血管活性肠多肽结合核苷酸性质的研究

采用光亲和技术检测了血管活性肠多肽(VIP)与核苷酸之间的相互作用,发现VIP可以特异性结合同位素标记的GTP,还发现未标记的GTP以及其它三磷酸核苷抑制这种结合,这意味着VIP与上述三磷酸核苷之间的结合是一种典型的可逆性的结合反应.发现低浓度的GDP,GMP不但不抑制VIP与同位素标记GTP的结合反应,反而增强这种结合.联系到其它研究者关于GTP影响VIP与其受体结合反应的结果,可认为VIP能可逆性地连接一种三磷酸核苷,这种连接受反应系统中不同核苷酸比例影响,通过这种连接来调节VIP与其受体之间的反应.     

Low codon bias and high rates of synonymous substitution in Drosophila hydei and D. melanogaster histone genes

We have evaluated codon usage bias in Drosophila histone genes and have obtained the nucleotide sequence of a 5,161-bp D. hydei histone gene repeat unit. This repeat contains genes for all five histone proteins (H1, H2a, H2b, H3, and H4) and differs from the previously reported one by a second EcoRI site. These D. hydei repeats have been aligned to each other and to the 5.0-kb (i.e., long) and 4.8-kb (i.e., short) histone repeat types from D. melanogaster. In each species, base composition at synonymous sites is similar to the average genomic composition and approaches that in the small intergenic spacers of the histone gene repeats. Accumulation of synonymous changes at synonymous sites after the species diverged is quite high. Both of these features are consistent with the relatively low codon usage bias observed in these genes when compared with other Drosophila genes. Thus, the generalization that abundantly expressed genes in Drosophila have high codon bias and low rates of silent substitution does not hold for the histone genes.      

Survival of boll weevil （Coleoptera： Curculionidae） adults after feeding on pollens from various sources

The survival of overwintering boll weevil, Anthonomus grandis grandis （Boheman）, adults on non-cotton hosts in the Lower Rio Grande Valley （LRGV） of Texas was examined from 2001 to 2006. The success of the Boll Weevil Eradication Program, which was reintroduced into the LRGV in 2005, depends on controlling overwintering boll weevil populations. Laboratory studies were conducted using boll weevil adults that were captured in pheromone traps from September through March. The number of adults captured per trap declined significantly in the field from fall to the beginning of spring （3.5-7.0-fold）. The proportion of trapped males and females did not differ significantly. The mean weight of boll weevil adults captured in September was 13.3 mg, while those of captured adults from November to February were significantly lower and ranged from 6.7 to 7.8 mg. Our results show that boll weevil adults can feed on different plant pollens. The highest longevity occurred when adults were fed almond pollen or mixed pollens （72.6 days and 69.2 days, respectively） and the lowest when they fed on citrus pollen or a non-food source （9.7 days or 7.4 days, respectively）. The highest adult survival occurred on almond and mixed pollens [88.0%-97. 6% after 1st feeding period （10 days）, 78.0%-90.8% after 3rd feeding period （10 days）, 55. 0%-83.6% after 5th feeding period （10 days）, and 15.2%-32.4% after lOth feeding period （10 days）]. The lowest adult survival occurred on citrus pollen [52.0%-56.0% after 1st feeding period （10 days）, 13.3% after 3rd and 5th feeding periods （10 days）, and 0 after 6th feeding period （10 days）]. Pollen feeding is not a behavior restricted to adult boll weevils of a specific sex or physiological state. Understanding how boll weevil adults survive in the absence of cotton is important to ensure ultimate success of eradicating this pest in the subtropics.