A novel ABCG-like transporter of Trypanosoma cruzi is involved in natural resistance to benznidazole

Benznidazole (BZ) is one of the two drugs used for Chagas disease treatment. Nevertheless therapeutic failures of BZ have been reported, which were mostly attributed to variable drug susceptibility among Trypanosoma cruzi strains. ATP-binding cassette (ABC) transporters are involved in a variety of translocation processes and some members have been implicated in drug resistance. Here we report the characterisation of the first T. cruzi ABCG transporter gene, named TcABCG1, which is over-expressed in parasite strains naturally resistant to BZ. Comparison of TcABCG1 gene sequence of two TcI BZ-resistant strains with CL Brener BZ-susceptible strain showed several single nucleotide polymorphisms, which determined 11 amino acid changes. CL Brener transfected with TcI transporter genes showed 40-47% increased resistance to BZ, whereas no statistical significant increment in drug resistance was observed when CL Brener was transfected with the homologous gene. Only in the parasites transfected with TcI genes there was 2-2.6-fold increased abundance of TcABCG1 transporter protein. The analysis in wild type strains also suggests that the level of TcABCG1 transporter is related to BZ natural resistance. The characteristics of untranslated regions of TcABCG1 genes of BZ-susceptible and resistant strains were investigated by computational tools.     

天敌昆虫抗药性研究进展

天敌昆虫抗药性研究在协调害虫化学防治和生物防治中有着重要的理论和现实意义,其研究的最终目的在于更好地推进抗性天敌在害虫综合治理(IPM)中的应用。抗药性天敌昆虫具有潜在的巨大价值。鉴于此,本文系统地综述了天敌昆虫抗药性最新研究进展,包括杀虫剂对天敌昆虫的影响、天敌昆虫抗药性现状、抗药性机理和限制天敌昆虫抗药性发展因素等。文章最后还对抗药性天敌昆虫的应用前景进行了展望。     

提高摄食-反捕食能力导向的鱼类野化训练方法述评

鱼类的人工增殖放流未达到预期效果,原因之一是人工放流的鱼在放流后死亡率很高.鱼类在放流前的野化训练可能对提高其成活率有积极作用.本文分析了国内外增殖鱼类放流后成活率低的原因,指出摄食-反捕食能力是影响鱼类放流后成活率的关键要素之一;探讨了影响摄食-反捕食能力的重要因素,包括认知食物和捕食者信息、社会学习经验、环境的复杂程度和鱼类的游泳能力等;展望了鱼类野化训练技术的发展方向.     

A review of the gobioid fish genusgobioides

The gobioid genusGobioides Lacepède, 1800 shares with the amblyopine gobies (Gobiidae: Amblyopinae) an eel-like, elongate body with a continuous dorsal fin and an affinity for shallow water, muddy bottom habitats. Due to similarities in external morphology and habitat requirements, some workers consideredGobioides allied with amblyopine gobies. Others, however, dispute a close relationship betweenGobioides and the Amblyopinae; morphological and ecological similarities are considered to be homoplasious. Results of this study concur with placingGobioides separate from amblyopine gobies and within the gobiid subfamily Gobionellinae.Gobioides is easily distinguished from the Amblyopinae by its larger eyes (small inGobioides vs. inconspicuous in the Amblyopinae), fewer dorsal and anal-fin rays (14–20 vs. 27–48), and different fin element to vertebra ratios (1∶1 vs. 2∶1).Gobioides reaches lengths of 500 mm SL or greater whereas amblyopines rarely exceed 300 mm SL.Gobioides comprises five species (G. africanus, G. broussoneti, G. grahamae, G. peruanus, andG. sagitta). Although these gobies occupy habitats with similar conditions,Gobioides and amblyopines are nowhere sympatric.Gobioides occurs in tropical and subtropical coastal waters of the eastern and western Atlantic as well as the tropical eastern Pacific Ocean. In the eastern Atlantic.Gobioides is known from Senegal to Zaire. In the western Atlantic.Gobioides is reported from South Carolina to southern Brazil. In the eastern Pacific,Gobioides is known from Mexico to Peru.     

