PubMed Health⌕ Search

Biomedical subjects

F Steiner

Publications and source records attributed to F Steiner.

At least 19 recordsLinked to original sources
PubMed2001

Application of hydrophobic anion-exchange phases in capillary electrochromatography.

Capillary electrochromatography (CEC) requires stationary phases that enable appropriate electroosmotic propel under various conditions. Analyte retention can be controlled through hydrophobic or electrostatic interaction with the packing material. The development and characterization of new strong anion-exchange materials with additional hydrophobic moieties (SAX/C18 mixed-mode phases) is described. The synthesis was based on polymer encapsulation of porous silica. The phases were systematically characterized by means of elemental analyses, HPLC frontal analyses and CEC experiments. The studies focused on the influence of various parameters (e.g., pH, kind of buffer, capillary wall) on the electroosmotic flow (EOF). Phases with high anion-exchange capacity generated a fast and constant EOF over a wide pH range. Long-time stability of EOF and hydrophobic retention under CEC conditions were demonstrated within the course of 100 consecutive injections. The applicability of the SAX/C18 phases in appropriate buffer systems is demonstrated for neutral, acidic and basic compounds.

Anion Exchange Resins↗
PubMed2001

The environment in the provincial plan of Cremona, Italy.

Recent Italian laws mandate the consideration of environmental factors in local plans, especially at the provincial level of government. The plan for the province of Cremona in northern Italy illustrates the integration of the environment in provincial-level planning. The Cremona plan was developed through an ecological planning approach that occurred from 1994 to 1998. As part of this process, the planning team designed an environmental sustainability index. This index was integrated with an environmental capability analysis. To improve the quality of the Cremona landscape, the planning team developed an ecological network. This network seeks to weave together the natural areas of the province, especially by connecting provincial parks to regional river parks throughout Lombardy. The experience of the Cremona provincial plan has implications for environmental management elsewhere in Italy, Europe, and abroad.

Conservation of Natural Resources↗
PubMed2001

Growth in human immunodeficiency virus type 1-infected children treated with protease inhibitors.

UNLABELLED: To determine the long-term impact of antiretroviral treatment (ART) including a protease inhibitor (PI) on growth in children infected with the human immunodeficiency virus type I (HIV-1), a prospective multi-centre study was conducted in Switzerland on HIV-1-infected children treated with ritonavir (350 mg/m2 twice a day) or nelfinavir (20-30 mg/kg three times a day) in addition to two nucleoside reverse transcriptase inhibitors. Length or height of HlV-1-infected children from before (weeks -72, -48, -24, and 0) and after (weeks +24, +48, and +72) introducing a PI to the ART were compared. To allow for age- and gender-independent assessment, values were expressed in standard deviations from the mean. Complete data sets on body length were available for 44 children after 72 weeks of treatment with a PI. Preceding initiation of a PI, there was an overall decline in growth to -0.3 SD. Following start of a PI, an increase in growth was noted from weeks 0 to +24 (+0.33 SD, P=0.02) and from weeks +48 to +72 (+0.21 SD, P=0.03). The increase in growth was restricted to children with stunting before a PI was introduced (P=0.03), and was more marked in children younger than 3 years of age. CONCLUSION: children infected with human immunodeficiency virus type 1 showed catch-up growth after addition of a protease inhibitor to their antiretroviral treatment, but this phenomenon was observed almost exclusively in children under 3 years of age.

Adolescent↗
PubMed2001

Community-acquired pneumonia in children due to Mycoplasma pneumoniae: diagnostic performance of a seminested 16S rDNA-PCR.

A 16S rDNA-PCR assay for Mycoplasma pneumoniae applied to nasopharyngeal secretion (NPS) or pharyngeal swab (PS) from children with community-acquired pneumonia (CAP) was prospectively compared to serological tests including complement fixation (CF) test, a mu-capture enzyme immuno assay (EIA) for the detection of specific IgM, and an EIA for the detection of specific IgG. During a 24-months-period diagnosis of active M. pneumoniae infection was established in 32 (12.6%) of 253 patients for whom paired sera were available. In the acute phase, the sensitivities of PCR from NPS and PS, CF test, IgM EIA, and IgG EIA were 90.0%, 79.3%, 46.9%, 78.1%, and 59.4%, respectively. The corresponding specificities were 98.1%, 98.6%, 97.6%, 87.1%, and 72.4%, respectively. Thus, the 16S rDNA-PCR assay provides a highly sensitive and accurate tool for the rapid diagnosis of M. pneumoniae infection in children with CAP.

