脆性X综合征与FMR—1基因

脆性Ｘ综合征（ＦＸ）患者的脆性位点（ＦＲＡＸＡ）与ＦＡＲ－１位点一致，脆性断点位于（ＣＧＧ）ｎ上，而ＦＭＲ－１突变有两类：（ＣＧＧ）ｎ重复数突变和点突变（或丢失）。同时表明ＦＭＲ－１５′侧ＣＰＧ岛甲基化，并介绍了ＦＭＲ－１（ＣＧＧ）ｎ突变分子生物学检测方法。     

脆性X综合征的分子机制

脆性Ｘ智力低下基因（ＦＭＲ－１）克隆后，特别是１９９３年以来，在ＦＭＲ－１精细细胞与功能及脆性Ｘ综合征发病机制等方面的研究有了重要发现。现已知ＦＭＲ－１有１７个外显子，分布在３８ｋｂ范围内，而不是当初推测的８０ｋｂ以上，ＦＭＲ－１的表达产物为一种ＲＮＡ结合蛋白；ＦＭＲ－１异常甲基化的研究支持Ｘ失活印迹假说；染色体奠基突变是导致ＦＭＲ－１突变的原因；在三核苷酸动态突变的疾病中，只有（ＣＧＧ）ｎ序列拷     

脆性X综合征与FMR－1基因

脆性Ｘ综合征（ＦＸ）患者的脆性位点（ＦＲＡＸＡ）与ＦＭＲ－１位点一致，脆性断点位于（ＣＧＧ）ｎ上，而ＦＭＲ－１突变有两类：（ＣＧＧ）ｎ重复数突变和点突变（或丢失）。同时表明ＦＭＲ－１５＇侧ＣｐＧ岛甲基化。并介绍ＴＦＭＲ－１（ＣＧＧ）ｎ突变分子生物学检测方法。     

PREPARATION OF COLLAGEN/HYDROXYLAPATITE COMPOSITE FILLING PLASTIC MATERIAL AND ANIMAL EXPERIMENT STUDY

ＰＲＥＰＡＲＡＴＩＯＮＯＦＣＯＬＬＡＧＥＮ／ＨＹＤＲＯＸＹＬＡＰＡＴＩＴＥＣＯＭＰＯＳＩＴＥＦＩＬＬＩＮＧＰＬＡＳＴＩＣＭＡＴＥＲＩＡＬＡＮＤＡＮＩＭＡＬＥＸＰＥＲＩＭＥＮＴＳＴＵＤＹＰＲＥＰＡＲＡＴＩＯＮＯＦＣＯＬＬＡＧＥＮ／ＨＹＤＲＯＸＹＬＡＰＡ...     

EXPERIMENTAL RESEARCH OF ELFEMF ON CHANGE OF HEMORHEOLOGICAL PROPERTY AND DESIGN OF ELFEMF GENERATOR

ＥＸＰＥＲＩＭＥＮＴＡＬＲＥＳＥＡＲＣＨＯＦＥＬＦＥＭＦＯＮＣＨＡＮＧＥＯＦＨＥＭＯＲＨＥＯＬＯＧＩＣＡＬＰＲＯＰＥＲＴＹＡＮＤＤＥＳＩＧＮＯＦＥＬＦＥＭＦＧＥＮＥＲＡＴＯＲＥＸＰＥＲＩＭＥＮＴＡＬＲＥＳＥＡＲＣＨＯＦＥＬＦＥＭＦＯＮＣＨＡＮＧＥＯＦ...     

脆性位点FRAXE分子遗传学研究进展

Ｘｑ２８区带上（ＣＧＧ）ｎ结构的扩展作为脆性点ＦＲＡＸＥ分子遗传学基础的研究结果发表之时，正值人类动态突变性遗传病概念确立不久。因此，医学遗传学界试图通过脆性位点ＦＲＡＸＥ分子遗传学的研究堤法阐明人类动态突变性遗传和人类脆性位点共同的分子遗传规律。     

