Biogeography of Glandulocaudinae (Teleostei : Characiformes : Characidae) revisited: phylogenetic patterns, historical geology and genetic connectivity

The biogeography of the Glandulocaudinae ( former Glandulocaudini) is reviewed. The major pattern of diversification presented by this group of freshwater fishes can be clearly associated to the main aspects of the tectonic evolution of the southern portion of the Cis-Andean South American Platform. The phylogenetic relationships within the group suggest that the clade represented by Lophiobrycon is the sister-group of the more derived clade represented by the genus Glandulocauda and Mimagoniates. Lophiobrycon and Glandulocauda occur in areas of the ancient crystalline shield of southeastern Brazil and their present allopatric distribution is probably due to relict survival and tectonic vicariant events. Populations of Glandulocauda melanogenys are found in contiguous drainages in presently isolated upper parts of the Tiete, Guaratuba, Itatinga, and Ribeira de Iguape basins and this pattern of distribution is probably the result of river capture caused by tectonic processes that affected a large area in eastern and southeastern Brazil. The species of Mimagoniates are predominantly distributed along the eastern and southeastern coastal areas, but M. microlepis is additionally found in the rio Iguacu and Tibagi basins. Mimagoniates barberi occurs in both SW margin of the upper rio Parana basin and the lower Paraguay and Mimagoniates sp. occurs in the upper Paraguay river basin. Tectonic activations of the Continental Rift of Southeastern Brazil along the eastern margin of the Upper Parana basin promoted population fragmentation responsible of the present day distribution presented by Glandulocauda melanogenys. We hypothesize that occurrence of Mimagoniates along the lowland area around the Parana basin was due to a single or a multiple fragmentation of populations along the W-SW border of the upper Parana Basin, probably due to the major tectonic origin of the Chaco-Pantanal wetland foreland basins since the Miocene as well as Cenozoic tectonic activity along the borders of the upper Parana basin, such as in the eastern Paraguay, in the Asuncion Rift. Distributional pattern of Mimagoniates suggests that its initial diversification may be related to the tectonic evolution of the Chaco-Pantanal foreland basin system and a minimum age of 2.5 M.Y are proposed for this monophyletic group. Previous hypotheses on sea level fluctuations of the late Quaternary as being the main causal mechanism promoting cladogenesis and speciation of the group are critically reviewed. Phylogeographic studies based on molecular data indicate significant differences among the isolated populations of M. microlepis. These findings suggest that a much longer period of time and a paleogeographic landscape configuration of the Brazilian southeastern coastal region explain the present observed phylogenetic and biogeographic patterns.

Araucaria forest dynamics in relation to fire frequency in southern Brazil based on fossil and modern pollen dataf

To elucidate the relationship between forest dynamics and fire frequency pollen percentages and charcoal amounts from a 120 cm long peat core and from samples of modern pollen rain were collected along a transect. The study site in southern Brazil is characterized by a species-rich mosaic of grassland-Araucaria forest. It is of crucial importance for management strategies for conservation to understand the development and maintenance of these vegetation mosaics including their sharp forest-grassland boundaries. During the late Holocene, considerable changes occurred in the area. From Anno Domini (AD) 1360 to 1410, the area was dominated by Campos (grassland) vegetation and fire was very common. From AD 1410 to 1500, Araucaria forest expanded and fire was less frequent. From AD 1500 to 1580, Campos grassland spread and the Araucaria forest ceased its development, apparently due to the increase of fire. From AD 1580 to 1935, after a decrease in fire frequency, Araucaria forest expanded again. From AD 1935 to the present, the Araucaria forest expanded while the Campos area decreased. Fire was very rare in this period. The results indicate a strong interaction of forest expansion, forming a mosaic of Campos and Araucaria forest, and the frequency of fire during the past 600 years. A possible collapse of the indigenous population following the post-Colombian colonization in southern Brazil after about AD 1550 may have caused a great reduction of fire frequency. The introduction of cattle (probably after AD 1780) and the resulting decrease of fire frequency might be the reason for forest expansion. Fire is probably the most important factor controlling the dynamics of the forest-grassland mosaics and the formation of sharp borders between these two vegetation types. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis and magnetic characterization of TmCo(2)B(2)C

