Biomedical subjects

U Meyer

Publications and source records attributed to U Meyer.

At least 55 records · Page 3Linked to original sources

PubMed2002

Anaerobic digestion of alcohol sulfate (anionic surfactant) rich wastewater--batch experiments. Part II: influence of the hydrophobic chain length.

High-strength wastewater of some industries contains high concentrations of surfactants and readily biodegradable compounds like starch and other carbohydrates. Wastewater of this type is found in the textile wet-processing industry (e.g., cotton desizing). The anaerobic degradation process in such wastewater is inhibited due to the high surfactant content. Alcohol sulfate (AS) of increasing hydrophobic chain length (C8 to C18, surfactant) and soluble starch (size) were used as model compounds in a series of batch experiments with high loadings of the biomass (65 g AS/kg cell dry weight; 910 g starch/kg cell dry weight). The strongest inhibition of the hydrolysis, acidogenesis and acetogenesis was found in reactors containing medium chain ASs like dodecyl sulfate. Starch hydrolyzation rates decreased by nearly 90% in the presence of dodecyl sulfate. Decyl sulfate caused the strongest inhibition of the methanogenesis and a decrease of the methane evolution by 75% within 87 days experimental time. It was found that short as well as long chain ASs caused only minor inhibition phenomena. The presented data can be used as a basis for the selection of suitable surfactants that do not (or not seriously) inhibit the anaerobic digestion of industrial effluents.

Alcohols↗

PubMed2002

First experience with a public domain computer-aided surgical system.

The outcome of complex craniofacial operations is critically dependent on careful and accurate preoperative planning. Recent advances in computer technology enable the surgeon to do surgical simulations directly on to a computer terminal. We describe the clinical application of a public domain-based computer-aided system in craniofacial surgery. Operation planning was based on clinical investigations and radiological images, with particular use of a virtual three-dimensional surgical simulation. Three patients with complex craniofacial malformations were admitted for orbital correction. Surgical simulation defined numerically the extent of bone movements and the extent of resection areas. Operations were guided by the virtual planning. The outcome was compared with the planning to assess the accuracy of the operative correction. Our first experience confirms that computer-assisted simulation is a reliable and useful tool that improves surgical planning and helps to evaluate the surgical outcome.

Adult↗

PubMed2002

Effects of Fusarium toxin contaminated wheat and of a detoxifying agent on performance of growing bulls, on nutrient digestibility in wethers and on the carry over of zearalenone.

Experiments were carried out to examine the effects of a Fusarium contaminated wheat (10 mg deoxynivalenol and 0.76 mg zearalenone, ZON, per kg dry matter) and of a detoxifying agent (Mycofix Plus, Biomin GmbH, Herzogenburg, Austria) on the growing performance of bulls, carry-over of ZON and its metabolites into body fluids and tissues, and on nutrient digestibility in wethers. The experiments were designed according to a complete two by two factorial approach which meant that both the uncontaminated control wheat and the Fusarium toxin contaminated wheat were tested both in the absence and presence of Mycofix Plus. The growing experiment with bulls (n = 14 per treatment) covered the live weight range between 244 kg and 460 kg. The respective wheat batches were included in the concentrate portion at 65%. Concentrates were fed according to plan whereas maize silage was offered for ad libitum consumption. Daily dry matter intake and live weight gain [kg per animal and day] were 7.40, 7.52, 7.51 and 7.49 and 1.367, 1.296, 1.380 and 1.307 for bulls fed the unsupplemented control wheat, the supplemented control wheat, the unsupplemented and Fusarium toxin contaminated wheat and the supplemented Fusarium toxin contaminated wheat, respectively. ZON and its metabolites were not detected in edible tissues. The most striking effects of feeding the Fusarium toxin contaminated wheat on carcass characteristics were a reduced dressing percentage, an increased weight of the emptied gastro-intestinal tract and a reduced weight of the testicles. No effect of the detoxifying agent was seen for these parameters whereas heart weight increased independently of Fusarium toxin contamination of the concentrates. Nutrient digestibility of the two wheat batches, unsupplemented or supplemented with Mycofix Plus was evaluated according to the difference method using wethers. Presence of Fusarium toxins in wheat did not influence its feeding value. The effects of the addition of the detoxifying agent were mycotoxin unspecific and resulted in an increase in apparent digestibility of crude protein and a decrease in crude fiber digestibility. It is concluded that feeding of Fusarium toxin contaminated wheat did not adversely affect performance of growing bulls (approximately 2.2 mg DON and 0.1 mg ZON per kg complete ration at a reference dry matter content of 88%) or nutrient digestibility in wethers. The effects of the detoxifying agent Mycofix Plus on growing performance and on nutrient digestibility were rather Fusarium toxin unspecific. The slightly negative effects on growing performance needs to be examined further.

