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Biomedical subjects

M Wagner

Publications and source records attributed to M Wagner.

At least 325 records · Page 18Linked to original sources
PubMed1998

Apoptosis caused by oxidized LDL is manganese superoxide dismutase and p53 dependent.

Oxidized low density lipoprotein (oxLDL) induces apoptosis in human macrophages (Mphi), a significant feature in atherogenesis. We found that induction of apoptosis in Mphi by oxLDL, C2-ceramide, tumor necrosis factor alpha (TNF-alpha), and hydrogen peroxide (H2O2) was associated with enhanced expression of manganese superoxide dismutase (MnSOD) and p53. Treatment of cells with p53 or MnSOD antisense oligonucleotides prior to stimulation with oxLDL, C2-ceramide, TNF-alpha, or H2O2 caused an inhibition of the expression of the respective protein together with a marked reduction of apoptosis. Exposure to N-acetylcysteine before treatment with oxLDL, C2-ceramide, TNF-alpha, or H2O2 reversed a decrease in cellular glutathione concentrations as well as the enhanced production of p53 and MnSOD mRNA and protein. In apoptotic macrophages of human atherosclerotic plaques, colocalization of MnSOD and p53 immunoreactivity was found. These results indicate that in oxLDL-induced apoptosis, a concomitant induction of p53 and MnSOD is critical, and suggest that it is at least in part due to an enhancement of the sphingomyelin/ceramide pathway.

Apoptosis↗
PubMed1998

Improved nuclear magnetic resonance microscopic visualization of joint cartilage using liposome entrapped contrast agents.

RATIONALE AND OBJECTIVES: After intraarticular application of gadolinium (Gd)-DTPA the visualization cartilage surface roughness is limited because of diffusion into the cartilage. To improve the sensitivity of magnetic resonance (MR) arthrography to diagnose cartilage surface abnormalities, the authors have tested liposome-entrapped contrast agents. METHODS: Using paramagnetic contrast agents (Gd-DTPA and manganese chloride) free and entrapped in liposomes, respectively, high resolution MR imaging investigations were performed at 7.1 tesla on intact pig temporomandibular and rabbit knee joints. RESULTS: After intraarticular injection of the liposome-entrapped contrast agents an excellent contrast between cartilage surface and joint space was achieved. Diffusion of the contrast agent into the cartilage layer was prevented and the visualization of the cartilage surface was improved markedly. Small mechanically and enzymatically induced cartilage lesions could be assessed reliably. CONCLUSIONS: Intraarticular injection of liposome-entrapped contrast agents can improve the potential of MR arthrography concerning the detection of early osteoarthritic cartilage changes.

Animals↗
PubMed1998

An improved boundary element method for realistic volume-conductor modeling.

An improved boundary element method (BEM) with a virtual triangle refinement using the vertex normals, an optimized auto solid angle approximation, and a weighted isolated problem approach is presented. The performance of this new approach is compared to analytically solvable spherical shell models and highly refined reference BEM models for tangentially and radially oriented dipoles at different eccentricities. The lead fields of several electroencephalography (EEG) and magnetoencephalography (MEG) setups are analyzed by singular-value decompositions for realistically shaped volume-conductor models. Dipole mislocalizations due to simplified volume-conductor models are investigated for EEG and MEG examinations for points on a three dimensional (3-D) grid with 10-mm spacing inside the conductor and all principal dipole orientations. The applicability of the BEM in view of the computational effort is tested with a standard workstation. Finally, an application of the new method to epileptic spike data is studied and the results are compared to the spherical-shells approximation.

Body Fluid Compartments↗
PubMed1998

Human melanoma cell lines show little relationship between expression of pigmentation genes and pigmentary behaviour in vitro.

Several laboratories are pursuing the question of whether the expression of pigment genes can be used as a useful marker for tumour progression. However, many melanoma tumours are amelanotic in vivo. The purpose of this study was to examine the relationship between the expression of tyrosinase-related genes [tyrosinase, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2)] and pigmentation of melanoma cells. Fourteen cutaneous melanoma cell lines were examined for visible pigment, melanin content, and dopa oxidase activity and findings were related to the previously determined expression of the three tyrosinase-related genes in these cells in culture. Four of the cell lines were also stimulated with alpha-MSH, isobutylmethylxanthine, and forskolin to examine the relationship between induced pigmentation and upregulation of pigmentation genes. There was no simple correlation between pigmentation gene expression and dopa oxidase activity or total melanin content of the 14 melanoma cell lines in culture. In the majority of cells, there was no appreciable pigment, whereas, in contrast, half of the cells showed significant dopa oxidase activity. Upregulation of dopa oxidase activity was achieved by alpha-MSH in two out of four cell lines examined in detail and with IBMX in three out of four of these cell lines. IBMX increased tyrosinase gene expression in all four cell lines; alpha-MSH was without effect; and TRP-1 and TRP-2 expression were largely unaffected by IBMX or alpha-MSH. Modest changes in morphology were noted in response to IBMX. Overall, however, human melanoma cell lines were, with two exceptions, amelanotic in culture despite the fact that 10 out of the 14 lines expressed tyrosinase-related genes. We conclude that measurable pigmentation is not a necessary consequence of the expression of pigmentation genes. An implication of this work is that amelanotic tumours in vivo may nevertheless be positive for tyrosinase-related genes.

