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921.
Maia R D'Alba L Shawkey MD 《Proceedings. Biological sciences / The Royal Society》2011,278(1714):1973-1980
Colours in feathers are produced by pigments or by nanostructurally organized tissues that interact with light. One of the simplest nanostructures is a single layer of keratin overlying a linearly organized layer of melanosomes that create iridescent colours of feather barbules through thin-film interference. Recently, it has been hypothesized that glossy (i.e. high specular reflectance) black feathers may be evolutionarily intermediate between matte black and iridescent feathers, and thus have a smooth keratin layer that produces gloss, but not the layered organization of melanosomes needed for iridescence. However, the morphological bases of glossiness remain unknown. Here, we use a theoretical approach to generate predictions about morphological differences between matte and glossy feathers that we then empirically test. Thin-film models predicted that glossy spectra would result from a keratin layer 110-180 nm thick and a melanin layer greater than 115 nm thick. Transmission electron microscopy data show that nanostructure of glossy barbules falls well within that range, but that of matte barbules does not. Further, glossy barbules had a thinner and more regular keratin cortex, as well as a more continuous underlying melanin layer, than matte barbules. Thus, their quasi-ordered nanostructures are morphologically intermediate between matte black and iridescent feathers, and perceived gloss may be a form of weakly chromatic iridescence. 相似文献
922.
João Paulo Souza Carlos Henrique B. A. Prado Ana Lúcia S. Albino Maria A. Damascos Gustavo Maia Souza 《Plant Ecology》2011,212(1):11-19
Deciduous, semideciduous and evergreen leaf phenological groups of Cerrado trees were studied using a representative network
composed of nodes and links to uncover the structural traits of the crown. A node denotes the origin of a branch, and a link
represents the branch emerging from a lateral bud. The network representation usually resulted in a graph with three links
per node and twice as many links as nodes for each leaf phenological group. It was possible to identify four kinds of nodes
according to the position and the number of links: initial, regular, emission and final nodes. The numbers of links and nodes
and the distance between two kinds of nodes decreased from evergreen to deciduous species. A crown with a few nodes and links
and a short distance between the kinds of nodes could facilitate the unfolding of foliage on leafless branches at the end
of the dry season in deciduous trees. In contrast, foliage persistence in evergreens could facilitate the mass flow to new
leaves produced during the entire year in a crown with a high number of links and nodes and with a large distance between
nodes. There is a clear interdependence between the degree of leaf deciduousness and the crown structural traits in Cerrado
tree species. Therefore, there are functional groups of trees in Cerrado vegetation that are characterized by a set of structural
traits in the crown, which is associated with leaf deciduousness. 相似文献
923.
Jasmin Ana Luiza M Torres Henrique MP Nunes Juliana A Passipieri Linda A Jelicks Emerson L Gasparetto David C Spray Antonio C Campos de Carvalho Rosalia Mendez-Otero 《Journal of nanobiotechnology》2011,9(1):4
Background
Stem cell therapy has emerged as a promising addition to traditional treatments for a number of diseases. However, harnessing the therapeutic potential of stem cells requires an understanding of their fate in vivo. Non-invasive cell tracking can provide knowledge about mechanisms responsible for functional improvement of host tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) have been used to label and visualize various cell types with magnetic resonance imaging (MRI). In this study we performed experiments designed to investigate the biological properties, including proliferation, viability and differentiation capacity of mesenchymal cells (MSCs) labeled with clinically approved SPIONs. 相似文献924.
Soares Medeiros LC Gomes F Maciel LR Seabra SH Docampo R Moreno S Plattner H Hentschel J Kawazoe U Barrabin H de Souza W Damatta RA Miranda K 《The Journal of eukaryotic microbiology》2011,58(5):416-423
The structural organization of parasites has been the subject of investigation by many groups and has lead to the identification of structures and metabolic pathways that may represent targets for anti-parasitic drugs. A specific group of organelles named acidocalcisomes has been identified in a number of organisms, including the apicomplexan parasites such as Toxoplasma and Plasmodium, where they have been shown to be involved in cation homeostasis, polyphosphate metabolism, and osmoregulation. Their structural counterparts in the apicomplexan parasite Eimeria have not been fully characterized. In this work, the ultrastructural and chemical properties of acidocalcisomes in Eimeria were characterized. Electron microscopy analysis of Eimeria parasites showed the dense organelles called volutin granules similar to acidocalcisomes. Immunolocalization of the vacuolar proton pyrophosphatase, considered as a marker for acidocalcisomes, showed labeling in vesicles of size and distribution similar to the dense organelles seen by electron microscopy. Spectrophotometric measurements of the kinetics of proton uptake showed a vacuolar proton pyrophosphatase activity. X-ray mapping revealed significant amounts of Na, Mg, P, K, Ca, and Zn in their matrix. The results suggest that volutin granules of Eimeria parasites are acidic, dense organelles, and possess structural and chemical properties analogous to those of other acidocalcisomes, suggesting a similar functional role in these parasites. 相似文献
925.
926.
The emerging threat of a human pandemic caused by the H5N1 avian influenza virus strain magnifies the need for controlling the incidence of H5N1 infection in domestic bird populations. Culling is one of the most widely used control measures and has proved effective for isolated outbreaks. However, the socio-economic impacts of mass culling, in the face of a disease which has become endemic in many regions of the world, can affect the implementation and success of culling as a control measure. We use mathematical modeling to understand the dynamics of avian influenza under different culling approaches. We incorporate culling into an SI model by considering the per capita culling rates to be general functions of the number of infected birds. Complex dynamics of the system, such as backward bifurcation and forward hysteresis, along with bi-stability, are detected and analyzed for two distinct culling scenarios. In these cases, employing other control measures temporarily can drastically change the dynamics of the solutions to a more favorable outcome for disease control. 相似文献
927.
