Treatment of the first leaves of barley (Hordeum vulgare L. cv. Golden Promise) seedlings with methyl jasmonate (MJ) led to small, but significant increases in levels of free putrescine and spermine 1 d later and to significant increases in levels of free putrescine, spermidine and spermine by 4 d following treatment. MJ-treated first leaves also exhibited significant increases in the amounts of soluble conjugates of putrescine and spermidine 1, 2 and 4 d after treatment. In second leaves of plants where the first leaves had been treated with MJ, no significant changes in levels of free polyamines were observed, but significant increases in levels of soluble conjugates of putrescine and spermidine were detected. These changes were accompanied by increased activities of soluble ornithine decarboxylase (ODC), soluble and particulate arginine decarboxylase (ADC), and S-adenosylmethionine decarboxylase (AdoMetDC), in first and second leaves following treatment of the first leaves with MJ. Activities of soluble and particulate diamine oxidase (DAO) were also higher in first and second leaves following treatment of the first leaves with MJ. Treatment of the first leaves with MJ led to a significant reduction in powdery mildew (Blumeria graminis f. sp. hordei) infection on the second leaves and also resulted in significant increases in activities of the plant defence-related enzymes, phenylalanine ammonia lyase (PAL) and peroxidase.

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Alachlor (2-chloro-2',6'-diethyl-N-[methoxymethyl]-acetanilide) is a restricted-use chloracetanilide herbicide which has been shown previously to produce a dose-dependent incidence of olfactory mucosal tumors in rats following chronic dietary exposure. However, the mechanism of alachlor carcinogenicity is poorly understood. Alachlor was administered i.p. to male Long-Evans rats for up to 28 days at doses that are carcinogenic in chronic studies in order to study olfactory lesion development and alterations in cell proliferation. Neither treatment-related olfactory mucosal lesions nor regenerative cell proliferation, as assessed with BrdU labeling, was detected. In vitro genotoxicity studies using Salmonella typhimurium strain TA100 showed that alachlor was non-mutagenic in the absence of metabolic activation. When pre-incubated with an olfactory mucosal S9 activation system, alachlor induced a weak, dose-dependent mutagenic response at 500-1250 micrograms/plate, with toxicity at higher doses. In contrast, an S9 activation system derived from nasal respiratory mucosa, the tissue physically juxtaposed with the olfactory mucosa but reportedly not susceptible to alachlor-induced tumors, did not produce a mutagenic response for alachlor or the positive control. Thus, this result suggested site-specificity of alachlor activation consistent with the target site of carcinogenicity. The mutagenicity of alachlor to Salmonella, in the presence of an olfactory mucosal-activating system, was confirmed by a limited positive response in the mouse lymphoma assay. Here there were increases in small colony mutants (indicative of chromosomal effects) as well as large colony mutants (which reflect gene mutations). This study suggests that target tissue bioactivation of alachlor results in the formation of one or more mutagenic metabolite(s), which may be critical in alachlor-induced nasal tumorigenesis.

The Mouse Lymphoma Assay (MLA) Workgroup addressed and reached consensus on a number of issues. Discussion focused on five areas: (1) acceptable assay versions; (2) cytotoxicity measure; (3) 24‐hr treatment; (4) microwell colony counting and sizing; and (5) data acceptability/statistical analysis. Although the International Conference on Harmonisation (ICH) indicated a preference for the microwell over the soft agar method, all of the workgroup members agreed that both versions of the MLA are equally acceptable. The workgroup agreed that it is desirable for both assay versions to use the same measure of cytotoxicity to define the acceptable and required concentration range. Currently, laboratories using the microwell version use the relative survival (RS) determined by cloning immediately after the treatment. Laboratories using the soft agar method do not obtain an RS but use the relative total growth (RTG), a combination of the relative suspension growth (RSG) during the expression period and the relative cloning efficiency determined at the time of mutant selection. The workgroup agreed to investigate the RSG, the RS, and the RTG and to develop further guidance. In the interim, the workgroup reached consensus that the RTG be used as the standard measure of cytotoxicity. The ICH recommended a 24‐hr treatment in the absence of S9 when negative results are obtained with short (3–4 hr) treatments. The workgroup agreed to retain this requirement but acknowledged that more data are needed prior to making final recommendations concerning the need for and the specific protocol for the 24‐hr treatment. Environ. Mol. Mutagen. 35:185–190, 2000 Published 2000 Wiley‐Liss, Inc.