Animal Feed↗

PubMed2002

From khellin to sodium cromoglycate--a tribute to the work of Dr. R. E. C. Altounyan (1922-1987).

Sodium cromoglycate, which was launched in 1968 by the British company Fisons for the treatment of allergies and asthma, was an absolute novelty in chemical, pharmacological as well as therapeutic respects. The khellin derivative meanwhile did not owe its discovery to the usual strategies for finding drugs. On the contrary, the protective effect of the substance was discovered in a self trial through systematic antigen-induced provocation tests of the medicinal doctor and allergic Roger Ernest Collingwood Altounyan (1922-1987). The only subsequently formed hypothesis of a mast cell stabilising effect of Sodium cromoglcycate did not prove to be valid for the search for similar or more effective substances. A further development of this drug class could not take place because of the lack of suitable pharmacological models.

Anti-Asthmatic Agents↗

PubMed2002

On-line titration of non-ionic surfactants in wastewater treatment plants using a specific electrode.

Textile finishing industry wastewater often contains high concentrations of surfactants. Non-ionic surfactants like alcohol ethoxylates are among the most used surfactants and are discharged from batch-processes in widely varying concentrations. The anaerobic biomass and especially methanogenic microorganisms have been shown to be inhibited by surfactants. To protect these microorganisms from irreversible inhibition a measurement of the surfactant concentration is useful for the process control, but most analytical methods are too complicated and expensive for an on-line process control. It was shown that the titration of non-ionic surfactants is possible in the presence of biomass and in wastewater from textile wet processes using the Metrohm NIO-electrode. Titration and sampling were successfully performed with standard equipment. The software used for the process control of a lab-scale anaerobic treatment plant was also used to evaluate the obtained titration curves. This allowed performing the titrations without using a more expensive titrator.

Alcohols↗

PubMed2001

Integration of biotechnological wastewater treatment units in textile finishing factories: from end of the pipe solutions to combined production and wastewater treatment units.

Increasing costs for water, wastewater and energy put pressure on textile finishing plants to increase the efficiency of wet processing. An improved water management can decrease the use of these resources and is a prerequisite for the integration of an efficient, anaerobic on-site pretreatment of effluents that will further cut wastewater costs. A two-phase anaerobic treatment is proposed, and successful laboratory experiments with model effluents from the cotton finishing industry are reported. The chemical oxygen demand of this wastewater was reduced by over 88% at retention times of 1 day or longer. The next step to boost the efficiency is to combine the production and wastewater treatment. The example of cotton fabric desizing (removing size from the fabric) illustrates how this final step of integration uses the acidic phase bioreactor as a part of the production and allows to close the water cycle of the system.

Bioreactors↗

PubMed2001

Electrical stimulation influences mineral formation of osteoblast-like cells in vitro.

The aim of the present study was to assess the structure of newly formed mineral crystals after electrical stimulation of osteoblast-like cells in vitro. Pulsed electrical stimulation was coupled capacitively or semi-capacitively to primary osteoblast-like cells derived from bovine metacarpals. Computer calculations revealed that the chosen input signal (saw-tooth, 100 V, 63 ms width, 16 Hz repetition rate) generated a short pulsed voltage drop of 100 microV (capacitive coupled mode) and of 350 microV (semi-capacitive coupled mode) across the cell-matrix layer. Stimulated cultures showed an enhanced mineral formation compared to the non stimulated controls. In cultures exposed to capacitively coupled electric fields and in control cultures nodules and mineralized globules were found. Nodules with a diameter of less than 200 nm covered the cell surface, whereas mineral globules with a diameter of up to 700 nm formed characteristic mineral deposits in the vicinity of the cells similar to biomineral formations occurring in mineralizing tissues. In contrast, large rod-shaped crystals were found in cultures stimulated by semi-capacitive coupled electric fields, indicating a non-physiological precipitation process. In conclusion, osteoblasts in culture are sensitive to electrical stimulation resulting in an enhancement of the biomineralization process.