A new quaternary intermetallic borocarbide TmCo(2)B(2)C has been synthesized via rapid-quench of an arc-melted ingot. Elemental and powder-diffraction analyses established its correct stoichiometry and single-phase character. The crystal structure is isomorphous with that of TmNi(2)B(2)C (I4/mmm) and is stable over the studied temperature range. Above 7 K, the paramagnetic state follows modified Curie-Weiss behavior (chi = C/(T - theta) + chi(0)) wherein chi(0) = 0.008(1) emu mol(-1) with the temperature-dependent term reflecting the paramagnetism of the Tm subsystem: mu(eff) = 7.6(2) mu(B) (in agreement with the expected value for a free Tm(3+) ion) and theta = -4.5(3) K. Long-range ferromagnetic order of the Tm sublattice is observed to develop around similar to 1 K. No superconductivity is detected in TmCo(2)B(2)C down to 20 mK, a feature which is consistent with the general trend in the RCo(2)B(2)C series. Finally, the influence of the rapid-quench process on the magnetism (and superconductivity) of TmNi(2)B(2)C will be discussed and compared to that of TmCo(2)B(2)C.

Assessment the Health Hazard from (222)Rn in Old Metalliferous Mines in San Luis, Argentina

Radon levels in two old mines in San Luis, Argentina, are reported and analyzed. The radiation dose and environmental health risk of (222)Rn concentrations to both guides and visitors were estimated. CR-39 nuclear track detectors were used for this purpose. The values for the (222)Rn concentration at each monitoring site ranged from 0.43 +/- 0.04 to 1.48 +/- 0.12 kBq m(-3) in the Los Cndores wolfram mine and from 1.8 +/- 0.1 to 6.0 +/- 0.5 kBq center dot m(-3) in the La Carolina gold mine, indicating that, in this mine, the radon levels exceed up to four times the action level of 1.5 kBq m(-3) recommended by the International Commission on Radiological Protection. The patterns of the radon transport process revealed that the La Carolina gold mine can be interpreted as a gas confined into a single tube with constant cross-section and air velocity. Patterns of radon activity, taking into account the chimney-effect winds, were used to detect tributary currents of air from shafts or larger fissures along the main adit of the Los Cndores mine, showing that radon can be used as an important tracer of tributary air currents stream out from fissures and smaller voids in the rock of the mine.

Analysis and risk estimates to workers of Brazilian granitic industries and sandblasters exposed to respirable crystalline silica and natural radionuclides

Occupational exposure to respirable crystalline silica and to radiation emitted by natural radionuclides present both in rocks and sands was studied in the Brazilian extractive process and granite product manufacture. Respirable airborne dust samples were collected in working environments, where workers perform different tasks with distinct commercial granites types, and also in places where sandblasters work with sands from different origins. The free crystalline silica contents were determined using X-ray diffraction of the respirable particulate fraction of each sample. Dust samples from granite cutting and sandblasting ambient had the natural radionuclides concentrations measured by gamma spectrometry. Dust concentrations in the workplaces were quite variable, reaching values up to 10 times higher than the respirable particle mass threshold limit value (TLV) set by the American Conference for Governmental Industrial Hygienists of 3 mg m(-3). Also the free crystalline silica concentrations were high. reaching values up to 48 times the TLV of 0.025 mg m(-3). Additionally, our results suggest that the risk of radiation-induced cancer in the granite or marble industries is negligible. However, the combined exposure to dust, gamma radiation, and radon daughter products could result in the enhancement of lung cancer risks associated to sandblasting activities. (C) 2010 Elsevier Ltd. All rights reserved.

