Search PubMed⌕ Search

Biomedical subjects

S Steiner

Publications and source records attributed to S Steiner.

At least 19 recordsLinked to original sources
PubMed2001

Cholesterol biosynthesis regulation and protein changes in rat liver following treatment with fluvastatin.

The enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is a key regulator in cholesterol biosynthesis and HMG CoA reductase inhibitors (statins) have become a widely prescribed family of lipid lowering agents. Cholesterol synthesis occurs predominantly in liver which is the target organ of statins. We studied the effects of fluvastatin (Lescol), a member of the statin family, on hepatic protein regulation. Male F344 rats treated with 0.8 mg/kg per day fluvastatin or 24 mg/kg per day fluvastatin for 7 days showed treatment-related changes in 58 liver proteins (P<0.005). Major effects were evident in the cholesterol biosynthesis pathway including the induction of enzymes upstream and downstream of the target enzyme HMG CoA reductase. Treatment also triggered alterations in key enzymes of carbohydrate metabolism and was associated with changes in a heterogeneous set of cellular stress proteins involved in cytoskeletal structure, calcium homeostasis and protease activity. The latter set of protein alterations indicates that hepatotoxicity is associated with high-dose treatment. Based on the results it is suggested that HMG-CoA synthase and isopentenyl-diphosphate delta-isomerase may be explored as alternative drug targets and that the induction levels of these enzymes may serve as a measure of potency of individual statin drugs. It is proposed that efficacy and cellular stress markers discovered in this study may be used in a high throughput screen (HTS) assay format to compare efficiently and accurately the therapeutic windows of different members of the statin family.

Animals↗
PubMed2001

Precious things come in little packages.

The 110-amino acid multidrug transporter from E. coli, EmrE, is a member of the family of MiniTexan or Smr drug transporters. EmrE can transport acriflavine, ethidium bromide, tetraphenylphosphonium (TPP+), benzalkonium and several other drugs with relatively high affinities. EmrE is an H+/drug antiporter, utilizing the proton electrochemical gradient generated across the bacterial cytoplasmic membrane by exchanging two protons with one substrate molecule. The EmrE multidrug transporter is unique in its small size and hydrophobic nature. Hydropathic analysis of the EmrE sequence predicts four alpha-helical transmembrane segments. This model is experimentally supported by FTIR studies that confirm the high alpha-helicity of the protein and by high-resolution heteronuclear NMR analysis of the protein structure. The TMS of EmrE are tightly packed in the membrane without any continuous aqueous domain, as was shown by Cysteine scanning experiments. These results suggest the existence of a hydrophobic pathway through which the substrates are translocated. EmrE is functional as a homo-oligomer as suggested by several lines of evidence, including co-reconstitution experiments of wild-type protein with inactive mutants in which negative dominance has been observed. EmrE has only one membrane embedded charged residue, Glu-14, that is conserved in more than fifty homologous proteins and it is a simple model system to study the role of carboxylic residues in ion-coupled transporters. We have used mutagenesis and chemical modification to show that Glu-14 is part of the substrate-binding site. Its role in proton binding and translocation was shown by a study of the effect of pH on ligand binding, uptake, efflux and exchange reactions. We conclude that Glu-14 is an essential part of a binding site, common to substrates and protons. The occupancy of this site is mutually exclusive and provides the basis of the simplest coupling of two fluxes. Because of some of its properties and its size, EmrE provides a unique system to understand mechanisms of substrate recognition and translocation.

Amino Acid Sequence↗
PubMed2000

Expression profiling in toxicology--potentials and limitations.

Recent progress in genomics and proteomics technologies has created a unique opportunity to significantly impact the pharmaceutical drug development processes. The perception that cells and whole organisms express specific inducible responses to stimuli such as drug treatment implies that unique expression patterns, molecular fingerprints, indicative of a drug's efficacy and potential toxicity are accessible. The integration into state-of-the-art toxicology of assays allowing one to profile treatment-related changes in gene expression patterns promises new insights into mechanisms of drug action and toxicity. The benefits will be improved lead selection, and optimized monitoring of drug efficacy and safety in pre-clinical and clinical studies based on biologically relevant tissue and surrogate markers.

