Biomedical subjects

K Bär

Publications and source records attributed to K Bär.

16 recordsLinked to original sources

PubMed2004

[Inadvertent intravenous infusion of 380 mg ropivacaine].

This is a report about an inadvertent intravenous infusion of 380 mg ropivacaine in a 84-year-old patient over a period of 1.75 h. The level of serum ropivacaine measured immediately after the end of the infusion as well as 2 h and 7 h later, was initially in the lower toxic range (free concentration of 0.48 micro g/ml). The patient showed no symptoms of intoxication neither clinically nor during the technical examinations (EEG, ECG). This case confirms the wide therapeutic range of ropivacaine.

Aged↗

PubMed2002

Enhanced mutation and neoplastic transformation in human cells by 29 kVp relative to 200 kVp X rays indicating a strong dependence of RBE on photon energy.

The fundamental assumption implicit in the use of the atomic bomb survivor data to derive risk estimates for occupational and medical exposures is that the gamma rays of Hiroshima and Nagasaki are considered as equal efficiencies to other low LET radiations up to an LET of 10 keV.micron-1. For breast cancer induction, neoplastic cell transformation, mutation, reciprocal translocations and dicentrics in human lymphocytes, a strong and very similar dependence of the RBE values on photon energy or on LET is observed. Experimental data on mutation induction and neoplastic cell transformation in human cells show that 29 kVp X rays are by a factor of 4 and 3.4, respectively, more effective compared with 200 kVp X rays. These data are in excellent agreement with the data in the literature.

Cell Transformation, Neoplastic↗

PubMed2002

Enhanced neoplastic transformation by mammography X rays relative to 200 kVp X rays: indication for a strong dependence on photon energy of the RBE(M) for various end points.

The fundamental assumption implicit in the use of the atomic bomb survivor data to derive risk estimates is that the gamma rays of Hiroshima and Nagasaki are considered to have biological efficiencies equal to those of other low-LET radiations up to 10 keV/microm, including mammography X rays. Microdosimetric and radiobiological data contradict this assumption. It is therefore of scientific and public interest to evaluate the efficiency of mammography X rays (25-30 kVp) to induce cancer. In this study, the efficiency of mammography X rays relative to 200 kVp X rays to induce neoplastic cell transformation was evaluated using cells of a human hybrid cell line (CGL1). For both radiations, a linear-quadratic dose-effect relationship was observed for neoplastic transformation of CGL1 cells; there was a strong linear component for the 29 kVp X rays. The RBE(M) of mammography X rays relative to 200 kVp X rays was determined to be about 4 for doses < or = 0.5 Gy. A comparison of the electron fluences for both X rays provides strong evidence that electrons with energies of < or = 15 keV can induce neoplastic transformation of CGL1 cells. Both the data available in the literature and the results of the present study strongly suggest an increase of RBE(M) for carcinogenesis in animals, neoplastic cell transformation, and clastogenic effects with decreasing photon energy or increasing LET to an RBE(M) approximately 8 for mammography X rays relative to 60Co gamma rays.

Animals↗

PubMed2002

[Prognostic risk factors in children and adolescents with craniocerebral injuries with multiple trauma].

220 of 268 polytraumatized patients (82.1%) presented an additional head injury, which increased the mortality significantly. By the Hannover Polytrauma Score we could demonstrate that the severity of the polytrauma and the prognosis depended on the extent of the brain injury. Important risk factors were skull fractures and shock on arrival. 66.7% of the patients with a severe brain trauma and a skull fracture died; without this fracture, only 36.8% died. 76.1% of the children with a systolic blood pressure (SBP) > 80 mm Hg survived, but only 31.2% with a SBF < or = 80 mm Hg did not die. For all polytraumatized children we recommend a computer tomography of the head. In spite of a negative initial CT a follow up CCT should be performed.

Adolescent↗

PubMed1999

Prophylaxis of secondary osteoarthrosis with spherical osteotomy in residual acetabular dysplasia. Analysis of predictive factors of success.

The aim of this study was to evaluate whether or not spherical acetabular osteotomy prevents progression of osteoarthrosis in hip joints with residual dysplasia and which radiological parameters can be used postoperatively as predictive factors concerning the outcome. Sixty-eight out of 78 joints were re-investigated with a mean follow-up of 11.2 years after the index operation. Twenty-three Wagner type 1 and 45 type II osteotomies were performed. At surgery, the mean age of the patients was 26 years; 90% of joints showed no or mild degenerative changes, 26% presented with a good or excellent Harris hip score. At follow-up, 28% of patients had improved in function, mean Harris hip score rated 75 points. The mean center-edge (CE) angle improved from -4 degrees to 18 degrees, and the anterior center-edge (ACE) angle from -4 degrees to 26 degrees. The weight-bearing zone of the acetabulum showed an acetabular index (AC) angle of 27 degrees preoperatively and 14 degrees postoperatively. Statistical analysis proved a significant correlation between the normal postoperative values of the acetabulum/femoral-head index of Heyman and Herndon and the absence of degenerative joint changes at follow-up. 73.5% of the hips had not markedly progressed to secondary osteoarthrosis, but 26.5% of joints had deteriorated: 7.4% of them due to perioperative complications and early postoperative trauma. In 8.8% (severe dysplasia) only partial reorientation was possible, which explains the progression of arthrosis, but 10.2% progressed despite sufficient correction.

