Population Genetic Structure of Astyanax scabripinnis (Teleostei, Characidae) from an Urban Stream

Despite the great anthropogenic interference on urban streams, information is still scarce about the genetic variability and structure of native fish populations inhabiting such streams. In the present study, random amplified polymorphic DNA (RAPD) markers were used to analyze genetic variability and structure of populations assigned to the Neotropical fish species Astyanax scabripinnis from an urban stream located in Londrina, Paraná State, southern Brazil. Thirty individuals of this species were collected from three sites throughout the upper Cambé stream. A total of 10 primers amplified 159 loci, of which 128 (80.5%) were polymorphic. Each of the three populations showed very similar proportions of polymorphic loci, which ranged from 63.5 to 64.8%. Unbiased genetic distances varied from 0.0612 to 0.0646. Theta_p-test values indicated moderate to high genetic differentiation among individuals from different localities. The number of migrants varied from 1.34 to 1.46, suggesting a low gene flow between populations. The genetic similarity among all individuals studied ranged from 0.424 to 0.848. The results suggest that populations of A. scabripinnis in Cambé stream are undergoing genetic differentiation.     

ADP-ribosylation of dinitrogenase reductase in Azospirillum brasilense is regulated by AmtB-dependent membrane sequestration of DraG

Nitrogen fixation in some diazotrophic bacteria is regulated by mono-ADP-ribosylation of dinitrogenase reductase (NifH) that occurs in response to addition of ammonium to the extracellular medium. This process is mediated by dinitrogenase reductase ADP-ribosyltransferase (DraT) and reversed by dinitrogenase reductase glycohydrolase (DraG), but the means by which the activities of these enzymes are regulated are unknown. We have investigated the role of the P(II) proteins (GlnB and GlnZ), the ammonia channel protein AmtB and the cellular localization of DraG in the regulation of the NifH-modification process in Azospirillum brasilense. GlnB, GlnZ and DraG were all membrane-associated after an ammonium shock, and both this membrane sequestration and ADP-ribosylation of NifH were defective in an amtB mutant. We now propose a model in which membrane association of DraG after an ammonium shock creates a physical separation from its cytoplasmic substrate NifH thereby inhibiting ADP-ribosyl-removal. Our observations identify a novel role for an ammonia channel (Amt) protein in the regulation of bacterial nitrogen metabolism by mediating membrane sequestration of a protein other than a P(II) family member. They also suggest a model for control of ADP-ribosylation that is likely to be applicable to all diazotrophs that exhibit such post-translational regulation of nitrogenase.     

CFD simulation of an internal spin-filter: evidence of lateral migration and exchange flow through the mesh

In the present work Computational Fluid Dynamics (CFD) was used to study the flow field and particle dynamics in an internal spin-filter (SF) bioreactor system. Evidence of a radial exchange flow through the filter mesh was detected, with a magnitude up to 130-fold higher than the perfusion flow, thus significantly contributing to radial drag. The exchange flow magnitude was significantly influenced by the filter rotation rate, but not by the perfusion flow, within the ranges evaluated. Previous reports had only given indirect evidences of this exchange flow phenomenon in spin-filters, but the current simulations were able to quantify and explain it. Flow pattern inside the spin-filter bioreactor resembled a typical Taylor-Couette flow, with vortices being formed in the annular gap and eventually penetrating the internal volume of the filter, thus being the probable reason for the significant exchange flow observed. The simulations also showed that cells become depleted in the vicinity of the mesh due to lateral particle migration. Cell concentration near the filter was approximately 50% of the bulk concentration, explaining why cell separation achieved in SFs is not solely due to size exclusion. The results presented indicate the power of CFD techniques to study and better understand spin-filter systems, aiming at the establishment of effective design, operation and scale-up criteria.     

Assessing the environmental profile of orange production in Brazil

Background, aim, and scope

Brazil is the world’s largest orange producing country, with a total planted area of more than 820,000 hectares. The bulk of the oranges produced in Brazil (70%) is processed into frozen concentrated orange juice (FCOJ) by large processing companies. Exports represent around 97% of the total FCOJ produced, making Brazil the largest world producer and exporter of FCOJ. The Brazilian citrus sector accounts for half of the world’s supply of orange juice and for 80% of the juice traded on the international market. The goal of this study is to characterize the Brazilian orange producers in terms of farm size, cultivated varieties, watering system and tillage practices. In addition, the study presents some aspects of the LCI of oranges grown specifically for the production of FCOJ in the two major orange-growing areas in Brazil (the Northern and Southern regions of the State of São Paulo) during reference crop year 2002/03 in order to generate detailed production inventory data and identify the potential environmental impacts of tillage, both of which are key to enable the formulation of sustainability parameters for the production of FCOJ in Brazil.

