Background Early marriage is not uncommon in Ethiopia, particularly for adolescent girls in rural settings. Social norms are among the factors believed to perpetuate early marriage practices. This qualitative study explores social norms surrounding adolescent girls’ marriage practices in West Hararghe, Ethiopia. Methods This study used the qualitative inquiry method to explore social norms in rural Ethiopia. Focus group discussions were conducted with purposively sampled married and unmarried adolescent girls, adolescent boys, and parents. A total of 158 individuals participated in the study, comprising 95 adolescents and 63 parents. Data were collected using locally developed vignettes. A thematic framework analysis approach using the Social Norms Analysis Plot (SNAP) was employed to diagnose and understand social norms. Results Adolescent girls’ marriage was found to be mainly influenced by their peers who conform to prevailing social norms. Marrying one’s first suitor was considered an opportunity not to be missed and a symbol of good luck. Relatives, neighbors, and marriage brokers facilitate adolescent girls’ marriage in accordance with the local social norms. Girls usually accept the first marriage proposal regardless of their age, and they are highly expected to do so by their peers, parents, and influential others. Exceptions from the early marriage social norm include adolescent girls determined to continue their education and those having supportive teachers. Conclusions In this study context, social norms strongly encourage early marriage and are mainly perpetuated by peers of adolescent girls and influential adults. A strong determination to continue education on the part of girls, strong school performance, and supportive schoolteachers are important conditions for circumventing social norms on early marriage. As social norms evolve slowly, we recommend periodical assessment in order to develop locally appropriate interventions against early marriage.

We report the results of a collaborative study aimed at developing reliable, direct assays for mutation in human cells. The project used common lymphoblastoid cell lines, both with and without mutagen treatment, as a shared resource to validate the development of new molecular methods for the detection of low-level mutations in the presence of a large excess of normal alleles. As the "gold standard, " hprt mutation frequencies were also measured on the same samples. The methods under development included i) the restriction site mutation (RSM) assay, in which mutations lead to the destruction of a restriction site; ii) minisatellite length-change mutation, in which mutations lead to alleles containing new numbers of tandem repeat units; iii) loss of heterozygosity for HLA epitopes, in which antibodies can be used to direct selection for mutant cells; iv) multiple fluorescence-based long linker arm nucleotides assay (mf-LLA) technology, for the detection of substitutional mutations; v) detection of alterations in the TP53 locus using a (CA) array as the target for the screening; and vi) PCR analysis of lymphocytes for the presence of the BCL2 t(14:18) translocation. The relative merits of these molecular methods are discussed, and a comparison made with more "traditional" methods.

Cells from individuals with Cockayne syndrome (CS) are hypersensitive to the lethal effects of ultraviolet light (uv) and show a number of abnormal biochemical responses following uv-irradiation. Fujiwara et al. recently reported that the NAD contents of CS fibroblasts were lower than those of normal fibroblasts, and that addition of NAD to the cellular growth medium rectified most of the abnormal responses of CS cells to uv-irradiation. In our experiments, however, the cellular NAD contents of normal and CS fibroblasts were similar, and addition of NAD to the growth medium had no effect on the hypersensitivity of CS cells to uv-irradiation, nor did it restore the inability of CS cells to recover normal rates of DNA or RNA synthesis following uv-irradiation.

Following treatment of human fibroblasts with dimethyl-sulphate, more breaks persisted in DNA in cells incubated with 3-aminobenzamide, an inhibitor of ADP-ribosyltransferase, than in its absence. This effect of 3-aminobenzamide was more pronounced in non-dividing than in dividing cells. If non-dividing cells were treated with dimethylsulphate and then incubated for a few hours in the absence of 3-aminobenzamide, few breaks were detectable in the DNA. Subsequent addition of 3-aminobenzamide resulted in the reappearance of many breaks in the DNA. These data suggest that continued synthesis of poly(ADP-ribose) reduces the steady state level of breaks during excision repair of alkylation damage. This is probably mediated by the stimulation of DNA ligase activity. Inhibition of poly(ADP-ribose) synthesis with 3-aminobenzamide maintains or restores a higher steady-state level of breaks.

