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Biomedical subjects

R Müller

Publications and source records attributed to R Müller.

At least 217 records · Page 12Linked to original sources
PubMed1998

Generation of infectious retrovirus aerosol through medical laser irradiation.

A novel model system was used to investigate the spread of infectious particles and live cells through the application of lasers commonly used in clinical medicine. Supernatants from a cell line producing recombinant retroviruses carrying a marker gene (neoR) were exposed to Er:YAG-laser beams. Aerosols were collected from various sites and distances from the point of laser impact and were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for neoR. In addition, a susceptible indicator cell line was used to investigate the presence of infectious virions in collected aerosols. To test the possibility of dissemination of viable cells, a cell line was laser irradiated, and the generated aerosols were analyzed for the presence of viable cells. The viral marker gene neoR could be detected in 16% (distance: 5.0-6.3 cm) to 59% (0.5-1.6 cm) of wells adjacent to the point of laser impact. The presence of infectious viruses in laser vapors conferring G418 resistance could be detected in 3% (distance 5.0-6.3 cm) to 20% (distance: 0.5-1.6 cm) of wells containing susceptible cells, and subsequent PCR analysis of isolated resistant clones revealed the presence of neoR-RNA and -DNA. Viable cells were detected in 40% (distance 0.7-3.6 cm) to 3% (distance 10.7-11.8 cm) of wells adjacent to the point of laser impact. These results demonstrate that laser vapors can contain infectious viruses, viral genes, or viable cells and may promote the spread of infections or tumor cell dissemination.

3T3 Cells↗
PubMed1998

Extrathymic T cell differentiation in vitro from human CD34+ stem cells.

Although it is well established that T cells are derived from CD34+ stem cells in vivo, and that T cells can develop in the absence of a functioning thymus, it has not proven possible thus far to generate human T cells in vitro from CD34+ cells in the absence of any thymic influence. We now present a limiting dilution cloning culture system that supports the differentiation of highly purified human CD34+ cells to CD3+ T cells in vitro in the complete absence of any thymic components. The culture system features the use of a serum-free medium supplemented with a cocktail of cytokines including flt-3 ligand, interleukin-3 (IL-3), stem cell factor (SCF), and IL-2. CD4+ T cell clones capable of mitogen-stimulated proliferation and response to IL-2, and expressing a varied TCR-Vbeta repertoire were obtained under these conditions. This culture system therefore supports human T lymphopoiesis in the absence of any thymic influence and may prove useful for the evaluation of extrathymic T cell differentiation in vitro.

Animals↗
PubMed1998

[Percutaneous suture of femoral artery access sites after diagnostic heart catheterization and or coronary intervention. Safety and effectiveness of a new arterial suture technic].

UNLABELLED: The safety and efficacy of a suture-based closure device designed to achieve hemostasis at the femoral access site post catheterization procedures was compared to manual compression in a 600 patients randomized trial (data available for 590 patients). The patients were randomized to percutaneous vascular surgery (PVS) or manual compression after diagnostic (401 patients) and interventional (189 patients) procedures. Two types of PVS devices were used delivering 1 or 2 sutures at the arterial access site. The overall results as well as the results by procedure type demonstrated a significant reduction in time of hemostasis (7.8 +/- 4.8 min vs 19.6 +/- 13.2 min, p < 0.01) and time to ambulation (4.5 +/- 6.5 hours vs 17.8 +/- 5.0 hours, p < 0.01) with the use of the PVS device. The safety results showed no significant differences in the incidence of vascular complications (5.7% for PVS vs 11.3% for compression) in the overall population or in the interventional patients subset (8.4% for PVS vs 9.6% for compression). However, the PVS device demonstrated a significant reduction in the incidence of vascular complications post diagnostic catheterization procedures (4.4 for PVS vs 12.1% for compression, p < 0.05). The incidence of vascular complications and the time of hemostasis was similar in an American multicenter study (STAND II). CONCLUSION: Percutaneous vascular surgery is a safe and effective method to achieve hemostasis post catheterization procedure providing faster hemostasis and ambulation without increasing the rate of complication.

