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The present study provides a species list of freshwater mussels from Catalão, the meeting of the Solimõesand Negro rivers, in state of Amazonas, northern Brazil. Expeditions to collect molluscs were carried out between 2004and 2006, during high and low water seasons. Three hundred and thirty-one bivalve shells, 25 valves, and 57 livespecimens of four families and 10 species were identified. A single exotic species, Corbicula fluminea, represented overhalf the collected shells. All bivalve shells were photographed and registered at the mollusc collection of the InstitutoNacional de Pesquisas da Amazônia (INPA), Manaus.

In this work, we have measured, by means of optical tweezers, forces acting on depletion-induced DNA condensates due to the presence of the DNA-like charged protein bovine serum albumin (BSA). The stretching and unfolding measurements performed on the semi-flexible DNA chain reveal (1) the softening of the uncondensed DNA contour length and (2) a mechanical behavior strikingly different from those previously observed: the force-extension curves of BSA-induced DNA condensates lack the "saw-tooth" pattern and applied external forces as high as ≈80 pN are unable to fully unfold the condensed DNA contour length. This last mechanical experimental finding is in agreement with force-induced "unpacking" detailed Langevin dynamics simulations recently performed by Cortini et al. on model rod-like shaped condensates. Furthermore, a simple thermodynamics analysis of the unfolding process has enabled us to estimate the free energy involved in the DNA condensation: the estimated depletion-induced interactions vary linearly with both the condensed DNA contour length and the BSA concentration, in agreement with the analytical and numerical analysis performed on model DNA condensates. We hope that future additional experiments can decide whether the rod-like morphology is the actual one we are dealing with (e.g. pulling experiments coupled with super-resolution fluorescence microscopy). [ABSTRACT FROM AUTHOR]

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Plants not only respond to herbivorous damage but adjust their defense system after egg deposition by pest insects. Thereby, parasitoids use oviposition-induced plant volatiles to locate their hosts. We investigated the olfactory behavioral responses of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) to volatile blends emitted by maize (Zea mays L.) with singular and stacked events after oviposition by Spodoptera frugiperda Smith, 1797 (Hymenoptera: Trichogrammatidae) moths. Additionally, we examined possible variations in gene expression and on oviposition-induced volatiles. We used a Y-tube olfactometer to test for the wasp responses to volatiles released by maize plants oviposited by S. frugiperda and not-oviposited plants. Using the real-time PCR technique (qRT-PCR), we analyzed the expression of lipoxygenase and three terpene synthases genes, which are enzymes involved in the synthesis of volatile compounds that attract parasitoids of S. frugiperda. Olfactometer tests showed that T. pretiosum is strongly attracted by volatiles from transgenic maize emitted by S. frugiperda oviposition (VTPRO 3, more than 75% individuals were attracted). The relative expression of genes TPS10, LOX e STC was higher in transgenic hybrids than in the conventional (isogenic line) hybrids. The GC-MS analysis revealed that some volatile compounds are released exclusively by transgenic maize. This study provides evidence that transgenic hybrids enhanced chemical cues under oviposition-induction and helped to increase T. pretiosum efficiency in S. frugiperda control. This finding shows that among the evaluated hybrids, genetically modified hybrids can improve the biological control programs, since they potentialize the egg parasitoid foraging, integrating pest management. [ABSTRACT FROM AUTHOR]

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. Our results show that the persistence length of the DNA-drug complexes increases strongly as the drug concentration increases up to some critical value. Above this critical value, the persistence length decreases abruptly and remains approximately constant for larger drug concentrations, at least in the concentration range used in our experiments. Measured intercalators critical concentrations for the persistence length transition coincide with the reported values for the helix-coil transition of DNA-drug complexes obtained from sedimentation experiments. The contour length of the molecules increases monotonically and saturates as the drug concentration increases. The neighbor exclusion model fits to our results for the total drug concentration as a function of the relative increase of the contour length. [ABSTRACT FROM AUTHOR]

