Página 1 dos resultados de 23994 itens digitais encontrados em 0.050 segundos

O efeito contextual de vizinhança sobre os indicadores de obesidade e respectivos fatores associados no projeto OBEDIARP: aplicação de modelos multinível; Neighbourhood contextual effect on the obesity indexes and correlates in the OBEDIARP Project: Multilevel models approach

Freitas, Isabel Cristina Martins de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/06/2012 Português
Relevância na Pesquisa
45.66%
Objetivos: Identificar a distribuição do índice de massa corporal (IMC), da circunferência da cintura (Ccintura), da razão cintura-quadril (RCQ) e do índice de conicidade (IC), segundo variáveis demográficas, socioeconômicas, relacionadas à saúde e comportamentais na população de 30 anos e mais, residente no município de Ribeirão Preto - SP, em 2006; avaliar o efeito modulador das regiões geográficas do município sobre os fatores associados aos indicadores antropométricos e estimar a contribuição do nível agregado para esses desfechos. Métodos: Estudo epidemiológico transversal, de base populacional, com amostragem em três estágios de sorteio. Pesos amostrais foram calculados para a recomposição do total de elegíveis e correção da taxa de não-resposta, em cada setor censitário, originando amostra ponderada de 2.197 participantes. Médias e intervalos de confiança (95%) dos indicadores antropométricos foram calculados, segundo sexo, nas categorias das variáveis independentes. Análise de variância, com um critério de classificação foi utilizada para a comparação das médias dos desfechos nas categorias das variáveis independentes. Testes de tendência linear foram aplicados para variáveis com mais de duas categorias. O nível de significância adotado foi ?=5%. Para a identificação de fatores associados aos indicadores antropométricos foram construídos modelos lineares multinível de efeitos fixos com dois níveis. Os 81 setores censitários sorteados foram agrupados em quatro regiões geográficas do município (nível agregado). A análise multinível seguiu modelo conceitual hierarquizado para avaliação do efeito direto de variáveis de nível individual e a contribuição do nível agregado sobre os desfechos (rho). Medidas de efeito (?) foram estimadas por pontos e por intervalos com 95% de confiança para as variáveis independentes. As medidas de associação foram calculadas...

Direct effect of an acyl-CoA:cholesterol acyltransferase inhibitor, F-1394, on atherosclerosis in apolipoprotein E and low density lipoprotein receptor double knockout mice

Chiwata, Tsuyoshi; Aragane, Katsumi; Fujinami, Koji; Kojima, Kazuhiro; Ishibashi, Shun; Yamada, Nobuhiro; Kusunoki, Jun
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/2001 Português
Relevância na Pesquisa
45.69%
The acyl-CoA:cholesterol acyltransferase (ACAT) enzyme is thought to be responsible for foam cell formation and the subsequent progression of atherosclerosis. The apolipoprotein E and low density lipoprotein receptor double knockout (apoE/LDLr-DKO) mouse is an animal model that develops severe hyperlipidaemia and atherosclerosis.Here we have examined the effect of oral administration of an ACAT inhibitor, F-1394, on atherosclerosis in apoE/LDLr-DKO mice fed a regular chow diet.In en face analysis, a dose of 10, 30, or 100 mg kg−1 day−1 F-1394 for 10 weeks reduced the extent of lesions visible in the aorta by 24, 28 and 38%, respectively, as detected by staining with oil red O, without affecting serum cholesterol level in these mice. At the highest dose 100 mg kg−1 day−1 of F-1394, the reduction was statistically significant.For quantitative analysis of the cellular and non-cellular components comprising the lesions at the aortic sinus, the effects of an oral dose of 100 mg kg−1 day−1 F-1394 for 15 weeks were studied. There was a significant reduction (31.9%) in the oil-red O-stained area in cross-sections of the aortic sinus. In addition, the neointimal area, as well as levels of ACAT-1 protein tended to be decreased (15.2 and 25.8%...