Cardiac Catheterization↗
PubMed1998

[Toy cap pistols and their effect on hearing].

In order to understand the repeated occurrences of auditory impairments caused by toy pistols, an analysis of the circumstances involved was performed at Justus-Liebig University of Giessen. The acoustic impact of toy pistols on the ear was determined with a special measuring system for impulse noise. Results were compared with the acoustic impacts of the G3 common rifle of the German military on the ear of the soldier. It was apparent that all of the five randomly selected types of toy pistols were much louder than the military rifle, if fired close to the ear. The current standard of the European Union related to the safety of toys (EN 71-1) tolerates peaks of impulse noise from toy pistols that are actually illegal for workplaces without auditory protection. Measurements showed that the toy pistols tested were even louder than that tolerated by the EU standard. Problems related to acute acoustic trauma caused by these toys are discussed using recent examples. In order to prevent such injuries, we suggest limiting the loudness of the "worst case" instead of using unrealistic measurements.

Auditory Fatigue↗
PubMed1998

Synthesis of a neoglycoprotein containing the Lewis X analogous trisaccharide beta-D-GalpNAc-(1-->4)[alpha-L-Fucp-(1-->3)]-beta-D-GlcpNAc.

The trisaccharide allyl glycoside 36 and related disaccharide part structures have been prepared using the 2-trichloroacetamido-2-deoxy-alpha-D-galactopyranosyl trichloroacetimidate derivative 9 as glycosyl donor under promotion with TMSOTf or Sn(OTf)2, respectively, to produce the beta-(1-->4) linkage to suitably protected glucosamine derivatives in fair yields. Fucosylation was effected employing the ethyl 1-thio glycosyl donor 20 in the presence of IDCP. Deprotection of the intermediates afforded the disaccharide allyl glycosides beta-D-GalpNAc-(1-->4)- beta-D-GlcpNAc 13, beta-D-GalpNClAc-(1-->4)-beta-D-GlcpNAc 14, alpha-L-Fucp-(1-->3)-beta-D-GlcpNAc 24, alpha-L-Fucp-(1-->4)-beta-D- GlcpNAc 31 and the branched trisaccharide allyl glycoside beta-D-GalpNAc-(1-->4)[alpha-L-Fucp-(1-->3)]-beta-D-GlcpNAc 36. The trisaccharide which corresponds to a structural motif occurring in N-glycoprotein glycans from human urokinase, human recombinant protein C, phospholipase A2 as well as O-glycans, was converted into a neoglycoprotein following introduction of a cysteamine-derived spacer group and subsequent activation with thiophosgene.

Carbohydrate Sequence↗
PubMed1998

Biosynthesis of the ansamycin antibiotic rifamycin: deductions from the molecular analysis of the rif biosynthetic gene cluster of Amycolatopsis mediterranei S699.

BACKGROUND: The ansamycin class of antibiotics are produced by various Actinomycetes. Their carbon framework arises from the polyketide pathway via a polyketide synthase (PKS) that uses an unusual starter unit. Rifamycin (rif), produced by Amycolatopsis mediterranei, is the archetype ansamycin and it is medically important. Although its basic precursors (3-amino-5-hydroxy benzoic acid AHBA, and acetic and propionic acids) had been established, and several biosynthetic intermediates had been identified, very little was known about the origin of AHBA nor had the PKS and the various genes and enzymes that modify the initial intermediate been characterized. RESULTS: A set of 34 genes clustered around the rifK gene encoding AHBA synthase were defined by sequencing all but 5 kilobases (kb) of a 95 kb contiguous region of DNA from A. mediterranei. The involvement of some of the genes in the biosynthesis of rifamycin B was examined. At least five genes were shown to be essential for the synthesis of AHBA, five genes were determined to encode the modular type I PKS that uses AHBA as the starter unit, and 20 or more genes appear to govern modification of the polyketide-derived framework, and rifamycin resistance and export. Putative regulatory genes were also identified. Disruption of the PKS genes at the end of rifA abolished rifamycin B production and resulted in the formation of P8/1-OG, a known shunt product of rifamycin biosynthesis, whereas disruption of the orf6 and orf9 genes, which may encode deoxysugar biosynthesis enzymes, had no apparent effect. CONCLUSIONS: Rifamycin production in A. mediterranei is governed by a single gene cluster consisting of structural, resistance and export, and regulatory genes. The genes characterized here could be modified to produce novel forms of the rifamycins that may be effective against rifamycin-resistant microorganisms.

