Microorganisms associated with chromosome destruction and reproductive isolation between two insect species

Microorganisms have been implicated in causing cytoplasmic incompatibility in a variety of insect species, including mosquitoes, fruitflies, beetles and wasps. The effect is typically unidirectional: incompatible crosses produce no progeny or sterile males, whereas the reciprocal crosses produce normal progeny. The parasitic wasp Nasonia vitripennis is one of the few species in which the cytogenetic mechanism of incompatibility is known. In this species the paternal chromosome set forms a tangled mass in a fertilized egg and is eventually lost. Here we report that cytoplasmic microorganisms are associated with complete bidirectional incompatibility between N. vitripennis and a closely related sympatric species, N. giraulti. Microorganisms can be seen in the eggs of both species. Hybrid offspring are normally not produced in crosses between the two species, but do occur after elimination of the microorganisms by antibiotic treatment. A cytogenetic and genetic study shows that bidirectional interspecific incompatibility is due to improper condensation of the paternal chromosomes. Microorganism-mediated reproductive isolation is of interest because it could provide a rapid mode of speciation. The mechanism of incompatibility in Nasonia is also of interest as a potential tool for studying chromosome imprinting and chromosome condensation.     

Transduction and rearrangement of the myc gene by feline leukaemia virus in naturally occurring T-cell leukaemias

Evidence of myc gene transduction by feline leukaemia virus in several spontaneous lymphoid tumours of cats suggests that recombinant viruses carrying oncogenes may be much more involved in oncogenesis in natural conditions than previously recognized.     

The concepts of 'sameness' and 'difference' in an insect

Insects process and learn information flexibly to adapt to their environment. The honeybee Apis mellifera constitutes a traditional model for studying learning and memory at behavioural, cellular and molecular levels. Earlier studies focused on elementary associative and non-associative forms of learning determined by either olfactory conditioning of the proboscis extension reflex or the learning of visual stimuli in an operant context. However, research has indicated that bees are capable of cognitive performances that were thought to occur only in some vertebrate species. For example, honeybees can interpolate visual information, exhibit associative recall, categorize visual information and learn contextual information. Here we show that honeybees can form 'sameness' and 'difference' concepts. They learn to solve 'delayed matching-to-sample' tasks, in which they are required to respond to a matching stimulus, and 'delayed non-matching-to-sample' tasks, in which they are required to respond to a different stimulus; they can also transfer the learned rules to new stimuli of the same or a different sensory modality. Thus, not only can bees learn specific objects and their physical parameters, but they can also master abstract inter-relationships, such as sameness and difference.     

Analysis and evaluation of insect species diversity in Zyginellini from Southwest China karst area

笔者通过查阅网络数据库及相关国内外文献资料的记载,初步整理了截至目前我国有分布的塔叶蝉昆虫种类共计13属54种,其中在西南3省喀斯特地区有分布的为8属33种。同时对西南3省已报道塔叶蝉的物种多样性进行了简单分析和评价。     

中国西南喀斯特地区Zyginellini族昆虫物种多样性分析与评价

笔者通过查阅网络数据库及相关国内外文献资料的记载,初步整理了截至目前我国有分布的塔叶蝉昆虫种类共计13属54种,其中在西南3省喀斯特地区有分布的为8属33种。同时对西南3省已报道塔叶蝉的物种多样性进行了简单分析和评价。     

Nitrogen content features of several indigenous evergreen and decidous tree species in Chongqing region

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A natural polymorphism alters odour and DEET sensitivity in an insect odorant receptor

Blood-feeding insects such as mosquitoes are efficient vectors of human infectious diseases because they are strongly attracted by body heat, carbon dioxide and odours produced by their vertebrate hosts. Insect repellents containing DEET (N,N-diethyl-meta-toluamide) are highly effective, but the mechanism by which this chemical wards off biting insects remains controversial despite decades of investigation. DEET seems to act both at close range as a contact chemorepellent, by affecting insect gustatory receptors, and at long range, by affecting the olfactory system. Two opposing mechanisms for the observed behavioural effects of DEET in the gas phase have been proposed: that DEET interferes with the olfactory system to block host odour recognition and that DEET actively repels insects by activating olfactory neurons that elicit avoidance behaviour. Here we show that DEET functions as a modulator of the odour-gated ion channel formed by the insect odorant receptor complex. The functional insect odorant receptor complex consists of a common co-receptor, ORCO (ref. 15) (formerly called OR83B; ref. 16), and one or more variable odorant receptor subunits that confer odour selectivity. DEET acts on this complex to potentiate or inhibit odour-evoked activity or to inhibit odour-evoked suppression of spontaneous activity. This modulation depends on the specific odorant receptor and the concentration and identity of the odour ligand. We identify a single amino-acid polymorphism in the second transmembrane domain of receptor OR59B in a Drosophila melanogaster strain from Brazil that renders OR59B insensitive to inhibition by the odour ligand and modulation by DEET. Our data indicate that natural variation can modify the sensitivity of an odour-specific insect odorant receptor to odour ligands and DEET. Furthermore, they support the hypothesis that DEET acts as a molecular 'confusant' that scrambles the insect odour code, and provide a compelling explanation for the broad-spectrum efficacy of DEET against multiple insect species.     

Thermodynamic Assessment of Reactions between Yttrium and Tramp Elements in Petroleum Pipe Steel

In the thermodynamic evaluation Y was selected as a typical heavy rare earth metal for reducing the detrmental effects of tramp elements in the petroleum pipe steel. The possibilities of reactions between Y and tramp elements such as Sn, Sb, As, etc. after deoxidation and desulphurization were estimated by calculating the Gibbs free energies of formation. The equilibrium content of Y for eliminating the detrimental effects of tramp elements in the steel was recommended from the results of thermodynamic calculation.     

关于我国开展银保合作的几点思考

随着我国市场经济和金融业的发展，银保合作得到了加强，并显示出强大的发展后劲。银保合作是双方有效拓展市场的良好选择。我国的银保合作具有多种形式，以中国民生银行为代表的多家银行、保险企业，已通过银保合作业务取得了令人瞩目的成绩。     

Quantitative relationships between vegetation and several pollen taxa in surface soil from North China

According to the vegetation investigation and pollen analysis of surface samples sampled along a precipitation gradient of the Northeast China Transect (NECT), several pollen taxa, includingPinus, Betula, Quercus, Tilia, Acer, Ulmus, Artemisia, Chenopodiaceae, Gramineae and Cyperaceae, were chosen to make the regression and correlation analyses. The results indicated that there exists a close relationship between vegetation and pollen taxa in surface samples. The regression parameters for ten taxa in the forests in the eastern part of NECT were different from those in the steppes in the western part.Pinus, Betula, Artemisia and Chenopodiaceae, which have large slope and y-intercept terms, were over-representative taxa.Acer, Gramineae and Cyperaceae, which have small slope andy-intercept terms, were under-representative taxa.Quercus, Tilia andUlmus whose slope terms have negative correlation withy-intercept terms were equi-representative taxa. The pollen taxa with large slope or largey-intercept terms have small variability coefficients, implying that the slope andy-intercept terms for these pollen taxa are of high accuracy in the estimation of plant abundance from pollen frequencies.