Effect of mannitol and cold treatments on phosphate uptake and protein phosphorylation in Lemna minor (L.) plants

This report is aimed at elucidating the effect of mannitol and cold treatments on P uptake and protein phosphorylation in Lemna minor plants. Duckweed p lants were incu bated in the presence of [32P]or [33P]Pi in half-strength phosphate deprived E-medium under constant light regime for 1.5 h. Total plant protein extracts (pellet and supernatant) were then prepared and subjected to IEF x SDS-PAGE. To analyse the effect of the stresses on P uptake and protein labelling, Lemna minor plants were preincubated with 0.1, 0.5 mol · L-1 mannitol and at 4°C respectively, for 4 hours, before adding labelled orthophosphate. The results show that the general protein phosphorylation (including LHCII) is related to the level of P uptake. Radioactive phosphate incorporation is stimulated by a low concentration of mannitol (0.1 mol · L-1) but reduced by 0.5 mol · L-1 mannitol and cold stress in planta. The labelling into proteins is affected neither when stresses were applied to the plants after incubation with labelled orthophosphate, nor after in vitro protein phosphorylation. This indicates that general protein kinase activities in vivo are strictly limited by P uptake. A marked accumulation of soluble hexoses (mainly sucrose, glucose, and fructose) is observed under imposed stress, suggesting that the inhibition of P uptake in response to hyperosmotic and cold stresses is mediated by sugar accumulation in situ. However, metabolisable sugars like glucose did not alter the entry of phosphate at concentrations of 0.5 mol · L-1, showing that the chemical nature of the osmoticum influences P uptake.

Oral treatments of Echinococcus multilocularis-infected mice with the antimalarial drug mefloquine that potentially interacts with parasite ferritin and cystatin.

This study investigated the effects of oral treatments of Echinococcus multilocularis-infected mice with the antimalarial drug mefloquine (MEF) and identified proteins that bind to MEF in parasite extracts and human cells by affinity chromatography. In a pilot experiment, MEF treatment was applied 5 days per week and was intensified by increasing the dosage stepwise from 12.5 mg/kg to 200 mg/kg during 4 weeks followed by treatments of 100 mg/kg during the last 7 weeks. This resulted in a highly significant reduction of parasite weight in MEF-treated mice compared with mock-treated mice, but the reduction was significantly less efficacious compared with the standard treatment regimen of albendazole (ABZ). In a second experiment, MEF was applied orally in three different treatment groups at dosages of 25, 50 or 100 mg/kg, but only twice a week, for a period of 12 weeks. Treatment at 100 mg/kg had a profound impact on the parasite, similar to ABZ treatment at 200 mg/kg/day (5 days/week for 12 weeks). No adverse side effects were noted. To identify proteins in E. multilocularis metacestodes that physically interact with MEF, affinity chromatography of metacestode extracts was performed on MEF coupled to epoxy-activated Sepharose(®), followed by SDS-PAGE and in-gel digestion LC-MS/MS. This resulted in the identification of E. multilocularis ferritin and cystatin as MEF-binding proteins. In contrast, when human cells were exposed to MEF affinity chromatography, nicotinamide phosphoribosyltransferase was identified as a MEF-binding protein. This indicates that MEF could potentially interact with different proteins in parasites and human cells.

Associations among Nosema spp. fungi, Varroa destructor mites, and chemical treatments in honey bees, Apis mellifera

Nosema spp. and Varroa destructor are common parasites of honey bee colonies. Beekeepers routinely treat colonies with the fungicide fumagillin to control Nosema and an array of miticides to control V. destructor. Interactions between these parasites and chemical treatments are poorly understood. We allocated honey bee colonies to distinct chemical treatment regimes and monitored parasite intensities in the subsequent year. Infections of Nosema and infestations of V. destructor were positively correlated. Fumagillin was effective at mitigating Nosema intensities only over the short term, suggesting that biannual application is essential. V. destructor intensities were higher in colonies that had been previously treated with miticides, reasons for this warrant further investigation.