Actinobacteria↗
PubMed1998

Physiology and biochemistry of the pseudobranch: an unanswered question?

The structure and function of the pseudobranch has long interested scientists, but its overall role has remained a mystery. Previous studies have attributed respiratory, endocrine, osmoregulatory and sensory roles to the pseudobranch, and the present review concentrates on new findings. Perfusion experiments on the pseudobranch of the rainbow trout (Oncorhynchus mykiss) using both erythrocyte suspensions and Ringer solution have shown that this organ is able to generate values for the respiratory quotient (RQ) greater than 1.0. The release of carbon dioxide into the perfusate was found to be largely independent of flow between perfusion rates of 120-190 microl/min and could be inhibited by acetazolamide (10(-5) M), indicating a role for carbonic anhydrase. Noradrenaline (10(-5) M) had no effect on oxygen consumption or carbon dioxide release of the pseudobranch. The rate of carbon dioxide release was also dependent on the pH of the pre-pseudobranch perfusate, carbon dioxide release being reduced at lower perfusate pH values. Based on the glucose balance of the isolated saline-perfused rainbow trout pseudobranch and on the enzyme profiles for the rainbow trout, cod, swordfish and deep-water grenadier pseudobranch, it is suggested that the pentose phosphate shunt might be a source of carbon dioxide, yielding the high RQ values found for this organ. Most evidence now available indicates that the pseudobranch is integrally linked with the choroid rete and the supply of oxygen to the retina of the fish eye.

Animals↗
PubMed1998

Morphometric analysis of human bone biopsies: a quantitative structural comparison of histological sections and micro-computed tomography.

As a part of the European Union BIOMED I study "Assessment of Bone Quality in Osteoporosis," the trabecular structure of transiliac bone biopsies was assessed by conventional histomorphometry and by three-dimensional microcomputed tomography (microCT). Sixty-three cylindrical human transiliac bone specimens were obtained post mortem from 27 women and 36 men (age 23-92 years) and evaluated morphometrically in this study. For the conventional histomorphometric analysis, a pair of four undecalcified sections were prepared from two regions in the mediolateral plane of the bone cores. The sections were stained with the von Kossa technique to obtain high-contrast two-dimensional images. Prior to the histologic sectioning the samples were measured with a desktop microCT, providing a 14 microm nominal resolution. The morphometric parameters computed by both methods in two or three dimensions, respectively, were bone volume density (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). Results showed highly significant (p < 0.0001) correlations between conventional histology and microCT for BV/TV (r = 0.93), BS/TV (r = 0.91), Tb.Th (r = 0.84), and Tb.Sp (r = 0.91). The mean percentage differences between histology and microCT ranged from 2.5% (BV/TV) to 6.1% (Tb.Th). The high correlations and the low differences in terms of absolute numbers between conventional histomorphometric and microtomographic analysis are very promising for the use of micro-tomographic imaging. MicroCT is a nondestructive, fast, and very precise procedure that allows the measurement of cancellous and compact bone in unprocessed biopsies or small bones, as well as a fully automatic determination of three-dimensional morphometric indices.

Adult↗
PubMed1998

Do quantitative ultrasound measurements reflect structure independently of density in human vertebral cancellous bone?