Animals↗

PubMed2001

Increase of RM3/1-positive macrophages in radiation-induced oral mucositis.

The purpose of this study was to describe the distribution patterns of various leukocyte subpopulations in the oral mucosa during the course of radiotherapy and to determine whether there are dose-dependent alterations, or any correlation between the clinical stages and the population density of specific leukocytes. The distribution and density of various leukocytes in oral mucosa in 13 head and neck cancer patients were immunohistochemically analysed before radiotherapy at 30 and 60 Gy and compared with the clinical degree of oral mucositis. Antibodies were used which characterized different subtypes of macrophages (27E10, 25F9, RM3/1) and recognized epitopes of granulocytes (CD15) and T cells (CD3, CD4, CD8). The study showed that whereas macrophages reactive with RM3/1 increased significantly at 30 Gy (p<0.01) and showed a further increase at 60 Gy (p<0.01), no significant alterations could be detected in the density of macrophages which stained positively for 27E10 or 25F9. Moreover, the percentage of macrophages reactive with RM3/1 showed a non-linear correlation with the clinical mucositis score (p<0.05). No significant alterations were detected in the percentage of T cells and granulocytes, compared with the values before radiotherapy. In conclusion, radiation-induced mucositis is characterized by features of an intermediate stage of an inflammatory response, suggesting active involvement of down-regulatory macrophages in its pathogenesis.

Aged↗

PubMed2001

Chronic psychosocial stress regulates the expression of both GR and MR mRNA in the hippocampal formation of tree shrews.

A persistent hyperactivity of the hypothalamic-pituitary-adrenal axis and thus elevated glucocorticoid levels are main neuroendocrine features of depressive symptomatology in humans. The broad range of effects that are set off by glucocorticoids is mediated by glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs), which themselves are subject to autoregulation. In order to investigate the impact of long-lasting psychological stress on corticosteroid receptor mRNA expression in the hippocampal formation, we employed the psychosocial stress paradigm in male tree shrews (Tupaia belangeri). By in situ hybridization studies and semiquantitative evaluation of stress-induced changes of GR and MR mRNA expression at the single-cell level, brain tissue from subordinate animals which were exposed to 27 days (1 h/day) of social confrontation was compared to that of nonstressed animals. Four weeks of stress exposure resulted in a downregulation of GR mRNA in the dentate gyrus and hippocampal subfields CA1 and CA3 of subordinate male tree shrews compared to controls. The MR mRNA content in these subfields of the anterior hippocampus was also clearly reduced. On the contrary, in a more posterior location on the longitudinal axis of the tree shrew hippocampus, the MR message was increased in subfields CA1 and CA3 and in the dentate gyrus. These results suggest a relevance of the stress-induced regulation of both corticosteroid receptor subtype mRNAs in a naturalistic challenging situation. Moreover, the differential regulation of MR mRNA along the rostrocaudal axis of the hippocampus adds another feature to the heterogenous composition of this structure.

Animals↗

PubMed2001

The grp78 promoter of Neurospora crassa: constitutive, stress and differentiation-dependent protein-binding patterns.

In order to characterize the transcriptional regulation of the grp78 (glucose-regulated protein 78 kDa) gene of Neurospora crassa, a 1.65-kb genomic fragment upstream of the protein-coding region was sequenced and analysed. A single transcription start point was mapped 160 nt upstream of the first codon. Several distinct protein-DNA binding sites were identified in the promoter region by non-radioactive scanning electrophoretic mobility shift analysis during growth, stress treatment and differentiation of conidia. A protein DNA binding complex induced by tunicamycin was linked to a promoter motif similar to the unfolded protein response element consensus of yeast. Another binding complex in differentiating aerial hyphae was found, which differs from the known cis-elements involved in conidiation-dependent gene expression.

Base Sequence↗

PubMed2001

[New aspects in managing mandibular fractures].