急性低氧性肺动脉高压与磷脂酶A2活力关系初探

目的：探讨ＰＬＡ２及相关炎症介质在急性低氧性肺动脉高压形成中的作用。方法：用３０只ＳＤ大鼠随机分为三组（各１０只）：正常对照组（Ａ）、低氧组（Ｂ）、低氧加地塞米松组（Ｃ）。测定磷脂酶Ａ２活力（ＰＬＡ２）、血小板活化因子（ＰＡＦ）、前列腺素Ｅ２（ＰＧＥ２）、血栓素Ｂ２（ＴＸＢ２）。结果：Ｂ组低氧３０ｍｉｎ后，平均肺动脉压（ｍＰＡＰ）、血及肺中ＰＬＡ２活力、ＰＧＥ２、ＴＸＢ２、ＰＡＦ均明显增高；Ｃ组上述指标均明显低于Ｂ组。低氧情况下，ＰＬＡ２与ｍＰＡＰ、ＰＡＦ、ＰＧＥ２、ＴＸＢ２均呈正相关；ＰＡＦ、ＰＧＥ２、ＴＸＢ２分别又与ｍＰＡＰ呈正相关。结论：ＰＬＡ２通过相关炎症介质在急性低氧性肺动脉压的形成中可能起重要的介导作用。     

医用磁性纳米材料的制备───制备条件对有效粒径的影响

医用磁性纳米材料的制备＊制备条件对有效粒径的影响常津（天津大学生物工程研究中心，天津３０００７２）ＰＲＥＰＡＲＡＴＩＯＮＯＦＭＥＤＩＣＡＬＭＡＧＮＥＴＩＣＤＥＸＴＲＡＮＮＡＮＯＰＡＲＴＩＣＬＥＳＩＮＦＬＵＥＮＣＥＯＦＰＲＥＰＡＲＡＴＩＯＮＣＯＮＤＩＴ...     

骺板在受外力作用下的变形分析一例

骺板在受外力作用下的变形分析一例刚芹果（河北大学数学系，保定０７１００２）ＡＮＥＸＡＭＰＬＥＯＮＴＨＥＤＥＦＯＲＭＡＴＩＯＮＡＮＡＬＹＳＩＳＯＦＥＰＩＰＨＹＳＥＡＬＰＬＡＴＥＵＮＤＥＲＴＨＥＦＯＲＣＥＧａｎｇＱｉｎｇｕｏ（ＤｅｐａｒｔｍｅｎｔｏｆＭａ...     

A GLUCOSE SUPPORTER FOR MICORSURGERY AND ITSEXPERIMENTAL STUDY

ＡＧＬＵＣＯＳＥＳＵＰＰＯＲＴＥＲＦＯＲＭＩＣＯＲＳＵＲＧＥＲＹＡＮＤＩＴＳＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＡＧＬＵＣＯＳＥＳＵＰＰＯＲＴＥＲＦＯＲＭＩＣＯＲＳＵＲＧＥＲＹＡＮＤＩＴＳＥＸＰＥＲＩＭＥＮＴＡＬＳＴＵＤＹＺｈｕＨｏｎｇｋｕｉ；ＬｉＹｏ...     

The cloning of FRAXF: trinucleotide repeat expansion and methylation at a third fragile site in distal Xqter

Three fragile sites, FRAXA, FRAXE and FRAXF lie in the Xq27–28region of the human X chromosome. The expression of FRAXA isassociated with the fragile X syndrome, the most prevalent formof Inherited mental retardation whilst the expression of FRAXEIs associated with a rarer and comparatively milder form ofmental handicap. Both the FRAXA and FRAXE sites have been clonedand the fragile site expression found to be due to the expansionof analogous CGG/GCC trinucleotide repeat arrays. We describehere the cloning of the third fragile site, FRAXF, and demonstratethat it Involves the expansion of a (GCCGTC)n(GCC)n compoundarray. PCR analyses across the repeat of normal individualsshow that the number of triplets in the array ranges from 12–26and the most common allele consists of 14 triplet units. Sequencinganalyses show that 95% of normal individuals have three copiesof the GCCGTC motif and In these individuals, the size variationobserved by PCR is due to copy number alterations in the GCCarray. In a cytogenetically positive male with developmentaldelay, the array is expanded by >900 triplets and the adjacentCpG-rich region is methylated. The array is also expanded Incytogenetically positive carrier females from the family originallyused to define the FRAXF site. We conclude that the expandedarray corresponds to the FRAXF fragile site.     

