Axonal self-destruction and neurodegeneration

Neurons seem to have at least two self-destruct programs. Like other cell types, they have an intracellular death program for undergoing apoptosis when they are injured, infected, or not needed. In addition, they apparently have a second, molecularly distinct self-destruct program in their axon. This program is activated when the axon is severed and leads to the rapid degeneration of the isolated part of the cut axon. Do neurons also use this second program to prune their axonal tree during development and to conserve resources in response to chronic insults?     

Fetal alcohol syndrome: embryogenesis in a mouse model

When two small doses of ethanol were administered to pregnant mice during the gastrulation stage of embryogenesis, the embryos developed craniofacial malformations closely resembling those seen in the human fetal alcohol syndrome. Striking histological changes appeared in the developing brain (neuroectoderm) within 24 hours of exposure. Decreased development of the neural plate and its derivatives apparently accounts for the craniofacial malformations. The critical exposure period is equivalent to the third week in human pregnancy.     

Neurotoxicity and neurodegeneration when PrP accumulates in the cytosol

Changes in prion protein (PrP) folding are associated with fatal neurodegenerative disorders, but the neurotoxic species is unknown. Like other proteins that traffic through the endoplasmic reticulum, misfolded PrP is retrograde transported to the cytosol for degradation by proteasomes. Accumulation of even small amounts of cytosolic PrP was strongly neurotoxic in cultured cells and transgenic mice. Mice developed normally but acquired severe ataxia, with cerebellar degeneration and gliosis. This establishes a mechanism for converting wild-type PrP to a highly neurotoxic species that is distinct from the self-propagating PrP(Sc) isoform and suggests a potential common framework for seemingly diverse PrP neurodegenerative disorders.     

Vaccinia virus uses macropinocytosis and apoptotic mimicry to enter host cells

Viruses employ many different strategies to enter host cells. Vaccinia virus, a prototype poxvirus, enters cells in a pH-dependent fashion. Live cell imaging showed that fluorescent virus particles associated with and moved along filopodia to the cell body, where they were internalized after inducing the extrusion of large transient membrane blebs. p21-activated kinase 1 (PAK1) was activated by the virus, and the endocytic process had the general characteristics of macropinocytosis. The induction of blebs, the endocytic event, and infection were all critically dependent on the presence of exposed phosphatidylserine in the viral membrane, which suggests that vaccinia virus uses apoptotic mimicry to enter cells.     

运动对心肌细胞凋亡及相关基因表达的影响

通过研究不同运动强度对心肌细胞凋亡基因Bcl-2、Bax和Caspase-3的影响,探讨了运动对心肌细胞凋亡的作用机制。将大鼠分为3组(正常对照组、一般游泳有氧训练组和力竭性过度训练组)并建立运动模型;采用实时荧光定量PCR技术观察心肌细胞中凋亡基因Bcl-2、Bax和Caspase-3 mRNA的表达;采用Western blot方法观察Bcl-2、Bax、Caspase-3蛋白表达情况。结果显示,与对照组相比,一般游泳有氧训练组大鼠调控基因Bcl-2表达显著增加,对细胞的凋亡起到一定的抑制作用;而力竭过度训练组中心肌细胞相关调控基因Bcl-2表达下降,Bax、Caspase-3的表达升高促进凋亡。因此推定超负荷的运动会加重大鼠心肌细胞的凋亡,凋亡的发生可能与调控基因Bcl-2、Bax和Caspase-3有关。     

Autoimmune disease and impaired uptake of apoptotic cells in MFG-E8-deficient mice

Apoptotic cells expose phosphatidylserine and are swiftly engulfed by macrophages. Milk fat globule epidermal growth factor (EGF) factor 8 (MFG-E8) is a protein that binds to apoptotic cells by recognizing phosphatidylserine and that enhances the engulfment of apoptotic cells by macrophages. We report that tingible body macrophages in the germinal centers of the spleen and lymph nodes strongly express MFG-E8. Many apoptotic lymphocytes were found on the MFG-E8-/- tingible body macrophages, but they were not efficiently engulfed. The MFG-E8-/- mice developed splenomegaly, with the formation of numerous germinal centers, and suffered from glomerulonephritis as a result of autoantibody production. These data demonstrate that MFG-E8 has a critical role in removing apoptotic B cells in the germinal centers and that its failure can lead to autoimmune diseases.     

绿茶多酚诱导肝癌细胞凋亡时Caspase-3蛋白活性与mRNA的变化

[目的]研究绿茶多酚(EGCG)诱导肝癌细胞Hep-G2凋亡过程中半胱天冬酶-3(Caspase-3)蛋白活性与mRNA的变化。[方法]100 mg/L的EGCG处理Hep-G2细胞48 h,DAPI染色观察细胞形态学,用MTT检测EGCG对Hep-G2细胞生长的影响,流式细胞技术Annexin V-FITC PI法检测不同浓度EGCG诱导细胞的凋亡率,分光光度法检测Caspase-3的活性,用半定量RT-PCR法检测Caspase-3的mRNA变化。[结果]100 mg/L的EGCG作用Hep-G2细胞48 h后,荧光显微镜观察到细胞出现核碎裂和凋亡小体;MTT法检测到EGCG对肝癌细胞Hep-G2的生长均有显著抑制作用,呈浓度依赖性;Annexin V-FITC PI法检测到不同浓度的EGCG作用与肝癌细胞Hep-G2后,凋亡率较对照组明显升高,并随诱导浓度的增加而增加;不同浓度的EGCG处理组和不同时间EGCG处理组的Caspase-3活性和mRNA表达量均比对照组明显升高。[结论]Caspase-3蛋白活性与mRNA上调是EGCG诱导肝癌细胞凋亡的的重要原因和机制。     

Cannabis and alcohol: effects on stimulated car driving

The effects of cannabis and alcohol on simulated car driving were studied. Cannabis resin containing 4 percent Delta(1)-tetrahydrocannabinol was administered orally in three doses equivalent to 8, 12, and 16 milligrams of that component. Alcohol was given orally in one standard dose of 70 grams. Both cannabis and alcohol increased the time required to brake and start, whereas alcohol increased while cannabis decreased the number of gear changes. An effect of dosage on response was observed with cannabis.     

通过微量细胞鉴定快速生产基因编辑猪

目的建立快速筛选猪的基因编辑阳性成纤维细胞系的方法以提高利用体细胞核移植产生基因编辑克隆猪的效率。方法通过PCR、T7EN1酶切和Sanger测序分析不同数量的已知猪基因编辑阳性细胞(20、50、100、150和200个细胞)的基因型,确定最小细胞数用于鉴定未知的基因编辑阳性细胞系以证明该方法的可行性。结果除20细胞组外,其他所有细胞组中均扩增出2条明显的T7EN1酶切条带(175和555 bp)。定量数据显示：20细胞组和50细胞组之间的条带灰度值存在极显著差异(P<0.01),因此50细胞可用于基因编辑阳性细胞系鉴定。利用CRISPR/Cas9系统构建IPO13打靶载体,转染猪胎儿成纤维细胞形成细胞克隆点后计数50个细胞来筛选阳性细胞系,再通过体细胞核移植快速生产了IPO13敲除猪,从而证实通过微量细胞鉴定快速生产基因编辑猪的可行性。筛选基因编辑阳性细胞系的一般方法大约需要33.7 d,新建立的方法细胞筛选周期仅为18.9 d (减少15 d),获得阳性细胞系的成功率也提高了约4倍。结论本研究建立了一种通过微量细胞鉴定快速生产基因编辑克隆猪的方法,该方法可行可靠。     

Differential mortality by sex in fetal and neonatal deaths

Vital statistics data for the United States from 1922 to 1936 and from 1950 to 1972 were used to analyze fetal and early neonatal mortality. This analysis corroborates the previously established pattern of the sex ratio of fetal deaths--highest from months 3 to 5, lower from months 6 to 7 or 8, and increasing at term. It also indicates a postponement of late fetal deaths into the early infant period. Whereas earlier research reports have described the pattern of the sex ratio of fetal deaths, this report repeats this analysis for a recent national data base. This line of analysis is extended by using the patterns observed in the data to produce an empirical estimate of the primary sex ratio. For 1950 to 1972, this ratio (male to female) is conservatively estimated to be 120:100.     

Ubiquitin protein ligase activity of IAPs and their degradation in proteasomes in response to apoptotic stimuli

To determine why proteasome inhibitors prevent thymocyte death, we examined whether proteasomes degrade anti-apoptotic molecules in cells induced to undergo apoptosis. The c-IAP1 and XIAP inhibitors of apoptosis were selectively lost in glucocorticoid- or etoposide-treated thymocytes in a proteasome-dependent manner before death. IAPs catalyzed their own ubiquitination in vitro, an activity requiring the RING domain. Overexpressed wild-type c-IAP1, but not a RING domain mutant, was spontaneously ubiquitinated and degraded, and stably expressed XIAP lacking the RING domain was relatively resistant to apoptosis-induced degradation and, correspondingly, more effective at preventing apoptosis than wild-type XIAP. Autoubiquitination and degradation of IAPs may be a key event in the apoptotic program.     

从小桐子油提取分离醇溶性二萜的工艺研究

采用甲醇萃取的方法提取分离小桐子油中醇溶性二萜和脂肪酸;在确定萃取温度和搅拌速率的基础上,探讨了液液比(甲醇/小桐子油)、搅拌时间和提取次数对二萜提取率的影响,分析了冷冻温度和时间与脂肪酸分离的关系;并建立了紫外分光光度法测定小桐子油中二萜的含量的方法。结果表明:当萃取温度30℃,搅拌速率120 r/min,搅拌时间20 min,萃取次数为4次,4次液液比(甲醇/小桐子油)依次为2.5、2.0、1.5和1.0时,萃取效率最佳。