Forest spatial heterogeneity and palm richness, abundance and community composition in Terra Firme forest, Central Amazon

The mechanisms that maintain tree diversity in tropical rain forests are still in debate. Variations in forest structural components produce forest microenvironmental heterogeneity, which in turn may affect plant performance and have been scarcely analyzed in the Amazon. Palms are widespread in the Neotropical rainforests and have relatively well known taxonomy, apart from being ecologically and economically important. The understanding of how palms respond to variation in the forest structural components may help to explain their abundance and richness in a given area. In this study, we describe a palm community and analyze how it is affected by forest microenvironmental heterogeneity. In a pristine "Terra Firme" forest at Reserva Ducke, Manaus, we recorded all adult palm trees in twenty 100 × 10 m plots. In the same plots we recorded the variation in canopy openness, the leaflitter thickness and counted all non-palm forest trees. A total of 713 individuals in 29 palm species were found. The three most abundant species were Astrocaryum sciophilum (Miq.) Pulle, A. gynacanthum Mart. and Attalea attaleoides (Barb. Rodr.) Wess. Boer. The most locally abundant species were also very frequent or occurred in a larger number of plots. There were no significant effects of litter depth, forest canopy openness and forest tree abundance on palm richness. However, in areas where leaf litter was thicker a significant lower number of palm trees occurred. In microsites where proportionally more incident light was reaching the forest understory, due to higher canopy opening, significantly more palm trees were present.

Heterogeneity of glomerular perfusion and filtration induced by epinephrine and norepinephrine

The role of catecholamines in the distribution of intrarenal blood flow and in single-nephron glomerular filtration rate (SNGFR) was evaluated in anesthetized Wistar rats by the Hanssen technique. Epinephrine (EPI) and norepinephrine (NOR) were infused to produce elevations of 20-30 mmHg in mean arterial pressure. Superficial and juxtamedullary nephron perfusion and filtration were determined by the presence of Prussian blue dye. In the control group, 100% of the nephrons presented a homogeneous pattern of perfusion and filtration. In contrast, a heterogeneous distribution of the dye was found even in the larger arteries (arciform and radial), indicating variable perfusion and filtration in both superficial and juxtamedullary nephrons. The effects of EPI and NOR were also evaluated in the superficial cortex by the micropuncture technique in two additional groups of Munich-Wistar rats. Mean SNGFR was 27% and 54% lower in the EPI- and NOR-treated groups, respectively. No change in mean intraglomerular hydraulic pressure was observed after EPI or NOR infusion in spite of a highly scattered pattern, indicating an important variability in perfusion along the superficial cortex, and/or different sensitivity of the pre- and post-glomerular arterioles. The present data suggest that EPI and NOR may affect intrarenal hemodynamics by modifying perfusion and filtration in both superficial and juxtamedullary glomeruli and not by shifting blood flow from superficial to juxtamedullary nephrons. The heterogeneous pattern of perfusion was a consequence of differential vasoconstriction along the intrarenal arteries, probably due to different density and/or sensitivity of the adrenergic receptor subtypes present in the intrarenal vascular tree.

Candidate gene linkage analysis indicates genetic heterogeneity in Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant disease of the connective tissue that affects the ocular, skeletal and cardiovascular systems, with a wide clinical variability. Although mutations in the FBN1 gene have been recognized as the cause of the disease, more recently other loci have been associated with MFS, indicating the genetic heterogeneity of this disease. We addressed the issue of genetic heterogeneity in MFS by performing linkage analysis of the FBN1 and TGFBR2 genes in 34 families (345 subjects) who met the clinical diagnostic criteria for the disease according to Ghent. Using a total of six microsatellite markers, we found that linkage with the FBN1 gene was observed or not excluded in 70.6% (24/34) of the families, and in 1 family the MFS phenotype segregated with the TGFBR2 gene. Moreover, in 4 families linkage with the FBN1 and TGFBR2 genes was excluded, and no mutations were identified in the coding region of TGFBR1, indicating the existence of other genes involved in MFS. Our results suggest that the genetic heterogeneity of MFS may be greater that previously reported.

Heterogeneity of photosystem II as it occurs in domain specific regions of the thylakoid membrane of spinach (spinacia oleracia L.)

Thylakoid membrane fractions were prepared from specific regions of thylakoid membranes of spinach (Spinacia oleracea). These fractions, which include grana (83), stroma (T3), grana core (8S), margins (Ma) and purified stroma (Y100) were prepared using a non-detergent method including a mild sonication and aqueous two-phase partitioning. The significance of PSlla and PSII~ centres have been described extensively in the literature. Previous work has characterized two types of PSII centres which are proposed to exist in different regions of the thylakoid membrane. a-centres are suggested to aggregate in stacked regions of grana whereas ~-centres are located in unstacked regions of stroma lamellae. The goal of this study is to characterize photosystem II from the isolated membrane vesicles representing different regions of the higher plant thylakoid membrane. The low temperature absorption spectra have been deconvoluted via Gaussian decomposition to estimate the relative sub-components that contribute to each fractions signature absorption spectrum. The relative sizes of the functional PSII antenna and the fluorescence induction kinetics were measured and used to determine the relative contributions of PSlla and PSII~ to each fraction. Picosecond chlorophyll fluorescence decay kinetics were collected for each fraction to characterize and gain insight into excitation energy transfer and primary electron transport in PSlla and PSII~ centres. The results presented here clearly illustrate the widely held notions of PSII/PS·I and PSlIa/PSII~ spatial separation. This study suggests that chlorophyll fluorescence decay lifetimes of PSII~ centres are shorter than those of PSlIa centres and, at FM, the longer lived of the two PSII components renders a larger yield in PSlIa-rich fractions, but smaller in PSIlr3-rich fractions.