Host factors involved in resistance to retroviral infection

Viral replication requires the help of host cell factors, whose species specificity may affect viral tropism. On the other hand, there exist host factors that restrict viral replication. The anti-viral system mediated by some of these restriction factors, which is termed intrinsic immunity and is distinguished from conventional innate and adaptive immunity, has been described as playing an important role in making species-specific barriers against viral infection. Here, we describe the current progress in understanding of such restriction factors against retroviral replication, focusing on TRIM5alpha and APOBEC, whose anti-retroviral effects have recently been recognized. Additionally, we mention cyclophilin A, which is essential for HIV-1 replication in human cells and may affect viral tropism. Understanding of these host factors would contribute to identification of the determinants for viral tropism.     

A review of chemical communication in freshwater fish

Since communication between individuals of a species of fish by chemical agents (pheromones) was first demonstrated in 1932, such a process has been suggested in many aspects of fish behavidïo'ur and development. This review describes observations on such mechanisms in shoaling behaviour and beneficial conditioning of water, homing of migratory fish, communication of alarm, 'crowding factor' (which adversely affects growth, survival and fecundity in dense populations), pair formation and spawning, and a range of other social interactions. Some of the chemicals involved have been isolated and identified, but most are indicated by behavioural observations. Pheromones are of great significance in fish behaviour and ecology, and are likely to be an important factor in culture operations.     

Genetic resistance to rhabdovirus infection in teleost fish is paralleled to the derived cell resistance status

Genetic factors of resistance and predisposition to viral diseases explain a significant part of the clinical variability observed within host populations. Predisposition to viral diseases has been associated to MHC haplotypes and T cell immunity, but a growing repertoire of innate/intrinsic factors are implicated in the genetic determinism of the host susceptibility to viruses. In a long-term study of the genetics of host resistance to fish rhabdoviruses, we produced a collection of double-haploid rainbow trout clones showing a wide range of susceptibility to Viral Hemorrhagic Septicemia Virus (VHSV) waterborne infection. The susceptibility of fibroblastic cell lines derived from these clonal fish was fully consistent with the susceptibility of the parental fish clones. The mechanisms determining the host resistance therefore did not associate with specific host immunity, but rather with innate or intrinsic factors. One cell line was resistant to rhabdovirus infection due to the combination of an early interferon IFN induction--that was not observed in the susceptible cells--and of yet unknown factors that hamper the first steps of the viral cycle. The implication of IFN was well consistent with the wide range of resistance of this genetic background to VSHV and IHNV, to the birnavirus IPNV and the orthomyxovirus ISAV. Another cell line was even more refractory to the VHSV infection through different antiviral mechanisms. This collection of clonal fish and isogenic cell lines provides an interesting model to analyze the relative contribution of antiviral pathways to the resistance to different viruses.     

A review of the use of copepods in marine fish larviculture

In spite of the growing interest and success obtained using cultured-copepods, their use in marine aquaculture remains sporadic. Besides, mass culture of several marine copepods has been well established by several authors. However, the upscale of copepod cultures to commercial levels is still a challenge. The practice of using wild copepods from natural ponds which thus increases the risk of parasitic infections of most species has limited their application in aquaculture. The present paper thus emphasizes on recent research efforts focused on the use of chemical treatments and freeze-thawing methods to eradicate procercoids from copepods. Research efforts focused on copepod culture systems which subsequently improved and refined their culture in marine fish larviculture are also well discussed. Advances in the use of copepod eggs as potential source of nauplii for marine fish larvae with special emphasis on the viability, storage conditions and biochemical compositions of the copepod eggs are underscored. Additionally, recent advances in the biochemical compositions (protein, amino acids, pigments, and vitamins) of copepods, which has received relatively little attention compared to researches on the lipid and fatty acid compositions are well emphasized. Specific recommended areas for further research are also proffered.     

