Mutations in the gene encoding 11-cis retinol dehydrogenase cause delayed dark adaptation and fundus albipunctatus.

The metabolic pathways that produce 11-cis retinal are important for vision because this retinoid is the chromophore residing in rhodopsin and the cone opsins. The all-trans retinal that is generated after cone and rod photopigments absorb photons of light is recycled back to 11-cis retinal by the retinal pigment epithelium and Müller cells of the retina. Several of the enzymes involved have recently been purified and molecularly cloned; here we focus on 11-cis retinol dehydrogenase (encoded by the gene RDH5; chromosome 12q13-14; ref. 4), the first cloned enzyme in this pathway. This microsomal enzyme is abundant in the retinal pigment epithelium, where it has been proposed to catalyse the conversion of 11-cis retinol to 11-cis retinal. We evaluated patients with hereditary retinal diseases featuring subretinal spots (retinitis punctata albescens and fundus albipunctatus) and patients with typical dominant or recessive retinitis pigmentosa for mutations in RDH5. Mutations were found only in two unrelated patients, both with fundus albipunctatus; they segregated with disease in the respective families. Recombinant mutant 11-cis retinol dehydrogenases had reduced activity compared with recombinant enzyme with wild-type sequence. Our results suggest that mutant alleles in RDH5 are a cause of fundus albipunctatus, a rare form of stationary night blindness characterized by a delay in the regeneration of cone and rod photopigments.     

测井资料分析系统接口电路设计

从一种超声模拟测井记录的井下信号、深度信号送微机处理的实际要求出发，分析井下信号数据采集的工作原理，阐述了与１２位Ａ／Ｄ转换器实时配套工作的双存储体工作时序。通过对深度信号的解调，提出了一种解决４ＦＳＫ解调的有效方法。     

BP网络的抗干扰性研究及误差分析

从ＢＰ网络对信息存储的分布式特点出发，分析了连接权系数及输入变化对输出的影响，探讨了ＢＰ网络的容错性及抗干扰特性，得出了一些有益的结论。     

任意波形合成系统硬件设计

提出并分析了任意波形合成系统（ＡＷＳ）──一种高度智能化的计算机仪器的几种典型结构及其特点，着重讨论了ＰＣ总线式任意波形合成系统的系统组成及各部分硬件电路设计的关键技术     

High frequency of unequal recombination in pseudoautosomal region shown by proviral insertion in transgenic mouse

The mammalian X and Y chromosomes, in contrast to the autosomes, pair during male meiosis only near the telomeres. Alleles localized in this region can undergo reciprocal exchange during meiosis. Because such sequences do not show strict sex-linked inheritance, they have been termed pseudoautosomal. In man, several DNA sequences have been described which show pseudoautosomal transmission and which are localized in the pairing region at the ends of the short arms of both the X and Y chromosomes (refs 6-9, and D. Page, unpublished results). We now show that the transgenic mouse strain, Mov-15, contains a single Moloney murine leukaemia virus (M-MuLV) genome in its germline, and genetic evidence indicates that the provirus is integrated into the pseudoautosomal region of the sex chromosome. Proviral copies are lost or gained in 7% of male meioses in this strain, and mouse sequences flanking the provirus are tandemly repeated and highly variable. We conclude that unequal recombination events occur with high frequency in the pairing region, possibly because of the presence of repeated sequences.     

Bone marrow genotoxicity of N-methyl, N-nitrosourea (NMU): n-alkanols as sister chromatid exchange (SCE) anti-inducers

The in vivo SCE test was used to demonstrate significant inhibition of NMU bone marrow genotoxicity by pretreatment of Chinese hamsters with n-alkanols. Our findings exclude a loss of intracellular DNA alkylation potential through a competitive direct reaction of NMU with the weakly nucleophilic polar end of the n-alkanols, but not through methylations of nucleophilic membrane sites possibly liberated by structural modifications which the membrane-active amphiphilics induce.