By attaching one end of a single λ-DNA molecule to a microscope coverslip and the other end to a polystyrene microsphere trapped by an optical tweezers, we can study the entropic elasticity of the λ-DNA by measuring force versus extension as we stretch the molecule. This powerful method permits single molecule studies. We are particulary interested in the effects of the photosensitive drug psoralen on the elasticity of the DNA molecule. We have illuminated the sample with different light sources, studying how the different wavelengths affect the psoralen-DNA linkage. To do this, we measure the persistence length of individual DNA-psoralen complexes. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to assess anthropogenic impact of surrounding population in the Private Reserve of Natural Heritage at Pantanal, the world's largest freshwater wetland ecosystem located in the centre of South America. Viral aetiological agents of acute gastroenteritis as rotavirus A (RVA), noroviruses, human adenoviruses, klassevirus and of hepatitis, as hepatitis A virus, were investigated in different aquatic matrices. Annual collection campaigns were carried out from 2009 to 2012, alternating dry and rainy seasons. Viral particles present in the samples were concentrated by the adsorption–elution method, with negatively charged membranes, and detected by qualitative and quantitative PCR. From a total of 43 samples at least one virus was detected in 65% (28) of them. Viruses were detected in all matrices with concentrations ranging from 2 × 102 to 8·3 × 104 genome copies per litre. A significant higher RVA frequency was observed in the dry season. Our data revealing dissemination of human enteric viruses in water matrices both inside and outside the reserve could be useful to trace faecal contamination in the environment and to minimize the risk of infection by exposure of susceptible individuals. Significance and Impact of the Study: This study is part of a collaborative project designed to investigate the environmental and health conditions of the Private Reserve of Natural Heritage at Pantanal, the largest seasonally flooded wetland in the world. The project aimed to promote health and quality of human and wildlife extending technical‐scientific knowledge about pathogens present in the region. By assessing the occurrence of human enteric viruses in different water matrices we demonstrated the anthropogenic impact of surrounding population and pointed out the potential risk of infection by exposure of susceptible individuals. [ABSTRACT FROM AUTHOR]

Maturity‐Onset Diabetes of the Young (MODY) type 4 or PDX1 ‐MODY is a rare form of monogenic diabetes caused by heterozygous variants in PDX1 . Pancreatic developmental anomalies related to PDX1 are reported only in neonatal diabetes cases. Here, we describe dorsal pancreatic agenesis in 2 patients with PDX1 ‐MODY. The proband presented with diabetes since 14 years of age and maintained regular glycemic control with low doses of basal insulin and detectable C‐peptide levels after 38 years with diabetes. A diagnosis of MODY was suspected. Targeted next‐generation sequencing identified a heterozygous variant in PDX1 : c.188delC/p.Pro63Argfs*60. Computed tomography revealed caudal pancreatic agenesis. Low fecal elastase indicated exocrine insufficiency. His son had impaired glucose tolerance, presented similar pancreatic agenesis, and harbored the same allelic variant. The unusual presentation in this Brazilian family enabled expansion upon a rare disease phenotype, demonstrating the possibility of detecting pancreatic malformation even in cases of PDX1 ‐related diabetes diagnosed after the first year of life. This finding can improve the management of MODY4 patients, leading to precocious investigation of pancreatic dysgenesis and exocrine dysfunction. [ABSTRACT FROM AUTHOR]

In this work, we have studied the interaction between the anticancer drug doxorubicin (doxo) and condensed DNA, using optical tweezers. To perform this task, we use the protein bovine serum albumin (BSA) in the working buffer to mimic two key conditions present in the real intracellular environment: the condensed state of the DNA and the abundant presence of charged macromolecules in the surrounding medium. In particular, we have found that, when doxo is previously intercalated in disperse DNA, the drug hinders the DNA condensation process upon the addition of BSA in the buffer. On the other hand, when bare DNA is firstly condensed by BSA, doxo is capable to intercalate and to unfold the DNA condensates at relatively high concentrations. In addition, a specific interaction between BSA and doxo was verified, which significantly changes the chemical equilibrium of the DNA-doxo interaction. Finally, the presence of BSA in the buffer stabilizes the double-helix structure of the DNA-doxo complexes, preventing partial DNA denaturation induced by the stretching forces. [ABSTRACT FROM AUTHOR]

In this work, we use force spectroscopy to investigate the interaction between the DAPI fluorescent dye and the λ-DNA molecule under high (174 mM) and low (34 mM) ionic strengths. Firstly, we have measured the changes on the mechanical properties (persistence and contour lengths) of the DNA-DAPI complexes as a function of the dye concentration in the sample. Then, we use recently developed models in order to connect the behavior of both mechanical properties to the physical chemistry of the interaction. Such analysis has allowed us to identify and to decouple two main binding modes, determining the relevant physicochemical (binding) parameters for each of these modes: minor groove binding, which saturates at very low DAPI concentrations ( [ABSTRACT FROM AUTHOR]

We have investigated the interaction of the DNA molecule with the anticancer drug doxorubicin (doxo) by using three different experimental techniques: single molecule stretching, single molecule imaging, and dynamic light scattering. Such techniques allowed us to get new insights on the mechanical behavior of the DNA-doxo complexes as well as on the physical chemistry of the interaction. First, the contour length data obtained from single molecule stretching were used to extract the physicochemical parameters of the DNA-doxo interaction under different buffer conditions. This analysis has proven that the physical chemistry of such interaction can be modulated by changing the ionic strength of the surrounding buffer. In particular we have found that at low ionc strengths doxo interacts with DNA by simple intercalation (no aggregation) and/or by forming bound dimers. For high ionic strengths, otherwise, doxo-doxo self-association is enhanced, giving rise to the formation of bound doxo aggregates composed by 3 to 4 molecules along the double-helix. On the other hand, the results obtained for the persistence length of the DNA-doxo complexes is strongly force-dependent, presenting different behaviors when measured with stretching or non-stretching techniques. [ABSTRACT FROM AUTHOR]

