• The Korean Journal of Physiology and Pharmacology
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• v.16 no.1
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• pp.71-77
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• 2012

Mitochondrial dynamics and distribution is critical for their role in bioenergetics and cell survival. We investigated the consequence of altered fission/fusion on mitochondrial function and motility in INS-1E rat clonal ${\beta}$-cells. Adenoviruses were used to induce doxycycline-dependent expression of wild type (WT-Mfn1) or a dominant negative mitofusin 1 mutant (DN-Mfn1). Mitochondrial morphology and motility were analyzed by monitoring mitochondrially-targeted red fluorescent protein. Adenovirus-driven overexpression of WT-Mfn1 elicited severe aggregation of mitochondria, preventing them from reaching peripheral near plasma membrane areas of the cell. Overexpression of DN-Mfn1 resulted in fragmented mitochondria with widespread cytosolic distribution. WT-Mfn1 overexpression impaired mitochondrial function as glucose- and oligomycin-induced mitochondrial hyperpolarization were markedly reduced. Viability of the INS-1E cells, however, was not affected. Mitochondrial motility was significantly reduced in WT-Mfn1 overexpressing cells. Conversely, fragmented mitochondria in DN-Mfn1 overexpressing cells showed more vigorous movement than mitochondria in control cells. Movement of these mitochondria was also less microtubule-dependent. These results suggest that Mfn1-induced hyperfusion leads to mitochondrial dysfunction and hypomotility, which may explain impaired metabolism-secretion coupling in insulin-releasing cells overexpressing Mfn1.

• Journal of Microbiology and Biotechnology
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• v.23 no.11
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• pp.1627-1635
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• 2013

Mitochondria often play central roles in apoptotic pathways, and disruption of the mitochondrial transmembrane potential (${\Delta}{\psi}m$) has been observed in various cells undergoing apoptosis. Human cytomegalovirus (HCMV) infection induces apoptosis in permissive cells; however, investigations of mitochondria-targeted apoptosis in HCMV-infected human foreskin fibroblast (HFF) cells have been limited. Here, we investigated the mitochondrial apoptosis pathway in HCMV-infected HFF cells. Flow cytometry analysis using JC-1 revealed that HCMV infection induces disruption of ${\Delta}{\psi}m$ in HFF cells when administered 24 h post-infection (hpi), and this disruption was maximized at 48 hpi. Moreover, cytochrome c, normally a mitochondrial inner membrane protein, was detected in cytoplasmic extracts of HCMV-infected cells, but not mock-infected cells, by western blot analysis at 24 hpi. A caspase activity assay based on fluorescence spectrophotometry using a fluorogenic substrate revealed an increase in caspase-3 activity at 48 hpi in HCMV-infected cells. Caspase-8 activity was increased at 72 hpi in HCMV-infected cells. These results imply that HCMV infection induces mitochondria-mediated apoptosis in HFF cells.

• Journal of Environmental Health Sciences
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• v.23 no.3
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• pp.91-101
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• 1997

The biosynthesis of phospholipid and the composition of fatty acid in C. ellipsoidea mitochondria treated with antibiotics(cycloheximide, nalidixic acid) during the culture analyzed. The growth of Chlorella and the contents of total lipid in mitochondria treated with antibiotics were lower than those of the control. The synthesis of PC (phosphatidylcholine) and PI(phosphatidylinostiol) were inhibited in the nalidixic acid treatment and also the contents of PC(phosphatidylcholine), PE (phosphatidylethanolamine), PG(phosphatidylglycerol) and PI(phosphatidylinositol) in the cycloheximide treatment were also inhibited. The major fatty acids utilized for the various phospholipids formation in each antibiotics treatment were analyzed stearic acid, myristic acid, palmitic acid, oleic acid, linoleic acid and linolenic acid at the late phase of the culture.

