Cellular translocation of proteins by transportan

Abstract

The expression of the mitochondrially encoded subunit I of cytochrome-c oxidase (COX I) was investigated in cell cultures from patients with various mitochondrial diseases. Cells, grown on coverslips, were immunostained fluorescent green for the presence of COX I, while the mitochondria were co-stained fluoresent red with MitoTracker and the nuclei fluoresent blue with DAPI. Cell cultures expressing mitochondrial DNA depletion or harbouring heteroplasmic mutations in mitochondrial tRNA genes showed an intercellular mosaic staining for COX I. To analyse the results more objectively, we have developed a fully automated cytometric analysis system. The three fluorescent images of each field are captured using a low light level camera mounted on a fluorescence microscope which is fitted with a filter wheel with three excitation filters and a triple band pass emission filter. The system is used to scan 100 fields containing potentially thousands of cells. Sets of integrated images are processed to clearly define cell boundaries and to produce a binary mask image of the mitochondria. The fluorescent blue image (nuclear DNA) is utilised to define and separate individual cells. The system gave statistical credence to our earlier conclusions based on manual examination of the slides. In addition, image analysis showed a positive correlation between the intensity of COX I and MitoTracker staining (transmembrane electrical potential), and can be used to study organelle morphology. Measuring Betaine Metabolites Biochemistry Unit,Canterbury Health L.aboratories,Private Bag 151, ' 295 M . B . W . J . Dellow, M. Lever, C.M. Hayman Christchwrch, New ZeakandHomocysteine (hcy), a circulating non-protein amino acid is an independent risk factor for cardiovascular disease. Hcy is an intermediate in the metabolism of the essential amino acid methionine, a protein amino acid and precursor to S-adenosylmethionine (SAM). Methylation of hcy to methionine occurs by one of nvo pathways, a folate and B 12 (cobalamin) dependent pathway, or alternatively by methyl transfer from glycine betaine, mediated by betaine-homocysteine methyltransferase (BHMT), producing N,Ndimethylglycine. N,N-Dimethylglycine is a feedback inhibitor of BHMT and is broken down to glycine in a folate dependent pathway. The observation that elevation of N,N-dimethylglycine correlates with high hcy concentration led us to develop more sensitive and accurate methods to measure N,N-dimethylglycine and related betaine metabolites in plasma and urine samples.High performance liquid chromatography methods satisfy the requirements to measure N,N-dimethylglycine. Natural betaines are alkylated at the carboxyl terminal forming an ester using phenacyl triflates, in a base catalysed reaction. N,N-Dimethylglycine is derivatised at both the carboxyl and tertiary amine functions, producing a quaternary ammonium. Six derivatising agents have been tested with the greatest success shown by naphthacyl trifluoromethanesulphonate and 2-fluorenacyltrifluoromethanesulphonate respectively. A s...

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