BACKGROUND: The aim of osteosynthetic mandibular fracture treatment is a bony bridging of the fracture gap. The gap distance and the fragment movement determine the micromovement in the gap tissue. They are known to be the main factors associated with the clinical outcome of fracture treatment. LITERATURE: The term fracture stability and the underlying mechanically modulated tissue reactions are not well described in the literature. MODEL: In this article we describe experimental results of strain related bone regenerate reactions in vivo. Additionally, in an in vitro model of osteosynthetic fracture treatment micromovements in the sense of bone strains were determined in the gap area. Implications for the osteosynthetic treatment of mandibular fractures are discussed on the basis of our biological and biomechanical results.

Animals↗

PubMed2001

[Treatment of frontobasal trauma and polytrauma].

BACKGROUND: This paper describes the historical development as well as current concepts of frontobasal fracture treatment by maxillofacial surgeons. TREATMENT CONCEPT: Based on the experience of many years a diagnostic and therapeutic treatment concept was developed, which proved to be adequate in 320 patients with 90 frontobasal fractures in the last five years.

Facial Bones↗

PubMed2001

[Mechanical stimulation of osteoblasts in cell culture].

BACKGROUND: Mechanical loading of bone is known to play a crucial role in bone remodeling and regeneration. Whereas the clinical effects of mechanically modulated bone healing have been extensively studied, less is known about the underlying mechanisms on a cellular level. This study was aimed at investigating the effects of uniaxial strains on osteoblast-like cells in culture. Mechanical loading was applied in physiological and hyperphysiological magnitudes. Nonstimulated cultures served as controls. RESULTS: Cultured primary bovine periosteal cells exhibited phenotypic features of osteoblast-like cells. Application of physiological strains (2,000 mu strain) led to a bone-specific expression of extracellular matrix proteins (osteonectin, osteocalcin, collagen type I). Hyperphysiological loads (10,000 mu strain) were associated with an increased synthesis of proteoglycans. Proliferation of cells was higher than the controls at 10,000 mu strain and showed no difference from physiologically loaded osteoblasts. DISCUSSION: Our study demonstrates that physiological loading of osteoblast-like cells enhances the regenerative capacity of bone, whereas hyperphysiological loads may impair bone regeneration.

Animals↗

PubMed2001

Late effects of radiotherapy on oral mucosa in humans.

In order to gain further understanding of the late effects of radiotherapy on oral mucosa, we analysed the histomorphological alterations, the cell populations in the subepithelial tissue, and the endothelial expression pattern of different adhesion molecules. Biopsies were taken from patients before irradiation, directly after 60 Gy, and 6-12 months after radiotherapy. Besides the histomorphological evaluation of the vessels, the endothelial expression of ICAM-1, VCAM-1 and E-selectin was determined as well as the distribution of LFA-1-, Mac-1-, VLA-4-, RM3/1-, 27E10- and 25F9-bearing cells in the subepithelial tissue. The expression of ICAM-1 was downregulated after radiotherapy, whereas the percentage of LFA-1- and VLA-4-bearing cells increased. VCAM-1 remained at low levels. The subepithelial infiltration was still dominated by RM3/1-positive macrophages. The number of vessels decreased, while the lumen of the remaining vessels increased. In conclusion, the late effects of radiotherapy are characterized by a decreased number of blood vessels and by significantly different expression patterns of the adhesion molecules studied, and of integrins and macrophage subpopulations, compared to the conditions before irradiation and directly after irradiation with 60 Gy.

Aged↗

PubMed2001

Influence of distraction rates on the temporomandibular joint position and cartilage morphology in a rabbit model of mandibular lengthening.