• BMB Reports
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• v.40 no.6
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• pp.1095-1099
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• 2007

Endonuclease G (EndoG) is a mitochondrial non-specific nuclease that is highly conserved among the eukaryotes. Although the precise role of EndoG in mitochondria is not yet known, the enzyme is released from the mitochondria and digests nuclear DNA during apoptosis in mammalian cells. Schizosaccharomyces pombe has an EndoG homolog Pnu1p (previously named SpNuc1) that is produced as a precursor protein with a mitochondrial targeting sequence. During the sorting into mitochondria the signal sequence is cleaved to yield the functionally active endonuclease. From the analogy to EndoG, active extramitochondrial Pnu1p may trigger cell killing by degrading nuclear DNA. Here, we tested this possibility by expressing a truncated Pnu1p lacking the signal sequence in the extramitochondrial region of pnu1-deleted cells. The truncated Pnu1p was localized in the cytosol and nuclei of yeast cells. And ectopic expression of active Pnu1p led to cell death with fragmentation of nuclear DNA. This suggests that the Pnu1p is possibly involved in a certain type of yeast cell death via DNA fragmentation. Although expression of human Bak in S. pombe was lethal, Pnu1p nuclease is not necessary for hBak-induced cell death.

• Animal cells and systems
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• v.2 no.4
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• pp.529-538
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• 1998

In order to analyze the intracellu1ar localization of specific RNA components of ribonucleoproteins (RNP) in Xenopus oocytes, a modified protocol of whole-mount in situ Hybridization is presented in this paper, Mitochondria specific 12S rRNA probe was used to detect the amplification and distribution of mitochondria in various stages of the oocyte life cycle, and the results were found to be consistent with previously known distribution of mitochondria. The results with other specific probes (U1 and U3 small nuclear RNAs, and 5S RNA) also indicate that this procedure is generally effective in localizing RNAs in RNP complexes even inside organelles. In addition, the RNA component of RNase MRP, the RNP with endoribo-nuclease activity, localize to the nucleus in various stages of the oocyte life cycle. Some of MRP RNA, however, were found to be localized to the special population of mitochondria near the nucleus, especially in the active stage of mitochondrial amplification. It suggests dual localization of RNase MRP in the nucleus and mitochondria, which is consistent with the proposed roles of RNase MRP in mitochondrial DNA replication and in rRNA processing in the nucleolus.

• Applied Microscopy
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• v.17 no.1
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• pp.29-46
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• 1987

To study hexavalent chromium effects on mitochondrial electron transport, the activities of electron transport enzymes and conformational change of mitochondria treated with $40{\mu}M$ of sodium dichromate ($Na_{2}Cr_{2}O_{7}\;2H_{2}O$) were investigated. And so were those of liver mitochondria isolated from mouse intraperitoneally injected with sodium dichromate, 40mg per kg body weight. On both treatment with chromium(VI), the activities of electron transfer enzymes (Complex I and IV) were increased to some extent and the ultrastructural transformation of mitochondria from a condensed to an orthodox conformation was inhibited under State IV respiration. These results represent' inhibitory effect of hexavalent chromium on electron transport without inhibiting electron transfer enzymes (Complex I and IV) in mitochondria. On intraperitoneal treatment with hexavalent chromium as sodium dichromate and trivalent chromium as chromic chloride, containing 37.5 mg of chromium per kg body weight, respectively, the activities of electron transfer enzymes of liver isolated from mouse with chromium(VI) was reduced, but that with chromium(III) was not affected. And with chromium(VI), all mice after 12 hours of treatment died, only after 6 hours survived. With chromium(III), however, all survived. This indicates that hexavalent chromium is more toxic than trivalent chromiumin mouse liver.

• Biomolecules & Therapeutics
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• v.10 no.3
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• pp.152-158
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• 2002

The present study elucidated the effect of $\beta$-carbolines (harmaline and harmalol) on brain mitochondlial dysfunction caused by the tyrosinase-induced oxidation of dopamine. Harmaline, harmalol and antioxidant enzymes (SOD and catalase) attenuated the dopamine-induced alteration of membrane potential, cytochrome c release and thiol oxidation in mitochondria. In contrast, antioxidant enzymes failed to reverse mitochondrial dysfunction induced by dopmnine plus tyrosinase. $\beta$-Carbolines decreased the damaging effect of dopamine plus tyrosinase against mitochondria, except no effect of harmalol on thiol oxidation. Antioxidant enzymes decreased the melanin formation from dopamine in the reaction mixture containing mitochondria but did not reduce the formation of dopamine quinone caused by tyrosinase. Both harmalol and harmaline inhibited the formation of reactive quinone and melanin. Harmalol being more effective for quinone formation and vise versa. The results indicate that compared to MAO-induced dopamine oxidation, the toxic effect of dopamine in the presence of tyrosinase against mitochondria may be accomplished by the dopamine quinone and toxic substances other than reactive oxygen species. $\beta$-Carbolines may decrease the dopamine plus tyrosinase-induced brain mitochondrial dysfunction by inhibition of the formation of reactive quinone and the change in membrane permeability.