Acetabulum↗

PubMed1999

[3-dimensional registration of micro-movements of vertebral implants by a specially adapted measuring system using magnetic transducers].

The aim of this study was to develop a biomechanical experimental set-up to quantify motion of ventrally inserted spinal implants at the implant/bone interface. The model we used was the vertebral column of the calf. Lumbar vertebrae L2 to L4 were "instrumented" with a screw-rod system. The adjacent vertebrae L1 and L5 were connected to a servohydraulic testing machine and axial compression applied. Shortening of the specimen and three-dimensional movement of the most cranial implant relative to the bone was recorded using 3 electromagnetic transducers. 100,000 cycles of axial loading varying between -0.5 kN and -1 kN were applied. Static shortening of the specimen of 8.5 mm and an elastic movement of 180 to 280 microns were measured. The greatest amplitude of single-plane motion was recorded in the sagittal plane in both static and elastic modes. Implant motion within each cycle was recorded accurately as load-displacement curves within a range of 1.35 to 30 microns. With this test set-up, primary stability of different spinal implant systems can be compared. The use of electromagnetic transducers permits three-dimensional implant motion analysis even when only a mono-axial servohydraulic testing machine is available.

Animals↗

PubMed1995

Molecular mechanism of potentially lethal damage repair. I. Enhanced fidelity of DNA double-strand break rejoining under conditions allowing potentially lethal damage repair.

This study contributes to the elucidation of the molecular mechanism underlying potentially lethal damage (PLD) repair. Repair of DNA double-strand breaks (dsbs) is involved in PLD repair in yeast, i.e. in the enhanced survival of cells due to post-irradiation treatment under non-growth conditions before plating cells on nutrient agar (growth conditions). However, dsbs are rejoined when cells are kept either in non-growth or growth medium. One possibility to explain the enhanced survival of cells after post-irradiation treatment in non-growth medium might be an enhanced fidelity of dsb rejoining under non-growth relative to growth conditions. We have addressed this problem by using a plasmid-mediated assay. Into one of the two selectable plasmid markers a single dsb was introduced by a restriction enzyme. The cut plasmid was transfected into an appropriate yeast mutant. Transformants that had correctly rejoined the dsb were selected on the basis of restoration of the function of the cut gene. The yeast mutant was allowed to rejoin the cut plasmid under either non-growth or growth conditions. The results show that the fidelity of dsb rejoining is higher in cells kept under non-growth relative to growth conditions.

DNA Repair↗

PubMed1995

Temperate bacteriophages are common among Actinobacillus actinomycetemcomitans isolates from periodontal pockets.

Actinobacillus actinomycetemcomitans is a suspected etiologic agent in destructive periodontal diseases. The detection of bacteriophages in A. actinomycetemcomitans in the subgingival plaque of patients with rapidly destructive forms of periodontitis led to the hypothesis that bacteriophage infection might increase the virulence of this bacterium (19). A. actinomycetemcomitans was isolated from 68 subjects from the Netherlands and Switzerland with localized juvenile periodontitis, rapidly progressing periodontitis, or adult periodontitis, and was tested for the presence of temperate bacteriophage with the overlay plate technique. More than half of the A. actinomycetemcomitans strains were found to release bacteriophage which formed individual plaques on indicator strains. Electron microscopy of preparations from 7 strains revealed virions with an icosahedral head and a contractile tail typical for double-stranded DNA bacteriophages. The presence of A. actinomycetemcomitans carrying temperate bacteriophage was not correlated with the composition of the subgingival microflora nor with the clinical form of periodontal disease. Destructive periodontal disease of subjects with phage-carrying A. actinomycetemcomitans was not more severe than of subjects with phage-free A. actinomycetemcomitans as determined by several clinical parameters. In contrast, the pocket depth and the attachment loss were significantly lower for adult periodontitis subjects with phage-carrying A. actinomycetemcomitans. It seems unlikely that the frequently occurring temperate bacteriophages increase significantly the virulence of A. actinomycetemcomitans.

Adult↗

PubMed1993