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.     

Embryonic and extraembryonic stem cell lines derived from single mouse blastomeres

The most basic objection to human embryonic stem (ES) cell research is rooted in the fact that ES cell derivation deprives embryos of any further potential to develop into a complete human being. ES cell lines are conventionally isolated from the inner cell mass of blastocysts and, in a few instances, from cleavage stage embryos. So far, there have been no reports in the literature of stem cell lines derived using an approach that does not require embryo destruction. Here we report an alternative method of establishing ES cell lines-using a technique of single-cell embryo biopsy similar to that used in pre-implantation genetic diagnosis of genetic defects-that does not interfere with the developmental potential of embryos. Five putative ES and seven trophoblast stem (TS) cell lines were produced from single blastomeres, which maintained normal karyotype and markers of pluripotency or TS cells for up to more than 50 passages. The ES cells differentiated into derivatives of all three germ layers in vitro and in teratomas, and showed germ line transmission. Single-blastomere-biopsied embryos developed to term without a reduction in their developmental capacity. The ability to generate human ES cells without the destruction of ex utero embryos would reduce or eliminate the ethical concerns of many.     

Establishment and cryopreservation of liver, heart and muscle cell lines derived from the Chinese alligator （Alligator sinensis）

The Chinese alligator, Alligator sinensis, is a critically endangered species. A conservation project of gene resources for an endangered species first involves the preservation of organs, tissues, gametes, genomic DNA libraries and cell lines. The present study is the first to establish and cryopreserve cell lines of liver, heart and muscle tissues from the Chinese alligator. The study revealed that there was a large discrepancy in cell migration time in primary cultures among liver (11-12 d), heart (13-14 d) and muscle (17-18 d) tissue pieces. The differences in time in primary cell culture suggested that it was relatively easy to build visceral-derived cell lines for reptiles. Biological analysis showed that the population doubling time for thawed cells was approxi- mately 36 h. Karyotyping revealed that the frequency of Chinese alligator cells showing chromosome number as 2n=32 was 88.6%-93.4%. Chinese alligator cell lines established here provide a vital resource for research and are likely to be useful for protection of this rare and critically endangered species. Furthermore, the establishment of these methods may supply technical and theoretical support for preserving genetic resources at the cellular level for other reptile species.     

Human gamma-chain genes are rearranged in leukaemic T cells and map to the short arm of chromosome 7

Three gene families that rearrange during the somatic development of T cells have been identified in the murine genome. Two of these gene families (alpha and beta) encode subunits of the antigen-specific T-cell receptor and are also present in the human genome. The third gene family, designated here as the gamma-chain gene family, is rearranged in murine cytolytic T cells but not in most helper T cells. Here we present evidence that the human genome also contains gamma-chain genes that undergo somatic rearrangement in leukaemia-derived T cells. Murine gamma-chain genes appear to be encoded in gene segments that are analogous to the immunoglobulin gene variable, constant and joining segments. There are two closely related constant-region gene segments in the human genome. One of the constant-region genes is deleted in all three T-cell leukaemias that we have studied. The two constant-region gamma-chain genes reside on the short arm of chromosome 7 (7p15); this region is involved in chromosomal rearrangements identified in T cells from individuals with the immunodeficiency syndrome ataxia telangiectasia and observed only rarely in routine cytogenetic analyses of normal individuals. This region is also a secondary site of beta-chain gene hybridization.     

Proteomic analysis of blast-resistant near-isogenic lines derived from japonica rice,var. Yunyin,infected with Magnaporthe oryzae

Rice blast is one of the most devastating dis- eases in the world and outbreaks occur frequently. The differences in protein expression between blast resistant and susceptible near-isogenic lines （NILs） of japonica rice var. Yunyin infected with Magnaporthe oryzae were ana- lyzed using proteomics, indicated that 67 different proteins were identified from 75 obtained proteins using the matrix- assisted laser desorption/ionization time-of-flight mass spectrometry technique. Seven specific expression proteins, 43 up-regulated proteins and 17 down-regulated proteins were identified among the 67 proteins. The bioinformatical analysis demonstrated that these 67 different proteins were involved in many biological physiological processes including five proteins related to photosynthesis, 25 pro- teins related to metabolism, six proteins related to anti- oxidants, 10 proteins related to protein synthesis and modification, five proteins related to signal transduction,four proteins related to adversity stress and 12 non-func- tional proteins. These identified proteins were directly or indirectly related to stress. Five proteins related to different physiological processes were selected. Their cDNA sequences were predicted and their expression patterns were analyzed using real-time PCR, demonstrated that the genes would response to M. oryzae and the response blindingly different between blast resistant and blast sus- ceptible NILs.     

Human immunodeficiency virus genetic variation that can escape cytotoxic T cell recognition.

In a longitudinal study of HIV seropositive patients, there were fluctuations in the specificity of cytotoxic T cells for the virus. This was matched by variability in proviral gag DNA epitope sequences in the lymphocytes of these patients. Some of these viral variants are not recognized by autologous T cells. Accumulation of such mutations in T-cell antigenic targets would provide a mechanism for immune escape.     

Unique cell lines harbouring both Epstein-Barr virus and adult T-cell leukaemia virus, established from leukaemia patients

Members of three distinct classes of animal virus have been associated with naturally occurring neoplasias in man: Epstein--Barr virus (EBV), a DNA virus belonging to herpesvirus group, papillomavirus, and a novel human RNA (retro) virus, human T-cell leukemia virus or adult T-cell leukaemia (ATL) virus. We have established seven continuous cell lines from ATL patients and 0.1-7% of these cells consistently express ATL-specific antigens (ATLA). EBV-associated nuclear antigen (EBNA) is also found in more than 90% of these cells. We have cloned cells from two of these lines and show here that both ATLA and EBNA were present in the same B-cell clone carrying surface immunoglobulin (sIg).     

鳞翅目昆虫细胞抗菌肽的诱导、筛选及抗菌活性的研究

选取3种离体培养的鳞翅目昆虫细胞系,采用热灭活的大肠杆菌诱导的方法,诱导其产生抗菌肽,并进行抗菌活性检测、诱导动力学研究及Tricine SDS-聚丙烯酰胺凝胶电泳检测分析．结果筛选到1株诱导抗菌活性较高的昆虫细胞系——粉纹夜蛾BTI-Tn-5B1细胞系,并发现该粉纹夜蛾5B1细胞在诱导后16h产生了1个分子量大约为8000的抗菌肽,抗菌活性检测表明其对金黄色葡萄球菌（Sta phylococcus aureus）、大肠杆菌（Escherichia coli K12D31）、德氏卑沙门氏菌（Salmonella derby）均有不同程度的抑制作用,其中特别是对革兰氏阴性菌——大肠杆菌K12D31和德氏卑沙门氏菌有较强的抑菌活性．     

B.T.I.阅读模式与大学英语阅读教学

阅读是人们获取信息的一个极其复杂的综合心理言语过程 ,也是英语教学的主要手段。外国专家对阅读模式进行了研究 ,主要有三个阅读模式 :自下而上、自上而下、相互作用模式。笔者结合我国大学英语教学实际 ,提出对提高大学英语阅读教学的几点思考 :我们既不能照搬自上而下的模式 ,也不能照搬自上而下的模式 ,相比较而言相互作用的模式是目前较为理想的阅读模式。广大英语教师应采取切合实际的阅读教学模式以便使学生掌握真正的解码技能