Direct effect of propylthiouracil on progesterone release in rat granulosa cells

Chen, Jiann-Jong; Wang, Shyi-Wu; Chien, Eileen-Jea; Wang, Paulus S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.65%
The present study was to investigate the direct effect and action mechanism of propylthiouracil (PTU), an antithyroid drug, on the production of progesterone in rat granulosa cells.PTU (3–12 mM) decreased the basal and human chorionic gonadotropin (hCG)-stimulated release of progesterone from rat granulosa cells.PTU (3–12 mM) attenuated the stimulatory effects of forskolin and 8-bromo-cyclic 3′:5′-adenosine monophosphate on progesterone release from rat granulosa cells.PTU (12 mM) inhibited the activities of both the cytochrome P450 side-chain cleavage enzyme (P450scc, conversion of 25-hydroxyl cholesterol to pregnenolone) and the 3β-hydroxysteroid dehydrogenase (conversion of pregnenolone to progesterone) in rat granulosa cells. PTU decreased the Vmax but increased the Km of P450scc.PTU (12 mM) decreased the hCG-increased amount of steroidogenic acute regulatory (StAR) protein in rat granulosa cells.The present results suggest that PTU decreases the progesterone release by granulosa cells via a thyroid-independent mechanism involving the inhibition of post-cAMP pathway, and the activities of intracellular calcium, steroidogenic enzyme, and StAR protein functions.

Implication of interleukin 18 in production of matrix metalloproteinases in articular chondrocytes in arthritis: direct effect on chondrocytes may not be pivotal

Dai, S; Shan, Z; Nishioka, K; Yudoh, K
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/2005 Português
Relevância na Pesquisa
45.69%
Objective: To clarify the effect of interleukin (IL) 18 on cartilage degeneration by studying the profile of IL18 receptor (IL18R) on chondrocytes and the direct effect of IL18 on production of matrix metalloproteinases (MMPs), aggrecanases, and tissue inhibitors of metalloproteinases (TIMPs) in articular chondrocytes.

The HIV-1 Viral Protein R Induces Apoptosis via a Direct Effect on the Mitochondrial Permeability Transition Pore

Jacotot, Etienne; Ravagnan, Luigi; Loeffler, Markus; Ferri, Karine F.; Vieira, Helena L.A.; Zamzami, Naoufal; Costantini, Paola; Druillennec, Sabine; Hoebeke, Johan; Briand, Jean Paul; Irinopoulou, Theano; Daugas, Eric; Susin, Santos A.; Cointe, Denis; Xi
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 03/01/2000 Português
Relevância na Pesquisa
45.69%
Viral protein R (Vpr) encoded by HIV-1 is a facultative inducer of apoptosis. When added to intact cells or purified mitochondria, micromolar and submicromolar doses of synthetic Vpr cause a rapid dissipation of the mitochondrial transmembrane potential (ΔΨm), as well as the mitochondrial release of apoptogenic proteins such as cytochrome c or apoptosis inducing factor. The same structural motifs relevant for cell killing are responsible for the mitochondriotoxic effects of Vpr. Both mitochondrial and cytotoxic Vpr effects are prevented by Bcl-2, an inhibitor of the permeability transition pore complex (PTPC). Coincubation of purified organelles revealed that nuclear apoptosis is only induced by Vpr when mitochondria are present yet can be abolished by PTPC inhibitors. Vpr favors the permeabilization of artificial membranes containing the purified PTPC or defined PTPC components such as the adenine nucleotide translocator (ANT) combined with Bax. Again, this effect is prevented by addition of recombinant Bcl-2. The Vpr COOH terminus binds purified ANT, as well as a molecular complex containing ANT and the voltage-dependent anion channel (VDAC), another PTPC component. Yeast strains lacking ANT or VDAC are less susceptible to Vpr-induced killing than control cells yet recover Vpr sensitivity when retransfected with yeast ANT or human VDAC. Hence...

Direct effect of light on 24-hour variation of aqueous humor protein concentration in Sprague-Dawley rats

Valderrama, Chad M.; Li, Ruixia; Liu, John H.K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.65%
Sprague-Dawley rats 10-12 weeks of age were entrained to a standard light-dark cycle with lights turned on at 6 am and off at 6 pm. Variations of 24-hour aqueous humor protein concentration were determined. Samples were taken every 4 hours (N = 10-14) under the standard light-dark condition at 8 pm, midnight, 4 am, 8 am, noon, and 4 pm. Under an acute constant dark condition, when lights were not turned on at 6 am, samples were collected at 8 am, noon, 4 pm, and 8 pm. Aqueous humor protein concentrations under the standard light-dark condition were found in the range of 0.305 ± 0.115 mg/ml (mean ± SD, N = 10) at midnight to 1.505 ± 0.342 mg/ml (N = 14) at noon. The 3 light-phase protein concentrations were each higher than the 3 dark-phase concentrations. Aqueous humor protein concentrations at 8 am, noon, and 4 pm under the acute constant dark condition were each higher than the concentrations at 8 pm (after both 2 hours and 26 hours in the dark), midnight, and 4 am, demonstrating an endogenously driven 24-hour pattern. At 8 am, noon, and 4 pm, protein concentrations were 56-147% higher when exposed to light. Intraocular pressure (IOP) was monitored using telemetry in separate groups of light-dark entrained rats under the standard light-dark condition and the acute constant dark condition. The 24-hour IOP pattern was inverse to the 24-hour pattern of aqueous humor protein concentration under the standard light-dark condition...

