Morphological transformation of C3H/M2 mouse fibroblasts by, and genotoxicity of, extracts of human milk

Breast cancer may be initiated by environmental/dietary agents and human milk may act as an ex vivo indicator of in vivo exposure of mammary epithelial cells to genotoxins. Extracts of human milk from UK-resident women (n=7) were tested for their abilities to morphologically transform C3H/M2 mouse fibroblasts. Genotoxicities were assessed in the Salmonella typhimurium reverse-mutation assay in the presence of S9 using strains TA1538 and YG1019, and in metabolically-competent human MCL-5 cells with the micronucleus and with the alkaline single cell gel electrophoresis (comet) assays. Two of the seven extracts were inactive in the transformation assay both in the presence or absence of S9, two appeared to be equally transforming either in the presence or absence of S9, and two other extracts induced increased transformation frequencies in the presence of S9. A seventh extract, tested only in the absence of S9, was inactive. Extracts were either active or inactive in at least three of the four tests applied. Four extracts were active or inactive in all four tests. The results suggest that human milk could be used as a resource for investigations of the as-yet-unidentified transforming agents previously detected in mammary lipid.     

HPLC separation of 32P-postlabelled DNA adducts formed from dibenz[a,h]anthracene in skin.

Mouse skin and human skin have been treated in vivo or in short-term organ culture with dibenz[a,h]anthracene (DB[a,h]A), the related 3,4- or 5,6-diols or the anti- or syn-3,4-diol 1,2-oxides. DNA hydrolysates have been 32P-postlabelled and the adducts present examined by HPLC using a phenyl-modified reverse phase column and, for comparison, by PEI-cellulose TLC and autoradiography. The adducts formed when the diol-epoxides were reacted with salmon sperm DNA were also examined. The results show that in mouse skin treated in vivo, the major adducts formed from DB[a,h]A and the 3,4-diol were the same and that two of them were more polar than those formed in skin or in DNA that had been treated with the related anti- or syn-diol epoxides. Human skin treated with DB[a,h]A in culture yielded an adduct profile that was qualitatively similar to the profiles obtained with mouse skin.     

Identified taste bud cell proliferation in the perihatching chick [published erratum appears in Chem Senses 1998 Aug;23(4):459]

Developing taste buds in the anterior mandibular floor of perihatching chicks were studied by high voltage electron microscopic autoradiography in order to identify proliferating gemmal cell types. Montaged profiles of 29 taste buds in five cases euthanized between embryonic day 21 and posthatching day 2 were analyzed after a single [3H]thymidine injection administered on embryonic day 16, 17 or 18. Results showed that dark cells comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568 cells) gemmal cells as compared with light, intermediate, basal or perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of labeled cells and a greater amount of label (grains/nucleus) than the other four bud cell types, irrespective of injection day. The nuclear area (micron 2) of dark cells was not significantly larger (P > 0.05) than that of the other gemmal cell types and therefore cannot account for the greater amount for label in the dark cells. Interestingly, only dark cells showed a positive correlation (P < 0.003) between amount of label and nuclear area. Results suggest that, during the perihatching period of robust cell proliferation, dividing dark cells may give rise primarily, but not exclusively, to dark cell progeny.      

Action of ultraviolet-C on stilbene formation in callus ofArachis hypogaea

The action of light on the formation of stilbenes and the induction of stilbene synthase in dark-grown and light-grown callus of peanut (Arachis hypogaea) was investigated over the wavelength range from 250 to 400 nm. Ultraviolet light of 260–270 nm had a significant and selective effect on the formation of resveratrol and isopentenylresveratrol. The callus responded by the production of stilbene synthase, with maximal activity appearing 4 h after irradiation with a fluence rate of 1 W m^-2 (270 nm) applied for 10 min. At lower fluence rates, maximal responses in enzyme activity were shifted to longer induction periods. The efficiency of the biosynthetic pathway, and the form and maxima of enzyme profiles depended on the duration of exposure. We failed to demonstrate any significant influence of red light at low energy irradiation (672 nm, 726 nm and 753 nm).     

DNA adducts in marine and freshwater fish as biomarkers of environmental contamination

The analysis of DNA modifications in aquatic animals may serve as a sensitive marker of exposure to genotoxic contaminants. This is of importance in assessing water quality regarding pollution with genotoxic compounds, food safety analysing edible aquatic animals and in terms of ecotoxicology. Covalent modification of DNA is considered a crucial event in chemical carcinogenesis and thus may be considered a biomarker of an early genotoxic effect. Measuring DNA adducts is unique in that these lesions may be considered a biomarker of both exposure and effect. A number of studies have described the analysis of the DNA isolated from the liver of both freshwater and marine fish. Considerable levels of DNA adducts have been observed in some animals from contaminated lakes or rivers. Low levels were observed in DNA from the liver of marine fish. The background levels of DNA adducts have to be determined in animals from appropriate uncontaminated control sites that are matched for species, gender, age and season of the year. It is of crucial importance to consider the species analysed since there have been reports of the non responsiveness of some species.     

Photoinhibition of Photosynthetic Oxygen Production and its Recovery in the Subtidal Red Alga Polyneura hilliae

In the marine red alga Polyneura hilliae photoinhibition of photosynthesis was investigated by measuring the photosynthetic oxygen production. The extent of photoinhibition in this alga depends on the fluence rate as well as on the time of exposure. Strongly photoinhibited algae recover slowly. Full recovery is reached only in weak light after 3 days. Two phases of recovery can be distinguished: a first relatively fast phase of recovery that is independent of light, and a second slow phase which begins after about 6 hours and requires weak light. Consequently, even in complete darkness partial recovery is observed. An action spectrum of photoinhibition and its comparison with the in vivo absorption spectrum of Polyneura demonstrates that photoinhibition is mainly caused by light which is absorbed by phycobiliproteins, chlorophyll a and carotenoids. This fact and the ineffectiveness of light above 686 nm clearly indicate that the main photoinhibition site in this alga is PS II. No photosynthetic oxygen production is detectable after 3 h irradiation at 402 nm, 150 μmol quanta m^?2s^?1. As photosynthetic activity recovers slowly and to a limited extent, the suppression of oxygen production is apparently only in part the result of photoinhibition sensu strictu and in part due to permanent photodamage.