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Biomedical subjects

K Bonk

Publications and source records attributed to K Bonk.

6 recordsLinked to original sources
PubMed1996

Do DNA double-strand breaks induced by Alu I lead to development of novel aberrations in the second and third post-treatment mitoses?

Several authors have reported that ionizing radiation can give rise to novel aberrations several mitotic divisions after the exposure. At our institute this phenomenon has been observed in mouse preimplantation embryos. This cell system is uniquely well suited for such investigations because the first three cell divisions show a high degree of synchrony. Thus the expression of chromosomal aberrations at the first, second and third mitosis after irradiation can be scored unambiguously. To investigate whether DNA double-strand breaks may be the lesions responsible for the delayed expression of chromosomal aberrations, we have studied the frequencies of aberrations in the first, second and third mitosis after treatment of one-cell mouse embryos with the restriction enzyme Alu I. Embryos were permeabilized with Streptolysin-O. The results indicate that the induction of double-strand breaks does not lead to novel aberrations in the third post-treatment mitosis. Several embryos scored at the second mitosis showed very high numbers of aberrations, indicating that Alu I may remain active in the cells for a period of one cell cycle. After treatment with Streptolysin-O alone, enhanced aberration frequencies were observed in the third post-treatment mitosis, suggesting that membrane damage has a delayed effect on the cellular integrity.

Animals↗
PubMed1993

Is there an adaptive response in spleen lymphocytes of C57B1/6 mice as assessed by chromosomal aberrations?

In previous publications we have shown that no adaptive response could be induced in preimplantation embryos and spleen lymphocytes of Heiligenberger mice, a strain inbred at our institute (Wojcik et al., Int. J. Radiat. Biol. 62, 177-186, 1992; Müller et al., Int. J. Radiat. Biol. 62, 169-175, 1992). Because of data indicating that some humans may be genetically deficient in the ability to express an adaptive response, we have speculated that the cells of the Heiligenberger strain may lack an adaptive response. To check this, experiments have been done with spleen lymphocytes of the C57B1/6 mice. Initial results indicated the presence of an adaptive response in some individual C57B1/6 mice. However, an analysis of aberration scores of parallel lymphocyte cultures revealed a high intraindividual variability, indicating that the adaptive response observed initially was a reflection of this variability rather than of induced radiation resistance. This conclusion is confirmed further by the lack of such variability in parallel cultures of lymphocytes from Heiligenberger mice.

Adaptation, Physiological↗
PubMed1992

Absence of adaptive response to low doses of X-rays in preimplantation embryos and spleen lymphocytes of an inbred mouse strain as compared to human peripheral lymphocytes: a cytogenetic study.

The adaptive response was studied in preimplantation embryos and spleen lymphocytes of a mouse inbred strain and in peripheral lymphocytes of three human donors, using chromosomal aberrations as the endpoint. Embryos were adapted to 0.05 Gy X-ray 50 h post-conception either in vitro or in vivo and challenged 6 h later. Chromosome aberrations of the 8----16 cell stage mitoses were scored. No adaptive response was seen in the embryos. Of 14 female mice studied, an adaptive response was seen in spleen lymphocytes of only one mouse. However, because variable chromosomal aberration levels were observed in lymphocytes of different donors, it is concluded that the adaptive response detected was merely a result of this heterogeneity. In human peripheral lymphocytes an adaptive response was seen in all three donors. It is speculated that the inbred mouse strain used is deficient in the adaptive response.

Adaptation, Physiological↗
PubMed1983

Sialoadenoma papilliferum.

2 additional examples of sialoadenoma papilliferum, one occurring in the palate of a 32-year-old woman and the other in the palate of a 43-year-old man, have been added to the previously reported 11 cases. 9 of the 13 reported cases occurred in the palate with a 5.5:1 prevalence in men. The age at discovery ranged from 32 to 77 years. Whether these lesions represent a benign salivary gland tumor or hyperplasia of duct epithelium remains debatable. Surgical excision apparently effects a cure as no recurrences have been reported.

Adenoma↗
PubMed1976

Repair of the injured renal papillary tissue in rats.

Renal papillary necrosis was produced in rats by administration of 2-bromoethylamine hydrobromide. The rats drank either 0.9 per cent sodium chloride solution or distilled water, and structural restoration of renal papilla and effect on urine-concentrating ability were examined. All rats drinking distilled water had no evidence of structural restoration of the injured papilla and no significant improvement of urine-concentrating ability. When rats started drinking 0.9 per cent sodium chloride solution shortly after indution of the necrosis, enhanced cellular reconstitution of the necrosed papillary tissue and partial restoration of urine-concentrating ability occurred in a significant number of rats. The most successful structural reparation was the collecting tubules, followed by the thin loops of Henle and the capillaries. Repopulation of the interstitial cells was the least successful. In conclusion, repair of necrosed renal papilla was enhanced when rats drank 0.9 per cent sodium chloride solution starting shortly after injection of renal papilla-necrotizing dose of 2-bromoethylamine hydrobromide.

Animals↗