Mapping of quantitative trait loci controlling tick [Riphicephalus (Boophilus) microplus] resistance on bovine chromosomes 5, 7 and 14

Differences in domestication and selection processes have contributed to considerable phenotypic and genotypic differences between Bos taurus and Bos indicus cattle breeds. Of particular interest in tropical and subtropical production environments are those genetic differences between subspecies that underlie the phenotypic extremes in tolerance and susceptibility to parasite infection. In general, B. taurus cattle are more susceptible to ectoparasites than B. indicus cattle in tropical environments, and much of this difference is under genetic control. To identify genomic regions involved in tick resistance, we developed a B. taurus x B. indicus F(2) experimental population to map quantitative trait loci (QTL) for resistance to the Riphicephalus (Boophilus) microplus tick. About 300 individuals were measured for parasite load in two seasons (rainy and dry) and genotyped for 23 microsatellite markers covering chromosomes 5, 7 and 14. We mapped a suggestive chromosome-wide QTL for tick load in the rainy season (P < 0.05) on chromosome 5. For the dry season, suggestive (P < 0.10) chromosome-wide QTL were mapped on chromosomes 7 and 14. The additive effect of the QTL on chromosome 14 corresponds to 3.18% of the total observed phenotypic variance. Our QTL-mapping study has identified different genomic regions controlling tick resistance; these QTL were dependent upon the season in which the ticks were counted, suggesting that the QTL in question may depend on environmental factors.     

The role of Tyr605 and Ala607 of thimet oligopeptidase and Tyr606 and Gly608 of neurolysin in substrate hydrolysis and inhibitor binding

The physicochemical properties of TOP (thimet oligopeptidase) and NEL (neurolysin) and their hydrolytic activities towards the FRET (fluorescence resonance energy transfer) peptide series Abz-GFSXFRQ-EDDnp [where Abz is o-aminobenzoyl; X=Ala, Ile, Leu, Phe, Tyr, Trp, Ser, Gln, Glu, His, Arg or Pro; and EDDnp is N-(2,4-dinitrophenyl)-ethylenediamine] were compared with those of site-mutated analogues. Mutations at Tyr605 and Ala607 in TOP and at Tyr606 and Gly608 in NEL did not affect the overall folding of the two peptidases, as indicated by their thermal stability, CD analysis and the pH-dependence of the intrinsic fluorescence of the protein. The kinetic parameters for the hydrolysis of substrates with systematic variations at position P1 showed that Tyr605 and Tyr606 of TOP and NEL respectively, played a role in subsite S1. Ala607 of TOP and Gly608 of NEL contributed to the flexibility of the loops formed by residues 600-612 (GHLAGGYDGQYYG; one-letter amino acid codes used) in NEL and 599-611 (GHLAGGYDAQYYG; one-letter amino acid codes used) in TOP contributing to the distinct substrate specificities, particularly with an isoleucine residue at P1. TOP Y605A was inhibited less efficiently by JA-2 {N-[1-(R,S)-carboxy-3-phenylpropyl]Ala-Aib-Tyr-p-aminobenzoate}, which suggested that the aromatic ring of Tyr605 was an important anchor for its interaction with wild-type TOP. The hydroxy groups of Tyr605 and Tyr606 did not contribute to the pH-activity profiles, since the pKs obtained in the assays of mutants TOP Y605F and NEL Y606F were similar to those of wild-type peptidases. However, the pH-kcat/Km dependence curve of TOP Y605A differed from that of wild-type TOP and from TOP Y606F. These results provide insights into the residues involved in the substrate specificities of TOP and NEL and how they select cytosolic peptides for hydrolysis.     

Heritability and genetic correlations of metabolic disease-related phenotypes in Mexico: preliminary report from the GEMM Family Study

Cardiovascular disease (CVD) is a major cause of mortality in the Republic of Mexico, and metabolic syndrome, a complex of CVD risk factors, is increasingly prevalent. To date, however, there have been few studies of the genetic epidemiology of metabolic syndrome in Mexico. As a first step in implementing the GEMM Family Study, a large, multicenter collaborative study, we recruited 375 individuals in 21 extended families, without ascertainment on disease, at 9 medical institutions across Mexico. Participants were measured for anthropometric (stature, weight, waist circumference) and hemodynamic (blood pressure, heart rate) phenotypes; glucose, cholesterol, and triglyceride levels were measured in fasting blood. Variance components-based quantitative genetic analyses were performed using SOLAR. All phenotypes except diastolic blood pressure were significantly heritable. Consistent with the definition of metabolic syndrome, many phenotypes exhibited significant environmental correlation, and significant genetic correlations were found between measures of adiposity and fasting glucose and fasting triglyceride levels. These preliminary data represent the first heritability estimates for many of these phenotypes in the Republic of Mexico and indicate that this study design offers excellent power for future gene discovery relative to metabolic disease.     