Animals↗
PubMed2000

Evidence for the impairment of the vitamin D activation pathway by cyclosporine A.

Cyclosporine A (CsA) is a potent immunosuppressant with the drawback of renal side effects. We reported that CsA markedly decreases calcium-binding protein calbindin-D28k mRNA levels in rat kidneys, and showed that this decrease is associated with its adverse renal effects. The transcription of the calbindin-D28k gene is activated via the vitamin D pathway. In this work, the potential CsA-mediated impairment of the vitamin D pathway was investigated. Wistar rats were treated for 12 days with 50 mg/kg/day CsA or for 20 days with 50 mg/kg/day of the non-immunosuppressant and non-nephrotoxic SDZ PSC 833, which had been previously shown not to affect calbindin-D28k mRNA levels. The expression of the three vitamin D-regulated genes calbindin-D28k, 1,25-dihydroxyvitamin D3-24-hydroxylase (24-OHase), and vitamin D receptor (VDR) were quantified in rat kidney homogenates by real-time reverse transcription-polymerase chain reaction. Plasma parathyroid hormone (PTH) as well as plasma and kidney 1,25 dihydroxyvitamin D3 (calcitriol) levels were monitored in all animals. CsA induced a 85% decrease in calbindin-D28k mRNA levels as well as a 40% and 69% decrease in VDR and 24-OHase mRNA levels, respectively. Plasma and kidney 1,25 dihydroxyvitamin D3 as well as plasma PTH levels were increased by CsA, but not by SDZ PSC 833. The treatment with SDZ PSC 833 did not affect calbindin-D28k or VDR expression, but did cause a 73% decrease in 24-OHase mRNA levels. Taken together, these results indicate an association between CsA-mediated down-regulation of rat renal calbindin-D28k mRNA and the decrease in other 1,25 dihydroxyvitamin D3-regulated genes, suggesting an impairment of the vitamin D pathway by CsA which may be related to its adverse renal side effects and its immunosuppressive activity.

Animals↗
PubMed2000

Proteomics: applications and opportunities in preclinical drug development.

Advances in DNA sequencing and the near-term availability of whole genome sequences for several pharmaceutically relevant organisms promise to dramatically alter the breadth and scale of high-throughput proteomic studies. The substantial amount of literature is available in the public domain, demonstrate the potential of proteomics in the preclinical phases of pharmaceutical development. Over the next few years, it is anticipated that functional genomics and proteomics will have major impacts on the clinical phases of drug development. Expected benefits are earlier proof-of-concept studies in man and increased efficiency of clinical trials through the availability of biologically relevant markers for drug efficacy and safety.

Drug Design↗
PubMed2000

Two-dimensional electrophoresis of liver proteins: characterization of a drug-induced hepatomegaly in rats.

Two-dimensional electrophoresis (2-DE) of liver proteins was applied to further characterize an unusual drug-induced increase in hepatocellular rough endoplasmic reticulum (RER) in Sprague-Dawley rats given a substituted pyrimidine derivative. Absolute liver weights of drug-treated rats (9.9 +/- 0.4 g) increased above vehicle-treated controls (7.2 +/- 0.2 g) by 37%. Light microscopy revealed diffuse granular basophilia of the hepatocellular cytoplasm, uncharacteristic of hepatocytes and suggested cells rich in ribosomes, which was confirmed by electron microscopy. Immunostaining for cell proliferation, viz., 5-bromo-2'-deoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA), indicated marked hepatocellular proliferative activity. 2-DE of solubilized liver using an ISO-DALT gel system indicated significant (p<0.001) quantitative changes in at least 17 liver proteins (12 increased, 5 decreased) compared to controls. The protein with the largest increase was homologous to acute-phase reactant, contrapsin-like protein inhibitor-6. Other markedly upregulated proteins were methionine adenosyltransferase, a catalyst in methionine/ATP metabolism and mitochondrial HMG-CoA synthase, involved in cholesterol synthesis. The complementary strategies of 2-DE coupled either with database spot mapping or protein isolation and amino acid sequencing successfully identified a subset of proteins from xenobiotic-damaged rodent livers, the expression of which differed from controls. However, the current bioinformatics platform for rodent hepatic proteins and limited knowledge of specific protein functionality restricted application of this proteomics profile to further define a mechanistic basis for this unusual hepatotoxicity.

