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The fragile X syndrome is a common cause of mental retardation and is associated with a fragile site at Xq27.3 (FRAXA). Recently, evidence has been presented for the role of methylation and genomic imprinting in the expression of the disease. We have identified a site of methylation in patients by long range restriction mapping of the region. In this paper we present a YAC contig of this area, localise the CpG sequences which are methylated, and show by in situ hybridisation that the site of fragility lies within this region.  相似文献   
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In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera9. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo10,11, which has been tentatively attributed to its unblocking activity8,9 or, possibly, to a complement-dependent cytotoxicity10. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity9,10.  相似文献   
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Microarray-based pooled DNA experiments that combine the merits of DNA pooling and gene chip technology constitute a pivotal advance in biotechnology. This new technique uses pooled DNA, thereby reducing costs associated with the typing of DNA from numerous individuals. Moreover, use of an oligonucleotide gene chip reduces costs related to processing various DNA segments (e.g., primers, reagents). Thus, the technique provides an overall cost-effective solution for large-scale genomic/genetic research. However, few publicly shared tools are available to systematically analyze the rapidly accumulating volume of whole-genome pooled DNA data.  相似文献   
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Application of the functional-form model to the culture of seaweeds   总被引:1,自引:1,他引:0  
Selecting the most appropriate species or strains is an important first step in the development of most algal cultivation systems and is usually a tedious, time-consuming, and expensive step. The functional-form model, first developed to synthesize the adaptive significance of easily assessed thallus-form attributes relative to the productivity and survival of benthic macroalgae, is applicable to the culture of seaweeds and can expedite species or strain selection. The production ecology aspects of the model are useful particularly for applications where the desired product is not species-specific, e.g., systems in which the emphasis is on algal production, such as algal biomass farms and wastewater treatment. A thallus-form with a high surface area: volume ratio is more suited for rapid production and nutrient uptake. The utility of this model to strain selection is demonstrated with the red alga Gracilaria tikvahiae, a species that has been considered a maricultural candidate for a number of utilizations. A continuum of surface area: volume ratios for eight clones of G. tikvahiae showed that this ratio decreased as morphological complexity increased and was a good predictor of both short-term photosynthesis and long-term growth rate. Clones near opposite ends of the surface area: volume ratio spectrum had significant differences for both photosynthesis and growth. Each clone of G. tikvahiae possesses concomitant combinations of benefits as well as costs, which should be carefully evaluated for the cultivation application of interest. Knowledge of functional-form relationships in seaweeds can significantly expedite their successful cultivation.  相似文献   
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Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.  相似文献   
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