PURPOSE: Although various aspects of bone formation during distraction osteogenesis have been studied extensively, there are only limited experimental data concerning the influence of mandibular distraction rates on structural alterations in the temporomandibular joint (TMJ). In this study, a rabbit model of unilateral mandibular distraction was used to test the effects of various strain schedules on the position and morphology of the TMJ. MATERIAL AND METHODS: Fifty-two immature white female rabbits were used. The distraction procedure was performed using physiologic (2,000 microstrains, 1 per day) and elevated strain magnitudes (20,000 microstrains, 1 per day), as well as high strain magnitudes (200,000 and 300,000 microstrains, 1 per day). The investigation of the TMJ included clinical, radiologic, and histologic aspects. RESULTS: Clinical and radiologic examinations at the end of the distraction period showed no evidence of joint luxation even at maximal distraction rates. Histologic and ultrastructural analyses revealed a positive correlation between the degree of mechanical loading and the development of degenerative alterations in the cartilage. In samples distracted at hyperphysiologic strain magnitudes, all cartilaginous layers were reduced in the regions of the TMJ that had been exposed to the higher pressure forces. The fibrous layer became nearly completely destroyed. CONCLUSIONS: These experimental data show that distraction schedules with single but hyperphysiologic loads may lead to degenerative or even early arthrotic changes in the condyle. These data support the principle that distraction protocols should be performed without extensive mechanical loading on the TMJ.

Animals↗

PubMed2001

Tissue differentiation and cytokine synthesis during strain-related bone formation in distraction osteogenesis.

To investigate the contributions of various cytokines that are involved in mechanically related bone formation, we applied defined uniaxial strains in a rabbit model of mandibular elongation and examined the regenerating bone during early stages of dist raction osteogenesis by histomorphometry. We also measured serum concentrations of various cytokines during the distraction. Cell proliferation and differentiation indices correlated significantly (P<0.001) with the extent of load application. Serum concentrations of insulin-like growth factor-1 (IGF-1) decreased after osteotomy whereas transforming growth factor beta1 (TGFbeta1) showed a postoperative increase. Prostaglandin E2 (PGE2) concentrations were constant throughout the experimental period. Collagen degradation decreased slightly postoperatively and increased in samples exposed to higher magnitudes of strain. Our data show that it is the magnitude of mechanical strain that decides tissue response by a characteristic cell proliferation and differentiation. The operative trauma leads to inverse changes in serum concentrations of TGFbeta1 and IGF-1, thereby promoting the recruitment of osteoblastic precursor cells as well as collagen matrix synthesis.

Animals↗

PubMed2001

Microstructural investigations of strain-related collagen mineralization.

Distraction osteogenesis in rabbit mandibles after osteotomy can be used as an experimental model to study the microstructural features of mineralization of callus under defined mechanical loads. Our aim was to study the relation between the micromotions in the gap and the resulting features of mineralization of the matrix. We found that assembly of collagen and formation of crystals depended on the magnitude of the mechanical stress applied. At physiological bone strains (2000 microstrains), the callus had collagen type I in a mature bone-like extracellular arrangement, whereas at 20000 microstrains bundles were orientated predominantly towards the tension vector. Maximum loads (200000 microstrains) resulted in disorganized assembly of the collagen. Quantitative energy-dispersive analysis by X-rays confirmed that high strains were associated with substantially lower concentrations of calcium and phosphate. In contrast to bone-like apatitic formation of crystals at physiological strains, significantly fewer but larger crystals were detected by electron diffraction analysis in samples exposed to high strains. We suggest that mechanical stress regulates the assembly and mineralization of collagen during distraction osteogenesis.

Animals↗

PubMed2001

Mechanical tension in distraction osteogenesis regulates chondrocytic differentiation.

Differentiation of chondrocytes to cells of osteoblastic phenotype occurs during an interim period of bone development, fracture repair and distraction osteogenesis. To study the relationship between tension-stress and chondrogenesis, uniaxial strains (0 microstrains, 2000 microstrains, 20000 microstrains, 200000 microstrains, 300000 microstrains) were applied in a rabbit model of mandibular distraction osteogenesis. The results demonstrated that cell differentiation, apoptosis and tissue development in the newly formed gap tissue showed a correlation to the applied strain magnitudes. Only strains of 20000 microstrains resulted in a statistically significant (P<0.05) formation of cartilage struts with embedded chondrocyte-like cells. However, chondrocyte-like cells were rarely detected in samples distracted at lower or higher strain magnitudes. Osteoblasts appeared to replace cartilaginous matrix by mineralized bone matrix. The phenotypic change from chondrocytes to osteoblasts was accompanied by a decreased proteoglycan synthesis. a change in the expression from type II collagen towards type I and involved asymmetric cell divisions and apoptotic cell death. Therefore, we suggest that mechanical strain is an external stimulus responsible for phenotypic cell alterations.

Analysis of Variance↗