Animals↗
PubMed2000

Proteomics to display lovastatin-induced protein and pathway regulation in rat liver.

Lovastatin is a lipid lowering agent that acts by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a key regulatory enzyme in cholesterol biosynthesis. In this study the pattern of gene network regulation induced in hepatic proteins as a response to lovastatin treatment was analyzed by proteomics. In livers of male F344 rats treated with 1.6 mg/kg/day lovastatin or 150 mg/kg/day lovastatin for seven days, 36 proteins were found to be significantly altered (p<0.001) in relation to treatment. The changed proteins were classified according to their cellular function and participation in biochemical pathways. The following observations were made: (i) inhibition of HMG-CoA reductase provoked a regulatory response in the cholesterol synthesis pathway including the induction of cytosolic HMG-CoA synthase and of isopentenyl-diphosphate delta-isomerase, (ii) manipulation of the lipid metabolism triggered alterations in key enzymes of the carbohydrate metabolism, and (iii) lovastatin treatment was associated with signs of toxicity as reflected by changes in a heterogeneous set of cellular stress proteins involved in functions such as cytoskeletal structure, calcium homeostasis, protease inhibition, cell signaling or apoptosis. These results present new insights into liver gene network regulations induced by lovastatin and illustrate a yet unexplored application of proteomics to discover new targets by analysis of existing drugs and the pathways that they regulate.

Amino Acids↗
PubMed2000

Sudden onset of EDTA-dependent pseudothrombocytopenia after therapy with the glycoprotein IIb/IIIa antagonist c7E3 Fab.

The development of thrombocytopenia following exposure to the platelet glycoprotein (GP) IIb/ IIIa receptor antagonist abciximab (c7E3 Fab, ReoPro) is associated with adverse clinical outcome and excessive bleeding. Pseudothrombocytopenia is an important differential diagnosis in sudden onset of thrombocytopenia in a patient treated with c7E3 Fab. We report on a case of documented sudden onset of EDTA-dependent pseudothrombocytopenia in a 63-year-old woman who was admitted for emergency coronary intervention. Four hours after bolus administration of c7E3 Fab, the platelet concentration in EDTA-anticoagulated blood decreased from 385 x 10(9)/l to 119 x 10(9)/l, and it showed a further decrease to 57 x 10(9)/l at the end of a 12-h infusion. Despite no warnings or abnormalities of the automated cell counter, platelet aggregates were observed by microscopic evaluation of the blood smear. Repeated platelet counts in citrate-anticoagulated samples revealed platelet concentrations within the reference range. EDTA-dependent pseudothrombocytopenia due to therapy with c7E3 Fab is an important differential diagnosis that needs to be excluded rapidly from other causes of thrombocytopenia to avoid unnecessary further examinations, discontinuation of therapy, or even initiation of inappropriate therapy.

Abciximab↗
PubMed2000

Proteomics: applications in basic and applied biology.

The rapid evolution of proteomics has continued during the past year, with a series of innovations in the core technologies of two-dimensional electrophoresis and mass spectrometry, and a diversity of productive research programmes. Well-annotated proteomics databases are now emerging in a number of fields to provide a platform for systematic research, with particularly promising progress in clinical applications such as cardiology and oncology. Large-scale quantitative research, comparable in power and sensitivity to that achieved for gene expression, is thus becoming a reality at the protein level.