Ultrasonic measurements were made in three orthogonal directions on 70 vertebral bone cubes. Apparent density (rho) was determined, and microcomputed tomography was used to derive a range of microstructural parameters. Qualitatively different ultrasonic behavior was observed in the craniocaudal (CC) axis, in which two distinct waves propagated. In this direction, only attenuation correlated strongly with rho (r2 = 80%), whereas, in the anteroposterior (AP) and mediolateral (ML) axes, there were significant correlations between all ultrasonic parameters and rho (r2 = 57%-79%). Microstructural parameters were, in general, correlated with ultrasonic properties, but when adjusted for rho, few significant relationships remained and the additional variance explained by individual microstructural parameters was relatively small (< 25% for CC axis, < 3% for AP, 0% for ML). In stepwise regression analysis including rho and all of the microstructural parameters, rho remained the primary determinant of ultrasonic properties in the transverse axes: Combinations of structural parameters explained, at most, an additional of 6% of the variability in ultrasonic properties in the AP axis, but failed to contribute significantly in the ML axis. In the CC axis, structural parameters played a greater role, but the pattern of associations was complex and the predictive power of the models was generally much less than that for the transverse axes. These data indicate that the ability of ultrasound to reflect aspects of trabecular structure is strongly dependent on the direction in which ultrasonic measurements are made, and provide only qualified support for the hypothesis that ultrasound reflects cancellous bone structure independently of bone density.

Absorptiometry, Photon↗
PubMed1998

A strategy for enhancing the transcriptional activity of weak cell type-specific promoters.

Cell type- and tissue-specific promoters play an important role in the development of site-selective vectors for gene therapy. A large number of highly specific promoters has been described, but their applicability is often hampered by their inefficient transcriptional activity. In this study, we describe a new strategy for enhancing the activity of weak promoters without loss of specificity. The basic principle of this strategy is to establish a positive feedback loop which is initiated by transcription from a cell type-specific promoter. This was achieved by using a cell type-specific promoter to drive the simultaneous expression of the desired effector/reporter gene product and a strong artificial transcriptional activator which stimulates transcription through appropriate binding sites in the promoter. Using a VP16-LexA chimeric transcription factor, we show that this approach leads to a 14- to > 100-fold enhancement of both the endothelial cell-specific von Willebrand factor promoter and the gastrointestinal-specific sucrase-isomaltase promoter while maintaining approximately 30- to > 100-fold cell type specificity.

3T3 Cells↗
PubMed1998

Rationale for and efficacy of prolonged-interval treatment using liposome-encapsulated amikacin in experimental Mycobacterium avium infection.

The potential of liposome-encapsulated antibiotics for prolonging drug application intervals was investigated by using a murine model of chronic lethal Mycobacterium avium infection. Liposomal encapsulation of amikacin, but not of ciprofloxacin, resulted in high and sustained drug levels in infected tissues, exceeding the minimal inhibitory concentration for M. avium for at least 28 days. As a consequence, once-weekly and even once-monthly treatments with liposomal amikacin significantly reduced bacterial replication in infected tissues and extended the survival time of infected mice.

Amikacin↗
PubMed1998

Transformation of the ionic X-ray contrast agent diatrizoate and related triiodinated benzoates by Trametes versicolor.

Iodinated X-ray contrast agents are considered to be nondegradable by microorganisms. The decomposition of the ionic X-ray contrast agents Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoic acid) and Iodipamide (3,3'-adipoyl-diimino-di(2,4,6-triiodobenzoic acid) and related triiodinated benzoates (Acetrizoate [3-acetylamino-2,4, 6-triiodobenzoic acid] and Aminotrizoate [3-amino-2,4, 6-triiodobenzoic acid]) by Trametes versicolor has been investigated. The fungus was able to transform all tested triiodinated benzoates cometabolically. During transformation of these compounds, iodide was released, but deiodination was not complete. T. versicolor liberated traces of 14CO2 from uniformly ring-14C-labeled Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoate). Various extracellular metabolites were detected during transformation of the different substances. In the transformation of Diatrizoate, the three main metabolites were identified as 3,5-di(acetamido)-2, 6-diiodobenzoic acid, 3,5-di(acetamido)-2,4-diiodobenzoic acid, and 3,5-di(acetamido)-2-iodobenzoic acid, suggesting reductive deiodinations in steps as initial transformation steps.

