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Biomedical subjects

R Schulze

Publications and source records attributed to R Schulze.

At least 19 recordsLinked to original sources
PubMed2005

Potential analytical applications of gated artificial ion channels.

Biosensors based on natural ion channels combine a biological recognition mechanism with a physical transduction technique in a very selective and sensitive manner. This kind of molecular sensor will contribute to drug screening and environmental screening. Key information about channel gating, ion transport, and molecular mechanism is provided by the patch-clamp technique, commonly used for electrophysiological analysis. Here we report the synthesis of light-gated artificial ion channels, necessary constituents for construction of biosensors based on natural ion channels. The artificial gated ion channels described here are based on calix[4]resorcinarene. Opening and closing of the artificial ion channel is achieved by azo groups, which work like a lid. Azo groups alter their conformation on irradiation with light, and are chemically quite stable. Addition of a gate function will enhance the potential of synthetic channels to be used in sensors as molecular switches.

Azo Compounds↗
PubMed2001

Analysis of 1202 orthopantograms to evaluate the potential of forensic age determination based on third molar developmental stages.

A total of 1202 orthopantograms of young dental patients were analyzed to assess the correlation of third molar root development with chronological age. The investigated patients were treated at a university dental clinic on an outpatient basis, included a variety of demographic characteristics (600 males and 602 females, 28% of other than central European background), and were 15-24 years old when the radiographs were obtained. Radiographs in which more than one third molar were either missing due to agenesia or extraction, or not evaluable because of deep destruction or marked tilting, were not included in the analysis. Our findings show that the growth patterns of third molars, based on seven defined stages of root development, did correlate with chronological age; age estimation when applied to a specific individual would involve a margin of error of +/- 2-4 years. There were no significant differences between the left and right jaw segments, but the stage of root development was generally more advanced in the upper than in the lower third molars. Root development was also more advanced among boys than among girls of the same age. There were no apparent differences in growth patterns based on national/ethnic background. While only 2.5% of 18-year-olds revealed fully developed third molars in all four quadrants, this percentage leaped to 38.4% among the 21-year-olds. To summarize, while the developmental stage of third molars is not per se a highly useful indicator of chronological age in juveniles and young adults, it is nevertheless a valuable supplementary parameter given the scarcity of other available age indicators.

Adolescent↗
PubMed2001

Authorship.

Explore the source record for details and available documents.

Authorship↗
PubMed2000

[Effect of positioning errors on magnification factors in the mandible in digital panorama imaging].

Magnification factors (VF) in relation to various head positions were evaluated for a digital panoramic radiography machine (Orthophos DS, Sirona) by means of a dry skull phantom. Six metallic objects were attached to the facial layer of the mandible. A set of 170 digital radiographs (program 1) was produced, with defined positioning errors within the vertical and horizontal plane. Repeated digital measurements of the object images were performed by one reader, applying the mouse-driven measurement tool integrated in the proprietary software. In addition, the central layer of the radiographic device was experimentally determined and its location compared to that of the accurately positioned dry mandible. All objects were located on the outside of the central layer of minimum distortion and therefore placed towards the sensor. One- and two-way analysis of variance was applied for the statistical evaluation of the data, with VF as dependent variable and the positions as factors, respectively. Vertical inclinations of the skull affected horizontal VF only in the premolar region (p = 0.0069). However, when the skull was rotated within the horizontal plane, VF was significantly influenced in all anatomical regions of the mandible (p = 0.0001). This was particularly obvious in the premolar region, with a maximum variation of 10.3%. Fluctuations of VF were more pronounced in the premolar region than at the mandibular angle. We conclude from this study that, as expected, digital panoramic radiographs exhibit identical distortion effects as compared to conventional panoramic x-rays. Exact quantification of regional magnification requires (spherical) reference objects with known dimensions. Horizontal magnification is quite unreliable and far less reproducible than vertical magnification. Whenever several panoramic radiographs of one patient are to be compared quantitatively, accurate positioning of the patients' head is a necessary prerequisite.