Carla Maia Lídia Dionísio Maria Odete Afonso Luís Neto José Manuel Cristóv?o Lenea Campino 《Memórias do Instituto Oswaldo Cruz》2013,108(4):481-487
The Algarve Region (AR) in southern Portugal, which is an
international tourist destination, has been considered an endemic region of
zoonotic leishmaniasis caused by Leishmania infantum since the
1980s. In the present study, phlebotomine and canine surveys were conducted to
identify sandfly blood meal sources and to update the occurrence of
Leishmania infection in vectors and dogs. Four sandfly
species were captured: Phlebotomus perniciosus,
Phlebotomus ariasi, Phlebotomus sergenti
and Sergentomyia minuta. In one P. perniciosus
female, L. infantum DNA was detected. Blood meal tests showed
that this species had no host preferences and was an opportunistic feeder. An
overall canine leishmaniasis (CanL) seroprevalence of 16.06% was found; the
seroprevalence was 3.88% in dogs housed in kennels and 40.63% in dogs that
attended veterinary clinics. The simultaneous occurrence of dogs and P.
perniciosus infected with L. infantum in the AR
indicates that the region continues to be an endemic area for CanL. Our results
reinforce the need for the systematic spatial distribution of phlebotomine
populations and their Leishmania infection rates and the need
to simultaneously perform pathogen monitoring in both invertebrate and
vertebrate hosts to investigate the transmission, distribution and spreading of
Leishmania infection. 相似文献
928.
Nicolas Denancé Philippe Ranocha Nicolas Oria Xavier Barlet Marie‐Pierre Rivière Koste A. Yadeta Laurent Hoffmann François Perreau Gilles Clément Alessandra Maia‐Grondard Grardy C.M. van den Berg Bruno Savelli Sylvie Fournier Yann Aubert Sandra Pelletier Bart P.H.J. Thomma Antonio Molina Lise Jouanin Yves Marco Deborah Goffner 《The Plant journal : for cell and molecular biology》2013,73(2):225-239
929.
Danielle Maia de Souza Dan F. B. Flynn Fabrice DeClerck Ralph K. Rosenbaum Henrique de Melo Lisboa Thomas Koellner 《The International Journal of Life Cycle Assessment》2013,18(6):1231-1242
Purpose
The focus of land use modeling in life cycle impact assessment has been mainly on taxonomic measures of biodiversity, namely species richness (SR). However, increasing availability of trait data for species has led to the use of functional diversity (FD) as a promising metric to reflect the distinctiveness of species; this paper proposes the use of an FD index to calculate characterization factors (CFs) for land use impacts. Furthermore, we compare the results of the CFs to current practice and assess the increase in complexity introduced by the use of the new indicator.Methods
The model proposed is based on data compiled by previous regional meta-analysis on SR and FD, in different land use types in the Americas. The taxonomic groups included were mammals, birds, and plants. Within each study, calculated values for FD for different land use types were compared with the natural or close-to-natural state, taken as the reference situation. FD values among different land uses were standardized, and CFs were calculated. The final results were then analyzed and compared by analysis of variance and post hoc tests. A sensitivity analysis was also applied to verify the influence on the choice of the reference state.Results and discussion
The results show that significant differences exist between CFs for SR and FD metrics. Across all taxa, CFs differ significantly between land use types. The results support the use of CF for FD, as a complement to current practice. Distinct CFs should be applied for at least six groups of land use categories. The choice of reference land use type did not significantly alter the results but can be a source of variability. A sensitivity analysis evaluating the impact of alternate land use types as reference types found only few significant changes on the results.Conclusions and recommendations
Given the results, we believe the use of CFs based on FD can help on the establishment of possible links between species loss and key ecosystem functions, i.e., on the association between the midpoint indicator (e.g., biodiversity loss) and the damage caused to ecosystem quality, in terms of functions lost. Basing CFs on FD is not without challenges. Such indices are data hungry (requiring species composition and traits) require more complex calculations than current common practice, including decisions on the choice of a method to calculate FD and the selection of traits. 相似文献930.
Fabiano Gazzi Taddei Thiago Maia Davanso Lilian Castiglioni Daphine Ramiro Herrera Adilson Fransozo Rogério Caetano da Costa 《Invertebrate reproduction & development.》2013,57(4):189-199
Freshwater crabs of the family Trichodactylidae are widely distributed in major river basins of the South American continent. The population structure of one species, Dilocarcinus pagei, was analyzed in an artificial reservoir in Southeastern Brazil, recording data on the sex ratio, recruitment, and mortality. A total of 1339 crabs were collected and included 804 males and 535 females (3 ovigerous and 4 with hatchlings); the sex ratio was 1:0.61 (males: females). Two modes of male and female carapace width (CW) were recorded, with means of 14.4 mm (n = 407) and 38.9 mm (n = 394) for males and 17.9 mm CW (n = 269) and 39.2 mm (n = 267) for females. The mean size of males (CW = 26.6 ± 13.8 mm) was significantly larger than that of females (CW = 28.5 ± 12.8 mm). The data indicated that recruitment occurs in summer (January–March), with the reproductive period in spring (October–December), periods with the highest rainfall and temperature values in the region. Reproduction leads to the death of the parents, influencing the sex ratio, which oscillates mainly during the reproductive period. 相似文献