462 research outputs found
Structural changes of mitochondria during free radical-induced apoptosis
The initial proposal for apoptosis stressed nuclear change (condensation of chromatin) and the intactness of intracellular organelles, including mitochondria, based on light and electron microscopic observations. However, data have accumulated to demonstrate that the opening of megachannels of mitochondrial membranes, resulting in the swelling of the organelles, notably by Ca 2+ and free radicals, is the crucial step in the apoptotic processes of the cell. Application of fluorescent dyes to mitochondria, combined with flow cytometry, has made it possible to detect subtle changes in the structure and function of the organelles related to apoptosis. The present article overviews structural aspects of mitochondria related to apoptosis, including the free radical-induced formation of megamitochondria
Kinetics of Iron Passivation Studied by Sub-Second Resolution Realtime X-ray Reflectivity Technique
Divergent effects of quinolinic aminoxyls on mitochondrial ultrastructure and localisation in osteosarcoma 143 B cells
In the present study we have shown that quinolinic aromatic aminoxyls are very
efficient in protecting lipids of endoplasmic reticulum membranes against hydroperoxide-
induced oxidation. The efficacy of these aminoxyls as protectors of lipids
was much higher than the water-soluble 4-OH-TEMPO. We have also shown that
QAL causes distinct changes of the morphology of mitochondria: from filamentous
to granular enlarged structure via the folding of the former. QAL induces also
perinuclear clustering of mitochondria. C-QAL as well as 4-OH-TEMPO treated
cells revealed filamentous and scattered pattern of mitochondria. Antioxidant activity
of QAL as well as morphological changes of mitochondrial raise the possibility
that this drug can affect cell physiology via changes of mitochondrial function
Design of engineered active zymogen of microbial transglutaminase
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Fast perinuclear clustering of mitochondria in oxidatively stressed human choriocarcinoma cells
Mitochondrial dysfunction plays a crucial role in cell types that exhibit necrosislike
death after activation of their death program. Tumour necrosis factor (TNF)
induces abnormal, perinuclear clustering of mitochondria from an evenly spread
distribution throughout the cytoplasm. The mitochondria withdraw from the
cell periphery and aggregate in a unipolar perinuclear cluster. TNF-induced mitochondrial
clustering is caused by impaired kinesin-mediated transportation of
mitochondria. In this report, we describe a novel activity of menadione (MEN),
namely the induction of an altered spatial distribution of mitochondria in the
choriocarcinoma JAR cells. Strikingly, 2 hours of cell exposition to menadione
did not disrupt the integrity of the plasma membrane, while the intracellular
ATP level significantly decreased. Control (untreated) cells displayed a typically
scattered distribution of filamentary mitochondria inside the cell. After 2 hours
of MEN treatment the spatial distribution of the mitochondria was markedly
altered to an asymmetric perinuclear clustered distribution. Menadione-stressed
cells displayed a highly asymmetrical perinuclear clustered distribution of the
mitochondria. The exposure of cells to MEN also results in a change in shape of
the mitochondria into a population of enlarged granular structures. The results
of our study demonstrate that in JAR cells menadione causes mitochondria to
translocate from the cell periphery into the perinuclear region several hours
before disruption of cell membrane integrity and cell death
Co-existence of apoptotic and necrotic features within one single cell as a result of menadione treatment
In the present study we examined the effects of menadione, a redox cycling
agent, on structural changes of human osteosarcoma line 143B cells. It has
been previously reported that menadione can cause necrotic or apoptotic cell
death in a concentration- depending manner. In our experimental model, cells
were treated with 100 μM menadione for 24 hours. Using electron microscopy
technique cells carrying three kinds of morphological changes were detected:
necrotic cells, apoptotic cells and those demonstrating a co-existence of apoptotic
and necrotic features in one single cell
Genotoxicity of nano/microparticles in in vitro micronuclei, in vivo comet and mutation assay systems
<p>Abstract</p> <p>Background</p> <p>Recently, manufactured nano/microparticles such as fullerenes (C<sub>60</sub>), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C<sub>60</sub>, CB and kaolin, an <it>in vitro </it>micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by <it>in vivo </it>assay systems using male C57BL/6J or <it>gpt </it>delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles.</p> <p>Results</p> <p>In <it>in vitro </it>genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C<sub>60</sub>, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C<sub>60 </sub>and kaolin, increased either or both of <it>gpt </it>and Spi<sup>- </sup>mutant frequencies in the lungs of <it>gpt </it>delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the <it>gpt </it>genes. The G:C to C:G transversion was commonly increased by these particle instillations.</p> <p>Conclusion</p> <p>Manufactured nano/microparticles, CB, C<sub>60 </sub>and kaolin, were shown to be genotoxic in <it>in vitro </it>and <it>in vivo </it>assay systems.</p
3-keto-5α-steroid-Δ4-dehydrogenase from Nocardia corallina: Purification and characterization
金沢大学自然科学研究科 金沢大学理工研究域自然システム学系The inducible 3-keto-5α-steroid-Δ4-dehydrogenase of Nocardia corallina was purified to homogeneity using affinity chromatography on 19-nortestosterone-17-acetoxyaminoethyl Sepharose 4B. SDS-polyacrylamide gel electrophoresis, gel filtration and spectral analysis of flavin suggest that the purified dehydrogenase is a monomeric protein of M(r) 60,000 containing one flavin. It has a typical absorption spectrum of flavoprotein with maxima at 457, 375, and 277 nm. The values shifted to 470 and 395 nm on binding of 19-nortestosterone. The enzyme catalyzed the dehydrogenation of 3-keto-5α-steroid at the 4- and 5-position, e.g. the conversion of 5α-androst-1-ene-3,17-dione to 1,4-androstadiene-3,17-dione with the reduction of phenazine methosulfate. The substrate 3-ketosteroid has essentially the 5α-configuration. The enzyme did not reduce potassium ferricyanide but did reduce cytochrome c at a moderate rate, and exhibited only a weak steroid oxidase activity. Stereochemical study demonstrated that the enzyme abstracts the 4β, 5α-hydrogens of the substrate as a hydrogen ion through a protein-based reaction and as a hydride ion by transfer to FAD, respectively. The enzyme oxidizes a wide variety of 3-keto-5α-steroids but not 3β-hydroxysteroid. The dehydrogenase also catalyzed steroid transhydrogenation between 3-keto-5α-steroid and 3-keto-1,4-diene-steroid. The properties of this enzyme are compared with those of 3-keto-steroid-Δ1-dehydrogenase
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