term exposure the Clara cell morphology was indistinguishable from that of unexposed controls. In all short term exposure groups cellular proliferation was higher in the bronchiolar epithelium than in the bronchial epithelium. Whereas short term exposure to 5 ppm NO2 sufficed to induce a maximum epithelial proliferation of the bronchiolar epithelium, long term exposure to 5 ppm NO2 yielded no significant increase in the epithelial proliferation, a finding reflecting the adaptation of the airway epithelium to oxidative stress. Long term exposure to 10 and 20 ppm NO2 resulted in a dosilinear increase of cell proliferation in the bronchial and bronchiolar epithelium. Double labelling of CC10 and BrdU showed that BrdU uptake and hence proliferation were restricted to Clara cells. We conclude that changes of the Clara cell morphology are closely related to the extent of inhalative stress and functional status of the Clara cell. The results are in keeping with the assumption that the Clara cell exerts progenitor cell functions in the airway epithelium.

Animals↗
PubMed1999

Applications of neural network analyses to in vivo 1H magnetic resonance spectroscopy of epilepsy patients.

A total of 67 in vivo water-suppressed proton magnetic resonance spectra of the temporal lobes were recorded from 15 patients with long standing temporal lobe epilepsy and 13 healthy volunteers. Conventional data analysis indicated slightly lower N-acetyl aspartate levels in epileptic patients compared with controls. For further analysis of data, a spectral region (4.0-1.5 ppm) was used as input for artificial neural network analysis. Correct classification of spectra was obtained in 66 out of 67 cases, disregarding from which side of the brain the spectra were recorded. The ability of the trained network to recognize spectra recorded both contalaterally and ipsilaterally to the epileptic focus strongly indicates bilateral metabolic changes. Artificial neural networks could also be trained to recognize whether the spectra were recorded from the ipsilateral or contralateral side of the epileptic focus, indicating that neural network analysis of in vivo proton MR spectra can be used as an additional tool for pre-surgical lateralization of seizure foci.

Adolescent↗
PubMed1999

Synthesis of N-carboxyalkyl and N-aminoalkyl functionalized dipeptide building units for the assembly of backbone cyclic peptides.

To improve the assembly of backbone cyclic peptides, N-functionalized dipeptide building units were synthesized. The corresponding N-aminoalkyl or N-carboxyalkyl amino acids were formed by alkylation or reductive alkylation of amino acid benzyl or tert-butyl esters. In the case of N-aminoalkyl amino acid derivatives the aldehydes for reductive alkylation were obtained from N,O-dimethyl hydroxamates of N-protected amino acids by reduction with LiAlH4. N-carboxymethyl amino acids were synthesized by alkylation using bromoacetic acid ester and the N-carboxyethyl amino acids via reductive alkylation using aldehydes derived from formyl Meldrums acid. Removal of the carboxy protecting group leads to free N-alkyl amino acids of very low solubility in organic solvents, allowing efficient purification by extraction of the crude product. These N-alkyl amino acids were converted to their tetramethylsilane-esters by silylation with N,O-bis-(trimethylsilyl)acetamide and could thus be used for the coupling with Fmoc-protected amino acid chlorides or fluorides. To avoid racemization the tert-butyl esters of N-alkyl amino acids were coupled with the Fmoc-amino acid halides in the presence of the weak base collidine. Both the N-aminoalkyl and N-carboxyalkyl functionalized dipeptide building units could be obtained in good yield and purity. For peptide assembly on the solid support, the allyl type protection of the branching moiety turned out to be most suitable. The Fmoc-protected N-functionalized dipeptide units can be used like any amino acid derivative under the standard conditions for Fmoc-solid phase synthesis.

Amino Acids↗
PubMed1999

Characterization of human T-cell leukemia virus type I integrase expressed in Escherichia coli.

