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Biomedical subjects

C Voigt

Publications and source records attributed to C Voigt.

At least 37 records · Page 2Linked to original sources
PubMed2001

Determination of erythrocyte antioxidant capacity in haemodialysis patients using electron paramagnetic resonance.

BACKGROUND: The increased oxidative stress of uraemia is caused both by an increased generation of oxygen-free radicals and a decrease of antioxidative forces. There are, however, conflicting data concerning disturbances of the radical-scavenging power of red blood cells (RBCs) in uraemic patients. METHODS: The antioxidant capacities of the RBCs of 10 haemodialysis (HD) patients and 10 controls were examined after treatment with 0.324 mM tert-butylhydroperoxide (t-BOOH) in phosphate-buffered saline at 37 degrees C using electron paramagnetic resonance (EPR) with 5,5-dimethylpyrroline-N-oxide (DMPO) as a spin trap and glutathione (GSH) regeneration as an indicator of hexose monophosphate shunt (HMPS) activity. EPR investigations were also done after pre-incubation with N-ethylmaleimide (NEM) to inhibit the GSH system. Furthermore, we determined the RBC redox state in 15 HD patients and 15 controls. RESULTS: There was no difference between HD patients and controls in the elimination of t-BOOH-generated free radicals in the RBCs. A more than 20-fold increase in radical concentration was observed after GSH trapping with NEM. In this case, we found a delayed decrease of the relative radical concentration in HD patients compared with controls with a significant difference after 7 min (2.2+/-0.26 vs 1.60+/-0.21; P=0.005) and after 10 min (1.82+/-0.41 vs 0.83+/-0.44; P=0.001). GSH regeneration via HMPS did not differ between the RBCs of HD patients (99.5+/-13.5 nmol/min x ml RBC) and those of the controls (94.2+/-16.9 nmol/min x ml RBC). There were no differences in the RBC concentrations of GSH, GSSG, NADP, NADPH, and in the GSH/GSSG and NADP/NADPH ratios between HD patients and controls. CONCLUSIONS: These data suggest a strong antioxidant potential in the GSH system of erythrocytes without any evidence of a disturbance in HD patients. The HMPS pathway also appears not to be impaired in the RBCs of HD patients. However, the slower radical elimination in the RBCs of HD patients after inhibition of GSH-depending radical scavengers as compared with controls indicates a defect in the antioxidant forces outside the GSH system, and could be one reason for the reduced lifespan of RBCs in HD patients.

Adult↗
PubMed2000

Expression of beta-arrestins in toxic and cold thyroid nodules.

beta-Arrestins mediate agonist dependent desensitization of G protein-coupled receptors. Somatic TSH receptor mutations were identified in the majority of hot thyroid nodules. When transiently overexpressed in COS 7 cells these mutations resulted in constitutive activation of the cAMP pathway. However, the in vivo mechanisms and the in vivo desensitization of these TSH receptor mutations are unknown. Moreover, constitutively activated beta-adrenergic receptors are known to be constitutively desensitized. Therefore, we investigated the expression of beta-arrestins in toxic thyroid nodules (TTNs) with and without somatic TSH receptor mutation and in cold thyroid nodules (CTNs) by Western blotting and ELISA. Expression of beta-arrestin 2 was increased in all TTNs while beta-arrestin 2 expression was decreased in CTNs compared to their corresponding surrounding tissue. The mean beta-arrestin 1 expression was unchanged in the cytosol of TTNs, in membranes and cytosol of CTNs and decreased in the membranes of TTNs compared to their surrounding tissue. Transient coexpression of beta-arrestins 1 or 2 with the TSH receptor in HEK 293 cells and subsequent determination of cAMP showed that in vitro both beta-arrestins interact with the TSH receptor and are able to desensitize the receptor. The increased beta-arrestin 2 expression in TTNs and the desensitization of the TSH receptor by beta-arrestin 2 in vitro suggest that the beta-arrestin 2 expression is cAMP dependent and that beta-arrestin 2 very likely desensitizes the constitutively activated TSH receptor in toxic thyroid nodules.

