Cortisone sensitive T-cells in Peyer's patches

Summary Pretreatment of donor lymphoid cells with cortisone has been shown to depress the T-cell subpopulation responsible for cellular proliferation in the GVH reaction. A quantitative assay as well as the histological criteria of the GVH reaction have been used in this study to demonstrate the presence of cortisone-sensitive T-cells within the Peyer's patches as well as in the spleen and mesenteric lymph nodes in the rat.This work was supported by a grant of the Délégation Générale à la Recherche Scientifique et Technique (No. 74-7-0619).     

The harlequin mouse mutation downregulates apoptosis-inducing factor

Harlequin (Hq) mutant mice have progressive degeneration of terminally differentiated cerebellar and retinal neurons. We have identified the Hq mutation as a proviral insertion in the apoptosis-inducing factor (Aif) gene, causing about an 80% reduction in AIF expression. Mutant cerebellar granule cells are susceptible to exogenous and endogenous peroxide-mediated apoptosis, but can be rescued by AIF expression. Overexpression of AIF in wild-type granule cells further decreases peroxide-mediated cell death, suggesting that AIF serves as a free radical scavenger. In agreement, dying neurons in aged Hq mutant mice show oxidative stress. In addition, neurons damaged by oxidative stress in both the cerebellum and retina of Hq mutant mice re-enter the cell cycle before undergoing apoptosis. Our results provide a genetic model of oxidative stress-mediated neurodegeneration and demonstrate a direct connection between cell cycle re-entry and oxidative stress in the ageing central nervous system.     

A Bragg glass phase in the vortex lattice of a type II superconductor

Although crystals are usually quite stable, they are sensitive to a disordered environment: even an infinitesimal amount of impurities can lead to the destruction of crystalline order. The resulting state of matter has been a long-standing puzzle. Until recently it was believed to be an amorphous state in which the crystal would break into 'crystallites'. But a different theory predicts the existence of a novel phase of matter: the so-called Bragg glass, which is a glass and yet nearly as ordered as a perfect crystal. The 'lattice' of vortices that contain magnetic flux in type II superconductors provide a good system to investigate these ideas. Here we show that neutron-diffraction data of the vortex lattice provides unambiguous evidence for a weak, power-law decay of the crystalline order characteristic of a Bragg glass. The theory also predicts accurately the electrical transport properties of superconductors; it naturally explains the observed phase transitions and the dramatic jumps in the critical current associated with the melting of the Bragg glass. Moreover, the model explains experiments as diverse as X-ray scattering in disordered liquid crystals and the conductivity of electronic crystals.     

Morphological transformation of human keratinocytes expressing the LMP gene of Epstein-Barr virus.

The association of Epstein-Barr virus (EBV) with nasopharyngeal carcinoma (NPC) has been known for some time, but the precise role of EBV in this cancer is poorly understood, due partly to the lack of an in vitro system for studying NPC cells and the effect of EBV on epithelial cells. Biopsies of NPC tumours have revealed expression of the EBV latent membrane protein (LMP) in 65% of cases, suggesting that in at least some NPC tumours LMP may contribute to cell transformation. Here we address the question of the effect of LMP expression on epithelial cells. Transfection of an immortalized, non-tumorigenic keratinocyte cell line (RHEK-1) with the LMP gene causes a striking morphological transformation: the originally flat, polygonal colonies change to bundles of spindle-shaped cells that form multilayer foci, and cytokeratin expression is down-regulated. Our results suggest that LMP expression may be an important causal factor in the development of NPC.