Sugarcane Phosphoribosyl Pyrophosphate Synthetase: Molecular Characterization of a Phosphate-independent PRS

Phosphoribosyl pyrophosphate synthetase (PRS-EC:2.7.6.1) is an important enzyme present in several metabolic pathways, thus forming a complex family of isoenzymes. However, plant PRS enzymes have not been extensively investigated. In this study, a sugarcane prs gene has been characterized from the Sugar Cane Expressed Sequence Tag Genome Project. This gene contains a 984-bp open reading frame encoding a 328-amino acid protein. The predicted amino acid sequence has 77% and 78% amino acid sequence identity to Arabidopsis thaliana and Spinacia oleracea PRS4, respectively. The assignment of sugarcane PRS as a phosphate-independent PRS isoenzyme (Class II PRS) is verified following enzyme assay and phylogenetic reconstruction of PRS homologues. To gain further insight into the structural framework of the phosphate independence of sugarcane PRS, a molecular model is described. This model reveals the formation of two conserved domains elucidating the structural features involved in sugarcane PRS phosphate independence. The recombinant PRS retains secondary structure elements and a quaternary arrangement consistent with known PRS homologues, based on circular dichroism measurements.

Ligand dissociation from estrogen receptor is mediated by receptor dimerization: Evidence from molecular dynamics simulations

Estrogen Receptor (ER) is an important target for pharmaceutical design. Like other ligand-dependent transcription factors, hormone binding regulates ER transcriptional activity. Nevertheless, the mechanisms by which ligands enter and leave ERs and other nuclear receptors remain poorly understood. Here, we report results of locally enhanced sampling molecular dynamics simulations to identify dissociation pathways of two ER ligands [the natural hormone 17 beta-estradiol (E-2) and the selective ER modulator raloxifene (RAL)] from the human ER alpha ligand-binding domain in monomeric and dimeric forms. E-2 dissociation occurs via three different pathways in ER monomers. One resembles the mousetrap mechanism (Path I), involving repositioning of helix 12 (H12), others involve the separation of H8 and H11 (Path II), and a variant of this pathway at the bottom of the ligand-binding domain (Path II`). RAL leaves the receptor through Path I and a Path I variant in which the ligand leaves the receptor through the loop region between H11 and H12 (Path I`). Remarkably, ER dimerization strongly suppresses Paths II and II` for E-2 dissociation and modifies RAL escape routes. We propose that differences in ligand release pathways detected in the simulations for ER monomers and dimers provide an explanation for previously observed effects of ER quaternary state on ligand dissociation rates and suggest that dimerization may play an important, and hitherto unexpected, role in regulation of ligand dissociation rates throughout the nuclear receptor family.

Camptosemin, a tetrameric lectin of Camptosema ellipticum: structural and functional analysis

Lectins have been classified into a structurally diverse group of proteins that bind carbohydrates and glycoconjugates with high specificity. They are extremely useful molecules in the characterization of saccharides, as drug delivery mediators, and even as cellular surface makers. In this study, we present camptosemin, a new lectin from Camptosema ellipticum. It was characterized as an N-acetyl-d-galactosamine-binding homo-tetrameric lectin, with a molecular weight around 26 kDa/monomers. The monomers were stable over a wide range of pH values and exhibited pH-dependent oligomerization. Camptosemin promoted adhesion of breast cancer cells and hemagglutination, and both activities were inhibited by its binding of sugar. The stability and unfolding/folding behavior of this lectin was characterized using fluorescence and far-UV circular dichroism spectroscopies. The results indicate that chemical unfolding of camptosemin proceeds as a two-state monomer-tetramer process. In addition, small-angle X-ray scattering shows that camptosemin behaves as a soluble and stable homo-tetramer molecule in solution.