The C-terminal part of the pol gene of the human T-cell leukemia virus type I (HTLV-I) is predicted to encode the integrase (IN) of the virus; however, this protein has not yet been detected in virions or infected cells. We expressed the putative IN from an infectious molecular clone of HTLV-I in Escherichia coli. Comparison with protein resulting from coexpression of HTLV-I protease (PR) and Pol in insect cells indicated that the bacterially expressed protein is identical with or very similar to IN released from a PR-Pol precursor by proteolytic cleavage. HTLV-I IN was purified from E. coli under native conditions. The protein behaved like a dimer in size-exclusion chromatography. It carried out activities characteristic of retroviral IN with high efficiency, displaying a strong preference for U5-derived vs. U3-derived sequences in the processing and strand-transfer reactions. In the disintegration reaction, HTLV-I IN not only accepted the double-stranded branched substrate corresponding to the product of a strand-transfer reaction, but was also able to carry out a phosphoryl transfer on a branched molecule with a single-stranded or a single adenosine overhang.

Aspartic Acid Endopeptidases↗
PubMed1999

Vertical distribution of methanogens in the anoxic sediment of Rotsee (Switzerland).

Anoxic sediments from Rotsee (Switzerland) were analyzed for the presence and diversity of methanogens by using molecular tools and for methanogenic activity by using radiotracer techniques, in addition to the measurement of chemical profiles. After PCR-assisted sequence retrieval of the 16S rRNA genes (16S rDNA) from the anoxic sediment of Rotsee, cloning, and sequencing, a phylogenetic analysis identified two clusters of sequences and four separated clones. The sequences in cluster 1 grouped with those of Methanosaeta spp., whereas the sequences in cluster 2 comprised the methanogenic endosymbiont of Plagiopyla nasuta. Discriminative oligonucleotide probes were constructed against both clusters and two of the separated clones. These probes were used subsequently for the analysis of indigenous methanogens in a core of the sediment, in addition to domain-specific probes against members of the domains Bacteria and Archaea and the fluorescent stain 4', 6-diamidino-2-phenylindole (DAPI), by fluorescent in situ hybridization. After DAPI staining, the highest microbial density was obtained in the upper sediment layer; this density decreased with depth from (1.01 +/- 0.25) x 10(10) to (2.62 +/- 0.58) x 10(10) cells per g of sediment (dry weight). This zone corresponded to that of highest metabolic activity, as indicated by the ammonia, alkalinity, and pH profiles, whereas the methane profile was constant. Probes Eub338 and Arch915 detected on average 16 and 6% of the DAPI-stained cells as members of the domains Bacteria and Archaea, respectively. Probe Rotcl1 identified on average 4% of the DAPI-stained cells as Methanosaeta spp., which were present throughout the whole core. In contrast, probe Rotcl2 identified only 0.7% of the DAPI-stained cells as relatives of the methanogenic endosymbiont of P. nasuta, which was present exclusively in the upper 2 cm of the sediment. Probes Rotp13 and Rotp17 did not detect any cells. The spatial distribution of the two methanogenic populations corresponded well to the methane production rates determined by incubation with either [14C]acetate or [14C]bicarbonate. Methanogenesis from acetate accounted for almost all of the total methane production, which concurs with the predominance of acetoclastic Methanosaeta spp. that represented on average 91% of the archaeal population. Significant hydrogenotrophic methanogenesis was found only in the organically enriched upper 2 cm of the sediment, where the probably hydrogenotrophic relatives of the methanogenic endosymbiont of P. nasuta, accounting on average for 7% of the archaeal population, were also detected.

Anaerobiosis↗
PubMed1999

The functional use of the reciprocal hip mechanism during gait for paraplegic patients walking in the Louisiana State University reciprocating gait orthosis.

Reciprocally linked orthoses used for paraplegic walking have some form of linkage between the two hip joints. It has been assumed that flexion of the swinging leg is driven by extension of the stance leg. The aims of this study were to investigate the moments generated around the hip joint by the two cables in a Louisiana State University Reciprocating Gait Orthosis (LSU-RGO). Six (6) subjects were recruited from the Regional Spinal Injuries Centre at Southport, who were experienced RGO users. The cables were fitted with strain gauged transducers to measure cable tension. Foot switches were used to divide the gait into swing and stance phases. A minimum of 20 steps were analysed for each subject. Moments about the hip joint for each phase of gait were calculated. There were no moments generated by the front cable in 4 of the subjects. In only 2 subjects did the cable generate a moment that could assist hip flexion during the swing phase. These moments were very low and at best could only have made a small contribution to limb flexion. The back cable generated moments that clearly prevented bilateral flexion. It was concluded that the front cable, as used by these experienced RGO users, did not aid flexion of the swinging limb.

Biomechanical Phenomena↗