Prevalence of the fragile X syndrome in Yugoslav patients with non-specific mental retardation

Mutations at two fragile sites, FRAXA and FRAXE, loci are caused by an expansion of a CGG/GCC trinucleotide repeat and are characterized by mental retardation. Here we report molecular screening survey of 97 unrelated individuals diagnosed with non-specific mental retardation (MR), which produced positive test for FRAXA in two boys and none positive for the FRAXE mutation. In addition, we studied allelic frequency distribution for the FRAXA locus in this group of mentally retarded patients, as well as in the 99 healthy subjects of Yugoslav population. The distribution of FMR1 CGG repeat size in both groups was similar: the most common allele contained 29 repeats (32.86% in the healthy population and 54.54% in MR population), followed by the allele with 28 CGG repeats (21.43% in the healthy and 12.2% in MR population). Premutation alleles with more than 45 repeats were not found in control nor in the MR group.     

FRAXE mutation in mentally retarded patients using the OxE18 probe

The folate-sensitive fragile site FRAXE is located in proximal Xq28 of the human X chromosome and lies approximately 600 kb distal to the fragile X syndrome (FRAXA) fragile site at Xq27.3. Although FRAXA and FRAXE are indistinguishable by means of conventional cytogenetics, they can now be delineated at the molecular level and provides the basis for a proper diagnosis. The screening for CGG amplifications in the FMR1 gene was based on standard protocols using EcoRI digests on Southern blots and hybridization with the StB12.3 probe. The FRAXE mutation was analyzed by digestion with HindIII and the filters were probed with OxE20. We present the results of 144 patients referred for fragile X testing but negative for the FMR1 gene trinucleotide expansion, that were also screened for the FMR2 expansion. For FRAXE mutation a molecular protocol for OxE18 probe was used, in the DNA samples digested with EcoRI on the same blots as those used for detection of FRAXA. None of the patients tested were positive for the FRAXE expansion. This technique was successfully established into our laboratory routine showing the practical use of testing for FRAXA and FRAXE in a large series of patients.     

A simple multiplex FRAXA, FRAXE, and FRAXF PCR assay convenient for wide screening programs

FRAXA, FRAXE, and FRAXF are folate-sensitive fragile sites originally discovered in patients with X-linked mental retardation. The FMR1 gene, whose first exon includes the FRAXA site on Xq27.3, accounts for 15-20% of all X-linked forms of mental retardation. Loss of expression of FMR2, a gene adjacent to the FRAXE site on Xq28, is correlated with FRAXE expansion in some mild mentally retarded patients. FRAXF is a fragile site whose expression has not been associated with any pathological phenotype. The fragility in all three sites is caused by expansions of CGG repeats adjacent to hypermethylated CpG islands. The prevalence of FRAXA, FRAXE, and FRAXF remains uncertain because of the lack of a simple and cost-effective test allowing wide screening programs. For the same reason, the real phenotype-genotype correlations in FRAXE and FRAXF are uncertain as well. We have developed a rapid multiplex polymerase chain reaction (PCR) assay in which hypermethylated CpG islands adjacent to FRAXA, FRAXE, and FRAXF are displayed. The test is very simple and cost-effective, requires only 30 microl of peripheral blood, and can be used for performing diagnoses, postnatal and prenatal, and for screening large groups of control and mentally retarded males and newborn boys.     

Instability of the FMR2 trinucleotide repeat region associated with expanded FMR1 alleles

The fragile sites FRAXA and FRAXE, located ∼600 kb apart on Xq27.3 and Xq28, respectively, are due to a CGG trinucleotide repeat expansion. Although the expansion mechanism for these and other trinucleotide repeat disorders remains unknown, the similarities between the FRAXA and FRAXE regions suggest a possible association between the 2 sites. DNA from 953 individuals was analyzed to determine the distribution of FRAXE repeat sizes in this population and to ascertain potential association between FRAXA and FRAXE repeat sizes. Thirty-four FMR2 alleles ranging from 3–42 repeats were identified. No FRAXE expansions were found in this population, supporting previous findings that FRAXE expansions are rare. However, in the fragile X syndrome affected group, a FMR2 delection, 2 cases of FRAXE repeat instability and a FRAXE mosaic male were identified. Also, a previously identified, rare FMR2 polymorphism was observed. Statistical analyis showed no correlation between normal FRAXA and FRAXE repeat sizes studied, although there was a significant size difference in larger FMR2 alleles that segregated with expanded FMR1 alleles. These findings support the idea of an association between repeat expansion in the FMR1 gene and instability or deletions in the FMR2 gene. Am. J. Med. Genet. 73:447–455, 1997. © 1997 Wiley-Liss, Inc.     

