Changes in protein synthesis and breakdown rates and responsiveness to growth factors with ageing in human lung fibroblasts

The effects of insulin, epidermal growth factor, insulin-like growth factor-2 and fetal bovine serum on protein synthesis and protein breakdown have been measured in mid-passage and senescent cultures of human diploid lung fibroblasts. Each of the individual growth factors was a potent inhibitor of protein breakdown with no difference in either the maximum response or sensitivity evident between senescent cells and mid-passage cultures. Binding of 125I-labelled epidermal growth factor per mg of cell protein similarly showed no difference between senescent and confluent mid-passage fibroblasts, although sparse mid-passage cells bound more of the ligand. These results indicate normal binding and normal responsiveness to growth factors in senescent cultures. However, rates of protein synthesis are higher in confluent mid-passage cells and especially so in sparse mid-passage cells than in senescent cells of intermediate density. Furthermore, senescent cells differ from either growth state of mid-passage cells because protein synthesis in aged cells is much less responsive to any of the growth factors or to fetal bovine serum. It is suggested from these results that the reduced ability of serum or growth factors to initiate DNA synthesis or growth in ageing cells may be a consequence of an unresponsive protein synthesis pathway rather than a generalised defect in growth factor action.     

东芝DGW-20A、DFW-10B诊断床点片系统故障代码12处理技巧

故障代码12是东芝DGW-20A、DFW-10B诊断床点片系统最常出现的故障之一。对这个故障如处理不当，易引起胶片密着板进出片口的开闭电机(O／C电机)变速箱损坏，使机器故障扩大化。本文介绍在短时问内安全处理东芝DGW-20A、DFW-10B这两种型号诊断床故障代码12的处理技巧。     

Utilization of nitrogenous compounds by oral bacteria

In terms of the crucial acid-base balance in dental plaque, the bacterial catabolism of nitrogenous compounds, such as peptides and amino acids, is of importance because the end-products can raise plaque pH. Of particular significance is the fermentation of arginine by bacteria such as Streptococcus sanguis, a numerically important plaque organism. Aspects of the uptake of this amino acid were studied and it was also shown the organism can obtain arginine from small peptides, since it possesses cell-associated exo-peptidases. Furthermore, it could grow in media containing whole protein (casein), or one of its fractions, as the sole source of organic nitrogen. The studies thus showed that S. sanguis is well equipped, in terms of endo- and exo-peptidase activities, to obtain the metabolically important arginine from whole protein. It is suggested that knowledge of this type should lead to a better understanding of overall plaque metabolism--of relevance to both cariogenic and periodontopathic plaques.     

东软CT-C3000常见故障及分析

在对CT-C3000四年多的维修与保养中，通过总结得出了多例在日常工作中已经发生的常见故障，原因以及行之有效的解决方法。     

ED50 study of femtosecond terawatt laser pulses on porcine skin

BACKGROUND AND OBJECTIVES: Terawatt (TW) lasers have become commonplace since the development of the chirped-pulse amplification method using Ti:sapphire and Nd:glass laser rods. We have measured the minimum visible lesion (MVL) thresholds for porcine1The animals involved in this study were procured, maintained, and used in accordance with the Federal Animal Welfare Act and the "Guide for the Care and Use of Laboratory Animals" prepared by the Institute of Laboratory Animal Resources-National Research Council. Brooks City-Base, TX has been fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care, International (AAALAC) since 1967. (Yucatan mini-pig) skin using TW laser pulses. STUDY DESIGN/MATERIALS AND METHODS: Our system produced laser pulses at 810 nm and sub-50 femtoseconds. These 1-2 TW laser pulses created multiple self-focusing (SF) filaments during propagation and were directed on the flanks of mini-pigs under anesthesia. We measured the pulse energies necessary to determine the ED(50) skin damage thresholds. RESULTS: The MVL ED(50) threshold at 1 hour was 8 mJ and increased to 21 mJ after 24 hours. Histological sections were obtained after 1-hour and 24-hour readings. CONCLUSIONS: The damage patterns on the skin indicated the number of filaments in the laser pulse. Many of the pulses produced only superficial damage that disappeared in 24 hours and that nearly three times the pulse energy was required to cause subdural or cellular damage. With further research, non-thermal tissue ablation using TW laser pulses could provide a viable alternative to current techniques of laser use in dermatology.     

不可压缩平板边界层转捩中突变过程的数值模拟

采用时间模式对不可压平板边界层从层流到湍流的转捩过程进行了直接数值模拟。分析结果表明：在层流-湍流转捩的突变过程开始之前，已经产生非线性作用；二维波与三维波的幅值实际增长率也偏离线性状态，而且在二者之间存在能量转移的迹象。在突变过程中，速度变形率对总应力的影响较大，在转捩结束后雷诺应力对总应力的影响比较显著。研究表明：正是由于大量谐波被快速激发并增大，导致了雷诺应力及其法向梯度也快速增大。这使得平均流剖面快速被修正，流动快速转为湍流。     

1994-2007年CBMdisc收录MRI维护维修文献的计量分析

利用"中国生物医学文献数据库"(CBMdisc),对1994-2007年5月国内MRI维护维修相关中文文献进行文献计量学分析,对今后国内MRI维护维修工作具有重要指导意义。     

Specificity of brain cathepsin D: cleavage of model peptides containing the susceptible Phe-Phe regions of myelin basic protein

Brain cathepsin D, purified by affinity chromatography on Sepharose pepstatin columns, was incubated with synthetic peptides corresponding to the susceptible regions of the myelin basic protein encompassing the two Phe-Phe bonds. One peptide, Leu-Gly-Arg-Phe-Phe-Gly-Gly, was cleaved by cathepsin D at the Phe-Phe bond while another, Val-His-Phe-Phe-Lys-Asn-Gly, was resistant to cleavage. To determine if this was a result of His flanking the Phe-Phe bond, or chain length on the N-terminal side, two decapeptides were synthesized differing only in the presence or absence of His adjacent to Phe. The results show that both of the decapapetides were cleaved by cathepsin D at the Phe-Phe linkages. In addition, prolonged incubation led to release of N-terminal Lys, indicating an additional cleavage at the Phe-Lys bond. In contrast to the limited cleavage by cathepsin D, pepsin split all four peptides. These results support earlier work on the limited proteolysis of basic protein at the Phe-Phe bond and suggest additional sites upon prolonged exposure. Such peptides may have utility as alternative substrates for basic protein or as models for subsequent synthesis of possible inhibitors of the enzyme.