Pilot study for the neonatal screening of fragile X syndrome

An Erratum has been published for this article in Prenatal Diagnosis 23 (9), 2003, 771. Fragile X syndrome (SFX) is the commonest form of inherited mental retardation. Due to the highly variable phenotype clinical diagnosis is complicated. In nearly all cases, the disorder is caused by expansion of a CGG-repeat in the 5′-untranslated region of the FMR1 (fragile X mental retardation-1) gene. We have evaluated the feasibility, efficiency and costs of two methodologies in order to develop a simple test to screen large populations: PCR and fragile X mental retardation-1 protein (FMRP) immunodetection. We studied 100 newborn males using PCR and immunodetection (26.91 Euro). All but one amplified the CGG repeat of the FMR1 gene within the normal size range. The sample that failed to amplify showed only 28% of FMRP expression by immunodetection study; both results indicated an affected male. A further 100 males were studied only by polymerase chain reaction (PCR) (7.8 Euro); all of them amplified within the normal size range. Both methodologies, PCR and immunodetection, are feasible for screening large populations, PCR being the most suitable, economical and less time-consuming. However, it is advisable to keep slides for immunodetection when PCR fails or the external control shows no amplification. Early detection of SFX-affected individuals would represent a great benefit for their maximum social integration, due to appropriate treatment and early stimulation and would permit a cascade screening in their pedigree. Copyright © 2002 John Wiley & Sons, Ltd.     

Preimplantation genetic diagnosis of the fragile X syndrome by use of linked polymorphic markers

Fragile X syndrome is the most common cause of familial mental retardation. The most common mutation is expansion of a triplet (CGG)_n repeat in the 5′ untranslated region of the FMR1 gene on Xq27.3. The expansion is refractory to PCR due to preferential amplification of the smaller allele in heterozygous cells and the high GC content of the repeat and surrounding sequences. Direct detection of the normal parental alleles in preimplantation embryos has been used for preimplantation genetic diagnosis (PGD) of this disorder. However, this approach is only suitable for approximately 63% of couples due to the heterozygosity of the repeat in the normal population. As an alternative we investigated the use of polymorphic markers flanking the mutation to track the normal and premutation carrying maternal chromosomes in preimplantation embryos. Using a panel of 11 polymorphisms, six (CA)_n repeats and five single nucleotide polymorphisms, diagnosis was developed for 90% of referred couples. Multiplex amplification of informative markers was tested in 300 single buccal cells from interested couples with efficiency and allele drop out (ADO) rates ranging from 69% to 96% and 6% to 18%, respectively. Use of this approach is accurate and applicable to a larger number of patients at risk of transmitting fragile X to their offspring. Copyright © 2001 John Wiley & Sons, Ltd.     

Prenatal diagnosis of fragile X in a heterozygous female fetus and postnatal follow-up

An apparently normal female infant was born after the prenatal diagnosis of fragile Xq27×28 present in about 4 per cent of amniocytes. The mildly retarded mother had been found in early pregnancy to be heterozygous for fragile X. The child, now 9 months old. showed about the same level of fragile X expression as her mother. Variations in the proportion of cells with fragile X appeared to be related to cell type and laboratory techniques. The infant's growth and development have been normal. Different techniques to induce or increase the expression of fragile X are discussed.     

Prenatal diagnosis of fragile x syndrome: (cgg)n expansion and methylation of chorionic villus samples

