Sources of N Used for Growth Following Defoliation in \u3cem\u3ePanicum Maximum\u3c/em\u3e\u3csup\u3e1\u3c/sup\u3e

The nitrogen (N) supplied to growing leaves from root uptake and mobilisation from senescing tissues may be reduced following defoliation. However, morphological adaptation of the shoot to prior defoliation occurs (Matthew et al., 2002), which may affect the potential N supply from remaining leaves. This study determined the degree to which plants of Panicum maximum utilised current root uptake and mobilisation to supply N to growing leaves and side tillers following defoliation

Layered granitoids: Interaction between continental crust recycling processes and

In this paper, field, petrographic, mineralogical, geochemical and isotopic (Rb–Sr and Sm–Nd) information from three areas within the Évora Massif (Iberian Variscan Orogen) is presented and discussed aiming at to unravel the relationships between granitoids and units mapped as migmatites and also to evaluate the interplay between mantle and crustal derived magmas. One of the areas – Almansor – displays a well-developed compositional layering (concordant with the regional Variscan structure) which was considered, in previous works, as an alternation of leucosome and melanosome. In this study, the layering is described as intercalation of diatexites, weakly foliated granitoids and trondhjemitic veins. Diatexites have characteristics of crustal melts plus restitic material and, according to geochemical and isotopic evidence, result from anatexis of Ediacaran metasediments. Weakly foliated granitoids and trondhjemitic veins from Almansor have calc-alkaline signatures and may be related to each other by crystal fractionation processes; however, the mixing between mafic (mantle-derived) and felsic (diatexitic melt) magmas revealed by the isotopic data may also explain their genesis. In the Alto de São Bento area, several igneous lithologies (tonalites, granodiorites, porphyritic granites and leucogranites) are present and show typical isotropic igneous textures. Despite structural and textural differences, geochemical data support, for most rocks, an origin from the same calk-alkaline suite, also present at Almansor. The Alto de São Bento leucogranites have an isotopic signature that, although different from that obtained in the Almansor diatexites, is still compatible with an origin involving melting of Ediacaran metasediments; compositions, with very low contents of usually incompatible elements, flat normalized REE patterns and strong negative Eu anomalies, suggest that the anatectic melt has undergone crystal fractionation processes before reaching the composition of the leucogranite magma. The Almansor outcrop is then interpreted as the remnants of a shear zone that operated as a pathway for melts that moved upward through the crust providing the locus for differentiation and mingling/mixing of magmas, whilst Alto de São Bento would correspond to the zone, at a higher crustal level, where magmas were trapped and forced to spread horizontally. At Valverde (the third area) foliated and non-foliated granitoids are spatially related and field criteria links these rocks to metamorphic protolith and anatectic melt, respectively. However, petrographic, geochemical and isotopic information shows that they all are compositionally identical trondhjemites with no evidence of metamorphic fabric. In the foliated rocks, mesoscopic features are interpreted as resulting from melt segregation structures formed in a crystallizing mush. In contrast to the previous areas, the Valverde trondhjemites probably do not belong to the main calc-alkaline plutonic suite of the Évora Massif, since they have a distinct Sr and Nd isotope signature

Family relations, parents’ educational practices, and Angolan adolescents’ values

The purpose of this study was three-fold. First, to analyze psychometric properties of the instruments used to evaluate the perceived Family relations, Familiar socialization and Angolan adolescents’ Values. Second, to predict the adolescents’ Values based on Family relations and Family socialization.Third, to analyze adolescents’ Values sex differences. For this aim, 917 adolescents (384 males, 533 females) ages 14 to 17 years (M = 15.68; SD = 1.06)completed Portuguese translations of the Family relations, Family socialization and Value questionnaires. When psychometric properties of the instruments were assessed, a Structural Equation Model (SEM) controlling for sex was carried out, with Family relations and Family socialization as independent variables, and adolescents’ Values as dependent variables. Results showed acceptable psychometric properties of the Portuguese versions of the instruments. Related to the SEM, Familiar functioning predicted Achievement, Universalism, Securityand Conformity; Parents’ Support predicted Benevolence and Conformity; Family difficulties were negatively related with Achievement and Conformity; and Punishment/coercion were negatively related with Achievement, Benevolence and Conformity. The sex variable only differentiated two adolescents’ values. Boys assigned priority to Universalism and girls assigned priority to Conformity. These findings are discussed with regard to the implications to adolescents’ socialization