Artifacts↗
PubMed2000

Precision and accuracy of measurements in digital panoramic radiography.

OBJECTIVES: To evaluate the precision and accuracy of digital measurements in digital panoramic radiography. METHODS: A series of 70 digital panoramic radiographs were obtained of a dry skull in seven different positions with metallic pins and spheres fixed to the mandible. Three replicate measurements were performed with the mouse-driven cursor by one reader at 1:1 and 2:1 magnification. Precision was assessed with the reliability index (R) and Malony/Rastogi test and the effect of magnification on accuracy by paired Wilcoxon test. RESULTS: Vertical measurements were less reproducible than horizontal measurements. There were significant differences in assessments between images at 1:1 and 2:1 magnification (P < 0.05). The maximum variation in mean difference was 0.4% of actual object length for pins and 1.2% for spheres. The difference did not exceed 0.1 mm. R was lower for 2:1 magnification and consistently lower for spheres compared with pins. CONCLUSION: The most reliable measurements were obtained of linear objects in the horizontal plane. Digital measurements are sufficiently accurate for clinical use.

Data Display↗
PubMed2000

A new method for the radiological investigation of residual ridge resorption in the maxilla.

OBJECTIVES: To develop a new method for assessing residual ridge resorption in the edentulous maxilla. METHODS: Defined experimental and reference areas in the maxilla were drawn on transparent film laid over a panoramic radiograph and digitized. Bone areas were measured with an integrated planimetry program and expressed as a ratio R. The effect of positioning errors on reliability of the method was investigated on dry skulls. The correlation between the change in ratio and actual bone loss was examined by progressively reducing the height of an artificial residual ridge on one skull. RESULTS: The coefficient of variation for the absolute ratio in different head positions was < 0.05 and its correlation coefficient of the change in R and the degree of resorption was r2 > or = 98.3%, P = 0.0001. CONCLUSIONS: Comparison of the experimental area with the reference area on serial panoramic radiographs appears suitable for the assessment of residual resorption in the maxilla.

Bone Resorption↗
PubMed2000

Cytotoxicity of root canal filling materials to three different human cell lines.

The aim of this study was to investigate the biological compatibility of five root canal sealers (Sealapex, Endion, Super-EBA, Ketac-Endo, and AH Plus) and regular and calcium hydroxide-based gutta-percha in three different human cell lines. Cultures without root canal sealers were used as controls. Cell growth, cell morphology, cell viability, protein content of the cells, and prostaglandin E2 (PGE2) release were used as parameters to determine the cytotoxicity of the materials. The protein content of the three cell lines--nasal fibroblasts, gingival fibroblasts, and epithelial tumor cells--was significantly reduced (p < or = 0.001) by all materials tested. Determinations of PGE2 release showed significant material specific differences. No significant increased PGE2 release values were found with Sealapex, Endion, and Super-EBA. On the contrary significantly increased PGE2 levels were measured with Ketac Endo, AH Plus, regular and calcium hydroxide-based gutta-percha points (p < or = 0.001).

Biocompatible Materials↗
PubMed2000

Identification and characterization of ecologically significant prokaryotes in the sediment of freshwater lakes: molecular and cultivation studies.

The aim of this review is to interpret recent studies in which molecular methods were used to identify and characterize prokaryotes in lake sediments and related habitats. In the first part studies based on the phylogenetic diversity of prokaryotes found in lacustrine habitats are summarized. The application of various cultivation-independent methods for the characterization of distinct groups of sediment bacteria is exemplified with morphologically conspicuous, colorless sulfur bacteria in the second part of this review. Finally, traditional and recently developed methods are described which could be used for linking the function of microbial populations with their identification. The potential of these approaches for the study of lake sediments is discussed in order to give a perspective for future studies in this habitat.

Bacteria↗
PubMed1999

Stent or angioplasty after recanalization of chronic coronary occlusions? (The SARECCO Trial).