Biomarkers, Tumor↗
PubMed1998

Automated confocal laser scanning microscopy and semiautomated image processing for analysis of biofilms.

The purpose of this study was to develop and apply a quantitative optical method suitable for routine measurements of biofilm structures under in situ conditions. A computer program was designed to perform automated investigations of biofilms by using image acquisition and image analysis techniques. To obtain a representative profile of a growing biofilm, a nondestructive procedure was created to study and quantify undisturbed microbial populations within the physical environment of a glass flow cell. Key components of the computer-controlled processing described in this paper are the on-line collection of confocal two-dimensional (2D) cross-sectional images from a preset 3D domain of interest followed by the off-line analysis of these 2D images. With the quantitative extraction of information contained in each image, a three-dimensional reconstruction of the principal biological events can be achieved. The program is convenient to handle and was generated to determine biovolumes and thus facilitate the examination of dynamic processes within biofilms. In the present study, Pseudomonas fluorescens or a green fluorescent protein-expressing Escherichia coli strain, EC12, was inoculated into glass flow cells and the respective monoculture biofilms were analyzed in three dimensions. In this paper we describe a method for the routine measurements of biofilms by using automated image acquisition and semiautomated image analysis.

Automation↗
PubMed1998

Combined molecular and conventional analyses of nitrifying bacterium diversity in activated sludge: Nitrosococcus mobilis and Nitrospira-like bacteria as dominant populations.

The ammonia-oxidizing and nitrite-oxidizing bacterial populations occurring in the nitrifying activated sludge of an industrial wastewater treatment plant receiving sewage with high ammonia concentrations were studied by use of a polyphasic approach. In situ hybridization with a set of hierarchical 16S rRNA-targeted probes for ammonia-oxidizing bacteria revealed the dominance of Nitrosococcus mobilis-like bacteria. The phylogenetic affiliation suggested by fluorescent in situ hybridization (FISH) was confirmed by isolation of N. mobilis as the numerically dominant ammonia oxidizer and subsequent comparative 16S rRNA gene (rDNA) sequence and DNA-DNA hybridization analyses. For molecular fine-scale analysis of the ammonia-oxidizing population, a partial stretch of the gene encoding the active-site polypeptide of ammonia monooxygenase (amoA) was amplified from total DNA extracted from ammonia oxidizer isolates and from activated sludge. However, comparative sequence analysis of 13 amoA clone sequences from activated sludge demonstrated that these sequences were highly similar to each other and to the corresponding amoA gene fragments of Nitrosomonas europaea Nm50 and the N. mobilis isolate. The unexpected high sequence similarity between the amoA gene fragments of the N. mobilis isolate and N. europaea indicates a possible lateral gene transfer event. Although a Nitrobacter strain was isolated, members of the nitrite-oxidizing genus Nitrobacter were not detectable in the activated sludge by in situ hybridization. Therefore, we used the rRNA approach to investigate the abundance of other well-known nitrite-oxidizing bacterial genera. Three different methods were used for DNA extraction from the activated sludge. For each DNA preparation, almost full-length genes encoding small-subunit rRNA were separately amplified and used to generate three 16S rDNA libraries. By comparative sequence analysis, 2 of 60 randomly selected clones could be assigned to the nitrite-oxidizing bacteria of the genus Nitrospira. Based on these clone sequences, a specific 16S rRNA-targeted probe was developed. FISH of the activated sludge with this probe demonstrated that Nitrospira-like bacteria were present in significant numbers (9% of the total bacterial counts) and frequently occurred in coaggregated microcolonies with N. mobilis.

Ammonia↗
PubMed1998

Identification and activities in situ of Nitrosospira and Nitrospira spp. as dominant populations in a nitrifying fluidized bed reactor.

