ABSTRACT
The solar neighbourhood is the closest and most easily studied sample of the Galactic interstellar medium, an understanding of which is essential for models of star formation and galaxy evolution. Observations of an unexpectedly intense diffuse flux of easily absorbed 1/4-kiloelectronvolt X-rays, coupled with the discovery that interstellar space within about a hundred parsecs of the Sun is almost completely devoid of cool absorbing gas, led to a picture of a 'local cavity' filled with X-ray-emitting hot gas, dubbed the local hot bubble. This model was recently challenged by suggestions that the emission could instead be readily produced within the Solar System by heavy solar-wind ions exchanging electrons with neutral H and He in interplanetary space, potentially removing the major piece of evidence for the local existence of million-degree gas within the Galactic disk. Here we report observations showing that the total solar-wind charge-exchange contribution is approximately 40 per cent of the 1/4-keV flux in the Galactic plane. The fact that the measured flux is not dominated by charge exchange supports the notion of a million-degree hot bubble extending about a hundred parsecs from the Sun.
ABSTRACT
We studied the effect of riboflavin treatment on the clinical status and on the activities of beta-oxidation and respiratory chain enzymes in a 69-year-old patient with late-onset myopathy. Before treatment, she was very weak and wasted in the limbs and trunk muscles; also, she could not walk or attend to daily activities. Marked lipid storage was present in the muscle biopsy. The activities of short-chain acyl coenzyme A (acyl-CoA) dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and long-chain acyl-CoA dehydrogenase (LCAD) in isolated muscle mitochondria were reduced to less than 10% of control values. This defect in fatty acid oxidation was associated with a marked deficiency of two flavin-dependent respiratory chain complexes: complex I activity was 20% and complex II activity was 25% of control values. By contrast, the activities of the nonflavin-dependent complex III and complex IV were normal. Western blot analysis of the patient's muscle mitochondrial extracts with antibodies raised against purified SCAD, MCAD, and the alpha- and beta-subunits of the electron transfer flavoprotein (ETF) showed absence of SCAD cross-reacting material (CRM), markedly decreased MCAD-CRM, and normal amounts of both alpha- and beta-ETF-CRM. After riboflavin treatment, the patient's clinical status dramatically improved and morphologic changes in muscle disappeared. SCAD activity increased to 55% of control values, whereas MCAD, LCAD, and complex I and complex II activities normalized. SCAD and MCAD immunoreactivity was restored to normal. On the basis of our experience and the data in the literature, we concluded that some lipid storage myopathies can show dramatic response to riboflavin.
