Molecular Characterization of Segments S7 to S10 of a Southern Rice Black-streaked Dwarf Virus Isolate from Maize in Northern China

Southern rice black-streaked dwarf virus (SRBSDV) is a novel Fijivirus prevalent in rice in southern and central China,and northern Vietnam. Its genome has 10 segments of double-stranded RNA named S1 to S10 according to their size. An isolate of SRBSDV,JNi4,was obtained from naturally infected maize plants from Ji'ning,Shandong province,in the 2008 maize season. Segments S7 to S10 of JNi4 share nucleotide identities of 72.6%-73.1%,72.3%-73%,73.9%-74.5% and 77.3%-79%,respectively,with corresponding segments of Rice black-streaked dwarf virus isolates,and identities of 99.7%,99.1%-99.7%,98.9%-99.5%,and 98.6%-99.2% with those of SRBSDV isolates HN and GD. JNi4 forms a separate branch with GD and HN in the phylogenetic trees constructed with genomic sequences of S7 to S10. These results confirm the proposed taxonomic status of SRBSDV as a distinct species of the genus Fijivirus and indicate that JNi4 is an isolate of SRBSDV. Shandong is so far the northernmost region where SRBSDV is found in China.

Panax quinquefolium saponin attenuates cardiomyocyte apoptosis induced by thapsigargin through inhibition of endoplasmic reticulum stress

Background Endoplasmic reticulum （ER） stress-related apoptosis is involved in the pathophysiology of many cardiovascular diseases, and Panax quinquefolium saponin （PQS） is able to inhibit excessive ER stress-related apoptosis of cardiomyocytes following hypoxia/reoxygenation and myocardial infarction. However, the pathway by which PQS inhibits the ER stress-related apoptosis is not well understood. To further investigate the protective effect of PQS against ER stress-related apoptosis, primary cultured eardiomyocytes were stimulated with thapsigargin （TG）, which is widely used to model cellular ER stress, and it could induce apoptotic cell death in sufficient concentration. Methods Primary cultured cardiomyocytes from neonatal rats were exposed to TG （1 μmol/L） treatment for 24 h, following PQS pre-treatment （160 μg/mL） for 24 h or pre-treatment with small interfering RNA directed against protein kinase-like endoplasmic reticulum kinase （Si-PERK） for 6 h. The viability and apoptosis rate of cardiomyocytes were detected by cell counting kit-8 and flow cytometry respectively. ER stress-related protein expression, such as glucose-regulated protein 78 （GRP78）, calreticulin, PERK, eukaryotic translation initiation factor 2α （elF2c0, activating transcription factor 4 （ATF4）, and C/EBP homologous protein （CHOP） were assayed by western blotting. Results Both PQS pre-treatment and PERK knockdown remarkably inhibited the cardiomyocyte apoptosis induced by TG, increased cell viability, decreased phosphorylation of both PERK and eIF2α, and decreased protein levels of both ATF4 and CHOP. There was no statistically significant difference between PQS pre-treatment and PERK knockdown in the cardioprotective effect. Conclusions Our data indicate that the PERK-eIF2α-ATF4-CHOP pathway of ER stress is involved in the apoptosis induced by TG, and PQS might prevent TG-induced cardiomyocyte apoptosis through a mechanism involving the suppression of this pathway. These findings provide novel data regarding the molecular mechanisms by which PQS inhibits cardiomyocyte apoptosis.

Calreticulin Translocation Aggravates Endoplasmic Reticulum Stress-associated Apoptosis during Cardiomyocyte Hypoxia/Reoxygenation

Background： Calreticulin （CRT） is major Ca^2＋-binding chaperone mainly resident in the endoplasmic reticulum （ER） lumen. Recently, it has been shown that non-ER CRT regulates a wide array of cellular responses. We previously found that CRT was up-regulated during hypoxia/ reoxygenation （H/R） and this study was aimed to investigate whether CRT nuclear translocation aggravates ER stress （ERS）-associated apoptosis during H/R injury in neonatal rat cardiomyocytes. Methods： Apoptosis rate and lactate dehydrogenase （LDH） leakage in culture medium were measured as indices of cell injury. lmmunofluorescence staining showed the morphological changes of ER and intracellular translocation of CRT. Western blotting or reverse transcription polymerase chain reaction was used to detect the expression of target molecules. Results： Compared with control, H/R increased apoptosis rate and LDH activity. The ER became condensed and bubbled, and CRT translocated to the nucleus. Western blotting showed up-regulation of CRT, Nrf2, activating transcription factor 4 （ATF4）, CHOP and caspase-12 expression after H/R. Exogenous CRT overexpression induced by plasmid transfection before H/R increased cell apoptosis, LDH leakage, ER disorder, CRT nuclear translocation and the expression of ERS-associated molecules. However, administration of the ERS inhibitor, taurine, or CRT siRNA alleviated cell injury, ER disorder, and inhibited ERS-associated apoptosis. Conclusions： Our results indicated that during H/R stress, CRT translocation increases cell apoptosis and LDH leakage, aggravates ER disorder, up-regulates expression of nuclear transcription factors, Nrf2 and ATF4, and activates ERS-associated apoptosis.

Brain-Derived Glia Maturation Factor b Participates in Lung Injury Induced by Acute Cerebral Ischemia by Increasing ROS in Endothelial Cells

Brain damage can cause lung injury. To explore the mechanism underlying the lung injury induced by acute cerebral ischemia(ACI), we established a middle cerebral artery occlusion(MCAO) model in male Sprague-Dawley rats. We focused on glia maturation factor b(GMFB) based on quantitative analysis of the global rat serum proteome.Polymerase chain reaction, western blotting, and immunofluorescence revealed that GMFB was overexpressed in astrocytes in the brains of rats subjected to MCAO. We cultured rat primary astrocytes and confirmed that GMFB was also up-regulated in primary astrocytes after oxygen-glucose deprivation(OGD). We subjected the primary astrocytes to Gmfb RNA interference before OGD and collected the conditioned medium(CM) after OGD.We then used the CM to culture pulmonary microvascular endothelial cells(PMVECs) acquired in advance and assessed their status. The viability of the PMVECs improved significantly when Gmfb was blocked. Moreover,ELISA assays revealed an elevation in GMFB concentration in the medium after OGD. Cell cultures containing recombinant GMFB showed increased levels of reactive oxygen species and a deterioration in the state of the cells.In conclusion, GMFB is up-regulated in astrocytes after ACI, and brain-derived GMFB damages PMVECs by increasing reactive oxygen species. GMFB might thus be an initiator of the lung injury induced by ACI.

Molecular dynamics study on surface formation and phase transformation in nanometric cutting of β-Sn

Atomic motion and surface formation in the nanometric cutting process ofβ-Sn are investigated using molecular dynamics(MD).A stagnation region is observed that changes the shape of the tool edge involved in nanometric cutting,resulting in a fluctuation in the cutting forces.It is found that single-crystal tin releases the high compressive stress generated under the tool pressure through slip and phase transformation.The tin transformation proceeds from aβ-Sn structure to a bct-Sn structure.The effects of the cutting speed,undeformed chip thickness(UCT)and tool edge radius on material removal are also explored.A better surface is obtained through material embrittlement caused by a higher speed.In addition,a smaller UCT and sharper tool edge help reduce subsurface damage.