Probing conformational changes in orphan nuclear receptor: The NGFI-B intermediate is a partially unfolded dimer

Human nerve growth factor-induced B (NGFI-B) is a member of the NR4A subfamily of orphan nuclear receptors (NRs). Lacking identified ligands, orphan NRs show particular co-regulator proteins binding properties, different from other NRs, and they might have a non-classical quaternary organization. A body of evidence suggests that NRs recognition of and binding to ligands, DNA, homo- and heterodimerization partners and co-regulator proteins involve significant conformational changes of the NR ligand-binding domains (LBDs). To shed light on largely unknown biophysical properties of NGFI-B, here we studied structural organization and unfolding properties of NGFI-B ligand (like)-binding domain induced by chemical perturbation. Our results show that NGFI-B LBD undergoes a two-state guanidine hydrochloride (GndHCl) induced denaturation, as judged by changes in the a-helical content of the protein monitored by circular dichroism spectroscopy (CD). In contrast, changes in the tertiary structure of NGFI-B LBD, reported by intrinsic fluorescence, reveal a clear intermediate state. Additionally, SAXS results demonstrate that the intermediate observed by intrinsic fluorescence is a partially folded homodimeric structure, which further unfolds without dissociation at higher GndHCl concentrations. This partially unfolded dimeric assembly of NGFI-B LBD might resemble an intermediate that this domain access momentarily in the native state upon interactions with functional partners. (C) 2008 Elsevier B.V. All rights reserved.

Sediment deformation in Miocene and post-Miocene strata, Northeastern Brazil: Evidence for paleoseismicity in a passive margin

Stratigraphic intervals characterized by varied and complex styles of soft-sediment deformation structures are well preserved in Miocene and Late Pleistocene to Holocene deposits of a sedimentary basin located in Northeastern Brazil. The Miocene strata, represented by the Barreiras Formation, record only brittle structures, including numerous faults and fractures with straight and high angle-dipping planes that are often filled with sands derived from overlying beds. Folds consisting of broad anticlines and synclines are also present in this unit. The late Pleistocene to Holocene deposits, named Post-Barreiras Sediments, contain an indurated sandy package with a large variety of ductile and brittle deformation structures (i.e., massive sandstones with isolated sand fragments and breccias, undulatory strata, sand dykes and diapirs, sinks and bowls, pebbly pockets, plunged sediment mixtures, fitted sand masses, cone-shaped cracks, fault grading and sedimentary enclaves). These features, confined to sharp-based stratigraphic horizons that progressively grade downward into undisturbed deposits, are related to seismic shocks of high surface-wave magnitude (i.e., Ms>5 or 6). Amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic-wave propagation. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the depositional environment, producing laterally extensive seismites. The close proximity to earthquake epicenters would have promoted pervasive re-sedimentation due to pore overpressure, resulting high volumes of massive sandstones and breccia. The similarity between deposits with correlatable strata from many other areas along the Brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large (i.e., extension of several hundreds of kilometers) geographic area. Thus, the modern seismicity recorded along Northeastern Brazil was recurrent during the Quaternary and, perhaps, also in the Pliocene. The estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the Brazilian coast experienced tectonic stress through the last geological episodes of its evolution, which would have favored sediment accumulation and penecontemporaneous re-sedimentation. This geological context is unexpected in a passive margin, inducing to revisit the debate on how active is a passive margin. (C) 2010 Elsevier B.V. All rights reserved.

