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O Sauer

Publications and source records attributed to O Sauer.

At least 19 recordsLinked to original sources
PubMed1999

A simple model for examining issues in radiotherapy optimization.

Convolution/superposition software has been used to produce a library of photon pencil beam dose matrices. This library of pencil beams is designed to serve as a tool for both education and investigation in the field of radiotherapy optimization. The elegance of this pencil beam model stems from its cylindrical symmetry. Because of the symmetry, the dose distribution for a pencil beam from any arbitrary angle can be determined through a simple rotation of a pre-computed dose matrix. Rapid dose calculations can thus be performed while maintaining the accuracy of a convolution/superposition based dose computation. The pencil beam data sets have been made publicly available. It is hoped that the data sets will facilitate a comparison of a variety of optimization and delivery approaches. This paper will present a number of studies designed to demonstrate the usefulness of the pencil beam data sets. These studies include an examination of the extent to which a treatment plan can be improved through either an increase in the number of beam angles and/or a decrease in the collimator size. A few insights into the significance of heterogeneity corrections for treatment planning for intensity modulated radiotherapy will also be presented.

Computer Simulation↗
PubMed1998

High-resolution native and complex structures of thermostable beta-mannanase from Thermomonospora fusca - substrate specificity in glycosyl hydrolase family 5.

BACKGROUND: . beta-Mannanases hydrolyse the O-glycosidic bonds in mannan, a hemicellulose constituent of plants. These enzymes have potential use in pulp and paper production and are of significant biotechnological interest. Thermostable beta-mannanases would be particularly useful due to their high temperature optimum and broad pH tolerance. The thermophilic actinomycete Thermomonospora fusca secretes at least one beta-mannanase (molecular mass 38 kDa) with a temperature optimum of 80 degreesC. No three-dimensional structure of a mannan-degrading enzyme has been reported until now. RESULTS: . The crystal structure of the thermostable beta-mannanase from T. fusca has been determined by the multiple isomorphous replacement method and refined to 1.5 A resolution. In addition to the native enzyme, the structures of the mannotriose- and mannohexaose-bound forms of the enzyme have been determined to resolutions of 1.9 A and 1.6 A, respectively. CONCLUSIONS: . Analysis of the -1 subsite of T. fusca mannanase reveals neither a favourable interaction towards the axial HO-C(2) nor a discrimination against the equatorial hydroxyl group of gluco-configurated substrates. We propose that selectivity arises from two possible mechanisms: a hydrophobic interaction of the substrate with Val263, conserved in family 5 bacterial mannanases, which discriminates between the different conformations of the hydroxymethyl group in native mannan and cellulose; and/or a specific interaction between Asp259 and the axial hydroxyl group at the C(2) of the substrate in the -2 subsite. Compared with the catalytic clefts of family 5 cellulases, the groove of T. fusca mannanase has a strongly reduced number of aromatic residues providing platforms for stacking with the substrate. This deletion of every second platform is in good agreement with the orientation of the axial hydroxyl groups in mannan.

Actinomycetales↗
PubMed1998

In vitro and in vivo porphyrin accumulation by C6 glioma cells after exposure to 5-aminolevulinic acid.

Several malignant tissues synthesize endogenous porphyrins after exposure to 5-aminolevulinic acid (5-ALA). The present experiments have been designed to elucidate whether the C6 glioma cell, a model cell for human malignant glioma, similarly synthesizes porphyrins when exposed to 5-ALA, and whether specific synthesis occurs when C6 cells are inoculated into rat brains to form a tumor. In this situation the blood-brain barrier may interfere with 5-ALA availability, and spreading of porphyrins with edema outside the tumor may occur. Flow cytometry is used to determine the course of cell volume and porphyrin fluorescence intensities in cultured C6 cells which are incubated in 1 mM 5-ALA. For the induction of experimental brain tumors, 10(4) untreated C6 cells are inoculated into the brains of rats. After 9 days animals receive 100 mg 5-ALA/kg body weight. Brains are removed after 3, 6, or 9 h and frozen coronal sections obtained for H/E staining or fluorescence spectography. Cultured C6 cells show a linear increase of protoporphyrin IX fluorescence after exposure to 5-ALA, which begins to plateau after 85 min. Marked fluorescence is also observed in solid and infiltrating experimental tumor. However, faint fluorescence also occurs in normal tissue, basal pia, choroid plexus, and, more obviously, in white-matter tracts bordering the tumor (maximal distance: 1.5 +/- 0.7 mm). The observations demonstrate that C6 cells synthesize protoporphyrin IX after exposure to 5-ALA in vitro and in vivo. However, when utilizing 5-ALA for fluorescence detection or photodynamic therapy of brain tumors, attention should be paid to the possibility of protoporphyrin IX occurring outside the tumor.

