Suitability of human chromosome-specific DNA libraries for mutagenicity studies in Macaca fascicularis.

The development and use of chromosome-specific DNA probes to label entire human chromosomes has been an important advance in molecular cytogenetics. Fluorescence in situ hybridization using whole chromosome-specific DNA probes has been used to study both numerical and structural chromosomal aberrations in many human cell types. It would be useful if this technology could be applied to other animal species. However, whole chromosome-specific DNA probes have been reported for only human chromosomes. In this study, experiments were conducted to determine whether human probes could be used to label chromosomes of the cynomolgus monkey, Macaca fascicularis. The results demonstrate that some human DNA probes are suitable for the study of chromosomal aberrations in the monkey. Monkey chromosomes 1 and 4 labelled with human DNA probes had a strong, chromosome-specific labelling pattern. The probe for human chromosome 21 labelled the short arm on the monkey chromosome 2 and the probe for human chromosome 2 could not be detected on any of the monkey chromosomes.

Mutagenic activity of p-toluenesulfonhydrazide.

Toluenesulfonhydrazide (TSH) is a high volume production chemical for which there is relatively little toxicological data. In this study, the mutagenic activity of TSH was determined in the Salmonella/mammalian microsome assay and the in vitro chromosomal aberration assay using Chinese hamster ovary cells. TSH induced gene mutations both with and without metabolic activation in the Salmonella/mammalian microsome assay but that it did not induce chromosomal aberrations in Chinese hamster ovary cells. The results of this study indicate that TSH is an in vitro mutagen and should be assessed for in vivo mutagenicity.

Induction of chromosomal aberrations in Chinese hamster ovary cells by triethyllead acetate.

Organolead compounds enter the environment primarily through the combustion of leaded gasoline and industrial discharge. Lead and lead-containing compounds have been shown to induce a broad spectrum of toxic effects, including hematopoietic, renal, neurologic, and carcinogenic effects. In this study, the mutagenic activity of triethyllead acetate (Et3PbAc) was determined by measuring the induction of chromosomal aberrations in Chinese hamster ovary cells. The results indicate that Et3PbAc is very cytotoxic and a potent clastogen. In preliminary cytotoxicity studies used to determine appropriate test concentrations for chromosomal aberration analysis, the LC50 of Et3PbAc was approximately 10 microM in the absence of metabolic activation, and 80 microM in the presence of metabolic activation. The maximal response was greater with metabolic activation than without. However, a much higher dose was required to elicit a significant response in the presence of metabolic activation than in its absence.

The effect of the source of inorganic nitrogen on growth and enzymes of nitrogen assimilation in soybean and wheat cells in suspension cultures.

Soybean (Glycine max L. cv. Mandarin) and wheat (Triticum monococcum L.) cells were grown in media with NO3 (-) plus NH4 (+) (B5) and NO3 (-) without NH4 (+) (B5-NH4) as nitrogen sources. Changes in pH, [NO3 (-)] and [NH4 (+)] in media, and dry weight, protein content, nitrate reductase (NR) and glutamate dehydrogenase (GDH) in the cells were followed for about 170 h. With both NH4 (+) and NO3 (-) in the medium, NH4 (+) was utilized very quickly. Soybean cells grew poorly in the absence of NH4 (+) while wheat cells grew equally well on media with or without NH4 (+). When soybean cells were grown in medium with NO3 (-) plus NH4 (+), dry weight and NR activity remained relatively low for several hours after which both increased rapidly. This coincided with the time NH4 (+) was depleted from the medium. In the absence of NH4 (+), soybean cell growth and NR activity remained low. NR activity in wheat cells, and GDH activity in soybean and wheat cells, did not vary significantly in the presence or absence of NH4 (+).

The ability of amino compounds and conditioned medium to alleviate the reduced nitrogen requirement of soybean cells grown in suspension cultures.

Various nitrogen compounds were tested for their ability to alleviate the reduced nitrogen requirement of soybean cells growing in defined liquid medium containing nitrate as the alternative nitrogen source. Either L-glutamine, L-alanine, putrescine or NH4 (+) satisfied this requirement. Addition of L-glutamate resulted in poor growth. Where growth was stimulated, nitrate reductase (NR) activity increased whereas glutamate dehydrogenase activity in the cells showed no such correlation. In all fresh media which supported rapid growth, NR activity first decreased rapidly to a low value. Subsequent dry weight increases occurred concommitantly with an increase in NR activity. When 2,4-dichlorophenoxyacetic acid was omitted from the medium the growth was slow and the NR activity did not increase. During the first 40 h of incubation in medium containing NH4 (+) plus NO3 (-) the cells produced a growth-enhancing factor(s). This factor(s) was present in the cells and in the medium and eliminated the requirement for reduced nitrogen.