Arrestins↗
PubMed2000

Nitric acid trihydrate (NAT) in polar stratospheric clouds.

A comprehensive investigation of polar stratospheric clouds was performed on 25 January 2000 with instruments onboard a balloon gondola flown from Kiruna, Sweden. Cloud layers were repeatedly encountered at altitudes between 20 and 24 kilometers over a wide range of atmospheric temperatures (185 to 197 kelvin). Particle composition analysis showed that a large fraction of the cloud layers was composed of nitric acid trihydrate (NAT) particles, containing water and nitric acid at a molar ratio of 3:1; this confirmed that these long-sought solid crystals exist well above ice formation temperatures. The presence of NAT particles enhances the potential for chlorine activation with subsequent ozone destruction in polar regions, particularly in early and late winter.

Journal Article↗
PubMed1999

Chemical analysis of polar stratospheric cloud particles

A balloon-borne gondola carrying a particle analysis system, a backscatter sonde, and pressure and temperature sensors was launched from Kiruna, Sweden, on 25 January 1998. Measurements within polar stratospheric cloud layers inside the Arctic polar vortex show a close correlation between large backscatter ratios and enhanced particle-related water and nitric acid signals at low temperatures. Periodic structures in the data indicate the presence of lee waves. The H2O/HNO3 molar ratios are consistently found to be above 10 at atmospheric temperatures between 189 and 192 kelvin. Such high ratios indicate ternary solution particles of H2O, HNO3, and H2SO4 rather than the presence of solid hydrates.

Journal Article↗
PubMed1999

Tissue engineering of biphasic joint cartilage transplants.

In isolated posttraumatic or idiopathic joint defects the chondral layers and adjacent subchondral spongy bone are usually destructed. For regeneration we suggest the in vitro formation of a cartilage-coated biomaterial carriers (biphases) in order to fill the correspondingjoint defects. In this study Biocoral, a natural coralline material made of calcium carbonate, and calcite, a synthetic calcium carbonate, were used as supports for the cultivation of bovine chondrocytes in a three-dimensional polymer fleece. The cell-polymer-structure was affixed to the biomaterial with a fibrin-cell-solution. The artificial cartilage formed a new matrix and fused with the underlying biomaterial. The results indicate a promising technical approach to anchor tissue engineered cartilage in joint defects.

Animals↗
PubMed1998

Purification and properties of methanol dehydrogenase from Methylosinus sp. WI 14.

Similarly to the recently described methanol dehydrogenase (MDH) from Methylocystis sp. GB 25 (Grosse et al. 1997) MDH from Methylosinus sp. WI 14 is able to catalyse the oxidation of methanol to formate directly. The enzyme was purified about 9-fold to electrophoretic homogeneity and is localised in the soluble fraction. The relative molecular mass of the native enzyme has been determined to be 140 kDa. It is composed of two identical subunits of relative molecular mass 70 kDa. The amino terminal sequence shows a strong similarity (a match of 80% over the first 20 amino acids) to the MDH from Methylocystis sp. GB 25. PQQ could be detected as the prosthetic group of MDH in the purified enzyme fraction by using the apoenzyme of a membrane-bound glucose dehydrogenase from Pseudomonas aeruginosa. A PQQ ratio of 1.3 per mole MDH was estimated. The purified enzyme has an optimum activity at pH 9.0 and at 57 degrees C. MDH from Methylosinus sp. WI 14 oxidises only primary alcohols up to octanol and several aldehydes. The estimated K(m)-values vary between 0.18 mM for the sorbic alcohol and 6.3 mM for butanol and show no dependence upon the chain length.

Alcohol Oxidoreductases↗
PubMed1998

Gas exchange during hovering flight in a nectar-feeding bat Glossophaga soricina.

