甘蔗叶不同部位ATP酶活性细胞化学定位

甘蔗叶片,叶鞘和肥厚带韧皮部 ATP 酶活性定位于筛管、伴胞的质膜、内质网和某些伴胞细胞基质、小囊泡和发育成熟的液泡上;叶片韧皮部薄壁细胞、厚壁细胞和厚壁通道细胞质膜及小囊泡中亦显示有 ATP 水解产物;维管束鞘细咆与厚壁细胞或厚壁通道细胞所构成的细胞间隙上也存在有 ATP 酶活性反应产物沉淀。甘蔗叶片大、中、小三种维管束,从小维管束到大维管束,面向细胞间隙的细胞表面上的 ATP 酶活性逐渐增强,而维管束鞘细胞质膜上的 ATP 酶活性则趋于减弱;同一维管束内则以韧皮部细胞的 ATP 酶活性最强。维管束鞘细胞与叶肉细胞之间存在很多的胞间连丝,并表现出高的 ATP 酶活性。讨论了 ATP 酶活性的分布状态与叶肉细胞的光合产物向韧皮部运输的关系。     

Chloroplast and mitochondrial SSR help to distinguish allo-cytoplasmic male sterile types in cabbage (Brassica oleracea L. var. capitata)

The profiles of single sequence repeat (SSR) in six distinct allo-cytoplasmic male sterile (CMS) types of cabbage (Brassica oleracea L. var. capitata) were generated using 32 SSR primer pairs derived from the Arabidopsis thaliana chloroplast (cp) genome and another 21 SSR primers from the B. napus mitochondrial (mt) genome sequences. In total, 11 cpSSR and 4 mtSSR primers revealed polymorphism among the six cabbage CMS types, namely NigCMS, OguCMSR₁, OguCMSR₂, OguCMSR₃, OguCMSHY and PolCMS. Through cluster analysis, six cabbage CMS types could be unambiguously differentiated with just three sets of primers (ACP43, ACP47, mtSSR2). Analysis of the selected amplicon sequences showed high identity to that of the corresponding sequences in A. thaliana, B. rapa and B. napus. The aligned cluster analysis revealed that the polymorphism mainly included SSR number variation, single nucleotide polymorphism (SNP), and sequence insertion or deletion (InDel). Our results demonstrated that specific mitochondrial or chloroplast SSR analysis could be a feasible alternative means for cabbage CMS type identification.     

Simultaneous saccharification and fermentation of acid-pretreated corncobs with a recombinant Saccharomyces cerevisiae expressing beta-glucosidase

To reduce the cellobiose inhibition of exoglucanase and endogulcanase and enhance cellulose hydrolysis during simultaneous saccharification and fermentation (SSF), a beta-glucosidase encoding gene named BGL1 was cloned from Saccharomycopsis fibuligera and integrated into the chromosomal rDNA region of the Saccharomyces cerevisiae industrial strain NAN-27 producing NAN-227. Compared with the parental strain, which had no detectable activity, the beta-glucosidase specific activity in NAN-227 was 1.02 IU/mg of protein. When cellobiose was used as the sole carbon source in a shake-flask, NAN-227 consumed 6.2g/L of cellobiose and produced 3.3g/L of ethanol in 48 h. The yield was 0.532 g/g. The parent strain only consumed 1.92 g/L of cellobiose and no ethanol was detected. During the SSF of acid-pretreated corncobs NAN-227 produced 20 g/L of ethanol at 72 h, which was similar to the parent strain when 20IU of beta-glucosidase/g of substrate was added.     

帕金森病丘脑底核神经元的电活动特点

本研究探讨了帕金森病(Parkinson′s disease, PD)患者丘脑底核(subthalamic nucleus, STN)神经元电活动的特点及其与PD症状的关系. 35例PD患者在接受手术治疗的同时, 应用微电极细胞记录和EMG记录技术, 记录手术靶点STN及其周围结构神经元的电活动以及手术对侧肢体的EMG. 应用分析软件甄别单细胞电活动, 分析其特点及其与肢体EMG的关系. 结果表明, STN及其周围结构具有特征性放电活动.在36个记录针道中, 共发现436个STN神经元, 平均放电频率44.0±20.5 Hz. 其中, 56%的神经元呈不规则簇状放电; 15%呈紧张性放电; 29%呈规则的簇状放电, 其放电节律与肢体震颤的EMG高度一致(r2=0.66, P<0.01), 称之为震颤细胞. 在PD震颤型患者的STN中发现大量震颤细胞, 且80%位于STN中上部, 而在PD僵直型患者的STN中均发现与运动相关的细胞电活动. 本研究提示, 通过微电极记录技术可准确地判断STN的位置和范围; 与震颤活动相关的细胞放电和与运动相关细胞的放电与PD症状有内在关系; STN参与PD运动障碍的病理生理过程.     

