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1 Thirty migraine patients who had taken the leaves, tablets or capsules of feverfew daily for more than 11 consecutive months were compared to 30 feverfew non-user migraine patients who had been individually age- and sex-matched. 2 The frequency of chromosomal aberrations and sister chromatid exchanges (SCE) were determined from lymphocyte cultures established from blood samples taken over a period of several months. Matched pairs were sampled on the same date for two-thirds of the cases, and the greatest difference in sampling time of the remainder was 20 days. Also, the mutagenicity of urine samples from 10 feverfew user migraine patients was compared to that from 10 matched non-user migraine patients using the Ames Salmonella mutagenicity test system. Paired samples were given on the same date. 3 The mean frequency of chromosomal aberrations in the feverfew user group was lower than that in the non-user group both in terms of cells with breaks (2.13% vs 2.76%) and in terms of cells with all aberrations (4.34% vs 5.11%). However, this difference was small and not significant. 4 The mean frequency of SCE in the feverfew exposed group was lower than that in the control group (8.78 vs 8.80 SCE/cell), but, this difference was not significant as determined by factorial analysis of variance (P = 0.897). There was a highly significant variance between the frequencies of SCE in the matched pairs of migraine patients but this was not related to age, sex or feverfew exposure. 5 The mean number of revertants in the Ames mutagenicity assay was greater for the urine of the feverfew user migraine patients than that of the non-user migraine patients, in both strains of bacteria, with or without the inclusion of an S-9 metabolizing system. However, the increases were small and not significant. 6 The data indicate that the prophylactic use of feverfew for the alleviation of migraine symptoms affects neither the frequency of chromosomal aberrations nor the frequency of SCE in the circulating peripheral lymphocytes. Also, the mutagenicity of urine from feverfew user migraine patients is unaffected compared to urine from non-user migraine patients detectable by the methods used in this study.

1 The stimulation of ( 3H)-thymidine incorporation by lymphocytes in response to phorbol and seven other phorbol related compounds was investigated. 2 Lymphocytes from each of a small group of individuals were treated with the test compounds over wide concentration ranges. 3 All the tested compounds, including the most active, 12-0-tetradecanoylphorbol-13-acetate, were far less effective lymphocyte mitogens than the plant lectin phytohaemagglutinin. 4 Inter-individual differences were detected in the maximum response to the phorbols but not in their stimulating potency, as estimated by the concentration producing a half maximal response. 5 The rank order of the lymphocyte stimulating potency of the tested compounds was similar to the rank order of both tumour promoting activity and irritant potency in mouse skin. 6 Lymphocyte stimulation was paralleled equally well by these two mouse skin responses.

Interest in certain esters of the diterpene phorbol centres upon two actions which they exhibit to varying degrees. The first is the intense inflamation produced upon application to mammalian skin and the second is the tumour promoting activity exhibited on repeated application to mouse skin following a sub-threshold dose of carcinogen. The most potent phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) induces cell proliferation and subsequent epidermal hyperplasia when applied in nanomolar quantities to mouse skin. These sequential events are recognised as being essential components of TPA's action as a mouse skin tumour promoter (Boutwell 1974). Analogous TPA-induced cell proliferation (mitogenesis) is observed in vitro in human lymphocyte cultures (Estensen et a1 1974). As part of an investigation into the mechanisms of action of tumour promoters we have examined the abilities of a series of phorbol esters to induce human lymphocyte proliferation, in order to determine if the activities of these compounds as lymphocyte mitogens correlate with their potencies as tumour promoters.Mononuclear cells, predominantly lymphocytes, were separated from heparinised human peripheral blood by sedimentation on Ficoll-Isopaque gradients. The cells were washed in phosphate buffered saline and then washed and resuspended at lo6 cells ml-' in a modified RPMI 1640 medium supplemented with 10% foetal bovine serum. The cell suspension was treated with phorbol ester and dispensed in 0.1 ml volumes (lxloS cells) into the wells of microtitre plates. The plates were incubated for 72h at 3 7 O~ in a humidified 5% C01 atmosphere. Proliferative stimulation of lymphocytes was assessed by cellular 3~-thymidine uptake. 3~-thymidine 1U Ci ml-' was added to each microculture for the final 24h of incubation. The microcultures were harvested onto glass fibre filter discs and the entrained cells washed successively with distilled water, 5% trichloroacetic acid and methanol. The discs were dried thoroughly in glass scintillation vials. Five ml of scintillation cocktail (PPO 69, POPOP 0.059 toluene) was added to each vial. Counts per minute (cpm) of incorporated 3~-thymidine from a minimum of five replicate microcultures were obtained for each phorbol ester dose.