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Aims: Recently, a new defibrillation modality using nanosecond pulses was shown to be effective at much lower energies than conventional 10 millisecond monophasic shocks in ex vivo experiments. Here we compare the safety factors of 300 nanosecond and 10 millisecond shocks to assess the safety of nanosecond defibrillation. Methods and results: The safety factor, i.e. the ratio of median effective doses (ED50) for electroporative damage and defibrillation, was assessed for nanosecond and conventional (millisecond) defibrillation shocks in Langendorff-perfused New Zealand white rabbit hearts. In order to allow for multiple shock applications in a single heart, a pair of needle electrodes was used to apply shocks of varying voltage. Propidium iodide (PI) staining at the surface of the heart showed that nanosecond shocks had a slightly lower safety factor (6.50) than millisecond shocks (8.69), p = 0.02; while PI staining cross-sections in the electrode plane showed no significant difference (5.38 for 300 ns shocks and 6.29 for 10 ms shocks, p = 0.22). Conclusions: In Langendorff-perfused rabbit hearts, nanosecond defibrillation has a similar safety factor as millisecond defibrillation, between 5 and 9, suggesting that nanosecond defibrillation can be performed safely. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal fungi (EMF) are critical to the establishment of many plant species and an important consideration in ecological restoration of southern beech (Nothofagaceae) forest. However, information on spore viability and storage is lacking for EMF taxa associated with southern beech. This study tested the viability and germination of spores from fruiting bodies collected during autumn and spring from mountain beech forest, Otago, New Zealand. Nuclear ribosomal ITS sequences matched autumn collections to the EMF genera Cortinarius, Inocybe and Russula, but all spring collections were an undescribed hypogeous taxon resembling the native EMF genus Hysterangium, referred to here as Hysterangiaceae 'Motatapu'. We investigated propidium iodide as a spore viability test, and compared spore germination in water vs glucose, in different temperature and light regimes, and between freshly collected spores and spores from fruiting bodies dried at 30°C or frozen at −20°C. Propidium iodide did not stain all devitalised spores, so may be unreliable for quantifying viability of fresh spores. Spore germination in water was <6% for all genera and <2% for most taxon × treatment combinations. Fresh spores of Hysterangiaceae 'Motatapu' suspended in 4°C water showed higher germination than at 20°C; excluding light had no significant effect. Spores of the same taxon suspended in 10% and 20% glucose showed lower germination in comparison to water and showed deformations. Germination percentages of all taxa decreased with storage, but spores of some taxa retained viability for 120 days in 4°C water suspensions. Spores of Hysterangiaceae 'Motatapu' showed the least loss of viability with storage of all taxa investigated. For the purposes of storing EMF material for use as inoculum, we recommend drying fruiting bodies at 30°C for storage, then preparing fresh spore suspensions in water when inoculum is required. [ABSTRACT FROM AUTHOR]