A review of some fish nutrition methodologies

Several classical warm blooded animal (poultry, sheep, cows, etc.) methods for dietary nutrients evaluation (digestibility, metabolizablity, and energy budget) are applied to fish, even though fish live in a different environment in addition to being cold blooded animals. These applications have caused significant errors that have made these methods non-additive and meaningless, as is explained in the text. In other words, dietary digestion and absorption could not adequately be measured due to the aquatic environment fish live in. Therefore, net nutrient deposition and/or growth are the only accurate measurement left to evaluate dietary nutrients intake in fish. In order to understand and predict dietary nutrient intake-growth response relationship, several mathematical models; (1) the simple linear equation, (2) the logarithmic equation, and (3) the quadratic equation are generally used. These models however, do not describe a full range of growth and have no biological meaning as explained in the text. On the other hand, a model called the saturation kinetic model. It has biological basis (the law of mass action and the enzyme kinetic) and it describes the full range of growth curve. Additionally, it has four parameters that summarize the growth curve and could also be used in comparing diets or nutrients effect on fish growth and/or net nutrient deposition. The saturation kinetic model is proposed to be adequate for dietary nutrient evaluation for fish. The theoretical derivation of this model is illustrated in the text.     

The leucocytes of fish: A review

The data available in the literature concerning fish thrombocytes, lymphocytes, monocytes, macrophages and granulocytes is discussed and the dearth of reliable information concerning the functional identity of most fish leucocytes is underlined. The methods of applying nomenclatures to fish leucocytes encountered in the literature is discussed in some detail and found to be unsatisfactory. An attempt is made to simplify the confused and conflicting reports by applying the concepts which have recently arisen in the field of mammalian immunology. Nomenclatures are assigned to cells on a functional and morphological basis where sufficient data exists.
Thrombocytes are responsible for clot formation and are considered to be distinct, separate and unrelated to lymphocytes. Lymphocytes are recognised as immuno-competent cells though as yet little information exists on their role in immune mechanisms. Recent work is furnishing interesting results in this direction, especially in the origin of lymphocyte populations and their co-operative responses in immunity. Previous references to monocytes and macrophages in fish are confused and the literature is discussed in the light of the new classification of the Mononuclear Phagocyte System.
Very few experimental data exist concerning granulocytic leucocytes in fish, indeed the presence of such cells with granulocytic functions still requires proof. Cells with morphological similarity to mammalian granulocytes do exist in fish but information essential for an understanding of their role in defence mechanisms is lacking. The state of the literature concerning the eosinophil, basophil and mast cell in fish is so confused that an entirely new approach to a study of these cells is warranted. It is hoped that this review will supply guidelines for future research.     

鱼类个性测定方法研究进展

动物个性是指在不同时空条件下动物种内个体间行为的稳定差异.鱼类个性的研究历史已超过50年,但不同时期和不同研究的鱼类个性测定方法存在较大差异,缺乏一个规范的用于量化鱼类个性研究的方法论.本文作者认为,关注鱼类个性的常规测定方法,了解现有个性定义及其生态学意义,规范鱼类个性的常规实验方法是有必要的.本文所涉及的个性是指狭...     

Total synthesis of the natural antigen involved in the hyperacute rejection response to xenotransplants

The major glycosphingolipid in pig vascular endothelium is the ceramide pentasaccharide Gal alpha(1 --> 3)Gal beta(1 --> 4)GlcNAc beta(1 --> 3)Gal beta(1 --> 4)Glc beta(1 --> 0)Cer (1), which binds specifically to human anti-Gal antibody and is involved in the hyperacute rejection response in xenotransplantation from pig to man. The synthesis of 1 and its methyl glycoside 2 is described.     

