Detection of Leishmania braziliensis in human paraffin-embedded tissues from Tucumán, Argentina by polymerase chain reaction

American cutaneous leishmaniasis (ACL) is an endemic disease in Northern Argentina. We applied the polymerase chain reaction (PCR) followed by a hybridization labelled probe to 21 paraffin embedded human skin biopsies, already analyzed histologically, from leishmaniasis endemic areas in the province of Tucumán, Argentina. We used primers previously designed to detect a Leishmania-specific 120-base-pair fragment of kinetoplast DNA minicircle, other two primer pairs that amplify kDNA minicircles belonging to the L. braziliensis and L. mexicana complexes respectively, and specific oligonucleotide primers to detect L. (V.) braziliensis which amplify the sequence of the ribosomal protein L-14 of this species. The PCR-hybridization showed a sensitivity of 90.5% when compared to the histopathology test which was 61.9%. Five of the total samples analyzed were positive for the L. braziliensis complex whilst none was positive for the L. mexicana complex. The specific primers for L. (V.) braziliensis detected the parasite in four samples. These results are consistent with those reported for close endemic areas and demonstrate that the causative agent of human leishmaniasis in the analyzed cases was L. (V.) braziliensis. PCR should be used as a diagnostic tool for tegumentary leishmaniasis, especially in the mucosal form, and as a valuable technique for the identification of the Leishmania species that causes the disease in certain areas.     

Environmental signaling and evolutionary change: can exposure of pregnant mammals to environmental estrogens lead to epigenetically induced evolutionary changes in embryos?

DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic expression in mammalian cells. In this review, we propose how certain natural agents, through their dietary consumption, could induce changes in physiological aspects in mammalian mothers, leading to alterations in DNA methylation patterns of the developing fetus and to the emergence of new phenotypes and evolutionary change. Nevertheless, we hypothesize that this process would require (i) certain key periods in the ontogeny of the organism where the environmental stimuli could produce effects, (ii) particular environmental agents as such stimuli, and (iii) that a genomic persistent change be consequently produced in a population. Depending on the persistence of the environmental stimuli and on whether the affected genes are imprinted genes, induced changes in DNA methylation patterns could become persistent. Moreover, some fragments could be more frequently methylated than others over several generations, leading to biased base change and evolutionary consequences.     

Pentamidine is an antiparasitic and apoptotic drug that selectively modifies ubiquitin

We have determined the cytotoxic properties of pentamidine isethionate (2) towards the promastigotes of the protozoan parasite Leishmania infantum. The leishmanicidal activity of 2 was 60 times higher after 72 h of incubation than that of cisplatin (4). The pentamidine salt 2 induced a higher amount of programmed cell death (PCD) than cisplatin, which is associated with inhibition of DNA synthesis and cell-cycle arrest in the G2/M phase. Circular dichroism (CD) data indicate that binding of 2 to calf-thymus DNA (CT-DNA) induces conformational changes in the DNA double helix, consistent with a B-->A transition. Moreover, the interaction of 2 with ubiquitin led to a 6% increase in the beta-sheet content of the protein as observed by CD spectroscopy. Fluorescence-spectroscopy studies agreed with the CD data, showing that the pentamidine portion of 2 induces a significant decrease in the fluorescence of the Ub residues Phe4 and Phe45 located on the beta-cluster of the molecule, but not of Tyr59 on the alpha-cluster. These data indicate that pentamidine specifically modifies the beta-cluster, i.e., the 'basic face' of ubiquitin. Our results suggest that the biochemical mechanism of action of pentamidine may be a consequence of its dual binding to DNA and proteins.     

A functional analysis of the crown architecture of tropical forest<Emphasis Type="Italic"> Psychotria</Emphasis> species: do species vary in light capture efficiency and consequently in carbon gain and growth?

