PubMed Health⌕ Search

Biomedical subjects

E Wawra

Publications and source records attributed to E Wawra.

26 records · Page 2Linked to original sources
PubMed1981

Effect of sodium butyrate on induction of cellular and viral DNA syntheses in polyoma virus-infected mouse kidney cells.

Sodium butyrate inhibited initiation of viral and cellular DNA replication in polyoma virus-infected mouse kidney cells. Ongoing viral or cellular DNA replication, however, was not affected by the presence of the substance. Butyrate had no effect on T-antigen synthesis and on the stimulation of transcription, one of the earliest reactions of the infected cells to the appearance of T-antigen, nor did it inhibit expression of late viral genes (synthesis of viral capsid proteins). In addition to blocking the onset of DNA synthesis, butyrate also inhibited stimulation of the activities of enzymes involved in DNA synthesis. When butyrate was removed, viral and cellular DNA syntheses were induced in parallel after a lag period of approximately 4 h. At the same time, the activities of enzymes involved in DNA synthesis increase. If protein synthesis was inhibited during part of the lag period, the initiation of DNA synthesis was retarded for the same time interval, suggesting that the proteins involved in the initiation of DNA replication had to be made. We have developed an in vitro system for measuring DNA synthesis in crude nuclear preparations which mimics the status of DNA replication in intact cells and may help in future experiments to study the requirements for initiation of cellular and viral DNA synthesis and the possible involvement of T-antigens in this reaction.

Animals↗
PubMed1979

Evidences for the function of DNA polymerase-beta in unscheduled DNA synthesis.

The activities of DNA polymerase-alpha and -beta isolated from pig spleen were determined at different temperatures and in the presence of different concentrations of inhibitors. The results were compared with parallel estimations of replicative DNA synthesis and UV-induced repair synthesis in spleen cells. In respect to pCMB and aCTP, polymerase-alpha is more sensitive than polymerase-beta and similarly is replication more sensitive than repair. Repair synthesis and the activity of polymerase-beta decreases at temperatures higher than 40 degrees C whereas both replication and the activity of polymerase-alpha are greatly stimulated at elevated temperatures with optima of 45 degrees C (polymerase-alpha) and 41 degrees C (replication). The results favour the hypothesis that polymerase-beta is involved in repair synthesis.

Animals↗
PubMed1979

[The action of hyperthermia on DNA repair (author's transl)].

The time-course of DNA repair after gamma irradiation was measured in HeLa cells at various temperatures. Unscheduled DNA synthesis was estimated by incorporation of 3H-thymidine in presence of hydroxyurea. To detect the ligase reaction, the number of single strand breaks (SSB) was determined by centrifugation in alcaline sucrose as well as by hydroxylapatite chromatography after partial denaturation. In addition, the temperature dependence of DNA polymerase and DNase reaction in cell-free systems were measured. These data were compared with the reduction of colony-forming ability of the cells caused by gamma irradiation and following repair at various temperatures. All steps of repair proceed faster at 41--43 degrees than at 37 degrees but cells are most resistant to gamma irradiation at 37 degrees. We therefore assume that the DNA repair process at 42 degrees is faster but more error prone than at 37 degrees.

Colony-Forming Units Assay↗
PubMed1978

[Passive smoking at the workplace--injurious to health? (author's transl)].

The question as to whether passive smoking at the workplace is injurious to health is dealt with. With the aid of the bibliographic standard literature on industrial, social and preventive medicine, all experimental investigations of this subject and published since 1970 were considered. The important results and findings are presented in tabulated surveys broken down by the substances contained in smoke. The present results of investigation are discussed with respect to a practical workplace model whose air-hygienic conditions are determined by legal prescriptions for workplaces. The measured concentrations of the particulate mass and of the most important individual constituents of smoke, carbon monoxide, nicotine and aldehyde make it highly unlikely that passive smoking at the workplace causes injury to health if the prevailing regulations governing the workplace are complied with. Particular attention has to be given to the occupational problems existing in night bars, restaurants and discothecs.

Air Pollutants, Occupational↗
PubMed1977

Autoradiographic in vitro studies on diurnal variation in human epidermal cell proliferation.

Five men with healthy skin ranging in age from 24 to 37 years were investigated for the presence of diurnal variation in epidermal cell proliferation by the in vitro 3H-thymidine labeling technique. The following parameters were studied: The basal cell LI; the numbers of labeled basas and supra-basal cell nuclei as well as the total number of labeled nuclei situated above a basal membrane length of 100 mum. All autoradiographic parameters showed marked diurnal variations, the amplitudes of which differed individually. The basal 3H labeling index always showed the highest diurnal variation. In all patients diurnal variations of the basal and suprabasal cell proliferation occurred simultaneously and in equal direction. However, each test person showed maxima and minima of epidermal DNA synthesis at different times. No synchronism could be found when comparing the individual variations of cell proliferation. Several possible reasons for the asynchronous in vitro behaviour of epidermal cells will be discussed.

Adult↗