Bacterial aggregates from a chemolithoautotrophic, nitrifying fluidized bed reactor were investigated with microsensors and rRNA-based molecular techniques. The microprofiles of O2, NH4+, NO2-, and NO3- demonstrated the occurrence of complete nitrification in the outer 125 microgram of the aggregates. The ammonia oxidizers were identified as members of the Nitrosospira group by fluorescence in situ hybridization (FISH). No ammonia- or nitrite-oxidizing bacteria of the genus Nitrosomonas or Nitrobacter, respectively, could be detected by FISH. To identify the nitrite oxidizers, a 16S ribosomal DNA clone library was constructed and screened by denaturing gradient gel electrophoresis and selected clones were sequenced. The organisms represented by these sequences formed two phylogenetically distinct clusters affiliated with the nitrite oxidizer Nitrospira moscoviensis. 16S rRNA-targeted oligonucleotide probes were designed for in situ detection of these organisms. FISH analysis showed that the dominant populations of Nitrospira spp. and Nitrosospira spp. formed separate, dense clusters which were in contact with each other and occurred throughout the aggregate. A second, smaller, morphologically and genetically different population of Nitrospira spp. was restricted to the outer nitrifying zones.

Ammonia↗
PubMed1998

Phylogeny of dissimilatory sulfite reductases supports an early origin of sulfate respiration.

Microorganisms that use sulfate as a terminal electron acceptor for anaerobic respiration play a central role in the global sulfur cycle. Here, we report the results of comparative sequence analysis of dissimilatory sulfite reductase (DSR) genes from closely and distantly related sulfate-reducing organisms to infer the evolutionary history of DSR. A 1.9-kb DNA region encoding most of the alpha and beta subunits of DSR could be recovered only from organisms capable of dissimilatory sulfate reduction with a PCR primer set targeting highly conserved regions in these genes. All DNA sequences obtained were highly similar to one another (49 to 89% identity), and their inferred evolutionary relationships were nearly identical to those inferred on the basis of 16S rRNA. We conclude that the high similarity of bacterial and archaeal DSRs reflects their common origin from a conserved DSR. This ancestral DSR was either present before the split between the domains Bacteria, Archaea, and Eucarya or laterally transferred between Bacteria and Archaea soon after domain divergence. Thus, if the physiological role of the DSR was constant over time, then early ancestors of Bacteria and Archaea already possessed a key enzyme of sulfate and sulfite respiration.

Archaeoglobus fulgidus↗
PubMed1998

Transcriptional regulation of the SMK1 mitogen-activated protein kinase gene during meiotic development in Saccharomyces cerevisiae.

Meiotic development (sporulation) in Saccharomyces cerevisiae is characterized by an ordered pattern of gene expression, with sporulation-specific genes classified as early, middle, mid-late, or late depending on when they are expressed. SMK1 encodes a mitogen-activated protein kinase required for spore morphogenesis that is expressed as a middle sporulation-specific gene. Here, we identify the cis-acting DNA elements that regulate SMK1 transcription and characterize the phenotypes of mutants with altered expression patterns. The SMK1 promoter contains an upstream activating sequence (UASS) that specifically interacts with the transcriptional activator Abf1p. The Abf1p-binding sites from the early HOP1 and the middle SMK1 promoters are functionally interchangeable, demonstrating that these elements do not play a direct role in their differential transcriptional timing. Timing of SMK1 expression is determined by another cis-acting DNA sequence termed MSE (for middle sporulation element). The MSE is required not only for activation of SMK1 transcription during middle sporulation but also for its repression during vegetative growth and early meiosis. In addition, the SMK1 MSE can repress vegetative expression in the context of the HOP1 promoter and convert HOP1 from an early to a middle gene. SMK1 function is not contingent on its tight transcriptional regulation as a middle sporulation-specific gene. However, promoter mutants with different quantitative defects in SMK1 transcript levels during middle sporulation show distinct sporulation phenotypes.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

Rat renal expression of mRNA coding for aldose reductase and sorbitol dehydrogenase and its osmotic regulation in inner medullary collecting duct cells.

Sorbitol plays an important role in the osmoregulation of several renal cell types, especially the inner medullary collecting duct (IMCD) cells. Very little information is available concerning the expression of the enzymes of sorbitol metabolism (aldose reductase (AR) and sorbitol dehydrogenase (SDH)) on the RNA level under different osmotic conditions. We employed a RT-PCR-based strategy to investigate the regulation of mRNA coding for AR and SDH. For AR two primers (derived from the sequence of the rat eye lens) were chosen which amplify a 668-bp product. For SDH (considering the sequence of rat liver) three primers were chosen, amplifying a 367- and a 1, 068-bp fragment. Digestion with restriction enzymes and sequencing of the products clearly indicate that the specific mRNA of AR and SDH was amplified. By relative quantitative determination of the amplification products a more than 4-fold increase in mRNA for AR in IMCD cells was observed within 24 h after increasing the extracellular osmolarity from 600 to 900 mosm/l. Decreasing the osmolarity from 600 to 300 mosm/l resulted in a reduction in the mRNA level by 70%. The complete adaptation of the AR activity needed 3 (increasing osmolarity) and 6 days (decreasing osmolarity). Osmotically induced alterations in the levels of mRNA coding for SDH could not be observed. These results suggest that the adaptation of sorbitol synthesis occurs by a rapid regulation of transcription or stability of specific mRNA. For a complete synthesis or degradation of AR 3-6 days are necessary. Thus sorbitol synthesis in IMCD is more rapidly adapted to increasing osmolarities than to decreasing osmolarities.