Influence of chk1 and plk1 silencing on radiation- or cisplatin-induced cytotoxicity in human malignant cells

The G2/M checkpoint is an attractive pathway for targeting and sensitizing tumor cells to cancer treatment. Abrogation of the G2/M checkpoint by targeting molecules, such as checkpoint kinase 1 (chk1), increases DNA breakage and sensitizes tumor cells to anti-tumoral agents. However, most of the previously described G2/M abrogators are actually targeting the G2-M border checkpoints rather than mitotic checkpoints. This prompted us to test the effects of combined targeting of chk1 and a critical regulator of mitosis, polo-like kinase 1 (plk1). Chk1 and plk1 were found to be co-expressed in 70% of primary neoplastic tissues we examined. Asynchronized tumor cells were treated with different DNA damaging-agents to activate G1/S, S or G2/M checkpoints. Either chk1 or plk1-specific antisense oligodeoxynucleotides (ASODN) enhanced DNA damaging agent-induced apoptosis. When used in combination, however, chk1- plus plk1-specific ASODN failed to produce synergistic effects. Moreover, selective targeting of plk1 or chk1 in tumor xenografts of mice by oncolytic adenovirus mutants demonstrated potent anti-tumoral efficacy in the presence of low dose cisplatin. Again, combined targeting of chk1 and plk1 did not further enhance anti-tumoral efficacy. We concluded that combined targeting of chk1 and plk1 was not superior to either targeting chk1 or plk1 alone, which suggested that chk1 and plk1 silencing might overlap in their mechanism of action. Whether combined targeting of chk1 with other, more specific mitotic regulators would synergistically sensitize tumor to anti-neoplastic therapeutics needs to be further clarified. Qinglei Gao and Xiaoyuan Huang contributed equally to this work.     

FUNDC1 regulates mitochondrial dynamics at the ER–mitochondrial contact site under hypoxic conditions

In hypoxic cells, dysfunctional mitochondria are selectively removed by a specialized autophagic process called mitophagy. The ER–mitochondrial contact site (MAM) is essential for fission of mitochondria prior to engulfment, and the outer mitochondrial membrane protein FUNDC1 interacts with LC3 to recruit autophagosomes, but the mechanisms integrating these processes are poorly understood. Here, we describe a new pathway mediating mitochondrial fission and subsequent mitophagy under hypoxic conditions. FUNDC1 accumulates at the MAM by associating with the ER membrane protein calnexin. As mitophagy proceeds, FUNDC1/calnexin association attenuates and the exposed cytosolic loop of FUNDC1 interacts with DRP1 instead. DRP1 is thereby recruited to the MAM, and mitochondrial fission then occurs. Knockdown of FUNDC1, DRP1, or calnexin prevents fission and mitophagy under hypoxic conditions. Thus, FUNDC1 integrates mitochondrial fission and mitophagy at the interface of the MAM by working in concert with DRP1 and calnexin under hypoxic conditions in mammalian cells.     

Phytophthora capsici homologue of the cell cycle regulator SDA1 is required for sporangial morphology,mycelial growth and plant infection

SDA1 encodes a highly conserved protein that is widely distributed in eukaryotic organisms. SDA1 is essential for cell cycle progression and organization of the actin cytoskeleton in yeasts and humans. In this study, we identified a Phytophthora capsici orthologue of yeast SDA1, named PcSDA1. In P. capsici, PcSDA1 is strongly expressed in three asexual developmental states (mycelium, sporangia and germinating cysts), as well as late in infection. Silencing or overexpression of PcSDA1 in P. capsici transformants affected the growth of hyphae and sporangiophores, sporangial development, cyst germination and zoospore release. Phalloidin staining confirmed that PcSDA1 is required for organization of the actin cytoskeleton. Moreover, 4′,6‐diamidino‐2‐phenylindole (DAPI) staining and PcSDA1‐green fluorescent protein (GFP) fusions revealed that PcSDA1 is involved in the regulation of nuclear distribution in hyphae and sporangia. Both silenced and overexpression transformants showed severely diminished virulence. Thus, our results suggest that PcSDA1 plays a similar role in the regulation of the actin cytoskeleton and nuclear division in this filamentous organism as in non‐filamentous yeasts and human cells.     

低氧预处理对低氧／复氧心肌能量代谢的作用

目的：研究低氧预处理（HPC）对心肌的保护作用,方法：借助^31P－NMR图谱技术,在模拟Langendorff离体灌流大鼠心脏的正常生理条件下,跟踪心肌高能磷酸化合物含量的动态变化。结果：在30min低氧期,PCr、ATP相对含量及PCr/Pi值逐渐减小,但HPC组减小的速度比对照组慢;而在复氧期,HPC组能提高心肌高能磷酸化合物含量的恢复程度,特别是复氧初期,HPC组PCr 、ATP相对含量及PCr/Pi值立即有了恢复;在本实验中,HPC对pHi的改善不显著。结论：HPC能降低后续长时间低氧及复氧阶段的心肌能量代谢,对心肌的低氧／复氧损伤具有保护作用。