Absence of Classical Heat Shock Response in the Citrus Pathogen <Emphasis Type="Italic">Xylella fastidiosa</Emphasis>

The fastidious bacterium Xylella fastidiosa is associated with important crop diseases worldwide. We have recently shown that X. fastidiosa is a peculiar organism having unusually low values of gene codon bias throughout its genome and, unexpectedly, in the group of the most abundant proteins. Here, we hypothesized that the lack of codon usage optimization in X. fastidiosa would incapacitate this organism to undergo quick and massive changes in protein expression as occurs in a classical stress response. Proteomic analysis of the response to heat stress in X. fastidiosa revealed that no changes in protein expression can be detected. Moreover, stress-inducible proteins identified in the closely related citrus pathogen Xanthomonas axonopodis pv citri were found to be constitutively expressed in X. fastidiosa. These proteins have extremely high codon bias values in the X. citri and other well-studied organisms, but low values in X. fastidiosa. Because biased codon usage is well known to correlate to the rate of protein synthesis, we speculate that the peculiar codon bias distribution in X. fastidiosa is related to the absence of a classical stress response, and, probably, alternative strategies for survival of X. fastidiosa under stressfull conditions.     

A chitin-like component in Aedes aegypti eggshells, eggs and ovaries

An insoluble white substance was prepared from extracts of eggshells of Aedes aegypti, the yellow fever mosquito and dengue vector. Its infrared and proton NMR spectra were similar to that of standard commercial chitin. This putative chitin-like material, also obtained from ovaries, newly laid and dark eggs, was hydrolyzed in acid and a major product was identified by HPLC to be glucosamine. The eggshell acid hydrolysate was also analyzed by ESI-MS and an ion identical to a glucosamine monoprotonated species was detected. The presence of chitin was also analyzed during different developmental stages of the ovary using a fluorescent microscopy technique and probes specific for chitin. The results showed that a chitin-like material accumulates in oocytes during oogenesis. Streptomyces griseus chitinase pre-treatment of oocytes greatly reduced the chitin-derived fluorescence. Chitinase activity was detected in newborn larvae and eggs prior to hatching. Feeding experiments indicated that the chitin synthesis inhibitor lufenuron inhibited chitin synthesis, either when mosquitoes were allowed to feed directly on lufenuron-treated chickens or when an artificial feeding system was used. Lufenuron inhibited egg hatch, larval development and reduced mosquito viability. These data demonstrate for the first time that (1) a chitin-like material is present in A. aegypti eggs, ovaries and eggshells; (2) a chitin synthesis inhibitor can be used to inhibit mosquito oogenesis; and (3) chitin synthesis inhibitors have potential for controlling mosquito populations.     

Insecticidal action of Bauhinia monandra leaf lectin (BmoLL) against Anagasta kuehniella (Lepidoptera: Pyralidae), Zabrotes subfasciatus and Callosobruchus maculatus (Coleoptera: Bruchidae)

Bruchid beetle larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil (Callosobruchus maculatus) and the Mexican bean weevil (Zabrotes subfasciatus), are pests that damage stored seeds. The Mediterranean flour moth (Anagasta kuehniella) is of major economic importance as a flour and grain feeder; it is often a severe pest in flour mills. Plant lectins have been implicated as antibiosis factors against insects. Bauhinia monandra leaf lectin (BmoLL) was tested for anti-insect activity against C. maculatus, Z. subfasciatus and A. kuehniella larvae. BmoLL produced ca. 50% mortality to Z. subfaciatus and C. maculatus when incorporated into an artificial diet at a level of 0.5% and 0.3% (w/w), respectively. BmooLL up to 1% did not significantly decrease the survival of A. kuehniella larvae, but produced a decrease of 40% in weight. Affinity chromatography showed that BmoLL bound to midgut proteins of the insect C. maculatus. 33 kDa subunit BmoLL was not digested by midgut preparations of these bruchids. BmoLL-fed C. maculatus larvae increased the digestion of potato starch by 25% compared with the control. The transformation of the genes coding for this lectin could be useful in the development of insect resistance in important agricultural crops.     