This study tests whether stent implantation without anticoagulation after catheter recanalization of coronary occlusions can improve outcome compared with balloon angioplasty alone. One hundred ten patients were randomly assigned to angioplasty alone (no stent group) or stent implantation (stent group) after successful recanalization and balloon angioplasty. The type of stent and angioplasty technique utilized were decided by the operator. The acute procedural success in both groups was 100%. The acute minimal lumen diameter (MLD) was 1.85 +/- 0.44 mm in the no stent group versus 2.54 +/- 0.53 mm in the stent group (p <0.01). The diameter stenosis was 21 +/- 13% versus 3 +/- 14% (p <0.01). This was achieved not only by the stent implantation itself but primarily by a larger maximum balloon diameter in the stent group after stent implantation (3.32 +/- 0.55 mm vs 2.86 +/- 0.4 mm, p <0.05). After 4 months, the MLD was 1.15 +/- 0.73 mm in the no stent group versus 1.81 +/- 0.9 mm in the stent group (p <0.01). The diameter stenosis was 56 +/- 29% versus 34 +/- 28% (p <0.01). After 2 years, event-free survival was 26% in the no stent group and 52% in the stent group (p <0.05). Thus, acute and long-term procedural and angiographic success of stent implantation without anticoagulation after recanalization of total coronary occlusions is superior to that of balloon angioplasty alone. This beneficial effect is mainly the result of the larger balloon diameters, which may be used after stent implantation.

Angioplasty, Balloon↗
PubMed1999

Influence of resin-based restoration materials on cytotoxicity in gingival fibroblasts.

Tooth-colored resin-based restoration materials have gained enormous significance in recent decades. Since the composites presently available still evidence various weaknesses, intensive research continues concerning them. In this study we tested the biocompatibility of six resin-based materials (Charisma, Solitaire, Definite, Tetric ceram, Ariston pHc and Compoglass) by means of cultured human gingival fibroblasts. Over a period of 9 days the cured resin-based materials were incubated with the fibroblasts. Cell growth, cell viability, and protein content was measured. The release of prostaglandin (PGE subset2) was also determined. There was a reduction of cell functions, related to the different resin-based materials. Protein content of the fibroblasts was significantly reduced (Kruskal Wallis test; p = 0.0001), depending on the material tested. Definite induced only minimal irritation, and there was correspondingly little contrast to the protein content of the controls. Solitaire induced the highest levels of irritation and the greatest reduction in protein content. Lactate production of fibroblasts also showed some significant reduction in contact with particular materials (p = 0.005). There were only small differences among the tested materials as concerns measured PGE subset2 release of the fibroblasts. The data suggest that the methods here employed may be quite useful in testing the cytotoxic potential of newly developed resin-based materials

Cell Division↗
PubMed1999

Genotypic diversity of Acidovorax strains isolated from activated sludge and description of Acidovorax defluvii sp. nov.

Fluorescence in situ hybridization of activated sludge samples from a municipal wastewater treatment plant using oligonucleotide probes specific for Acidovorax demonstrated that these bacteria are highly abundant in this environment. For the targeted cultivation of representatives belonging to this genus, isolates grown on agar plates after serial dilution were screened by whole-cell hybridization with specific probes. The obtained strains clustered in two phylogenetic groups as determined by 16S rRNA gene sequence analyses. The isolates of one cluster were phylogenetically and genotypically closely related to A. delafieldii. In contrast, the strains of the other cluster were genotypically and phenotypically distinct from the hitherto known Acidovorax species. Therefore, a new species, Acidovorax defluvii sp. nov., was proposed for these strains. The main characteristics of the newly defined species are as follows: Gram-negative, motile or non-motile rods with rounded ends, often with large polyhydroxybutyrate granules. In broth cultures flocs are formed. Test for cytochrome oxidase is positive with all strains. The majority of strains is catalase positive and reduces nitrate. All strains are metabolically inactive against most carbohydrates and organic acids. Fatty acid patterns are typical for the genus Acidovorax. The guanine-plus-cytosine content of DNAs varies between 62 and 64 mol%. The type strain of A. defluvii is BSB411T (DSM 12644). A new 16S rRNA-targeted oligonucleotide probe reacting by in situ hybridization with all known Acidovorax species, including A. defluvii sp. nov., was designed.