Adolescent↗
PubMed2000

Instrumentation for capillary electrochromatography.

One of the reasons for the immense interest in capillary electrochromatography (CEC) is its feature to combine chromatographic selectivity with the high efficiency and the miniaturization potential of capillary electrophoresis (CE). The capability of commercial CE instruments to run CEC has enforced the readiness of users and researchers to work on this separation technique. Nevertheless, to fully exploit the potential of CEC, a routine CE device can certainly not fulfill all requirements. Two different approaches have been made to overcome this problem. The first was to modify commercial CE instruments for various demands. Pressurization of the packed capillary to prevent "air" bubble formation, gradient elution capabilities and thermostating devices allowing a greater flexibility in column designs have been implemented in CE instruments of several manufacturers. A completely different approach is the development of modular laboratory-made instrumentation dedicated to special CEC requirements. In order to increase mobile phase velocity and thus the speed of analysis the availability of voltages higher than 30 kV was accomplished in some of these devices. Gradient elution was achieved by either coupling of gradient LC systems or an electroosmotic generation of the changing eluent composition. When a pressure gradient is applied between both column ends in addition to the voltage gradient, a hybrid between capillary HPLC and CEC results. This chromatographic mode is named pressure-assisted electrochromatography (PEC). Either CE instruments equipped with additional HPLC pumps or modular laboratory-made devices are suitable for PEC. In CEC, sensitivity for UV detection is rather poor due to the short optical path length for on-column detection in capillary separation techniques. A special cell design with enhanced light path is presented and further principles like, e.g., fluorescence detection and coupling to mass spectrometry are discussed.

Electrophoresis, Capillary↗
PubMed2000

Nonaqueous capillary electrophoresis: a versatile completion of electrophoretic separation techniques.

Nonaqueous capillary electrophoresis (NACE) is the application of a conductive electrolyte dissolved in either one organic solvent or a mixture of several organic solvents to carry out zone electrophoresis or related techniques in fused-silica capillaries. A complete review on the fundamentals, the optimization of analytical methods, practical considerations, and applications is given. To explain the differences to CE in aqueous media, a brief summary on solvent properties and molecular interactions in solutions introduces the reader into these fields. The use of additives to tune separation selectivity by means beyond a pure zone-electrophoretic mechanism is discussed in detail for organic media. Special detection techniques providing high potential for NACE are presented. Data on the precision of NACE methods and a list of relevant applications are included. More specialized applications like the determination of physicochemical constants in NACE or the setup of a semipreparative mode are described.

Electrophoresis, Capillary↗
PubMed2000

On-line determination of mercury in river water at the German monitoring station Schnackenburg/Elbe.

A monitor is described which provides the on-line determination of mercury in river water at concentrations from 20 to 1000 ng/L. The measurement includes an on-line digestion with Br-/BrO3- and UV-radiation. Each determination is controlled by an on-line addition of 50 and 100 ng/L mercury carried out by pre-dilution of a 500 and 1000 ng/L stock solution using sequential injection analysis (SIA). One cycle of analysis takes 20 min and results in nine signals. A five days stand-alone operation has been performed successfully. Details are also published at web page: "http/www.rzbd.fh-hamburg.de/-prmercol".

Environmental Monitoring↗
PubMed2000

Long-term responses to treatment including ritonavir or nelfinavir in HIV-1-infected children. Pediatric AIDS Group of Switzerland.

