Snake venom components and their applications in biomedicine

Snake envenomation is a socio-medical problem of considerable magnitude. About 2.5 million people are bitten by snakes annually, more than 100,000 fatally. However, although bites can be deadly, snake venom is a natural biological resource that contains several components of potential therapeutic value. Venom has been used in the treatment of a variety of pathophysiological conditions in Ayurveda, homeopathy and folk medicine. With the advent of biotechnology, the efficacy of such treatments has been substantiated by purifying components of venom and delineating their therapeutic properties. This review will focus on certain snake venom components and their applications in health and disease. Received 6 July 2006; received after revision 14 August 2006; accepted 28 September 2006     

Phytanic acid: production from phytol, its breakdown and role in human disease

Phytanic acid is a branched-chain fatty acid that accumulates in a variety of metabolic disorders. High levels of phytanic acid found in patients can exceed the millimolar range and lead to severe symptoms. Degradation of phytanic acid takes place by α-oxidation inside the peroxisome. A deficiency of its breakdown, leading to elevated levels, can result from either a general peroxisomal dysfunction or from a defect in one of the enzymes involved in α-oxidation. Research on Refsum disease, belonging to the latter group of disorders and characterized by a deficiency of the first enzyme of α-oxidation, has extended our knowledge of phytanic acid metabolism and pathology of the disease greatly over the past few decades. This review will centre on this research on phytanic acid: its origin, the mechanism by which its α-oxidation takes place, its role in human disease and the way it is produced from phytol. Received 4 October 2005; received after revision 24 February 2006; accepted 26 April 2006     

Truncating mutations in the Fanconi anemia J gene BRIP1 are low-penetrance breast cancer susceptibility alleles

We identified constitutional truncating mutations of the BRCA1-interacting helicase BRIP1 in 9/1,212 individuals with breast cancer from BRCA1/BRCA2 mutation-negative families but in only 2/2,081 controls (P = 0.0030), and we estimate that BRIP1 mutations confer a relative risk of breast cancer of 2.0 (95% confidence interval = 1.2-3.2, P = 0.012). Biallelic BRIP1 mutations were recently shown to cause Fanconi anemia complementation group J. Thus, inactivating truncating mutations of BRIP1, similar to those in BRCA2, cause Fanconi anemia in biallelic carriers and confer susceptibility to breast cancer in monoallelic carriers.     

Huntington’s disease: from huntingtin function and dysfunction to therapeutic strategies

Huntington’s disease (HD) is a neurodegenerative disorder that usually starts in middle age and is characterized by involuntary movements (chorea), personality changes and dementia, leading to death within 10–20 years. The defective gene in HD contains a trinucleotide CAG repeat expansion within its coding region that expresses a polyglutamine repeat in the protein huntingtin. Together with the characteristic formation of aggregates in HD, aberrant protein interactions and several post-translational modifications affect huntingtin during disease progression and lead to the dysfunction and death of selective neurons in the brains of patients. The exact molecular mechanisms by which mutant huntingtin induces cell death are not completely understood but may involve the gain of new toxic functions and the loss of the beneficial properties of huntingtin. This review focuses on the cellular functions in which huntingtin is involved and how a better understanding of pathogenic pathways can lead to new therapeutic approaches. Received 24 May 2006; received after revision 5 July 2006; accepted 23 August 2006     

植物标签技术

传统的正向遗传学主要用于克隆表型或功能已确定的基因。转座子标签突变体可用随机标签法从带有活性转座子的自交后代中筛选得到,或用定向标签法从杂交一代中筛选得到,即用目的基因的隐性突变统合体与具高度活性转座号的统合体杂交,极大多数的FI个体为正常表型,但其中会有极少量的表现隐性性状的转庄子插入突变体。正向基因标签和克隆法在利用异源和低拷贝数品系时尤其有用。采用反向fCR或热不对称交替PCR（TAIL－PCR）且很容易从单拷贝或低拷贝数品系中获得插入于两侧的基因组序列。TAIL－PCR由三轮连续的半巢式PCR组成,所…     

Mixtures of Autoregressions with an Improper Component for Panel Data

An EM algorithm for fitting mixtures of autoregressions of low order is constructed and the properties of the estimators are explored on simulated and real datasets. The mixture model incorporates a component with an improper density, which is intended for outliers. The model is proposed as an alternative to the search for the order of a single-component autoregression. The methods can be adapted to other patterns of dependence in panel data. An application to the monthly records of income of the outlets of a retail company is presented.     

Transthyretin: a review from a structural perspective

Transthyretin (formerly called prealbumin) plays important physiological roles as a transporter of thyroxine and retinol-binding protein. X-ray structural studies have provided information on the active conformation of the protein and the site of binding of both ligands. Transthyretin is also one of the precursor proteins commonly found in amyloid deposits. Both wild-type and single-amino-acid-substituted variants have been identified in amyloid deposits, the variants being more amyloidogenic. Sequencing of the gene and the resulting production of a transgenic mouse model have resulted in progress toward solving the mechanism of amyloid formation and detecting the variant gene in individuals at risk. Received 23 January 2001; received after revision 4 April 2001; accepted 30 April 2001