T2 relaxation time histograms in multiple sclerosis.

An accurate measurement of the transverse relaxation time T(2), and the histogram of T(2) in the brain parenchyma can be accomplished in vivo using a multi-echo magnetic resonance imaging sequence. An estimate of the error in the T(2) measurement is derived using copper sulfate doped water phantoms. Correction factors are calculated and applied to the signal intensity of each voxel prior to the in vivo T(2) evaluation. These corrected T(2) are in good agreement with the theoretical values calculated from copper sulfate concentrations. This technique is then applied to calculate T(2) histograms of the brain. The population studied was composed of normal volunteers and multiple sclerosis patients. The corrected T(2) histogram method discriminates the normal control population from the MS population, and also discriminates between relapsing-remitting patients and primary progressive or secondary progressive patients. Moreover using this approach we are able to detect in MS patients a global shift of the T(2) of the white mater toward higher values. The results of this study showed that the method is easy to implement and may be used to characterize MS pathology.

A galactic chimney in the Perseus arm of the Milky Way.

Galaxies are surrounded by large haloes of hot gas which must be replenished as the gas cools. This has led to the concept of galactic 'chimneys'--cavities in the interstellar medium, created by multiple supernova explosions, that can act as conduits for the efficient transport of hot gas from a galaxy's disk to its halo. Here we present a high-resolution map of atomic hydrogen in the Perseus arm of our galaxy, which shows clear evidence for the existence of such a chimney. This chimney appears to have been formed by the energetic winds from a cluster of young massive stars, and may currently have reached the stage of bowing out into the halo.

Heterogeneity in the Xenopus ribosomal transcription factor xUBF has a molecular basis distinct from that in mammals.

The Xenopus polymerase I transcription factor xUBF is an HMG-box protein which has been purified as two polypeptides of approximately 82 and 85 kDa. Recently a cDNA sequence predicted an xUBF protein (xUBF1) of 677 amino acids (79 kDa) containing five tandem HMG-boxes. Here a second and distinct xUBF cDNA has been isolated and characterised. This cDNA codes an xUBF protein (xUBF2) of 701 amino acids (82 kDa), having 93% homology with xUBF1 but containing an insertion of 22 amino acids between HMG-boxes 3 and 4. In vitro translation of synthetic mRNAs derived from the xUBF1 and 2 cDNAs was used to show that the electrophoretic mobility of the gene products accounted for the major xUBF molecular weight heterogeneity noted in vivo. It is also shown that the Xenopus laevis genome contains 3 or 4 distinct loci which hybridise with xUBF coding sequences, leaving open the possibility of yet further unrecognised heterogeneity in xUBF.