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A virus obtained from sweet potatoes in Kenya, Uganda and Tanzania was transmitted by inoculation of sap and by whiteflies (Bemisia tabaci).It infected forty-five of I 19 plant species in fourteen of thirty-six plant families. It was propagated in Nicotiana glutinosa and N . tabacum, in which diagnostic symptoms of vein clearing, leaf curling and distortion developed. Chenopodium quinoa was a good local lesion host.Different seedling lines of sweet potato differed greatly in their susceptibility to infection and in symptoms produced; some developed leaf mottling and were stunted, some were symptomless, and some appeared immune.The virus was transmitted by dodder (Cuscuta campestris) but not by aphids, or through seed of Ipomoea nil or N . clevelandii. Sweet potato sap contained strong inhibitors of infection, and a low concentration of virus.Virus-free cuttings of sweet potato were obtained by thermotherapy (4-5 wk at 35 "C), or by meristem-tip culture. The virus remained infective in sap of N . tabacum after dilution to 10-3, or after 10 min at 55 "C (but not 60 "C), 3 but not 7 days at 18 "C, or 42 but not 49 days at 2 "C. Infectivity was abolished by sonication or U.V.irradiation, by 2 % formaldehyde or 2 % tri-sodium orthophosphate, and was greatly decreased by 20% CHCl, or 20% ether. Purified virus preparations were obtained from N . tabacum by clarifying phosphate buffer extracts with n-butanol, virus precipitation with polyethylene glycol, and differential centrifugation. The virus sedimented as one band in density gradients, and produced a single sedimenting boundary in analytical centrifugation (sozo, 7 155s). It contained one polypeptide species of mol wt 37 700, and preliminary digestion experiments suggested a single-stranded RNA.Antisera prepared against the virus reacted specifically in precipitin tube tests with titres of 1/16 384, but no serological relationships could be found between the virus and fourteen viruses of the potato virus Y group.Electron micrographs showed straight, filamentous particles c. 950 nm

Salmonella typhimurium strains TA98 and TA100 were used to assess the mutagenic potential of the aerosol from a commercially available, rechargeable, closed system electronic-cigarette. Results obtained were compared to those for the mainstream smoke from a Kentucky reference (3R4F) cigarette. Two different test matrices were assessed. Aerosol generated from the e-cigarette was trapped on a Cambridge filter pad, eluted in DMSO and compared to cigarette smoke total particulate matter (TPM), which was generated in the same manner for mutagenicity assessment in the Salmonella assay. Fresh e-cigarette and cigarette smoke aerosols were generated on the Vitrocell VC 10 smoking robot and compared using a modified scaled-down 35mm air agar interface (AAI) methodology. E-cigarette aerosol collected matter (ACM) was found to be non-mutagenic in the 85mm plate incorporation Ames assay in strains TA98 and TA100 conducted in accordance with OECD 471, when tested up to 2400μg/plate. Freshly generated e-cigarette aerosol was also found to be negative in both strains after an AAI aerosol exposure, when tested up to a 1L/min dilution for up to 3h. Positive control responses were observed in both strains, using benzo[a]pyrene, 2-nitrofluorene, sodium azide and 2-aminoanthracene in TA98 and TA100 in the presence and absence of metabolic activation respectively. In contrast, cigarette smoke TPM and aerosol from 3R4F reference cigarettes were found to be mutagenic in both tester strains, under comparable test conditions to that of e-cigarette exposure. Limited information exists on the mutagenic activity of captured e-cigarette particulates and whole aerosol AAI approaches. With the lower toxicant burden of e-cigarette aerosols compared to cigarette smoke, it is clear that a more comprehensive Ames package of data should be generated when assessing e-cigarettes, consisting of the standard OECD-five, TA98, TA100, TA1535, TA1537 (or TA97) and E. coli (or TA102). In addition, TA104 which is more sensitive to the carbonyl based compounds found in e-cigarette aerosols under dry-wicking conditions may also prove a useful addition in a testing battery. Regulatory standard product testing approaches as used in this study will become important when determining whether e-cigarette aerosols are in fact less biologically active than cigarette smoke, as this study suggests. Future studies should be supported by in vitro dosimetry approaches to draw more accurate comparisons between cigarette smoke, e-cigarette aerosol exposure and human use.

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