Base Sequence↗
PubMed1997

Detection and in situ identification of representatives of a widely distributed new bacterial phylum.

16S rRNA gene libraries were prepared by polymerase chain reaction amplification and cloning from soil samples taken periodically from a field with genetically modified plants. Sequence analyses of the cloned rDNAs indicated that 140 of them clustered apart from known bacterial phyla. Based on 31 full sequences a new phylum could be defined. It includes Holophaga foetida, 'Geothrix fermentans' and Acidobacterium capsulatum as the only cultured species so far. Therefore, this line of descent was named the Holophagal Acidobacterium phylum. About 50 published partial sequences of cloned rDNAs retrieved from soil, freshwater sediments or activated sludge from different continents indicate the occurrence of further representatives of this phylum. Two specific hybridization probes were constructed for members of one of four subclusters. A careful data analysis revealed the importance and problems of identifying and dealing with artefacts such as chimeric structure when defining new phylogenetic groups based mainly upon cloned amplified rDNAs. For the first time, the presence of bacterial cells representing this group could be shown in soil, sediment, activated sludge and lake snow by in situ hybridization.

Bacteria↗
PubMed1997

Dynamic compartmentation of vacuolar amino acids in Penicillium cyclopium. Cytosolic adenylates act as a control signal for efflux into the cytosol.

The regulation of amino acid transport from the vacuolar reservoir into the cytoplasm has been studied in hyphal cells of Penicillium cyclopium. To avoid artifacts caused by the isolation of vacuoles, efflux was examined "in situ," i.e. in cells whose plasma membranes were permeabilized for micromolecules by a treatment with nystatin. The ATP-dependent proton gradient and amino acid transport activities at the vacuolar membrane remained intact under these conditions. Accumulation of amino acids in the vacuole proved to be the result of a dynamic equilibrium of active, ATP-dependent uptake and energy-independent efflux. The latter was strongly accelerated after the vacuolar amino acid content had surpassed a threshold level. Efflux of vacuolar amino acids was specifically controlled by extravacuolar adenylates: ATP, 5'-adenylyl imidodiphosphate (an ATPase-resistant ATP-analogue), ADP, or AMP caused a strong inhibition in the concentration range around 200 micromol/liter, whereas both lower and higher concentrations allowed significant efflux rates. Estimates of the cytosolic adenylates (which consisted mainly of ATP) were close to 2 mmol/liter in glucose-metabolizing cells, which concentration allowed maximum rates of both vacuolar uptake and efflux. During 24 h of carbon and nitrogen starvation, the adenylate level decreased toward the efflux-inhibiting region around 200 micromol/liter, whereas 3-4 d of carbon and nitrogen starvation caused a further decline of the adenylate content, leading again to efflux-permitting concentrations. Thus, the cytosolic adenylate pool appears to effectively control the availability of vacuolar amino acids for the cellular metabolism.

Adenine Nucleotides↗
PubMed1997

Necrotizing skin lesions induced by low-molecular-weight heparin after total knee arthroplasty.

We report the unusual complication of focal necrotizing skin lesions accompanied by moderate thrombocytopenia in a female patient undergoing thromboprophylaxis with low-molecular-weight heparin after total knee arthroplasty. Heparin-induced thrombocytopenia was suspected and confirmed using the heparin-induced platelet activation assay. The skin lesions improved gradually after the discontinuation of heparin application. In addition to the description of this exceptionally rare adverse effect of low-molecular-weight heparin, a brief discussion of previously reported cases is provided.