Databases, Factual↗
PubMed2000

Pharmaceutical proteomics.

Genomics and proteomics are today well established in drug discovery and, in combination with combinatorial chemistry and high-throughput screening, are helping to bring forward an unprecedented number of potential lead compounds. To avoid the generation of bottlenecks downstream in drug development, increasing pressure is arising to integrate these technologies into the development environment. Proteomics has demonstrated proof-of-concept in toxicology as shown by a number of successful applications in mechanistic toxicology and lead selection. The "technology wave" is now starting to impact the clinical phase of drug development. Expected benefits are optimized clinical trials based on the availability of biologically relevant markers of drug efficacy and safety.

Animals↗
PubMed1999

4-chloro-o-phenylenediamine induces a dose-related increase in G:C > T:A transversions and one major DNA adduct in the liver of Big Blue mice after 26 weeks in feed treatment.

The monocyclic aromatic amine 4-chloro-o-phenylenediamine (4-C-o-PDA), a known mutagen and mouse hepatocarcinogen, was tested for its in vivo mutagenic potential in the Big Blue transgenic mouse assay system. Genomic DNA was isolated from liver tissue of control and treated animals and lacI mutants were recovered. In an initial 2-week study 4-C-o-PDA was administered daily per os to groups of male and female C57BL/6 Big Blue mice at doses of 0 and 200 mg/kg for 2 weeks (on working days) followed by a treatment free expression time of 10 days. Only a weak increase in the mutant frequencies in females was observed. In a 26-week study, where 4-C-o-PDA was given to groups of male and female Big Blue mice in feed at dietary concentrations of 0, 5,000 and 10,000 ppm, 4-C-o-PDA was found to induce a pronounced dose-dependent increase in mutant frequencies in either sex. In the present work, we analyzed the mutation spectrum by automated DNA sequencing of lacI mutants from both studies. Following the 2-week administration of 4-C-oT:A transversions in both sexes. In addition, upon 26-week treatment with 4-C-o-PDA, one major DNA adduct was detected by 33P postlabelling and subsequent multidimensional thin layer chromatography. It is concluded that 4-C-oT:A transversions after 26 weeks in feed treatment. This result indicates that the sensitivity of the Big Blue transgenic assay system, in detecting a unique chemically induced mutation spectrum, is dependent on experimental parameters, such as treatment time. The data suggest that the formation of one major DNA adduct upon 4-C-o-PDA treatment may be critical for its mutagenicity.

Adenine↗
PubMed1999

[Development of evidence-based clinical practice guidelines; a model project integrating external evidence and clinical expertise].

BACKGROUND: Internationally, evidence-based clinical practice guidelines have been established for several years. In Germany, they are now gaining increasing importance. OWN STUDIES: The Institute of Health Economics and Clinical Epidemiology at the University of Cologne has developed a mostly standardized process for evidence-based guideline development. This process has been implemented in such a way that reproducibility, validity and practicability of guidelines can be assured: evidence from research (external evidence) has been searched and evaluated according to the criteria of the Agency of Health Care Policy and Research (AHCPR). Through cooperation with clinical experts, this evidence has been transferred into practicable recommendations. In addition, acceptance of guideline users and patients was improved by applying this method. CONCLUSION: Evidence-based guidelines are considered as an appropriate tool to assist medical decision-making of all stakeholders involved. The process will be demonstrated developing an evidence-based guideline for obesity treatment.

Evidence-Based Medicine↗
PubMed1999

Congenital asplenia detected in a 60 year old patient with septicemia.

