Ion conduction pore is conserved among potassium channels.

Potassium channels, a group of specialized membrane proteins, enable K+ ions to flow selectively across cell membranes. Transmembrane K+ currents underlie electrical signalling in neurons and other excitable cells. The atomic structure of a bacterial K+ channel pore has been solved by means of X-ray crystallography. To the extent that the prokaryotic pore is representative of other K+ channels, this landmark achievement has profound implications for our general understanding of K+ channels. But serious doubts have been raised concerning whether the prokaryotic K+ channel pore does actually represent those of eukaryotes. Here we have addressed this fundamental issue by substituting the prokaryotic pore into eukaryotic voltage-gated and inward-rectifier K+ channels. The resulting chimaeras retain the respective functional hallmarks of the eukaryotic channels, which indicates that the ion conduction pore is indeed conserved among K+ channels.     

GPS定位和陀螺定向在大型贯通测量中的应用

详述了GPS定位和陀螺定向在大型贯通测量中的应用，并总结了煤矿测量的成功经验。     

Mutant mitochondrial thymidine kinase in mitochondrial DNA depletion myopathy.

The mitochondrial deoxyribonucleotide (dNTP) pool is separated from the cytosolic pool because the mitochondria inner membrane is impermeable to charged molecules. The mitochondrial pool is maintained by either import of cytosolic dNTPs through dedicated transporters or by salvaging deoxynucleosides within the mitochondria; apparently, enzymes of the de novo dNTP synthesis pathway are not present in the mitochondria. In non-replicating cells, where cytosolic dNTP synthesis is down-regulated, mtDNA synthesis depends solely on the mitochondrial salvage pathway enzymes, the deoxyribonucleosides kinases. Two of the four human deoxyribonucleoside kinases, deoxyguanosine kinase (dGK) and thymidine kinase-2 (TK2), are expressed in mitochondria. Human dGK efficiently phosphorylates deoxyguanosine and deoxyadenosine, whereas TK2 phosphorylates deoxythymidine, deoxycytidine and deoxyuridine. Here we identify two mutations in TK2, histidine 90 to asparagine and isoleucine 181 to asparagine, in four individuals who developed devastating myopathy and depletion of muscular mitochondrial DNA in infancy. In these individuals, the activity of TK2 in muscle mitochondria is reduced to 14-45% of the mean value in healthy control individuals. Mutations in TK2 represent a new etiology for mitochondrial DNA depletion, underscoring the importance of the mitochondrial dNTP pool in the pathogenesis of mitochondrial depletion.     

Central IL-1 differentially regulates peripheral IL-6 and TNF synthesis

Centrally given interleukin (IL)-1 is known to induce a rapid rises in blood IL-6. To extend this and to examine the mechanism by which this occurs, the effects of intracerebroventricular (icv) injection of human recombinant IL-1β on mRNA expression of IL-6 and tumour necrosis factor (TNF) in the spleen and liver were examined in rats. Icv injection of IL-1 produced a rapid rise of the tissue mRNA levels of IL-6 and TNF in both organs, prior to and/or in parallel with an increase in their serum levels. Pretreatment with chlorisondamine, a ganglionic blocking agent, inhibited the IL-6 responses, while it had little influence on the TNF responses. The results suggest that brain IL-1 induces peripheral production of IL-6, but not of TNF, through autonomic nervous system activation. Received 27 October 1997; received after revision 15 December 1997; accepted 12 January 1998     

Shrinkage Properties of Wool and Acrylic/Wool Plain Knitted Fabrics Treated with DC109

This paper examines the effects of shrink - resist treatment, washing cycle and fabric tightness on the shrinkage properties of plain knitted fabrics made from 100% wool, acrylic/wool (50/50) and acrylic/wool (70/30). It was found that shrinkages of both treated and untreated wool fabrics were negatively correlated to fabric tightness and exceeded the IWS shrinkage limits (5% in length and 8 % in area) after 2 - 5A washing cycle. The effect of tightness was not as obvious with acrylic/wool (A/W) fabrics, but the shrinkage was seen to increase with stages of washing cycle for untreated A/W fabrics with some exceeding IWS standard. By applying the DC 109 shrink - resist solvent treatment, it was identified that by with higher percentage of acrylic fibre blended with wool, shrinkage could be reduced considerably and within acceptable limits.     

Mutations in RECQL4 cause a subset of cases of Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS; also known as poikiloderma congenitale) is a rare, autosomal recessive genetic disorder characterized by abnormalities in skin and skeleton, juvenile cataracts, premature ageing and a predisposition to neoplasia. Cytogenetic studies indicate that cells from affected patients show genomic instability often associated with chromosomal rearrangements causing an acquired somatic mosaicism. The gene(s) responsible for RTS remains unknown. The genes responsible for Werner and Bloom syndromes (WRN and BLM, respectively) have been identified as homologues of Escherichia coli RecQ, which encodes a DNA helicase that unwinds double-stranded DNA into single-stranded DNAs. Other eukaryotic homologues thus far identified are human RECQL, Saccharomyces cerevisiae SGS1 and Schizosaccharomyces pombe rqh1. We recently cloned two new human helicase genes, RECQL4 at 8q24.3 and RECQL5 at 17q25, which encode members of the RecQ helicase family. Here, we report that three RTS patients carried two types of compound heterozygous mutations in RECQL4. The fact that the mutated alleles were inherited from the parents in one affected family and were not found in ethnically matched controls suggests that mutation of RECQL4 at human chromosome 8q24.3 is responsible for at least some cases of RTS.     

QSHR中理化参数描述矩阵的病态参数剔除

在定量构效关系（ＱＳＡＲ）研究中各理化参数ｘｉ构成的描述矩阵，由于参数之间的相关性往往呈病态性或奇异性，由此获得的ＱＳＡＲ回归方程则不稳定，本文提出了一种新方法即病态指标剔除法：选择一个适当的临界值α∈（０，１），找出相关系数大于或等于该临界值所涉及的指标，剔除部分病态指标；再作逐步回归从而获得稳定优良的ＱＳＡＲ回归方程，可望在ＱＳＡＲ中广泛应用．     

面心立方萤石结构Ce_（1－x）Tb_xO_（2－δ）固溶体的氧缺欠研究

以热重量法研究了Ｃｅ１－ｘＴｂｘＯ２－δ（ｘ＝０．３，０．４，０．５）的缺氧分数６值．发现δ值随组成、环境氧分压和温度的不同在０．０６—０．４范围内变化．样品ＣＴ３０和ＣＴ５０于６５０℃以上温度在空气中失氧形成氧空位的反应热熔经估算分别为３６．０和４０．６ｋＪ／ｍｏｌ．研究表明，该数值主要由Ｔｂ离子的反应性决定，该复合氧化物中Ｃｅ离子的还原反应热焓显著小于它在纯ＣｅＯ２－δ中的数值．     

Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana

The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we report one of the first milestones of this project, the sequence of chromosome 4. Analysis of 17.38 megabases of unique sequence, representing about 17% of the genome, reveals 3,744 protein coding genes, 81 transfer RNAs and numerous repeat elements. Heterochromatic regions surrounding the putative centromere, which has not yet been completely sequenced, are characterized by an increased frequency of a variety of repeats, new repeats, reduced recombination, lowered gene density and lowered gene expression. Roughly 60% of the predicted protein-coding genes have been functionally characterized on the basis of their homology to known genes. Many genes encode predicted proteins that are homologous to human and Caenorhabditis elegans proteins.