Fragile X syndrome is the most common form of inherited mental retardation, due to an expansion of the (CGG)_n trinucleotide repeat in the FMR-1 gene and hypermethylation of its 5′ upstream CpG island. Two major problems remain to be resolved for fragile X prenatal diagnosis: the abnormal methylation patterns of chorionic villus samples (CVS) and the inability to predict the mental status of females with the full mutation. We present here the results of ten prenatal diagnoses of fragile X syndrome using Southern blotting and polymerase chain reaction (PCR) amplification, and the analysis of 50 further CVS to test the methylation status of the CpG island of the FMR-1 gene. In the ten ‘at-risk’ CVS, eight normal (five males and three females) and two affected male fetuses were detected. Absence of methylation in the CVS was observed in two cases, which was not found upon subsequent examination of the newborn or of fetal tissues. In the 50 CVS not ‘at risk’ for fragile X syndrome, abnormal fragment patterns for probe StB12.3 were detected in 32 per cent for female and 24 per cent for male fetuses. This abnormal pattern could be due to absent or partial methylation of the CpG island of the FMR-1 gene in chorionic villus tissues.     

Early prenatal diagnosis of the fragile site AT Xq27.3 associated with Martin-Bell syndrome

Early prenatal diagnosis of the fragile X was attempted in 44 pregnancies, including one twin pregnancy at risk of Martin-Bell (MB) syndrome. The sex ratio was 24M:21F. The fragile site was reproducibly demonstrated in cultured chorionic villus (CV) cells in eight male and five female fetuses. Six of the male and three of the female fetuses were terminated. Simultaneous RFLP analysis provided confirmative data with flanking DNA markers in 3 of 13 analysed cases. Recombination and/or non-informativeness at available distal and/or proximal loci were found in nine cases. In one male fetus, discordance between the haplotype and cyto-genetics (fragile-X-negative) suggested the presence of a normal male transmitter, a double meiotic cross-over within the region, or a false-negative cytogenetic diagnosis. However, discordance between prenatal and post-termination/postnatal cytogenetic findings was not observed in this series. The use of excess thymidine for induction of the fragile X in cultured CV cells provided in the majority of cases a safe and rapid method for cytogenetic diagnosis, with options for early induced termination in fragile-X-positive pregnancies, for simultaneous RFLP analysis, and for subsequent second-trimester analysis of fetal blood in complicated cases.     

通辽北部农牧交错生态脆弱区农地利用强度与潜力分析

农牧交错生态脆弱区农业土地利用系统具有高敏感性特点,对其利用强度及潜力分析能够为区域土地可持续利用提供重要支持。论文基于农用地分等成果,在通辽市从北向南选取扎鲁特旗、科尔沁左翼中旗、开鲁县和科尔沁区作为典型区域,分析中国北方农牧交错带生态脆弱区农地产能差异及空间变异规律,并对该地区农地利用强度及增产潜力进行了研究。结果表明:①研究区北部和东北部产能较低,贯穿开鲁县由东北向西南延伸带状区域及科尔沁区沿西辽河分布的带状区域是研究区产能最高的区域;②西辽河平原区各层次产能均高于大兴安岭丘陵区,光、温、水、土等自然因素对产能产生主要影响,县区之间可实现产能差异性小于理论产能,利用和管理水平是产能发挥的根本;③理论利用强度自西南向东北递减,理论利用潜力自东向西递减,可实现产能利用强度自南向北递减,可实现利用潜力西高东低;④研究区中部和东南部属于粮食主产区,应加强农业技术的推广,着重解决土地利用粗放、非法占用耕地的问题;北部丘陵区应因地制宜,对不适耕种的区域建议还林还草,加强生态保护。     

脆弱生态环境指标库的建立及其定量评价

吉林西部曾是一个水草丰富的地方.近30 a来,由于人口剧增和人类对自然资源的过量开发,导致该地区干旱缺水、土地盐碱化和沙化,制约了环境的持续发展.笔者兼顾多方面因素,建立了脆弱生态环境指标体系,确定了脆弱生态环境定量评价的工作流程,包括数据库的建立、脆弱生态环境评价单元的确定、评价因子及其权重的确定、评价方法的确定,最后借助地理信息系统(GIS)强大的输入、空间分析及制图功能,采用层次分析法和综合指数法进行了生态环境脆弱度定量评价与分区.      