Lacustrine sediments provide geochemical evidence of environmental change during the last millennium in southeastern Brazil

A 172 cm-long sediment core was collected from a small pristine lake situated within a centripetal drainage basin in a tropical karst environment (Ribeira River valley, southeastern Brazil) in order to investigate the paleoenvironmental record provided by the lacustrine geochemistry. Sediments derived from erosion of the surrounding cambisoils contain quartz, kaolinite, mica, chlorite and goethite. Accelerator mass spectroscopy (AMS) (14)C dating provided the geochronological framework. Three major sedimentary units were identified based on the structure and color of the sediments: Unit III from 170 to 140 cm (1030 +/- 60-730 +/- 60 yr BP), Unit II from 140 to 90 cm (730 +/- 60-360 +/- 60 yr BP) and Unit I from 90 to 0 cm (360 +/- 60-0 yr BP). Results of major and trace element concentrations were analysed through multivariate statistical techniques. Factor analysis provided three factors accounting for 72.4% of the total variance. F1 and F2 have high positive loadings from K, Ba, Cs, Rb, Sr, Sc, Th, light rare earth element (LREE), Fe, Cr, Ti, Zr, Hf and Ta, and high negative loadings from Mg, Co, Cu, Zn, Br and loss on ignition (LOI). F3, with positive loadings from V and non-metals As and Sb, accounts for a low percentage (9.7%) of the total variance, being therefore of little interpretative use. The profile distribution of F1 scores reveals negative values in Units I and III, and positive values in Unit II, meaning that K, Ba, Cs, Rb, Sr, Sc, Th, LREE, Fe, Cr, Ti, Zr, Hf and Ta are relatively more concentrated in Unit II, and Mg, Co, Cu, Zn and Br are relatively more abundant in Units I and III. The observed fluctuations in the geochemical composition of the sediments are consistent with slight variations of the erosion intensity in the catchment area as a possible response to variations of climatic conditions during the last millennium. (c) 2009 Elsevier GmbH. All rights reserved.

The development of blowouts and foredunes in the Ilha Comprida barrier (Southeastern Brazil): the influence of Late Holocene climate changes on coastal sedimentation

Middle to Late Holocene barriers are conspicuous landforms in southeastern and southern Brazilian regions. The barriers in the coastal zones of northern Santa Catarina, Parana and Sao Paulo states (27 degrees 19`-24 degrees 00`S) are formed mainly by beach ridge alignments and many barriers present foredune and blowout alignments in their seaward portion. The development of these eolian landforms appears to record a regional shift in coastal dynamics and barrier building. In this context, the Ilha Comprida barrier stands out for its well-developed and well-preserved foredunes and blowouts. Based on the presence or not and type of eolian landforms, the Ilha Comprida barrier can be divided seaward into inner, middle and outer units. The inner unit is formed entirely by beach ridges. The middle unit comprises a narrow belt of blowouts (up to 15 m high) aligned alongshore. Blowout lobes pointing NNW are indicative of their generation by southern winds. The outer unit is represented by low (<= 1 m high) active or stabilized foredunes and a small transgressive dunefield (similar to 1 km(2)). Twenty-seven luminescence ages (SAR protocol) obtained for the beach ridges, foredunes, and blowouts of these three units allow definition of a precise chronology of these landforms and calculation of rates of coastal progradation. The inner unit presents ages greater than 1004 +/- 88 years. The blowouts of the middle unit show ages from 575 +/- 47 to 172 +/- 18 years. The ages of the outer unit are less than 108 +/- 10 years. Rates of coastal progradation for the inner and outer units are 0.71-0.82 m/year and 0.86-2.23 m/year, respectively. The main phase of blowout development correlates well with the Little Ice Age (LIA) climatic event. These results indicate that southern winds in subtropical Brazil became increasingly more intense and/or frequent during the LIA. These conditions persist to the present and are responsible for the development of the eolian landforms in the outer unit. Thus, barrier geomorphology can record global climatic events. The sensitivity of barrier systems in subtropical Brazil to Late Holocene climate changes was favored by the relative sea level stillstand during this time. Luminescence dating makes it possible to analyze barrier geomorphology during Late Holocene climate changes operating on timescales of a hundred to thousand years. These results improve our knowledge of barrier building and will help in the evaluation of the impact of future climate changes on coastal settings. (C) 2008 Elsevier Ltd. All rights reserved.