Aldehyde Reductase↗
PubMed1998

Current trends in biocompatibility testing.

Biocompatibility remains the central theme for biomaterials applications in medicine. It is generally accepted that this term means not only absence of a cytotoxic effect but also positive effects in the sense of biofunctionality, i.e. promotion of biological processes which further the intended aim of the application of a biomaterial. The national and international standards for testing regimes represent a lowest common denominator for such applications and do not necessarily ensure that optimal function will be achieved. The authors' thesis is that biocompatibility testing has scope for extensive development with respect to biofunctionality. The present paper reviews current trends in the in vitro aspects of biocompatibility testing. As well as a critical appraisal of the recent literature, future trends are also stressed, which the authors regard as essential for a meaningful integration of a modern biological approach into new developments in the material sciences. These include the application of modern techniques of cell and molecular biology, the concepts of tissue remodelling, hybrid organ development and encapsulated cell technology.

Animals↗
PubMed1998

Root surface characteristics of primary teeth from children with prepubertal periodontitis.

This study describes the histologic characteristics of root surfaces of primary teeth from children with prepubertal periodontitis (PP). Fifteen primary teeth from 4 children with PP, and 2 control primary teeth from 2 healthy children were examined. Light microscopy revealed normal root surfaces in the control teeth. In contrast, the PP specimens revealed bacteria inside dentin tubules or covering cementum, a cuticle, or resorbed dentin; normal, wider than normal, or hypoplastic cementum; resorption lacunae with various depths; aplastic root resorption; alternate resorption and repair; and active repair. No cementoclasts were found in the resorption lacunae. Scanning electron microscopy revealed intrabony and suprabony root areas, and a "plaque free zone" (PFZ). Colonies of filaments were evident at the cemento-enamel junction (CEJ). The suprabony root surfaces had resorption lacunae, isolated short rods, calculus, colonies of filaments, or colonies composed by an heterogeneous bacterial population. The coronal boundary of the PFZ was the border of a sheet-like structure, which included isolated rods or filaments. At the PFZ, isolated filaments and rods, and a fibril matrix were evident. The apical boundary of the PFZ consisted of bundles of soft tissue remnants or the insertion of the periodontal fibers. The intrabony surfaces were mostly covered by soft tissue, which included isolated filaments and short rods. Resorption lacunae with or without soft tissue were also evident in this area. Crystals of calcium oxalate dihydrate and erythrocytes in distinct forms were found at various root areas. The present findings are different from those previously reported for hypophosphatasia specimens.

Aggressive Periodontitis↗
PubMed1998

[Pilot study of effectiveness of electrotherapy in the experimental liver metastasis model].

The aim of the present was to assess the effectiveness of low level direct current therapy in liver metastases and the influence of polarity (anode or cathode in the center of the tumor) or current dose (60 or 80 C/cm3). Colorectal metastases were established in 25 BD IX rats by injection of DHD/K12 colon cancer cells under the liver capsule. After 3 weeks the tumors were treated by low level direct current therapy (applied with five platinum electrodes). Histological examination of the removed livers on postoperative day 7 revealed significant destruction of the metastases with localized necroses. The best treatment results were obtained in the group with an anode in the center and a current dose of 80 C/cm3. We conclude that low level direct current therapy may offer an alternative minimal invasive method in the treatment of liver metastases.

Animals↗
PubMed1998

[Treatment of fingertip defect injuries with a semi-occlusive dressing].

In the treatment of substance loss of fingertips it is crucial to maintain functional length and to restore adequate sensibility. By treating those injuries with a semiocclusive dressing according to Mennen and Wiese (1993), we were able to achieve both goals with excellent results, avoiding the necessity of local or regional flaps as well as shortening of bone to achieve primary closure. 82 patients with 85 injured digits were treated either conventionally (primary closure with or without shortening of bone, vaseline gauze dressings: 31 digits) or with semiocclusive dressings (54 digits). 42 digits of the latter group with complete protocols were evaluated at the end of treatment. 26 digits with defects of skin and subcutaneous tissue of less than 1 cm2 to more than 2 cm2 necessitated an average of 18 days until complete healing (minimum 6, maximum 46 days). Eight digits with loss of skin, subcutaneous tissues and nailbed healed within 10 to 32 days (average 22 days) and eight digits in which defects included bone loss averaged 49 days for complete healing (37 to 64 days). No complications, especially no infections have been observed. All healed finger-tips were well padded, painless, many without visible scar and with static two-point discrimination between 2 and 8 mm.

Adolescent↗