Methods

This study was performed in compliance with the guidelines and requirements of the ISO 14040 standard series. All information and data considered and evaluated in this study (the use of water, energy, fertilizers, pesticides and soil correctors) were gathered through in-depth questionnaires either filled in directly by the farm manager or completed by the farm manager and sent in by mail. The data cover a total of 367,200 metric tons of oranges produced by 4 million plants in commercial production from a total evaluated area that accounts for 19.5% of the overall production of oranges in the State of São Paulo. The two major orange-producing areas in Brazil located respectively in the Northern and Southern regions of the State of São Paulo were evaluated. Only the inputs and outputs associated with tillage practices and technology were considered in this paper. The environmental aspects of the production of fertilizers and pesticides were not included within the boundaries. The functional unit selected for this study was 1,000 kg of oranges for FCOJ. Farm-specific data have been combined with agricultural production data to construct an orange cultivation model.

Results

The orange varieties for the production of FCOJ evaluated in this study were Pêra, Valência and Natal. The farms investigated had a cultivated area varying from 22 to 7,000 ha, with a plant density ranging from 170 to 500 plants/ha and an average yield of 30,500 kg/ha for mature trees. Depending on the region, the production of 1,000 kg of oranges requires approx. 120 to 4,400 MJ of energy; 0.3 to 36 kg of diesel; 1,100 to 54,500 kg of water for irrigation; 0.3 to 65 kg of fertilizers (NPK); 0.1 to 13.5 kg of pesticides; 8 to 650 kg of soil correctors. The distribution of some inputs across the farms located in the two main Brazilian orange-producing regions is presented, in addition to the total weighted average.

Discussion

In addition to the variations among the regions evaluated, it was generally observed that there were very considerable differences in order of magnitude between the data collected from farms located in the same region. Although the inputs are directly related to the specific characteristics of each farm and the climatic and topographic conditions of its location, this study has identified some farms that are in a good position to reduce the amounts of some inputs and enhance their environmental and economical performance.

Conclusions

Taking into account the aspects evaluated in this study, only 21% of the orange growers showed good performance, i.e., consumption of pesticides, fertilizers and soil correction compounds equal to or lower than the weighted averages, except for “land use”, which was above the average for the majority of these farms. This study provided important results that allow for a better understanding of the agricultural practices involved and the potential environmental impacts of this product.

Recommendation and perspective

The authors would like to suggest that the five best-performing farms average values be set as the maximum allowable level and point of departure for the discussion on the good environmental performance of Brazilian FCOJ. Besides the total inputs, the role of good agricultural practices to achieve good yields and, at the same time, improve the sustainability of orange growing should also be taken into consideration. Future updates of this study will show the evolution of natural resource management as a result of improved land use, new agricultural practices, reduced use of fertilizers and agrochemicals.     

Low and high-dose intradermal infection with Leishmania major and Leishmania amazonensis in C57BL/6 mice

A model of skin infection with Leishmania amazonensis with low doses of parasites is compared to infection with high doses of L. amazonensis and low and high doses of Leishmania major. C57BL/6 mice were infected with 103 or 10(6) parasites in the ear and the outcome of infection was assessed. The appearance of lesions in mice infected with 103 parasites was delayed compared to mice infected with 10(6) Leishmania and parasites were detectable at the infection site before lesions became apparent. Mice infected with L. amazonensis displayed persistent lesions, whereas infection with L. major spontaneously healed in all groups, although lymphocytes persisted at the site of infection after healing. Macrophages persisted only in L. amazonensis-infected mice. High-dose L. amazonensis-infected mice produced lower levels of IFN-γ and TNF than mice infected with L. major. No correlation between the persistence of parasites and IL-10 levels and the production of nitric oxide or urea by macrophages was found. We conclude that infection with low doses of L. amazonensis in the dermis changes the course of infection by delaying the appearance of lesions. However, low-dose infection does not change the outcomes of susceptibility and cytokine production described for subcutaneous infection with high numbers of parasites.     

