Derivation and spontaneous differentiation of human embryonic stem cells

Embryonic stem (ES) cells are unique cells derived from the inner cell mass of the mammalian blastocyst. These cells are immortal and pluripotent, retain their developmental potential after prolonged culture, and can be continuously cultured in an undifferentiated state. Many in vitro differentiation systems have been developed for mouse ES cells, including reproducible methods for mouse ES cell differentiation into haematopoietic and neural precursors, cardiomyocytes, insulin‐secreting cells, endothelial cells and various other cell types. The derivation of new human ES cell lines provides the opportunity to develop unique models for developmental research and for cell therapies. In this review we consider the derivation and spontaneous differentiation of human ES cells.     

A perspective on measurement of mutations in vivo.

The development of transgenic mouse lines with target genes that are suitable for tissue-specific mutagenesis studies is an important contribution to the field of environmental mutagenesis. These models can accommodate many of the questions relating to metabolism, distribution and relative potency of mutagens as well as providing a more comprehensive system for the identification of mutagens. However, the lesions that the field has learned about methods, development and validation from the use of in vitro systems must be applied to the development and validation of transgenic models.     

智力低下者皮纹特征研究

通过对８３例智力低下者（男５８人，女２５人，ＩＱ２５～８９）的１７项指纹指标和７项掌纹指标特征的观察分析，并与７５２例中等智力者（男３７０人，女３８２人，ＩＱ９０～１０９）的指纹和掌纹进行比较。结果表明，两组间有１０项指标存在显著差异或高度差异，其中Ｗｃ、Ｗｂ、ｗＡｃ、Ｌ、Ｓｄ和Ｔｈ／１的真实花纹等６项指标与智力呈负相关；Ｗｓ、ｗｄｌ、Ｌｕ、ＰＴＣ等４项指标与智力呈正相关。同时，作者提出了Ｗｃ、Ｗｂ、ＷＡｃ、Ｓｄ和ＰＴＣ的正常值，其可作为判定智力低下的重要生物学指标，为筛查弱智儿童提供了一种简便易行的方法。作者还为皮纹学的研究方向提出了新的建议。同时，作者还发现了一种新的皮纹型，暂命名为Ｗｂ。     

细小病毒H－1对肿瘤细胞株的杀伤研究

本文利用细胞集落形成测定细胞存活率的方法，检测了仓鼠细小病毒（ＰＶＨ－１）对２株不同分化程度的胃癌细胞的抑制作用。同时收集感染后４８ｈ、７２ｈ、９６ｈ、１４４ｈ的胃癌细胞，利用电镜观察胃癌细胞的变化。结果表明，ＰＶＨ－１能抑制不同分化程度的胃癌细胞株，其敏感性与胃癌细胞的分化程度有关。     

广西巴马长寿乡壮族长寿老人永生细胞库的建立

目的：建立广西巴马长寿乡壮族长寿老人永生细胞库。方法：使用EB病毒转化外周血B淋巴细胞方法。结果：建立了长寿者外周血细胞转化永生细胞株的方法，转化成功率77．4％。建立了65株长寿老人、直系亲属永生细胞株及长寿老人资料库和完整的细胞株档案。结论：广西巴马长寿乡壮族长寿老人永生细胞库的建立为永久保存细胞系及后续研究提供了必要的基础。     