The crown architectures of 11 Psychotria species native to Barro Colorado Island, Panama were reconstructed from field measurements of leaf and branch geometry with the three-dimensional simulation model Y-plant. The objective was to assess the role of species differences in architecture in light capture and carbon gain in their natural understory environment. When species were grouped according to their putative light environment preference, the shade tolerant species were found to have a small but significantly higher efficiency of light capture for both diffuse and direct light as compared to the light demanding species. Within each grouping, however, there were few significant differences in light capture efficiency among species. The lower efficiencies of light demanding species was due to slightly higher self-shading and slightly lower angular efficiencies. Simulations of whole plant assimilation showed that light demanding species had greater daily assimilation in both direct and diffuse light due to the significantly greater light availability in the sites where light demanding species were found, as compared to those where shade tolerant species occurred. Among light demanding species, the above ground relative growth rate measured over a 1-year period by applying allometric equations for mass versus linear dimensions, was positively correlated with diffuse PFD and with mean daily assimilation estimated from Y-plant. For the shade tolerant plants, there was no significant correlation between RGR and mean daily assimilation or with any measure of light availability, probably because they occurred over a much narrower range of light environments. Overall, the results reveal a strong convergence in light capture efficiencies among the Psychotria species at lower values than previously observed in understory plants using similar approaches. Constraints imposed by other crown functions such as hydraulics and biomechanical support may place upper limits on light capture efficiency.Abbreviations E_a Efficiency of light absorption (dimensionless) - E_adir Efficiency of direct light absorption (dimensionless) - E_adif Efficiency of diffuse light absorption (dimensionless) - D_E Display efficiency (dimensionless) - P_E Projection efficiency (dimensionless) - CosI Mean cosine of incidence (dimensionless) - aLAR_e Effective leaf area ratio (m² g^–1) - A_tot Daily assimilation (mmol m^–2 day^–1) - A_dir Daily assimilation in direct PFD (mmol m^–2 day^–1) - A_dif Daily assimilation in diffuse PFD (mmol m^–2 day^–1)     

Seedling survival responses to irradiance are differentially influenced by low-water availability in four tree species of the Iberian cool temperate–Mediterranean ecotone

Inter-specific differences in seedling survival responses along a sun-shade gradient and the influence of low-water availability were examined for four Iberian tree species (Quercus robur L., Quercus pyrenaica Willd., Pinus sylvestris L. and Pinus pinaster Ait.) typical of the cool temperate–Mediterranean transition zone. Seedlings were grown under controlled conditions in a factorial experiment with four levels of irradiance (1%, 6%, 20% and 100% of full sunlight) and two levels of water availability. Five censuses (from late spring to autumn) leading to four regular intervals (T₀ → T_I; T_I → T_II; T_II → T_III; T_III → T_IV) were established. Statistical models of seedling survival as a function of irradiance were calibrated throughout the whole experiment (T₀ → T_IV) and also for each time interval and water availability level. Seedling survival responses among different species diverged both in the type of functional response to irradiance and in their response to water stress. Ranking of species according to shade tolerance (Q. pyrenaica > Q. robur > P. sylvestris > P. pinaster) contrasted with tolerance of high irradiance and conformed to a hypothetical sun-shade trade-off for survival (i.e. species having higher survival in low irradiance—oaks—had poorer survival at high irradiance and vice-versa). Low-water availability also differentially affected each species, with pines being more drought tolerant than oaks. At an intra-specific level, low-water availability decreased survival of Q. pyrenaica under both high and low irradiance. For Q. robur, however, low-water availability exerted a relatively stronger effect under low irradiance. Consequences of the interplay between irradiance and water availability for explaining segregation and coexistence of forest tree species at the ecotone between cool temperate and Mediterranean forests are discussed.     

Ecophysiological traits associated with drought in Mediterranean tree seedlings: individual responses versus interspecific trends in eleven species

Species differ regarding their drought tolerance and individuals of a given species can modify their morphology and physiology in response to drought. However, since evolutionary and ecological selective pressures differ, individual and interspecific responses to drought might not match. We determined summer survival and a number of ecophysiological variables in two factorial experiments with seedlings of eleven tree species present in Mediterranean ecosystems, grown under slowly imposed water stress and control conditions. Plants experiencing drought exhibited reduced growth, low specific leaf area, chlorophyll content, and photosynthetic rate when compared to the controls, and species-specific drought tolerance was associated with an analogous set of trait values. However, while species with high leaf area ratio and shoot-root ratio exhibited greater drought tolerance, drought induced the reversed response within species. Contrary to expectations, water use efficiency was lower in drought-tolerant species and decreased in water-stressed individuals compared to the control plants. There was a distinctive phylogenetic signal in the functional grouping of species, with oaks, pines, and other genera being clearly different from each other in their drought tolerance and in their functional responses to drought. However, all relationships between ecophysiological variables and drought tolerance were significant after accounting for phylogenetic effects, with the exception of the relationship between drought tolerance and photochemical efficiency. Our results show that drought tolerance is not achieved by a single combination of trait values, and that even though evolutionary processes and individual responses tend to render similar results in terms of functional traits associated with drought, they do not necessarily match.     