脆弱地质景观评价体系研究—以江西鹰潭龙虎山丹霞地貌景观为例

我国地质资源开发过程中对外部环境的抗干扰能力低、自身稳定性差、易破碎或消亡的脆弱地质景观缺乏足够认识。本文运用层次分析法建立脆弱地质景观评价体系,包含脆弱性和景观性两方面九个评价因子,并对评价因子赋值及划分脆弱地质景观等级。运用脆弱地质景观评价体系评价龙虎山丹霞地貌30处代表性景观,所得结果与实际调查吻合,且可为地质遗迹保护提供参考。     

Prenatal diagnosis of del(15)(q11q13)

A case of del(15)(q11q13) was detected in amniotic fluid cell cultures and confirmed by cordocentesis in a 27-year-old woman with a low maternal serum alpha-fetoprotein level. The fetus was shown to have a short femoral length on ultrasonography. This structural chromosome abnormality associated with the prenatal ultrasonographic findings and the morphological characteristics visualized after termination of pregnancy strongly suggest Prader-Willi syndrome.     

西部生态脆弱地区农业功能区划及模式探析——以宁夏盐池县为例

西部地区农业生产自然条件恶劣,生态系统脆弱,长期以来存在荒漠化、水土流失等威胁,而该区又属社会、经济发展相对缓慢的农业地区,如何在新农村建设中既实现农业产业化、专业化,又同时满足当地建设和保护生态环境的需求、发展地区循环经济,农业资源与环境的功能区划是重要前提。论文以该区典型农业县--宁夏盐池县农业生态经济系统为例,结合数学生态学模型与聚类分析模型,在地域区划基础上进一步解析其社会、经济功能分异,探讨该县农业功能空间分异格局,结果划分为5个农业功能区,并提出实现各区农业循环经济的发展模式及相应生态建设措施。     

黑液水煤浆技术在造纸黑液处理中的应用

介绍一种新的造纸黑液治理技术,即用造纸黑液制造黑液水煤浆通过燃烧实现造纸行业黑液无害化的目的。通过分析黑液水煤浆燃烧 残渣的成分和现场燃烧排气检测,探讨了燃烧残渣的资源化途径。      

生态脆弱区耕地集约利用水平分析

以米脂县高西沟村为例,通过构建耕地集约利用评价指标体系,利用主成分分析方法进行分析,探讨高西沟在实施有效的水土治理措施后,耕地集约利用情况,得出结论：1997—2006年米脂县高西沟村耕地集约利用情况呈波动上升趋势,1999～2001年出现下降趋势,这与当年的自然灾害有关;高西沟村非农指数、单位化肥投入、复种指数和人均纯收入,极大地影响到耕地的集约利用水平,说明农户的经济情况影响高西沟耕地集约利用程度。     

新疆干旱区某矿冶场对周围土壤重金属累积的影响

我国西部干旱半干旱地区为生态脆弱区,近年来西部工矿业发展引起的土壤污染问题越来越受到关注.本文通过空间布点采样,采用多元统计分析、GIS技术以及地积累指数评估等手段,对新疆某矿冶场区周围土壤的9种重金属污染特征进行了调查.结果表明,Cu和As元素为研究区域的主要重金属污染物;重金属Cr、Zn、Ni和Cd累积程度较轻、受人为干扰小;Co和Pb元素在少数样点存在人为干扰累积的现象,但程度也较轻;土壤中Mn没有明显累积和人为干扰.因子分析结果发现9种重金属主要存在2种来源,As、Cu、Ni、Cr、Zn、Cd和Co主要来源于第1种源;元素Mn和Pb主要来源于第2种源.从重金属空间分布特征可知,As、Cu、Ni、Cr、Zn、Pb、Cd和Co的最高含量样点都分布在尾砂库附近区域,因此对尾砂库进行封闭处理是减少重金属污染物向周围环境扩散的重要措施.此外,本研究还发现基于大气污染分析的PCA/APCS受体模型不适用于本案例中定量分析土壤重金属来源.