Aminolevulinic Acid↗
PubMed1994

[The multisegmental electron irradiation of the chest wall following ablative therapy of breast cancer].

PURPOSE: The paper describes the clinical aspects of postoperative irradiation of breast cancer using electron arc technique at the chest wall. The value of the treatment is assessed by long-term results concerning the rate of local recurrences and side effects. The advantages of the procedure are described with regard to physical and technical aspects. PATIENTS AND METHODS: After mastectomy, 117 patients underwent and adjuvant radiotherapy of the chest wall by multisegmental electron rotation technique with energies between 4 and 14 MeV. The number and angular range of the segments as well as the energy of the electrons depended on the peculiar thickness of the chest wall. 25 times 2 Gy were applied within five weeks. The treatment planning is based on a patient model constructed from five CT-slices at least. RESULTS: In four cases (3.4%) a local relapse and in one case (0.9%) a relapse in supraclavicular lymphatics was found. The recurrences appeared after an average period of 32 months. The mean observation time was 70 months. In 37 women (32%) distant metastases were seen after 29 months on an average. The five-year survival rate is 73.5%. CONCLUSION: In comparison to usual techniques using photons the described method shows a more homogeneous dose distribution to the chest wall and a reduction of lung radiation exposure. The clinical result of this dose adaptation to the treatment volume is a lower rate of local relapses and of side effects, inclusive late reactions. It can be suggested that the efficiency of the procedure will be ameliorated in future using special electron compensators. This will result in a more favorable adaptation of dose distribution to the anatomical situation in regard to the cranio-caudal profile.

Adult↗
PubMed1990

Reconstruction of high-energy bremsstrahlung spectra by numerical analysis of depth-dose data.

The determination of the spectral distribution of a photon beam is important for exact dosimetry and for the calculation of dose distributions. Direct measurements are not possible because of physical reasons. The approximation described uses a numerical reconstruction method based upon depth-dose data measured in water. The basic idea of the method is that a measured depth-dose curve can be thought of as a weighted superposition of monoenergetic depth-dose curves. The monoenergetic data are obtained by convolution of Monte Carlo generated energy deposition kernels. They were fitted to the measured data by means of a least squares method. Several constraints were applied to the superposition coefficients. The optimization algorithm uses the Wolfe reduced gradient method. The results were compared to Monte Carlo generated thick target spectra.

Algorithms↗
PubMed1990

[Surgical aspects of bone tumors in children].

The combination of surgical procedures with chemotherapy and radiotherapy has improved the disease-free 3-year survival rate in children treated for malignant bone tumors, and it is now 80%. As far as the quality of life is concerned, limb-conserving technique should be preferred whenever possible. The rate of local recurrence is equal to that after amputation, while the rate of pulmonary metastasis somewhat higher, for reasons that are still unknown. It is shown that the decision for amputation or segmental resection has to be considered strictly individually for each patient.

Amputation, Surgical↗
PubMed1988

[Accomplishments of tumor surgery in bone sarcoma in childhood].

Neither chemotherapy nor surgery alone provided satisfactory treatment of bone sarcomas in children. However, their combination improved the 3-year-survival rate by up to 80% in the last decade. For better life quality, limb-sparing techniques like en-bloc-resection, rotation plasty or endoprosthesis should be preferred instead of amputation, if they are possible within the demands of radical oncological surgery. The significantly higher incidence of pulmonary metastasis of en-bloc-resection compared to that of ablative surgery as shown in the COSS-80-study points out that limb-sparing surgery is still problematic and needs further technical improvement in the future.

Bone Neoplasms↗
PubMed1988

[3-D reconstruction of the breast implants from isocentric stereoscopic x-ray images for the application monitoring and irradiation planning of a remote-controlled interstitial afterloading method].

An individual irradiation planning and application monitoring by ISXP is presented for a remote-controlled interstitial afterloading technique using 192Ir wires which is applied in breast-preserving radiotherapy. The errors of reconstruction of the implants are discussed. The consideration of errors for ISXP can be extended to other stereoscopic methods. In this case the quality considerations made by other authors have to be enlarged. The maximum reconstruction error was investigated for a given digitalization precision, focus size, and object blur by patient's movements in dependence on the deviation angle. The optimum deviation angle is about 45 degrees, depending on the importance given to the individual parts and almost without being influenced by the relation between the isocenter-film and the focus-isocenter distances. In case of an optimized deviation angle, a displacement of an implant point of 1 mm leads to a maximum reconstruction error of 2 mm. The dosage is made according to the Paris system. If the circumcircle radius of the application triangle is modified by 1 mm, a dosage modification of 14% will be the consequence in case of very short wires and a small side length. A verification in a phantom showed a positioning error below 0.5 mm. The dosage error is 2% due to the mutual compensation of the direction-isotropic reconstruction errors of the needles the number of which is between seven and nine.

