It has been proposed that increases in the number of bacteria applied to each plate can enhance the sensitivity of the Ames S. typhimurium mutagenicity assay. These procedures have the potential to elevate the number of spontaneous revertants (SR) by increasing the contribution of pre-existing revertants (PER) present before application of the bacteria to the limited histidine test plates. We have investigated the contribution of PER when 10(9) bacteria are applied to the plates and found that the number of PER is dependent on the handling and storage of the cultures used to inoculate the overnight broth. The average number of PER/10(9) viable bacteria after overnight growth in broths inoculated from a frozen permanent, lyophilized permanent, master plate, and an isolated colony, of TA98 were 267, 188, 57 and 13 respectively. The resultant elevation of the number of SR for a strain may result in a failure to identify a mutagenic response. It is recommended that the number of PER be monitored in any modification of the Ames test that makes use of elevated numbers of bacteria.

Mutagenicity Tests↗

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Dibutyl- and di-(2-ethylhexyl)phthalate in fish.

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Canada↗

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The retention, distribution, excretion, and metabolism of dibutyl phthalate-7-14 C in the rat.

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Animals↗

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Organohalogen residues in human adipose autopsy samples from six Ontario municipalities.

Human adipose tissue samples obtained during autopsies in 6 Canadian Great Lakes municipalities were analyzed for chlorobenzenes, polychlorobiphenyls, and organohalogen pesticide residues. The frequency of occurrence and the range and mean for 28 organohalogen residues are reported for male and female donors in each municipality. Overall mean residue values in females were significantly higher than those in males for hexachlorobenzene, beta-HCH, p,p'-DDE,p,p'-DDD + o,p'-DDT, and p,p'-DDT. The means and ranges of residue values were similar to those reported in previous Canadian surveys.

Adipose Tissue↗

PubMedDate not supplied

Determination of halogenated contaminants in human adipose tissue.

A method has been developed for determination of organochlorine contaminants in human adipose tissue. After fat extraction from the tissue with acetone-hexane (15 + 85, v/v), organochlorines were fractionated from fat by gel permeation chromatography with methylene chloride-cyclohexane (1 + 1, v/v) as solvent. After Florisil column cleanup, the GPC extract was analyzed by capillary column gas chromatography using 2 columns of different polarity. Compound identity was confirmed by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries for fortification levels of 10-500 ng/g were greater than 80% except for trichlorobenzene and hexachlorobutadiene (ca 60%).

Adipose Tissue↗