Glossophagine nectar-feeding bats exploit flowers while hovering in front of them. Aerodynamic theory predicts that power output for hovering flight in Glossophaga soricina is 2.6 times higher than during horizontal flight. We tested this prediction by measuring rates of gas exchange during hover-feeding. Five individuals of Glossophaga soricina (mean mass 11.7 g) were trained to feed from a nectar dispenser designed as a flow-through respirometry mask. Single hover-feeding events lasted for up to 4.5 s. Measured rates of gas exchange varied as a function of hovering duration. O2 and CO2 during short hovering events (up to 1 s) were 20.5+/-6.7 ml g-1 h-1 (N=55) and 21.6+/-5.6 ml g-1 h-1 (N=39) (means +/- S.D.), respectively. These values are in the range of a previous estimate of the metabolic power input for level forward flight (23.8 ml O2 g-1 h-1). However, during hovering events lasting longer than 3 s, oxygen uptake was only 16.7+/-3.5 ml g-1 h-1 (N=73), which is only 70 % of the value expected for forward flight. Thus, bats reduced their rate of oxygen uptake during longer periods of hovering compared with level forward flight. This result is in contrast to the predicted hovering cost derived from aerodynamic theory. The exact metabolic power input during hovering remains uncertain. During longer hovering events, bats were probably not in respiratory steady state, as indicated by the deviation of the respiratory exchange ratio from the expected value of 1 (oxidization of nectar sugar) to the measured value of 0.8.

Animals↗
PubMed1996

Procollagen alpha 1(I) transcripts in cells near the interface of coralline implants in rats, detected by in situ hybridization.

Cells procollagen alpha 1(I) transcripts were demonstrated at the interface of natural coral mineral implanted in the femur of rats after 7, 14, 21 and 28 days by in situ hybridization with digoxigenin-labelled RNA probes. Procollagen alpha 1(I) transcripts were detectable in osteoblasts between 7 and 28 days after implantation. As early as 7 days after implantation, procollagen alpha 1(I) RNA expression was also demonstrated in fibroblasts; the transcripts steady state levels decreased until the 28th day, when they subsided completely. The development of bone was significantly during the 4 weeks of implantation. Inhibition of bone development by the coralline material could not be recorded.

Animals↗
PubMed1995

Nanoapatite and organoapatite implants in bone: histology and ultrastructure of the interface.

This article reports on the reaction of bone to a new family of nanocrystalline hydroxyapatite biomaterials with crystal sizes similar to those of human bone. Pure nanoapatite cylinders and organoapatite cylinders containing a synthetic nanopeptide were analyzed 28 days after implantation into the spongy bone of Chinchilla rabbits. The experimental techniques used for analysis were light microscopy, scanning electron microscopy, and transmission electron microscopy. Both implant types were well incorporated, and interface events were found to be similar to those observed on human bone surfaces with regard to resorption by osteoclast-like cells and bone formation by osteoblasts. Different types of giant cells were observed resorbing the outermost surfaces of implants. There seemed to be both dissolution of the implant and particulate biodegradation leading to less dense implant regions near the interface, whereas the bulk of the implants remained denser. Transmission electron micrographs revealed that bone bonding occurred with and without an afibrillar intervening layer. Given the biologic reaction observed, these implant materials should be suitable for bone replacement and the organoapatite form could be useful for additional functions such as the release of drugs and optimized release of antibiotics, growth factors, or other substances. The organic component can also be used to control physical properties in a bony implantation bed.

Animals↗
PubMed1994

[Malignant atrophic papulosis].

A 53-year-old woman had noticed numerous papules on her trunk and proximal parts of the limbs. They had healed with a central scar surrounded by a reddish wall. Four months later she had to undergo laparotomy for ileus, resulting from a perforation in the region of the middle jejunum: it was excised and sutured over. At laparotomy white plaque-like lesions were noted on the serosa of both small and large intestine. Histological examination of the jejunal exudate and of a skin biopsy both demonstrated malignant atrophic papulosis (Köhlmeier-Dégos' disease). Treatment with ticlopidine, a platelet-aggregation inhibitor (250 mg twice daily), was initiated and she has now been free of extracutaneous symptoms for 6 years.