BACKGROUND: Knowledge concerning the long-term antiretroviral and immunological efficacy of protease inhibitors in children is limited. PATIENTS AND METHODS: An open-label, prospective, multicenter clinical trial was conducted over a period of 72 weeks in Switzerland. 60 HIV-1 infected children (aged 0.3-16.9 years) naive to protease inhibitors were enrolled. Ritonavir or nelfinavir and at least one new nucleoside reverse transcriptase inhibitor were introduced into the current treatment regimen. HIV-1 RNA levels and CD4 cell counts were monitored after introducing the protease inhibitor, and the tolerability and safety of the drugs were assessed. RESULTS: Dictated by chronological availability, 37 children received ritonavir and 23 nelfinavir. At baseline, children given ritonavir had higher mean plasma HIV-1 RNA levels (5.03 vs 4.63 log10 copies/ml; p = 0.001) and lower mean CD4 cell counts (277 vs 555 cells/microl; p = 0.009) than children given nelfinavir. Antiretroviral treatment (ART) naive children showed higher mean plasma HIV-1 RNA levels than non-naive (5.18 vs 4.64 log10 copies/ml; p = 0.02). The decline in plasma HIV-1 RNA levels 72 weeks after treatment with ritonavir and nelfinavir was -2.17 and -1.30 log10 copies/ml, respectively (p = 0.006) and in ART-naive vs non-naive patients -2.70 vs -1.39 log10 copies/ml (p < or = 0.01). 69% of ART-naive patients and 32% of non-naive patients achieved sustained plasma HIV-1 RNA levels < 400 copies/ml. Increases in CD4 cells were higher in ART-naive compared to non-naive patients (p < 0.04). CONCLUSION: The antiretroviral and immunologic benefits of protease inhibitors are more profound in ART-naive than in non-naive children.

Adolescent↗
PubMed1999

M band proteins myomesin and skelemin are encoded by the same gene: analysis of its organization and expression.

The complete exon-intron organization of the murine gene encoding sarcomeric myomesin has been determined. The gene is composed of 38 exons and 37 introns, spanning approximately 105 kb of DNA. Intron positions and phases are essentially identical to those identified in M-protein. They are related to the modular structure of myomesin, which is composed almost entirely of immunoglobulin and fibronectin type III domains. Nearly all repeats follow a two exon-one domain structure. The start and end of each domain are defined by introns in phase I, while internal introns are more divergent in position and very rarely use phase I. Genomic Southern blotting and reverse transcription-polymerase chain reaction revealed that differential splicing of a single exon gives rise to two polypeptides, described in the literature as myomesin and skelemin, respectively. A single transcriptional start point was detected in both skeletal and cardiac muscle. Analysis of the presumptive promoter region revealed several potential regulatory elements. CAT expression assays using promoter deletion constructs identified three regions that seem to be important for the muscle-specific transcriptional activation of the myomesin gene. These results provide the basis for a comparative analysis of the regulation of myomesin and M-protein genes in vivo.

Alternative Splicing↗
PubMed1999

Prospective evaluation of amplification-boosted ELISA for heat-denatured p24 antigen for diagnosis and monitoring of pediatric human immunodeficiency virus type 1 infection.

The performance in pediatric human immunodeficiency virus type 1 (HIV-1) infection of a signal-amplification boosted ELISA for HIV-1 p24 antigen in plasma after heat-mediated immune complex dissociation was prospectively compared with polymerase chain reaction-based procedures. Diagnostic sensitivity and specificity of the p24 antigen test were 100% and 99.2%, respectively. Quantification revealed RNA in 85.7% and p24 antigen in 87.4% of 230 samples from 25 infected children. Concentrations of these indices in individual samples correlated (P<.0001). Introduction or modification of antiretroviral treatment showed concordant responses of RNA and p24 antigen in 39 (90.7%) of 43 instances. The treatment-induced changes in concentrations of RNA were higher than those of p24 antigen in 11 instances. In 1 instance, however, the concentration change of p24 antigen was greater than that of RNA (P=. 002). Variation of RNA concentrations was more marked than that of p24 antigen (P=.002). The p24 antigen test was equivalent to PCR for diagnosing and monitoring pediatric HIV-1 infection.

Anti-HIV Agents↗
PubMed1998

Structure and expression of the gene encoding murine M-protein, a sarcomere-specific member of the immunoglobulin superfamily.