Algorithms↗
PubMed1983

Neurological and neuropathological findings in familial erythrophagocytic lymphohistiocytosis.

An infant case of erythrophagocytic lymphohistiocytosis is reported. The disease began at the age of two months with hepatosplenomegaly and intractable fever, and later developed pancytopenia. Splenectomy had to be performed at the age of six months and led to the final diagnosis. After the age of nine months the patient developed progressive neurological signs (loss of visual function convulsions, opisthotonus and CSF pleocytosis). The changes in the CT-scan of the brain were explained by the neuropathologic findings after the death of the patient at the age of 13 months. The markedly atrophic brain showed diffuse and mainly perivascular infiltration of brain and meninges with lympho- and histiocytes and extensive microscopic calcification.

Atrophy↗
PubMed1980

[Myositis ossificans progressiva (M.o.p.)--a morphological and biochemical study (author's transl)].

In a two-year-old girl suffering from myositis ossificans progressiva a biopsy specimen from a soft tissue tumor was examined by electron microscopy and by collagen electrophoresis (SDS-Polyacrylamide Gel Electrophoresis). Electron microscopic findings of the biopsy specimen showed that the collagen appeared to be similar to type II collagen which can be found for example in hyaline cartilage however collagen electrophoresis revealed neither any certain signs of type II collagen nor any different proportion of type I and type III collagen compared to a healthy child.

Biopsy↗
PubMed1979

[Preliminary clinical experiences with adenine arabinoside monophosphate (ARA-AMP) in encephalitis due to viruses of the herpes group and varicella/zoster infections (author's transl)].

Adenine arabinoside monophosphate (ARA-AMP) is a new antiviral agent with significant activity against DNA viruses of the herpes group. It appears to be superior to cytosine arabinoside and iodoxuridine in severe herpes simplex infections. Unlike cytosine arabinoside and idoxuridine ARA-AMP has only minimal myelosuppressive and immunosuppressive properties. The original compound, adenine arabinoside (ARA-A) which has been used in the United States in the last years had the disadvantage of poor solubility and tissue penetrance. Compared to adenine arabinoside the monophosphate ester of this compound has the advantage of better solubility and is more slowly metabolized in humans. In eight children with virus induced encephalitis ARA-AMP was well tolerated, we could not observe any severe side effects. A case of herpes simplex encephalitis showed a complete recovery. However it has to be pointed out that in herpes simplex encephalitis ARA-AMP should be given early in the course of infection to have a beneficial effect, therefore an early diagnosis is of utmost importance. A case of generalized herpes zoster healed up within about a week. Of course these are very preliminary results which must be confirmed by further experiences.

Arabinonucleotides↗
PubMed1978

[The virostatic effect of adenine-arabinoside monophosphate. Experimental findings and preliminary clinical experiences].

Adenine arabinoside (Ara-A), a synthetic nucleoside, is an antiviral agent, which is effective against poxviruses and viruses of the herpes group. The monophosphate (Ara-AMP) has the great advantage of better solubility, compared to the parent compound. Experimental studies show the outstanding effect of Ara-AMP on the encephalitis by vaccinia-virus in white mice. Even after immunesuppression by total body irradiation, the survival rate of the Ara-AMP treated animals was significantly higher compared to the untreated controls. In experimental vaccinia-virus infections in rabbits, who had undergone total body irradiation. Ara-AMP has a favourable influence upon the course of the disease and the prognosis. Some clinical observations in children with immunesuppression, who suffered from generalized zoster of varicella-infections, are reported. Furthermore in cases of viral encephalitis Ara-AMP was successful. Controlled studies of a greater number of patients on the therapeutic value of Ara-AMP in infections with DNS-viruses are needed.

Adenosine Monophosphate↗
PubMed1977

[Tertiary malaria with acute lung edema in a Turkish child].

In the past 10-15 years there has been a continuous increase of imported cases of malaria in the Federal Republic of Germany. The case of a two-year-old child of a Turkish foreign worker with severe tertian malaria complicated by pulmonary edema is described. In general tertian malaria is rarely fatal to adults, but in children the primary attack can be life threatening.

Blood Transfusion↗