Benzoates↗
PubMed1998

Pseudomonas sp. strain 273, an aerobic alpha, omega-dichloroalkaneDegrading bacterium.

A gram-negative, aerobic bacterium was isolated from soil; this bacterium grew in 50% (vol/vol) suspensions of 1,10-dichlorodecane (1,10-DCD) as the sole source of carbon and energy. Phenotypic and small-subunit ribosomal RNA characterizations identified the organism, designated strain 273, as a member of the genus Pseudomonas. After induction with 1,10-DCD, Pseudomonas sp. strain 273 released stoichiometric amounts of chloride from C5 to C12 alpha, omega-dichloroalkanes in the presence of oxygen. No dehalogenation occurred under anaerobic conditions. The best substrates for dehalogenation and growth were C9 to C12 chloroalkanes. The isolate also grew with nonhalogenated aliphatic compounds, and decane-grown cells dechlorinated 1,10-DCD without a lag phase. In addition, cells grown on decane dechlorinated 1,10-DCD in the presence of chloramphenicol, indicating that the 1,10-DCD-dechlorinating enzyme system was also induced by decane. Other known alkane-degrading Pseudomonas species did not grow with 1,10-DCD as a carbon source. Dechlorination of 1,10-DCD was demonstrated in cell extracts of Pseudomonas sp. strain 273. Cell-free activity was strictly oxygen dependent, and NADH stimulated dechlorination, whereas EDTA had an inhibitory effect.

Aerobiosis↗
PubMed1998

CIF150, a human cofactor for transcription factor IID-dependent initiator function.

The transcription factor IID (TFIID) complex is highly conserved between the Drosophila and mammalian systems. A mammalian homolog has been described for all the Drosophila TATA box-binding protein-associated factors (TAFs), with the exception of dTAF(II)150. We previously reported the identification of CIF, an essential cofactor for TFIID-dependent transcription from promoters containing initiator (Inr) elements. Here we describe the molecular cloning of CIF150, the human homolog of dTAF(II)150, and present biochemical evidence that this factor is involved in Inr activity. CIF150 is capable of mediating TFIID-dependent Inr activity in a complementation assay, and a protein fraction lacking Inr activity lacks detectable amounts of CIF150. Despite the striking similarity to dTAF(II)150, CIF150 does not appear to be associated with human TFIID. However, in vitro binding assays revealed a specific and direct interaction between CIF150 and hTAF(II)135. This interaction might be structurally important for the functional interaction between CIF150 and human TFIID, since CIF150 stabilizes TFIID binding to a core promoter.

Amino Acid Sequence↗
PubMed1998

Overexpression and structural characterization of the phage T4 protein DsbA.

The double strand binding protein A (DsbA) of bacteriophage T4 is one of several viral gene products participating in transcriptional regulation. These proteins interact or associate with the host RNA polymerase core enzyme, enabling the enzyme to successively initiate transcription at different classes of viral promoters: early, middle and late. This leads to a temporally controlled expression of the T4 gene products. The DsbA binding site overlaps the late promoter region, and DsbA binding seems to intensify transcription of late genes in vitro, possibly acting as an enhancer protein (Molecular Biology of Phage T4, Karam, 1994). To further investigate the function and structure of DsbA, we overexpressed the protein in E. coli and purified it to homogeneity. Physiological functionality of the recombinant protein was shown by gel retardation experiments and by circular dichroism (CD) spectroscopy. DsbA shows strong bands in the near UV-CD spectra. The far UV-CD spectroscopy analysis shows alpha-helices to be the main secondary structure elements. This is in agreement with secondary structure predictions. A possible helix-turn-helix motif in the center of the protein could be identified. Results from crosslinking and sedimentation analyses show that DsbA forms a dimer in solution. The thermal unfolding curve fits a dimer-two-state-folding-model, and the unfolding temperature was concentration dependent. Therefore, dimerization should supply the main portion of the free energy of stabilization of deltaG0 = 42 kJ/mol.