Controls of heavy minerals and grain size in a holocene regressive barrier (Ilha Comprida, southeastern Brazil)

Ilha Comprida is a regressive barrier island located in southeastern Brazil that was formed essentially by Quaternary sandy sediments. Ilha Comprida sediments were analyzed to assess heavy mineral indices and grain size variables. The spatial variation of heavy minerals and grain size was interpreted in terms of the present barrier dynamics and the barrier`s evolution since the Middle Holocene. These analyses allowed for the identification of the main factors and processes that control the variation of heavy minerals and grain size on the barrier. Rutile and zircon (RZi) and tourmaline and hornblende (THi) are significantly sensitive to provenance and exhibit the contributions of the Ribeira de Iguape River sediments, which reach the coast next to the northeastern end of Ilha Comprida. In addition to the influence of provenance, TZi responds mainly to hydraulic sorting processes. This agrees with a sediment transport pattern characterized by a divergence of two resultant net alongshore drifts southwest of the barrier. The sediments from the Ribeira de Iguape River reach the barrier directly through the river mouth and indirectly after temporary storage in the inner shelf. The combination of grain size and heavy mineral analyses is a reliable method for determining sediment transport patterns and provenance. (C) 2010 Elsevier Ltd. All rights reserved.

Towards high-resolution shell midden archaeology: Experimental and ethnoarchaeology in Tierra del Fuego (Argentina)

This paper discusses the ongoing ethnoarchaeological research carried out in Yamana shell middens of Tierra del Fuego. Ethnoarchaeology is used in this research as a tool to improve the archaeological methodology by testing it against anthropological, ethnographical and ethnological sources for achieving more accurate reconstructions of past societies. The ethnographical/ethnological information also is coupled with an experimental approach devised to understand physical and social processes, such as site formation processes and resource use and management. Specifically, this experimental approach was applied to the archaeological sites Tunel VII and Lanashuaia I (Tierra del Fuego, Argentina). (C) 2011 Elsevier Ltd and INQUA. All rights reserved.

Thermal history versus sedimentary history: OSL sensitivity of quartz grains extracted from rocks and sediments

The optically stimulated luminescence (OSL) sensitivity of quartz has a significant influence on luminescence dating procedures. Furthermore, identifying the natural controls of quartz OSL sensitivity is an important step towards new applications of OSL in geology such as provenance tracing. We evaluate the OSL sensitivity (total and the proportion of the informally assigned fast, medium and slow components) of single grains of quartz extracted from 10 different igneous and metamorphic rocks with known formation conditions; and from fluvial and coastal sediments with different sedimentary histories and known source rocks. This sample suite allows assessment of the variability of the OSL sensitivity of single quartz grains with respect to their primary origin and sedimentary history. We observed significant variability in the OSL sensitivity of grains within all studied rock and sediment samples, with the brightest grains of each sample being those dominated by the fast component. Quartz from rocks formed under high temperature (> 500 degrees C) conditions, such as rhyolites and metamorphic rocks from the amphibolite facies, display higher OSL sensitivity. The OSL sensitivity of fluvial sediments which have experienced only a short transport distance is relatively low. These sediments show a small increase in OSL sensitivity downstream, mainly due to a decreasing fraction of ""dim"" grains. The quartz grains from coastal sands present very high sensitivity and variability, which is consistent with their long sedimentary history. The high variability of the OSL sensitivity of quartz from coastal sands is attributed more to the mixture of grains with distinct sedimentary histories than to the provenance from many types of source rocks. The temperature of crystallization and the number of cycles of burial and solar exposure are suggested as the main natural factors controlling the OSL sensitivity of quartz grains. The increase in OSL sensitivity due to cycles of erosion and deposition surpasses the sensitivity inherited from the source rock, with this increase being mainly related to the sensitization of fast OSL components. The discrimination of grains with different sedimentary histories through their OSL sensitivities can allow the development of quantitative provenance methods based on quartz. (C) 2010 Elsevier B.V. All rights reserved.