单链胰岛素前体在酵母中的分泌表达及其转变成人胰岛素

将化学合成的单链猪胰岛素前体(PIP)基因和用聚合酶链反应得到的α交配因子前导顺序(αMFL)基因插入质粒pVT102-U的醇脱氢酶基因ADH1的启动子和3’终止顺序之间而生成质粒pVT102-U/αMFL-PIP.被pVT102-U/αMFL-PIP转化的酵母(Saccharomyces cerevistae)可表达单链前体并分泌到培养基中.前体在纯化后可通过胰蛋白酶的转肽作用转变成人胰岛素.纯化的人胰岛素具有全部活力并可结晶.人胰岛素的总收率为每升培养液25mg.     

Molecular phylogeny of the springhare, Pedetes capensis, based on mitochondrial DNA sequences

The phylogenetic position of the Pedetidae, represented by a single species Pedetes capensis, is controversial, reflecting in part the retention of both Hystricomorphous and Sciurognathous characteristics in this rodent. In an attempt to clarify the species evolutionary relationships, mtDNA gene sequences from 10 rodent species (representing seven families) were analyzed using phenetic, parsimony, and maximum-likelihood methods of phylogenetic inference; the rabbit, Oryctolagus cuniculus (Order Lagomorpha), and cow, Bos taurus (Order Artiodactyla), were used as outgroups. Investigation of 714 base pairs of the protein-coding cytochrome b gene indicate strong base bias at the third codon position with significant rate heterogeneity evident between the three structural domains of this gene. Similar analyses conducted on 816 base pairs of the 12S rRNA gene revealed a transversion bias in the loop sections of all taxa. The cytochrome b gene sequences proved useful in resolving associations between closely related species but failed to produce consistent tree topologies at the family level. In contrast, phylogenetic analysis of the 12S rRNA gene resulted in strong support for the clustering of Pedetidae/Heteromyidae/Geomyidae and Muridae in one clade to the exclusion of the Hystricidae/Thryonomyidae and Sciuridae, a finding which is concordant with studies of rodent fetal membranes as well as reproductive and other anatomical features.      

Cranial variation amongst independent lineages of the alligator snapping turtle (Macrochelys temminckii)

Recent interest in diagnoses and relationships between lineages of the alligator snapping turtle (Macrochelys temminckii) present conflicting patterns of molecular variation across the taxon's range. This study uses geometric morphometric techniques to test molecular hypotheses. We analyse alligator snapping turtle cranial variation amongst populations (i.e. drainages) with the hypothesis that populations of turtles recovered as monophyletic by previous molecular studies are more similar to each other in cranial shape. Dorsal, lateral and ventral cranial shape analyses corroborate the uniqueness of populations recovered by molecular genetic hypotheses. Additionally, analyses reveal near equal separation between drainages that were assigned to monophyletic clades by previous phylogenetic studies. These results reveal the potential for more independent lineages that have yet to be diagnosed, and unique cranial shapes are described for our three most heavily sampled drainages.     

A note on the dominance hierarchy index

The realized (observed) value of Landau’s dominance hierarchy index is examined. Under a model of constant pairwise dominance probabilities, the observed index is shown to be a strongly consistent estimator of the underlying (true) index. However, a large number of encounters between animals is shown to be required in order to reduce bias and variance to practical levels except when the pairwise dominance probabilities are near one.     

New insights on facultative parthenogenesis in pythons

In vertebrates, facultative parthenogenesis (i.e. asexual reproduction by a sexually reproducing species) has been documented in four diverse taxonomic groups, namely sharks, birds, lizards, and snakes. With a single exception, the mode is terminal fusion automixis, where the second polar body fuses with the nucleus of the gamete, restoring diploidy and triggering cell division. The deviating case involves a report of a captive Burmese python (Python bivittatus), a giant Asiatic species common in zoological gardens and the pet trade. Although terminal fusion automixis produces half‐clones of the mother, under this unique case in P. bivittatus, the foetuses were reported as full clones. This conclusion is an apparent anomaly with respect to the mechanism of facultative parthenogenesis reported in all other snakes. In the present study, using genotyping methods, we analyze facultative parthenogenesis in two other species of pythonids and report results that challenge the abovementioned conclusions regarding clonality. Specifically, we report new findings comparable to those reported in other primitive snakes (namely boids), which support the hypothesis of terminal fusion automixis as the mode of facultative parthenogenesis. Furthermore, in light of our new data, we re‐examine the previous report of facultative parthenogenesis in the Burmese python and suggest an intriguing alternative explanation for the earlier findings. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 461–468.     