The complete exon-intron organization of the murine gene encoding M-protein, a structural protein of sarcomeric myofibrils, was determined. The gene is composed of 37 exons and 36 introns, spanning approximately 75 kb of DNA. Intron positions are related to the modular structure of M-protein, which is composed essentially of immunoglobulin and fibronectin type III domains. Almost all repeats follow a two exon-one domain structure. The beginning and end of each domain are defined by introns in phase I; internal introns are more divergent in position and very rarely use phase I. A single transcriptional start point was detected in both skeletal and cardiac muscle. Analysis of the prospective promoter region revealed several potential regulatory elements. CAT expression assays using promoter deletion constructs identified three regions that seem to be most important for the muscle-specific transcription activation of the M-protein gene. These results provide the first complete characterization of a gene for a member of the intracellular branch of the immunoglobulin superfamily.

Amino Acid Sequence↗
PubMed1998

Cardiopulmonary bypass primes polymorphonuclear leukocytes.

Polymorphonuclear leukocyte (PMN) superoxide (.O2-) production has been implicated in the pathogenesis of cardiopulmonary bypass (CPB)-related end organ injury. PMN "priming" has been described as an event which enhances the release of .O2- following a second, activating insult. We hypothesized that PMN priming occurs during CBP and is temporally related to the plasma level of complement (C3a), interleukin (IL)-6, and IL-8. PMNs were isolated from 10 CPB patients pre-bypass (preCPB), 5 min after protamine administration (PROT), and at 6 and 24 h post-CPB. PMN .O2- production was measured by a cytochrome c reduction assay in the presence or absence of either phorbol 12-myristate-13-acetate (PMA, 0.4 microgram/ml) or N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 microM) and also after priming with 2000 nM platelet-activating factor (PAF) followed by activation with either PMA or FMLP. Plasma levels of C3a, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay. PMA-activated PMN .O2- production was significantly elevated at 6 h post-CPB compared to pre-CPB levels (11.04 +/- 0.9 vs 7.62 +/- 0.57, P = 0.009), indicating that CPB is associated with in vivo PMN priming. When PMNs were primed in vitro with PAF and then activated with PMA or FMLP, .O2- release at 6 h post-CPB was also significantly greater than pre-CPB levels (16.04 +/- 0.74 vs 12.2 +/- 0.92, P = 0.038; and 17.33 +/- 1.38 vs 13.33 +/- 1.35, P < 0.05), indicating that CPB acts synergistically with PAF to prime PMNs. Levels of C3a rose significantly over pre-CPB levels at PROT (P = 0.001), and IL-6 and IL-8 rose over pre-CPB levels at 6 h post-CPB (P = 0.01 and P = 0.006, respectively). These findings demonstrate that CPB not only directly primes PMNs, but also potentiates priming of PMNs by PAF. This "primed" PMN state, which coincided with the increased plasma levels of inflammatory mediators, may suggest a mechanism of predisposition to organ dysfunction following CPB.

Aged↗
PubMed1998

Mapping of a myosin-binding domain and a regulatory phosphorylation site in M-protein, a structural protein of the sarcomeric M band.

The myofibrils of cross-striated muscle fibers contain in their M bands cytoskeletal proteins whose main function seems to be the stabilization of the three-dimensional arrangement of thick filaments. We identified two immunoglobin domains (Mp2-Mp3) of M-protein as a site binding to the central region of light meromyosin. This binding is regulated in vitro by phosphorylation of a single serine residue (Ser76) in the immediately adjacent amino-terminal domain Mp1. M-protein phosphorylation by cAMP-dependent kinase A inhibits binding to myosin LMM. Transient transfection studies of cultured cells revealed that the myosin-binding site seems involved in the targeting of M-protein to its location in the myofibril. Using the same method, a second myofibril-binding site was uncovered in domains Mp9-Mp13. These results support the view that specific phosphorylation events could be also important for the control of sarcomeric M band formation and remodeling.

Amino Acid Sequence↗
PubMed1997

Lexipafant inhibits platelet activating factor enhanced neutrophil functions.