Echinophilic proteins stomatin, sorcin, and synexin locate outside gangliosideM1 (GM1) patches in the erythrocyte membrane

The detergent (Triton X-100, 4 °C)-resistant membrane (DRM)-associated membrane proteins stomatin, sorcin, and synexin (anexin VII) exposed on the cytoplasmic side of membrane were investigated for their lateral distribution in relation to induced ganglioside_M1 (GM1) raft patches in flat (discocytic) and curved (echinocytic) human erythrocyte membrane. In discocytes, no accumulation of stomatin, sorcin, and synexin in cholera toxin subunit B (CTB) plus anti-CTB-induced GM1 patches was detected by fluorescence microscopy. In echinocytes, stomatin, sorcin, and synexin showed a similar curvature-dependent lateral distribution as GM1 patches by accumulating to spiculae induced by ionophore A23187 plus calcium. Stomatin was partly and synexin and sorcin were fully recruited to the spiculae. However, the DRM-associated proteins only partially co-localized with GM1 and were frequently distributed into different spiculae than GM1. The study indicates that stomatin, sorcin, and synexin are echinophilic membrane components that mainly locate outside GM1 rafts in the human erythrocyte membrane. Echinophilicity is suggested to contribute to the DRM association of a membrane component in general.     

Sensitive quantification of chosen drugs by reversed-phase chromatography with electrochemical detection at a glassy carbon electrode

Reversed-phase-high-performance liquid chromatographic method with electrochemical detection has proven to be a highly sensitive and selective method for determination of trace components in complex biological samples, and the electrochemical detector becomes an important alternative tool to ultraviolet and fluorescence detectors. A rapid and sensitive method for the accurate determination of metoclopramide, hydrochlorothiazide, imipramine and diclofenac in serum or plasma samples is described. The method is based on liquid-liquid extraction. The compounds were separated on C-18 column as stationary phase with a different binary mixture as mobile phase. Proposed method was validated with respect to specificity, linearity range, limit of detection and quantitation, precision, accuracy and successfully applied in a pharmacokinetic studies.     

Genetic similarity among male bees of Euglossa truncata Rebêlo & Moure (Hymenoptera: Apidae) revealed by RAPD markers

The genetic RAPD (random amplified polymorphic DNA) markers have been used successfully in taxonomical studies of several groups of organisms. In the present study these molecular markers were used to analyze the genetic similarity among eighteen males of Euglossa truncata Rebêlo & Moure exhibiting variations in two morphological characters (colour of the antennal scape and metaepisternal hairs) which are frequently used to identify this species of euglossine bee. The twelve primers used in the RAPD analysis amplified 127 loci, of which 40 (31.5%) were polymorphic, showing some variation among the individuals. The coefficients of genetic similarity among the individuals ranged from 0.79 to 0.95, indicating a rather high genetic similarity among the 18 male bees studied. No RAPD band was specific to any morphological character analyzed. The results indicate that all bees analyzed belong to the same species. The high genetic similarity among the eighteen euglossine males studied indicates that the variations observed in the morphological characters are not in disagreement with the identification of this species of Euglossina and these characters can vary among males of E. truncata.     

Endovesicle formation and membrane perturbation induced by polyoxyethyleneglycolalkylethers in human erythrocytes

Polyoxyethyleneglycolalkylether (CmEn, m=12, n=8) can induce a large torocyte-like endovesicle in human erythrocytes. The present study aimed to examine how variations in the molecular structure of CmEn (m=10,12,14,16,18; n=1-10,23) affect the occurrence of torocyte endovesicles. Our results show that torocytes occur most frequently when m=12,14 and n=8,9. At this molecular configuration the detergents induce inward membrane bending (stomatocytic S1-S2 shapes) resulting in the formation of a large membrane invagination. These detergents have a strong membrane perturbing, i.e., haemolytic, effect. Theoretical calculations indicate that a torocyte-shaped inside-out membrane vesicle can be created from a large membrane invagination due to the impact of laterally mobile anisotropic membrane inclusions. Such inclusions may be detergent-membrane component complexes or unanchored integral membrane proteins. It is shown that a nonhomogeneous lateral distribution of anisotropic membrane inclusions may stabilise the torocyte endovesicle shape, characterised by having opposite membranes in the thin central region of the vesicles separated by a certain distance. Tubular, conical or inverted conical isotropic inclusions cannot do so.