Binding Sites↗
PubMed1998

Micro-compression: a novel technique for the nondestructive assessment of local bone failure.

Many bones within the axial and appendicular skeleton are subjected to repetitive, cyclic loading during the course of ordinary daily activities. If this repetitive loading is of sufficient magnitude or duration, fatigue failure of the bone tissue may result. In clinical orthopedics, trabecular fatigue fractures are observed as compressive stress fractures in the proximal femur, vertebrae, calcaneus and tibia, and are often preceded by buckling and bending of microstructural elements. However, the relative importance of bone density and architecture in the etiology of these fractures is poorly understood. The aim of the study was to investigate failure mechanisms of 3D trabecular bone using micro-computed tomography (microCT). Because of its nondestructive nature, microCT represents an ideal approach for performing not only static measurements of bone architecture but also dynamic measurements of failure initiation and propagation as well as damage accumulation. For the purpose of the study, a novel micro-compression device was devised to measure loaded trabecular bone specimens directly in a micro-tomographic system. The measurement window in the device was made of a radiolucent, highly stiff plastic to enable X-rays to penetrate the material. The micro-compressor has an outer diameter of 19 mm and a total length of 65 mm. The internal load chamber fits wet or dry bone specimens with maximal diameters of 9 mm and maximal lengths of 22 mm. For the actual measurement, first, the unloaded bone is measured in the microCT. Second, a load-displacement curve is recorded where the load is measured with an integrated mini-button load cell and the displacement is computed directly from the microCT scout-view. For each load case, a 3D snap-shot of the structure under load is taken providing 34 microm nominal resolution. Initial measurements included specimens from bovine tibiae and whale spine to investigate the influence of the structure type on the failure mechanism. In a rod-like type of architecture as seen in the whale spine, structural failure was described by an initial buckling and bending of structural elements followed by a collapse of the overloaded trabeculae. In the more plate-like bovine tibial architecture, buckling and bending could not be observed. Failure rather seemed to occur instantaneously. In conclusion, micro-compression in combination with 3D microCT allows visualization of failure initiation and propagation and monitoring of damage accumulation in a nondestructive way. We expect these findings to improve our understanding of the relative importance of density, architecture and load in the etiology of spontaneous fractures of the hip and the spine. Eventually, this improved understanding may lead to more successful approaches to the prevention of age-related fractures.

Animals↗
PubMed1998

Should insulin therapy in type 2 diabetic patients be started on an out- or inpatient basis? Results of a prospective controlled trial using the same treatment and teaching programme in ambulatory care and a university hospital.

The aim of this study was to determine whether Type 2 diabetic patients should be hospitalised to start insulin therapy. The same structured diabetes treatment and teaching programme (DTTP) was used in outpatients in 10 private practices after postgraduate training of physicians and teaching staff as well as in the Diabetes Department of the University Hospital of Jena, Germany. Seventy-two consecutive Type 2 diabetic patients (ambulatory group) participated in the outpatient DTTP. After one year, 70 patients were re-evaluated and compared with 70 other patients (matched pairs) who were referred to the University Hospital of Jena to start insulin treatment and participated in the same programme during hospitalisation. Initially there were no significant differences between the groups for age, gender, HbA1c, body mass index (BMI), and the time since diagnosis of diabetes. HbA1c (mean normal value 5%) decreased in both groups within the 12 months of follow-up (ambulatory group from 10.3 +/- 2.2 to 8.1 +/- 1.7, p < 0.0001; inpatient group from 10.4 +/- 1.6 to 8.4 +/- 1.7, P = 0.0001). At follow-up there were no significant differences between the groups concerning insulin dosage, HbA1c, severe hypoglycaemia, BMI, and hospitalisation. In combination with a DTTP, the initiation of insulin therapy on an ambulatory basis was as safe and effective as in the inpatient programme. Cost-benefit analysis demonstrated substantial savings in direct costs in the ambulatory programme.

Aged↗