Patterns of sequence conservation in presynaptic neural genes

Background  

The neuronal synapse is a fundamental functional unit in the central nervous system of animals. Because synaptic function is evolutionarily conserved, we reasoned that functional sequences of genes and related genomic elements known to play important roles in neurotransmitter release would also be conserved.     

Isolation and characterization of 10 microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean relict plant

? Premise of the study: The main aim of this study was to isolate and characterize microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean shrub relict of the early Tertiary, which inhabits western Mediterranean islands and coasts. Microsatellites will be useful for investigating biogeography and landscape genetics across the species distribution range, including current or past gene flow. ? Methods and Results: Seventeen microsatellite loci were characterized, of which 10 were polymorphic and amplified for a total of 56 alleles in three populations of C. tricoccon. The markers revealed average coefficients of expected heterozygosity (H(e) = 0.425), observed heterozygosity (H(o) = 0.282), and inbreeding coefficient value per population (F(IS) = 0.408). ? Conclusions: These microsatellite primers will potentially be useful in the study of population and landscape genetics, conservation status of isolated populations, island-continental distribution, current or historical movements between populations, and in the investigation of the consequences of dispersal mechanisms of these plants.     

Forest fragmentation leads to food web contraction

Fragmentation and loss of habitat are critical components of the global change currently threatening biodiversity and ecosystem functioning. We studied the effects of habitat loss through fragmentation on food web structure, by constructing and analyzing plant‐herbivore and host‐parasitoid food webs including more than 400 species and over 120 000 feeding records, in 19 Chaco Serrano remnants of differing areas. Food web structure was altered by habitat fragmentation, with different metrics being affected depending on interaction type, and with all changes being driven by the reduced size of networks in smaller fragments. Only connectance varied in both quantitative and qualitative analyses, being negatively related to area. In addition, the interactions were represented by proper successive subsets, modulated mainly by resource availability (plant–herbivore) or consumer specialization (host–parasitoid), as forest size decreased. The results suggest that habitat loss has led to food web contraction around a central core of highly‐connected species, for plant–herbivore as well as for host–parasitoid systems. The study provides new insights into the effects of human perturbations on complex biological systems.     

Phenotypic plasticity to light of two congeneric trees from contrasting habitats: Brazilian Atlantic Forest versus cerrado (savanna)

The Brazilian Atlantic Forest is a typically multi-layer tropical forest, while cerrado (savanna) is a patchy habitat with different physiognomy. Despite these differences, both habitats have high light heterogeneity. Functional traits of Dalbergia nigra and D. miscolobium from the Atlantic Forest and cerrado, respectively, were evaluated under shade (25% of full sunlight) and full sunlight in a nursery experiment. We hypothesised that both species should benefit from high phenotypic plasticity in relation to light. Plasticity was estimated using the relative distance phenotypic index (RDPI). D. miscolobium had lower shoot growth under both light conditions, suggesting it has low competitive capacity in the forest environment, which could explain its limited ability to expand over areas of Atlantic Forest. The studied species exhibited photoprotection strategies under high light and improved light capture under low light. Stomatal conductance, ETR(max) (maximum electron transport rate), PPFD(sat) (saturating photosynthetically active photon flux density), chlorophyll and carotenoid content had higher RDPI than stem morphological traits. Although both species showed considerable phenotypic plasticity, D. miscolobium had higher RDPI for eight of 11 evaluated traits. This high plasticity could be one of the factors that explain the occurrence of this species in a wide range of environmental conditions, from open grassland to dense woodlands, and it could also reflect its adaptation to high light. D. nigra also had considerable plasticity and good growth performance in both shade and full sunlight, but its absence in areas of cerrado suggests that factors other than light limit its occurrence in these habitats.