Platelet activating factor (PAF) enhances polymorphonuclear leukocyte (PMN) superoxide (.O2-) production, CD11b expression, and elastase release, all essential components in the pathophysiology of multiple-organ failure. This study was designed to determine the effects of Lexipafant, a PAF receptor antagonist, on PAF-mediated PMN functions. PMNs from 10 healthy volunteers were isolated and pretreated with various concentrations of Lexipafant (0-100 microM). PMNs were then incubated for 5 min with 200 nM PAF for .O2- detection or 2000 nM PAF for elastase measurement and activated with 1 microM N-formylmethionylleucylphenylalanine. The mean rate of .O2- production was determined by a cytochrome c reduction assay (nmole .O2-/min/1.33 x 10(5) PMN +/- SEM). Elastase release was measured by the cleavage of the synthetic elastase substrate Meo-Suc-Ala-Ala-Pro-Val-pNA (mean elastolytic activity +/- SEM). In parallel experiments, PMNs were incubated with 200 nM PAF for 30 min following pre-treatment with Lexipafant and CD11b expression was determined by flow cytometry (mean fluorescence intensity +/- SEM). Statistical analysis was performed using repeated-measures ANOVA (P < 0.05). Lexipafant inhibited PAF-enhanced PMN .O2- generation, CD11b expression and elastase release in a dose dependent fashion. The IC50 of Lexipafant for .O2- production, CD11b expression, and elastase release was 0.046, 0.285, and 0.05 microM, respectively. Lexipafant attenuated the PAF-mediated upregulation of PMN .O2- production, CD11b expression, and elastase release in a dose dependent fashion. These data support the hypothesis that Lexipafant may reduce the severity of the inflammatory response to injury produced by PAF-enhanced activation of PMNs.

Dose-Response Relationship, Drug↗
PubMed1997

Mutation of ornithine transcarbamylase (H136R) in a girl with severe intermittent orotic aciduria but normal enzyme activity.

Ornithine transcarbamylase deficiency shows X-linked inheritance with partial dominant expression in carrier females. We studied a girl with intermittent severe orotic aciduria and mild hyperammonaemia despite apparently normal enzyme activity in the liver. Sequence analysis of all 10 exons of the ornithine transcarbamylase gene revealed a novel A-->G exchange (A502G) in exon 5 which changes His-136 to arginine in the ornithine transcarbamylase protein. Km values for carbamyl phosphate and ornithine determined in the patient's liver were comparable to those of wild-type enzyme but, unlike the wild-type enzyme, the mutant enzyme was unstable upon freezing and thawing. Electron microscopy revealed several giant mitochondria with paracrystalline inclusions. The results are compatible with the assumption that the mutant enzyme cannot form a functional complex with carbamyl phosphate synthetase and the ornithine carrier, resulting in decreased availability of substrates and diminished enzyme activity in vivo.

Ammonia↗
PubMed1996

The structure of the sarcomeric M band: localization of defined domains of myomesin, M-protein, and the 250-kD carboxy-terminal region of titin by immunoelectron microscopy.

The M band of vertebrate cross-striated myofibrils has remained an enigmatic structure. In addition to myosin thick filaments, two major structural proteins, myomesin and M-protein, have been localized to the M band. Also, titin is expected to be anchored in this structure. To begin to understand the molecular layout of these three proteins, a panel of 16 polyclonal and monoclonal antibodies directed against unique epitopes of defined sequence was assembled, and immunoelectron microscopy was used to locate the position of the epitopes at the sarcomere level. The results allow the localization and orientation of defined domains of titin, myomesin, and M-protein at high resolution. The 250-kD carboxy-terminal region of titin clearly enters the M band with the kinase domain situated approximately 52 nm from the central M1-line. The positions of three additional epitopes are compatible with the view that the titin molecule reaches approximately 60 nm into the opposite sarcomere half. Myomesin also seems to bridge the central M1-line and is oriented parallel to the long axis of the myofibril. The neighboring molecules are oriented in an antiparallel and staggered fashion. The amino-terminal portion of the protein, known to contain a myosin binding site, seems to adopt a specific three-dimensional arrangement. While myomesin is present in both slow and fast fibers, M-protein is restricted to fast fibers. It appears to be organized in a fundamentally different manner: the central portion of the polypeptide is around the M1-line, while the terminal epitopes seem to be arranged along thick filaments. This orientation fits the conspicuously stronger M1-lines in fast twitch fibers. Obvious implications of this model are discussed.

Animals↗