BACKGROUND AND PURPOSE:It is difficult to differentiate the cause of brain abscesses with the use of CT and MR imaging. We did a comparative evaluation of pyogenic, tubercular, and fungal brain abscesses by using conventional, diffusion-weighted imaging (DWI), and proton MR spectroscopy (PMRS) with an aim to define the unique features that may differentiate among the pyogenic, tubercular, and fungal brain abscesses.

Diffuse axonal injury (DAI) that follows traumatic brain injury (TBI) is thought to be a major contributor to neurocognitive dysfunction that sometimes follows TBI. Conventional magnetic resonance imaging (MRI), diffusion tensor imaging (DTI) and neuropsychological tests (NPT) were performed on 38 TBI patients [hemorrhagic DAI (H-DAI, n=8), non-hemorrhagic (Nh-DAI, n=7), with no apparent DAI on conventional MRI (NA-DAI, n=23)] with a Glasgow Coma Scale score ranging between 9 and 13. The fractional anisotropy (FA) and mean diffusivity (MD) were quantified from different regions of the corpus callosum (CC), and peri-ventricular white matter (PWM) within 5-14 days and 6 months following TBI. Patients in all three groups showed decreased FA in the anterior limb of the internal capsule (ALIC) and the posterior limb of the internal capsule (PLIC), while the genu of the CC showed a decrease in the H-DAI group during the early period following TBI that persisted 6 months later, which appeared to be consistent with axonopathy. In patients without abnormalities on conventional MRI and DTI in the initial phase, a significant decrease in FA and increase in MD were observed in a few regions of the CC at 6 months, which was suggestive of demyelination/gliosis. The changes in FA and MD in the CC and PWM at 6 months follow-up showed significant correlation with some of the NPT performed in the three groups. DTI demonstrates axonopathy in the acute stage, as well as at secondary stages, at 6 months post-injury in the CC and PWM in regions of normal-appearing white matter on conventional MRI.

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It is possible to differentiate anaerobic from aerobic or sterile brain abscesses on the basis of metabolite patterns observed at in vivo proton MR spectroscopy. This information may be useful in facilitating prompt and appropriate treatment of patients with these abscesses.

Methylamine dehydrogenase from Paracoccus denitrificans was purified to homogeneity in two steps from the periplasmic fraction of methylamine-grown cells. The enzyme exhibited a pI value of 4.3 and was composed of two 46,700-dalton subunits and two 15,500-dalton subunits. Each small subunit possessed a covalently bound pyrrolo-quinoline quinone prosthetic group. The amino acid compositions of the large and small subunits are very similar to those of other methylamine dehydrogenases which have been isolated from taxonomically different sources. It has been established recently that certain oxidoreductases from a variety of sources contain pyrrolo-quinoline quinone (PQQ) as a prosthetic group (2, 4, 10, 11). These quinoproteins include bacterial methanol (9) and glucose dehydrogenases (12), which possess noncovalently associated PQQ, and bacterial methylamine dehydrogenase, which contains a covalently bound form of PQQ (8,21). Mammalian plasma amine oxidase (26) and choline dehydrogenase (3) also possess covalently attached PQQ. When grown on methylamine as a sole source of carbon and energy, Paracoccus denitrificans synthesizes a methylamine dehydrogenase which functions in the periplasm of this gramnegative bacterium and donates electrons to a periplasmic type I blue copper protein, amicyanin (16). We have previously reported the partial purification of methylamine dehydrogenase from P. denitrificans (16) and have characterized the physical and redox properties of amicyanin (14,16,18,25) and periplasmic c-type cytochromes (14, 17) which accept electrons from methylamine dehydrogenase via amicyanin. This paper reports a relatively simple procedure by which methylamine dehydrogenase was purified to homogeneity from P. denitrificans and describes several of the physical and kinetic properties of this enzyme. MATERIALS AND METHODSBacterial strains and culture conditions. P. denitrificans (ATCC 13543) was grown aerobically at 30°C in the medium of Kornberg and Morris (23), supplemented with 0.05% NaHCO3, 0.01% yeast extract, and 0.5% methylamine, 0.5% methanol, or 0.3% succinate.Preparation of proteins. Methylamine dehydrogenase was purified from the periplasmic fraction of methylamine-grown cells, which was prepared by the method of Alefounder and Ferguson (1). Routinely, 15 to 20 g (wet weight) of cells was * Corresponding author. fractionated at a time, and four such preparations were pooled, concentrated by ultrafiltration over an Amicon YM5 membrane (Amicon Corp., Lexington, Mass.), dialyzed against 20 mM potassium phosphate (pH 7.2), and applied to a DEAE-cellulose column (3.5 by 30 cm) which had been equilibrated in the same buffer that was used for dialysis. This column was eluted with a linear gradient (2.0 liters) of 0 to 400 mM NaCl in the starting buffer. Fractions containing methylamine dehydrogenase were pooled, concentrated by ultrafiltration over an Amicon PM 30 membrane, dialyzed against 20 mM potassium phosphate (pH 7.2), and applied to a DEAE-Trisacryl (LKB Instruments, Inc., Rockville, Md.) column...

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It is concluded that DTI abnormalities in the regions of CC were more in patients with moderate TBI compared to mild TBI and this was associated with relatively poor neuropsychological outcome 6 months post-injury.