Legal Institutions, Sectoral Heterogeneity, and Economic Development

Poor countries have lower PPP–adjusted investment rates and face higher relative prices of investment goods. It has been suggested that this happens either because these countries have a relatively lower TFP in industries producing capital goods, or because they are subject to greater investment distortions. This paper provides a micro–foundation for the cross–country dispersion in investment distortions. We first document that firms producing capital goods face a higher level of idiosyncratic risk than their counterparts producing consumption goods. In a model of capital accumulation where the protection of investors’ rights is incomplete, this difference in risk induces a wedge between the returns on investment in the two sectors. The wedge is bigger, the poorer the investor protection. In turn, this implies that countries endowed with weaker institutions face higher relative prices of investment goods, invest a lower fraction of their income, and end up being poorer. We find that our mechanism may be quantitatively important.

Homogeneity and heterogeneity of political traditions in the remaking of world order

Deux décennies après la chute de l'URSS (1991), ce mémoire propose une réévaluation de la thèse de Francis Fukuyama sur la Fin de l'Histoire, élaborée en 1989, qui postule qu'avec la chute de l'URSS aucune idéologie ne peut rivaliser avec la démocratie libérale capitaliste; et de la thèse de Samuel P. Huntington sur le Choc des civilisations, élaborée en 1993, qui pose l'existence d'un nombre fini de civilisations homogènes et antagonistes. Pourtant, lorsque confrontées à une étude approfondie des séquences historiques, ces deux théories apparaissent pour le moins relatives. Deux questions ont été traitées: l'interaction entre Idéologie et Conditions historiques, et la thèse de l'homogénéité intracivilisationnelle et de l'hétérogénéité antagoniste intercivilisationnelle. Sans les invalider complètement, cette recherche conclut toutefois que ces deux théories doivent être nuancées; elles se situent aux deux extrémités du spectre des relations internationales. La recherche effectuée a montré que les idéologies et leur poids relatif sont tributaires d'un contexte, contrairement à Fukuyama qui les pose dans l'absolu. De plus, l'étude de la Chine maoïste et particulièrement de la pensée de Mao Zedong montre que les traditions politiques locales sont plus hétérogènes qu'il n'y paraît au premier abord, ce qui relativise la thèse de Huntington. En conclusion, les rapports entre États sont plus dynamiques que ne le laissent penser les thèses de Fukuyama et de Huntington.

Genetic determinants of clinical heterogeneity in sickle cell disease

L’anémie falciforme est une maladie monogénique causée par une mutation dans le locus de la β-globine. Malgré le fait que l’anémie falciforme soit une maladie monogénique, cette maladie présente une grande hétérogénéité clinique. On présume que des facteurs environnementaux et génétiques contribuent à cette hétérogénéité. Il a été observé qu’un haut taux d’hémoglobine fœtale (HbF) diminuait la sévérité et la mortalité des patients atteints de l’anémie falciforme. Le but de mon projet était d’identifier des variations génétiques modifiant la sévérité clinique de l’anémie falciforme. Dans un premier temps, nous avons effectué la cartographie-fine de trois régions précédemment associées avec le taux d’hémoglobine fœtale. Nous avons ensuite effectué des études d’association pan-génomiques avec deux complications cliniques de l’anémie falciforme ainsi qu’avec le taux d’hémoglobine fœtale. Hormis les régions déjà identifiées comme étant associées au taux d’hémoglobine fœtale, aucun locus n’a atteint le niveau significatif de la puce de génotypage. Pour identifier des groupes de gènes modérément associés au taux d’hémoglobine fœtale qui seraient impliqués dans de mêmes voies biologiques, nous avons effectué une étude des processus biologiques. Finalement, nous avons effectué l’analyse de 19 exomes de patients Jamaïcains ayant des complications cliniques mineures de l’anémie falciforme. Compte tenu de la taille des cohortes de réplication disponibles, nous n’avons pas les moyens de valider statistiquement les variations identifiées par notre étude. Cependant, nos résultats fournissent de bons gènes candidats pour des études fonctionnelles et pour les réplications futures. Nos résultats suggèrent aussi que le β-hydroxybutyrate en concentration endogène pourraient influencer le taux d’hémoglobine fœtale. De plus, nous montrons que la cartographie-fine des régions associées par des études pan-génomiques peut identifier des signaux d’association additionnels et augmenter la variation héritable expliquée par cette région.

Factors Underlying Heterogeneous Individual Growth in Macrobrachium rosenbergii and the Effect of Size Heterogeneity on Economic Feasibility of Farming in Kuttanad ( Kerala )

School of Industrial Fisheries, Cochin University of Science and Technology

Effects of the heterogeneity of the variances on reliability generalization : An example with the beck depression inventory

Resumen tomado de la publicaci??n

Vignettes and self-reported work disability in the United States: Correction of report heterogeneity

Subjective measures of health tend to suffer from bias given by reporting heterogeneity. however, some methodologies are used to correct the bias in order to compare self-assessed health for respondents with different sociodemographic characteristics. One of the methods to correct this is the hierarchical ordered probit (hopit), which includes rates of vignettes -hypothetical individuals with a fixed health state- and where two assumptions have to be fulfilled, vignette equivalence and response consistency. this methodology is used for the self-reported work disability for a sample of the united states for 2011. The results show that even though sociodemographic variables influence rating scales, adjusting for this does not change their effect on work disability, which is only influenced by income. the inclusion of variables related with ethnicity or place of birth does not influence the true work disability. however, when only one of them is excluded, it becomes significant and affects the true level of work disability as well as income.