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The ability of two alkyl pyridinium sponge toxin preparations (poly-APS and halitoxin) to form transient pores/lesions in cell membranes and allow transfection of plasmid cDNA have been investigated using HEK 293 cells. Poly-APS and halitoxin preparations caused a collapse in membrane potential, reductions in input resistance and increased Ca2+ permeability. At least partial recovery was observed after poly-APS application but recovery was more rarely seen with halitoxin. The transfection with plasmid cDNAs for an enhanced green fluorescent protein (EGFP) and human tumour necrosis factor receptor 2 (TNFR2) was assessed for both toxin preparations and compared with lipofectamine. Stable transfection was achieved with poly-APS although it was less efficient than lipofectamine. These results show that viable cells transfected with alien cDNA can be obtained using novel transient pore-forming alkyl pyridinium sponge toxins and a simple pre-incubation protocol. This provides the first proof of principle that pore-forming alkyl pyridinium compounds can be used to deliver cDNA to the intracellular environment without permanently compromising the plasma membrane.

1 In this study, we investigated the electrophysiological actions of a high molecular weight fraction, predominantly containing two polymeric 1,3-alkylpyridinium salts (poly-APS) of 5.5 and B19 kDa isolated from the marine sponge Reniera sarai. The biological properties of poly-APS are of particular interest because this preparation may be used to deliver macromolecules into the intracellular environment without producing long-term damage to cells. Poly-APS (50 -0.05 mg ml À1 ) was applied to cultured dorsal root ganglion neurones or HEK 293 cells and changes in cell membrane properties were measured using whole-cell patch-clamp recording and fura-2 Ca 2 þ imaging. 2 Poly-APS (50 mg ml À1 ) evoked irreversible depolarisations in membrane potential and reductions in input resistance. However, doses of 5 mg ml À1 and less produced reversible effects on these cell membrane characteristics and on Ca 2 þ permeability. 3 At 0.05 mg ml À1 , poly-APS could evoke robust transient increases in Ca 2 þ permeability without damaging the neurones or subsequently attenuating Ca 2 þ entry through voltage-activated channels. 4 Bathing cells in NaCl-based extracellular medium containing 1.5 mm zinc attenuated the irreversible and reversible effects of poly-APS on membrane properties (membrane potential, input resistance and whole-cell currents). In both DRG neurones and HEK 293 cells, zinc attenuated Ca 2 þ entry evoked by poly-APS. These effects of zinc were only observed if zinc was continually present during poly-APS application. However, zinc failed to attenuate the actions of poly-APS if it was applied after the sponge toxin preparation had evoked changes in membrane properties. 5 In conclusion, the pore-forming preparation poly-APS can have dose-dependent interactions with cell membranes and at low doses these can be reversible. Additionally, the interactions between poly-APS and cell membranes could be attenuated by zinc.

Background: Gabapentin and pregabalin have wide-ranging therapeutic actions, and are structurally related to the inhibitory neurotransmitter GABA. Gabapentin, pregablin and GABA can all modulate voltage-activated Ca 2+ channels. In this study we have used whole cell patch clamp recording and fura-2 Ca 2+ imaging to characterise the actions of pregabalin on the electrophysiological properties of cultured dorsal root ganglion (DRG) neurones from neonatal rats. The aims of this study were to determine whether pregabalin and gabapentin had additive inhibitory effects on high voltage-activated Ca 2+ channels, evaluate whether the actions of pregabalin were dependent on GABA receptors and characterise the actions of pregabalin on voltage-activated potassium currents.

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The camel is important in many of the arid zones of the world where its ability to continue to produce and reproduce offers considerable potential. It is able to forage at greater distances from water sources than cattle, goats or sheep; increasing the area which can be grazed and browsed, and thus easing grazing pressure on vegetation close to water sources. These factors commend it as a primary source of transport, power, meat, milk and hides in arid areas. Both the dromedary camel (Camelus dromedarius), and the bactrian camel (Camelus bactrianus) have long been utilised by the peoples of areas where these camels are indigenous, and there has increasingly been a more general awareness of the potential of the species. The United Arab Emirates (UAE) is among countries where camels have considerable cultural importance. Recently attention has focused on the potential of the camel to supply meat, and Wardeh (1992) estimated world annual camel meat production to be 538,000 tons. The number of camels in the UAE increased from 57,000 in 1979 to 100,000 in 1989, and Wilson (1984) reported that camels account for 58% of the domestic herbivore biomass. However little is known about the constraints to camel production (Schwartz et al 1983). A factor limiting production is the availability of feeds. Currently heavily subsidised feed concentrates are imported, and investigations have focused on the better use of local resources. The UAE is one of the largest producers of dates with over 19 million palms. By-products have not been well utilized, but feeding trials with pits (Al-Yousef et al, 1987); and fruits (El-Gasim et al, (1987) and Kohnke and Cluer (1992) have been reported. Dates are low in nitrogen, and no reports on the use of urea in camel diets could be found.