The Role of the E47-p21 Pathway in Long-Term Hematopoietic Stem Cells During Homeostasis and Under Repopulation Stress

During hematopoiesis the transcription factor E47 plays two important roles. First, E47 promotes lymphoid lineage development. Second, E47 regulates proliferation of LT-HSCs, bone marrow cells uniquely capable of long-term self-renewal and multilineage reconstitution. Because hyperproliferation of LT-HSCs can be detrimental to its function, LT-HSC proliferation must be tightly regulated. We have previously shown that E47 directly activates the cell cycle inhibitor p21 in LT-HSCs. However, the biological relevance of the E47-p21 pathway to LT-HSC function in vivo has not yet been examined. Here, we used mice with reduced gene dosage in E47 and p21 individually (E47het or p21het) versus in tandem (E47hetp21het) and show that E47hetp21het LT-HSCs exhibit hyperproliferation during homeostasis and under transplantation stress. In serial adoptive transfers that rigorously challenge self-renewal, E47hetp21het LT-HSCs dramatically and progressively decline, indicating the importance of cell-intrinsic E47-p21 pathway in preserving LT-HSC self-renewal under repopulation stress. Transient numeric recovery of downstream progenitors enabled production of functionally competent myeloid cells but not lymphoid cells as common lymphoid progenitors (CLPs) were decreased and peripheral lymphocytes virtually ablated. Thus, we demonstrate a developmental compartment-specific and lineage-specific requirement for the E47-p21 pathway in maintaining LT-HSC and lymphoid lineage cells under hematopoietic repopulation stress in vivo. It is likely that other mechanisms exist by which E47 regulate LT-HSC proliferation. Therefore, we also examined if p15PAF is a direct E47 target gene since E47-deficient and p15PAF-deficient mice share very similar early hematopoietic defects during homeostasis. We show that E47 can activate p15PAF promoter-mediated transcription in a model cell line. Unexpectedly, analysis of transcript levels show a 2-fold increase in E47-deficient progenitors compared to WT, while protein levels were comparable. These findings suggest that E47 is a transcriptional regulator of p15PAF expression that is part of a broader network of transcriptional and post-translational mechanisms that regulate p15PAF expression in primary hematopoietic progenitors. Collectively, these studies demonstrate the importance of the E47-p21 pathway in LT-HSC self-renewal and lymphoid lineage development under transplantation stress and identify p15PAF as a novel E47 target gene. These findings might provide mechanistic insights into preserving and enhancing LT-HSC function for improved therapeutic hematopoietic stem cell transplantation

Native rodent species are unlikely sources of infection for Leishmania (Viannia) braziliensis along the Transoceanic Highway in Madre de Dios, Peru.

An estimated 2.3 million disability-adjusted life years are lost globally from leishmaniasis. In Peru's Amazon region, the department of Madre de Dios (MDD) rises above the rest of the country in terms of the annual incidence rates of human leishmaniasis. Leishmania (Viannia) braziliensis is the species most frequently responsible for the form of disease that results in tissue destruction of the nose and mouth. However, essentially nothing is known regarding the reservoirs of this vector-borne, zoonotic parasite in MDD. Wild rodents have been suspected, or proven, to be reservoirs of several Leishmania spp. in various ecosystems and countries. Additionally, people who live or work in forested terrain, especially those who are not regionally local and whose immune systems are thus naïve to the parasite, are at most risk for contracting L. (V.) braziliensis. Hence, the objective of this study was to collect tissues from wild rodents captured at several study sites along the Amazonian segment of the newly constructed Transoceanic Highway and to use molecular laboratory techniques to analyze samples for the presence of Leishmania parasites. Liver tissues were tested via polymerase chain reaction from a total of 217 rodents; bone marrow and skin biopsies (ear and tail) were also tested from a subset of these same animals. The most numerous rodent species captured and tested were Oligoryzomys microtis (40.7%), Hylaeamys perenensis (15.7%), and Proechimys spp. (12%). All samples were negative for Leishmania, implying that although incidental infections may occur, these abundant rodent species are unlikely to serve as primary reservoirs of L. (V.) braziliensis along the Transoceanic Highway in MDD. Therefore, although these rodent species may persist and even thrive in moderately altered landscapes, we did not find any evidence to suggest they pose a risk for L. (V.) braziliensis transmission to human inhabitants in this highly prevalent region