Molecular screening of fragile X (FRAXA) and FRAXE mental retardation syndromes in the Hellenic population of Greece and Cyprus: incidence, genetic variation, and stability.

This study presents the first large, population-based molecular investigation of the fragile X (FRAXA) and FRAXE mental retardation syndromes in the Hellenic populations of Greece and Cyprus. The aims of this population screening were to determine the prevalence of FRAXA and FRAXE syndromes among idiopathic mentally retarded (IMR) individuals, to estimate the incidence in the general population, and to investigate the molecular mechanism of instability and expansion of the FMR1-repeat. Ten FRAXA patients were identified to have either the full mutation (eight) or premutation (two) from a Hellenic population of 866 unrelated IMR individuals (611 males and 255 females, age range 3-25 years). No FRAXE patients were identified among the 611 IMR males. The incidence of FRAXA in the Hellenic population of Cyprus is estimated at 1 in 4,246 males. The repeat sites from the FMR1 and FMR2 alleles were accurately determined and showed similar distribution and frequencies with other population studies. The analysis of AGG interspersion within the FMR1-repeat in normal males revealed long, pure CGG repeats within the "gray zone" as well as variation within the 3' end showing polarity of instability. This finding supports the hypothesis that the AGG interspersion and the length of the pure repeat are major factors in determining allele stability. Analysis of FRAXAC1, DXS548, and FRAXAC2 identified particular alleles and haplotypes to have a significant association with either gray zone alleles or alleles >15 pure CGG repeats. We hypothesize that this subgroup of alleles and haplotypes are associated with long pure CGGs (>15 CGG) or 35 repeats and, having shared an evolutionary past, would have the tendency to expand.     

Characterisation of a new rare fragile site easily confused with the fragile X.

A new fragile site (FRAXE) in Xq28 is described. It appears to be a typical folate sensitive fragile site. The fragile site is not associated with mental retardation, it does not give abnormal results when subjected to Southern analysis with probe pfxa3 which detects the unstable DNA sequence characteristic of fragile X syndrome. In situ hybridization mapping locates the fragile site between 150 kb and 600 kb distal to FRAXA. The distinction between the two fragile sites is important clinically since cytogenetic detection of FRAXE, without molecular analysis, could result in misdiagnosis of fragile X syndrome.     

Identification of the FRAXE fragile site in two families ascertained for X linked mental retardation.

Chromosome fragility in two families not exhibiting amplification of the CGG trinucleotide associated with the fragile X site has been examined. Fluorescence in situ hybridisation with cosmid DNA from loci immediately flanking FRAXA and other distal loci have confirmed that cytogenetic fragility in these subjects is the result of expression of a new folate sensitive fragile X site, FRAXE.     

Routine clinical application of the FRAXA Pfu PCR assay: limits and utility

Fragile X genotype is characterized by the excessive amplification of an unstable region of DNA: a trinucleotide repeat CGG of variable copy number present in the FRAXA locus. Methods based on polymerase chain reaction (PCR) amplification of the CGG repeat region could facilitate the development of a rapid screening assay. Unfortunately, amplification across CGG repeats can be inefficient and unreliable due to their 100% G+C base composition. The utility of the exonuclease-deficient Pfu polymerase for amplification and detection of the CGG repeats at the FRAXA locus has been reported. In the present study we analysed the utility of a Pfu PCR assay as a rapid initial screening method to rule out a diagnosis of fragile X syndrome in males with mental retardation. Affected males did not show any amplification products or a smear of amplification products between 350 and 550 bp. Only 10% of affected male samples did not show any amplification products, while the vast majority showed the amplification smear. The amplification smears represent a serious drawback of the method, since they cannot be distinguished from the amplification products of normal samples after separation in 1 % agarose gel. Several modifications of the PCR conditions were attempted to eliminate this problem, but none was appropriate for clinical applications. However, the problem was easily solved by using a higher resolution electro-phoretic system that allows a clear distinction of normal bands from pathological smears. We tested the specificity of the Pfu PCR assay, followed by an improved MetaPhor gel electrophoretic separation of PCR products, on 50 samples from normal males and 24 samples from affected males. The results showed that this method is a rapid, sensitive and specific assay for the exclusion of fragile X syndrome diagnosis in mentally retarded males.