Biopsy↗
PubMed1994

[Treatment of acromioclavicular joint dislocation with the Rahmanzadeh joint plate].

Type Tossy III dislocations of the acromioclavicular joint (AC) are treated surgically in German-speaking countries. There is considerable rotation and tilting in the AC joint with elevation or abduction of the shoulder joint over 90 degrees. Thus, in the majority of countless surgical procedures, the abduction and elevation are restricted or immobilized for long periods in abduction strapping or other types of movement restriction. The AC joint plate developed by Prof. Rahmanzadeh enables early functional, complete physical therapy since the plate permits rotation and tilting. Over a period of 13 years, 133 patients have been treated with this plate. 83 patients could be included in the follow-up examination. On the average, the follow-up was 4.8 years after surgery. In the evaluation score according to Taft et al., 76% of the patients in the follow-up showed very good or good results. The surgical procedure is standardized and will show that no immobilization is required postoperatively. It could already be seen of the first postoperative day that patients could passively elevate up to 90 degrees. At the latest, free active abduction and elevation are reached after 5 weeks. Material removal should take place after 12 weeks. Due to the limited tissue covering in the area of the AC joint, a higher rate of infection can be expected than in other osteosyntheses. However, there were no persistent infections. Transitory problems in the implantation were remedied by constructive changes in the course of its development. Rahmanzadeh's AC plate is outstandingly suited for surgical treatment of type Tossy III AC joint injuries and for the treatment of lateral clavicle fractures.

Acromioclavicular Joint↗
PubMed1994

[Herpes simplex digitalis--an important differential diagnosis of paronychia].

Herpes simplex infection of the hand is often falsely diagnosed as a pyogenic paronychia or felon and treated as such, because the clinical picture is not known and pathogen isolation is difficult. However, the surgical treatment of herpes digitalis is contraindicated, since it promotes the development of superinfections and triggers recurrence. The pathogen can be isolated in cell cultures prepared from the vesicle contents or a smear from the vesicle base. Serological antibody testing is unreliable. Topical application of Acyclovir cream (Zovirax) is the treatment of choice.

Acyclovir↗
PubMed1994

[Using of a Wagner stem in revision-arthroplasty following loosening of a total hip endoprosthesis].

During a three-year period to 50 patients a Wagner femoral revision endoprosthesis was implanted. The mean age of the patients was 67.5 years. In 39 patients replacement of an endoprosthesis was involved, in 7 patients the indication was fracture in the area of the endoprosthesis, 4 patients were operated for other reasons. Of 44 patients, who were operated at least 12 months ago, 33 were checked. Sixteen patients were classified according to Harris' score as very good, 9 as good and in 4 the result was satisfactory or poor. Wagner's revision shank is suitable in particular in damage of the proximal femur, where in case of firm distal anchoring and early ability to burden the extremity proximally, marked new formation of bone was observed with restoration of the pipe-shaped bone structure.

Aged↗
PubMed1993

Cerebral amyloid angiopathy. Frequency, significance and immunohistochemistry.

For the assessment of the anatomical distribution of cerebral amyloid angiopathy (CAA) as well as that of amyloid plaques (AP), 955 post-mortem brain specimens from 653 patients (aged 14 to 95 years) were made available from a general hospital. Using histological and immunohistochemical techniques, we demonstrated amyloid angiopathy chiefly in the occipital, parietal and temporal regions. Senile plaques were mostly found in parietal, temporal and occipital areas. In our cases, neurofibrillary tangles were rarely prominent in the regions examined. There was often a significant difference in the frequency of amyloid angiopathy and of plaques in distinct areas between men and women. Congophilic angiopathy was associated with senile plaques in 82.3%, and neurofibrillary tangles with plaques in 76.9%. In comparison, the correlation of amyloid plaques with CAA (32.5%) and of plaques with neurofibrillary tangles (11.5%) was less pronounced. There was a strong association of cerebral vascular amyloid with age in both sexes, it was more pronounced in women than in men. Unexpectedly, CAA showed a decrease in frequency in men in the 7th and 8th decade of life. In addition, there was a positive correlation between the amount of CAA and spontaneous hemorrhages, but no correlation with ischemic encephalopathy. Immunohistochemistry showed that cerebral amyloid was neither amyloid of the AA- nor of the ATTR-(Antitransthyretin-, formerly anti-AF)-type. An antibody to the beta-protein (anti-A beta) showed cerebral vascular deposits to be congruent with the Congo red method, whereas senile plaques stained weakly and neurofibrillary tangles could not be stained at all with these antibodies.