Some applications of quasi-velocities in optimal control

In this paper we study optimal control problems for nonholonomic systems defined on Lie algebroids by using quasi-velocities. We consider both kinematic, i.e. systems whose cost functional depends only on position and velocities, and dynamic optimal control problems, i.e. systems whose cost functional depends also on accelerations. The formulation of the problem directly at the level of Lie algebroids turns out to be the correct framework to explain in detail similar results appeared recently (Maruskin and Bloch, 2007). We also provide several examples to illustrate our construction.Comment: Revtex 4.1, 20 pages. To appear in Int. J. Geom. Meth. Modern Physic

Rapid Experimental Evolution of Pesticide Resistance in C. elegans Entails No Costs and Affects the Mating System

Pesticide resistance is a major concern in natural populations and a model trait to study adaptation. Despite the importance of this trait, the dynamics of its evolution and of its ecological consequences remain largely unstudied. To fill this gap, we performed experimental evolution with replicated populations of Caenorhabditis elegans exposed to the pesticide Levamisole during 20 generations. Exposure to Levamisole resulted in decreased survival, fecundity and male frequency, which declined from 30% to zero. This was not due to differential susceptibility of males. Rather, the drug affected mobility, resulting in fewer encounters, probably leading to reduced outcrossing rates. Adaptation, i.e., increased survival and fecundity, occurred within 10 and 20 generations, respectively. Male frequency also increased by generation 20. Adaptation costs were undetected in the ancestral environment and in presence of Ivermectin, another widely-used pesticide with an opposite physiological effect. Our results demonstrate that pesticide resistance can evolve at an extremely rapid pace. Furthermore, we unravel the effects of behaviour on life-history traits and test the environmental dependence of adaptation costs. This study establishes experimental evolution as a powerful tool to tackle pesticide resistance, and paves the way to further investigations manipulating environmental and/or genetic factors underlying adaptation to pesticides

In vitro screening for estrogenic endocrine disrupting compounds using Mozambique tilapia and sea bass scales

A wide range of estrogenic endocrine disruptors (EDCs) are accumulating in the environment and may disrupt the physiology of aquatic organisms. The effects of EDCs on fish have mainly been assessed using reproductive endpoints and in vivo animal experiments. We used a simple non-invasive assay to evaluate the impact of estrogens and EDCs on sea bass (Dicentrarchus labrax) and tilapia (Oreochromis mossambicus) scales. These were exposed to estradiol (E2), two phytoestrogens and six anthropogenic estrogenic/anti-estrogenic EDCs and activities of enzymes related to mineralized tissue turnover (TRAP, tartrate-resistant acid phosphatase and ALP, alkaline phosphatase) were measured. Semi-quantitative RT-PCR detected the expression of both membrane and nuclear estrogen receptors in the scales of both species, confirming scales as a target for E2 and EDCs through different mechanisms. Changes in TRAP or ALP activities after 30 minute and 24 h exposure were detected in sea bass and tilapia scales treated with E2 and three EDCs, although compound-, time- and dose-specific responses were observed for the two species. These results support again that the mineralized tissue turnover of fish is regulated by estrogens and reveals that the scales are a mineralized estrogen-responsive tissue that may be affected by some EDCs. The significance of these effects for whole animal physiology needs to be further explored. The in vitro fish scale bioassay is a promising non-invasive screening tool for E2 and EDCs effects, although the low sensitivity of TRAP/ALP quantification limits their utility and indicates that alternative endpoints are required