The fibroblast cell strain 46BR, derived from an immunodeficient individual, is hypersensitive to the lethal effects of a variety of DNA-damaging agents, this effect being particularly marked for monofunctional methylating agents. After u.v. irradiation 46BR cells show normal unscheduled DNA synthesis, daughter strand repair, and recovery of DNA and RNA synthesis. The inhibition of DNA replicative synthesis by u.v. is slightly less than that of normal cells. After gamma-irradiation the rejoining of strand breaks is normal as are the kinetics of replicative DNA synthesis. Following treatment with dimethylsulphate, replicative DNA synthesis is affected in a similar way to normal cells, unscheduled DNA synthesis may be increased relative to normal cells, but more strand breaks persist in 46BR than in normal cells. In addition 46BR cells are hypersensitive to the toxic effects of 3-aminobenzamide, an inhibitor of ADP-ribosyl transferase. This enzyme is involved in the ligation step of repair of alkylation damage. A hypothesis is presented suggesting that 46BR may be defective in DNA ligase I.

Using a highly specific rabbit antiserum (E3) directed against O6-ethyldeoxyguanosine in a competitive radioimmunoassay, we have measured the kinetics of removal of this alkylation product from the DNA of human fibroblasts treated with the N-nitroso carcinogen N-ethyl-N-nitrosourea. A very similar rate of elimination from DNA was found in two normal human fibroblast strains (GM730 and 54BR) and in the nonvirus-transformed xeroderma pigmentosum fibroblast strains XP2BI and XP3BR. This is in contrast to the SV40-transformed xeroderma pigmentosum fibroblast strain XP12RO-SV40 which had previously been shown to be defective in its ability to remove O6-ethylguanine from DNA.

The size of the replicating units of the DNA from the murine lymphoma cell L5178Y has been studied by direct measurement of the size of the growing DNA strands in sucrose gradients. Cells were pulse-labelled with [3H]thymidine and then irradiated with low doses of X-rays in order to introduce a small amount of fragmentation into the DNA, thus overcoming entanglement effects. Detailed analysis of the radioactivity profiles obtained on sedimentation of the resulting labelled DNA fragments in alkaline sucrose gradients has provided information about the size of the growing DNA strands. The results suggest that most of the replicating units have a single-strand molecular weight of about 2 · 108. Sometimes a much smaller population with molecular weight of about 4 · 107 is also observed. On completion of replication the newly-synthesized strands are linked end-to-end, so that the molecular weight of the DNA strands in the G2 phase of the cell cycle is greater than 109 (i.e., larger than can be estimated by the methods available at present).

Alkaline sucrose gradients have been used to study denatured DNA from a murine lymphoma cell. The results show that the sedimentation behaviour of DNA molecules of number-average molecular weight above 1 · 108 is dependent on the speed of centrifugation. This means that this method cannot be used to measure high molecular weights. The results also cast doubt on the recent claim that a structural subunit can be isolated from the DNA of a mammalian cell (J. T. Lett, E. S. Klucis and C. Sun, Biophys. J., 10 (1970) 277; M. M. Elkind, C. Kamper, Biophys. J. 10., (1970) 237.

The production of X-ray-induced double-strand breaks in the DNA of murine lymphoma cells (L5178Y) has been measured by determining the molecular weight of the DNA from X-irradiated cells. The cells were lysed on top of neutral sucrose gradients and the molecular weight of the released DNA was measured by rate sedimentation through the gradients. Several independent criteria have been used to test whether the sedimenting DNA was pure and unaggregated and to show that the sedimentation behaviour of the DNA provided a true measure of its molecular weight. These criteria were only fulfilled if the speed of centrifugation was less than 20 000 rev./min. Using these conditions, the results show that double-strand breaks are formed in the DNA of L5178Y cells as single events with an efficiency of 2900±400 eV per break, and that after X-ray doses of more than 20 krads these breaks are not rejoined on post-irradiation incubation. Under appropriate conditions DNA molecules of molecular weight up to 2·109 sediment freely and the molecular weight of DNA from unirradiated cells is at least 3·109 and probably greater.

TSUKADA et al.1 have recently reported that, after denaturation, newly replicated DNA from regenerating rat liver cells apparently has a lower molecular weight than the main body of the chromosomal DNA. After pulse labelling with tritiated thymidine, they isolated the DNA by conventional methods, which extensively shear the DNA, thereby reducing its chain length, and then measured the molecular weight of the denatured DNA by sedimentation on an akaline sucrose gradient.