模拟调强技术照射鼻咽低分化鳞癌细胞的生物效应机制研究

Objective To study the altered radiobiological effect of simulative intensity-modulated radiotherapy (SIMR) in cultured human nasopharyngeal carcinoma (NPC) cells and the related mechanism. Methods Single cell suspension of exponentially growing CNE-2 cells, a poor differentiated NPC cell line, was seeded and cultured for 12 hours, then the cells were irradiated in two different models by 6 MV X-ray beams at 3 Gy/min. In single fraction irradiation (SFR) model, cells were irradiated a single fraction of 0, 2, 4, 6 or 8 Gy within 0 to 3 minutes. In S1MR model, cells were irradiated 0, 2, 4, 6 or 8 Gy in 5 frac-tions with interval of 8.0-8.5 minutes between. Clonogenic assay was performed to determine the radiosen-sitivity. Cellular apoptosis was measured by flow cytometry. RT-PCR was used to detect mRNA expressions of Bax and Bcl-2, Respectively. Results Compared with SFR group, the survival fraction in SIMR group was higher at all the dose levels. The values of α, β, D0 and Dq were higher in SIMR group than in SFR group. At dose levels of 2 Gy, 4 Gy and 6 Gy, The early and late apoptotic cells in SIMR group were lower than in SFR group (21.20%: 15.89%, F=18.51, P=0.020;13.00%: 10.20, F=15.67, P=0.040).The mRNA expression of Bax was upregulated in a dose-dependent manner in the both groups. Compared with SFR group, the mRNA expression of Bax in SIMR group was lower at all the dose levels (Mean value of 76.75% : 62.50%, F =36.57, P =0.000). Bcl-2 mRNA expression at every dose level had no significant difference between the two groups (Mean value of 29.25% : 29.75%, F=0.74, P=0.800). Conclusions Prolonged delivery time in SIMR model can decrease the radiobiological effects.     

Familial systematized epidermal nevus syndrome

Epidermal nevi are typically congenital but rarely familial. We report on a family in which 3 relatives have systematized epidermal nevi. The propositus also has evidence of a hemangioma and a hemangioendothelioma. Peripheral blood and skin fibroblast karyotypes of the propositus did not show evidence of mosaicism. Epidermal nevi have been associated with nondermatologic pathology, involving the nervous, vascular, and skeletal systems in sporadic cases. This report demonstrates that nondermatologic pathology can be also be associated with systematized epidermal nevi in a familial setting. The apparent skipping of generations may be explained by autosomal dominant inheritance with decreased penetrance. © 1992 Wiley-Liss, Inc.     

Intoxicating effects of lorazepam and barbital in rat lines selected for differential sensitivity to ethanol

The motor impairing effects and plasma concentrations of barbital and lorazepam were studied in the alcohol tolerant (AT) and alcohol non-tolerant (ANT) rat lines developed for low and high sensitivity to motor impairment from ethanol. The mixed (M) line, from which the AT and ANT rats were derived, was also included in the study. Like ethanol, barbital and lorazepam impaired the performance of the ANT rats more than that of the AT rats. The motor performance of the M rats was relatively more impaired after barbital than after lorazepam administration at the same dose used in the AT and ANT rats. At the two latter time points (2.5 and 3.5 h) the sensitive ANT rats had significantly higher serum barbital concentrations than the AT rats. The serum barbital concentrations of the AT and ANT rats did not differ, however, at the two first time points (0.5 and 1.5 h) of the tilting plane tests, although the ANT rats were significantly more intoxicated. The concentrations of lorazepam in plasma do not explain the differential motor impairment either, since the sensitive ANT rats had lower plasma concentrations than the insensitive AT rats. The results, thus, suggest that the selection involved in the development of the AT and ANT lines has not been specific for ethanol. The results also support the idea that ethanol, barbiturates and benzodiazepines have some modes of action in common.     

Evidence for a human IgG1 class switch program

In activated murine B lymphocytes, immunoglobulin class switch recombination occurs as a highly regulated process which is targeted to distinct switch regions. Here we present first evidence that in human B lymphocytes, switch recombination is targeted to distinct switch regions as well. In a panel of clonally unrelated IgG1-expressing human B cells, immortalized by Epstein-Barr virus (EBV) transformation, seven out of nine cells show switch recombination between Sμ and Sγ1 on both alleles, the active and inactive one. The remaining cells show no switch recombination on the inactive IgH locus. The very strong correlation of switch recombination on both alleles of IgG1-expressing cells proves that class switch recombination to IgG1 is not random but directed in human B lymphocytes.     

The Dodo Bird: Less a Verdict Than an Opportunity

I contend that although the Luborsky et al. findings on the Dodo bird verdict are noteworthy, the methodology on which they are based is significantly delimited. Amplifying Luborsky et al.'s moderate recognition of that delimitation, I propose a qualitative complement to the extant research. I call this complement "amalgamated" qualitative research and propose that it will deepen, clarify, and contextualize Luborsky et al.'s enigmatic findings. Until this amalgam is implemented, therapy research will be relegated to impressions rather than fine-grained illuminations.