Modeling of antigenomic therapy of mitochondrial diseases by mitochondrially addressed RNA targeting a pathogenic point mutation in mitochondrial DNA

Defects in mitochondrial genome can cause a wide range of clinical disorders, mainly neuromuscular diseases. Presently, no efficient therapeutic treatment has been developed against this class of pathologies. Because most of deleterious mitochondrial mutations are heteroplasmic, meaning that wild type and mutated forms of mitochondrial DNA (mtDNA) coexist in the same cell, the shift in proportion between mutant and wild type molecules could restore mitochondrial functions. Recently, we developed mitochondrial RNA vectors that can be used to address anti-replicative oligoribonucleotides into human mitochondria and thus impact heteroplasmy level in cells bearing a large deletion in mtDNA. Here, we show that this strategy can be also applied to point mutations in mtDNA. We demonstrate that specifically designed RNA molecules containing structural determinants for mitochondrial import and 20-nucleotide sequence corresponding to the mutated region of mtDNA, are able to anneal selectively to the mutated mitochondrial genomes. After being imported into mitochondria of living human cells in culture, these RNA induced a decrease of the proportion of mtDNA molecules bearing a pathogenic point mutation in the mtDNA ND5 gene

Correction of the consequences of mitochondrial 3243A>G mutation in the MT-TL1 gene causing the MELAS syndrome by tRNA import into mitochondria

Mutations in human mitochondrial DNA are often associated with incurable human neuromuscular diseases. Among these mutations, an important number have been identified in tRNA genes, including 29 in the gene MT-TL1 coding for the tRNALeu(UUR). The m.3243A>G mutation was described as the major cause of the MELAS syndrome (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes). This mutation was reported to reduce tRNALeu(UUR) aminoacylation and modification of its anti-codon wobble position, which results in a defective mitochondrial protein synthesis and reduced activities of respiratory chain complexes. In the present study, we have tested whether the mitochondrial targeting of recombinant tRNAs bearing the identity elements for human mitochondrial leucyl-tRNA synthetase can rescue the phenotype caused by MELAS mutation in human transmitochondrial cybrid cells. We demonstrate that nuclear expression and mitochondrial targeting of specifically designed transgenic tRNAs results in an improvement of mitochondrial translation, increased levels of mitochondrial DNA-encoded respiratory complexes subunits, and significant rescue of respiration. These findings prove the possibility to direct tRNAs with changed aminoacylation specificities into mitochondria, thus extending the potential therapeutic strategy of allotopic expression to address mitochondrial disorders

MITOCHONDRIAL DYSFUNCTION AS POSSIBLE CAUSE OF IMPAIRED FOLLICULAR DEVELOPMENT

Mitochondria play leading role in senescence program realization. One of the early manifestations of this process is loss of reproductive function in female (menopause). In this review we discuss up-to-date data on basic mitochondria functions and their possible role in development of premature ovarian insufficienсy and morbid conditions associated with this state, that are typical for ageing organism. Besides performing function of conversion of free energy by cell respiration substrates oxidation mitochondria control survival and death of somatic cells and gametes maintaining optimal level of reactive oxygen species in cells. Oxidative stress results in selective death of specialized cells; organs and tissues functionality disturbance; leads to development of cardiovascular, locomotor and nervous disorders. The main reason of oxidative stress is mitochondrial disfunction induced by disbalance between reactive oxygen species production and their utilization by antioxidant system. On the other hand mitochondria play central role in intracellular signal transmission and maintain functional state and cellular structure of tissues, organs and systems of an organism controlling cell proliferation, differentiation and apoptosis. Finally mitochondria define largely immune response in case of infections and tumoral transformation and control sex hormones level taking part in steroidogenesis. It was found that high level of damaged mitochondrial DNA, decrease of its copy number and increase of reactive oxygen species production in ovarian tissue cells are typical for women suffering from premature ovarian insufficienсy. Chronic oxidative stress leads not only to oogenesis disturbance and decrease of oocyte maturation probability but promotes also cardiovascular diseases, osteoporosis and other delayed consequences of estrogen deficit development in case of this state

Streamball techniques for flow visualization

The authors introduce the concept of streamballs for fluid flow visualization. Streamballs are based upon implicit surface generation techniques adopted from the well-known metaballs. Their property to split or merge automatically in areas of significant divergence or convergence makes them an ideal tool for the visualization of arbitrary complex flow fields. Using convolution surfaces generated by continuous skeletons for streamball construction offers the possibility to visualize even tensor fields. (orig.)SIGLEAvailable from TIB Hannover: RN 7281(244) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Complete tree-level calculation of the reaction e"+e"-#->##mu#"+#mu#"-b anti b and the Higgs boson signal at LEP200 and NLC energies

A complete tree-level calculation of the reaction e"+e"-#->##mu#"+#mu#"-b anti b in the electroweak standard theory for the energy range of LEP200 and the Next Linear Collider is presented. The matrix elements have been calculated by employing the computer program CompHEP, the phase space integrals by the Monte Carlo integrator and event generator BASES/SPRING. The dependence of the 4-fermion cross section on energy, Higgs boson mass and Higgs width is studied in detail. Interference contributions between the various diagrams are found not to alter significantly the production and decay distributions of the Higgs boson. It is shown that already the counting rate of the reaction e"+e"-#->##mu#"+#mu#"-b anti b at LEP200 can provide evidence for the existence of the Higgs boson. The dependence of the #mu#"+#mu#"-b anti b cross section on the Higgs width will allow to extract information on this width in particular at LEP200 energies. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(93-089) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Standard model Higgs search in the reactions e"+e"-#-># b anti b + 2 fermions at LEPII and NLC energies

A brief review of a complete tree-level Standard Model calculation of the reactions e"+e"-#->#b anti b+2 fermions in the enrgy range of LEPII and the Next e"+e"- Linear Collider is presented. Cross sections of the Higgs boson, the total background and important subsets of background are shown as a function of the center-of-mass energy. Properties of the Higgs signal and its extraction from background are discussed. (orig.)15 refs.SIGLEAvailable from TIB Hannover: RA 2999(96-007) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman