中东

Thomson Reuters 发布的全球系列研究报告表明,以阿拉伯、伊朗、土耳其为主的中东国家的科学研究与西文国家相比落后许多.当然,也有部分中东的科学家或研究机构从事着世界一流的研究工作.事实上,论文数量及引文指标都清晰地表明,近10年中东地区的研究工作有了很大的进步,表现出了鼓舞人心的发展趋势.     

Human embryonic stem cell lines derived from single blastomeres

The derivation of human embryonic stem (hES) cells currently requires the destruction of ex utero embryos. A previous study in mice indicates that it might be possible to generate embryonic stem (ES) cells using a single-cell biopsy similar to that used in preimplantation genetic diagnosis (PGD), which does not interfere with the embryo's developmental potential. By growing the single blastomere overnight, the resulting cells could be used for both genetic testing and stem cell derivation without affecting the clinical outcome of the procedure. Here we report a series of ten separate experiments demonstrating that hES cells can be derived from single blastomeres. In this proof-of-principle study, multiple biopsies were taken from each embryo using micromanipulation techniques and none of the biopsied embryos were allowed to develop in culture. Nineteen ES-cell-like outgrowths and two stable hES cell lines were obtained. The latter hES cell lines maintained undifferentiated proliferation for more than eight months, and showed normal karyotype and expression of markers of pluripotency, including Oct-4, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, nanog and alkaline phosphatase. These cells retained the potential to form derivatives of all three embryonic germ layers both in vitro and in teratomas. The ability to create new stem cell lines and therapies without destroying embryos would address the ethical concerns of many, and allow the generation of matched tissue for children and siblings born from transferred PGD embryos.     

Inactivation of the p53 pathway in retinoblastoma

Most human tumours have genetic mutations in their Rb and p53 pathways, but retinoblastoma is thought to be an exception. Studies suggest that retinoblastomas, which initiate with mutations in the gene retinoblastoma 1 (RB1), bypass the p53 pathway because they arise from intrinsically death-resistant cells during retinal development. In contrast to this prevailing theory, here we show that the tumour surveillance pathway mediated by Arf, MDM2, MDMX and p53 is activated after loss of RB1 during retinogenesis. RB1-deficient retinoblasts undergo p53-mediated apoptosis and exit the cell cycle. Subsequently, amplification of the MDMX gene and increased expression of MDMX protein are strongly selected for during tumour progression as a mechanism to suppress the p53 response in RB1-deficient retinal cells. Our data provide evidence that the p53 pathway is inactivated in retinoblastoma and that this cancer does not originate from intrinsically death-resistant cells as previously thought. In addition, they support the idea that MDMX is a specific chemotherapeutic target for treating retinoblastoma.     

Pregnenolone stabilizes microtubules and promotes zebrafish embryonic cell movement

Embryonic cell movement is essential for morphogenesis and the establishment of body shapes, but little is known about its mechanism. Here we report that pregnenolone, which is produced from cholesterol by the steroidogenic enzyme Cyp11a1 (cholesterol side-chain cleavage enzyme, P450scc), functions in promoting cell migration during epiboly. Epiboly is a process in which embryonic cells spread from the animal pole to cover the underlying yolk. During epiboly, cyp11a1 is expressed in an extra-embryonic yolk syncytial layer. Reducing cyp11a1 expression in zebrafish using antisense morpholino oligonucleotides did not perturb cell fates, but caused epibolic delay. This epibolic defect was partially rescued by the injection of cyp11a1 RNA or the supplementation of pregnenolone. We show that the epibolic delay is accompanied by a decrease in the level of polymerized microtubules, and that pregnenolone can rescue this microtubule defect. Our results indicate that pregnenolone preserves microtubule abundance and promotes cell movement during epiboly.     

Hepatic CDP-diacylglycerol synthase 2 deficiency causes mitochondrial dysfunction and promotes rapid progression of NASH and fibrosis

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies,ranging from steatosis to nonalcoholic steatohepatitis (NASH).The factors promoti...     

菜籽粕发酵脱毒的一些影响因素

报告了菜籽饼粕发酵脱毒的菌种复壮方法及脱毒辅助剂．应用芥子甙的酶分解产物异硫氰酸酯类，通过产物耐受性筛选法，获得提高了脱毒率的曲霉（Ａｓｐｅｒｇｉｌｕｓｓｐ．）菌株．从饲料添加剂中寻找到一种可增强发酵脱毒效果的脱毒助剂，并试验了影响发酵脱毒的各种因子．     

中国西南地区地壳运动的GPS监测

通过１９９１￣１９９７年期间对中国西南地区ＧＰＳ（全球定位系统）载波相位测量,建立了青藏高原东部及相邻地区现代地壳运动的速度场,相对于成都,川滇地块及其以西的速度大多为５￣１０ｍｍ／ａ,鲜水河－小江断裂以东的川青地块和扬子地块运动微弱,约为０￣７ｍｍ／ａ,２个地区都表现为顺时钟的涡旋运动,而没有明显的地壳物质向东挤出或逃逸,地壳变形主要型式为顺时针旋卷构造和块体边界断裂的非均一滑动。     

Selective antiproliferative effects of thymidine

A substance with antiproliferative bioactivity in an aqueous extract ofCordyline terminalis was purified and identified by mass spectrometry to be the natural nucleoside, thymidine. 10^–5M Thymidine inhibited EL4 cell replication and decreased cell viability after 12–24 h. The effect was highly specific for this nucleoside. Treated cell cultures showed a significant increase in S phase cells and a corresponding decrease in G₁ phase cells. Nitrobenzylthioinosine (which prevented facilitated entry of thymidine) protected cells from the antiproliferative action of thymidine. A human breast cancer cell line (MCF7) was also growth-inhibited by 10^–5M thymidine but a murine lymphoma cell line (K36) was not. Thus, submillimolar thymidine has effects on cell proliferation which are selective both with respect to specificity for the compound and for different tumour cell lines.