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PubMed1977

[Dosimetry of negative pi-mesons (author's transl)].

Central axis depth-dose curves, isodose curves, and size of beam spot at various depth were measured in a water phantom at a pi- -beam suitable for radiobiological and radiotherapeutical experiments. Problems of measurement of the absorbed dose in the peak region of the depth dose cure are discussed.

Animals↗
PubMed1977

Effects of low-dose irradiation with x-rays and pi-mesons on embryos of two different mouse strains.

The effects of two different kinds of radiation (X-rays and negative pions) on embryonic development of mice was examined. The application of a known radiosensitizer (lucanthone) combined with 13.5 rd whole-body irradiation on day 8 of gestation showed enhanced teratogenic action compared to treatment with each of the agents alone. The extent of intensification varied both with mouse strain and treatment, indicating possible differences in repair capacity and LET-dependency of sensitization effects. Strain differences were found in the incidence and type of chemical and radiation-induced malformations, which may be explained by different developmental stages at the time of treatment.

Animals↗
PubMed1978

[Dose distribution of photons and neutrons outside of the irradiation field of a 8-mev linear accelerator (author's transl)].

During the irradiation with a continuous radiation of 8 MeV by the linear accelerator LINAC SL 75/10, the dose distribution of photons and neutrons was measured outside of the irradiation field. The dose distribution of photons was mostly determined by thermoluminescence dose meters. There was a significant maximum of leak radiation on the back of the emitter head which showed a dose rate amounting to 7,5% of the dose rate of the central ray. Whereas the leak radiation on the patients' table was less than 0,1% of the dose of the central ray, the dose of scattered radiation emitted by the patient still amounts to 2% of the central ray dose in a distance of 15 cm from the field edge. The isodoses measured in the room demonstrate above all the importance of the lock for a sufficient radioprotection.--The dose rate of the neutrons formed in the shielding material by photonuclear reactions were measured mostly with uranium fission-track dosimeters. The highest equivalent dose rate was found on the back of the emitter head; it is about 17 rem/h. The maximum value of the equivalent dose rate of neutrons on the patient's table amounts to 1,4 rem/h and is almost independent of the size of the diaphragm. The isodoses in the room depend largely on the shape of the irradiation room; they confirm the existence of a sufficient radioprotection.

Elementary Particles↗
PubMed1998

Co-cultivation of conjunctival epithelial cells and Chlamydia trachomatis: electron microscopic findings.

This study used primary culture of rabbit conjunctival epithelial cells to investigate the infection process of chlamydia. The epithelial cells isolated from conjunctiva of rabbit were initially cultured for three weeks. After attaining confluence they were infected with Chlamydia trachomatis (C. trachomatis) serotype D, and after co-cultivation for 24, 48, and 96 hours, electron microscopic study was performed. An inclusion body, a characteristic finding of chlamydial infection, was observed in the vicinity of the nucleus after 24 hours of co-cultivation. It contained a large number of elementary and reticulate bodies and their intermediate forms. Infectious particles known as elementary bodies were noted in the inclusion as 20 to 30 microns sized round bodies with an electron dense core. Reticulate bodies were also noted; they too were round but somewhat pleomorphic and larger than elementary bodies. Some reticulate bodies multiplied actively by means of binary fission. In this study, we observed the characteristic changes of C. trachomatis-infected cells; this in-vitro system might provide a suitable model for the study of some aspects of the pathogenesis of ocular chlamydia infection.

Animals↗
PubMed1998

Studies of persistent infection by Chlamydia trachomatis serovar K in TPA-differentiated U937 cells and the role of IFN-gamma.

Inoculation of phorbol ester-differentiated U937 cells as a model for human macrophages with Chlamydia trachomatis of the urogenital serovar K resulted in a persistent infection, with maximal growth at day 7, until day 10 post-infection. At these times inclusion bodies were present in 0.5-2% of the cells. Typical inclusion bodies containing elementary bodies and reticulate bodies were observed by electron microscopy. Furthermore, single chlamydial particles resembling atypical elementary or intermediate bodies were identified in the cytoplasm in > 80% of the host cells. IFN-gamma exerts antichlamydial activity in epithelial and fibroblastoid cells, but the infection of U937 cells by C. trachomatis was not affected by IFN-gamma. The activity of the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) was not detected in untreated or in IFN-gamma-treated or chlamydiae-infected or mock-infected U937 cells. The presence of atypical persisting chlamydiae and the lack of IDO expression in U937 cells indicates that the development of these atypical bacteria is independent from IFN-gamma-mediated tryptophan deprivation and other IFN-gamma-mediated effects. Evaluation of persistently infected cells revealed that the expression of the chlamydial major outer-membrane protein, heat-shock protein (hsp60) and lipopolysaccharide (LPS) antigens was not significantly altered in the course of the culture. An intense staining of the LPS on the surface of the host cells was demonstrated by immunofluorescence. The data show that phorbol ester-differentiated U937 cells restrict chlamydial growth strongly but not completely through a mechanism distinct from IDO-mediated tryptophan deprivation. The mechanisms of persistence of chlamydiae in monocytes, which differ considerably from those described for other cells, require further investigation.

Antigens, Bacterial↗