Progressive secondary neurodegeneration and microcalcification co-occur in osteopontin-deficient mice.

In the brain, osteopontin (OPN) may function in a variety of pathological conditions, including neurodegeneration, microcalcification, and inflammation. In this study, we addressed the role of OPN in primary and secondary neurodegeneration, microcalcification, and inflammation after an excitotoxic lesion by examining OPN knock-out (KO) mice. Two, four, and ten weeks after injection of the glutamate analogue ibotenate into the corticostriatal boundary, the brains of 12 mice per survival time and strain were evaluated. OPN was detectable in neuron-shaped cells, in microglia, and at the surface of dense calcium deposits. At this primary lesion site, although the glial reaction was attenuated in OPN-KO mice, lesion size and presence of microcalcification were comparable between OPN-KO and wild-type mice. In contrast, secondary neurodegeneration at the thalamus was more prominent in OPN-KO mice, and this difference increased over time. This was paralleled by a dramatic rise in the regional extent of dense microcalcification. Despite these differences, the numbers of glial cells did not significantly differ between the two strains. This study demonstrates for the first time a genetic model with co-occurrence of neurodegeneration and microcalcification, mediated by the lack of OPN, and suggests a basic involvement of OPN action in these conditions. In the case of secondary retrograde or transneuronal degeneration, OPN may have a protective role as intracellular actor.

Excess water storage induced by viscous strain localization during high-pressure shear experiment.

Strain localization in viscously deformed rocks commonly results in fine-grained shear zones where massive fluid circulation is regularly observed. Recently attributed to strain-induced pumping, this phenomenon may have major implications for the distribution of ores deposits and rock rheology. However, although grain size reduction and/or creep cavitation have been proposed as important processes, the source mechanism of fluid concentration remains unresolved, particularly at high pressure. Here we use secondary ion mass spectrometry to document the H2O content of fine-grained olivine across an experimental shear zone, which developed with grain size reduction during a H2O-saturated shear experiment at 1.2 GPa and 900 °C. Through data interpolation, the olivine matrix reveals high fluid concentrations where shear strain is localized. These concentrations far exceed the predicted amount of H2O that grain boundaries can contain, excluding grain size reduction as a unique source of water storage. Instead, we show that H2O increases per unit of grain boundary across the shear zone, suggesting that cavitation and "healing" processes compete with each other to produce a larger pore volume with increasing strain rate. This provides an alternative process for fluids to be collected where strain rate is the highest in deep shear zones.

High-pressure, High-temperature Deformation Experiment Using the New Generation Griggs-type Apparatus.

In order to address geological processes at great depths, rock deformation should ideally be tested at high pressure (> 0.5 GPa) and high temperature (> 300 °C). However, because of the low stress resolution of current solid-pressure-medium apparatuses, high-resolution measurements are today restricted to low-pressure deformation experiments in the gas-pressure-medium apparatus. A new generation of solid-medium piston-cylinder ("Griggs-type") apparatus is here described. Able to perform high-pressure deformation experiments up to 5 GPa and designed to adapt an internal load cell, such a new apparatus offers the potential to establish a technological basis for high-pressure rheology. This paper provides video-based detailed documentation of the procedure (using the "conventional" solid-salt assembly) to perform high-pressure, high-temperature experiments with the newly designed Griggs-type apparatus. A representative result of a Carrara marble sample deformed at 700 °C, 1.5 GPa and 10-5 s-1 with the new press is also given. The related stress-time curve illustrates all steps of a Griggs-type experiment, from increasing pressure and temperature to sample quenching when deformation is stopped. Together with future developments, the critical steps and limitations of the Griggs apparatus are then discussed.

Pica and refractory iron deficiency anaemia: a case report.

INTRODUCTION: Iron deficiency is the most common cause of anaemia worldwide. Pica, the ingestion of substances that are inappropriate for consumption, is associated with iron deficiency and may be under-diagnosed. CASE PRESENTATION: A 34-year-old woman presented with iron deficiency anaemia refractory to treatment for more than a decade. The clinical presentation, endoscopic findings and laboratory investigations were consistent with pica. Subsequent geophysical analysis confirmed that the ingested material was kaolin, a negatively charged silicate. CONCLUSION: Prolonged unexplained iron deficiency anaemia should prompt clinicians to remember and inquire about pica. In our patient, this would have averted numerous unnecessary investigations and prevented a decade-long suffering.