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.

Invasion and persistence of Mycoplasma bovis in embryonic calf turbinate cells.

Mycoplasma bovis is a wall-less bacterium causing bovine mycoplasmosis, a disease showing a broad range of clinical manifestations in cattle. It leads to enormous economic losses to the beef and dairy industries. Antibiotic treatments are not efficacious and currently no efficient vaccine is available. Moreover, mechanisms of pathogenicity of this bacterium are not clear, as few virulence attributes are known. Microscopic observations of necropsy material suggest the possibility of an intracellular stage of M. bovis. We used a combination of a gentamicin protection assay, a variety of chemical treatments to block mycoplasmas entry in eukaryotic cells, and fluorescence and transmission electron microscopy to investigate the intracellular life of M. bovis in calf turbinate cells. Our findings indicate that M. bovis invades and persists in primary embryonic calf turbinate cells. Moreover, M. bovis can multiply within these cells. The intracellular phase of M. bovis may represent a protective niche for this pathogen and contribute to its escape from the host's immune defense as well as avoidance of antimicrobial agents.

Visualization of cell microtubules in their native state.

BACKGROUND INFORMATION Over the past decades, cryo-electron microscopy of vitrified specimens has yielded a detailed understanding of the tubulin and microtubule structures of samples reassembled in vitro from purified components. However, our knowledge of microtubule structure in vivo remains limited by the chemical treatments commonly used to observe cellular architecture using electron microscopy. RESULTS We used cryo-electron microscopy and cryo-electron tomography of vitreous sections to investigate the ultrastructure of microtubules in their cellular context. Vitreous sections were obtained from organotypic slices of rat hippocampus and from Chinese-hamster ovary cells in culture. Microtubules revealed their protofilament ultrastructure, polarity and, in the most favourable cases, molecular details comparable with those visualized in three-dimensional reconstructions of microtubules reassembled in vitro from purified tubulin. The resolution of the tomograms was estimated to be approx. 4 nm, which enabled the detection of luminal particles of approx. 6 nm in diameter inside microtubules. CONCLUSIONS The present study provides a first step towards a description of microtubules, in addition to other macromolecular assemblies, in an unperturbed cellular context at the molecular level. As the resolution appears to be similar to that obtainable with plunge-frozen samples, it should allow for the in vivo identification of larger macromolecular assemblies in vitreous sections of whole cells and tissues.

Effect of zirconia surface treatments on the shear strength of zirconia/veneering ceramic composites

Aim of the investigation was to assess the effect of different surface treatments on the bond strength of veneering ceramics to zirconia. In a shear test, the influences of polishing, sandblasting, and silica-coating of the zirconia surface on bonding were assessed with five different veneering ceramics. In addition the effect of liner application was examined. With one veneering ceramic, the impact of regeneration firing of zirconia was also evaluated. Statistical analysis was performed with one-way ANOVA and post hoc Scheffé's test. Failure in every case occurred in the veneering ceramic adjacent to the interface with a thin layer of ceramic remaining on the zirconia surface, indicating that bond strength was higher than the cohesive strength of the veneering ceramic. Shear strength ranged from 23.5 +/- 3.4 MPa to 33.0 +/- 6.8 MPa without explicit correlation to the respective surface treatment. Regeneration firing significantly decreased the shear strength of both polished and sandblasted surfaces. Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds. On this note, sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.

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.