Tomato yellow leaf curl viruses: ménage à trois between the virus complex,the plant and the whitefly vector

Tomato yellow leaf curl disease (TYLCD) is one of the most devastating viral diseases affecting tomato crops in tropical, subtropical and temperate regions of the world. Here, we focus on the interactions through recombination between the different begomovirus species causing TYLCD, provide an overview of the interactions with the cellular genes involved in viral replication, and highlight recent progress on the relationships between these viruses and their vector, the whitefly Bemisia tabaci. Taxonomy: The tomato yellow leaf curl virus‐like viruses (TYLCVs) are a complex of begomoviruses (family Geminiviridae, genus Begomovirus) including 10 accepted species: Tomato yellow leaf curl Axarquia virus (TYLCAxV), Tomato yellow leaf curl China virus (TYLCCNV), Tomato yellow leaf curl Guangdong virus (TYLCGuV), Tomato yellow leaf curl Indonesia virus (TYLCIDV), Tomato yellow leaf curl Kanchanaburi virus (TYLVKaV), Tomato yellow leaf curl Malaga virus (TYLCMalV), Tomato yellow leaf curl Mali virus (TYLCMLV), Tomato yellow leaf curl Sardinia virus (TYLCSV), Tomato yellow leaf curl Thailand virus (TYLCTHV), Tomato yellow leaf curl Vietnam virus (TYLCVNV) and Tomato yellow leaf curl virus(TYLCV). We follow the species demarcation criteria of the International Committee on Taxonomy of Viruses (ICTV), the most important of which is an 89% nucleotide identity threshold between full‐length DNA‐A component nucleotide sequences for begomovirus species. Strains of a species are defined by a 93% nucleotide identity threshold. Host range: The primary host of TYLCVs is tomato (Solanum lycopersicum), but they can also naturally infect other crops [common bean (Phaseolus vulgaris), sweet pepper (Capsicum annuum), chilli pepper (C. chinense) and tobacco (Nicotiana tabacum)], a number of ornamentals [petunia (Petunia×hybrida) and lisianthus (Eustoma grandiflora)], as well as common weeds (Solanum nigrum and Datura stramonium). TYLCVs also infect the experimental host Nicotiana benthamiana. Disease symptoms: Infected tomato plants are stunted or dwarfed, with leaflets rolled upwards and inwards; young leaves are slightly chlorotic; in recently infected plants, fruits might not be produced or, if produced, are small and unmarketable. In common bean, some TYLCVs produce the bean leaf crumple disease, with thickening, epinasty, crumpling, blade reduction and upward curling of leaves, as well as abnormal shoot proliferation and internode reduction; the very small leaves result in a bushy appearance.     

The co-distribution of Plasmodium falciparum and hookworm among African schoolchildren

Background

On the island of Bioko (Equatorial Guinea), insecticide-treated nets (ITNs) have been the main tool used to control malaria over the last 13 years. In 2004, started an indoor residual spraying (IRS) campaign to control malaria. The purpose of this study is to asses the impact of the two control strategies on the island of Bioko (Equatorial Guinea), with regards to Plasmodium infection and anaemia in the children under five years of age.

Methods

Two transversal studies, the first one prior to the start of the IRS campaign and the second one year later. Sampling was carried out by stratified clusters. Malaria infection was measured by means of thick and thin film, and the packed cell volume (PCV) percentage. Data related to ITN use and information regarding IRS were collected. The Pearson's chi-square and logistic regression statistical tests were used to calculate odds ratios (OR)

Results

In the first survey, 168 children were sampled and 433 children in the second one. The prevalence of infection was 40% in 2004, and significantly lower at 21.7% in 2005. PCV was 41% and 39%, respectively. 58% of the children surveyed in 2004 and 44.3% in 2005 had slept under an ITN. 78% of the dwellings studied in 2005 had been sprayed. In the 2005 survey, sleeping without a mosquito net meant a risk of infection 3 times greater than sleeping protected with a net hanged correctly and with no holes (p < 0.05).

Conclusion

IRS and ITNs have proven to be effective control strategies on the island of Bioko. The choice of one or other strategy is, above all, a question of operational feasibility and availability of local resources.     

Two-dimensional informative array testing

Summary Array-based group-testing algorithms for case identification are widely used in infectious disease testing, drug discovery, and genetics. In this article, we generalize previous statistical work in array testing to account for heterogeneity among individuals being tested. We first derive closed-form expressions for the expected number of tests (efficiency) and misclassification probabilities (sensitivity, specificity, predictive values) for two-dimensional array testing in a heterogeneous population. We then propose two "informative" array construction techniques which exploit population heterogeneity in ways that can substantially improve testing efficiency when compared to classical approaches that regard the population as homogeneous. Furthermore, a useful byproduct of our methodology is that misclassification probabilities can be estimated on a per-individual basis. We illustrate our new procedures using chlamydia and gonorrhea testing data collected in Nebraska as part of the Infertility Prevention Project.