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Biomedical subjects

G Christ

Publications and source records attributed to G Christ.

At least 91 records · Page 5Linked to original sources
PubMed1987

Proliferation of a human epidermal tumor cell line stimulated by urokinase.

Several tumor cells secrete significantly increased amounts of the plasminogen activator urokinase, a trypsinlike serine protease, whose biological function in tumor biology is unclear. In this study we report that cells of the human epidermal tumor cell line CCL 20.2 express about 80,000 high-affinity urokinase receptors per cell that bind active as well as diisopropylfluorophosphate-treated high-molecular-weight (HMW) urokinase. Low-molecular-weight (LMW) urokinase is not bound to the receptor. Occupation of these receptors by active HMW urokinase stimulates cell proliferation independently in the presence of plasminogen in the culture medium. LMW urokinase has again no effect on cell proliferation. Calculated on a molar basis, this effect is about 28% of that of epidermal growth factor. Active HMW urokinase might therefore provide an autocrine receptor-mediated growth-promoting mechanism for tumor cells similar to those described for other growth factors.

Cell Division↗
PubMed1986

Monoclonal antibodies against human high molecular weight urinary urokinase: application for affinity purification of urinary prourokinase.

Monoclonal antibodies against urinary urokinase were obtained by immunizing mice with purified human high molecular weight urokinase. Five antibodies were selected and denominated MPW1UK, MPW2UK, MPW3UK, MPW4UK, and MPW5UK, respectively. All selected antibodies reacted with high and low molecular weight urokinase. Cleavage of the low molecular weight paranitroanilide substrate pyro-Glu-Gly-Arg-pNA by urokinase was not inhibited by the antibodies and only one antibody (MPW5UK) inhibited plasminogen activation by urokinase. The ability of MPW5UK to bind to coated urokinase was 100-fold higher than that of the other antibodies. MPW5UK was used to prepare an immunosorbent for the purification of urokinase antigen from freshly voided crude urine. One-chain prourokinase was separated from two-chain urokinase by chromatography of the urokinase antigen containing mixture on agmatine Sepharose. As judged by SDS gel electrophoresis one-chain prourokinase as well as two-chain urokinase were purified to apparent homogeneity by this two-step procedure; the yields were 18% and 47% for single-chain prourokinase and two-chain urokinase, respectively, as calculated from total urokinase antigen contained in the starting material.

Animals↗
PubMed1986

Description of the TBI procedure for bone-marrow transplantation at the University of Tübingen.

The TBI is performed with 8 MV X-rays of a linear accelerator. The procedure is divided into a lateral and a.p./p.a. segment with a weighting factor of 5/6 and 1/6 respectively. For the lateral segment no compensators are employed. Only the upper part of the arms are used to shield the lungs. In the a.p./p.a. segment two or three fields have to be used on account of the small FSD. Here head and neck are shielded depending on the overdosage in the lateral segment. The dose given to the lungs is limited by mantlefield-technique to 10.5 Gy. The total midline dose amounts to 12 Gy and is applicated on three days with two fractions per day.

Bone Marrow Transplantation↗
PubMed1985

[The effect of beam hardening on CT values].

The investigation has shown that the effect of beam hardening and the nature of surrounding structures must not be neglected when carrying out quantitative measurements. This is particularly true in the presence of strongly attenuating, and therefore strongly beam hardening structures such as bone, in regions where there are wide variations in CT values and when using varying kilo-voltages. Within the range of 0 to 200 HU, the effect of beam hardening is less important when compared with other statistical errors.

Calcium Chloride↗
PubMed1985

[In vivo dosimetry in whole body irradiation].

The results of measurements on an Alderson phantom, as well as in-vivo-measurements, on five patients during total body irradiation are described. They were compared with computer-predicted values using the lateral A.P./P.A. irradiation, as used in Tübingen; measurements were carried out by a TLD method. Particular attention was paid to the critical areas such as the head, the neck and the lungs. The results in general agreed to within 5% and were in good accord with international findings.

Humans↗
PubMed1985

[A method for partial or whole-body irradiation with fast electrons].

A method for the electron irradiation of the body surface is presented which can easily be applied and standardized. The patient is placed in prone and supine position on the normal irradiation table. Contrary to many other methods, this proceeding is especially comfortable for the patient.

Beta Particles↗
PubMed1984

Exact treatment of the dual-energy method in CT using polyenergetic X-ray spectra.

The theoretical background of the dual-energy method in CT is discussed in detail, especially the meaning of a measured linear attenuation coefficient of a polyenergetic X-ray spectrum in the presence of beam hardening. Using exact values for the incident spectra the iteration procedure shown here allows one to obtain the true values of the effective atomic number and electron density of an absorber material. The applicability of the method in CT is illustrated by computer simulation of the image reconstruction for a homogeneous and an inhomogeneous phantom.

Humans↗
PubMed1983

[Comparison between experimentally and theoretically determined CT values].

The article presents two methods for the theoretical determination of CT values. These methods involve relatively little work and cost and enable at least an estimation of the CT value of any object to be examined. The results are compared with the experimental data, and possible sources of errors are shown. The article concludes with a discussion of a few examples from actual practice.

Argyria↗
PubMed1983

[Weekly control measurement at the linear accelerator].

Weekly control measurements taken at the linear accelerator of the Medizinisches Strahleninstitut der Universität Tübingen are described which largely exceed those prescribed by the "Richtlinien Strahlenschutz in der Medizin" (instructions about radioprotection in medicine). Since the determination of the field homogeneity and the energy of electron and X-ray radiation is very time-consuming, a largely automatized procedure has been elaborated which is presented in this study.

Methods↗
PubMed1982

[Dosimetry of a whole-body irradiation for bone marrow transplantation].

The authors present a method allowing to dose a whole-body irradiation in such a way that a nearly homogenous dose of 10 Gy is reached in the whole patient, with the exception of the lung which shall only receive 8 Gy. Particular attention is given to the increased dose in the head and neck region caused by the smaller thickness as compared to the trunk, which is compensated by shields. The measurements were taken in a plastic phantom for all possible patient's dimensions. All necessary basic data are stored in a program which calculates the monitor preselection for the individual fields after input of the patient's dimensions. Further controls are intended in the near future by in-vivo measurements. The time necessary for the described measurements is about for to six days, and the same time has to be appended for the evaluation and establishment of the program.

Bone Marrow Transplantation↗
PubMed1978

[The use of computer tomography in individual treatment planning (author's transl)].

Computer tomography provides the possibility of individual treatment planning. For this purpose it is necessary to obtain the matrix of linear absorption coefficient for the type of radiation used during radiotherapy. In this paper it is shown that it is necessary to obtain a cross section of the patient using rays of two different qualities. From these results and previous measurements on phantoms it is possible to calculate the density and effective atomic number. It is also shown that the most significant information is obtained from the density matrix, if ultra hard X-rays are used for radiation therapy; With this density matrix it is possible in a simple manner to take account of inhomogeneities within individual patients.

Absorptiometry, Photon↗