• Applied Microscopy
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• v.25 no.1
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• pp.111-121
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• 1995

The ultrastructure of spermatozoa in Hynobius leechii was examined with transmission electron microscope and compared with those of other urodeles and anurans. The perforatorium and the tail show most of the common feature of urodeles. However, there were several ultrastructural characteristics in an acrosome, nucleus, neck, axial rod and mitochondria related to the nucleus. The acrosome was trifoliate in transverse sections and the perforatorium consisted of two different concentric parts with a fine sharp point in a subacrosomal lumen. The nucleus consisted of two different regions of chromatin area and nuclear ridge. The nuclear ridge was composed of several bundles of five to ten minute tubular subunits of 19 nm diameter in this species, while in higher urodeles it was well developed in multi layers. The protoplasmic bead was separated by a cytoplasmic canal except the connection with only the distal portion of the nucleus. The neck was a short cylinder and contained pericentriolar material with transverse striations. In Hynobius the ring was not elongated to the tail and the mitochondria were distributed only in the protoplasmic bead around the nucleus as in Cryptobranchus, while in higher groups of urodeles it elongates to the length of the middle piece and the mitochondria follow the ring. The ring elongation may be related to the distribution of mitochondria. Hynobiidae and Cryptobranchidae are closely related based on structure of neck, the axial rod and location of mitochondria, although they are different in the composition of the axial rod.

• Animal cells and systems
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• v.14 no.2
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• pp.91-98
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• 2010

Male rats were given a single injection of iron, and temporal changes in iron content and iron-induced effects were examined in heart cellular fractions. Over a period of 72 h, the contents of total and labile iron, reactive oxygen species, and NO in tissue homogenate, nuclear debris, and postmitochondrial fractions were mostly constant, but in mitochondria they continuously increased. An abrupt decrease in membrane potential and NAD(P)H at 12 h was also found in mitochondria. The respiratory control ratio was reduced slowly with a slight recovery at 72 h, suggesting uncoupling by iron.While the ATP content of tissue homogenate decreased steadily until 72 h, it showed a prominent increase in mitochondria at 12 h. Total iron and calcium concentration also progressively increased in mitochondria over 72 h. Enzyme activity of the oxidative phosphorylation system was significantly altered by iron injection: activities of complexes I, III, and IV were reduced considerably, but complex II activity and the ATPase activity of complex V were enhanced. A reversal of activity in complexes I and II at 12 h suggested reverse electron transfer due to iron overload. These results support the argument that mitochondrial activities including oxidative phosphorylation are modulated by excessive iron.

• Animal cells and systems
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• v.7 no.1
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• pp.1-9
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• 2003

Programmed cell death, or apoptosis, is one of the most studied areas of modern biology. Apoptosis is a genetically regulated process, which plays an essential role in the development and homeostasis of higher organisms. Mitochondria, known to play a central role in regulating cellular metabolism, was found to be critical for regulating apoptosis induced under both physiological and pathological conditions. Mitochondria are a major source of reactive oxygen species (ROS) but they can also serve as its target during the apoptosis process. Release of apoptogenic factors from mitochondria, the best known of which is cytochrome c, leads to assembly of a large apoptosis-inducing complex called the apoptosome. Cysteine pretenses (called caspases) are recruited to this complex and, following their activation by proteolytic cleavage, activate other caspases, which in turn target for specific cleavage a large number of cellular proteins. The redox regulation of apoptosis during and after cytochrome c release is an area of intense investigation. This review summarizes what is known about the biological role of ROS and its targets in apoptosis with an emphasis on its intricate connections to mitochondria and the basic components of cell death.