Dynamic changes of microtubule and actin structures in CV-1 cells during electrofusion

To study the involvement of the cytoskeletal system in the fusion of animal cells, we examined the dynamic changes of cytoskeletal proteins during the various stages of cell fusion. CV-1 cells were fused by applying a radio-frequency electrical pulse. Structural changes of microtubules (MTs) and F-actin were monitored simultaneously by double-label fluorescence microscopy. It was observed that in a few minutes after the initiation of cell fusion, MT bundles began to extend into the cytoplasmic bridges which were formed by fusing the membranes of neighboring cells. Later, a network of parallel MT bundles appeared between the adjacent nuclei of the fusing cells; such MT bundles may provide the mechanical links that are responsible for nuclear aggregation. The structural changes of F-actin during cell fusion were more complicated. We observed many different patterns of actin distribution in the fusing cells, including some giant, ring-shaped structures. Reorganization of actin is unlikely to be involved in the nuclear aggregation process. Instead, actin bundles condensed at the cell edges may help to widen the cytoplasmic bridges to allow merging of cellular contents between the fusing cells.     

Effects of hyperthermia and photodynamic therapy on BALB/c mice bearing subcutaneous tumors

The therapeutic effects of photodynamic therapy and hyperthermia on mice bearing subcutaneous tumors were investigated. Ehrlich ascites tumor cells (1 x 10(7)) were implanted subcutaneously into the femoral area of BALB/c mice. A total of 134 tumor-bearing mice were treated with photodynamic therapy, i.e., administration of laser irradiation (514.5 nm, 112.5 mW/cm2 for 11.12 min with a total energy 75 J/cm2) after injection (i.p.) of hematoporphyrin derivative (HPD, 7.5 and 10.0 mg/kg body weight) and/or hyperthermia (by electric heating needles to 44 and 45 degrees C for 30 min) once a day for three successive days. The results revealed that the therapeutic effects of the combination of photodynamic therapy and hyperthermia were improved when compared with photodynamic therapy or hyperthermia alone. A combination of photodynamic therapy (10.0 mg HPD/kg body weight and 75 J/cm2 of total laser irradiation energy) and hyperthermia (44 degrees C for 30 min) had the best therapeutic effect, indicating that the mortality rate within 120 days (MR120) was 12.5% and the mean survival time (MST120) was 113.8 days.     

Exposure to high glutamate concentration activates aerobic glycolysis but inhibits ATP‐linked respiration in cultured cortical astrocytes

Astrocytes play a key role in removing the synaptically released glutamate from the extracellular space and maintaining the glutamate below neurotoxic level in the brain. However, high concentration of glutamate leads to toxicity in astrocytes, and the underlying mechanisms are unclear. The purpose of this study was to investigate whether energy metabolism disorder, especially impairment of mitochondrial respiration, is involved in the glutamate‐induced gliotoxicity. Exposure to 10‐mM glutamate for 48 h stimulated glycolysis and respiration in astrocytes. However, the increased oxygen consumption was used for proton leak and non‐mitochondrial respiration, but not for oxidative phosphorylation and ATP generation. When the exposure time extended to 72 h, glycolysis was still activated for ATP generation, but the mitochondrial ATP‐linked respiration of astrocytes was reduced. The glutamate‐induced astrocyte damage can be mimicked by the non‐metabolized substrate d ‐aspartate but reversed by the non‐selective glutamate transporter inhibitor TBOA. In addition, the glutamate toxicity can be partially reversed by vitamin E. These findings demonstrate that changes of bioenergetic profile occur in cultured cortical astrocytes exposed to high concentration of glutamate and highlight the role of mitochondria respiration in glutamate‐induced gliotoxicity in cortical astrocytes. Copyright © 2014 John Wiley & Sons, Ltd.