Search

Mitochondrial morphology was studied in cultivated myoblasts obtained from patients with mitochondrial disorders, including CPEO, MELAS and TMEM70 deficiency. Mitochondrial networks and ultrastructure were visualized by fluorescence microscopy and transmission electron microscopy, respectively. A heterogeneous picture of abnormally sized and shaped mitochondria with fragmentation, shortening, and aberrant cristae, lower density of mitochondria and an increased number of "megamitochondria" were found in patient myoblasts. Morphometric Fiji analyses revealed different mitochondrial network properties in myoblasts from patients and controls. The small number of cultivated myoblasts required for semiautomatic morphometric image analysis makes this tool useful for estimating mitochondrial disturbances in patients with mitochondrial disorders.

Mitochondrial respiratory chain enzyme Complexes are present in placenta at proportion similar to other tissues with exception of glycerophosphate dehydrogenase (mGPDH) which is expressed at a very high rate. As shown by Western blot quantification and respiratory chain enzyme activity measurements, the specific content of mGPDH is similar to that of succinate dehydrogenase or NADH dehydrogenase. Using fluorometric probe dichlorodihydrofluorescein diacetate we found that placental mitochondria display high rate of glycerophosphate-dependent hydrogen peroxide production. This was confirmed by oxygraphic detection of glycerophosphate-induced, KCN- or antimycin A-insensitive oxygen uptake. Hydrogen peroxide production by mGPDH was highly activated by one-electron acceptor, potassium ferricyanide and it was depressed by inhibitors of mGPDH and by cytochrome c. Our results indicate that mGPDH should be considered as an additional source of reactive oxygen species participating in induction of oxidative stress in placenta.

Leber hereditary optic neuropathy (LHON) is maternal ly inherited disorder characterized by subacute loss of vision due to impairment of retinal ganglion cel ls eventual ly lead ing to optic atrophy. Three prevalent point mutations in mitochondrial DNA: m.11778G>A, m.3460G>A, and m.14484T>C, are causative in the majority (> 95%) of cases. All of these mutations aff ect one of the subunits of complex I, NADH-ubiquinone oxidoreductase, the fi rst enzyme of the mitochondrial respiratory chain. The presence of a mutation is neces sary but not suffi cient to cause visual los s. The penetrance is incomplete with only about 50% of men and 10% of women event. develop ing clinical signs of the dis ease. Recently, it was proven that early initiation of ther apy with idebenone in patients manifest ing LHON ameliorates visual functions and clinical trials test ing several other promis ing ther apies are underway. Incomplete penetrance, similarites with other disorders affect ing the optic nerve and a great variability of clinical features cause considerable dia gnostic diffi culties. Often there is a delay in ther apy initiation, as late as in the phase of the ir reversible optic nerve damage. In 2013, we established a multidisciplinary medical care centre dedicated to patients with mitochondrial optic neuropathies in General University Hospital in Prague to develop eff ective diagnostic and treatment algorithms and to study the underlying pathogenetic mechanisms. [ABSTRACT FROM AUTHOR]