A review of bycatch reduction in demersal fish trawls

Otter trawling for fish is one of the world’s most productive yet problematic fishing methods due to its bycatch and discards; issues that have been mitigated in some fisheries by developing more selective trawls. This paper systematically reviews efforts published in international peer-reviewed papers over the past 30 years to identify beneficial (and limiting) factors and propose a way forward in this field. In total, 203 papers were assessed, encompassing many of the world’s fishing regions, and involving?>?147 species, although 74% of efforts occurred in Europe mainly focussing on haddock (Melanogrammus aeglefinus) (64 papers) and cod (Gadus morhua) (59 papers). Common, simple modifications have involved increasing lateral-mesh openings to match the morphology of unwanted catches via larger diamond-shaped mesh, or simply turning meshes 45° or 90°, either throughout codends or as strategic windows in the posterior trawl. In some fisheries, more complex grids have improved size or species selection. Fewer attempts have been made to modify the anterior trawl, but varying sweep/bridle lengths, horizontal separator panels and longer headropes have realized benefits depending on species-specific behavioural responses. While the utility of many modifications is indisputable, experimental designs (mostly involving covers, but also alternate hauls and paired comparisons) have, in many cases, suffered low replication and/or confounding variables. These deficits may have compromised some results and contributed to repeated efforts in particular fisheries. We conclude that rigorous empirical assessments, initially focusing on the posterior trawl, but eventually encompassing anterior changes, combined with straightforward interpretation of results for stakeholders, are as important as the simplicity and reliability of modifications. Finally, by assessing the utility, applicability, advantages and disadvantages of the modifications developed, we provide a framework which could be followed in future work to reduce bycatch in these fisheries.

     

Experiments on the resistance of fish to rapid increase in hydrostatic pressure

In a few hydro-electric pumping stations in the southern Black Forest it has been found that fish occurring in the high lying reservoirs could only arrive there from the river below after an upward transport through the pumping system. As there is a height difference of 400 m to overcome the fish must withstand a sudden pressure change of 40 atm. To test whether this is actually possible various species of fish were subjected suddenly to a pressure of 50 atm which was then reduced to 1 atm over a period of 10 min.
No mortality occurred. Although the pressure shock symptoms exhibited by the different species of fish were variable, all appeared to be perfectly normal 2 h after the experiment.     

A review of antimicrobial resistance in Canada

Antimicrobial resistance is a global concern. Over the past 10 years, considerable efforts and resources have been expended to detect, monitor, and understand at the basic level the many different facets of emerging and increasing resistance. This review summarizes our current understanding of bacterial antimicrobial resistance issues in Canada with particular emphasis given to the Enterobacteriaceae, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus, Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, and Streptococcus pyogenes. In addition, future concerns and programs for ongoing surveillance are discussed.     

Understanding behavioral responses of fish to pheromones in natural freshwater environments

There is an abundance of experimental studies and reviews that describe odorant-mediated behaviors of fish in laboratory microcosms, but research in natural field conditions has received considerably less attention. Fish pheromone studies in laboratory settings can be highly productive and allow for controlled experimental designs; however, laboratory tanks and flumes often cannot replicate all the physical, physiological and social contexts associated with natural environments. Field experiments can be a critical step in affirming and enhancing understanding of laboratory discoveries and often implicate the ecological significance of pheromones employed by fishes. When findings from laboratory experiments have been further tested in field environments, often different and sometimes contradictory conclusions are found. Examples include studies of sea lamprey (Petromyzon marinus) mating pheromones and fish alarm substances. Here, we review field research conducted on fish pheromones and alarm substances, highlighting the following topics: (1) contradictory results obtained in laboratory and field experiments, (2) how environmental context and physiological status influences behavior, (3) challenges and constraints of aquatic field research and (4) innovative techniques and experimental designs that advance understanding of fish chemical ecology through field research.     

Heterosis in resistance to Ichthyophthirius multifiliis infections in poeciliid fish

Resistance to experimental infections of Ichthyophthirius multifiliis was investigated in the poeciliid fish Xiphophorus maculatus, X. variatus and their two reciprocal hybrids. A third species, the goodeid Ameca splendens , was infected for comparative purposes. Infection data were analysed using a generalized linear interactive modelling package (GLIM). Infection levels were not significantly influenced by the sex of the fish, temperature, or speciestemperature interactions, but body area and time of infection did affect susceptibility. After accounting for variation due to these factors, it was shown that the two reciprocal hybrids of X. maculatus and X. variatus had significantly lower infection levels than either parental stock. Heterosis, H , was calculated from both raw data (16.2%) and from modelled values (31.3%) after removal of environmental factors. This confirms the existence of genetic factors determining resistance to /. multifiliis infection and has shown that gains in resistance can be made through hybridization.