Blunting effect of hypoxia on the proliferation and differentiation of human primary and rat L6 myoblasts is not counteracted by Epo.

OBJECTIVES: The aim of this study was to evaluate whether hypoxia and/or erythropoietin would be able to modulate proliferation/differentiation processes of rat and human myoblasts. MATERIALS AND METHODS: Rat L6 and primary human myoblasts were grown in 21% or 1% O(2) in the presence or absence of recombinant human erythropoietin (RhEpo). Presence of erythropoietin receptors (EpoR) was assayed using RT-PCR and Western blotting techniques. Cell proliferation was evaluated by determining the doubling time and kinetics of cultures by counting cells. Cell differentiation was analysed by determining myogenic fusion index using antibodies against the myosin heavy chain. Expression of myogenin and myosin heavy chain (MHC) proteins were evaluated using the Western blotting technique. RESULTS: After 96 h culture in growth medium for 2.5 and 9 h, doubling time of L6 and human primary myoblasts respectively, had increased in 1% O(2) conditions (P < 0.01). Kinetics of culture showed alteration in proliferation at 72 h in L6 myoblast cultures and at 4 days in human primary myoblasts. The myogenic fusion index had reduced by 30% in L6 myoblasts and by 20% in human myoblasts (P < 0.01). Expression of myogenin and MHC had reduced by around 50%. Despite presence of EpoR mRNA and protein, RhEpo did not counteract the effects of hypoxia either in L6 cells or in human myoblasts. CONCLUSIONS: The data show that exposure to hypoxic conditions (1% O(2)) of rat and human myoblasts altered their proliferation and differentiation processes. They also show that Epo is not an efficient growth factor to counteract this deleterious effect.

[Video technology and the personal computer in the therapy simulator]. / Videotechnik und Personalcomputer am Therapiesimulator.

PURPOSE: Technical progress in the development of radiation therapy simulators provided valuable addition of electronically stored images and monitor indicators for individual radiation parameters. One can store as well as print these data as a treatment plan. The possibility of supplementing older simulators with these technical options will be reported in the following paper. METHODS: The modification of our simulator installation was done simply. The new equipment needed to expand our simulator facility was almost exclusively derived from the fields of entertainment and home electronics (Visualizer/video camera, video tape recorder, video mixer, additional monitor; personal computer and printer). RESULTS: With these modifications we reached the technical standards of the latest simulator generation. In addition, we succeeded in implementing additional technical options: e.g. image inversion with contrast alignment to diagnostic displays, complete magnetic tape recording of the entire x-ray process with possible repetition, electronic overlapping of the simulator image and the diagnostic image (e.g. NMR; angiograms) to determine the treatment volume, automation in x-ray documentation. CONCLUSION: Increased precision and rational work steps employing readily available equipment will lead to further improvement in the quality of radiotherapy.

Solid phantom material for the dosimetry of iodine-125 seed ophthalmic plaques.

PURPOSE: A tissue-equivalent solid phantom material, RE-1, closely simulating the radiological attenuation and scattering properties of the human eye for the iodine-125 photon spectrum and their Compton-scattered secondary photons, was fabricated on a polyethylene base with CaCO3 and MgO as inorganic additives. METHODS AND MATERIALS: A 24 mm diameter spherical phantom was made from 1.1 mm thick sheets of RE-1, and holes were drilled in which 1 mm3 TLD cubes were placed. RESULTS: The radial dose function g(r), which determines the dose profile on the transverse axis, was measured in a quasi-infinite phantom of RE-1. CONCLUSION: The values obtained deviate only slightly from those for a quasi-infinite phantom made from water-equivalent material.

Autoradiography for iodine-125 seeds.

To study the interior design of model 6702 and 6711 iodine-125 seeds contact autoradiographs were performed using mammography film. Improved resolution was obtained using a pin-hole camera with a hole of 0.1 mm x 0.1 mm. With these techniques, qualitative determination of the relative activity distribution within each seed was possible. The number of the activated resin spheres and the positions of the centers of these spheres can be exactly determined. A model calculation shows, that variations in the arrangement of the activated spheres within a seed have a moderate influence on the dose distribution at source distances below 10 mm. Knowing the exact source configuration may be useful when comparing dose calculations with measured data for model 6702 125I seeds which are currently employed in ophthalmic plaque and implant therapy of other tumors.

Calcification of the aortic wall in hypercalcemic rabbits.

The mineralization process was investigated in the aortic wall of hypercalcemic rabbits. The elevated calcium level in serum was induced by intramuscular injection of vitamin D3. The animals were killed at different times of the experiment (max. 246 d). The freeze-dried tissue homogenates were used for elemental composition studies by means of proton induced X-ray emission (PIXE) and atomic absorption spectroscopy. The structural information was obtained from infrared (IR) and X-ray diffraction (XRD) spectra. Moreover, the ascending part of the aortic arch was separated and used for micro-PIXE (PIXE in combination with proton microprobe) and histochemical examinations. It was found that hypercalcemia (blood serum Ca content elevated by about 20%) induced calcification of the aortic wall. The mineral phase within the aortic wall consisted of Ca-P salts. The Ca/P ratio continuously increased during the experiment and approached 2 after 246 d of the vitamin D3 treatment. The IR and XRD studies made possible the identification of the complex phase composition of the samples. The hydroxyapatite crystals were detected after 196 days, however, in earlier phases of the experiment, amorphous calcium phosphate, dicalcium phosphate dihydrate and octacalcium phosphate were also observed. On the basis of the data obtained, the mechanism of the precipitation and growth of inorganic deposits in the tunica media of the aortic wall was discussed.

Intramembranaceous ossification analyses by a proton microprobe.

The proton induced X-ray emission method in combination with a proton microprobe was applied to study the intramembranaceous ossification. As material sections of mouse embryo skulls from the 17th and 19th day of gestation were used. The morphology of the sample was examined by routine histochemical procedure performed on the sections adjacent to that irradiated by the proton microprobe. The measurements were made in line scan and raster scan mode. The concentrations of P, S, Cl, K, Ca, Fe and Zn were determined at each irradiated point. The average element concentrations were calculated for four parts of each section (bone, cartilage, mesenchymal tissue close to the bone and mesenchymal tissue in other places). The distributions of Ca and P (less markedly than Ca) concentrations almost exclusively correlate with localization of the bone while S, Cl and K concentrations show preference to the cartilage. The amount of inorganic material in flat bones of the 17-day embryo amounts to 14% of the dry mass. The material is characterized by a Ca/P ratio of about 1.6. In the embryo 2 days older the amount of the inorganic phase is practically the same (15%) while the Ca/P ratio approaches 2. This suggests the presence of the precursor phase in the flat bone calcification. It is possible that octacalcium phosphate (Ca/P ratio equals to 1.72) is formed at the onset of the flat bone mineralization which transforms rapidly (in 2 days) to a more stable mineral (defective hydroxyapatite).