ABSTRACT In this work we have investigated the role of high molecular weight poly(ethylene-glycol) 8000 (PEG 8000) in modulating the interactions of the DNA molecule with two hydrophobic compounds: Ethidium Bromide (EtBr) and GelRed (GR). Both compounds are DNA intercalators and are used here to mimic the behavior of more complex DNA ligands such as chemotherapeutic drugs and proteins whose domains intercalate DNA. By means of single-molecule stretching experiments, we have been able to show that PEG 8000 strongly shifts the binding equilibrium between the intercalators and the DNA even at very low concentrations (1% in mass). Additionally, microcalorimetry experiments were performed to estimate the strength of the interaction between PEG and the DNA ligands. Our results suggest that PEG, depending on the system under study, may act as an 'inert polymer' with no enthalpic contribution in some processes but, on the other hand, it may as well be an active (non-neutral) osmolyte in the context of modulating the activity of the reactants and products involved in DNA-ligand interactions. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 227-233, 2016. [ABSTRACT FROM AUTHOR]

Inthis work we have characterized the effects of the intercalatorethidium bromide (EtBr) on the DNA condensation process by using forcespectroscopy and gel electrophoresis. We have tested two condensingagents: spermine (spm4+), a tetravalent cationic aminewhich promotes cation-induced DNA condensation, and poly(ethyleneglycol) (PEG), a neutral polymer which promotes DNA ψ-condensation.Two different types of experiments were performed. In the first type,bare DNA molecules disperse in solution are first treated with EtBrfor intercalation, and then the condensing agent is added to the samplewith the purpose of verifying the effects of the intercalator in hinderingDNA condensation. In the second experiment type, the bare DNA moleculesare first condensed, and then the intercalator is added to the samplein order to verify its influence on the previously condensed DNA.The results obtained with the two different experimental techniquesused agree very well, indicating that previously intercalated EtBrcan hinder both cation-induced and ψ-condensation, being moreefficient in the first case. On the other hand, EtBr has little effecton the previously formed cation-induced condensates, but is efficientin unfolding the ψ-condensates. [ABSTRACT FROM AUTHOR]

We have studied the interaction between the anticancer drug Actinomycin D (ActD) and the DNA molecule by performing single molecule stretching experiments and atomic force microscopy (AFM) imaging. From the stretching experiments, we determine how the mechanical properties of the DNA–ActD complexes vary as a function of drug concentration, for a fixed DNA concentration. We have found that the persistence lengths of the complexes formed behave non-monotonically: at low concentrations of ActD they are more flexible than the bare DNA molecule and become stiffer at higher concentrations. On the other hand, the contour length increases monotonically as a function of ActD concentration. Using a two-sites quenched disorder statistical model recently developed by us, we were able to extract chemical parameters such as the intrinsic binding constant and the degree of cooperativity from these pure mechanical measurements, thus performing a robust characterization of the interaction. The AFM images, otherwise, were used to measure the bending angle size distribution that ActD introduces on the double-helix structure and the average number of bendings per DNA molecule as a function of drug concentration, two quantities that cannot be determined from the stretching experiments. [ABSTRACT FROM AUTHOR]

A theoretical treatment of optical tweezers is presented at a level suitable for undergraduates. We explore the Rayleigh and the geometrical optics regimes with an emphasis on the latter. We discuss a model for the geometrical optics regime, including spherical aberration effects, and show that the model can easily be implemented numerically. A comparison of the model with experimental data yields excellent agreement between theory and experiment. We also briefly discuss a theory of optical tweezers valid for microspheres of any size. [ABSTRACT FROM AUTHOR]

We discuss measurements of the laser power at the focus of high numerical aperture objectives used in optical microscopy and optical tweezers. For a given power, the focused incident laser beam heats a small mercury bead that jumps when it reaches the boiling temperature of water, the medium used in the experiments. From the size of the mercury beads, the heat conductivities of water and glass-slide, and the absorption coefficient of mercury for the laser wavelength used, the incident power can be obtained using the solution of the associated heat problem. This problem is mapped onto the problem of a charged conducting sphere embedded in a semi-infinite medium of dielectric constant ϵ1, separated from another semi-infinite medium of dielectric constant ϵ2. [ABSTRACT FROM AUTHOR]