Adolescent↗
PubMed1992

Treatment of extensive aseptic defects in old Achilles tendon ruptures: methods and case reports.

Defect bridging is still problematic in the secondary treatment of Achilles tendon ruptures. Smaller defects can be treated without problems by the well-known standardized methods, whereas other methods have to be applied for treating larger defects. Free transplants with autogenous or exogenous material should be mentioned in this context. Complications are more likely to occur with exogenous material, free transplants from the fascia lata require an additional intervention to remove the transplant from another localization. These methods cannot be applied to achieve reliable restoration of continuity for defects with a length of 10 cm. Therefore, in these special cases, we carry out the tendon transplantation with a free tendon-muscle graft from the triceps surae muscle. We achieved reliable restoration of continuity with complication-free healing of the free transplant in, up to now, three cases, in association with the formation of a strong, functionally high grade scar plate in the area of the tendon.

Achilles Tendon↗
PubMed1991

The early host and material response of bone-bonding and non-bonding glass-ceramic implants as revealed by scanning electron microscopy and histochemistry.

The interface of bone-bonding and non-bonding glass-ceramics in the femur of of rats with the concomitant material and host response has been investigated by scanning electron microscopy (SEM) and histochemistry after transverse fractures in the interface level. During wound healing around these implants, four overlapping phases could be distinguished: (1) blood clot formation, (2) formation of organization tissue, (3) formation of primary bone and calcification, and (4) remodelling which lasts from months to years. This sequence of healing was disturbed around metal ions containing non-bonding implants, as shown by a longer settlement of acid phosphatase positive macrophages and a disturbed calcification at the surface of the material. Only bone-bonding implants developed considerable changes in surface morphology due to leaching and corrosion phenomena. A preferential leaching of the glass moiety, starting at the phase transition between glass and ceramic, contributes to the production of surface elevations which provide adhesion points for fibres and fibrils. Subsequent mineralization of inserting fibres contributes to a tensile strength at the interface. These findings are essential for further understanding of bone-bonding mechanisms and for further development of surface-reactive materials.

Animals↗
PubMed1991

[Modified after care following primary management of rupture of the Achilles tendon].

During the period ranging from 1975 to 1988, 169 Achilles tendon ruptures were operated on in the Department of Traumatology and Reconstructive Surgery of Steglitz Medical Center, Free University of Berlin. The majority of these ruptures, i.e. 149 cases, were due to sports injuries. In order to comply with our patients' wish for quick rehabilitation, we have altered our follow-up treatment concept since 1982. The surgical technique remained the same in the form of a Bunnell suture with wire or absorbable suture material. There was an initial post-operative immobilization for five to seven days in a dorsal femoral plaster splint at a 30 degree bending position. The ankle joint was immobilized in a neutral position from the start. After approximately one week, the lower leg was put in a walking cast in a neutral position. The patients were allowed to put full load on the leg. After an additional four weeks, the cast was removed and functional follow-up treatment started. The two patient collectives that were compared did not significantly differ with regard to age structure and accident mechanisms or accident causes. Changes in the follow-up treatment resulted in a marked reduction in duration from 14 to 10 weeks. Standing on the toes was likewise possible after 10 weeks. Sports activities could be resumed after four instead of six months, as before. The postoperative rate of complications was low. There were only 10 infections in the total patient collective, one being a deep-wound infection requiring surgical intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Achilles Tendon↗