FDG-PET analysis and findings in amnesia resulting from hypoxia.

The assumptions underlying neuroimaging, and problems in its analysis and interpretation, are commonly underestimated in neuropsychology. The ways in which fluoro-deoxy-glucose (FDG) positron emission tomography (PET) data can be analysed are discussed. PET findings from four patients who had suffered severe amnesia, following episodes of acute hypoxia, are presented. These patients had shown evidence of medial temporal (hippocampal and parahippocampal) atrophy on MRI brain scans. The PET data were analysed in several different ways. The converging findings were that the patients showed bilateral thalamic hypometabolism, and there was also evidence of retrosplenial hypometabolism bilaterally. Cognitively, these patients performed most like other patients with medial temporal lesions, but the results indicate that structural lesions can have distal metabolic effects on structures elsewhere. These findings are interpreted in the light of neuroanatomical observations concerning parallel projections between medial temporal lobe structures and the thalamus, some of which pass via the retrosplenium.

Cloning, expression, and properties of the regulatory subunit of bovine pyruvate dehydrogenase phosphatase.

cDNA encoding the regulatory subunit of bovine mitochondrial pyruvate dehydrogenase phosphatase (PDPr) has been cloned. Overlapping cDNA fragments were generated by the polymerase chain reaction from bovine genomic DNA and from cDNA synthesized from bovine poly(A)+ RNA and total RNA. The complete cDNA (2885 base pairs) contains an open reading frame of 2634 nucleotides encoding a putative presequence of 31 amino acid residues and a mature protein of 847 residues with a calculated Mr of 95,656. This value is in agreement with the molecular mass of native PDPr (95,800 +/- 200 Da) determined by matrix-assisted laser desorption-ionization mass spectrometry. The mature form of PDPr was expressed in Escherichia coli as a maltose-binding protein fusion, and the recombinant protein was purified to near homogeneity. It exhibited properties characteristic of the native PDPr, including recognition by antibodies against native bovine PDPr, ability to decrease the sensitivity of the catalytic subunit to Mg2+, and reversal of this inhibitory effect by the polyamine spermine. A BLAST search of protein data bases revealed that PDPr is distantly related to the mitochondrial flavoprotein dimethylglycine dehydrogenase, which functions in choline degradation.