Development of genetic maps of the citrus varieties ‘Murcott’ tangor and ‘Pêra’ sweet orange by using fluorescent AFLP markers

The progeny of 87 BC(1) hybrids of 'Murcott' tangor and 'Pera' sweet orange, genotyped with fluorescent amplified fragment length polymorphism (fAFLP) markers, was used for the construction of genetic maps for both citrus varieties. Mapping strategies, considering the progeny as a result of backcrossing and cross-pollination, were exploited in Mapmaker 2.0 (LOD score >or= 3.0 and or= 3.0 and theta 相似文献   

Lack of effect of dopaminergic antagonists in a rodent model of peritoneal sepsis

Central nervous system dopaminergic mechanisms have been implicated in the cytokine response to stress and sepsis. We here describe the effects of haloperidol or clozapine in the treatment of sepsis induced by cecal ligation and puncture. Male Wistar rats were subjected to the CLP procedure were treated with haloperidol or clozapine and plasma cytokines, myeloperoxidase activity, markers of organ injury and survival was analyzed. The addition of haloperidol or clozapine to basic support did not diminished hepatic, renal, pancreatic or muscular damage observed after sepsis. Neither haloperidol, nor clozapine, modulates pro and antiinflammatory cytokines after sepsis induction. In addition, haloperidol treatment did not diminished myeloperoxidase activity in the kidney, lung or liver, or altered BALF markers of lung damage or inflammatory infiltration. Our data did not support a role of haloperidol or clozapine as an immunomodulator agent in the treatment of sepsis in an animal model of peritonitis.     

Squamate richness in the Brazilian Cerrado and its environmental–climatic associations

We investigate patterns of species richness of squamates (lizards, snakes, and amphisbaenians) in the Brazilian Cerrado, identifying areas of particularly high richness, and testing predictions of large‐scale richness hypotheses by analysing the relationship between species richness and environmental climatic variables. We used point localities from museum collections to produce maps of the predicted distributions for 237 Cerrado squamate species, using niche‐modelling techniques. We superimposed distributions of all species on a composite map, depicting richness across the ecosystem. Then, we performed a multiple regression analysis using eigenvector‐based spatial filtering (Principal Coordinate of Neighbour Matrices) to assess environmental–climatic variables that are best predictors of species richness. We found that the environmental–climatic and spatial filters multiple regression model explained 78% of the variation in Cerrado squamate richness (r² = 0.78; F = 32.66; P < 0.01). Best predictors of species richness were: annual precipitation, precipitation seasonality, altitude, net primary productivity, and precipitation during the driest quarter. A model selection approach revealed that several mechanisms related to the different diversity hypothesis might work together to explain richness variation in the Cerrado. Areas of higher species richness in Cerrado were located mainly in the south‐west, north, extreme east, and scattered areas in the north‐west portions of the biome. Partitioning of energy among species, habitat differentiation, and tolerance to variable environments may be the primary ecological factors determining variation in squamate richness across the Cerrado. High richness areas in northern Cerrado, predicted by our models, are still poorly sampled, and biological surveys are warranted in that region. The south‐western region of the Cerrado exhibits high species richness and is also undergoing high levels of deforestation. Therefore, maintenance of existing reserves, establishment of ecological corridors among reserves, and creation of new reserves are urgently needed to ensure conservation of species in these areas.     

Shifts in the psychophysical function in rats

The primary goal was to compare results from a free-operant procedure with pigeons [Machado, A., Guilhardi, P., 2000. Shifts in the psychometric function and their implications for models of timing. J. Exp. Anal. Behav. 74, 25-54, Experiment 2] with new results obtained with rats. The secondary goal was to compare the results of both experiments with dependent variables that were not used in the original publication. As in the original study with pigeons, rats were trained on a two-alternative free-operant psychophysical procedure in which left lever press responses were reinforced during the first and second quarters of a 60-s trial, and right lever press responses were reinforced during the third and fourth quarters of the trial. The quarters were reinforced according to four independent variable interval (VI) schedules of reinforcement. The VI duration was manipulated in each quarter, and shifts in the psychophysical functions that relate response rate with time since trial onset were measured. The results obtained with rats were consistent with those previously obtained with pigeons. In addition, results not originally reported were also consistent between rats and pigeons, and provided insights into the perception, memory, and decision processes in Scalar Expectancy Theory and Learning-to-Time Theory.