On the Chemical Yield of Base Lesions, Strand Breaks, and Clustered Damage Generated in Plasmid DNA by the Direct Effect of X Rays

Purkayastha, Shubhadeep; Milligan, Jamie R.; Bernhard, William A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/2007 Português
Relevância na Pesquisa
45.71%
The purpose of this study was to determine the yield of DNA base damages, deoxyribose damage, and clustered lesions due to the direct effects of ionizing radiation and to compare these with the yield of DNA trapped radicals measured previously in the same pUC18 plasmid. The plasmids were prepared as films hydrated in the range 2.5 < Γ < 22.5 mol water/mol nucleotide. Single-strand breaks (SSBs) and double-strand breaks (DSBs) were detected by agarose gel electrophoresis. Specific types of base lesions were converted into SSBs and DSBs using the base-excision repair enzymes endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). The yield of base damage detected by this method displayed a strikingly different dependence on the level of hydration (Γ) compared with that for the yield of DNA trapped radicals; the former decreased by 3.2 times as Γ was varied from 2.5 to 22.5 and the later increased by 2.4 times over the same range. To explain this divergence, we propose that SSB yields produced in plasmid DNA by the direct effect cannot be analyzed properly with a Poisson process that assumes an average of one strand break per plasmid and neglects the possibility of a single track producing multiple SSBs within a plasmid. The yields of DSBs...

Direct effect of cocaine on epigenetic regulation of PKCε gene repression in the fetal rat heart

Meyer, Kurt; Zhang, Haitao; Zhang, Lubo
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.79%
Maternal cocaine administration during gestation caused a down-regulation of PKCε expression in the heart of adult offspring resulting in an increased sensitivity to ischemia and reperfusion injury. The present study investigated the direct effect of cocaine in epigenetic modification of PKCε gene repression in the fetal heart. Hearts were isolated from gestational day 17 fetal rats and treated with cocaine in an ex vivo organ culture system. Cocaine treatment for 48 h resulted in significant decreases in PKCε protein and mRNA abundance and increases in CpG methylation at two SP1 binding sites in the PKCε promoter region (−346 and −268). Electrophoretic mobility shift assays demonstrated that CpG methylation of both SP1 sites inhibited SP1 binding. Consistently, chromatin immunoprecipitation assays showed that cocaine treatment significantly decreased binding of SP1 to the SP1 sites in the intact fetal heart. Reporter gene assays revealed that site-directed mutations of CpG methylation at both SP1 sites significantly reduced the PKCε promoter activity while methylation of a single site at either −346 or −268 did not have a significant effect. The causal effect of increased methylation in the cocaine-induced down-regulation of PKCε was demonstrated with the use of DNA methylation inhibitors. The presence of either 5-aza-2’-deoxycytodine or procainamide blocked the cocaine-induced increase in SP1 sites methylation and decrease in PKCε mRNA. The results demonstrate a direct effect of cocaine in epigenetic modification of DNA methylation and programming of cardiac PKCε gene repression linking prenatal cocaine exposure and pathophysiological consequences in the heart of adult offspring.

Intravenous immunoglobulin preparations have no direct effect on B cell proliferation and immunoglobulin production

Heidt, S; Roelen, D L; Eijsink, C; Eikmans, M; Claas, F H J; Mulder, A
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em /10/2009 Português
Relevância na Pesquisa
45.77%
Intravenous immunoglobulin (IVIg) is used for treatment of a variety of immunological disorders and in transplantation. As one of its applications in transplantation is the reduction of donor specific antibodies in the circulation, we examined the direct effect of IVIg on essential parameters of human B cell responses in vitro. Purified human B cells, human B cell hybridomas and T cells were cultured in the presence of graded concentrations of IVIg to test its effect on their proliferative capacity. To address the effect of IVIg on immunoglobulin production, we designed a novel technique making use of quantitative polymerase chain reaction to assess IgM and IgG levels. IVIg failed to inhibit proliferation of human B cells and human B cell hybridomas. In contrast, when IVIg was added to T cell cultures, a dose-dependent reduction of the proliferative capacity was observed. IVIg did not affect the levels of IgM and IgG mRNA of activated B cells. Our data show that IVIg is not capable of directly inhibiting key B cell responses. Direct B cell inhibition by IVIg seems therefore unlikely, implying that alteration in humoral immunity by IVIg is due to indirect effects on T cells and/or interactions with circulating antibodies and complement factors.