Aged↗
PubMed1997

Tumor cell contamination of peripheral blood stem cell transplants and bone marrow in high-risk breast cancer patients.

Twenty-one high-risk patients with primary stage II/III breast cancer were treated with high-dose chemotherapy comprising etoposide, ifosfamide, carboplatin and epirubicin (VIC-E). Tumor cells of epithelial origin were analyzed using the monoclonal antibodies CK2 (IgG1) and A45-B/B3 (IgG1) against cytokeratin (CK) components in bone marrow (BM) aspirates prior to chemotherapy, and in peripheral blood stem cell transplants (PBSCT). They were separated after the first (21/21 patients) and the second cycle (16/21 patients) of induction chemotherapy with VIP-E (etoposide, ifosfamide, cisplatin, epirubicin). Preliminary results showed CK positive tumor cells in 40% (14/35) of the analyzed transplants. In 7/12 (58.3%) patients, CK positive tumor cells were detectable in BM prior to treatment. Sixteen patients were separated after the 1st and 2nd cycle of VIP-E. PBSCT of 14/16 patients were assessable for presence of CK positive tumor cells. Our preliminary results demonstrate a lower tumor cell contamination of PBSCT separated after the 2nd cycle of induction therapy (14.3%) compared to contamination after the first induction therapy (64.3%). To date, 4/21 patients have experienced a relapse, and three of these patients had tumor cell positive transplants. Due to the small patient number only a trend towards a superior relapse-free survival in the patient group with CK negative transplants can be shown by Kaplan-Meier analysis.

Adult↗
PubMed1997

Transcatheter closure of patent ductus arteriosus with the Rashkind occluder. Acute results and angiographic follow-up in adults.

We performed catheter closure of a patent ductus arteriosus with a Rashkind occluder in 51 adult patients (aged 14 to 76 years). The diameter of the ductus ranged from 2 to 13 mm (mean 4.5 +/- 2.0 mm), QP:QS from 1.0 to 2.6 (mean 1.6 +/- 0.3). The procedure was successful in 50/51 patients, in one of them at a second attempt. In one patient, the ductus could not be closed even with additional occluders. This patient was sent for surgery. In two patients with a large ductus, two Rashkind umbrellas were implanted simultaneously. Immediately after ductus closure, there was a residual shunt in 40/50 patients decreasing to 26/50 after 20 min. Two of the patients with a residual shunt suffered from haemolysis. In 16 patients, the residual shunt disappeared spontaneously within some months. In 15 patients, additional occluders (a second occluder in 12, a third occluder in one, and a fourth and fifth occluder in another) were implanted during the initial procedure or during follow-up. All patients were followed until angiography proved complete closure of the ductus. At the time of the last follow-up angiogram, the ductus was occluded in 49/50 patients; one patient refused a follow-up angiogram. Ductus occlusion with the Rashkind umbrella can be considered a technique with a high success rate and low rate of complications in adults. However, a residual shunt is not uncommon. Additional occluders have to be implanted in many patients.

Adolescent↗
PubMed1996

Recanalization of chronic coronary occlusions using a laser wire.

Between August, 1993-December, 1994, recanalization of a chronically occluded coronary artery was attempted in 412 patients, with an overall success rate of 77%. The main reason for failure was subintimal tracking of the guide wire. However, in 13 patients, advancing the guide wire was not possible either subintimally or in the former true lumen. In 8 of these 13 patients with failed conventional recanalization, a second attempt was made using a 0.018" laser wire. The suspected occlusion duration was 6 wk-6 yr, and the occlusion length 6-21 mm. Successful crossing of the occlusion was achieved in 7 of 8 patients. One patient experienced pericardial hematoma without severe clinical consequences. Adjunctive conventional laser angioplasty and/or balloon dilatation led to a residual stenosis of < 50% in 7 patients. The laser wire technique may become an important new method for recanalizing chronic total coronary occlusions in selected patients.

Angioplasty, Balloon, Coronary↗