A 60 year-old female who had never been seriously ill, was brought to the emergency ward after she had been found somnolent at home. She developed renal failure, meningitis, respiratory distress and disseminated intravascular coagulation. Overwhelming septicemia was evident, and streptococcus pneumoniae was isolated from blood and cerebrospinal fluid. Surprisingly, peripheral blood smears showed numerous Howell-Jolly-bodies, indicating severe impairment of splenic function. On abdominal ultrasound, CT-scan, and scintigraphy no spleen could be detected. There was no history of abdominal surgery. Apparently, congenital asplenia, which was not noticed until the age of 60, was responsible for the patient's life-threatening septicemia. We suggest that, in cases of severe septicemia, the examination of a blood smear is useful to detect functional (or congenital) asplenia.

Bacteremia↗
PubMed1999

Compact organization of rRNA genes in the filamentous fungus Ashbya gossypii.

The rDNA cluster in the phytopathogenic fungus Ashbya gossypii consists of approximately 50 tandem repeat units of 8197 bp. Each unit carries a gene for the 35S pre-rRNA, processed into 18S, 5.8S and 25S rRNA, and a divergently transcribed gene for 5S rRNA. The well-characterized rDNA of the yeast Saccharomyces cerevisiae is the only other example of a completely sequenced rDNA unit (9137 bp) carrying both a 35S pre-rRNA and a 5S rRNA gene. The coding regions for the 5S, 5.8S, 18S and 25S rRNAs are 95-100% identical whereas transcribed and non-transcribed spacers show 43-66% sequence identity. Functionally characterized rDNA and rRNA elements of S. cerevisiae can be unambiguously recognized in the A. gossypii sequence, including the RNA polymerase-I transcription start site, two Reb1p enhancer binding sites and numerous recognition sequences for rRNA modification and processing. In addition to these functionally characterized sequences eight highly conserved elements from 10 to 71 bp were detected in the over 600-bp transcribed region upstream of the 18S rRNA gene which most likely play as yet uncharacterized functions at the DNA or RNA level. In addition to this work we started to identify A. gossypii homologs of S. cerevisiae nucleolar proteins involved in rDNA maturation.

Amino Acid Sequence↗
PubMed1999

[Influence of pulmonary hemodynamics on right ventricular ejection fraction in chronic obstructive pulmonary disease].

Right ventricular dysfunction is common in patients with chronic obstructive pulmonary disease. Right ventricular function might be influenced by the afterload, which depends on pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). To evaluate the influence of the right ventricular afterload on right ventricular performance, we investigated 30 patients with chronic obstructive pulmonary disease without clinical signs or history of left heart failure or coronary heart disease. The study includes lung function tests, analysis of blood gases and right heart catheterisation. RV function was assessed by a thermodilution technique using a pulmonary artery catheter equipped with a rapid response thermistor (produced by Baxter, USA). There are 9 patients with normal, 12 with latent and 9 with fixed pulmonary hypertension. Median RVEF was measured to be 33.3% (19-44%). There was a significant correlation between RVEF and PAP (r = -0.66; p < 0.0001) and RVEF and PVR (r = -0.54; p < 0.0018). RVEF was not directly influenced by lungfunction or pulmonary capillary wedge pressure (PCWP). Under treadmill exercise RVEF and cardiac index increased without a change of PCWP. A low RVEF at rest seems to be a predictive value for a reduced exercise capacity. A reduced RVEF has a predictive value of pulmonary hypertension with a sensitivity of 66% in patients with unstable and 89% in patients with lasting pulmonary hypertension. In a subgroup of 6 cases treadmill exercise led to a RVEF decrease. These patients showed no difference in afterload, blood gases or lung function-tests compared with the total group. In conclusion, right ventricular ejection fraction seems to be influenced by PVR and PAP which determinate the right ventricular afterload. The validity of the method depends on the severity of pulmonary hypertension, and hence measurement of RVEF might not provide a reliable estimation of pulmonary arterial pressure in patients suffering from mild to moderate pulmonary hypertension.

Female↗