Neutralization of mitogenic lectins by intravenous immunoglobulin (IVIg) prevents T cell activation: does IVIg really have a direct effect on T cells?

Padet, L; St-Amour, I; Aubin, É; Bazin, R
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em /12/2011 Português
Relevância na Pesquisa
45.73%
Intravenous immunoglobulin (IVIg) is used for the treatment of an increasing number of autoimmune diseases. Clinical observations on IVIg-treated patients have revealed a modulation of T cell populations and functions in these patients. In vitro studies aimed at understanding the mechanisms underlying the effects of IVIg on T cells led to the conclusion that IVIg directly affected lectin-activated T cell functions. However, more recent studies have suggested the absence of a direct effect of IVIg on T cells. In the present work, we revisited the effect of IVIg on T cells using lectin-stimulated human T cells and showed that IVIg inhibited T cell functions only when added simultaneously with the activating lectin. Further, we showed that IVIg depleted from lectin-reactive IgG was no longer inhibitory, suggesting that the effect of IVIg on T cells was the consequence of lectin neutralization, possibly by interaction with glycans present in F(ab′)2 portion of IgG molecules. Our results challenge the previously widely accepted notion that IVIg exerts its anti-inflammatory effects by acting directly on T cells and suggest that effects of IVIg observed in treated patients are rather a consequence of the recently reported inhibitory effect of IVIg on antigen presentation.

Yields of damage to C4′ deoxyribose and to pyrimidines in pUC18 by the direct effect of ionizing radiation

Peoples, Anita R.; Lee, Jane; Weinfeld, Michael; Milligan, Jamie R.; Bernhard, William A.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.82%
Our mechanistic understanding of damage formation in DNA by the direct effect relies heavily on what is known of free radical intermediates studied by EPR spectroscopy. Bridging this information to stable product formation requires methods with comparable sensitivities, a criterion met by the 32P-post-labeling assay developed by Weinfeld and Soderlind, [Weinfeld,M. and Soderlind,K.-J.M. (1991) 32P-Postlabeling detection of radiation-induced DNA damage: identification and estimation of thymine glycols and phosphoglycolate termini. Biochemistry, 30, 1091–1097] which when applied to the indirect effect, detected phosphoglycolate (pg) and thymine glycol (Tg). Here we applied this assay to the direct effect, measuring product yields in pUC18 films with hydration levels (Γ) of 2.5, 16 or 23 waters per nucleotide and X-irradiated at either 4 K or room temperature (RT). The yields of pg [G(pg)] for Γ  ∼  2.5 were 2.8 ± 0.2 nmol/J (RT) and 0.2 ± 0.3 nmol/J (4 K), which is evidence that the C4′ radical contributes little to the total deoxyribose damage via the direct effect. The yield of detectable base damage [G(B*)] at Γ  ∼  2.5 was found to be 30.2  ±  1.0 nmol/J (RT) and 12.9  ±  0.7 nmol/J (4 K). While the base damage called B*...

Identification and efficient estimation of the natural direct effect among the untreated

Lendle, Samuel D; Subbaraman, Meenakshi S; van der Laan, Mark J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.84%
The natural direct effect (NDE), or the effect of an exposure on an outcome if an intermediate variable was set to the level it would have been in the absence of the exposure, is often of interest to investigators. In general, the statistical parameter associated with the NDE is difficult to estimate in the non-parametric model, particularly when the intermediate variable is continuous or high dimensional. In this paper we introduce a new causal parameter called the natural direct effect among the untreated, discus identifiability assumptions, propose a sensitivity analysis for some of the assumptions, and show that this new parameter is equivalent to the NDE in a randomized controlled trial. We also present a targeted minimum loss estimator (TMLE), a locally efficient, double robust substitution estimator for the statistical parameter associated with this causal parameter. The TMLE can be applied to problems with continuous and high dimensional intermediate variables, and can be used to estimate the NDE in a randomized controlled trial with such data. Additionally, we define and discuss the estimation of three related causal parameters: the natural direct effect among the treated, the indirect effect among the untreated and the indirect effect among the treated.

Reduced gravitational loading does not account for the skeletal effect of botulinum toxin-induced muscle inhibition suggesting a direct effect of muscle on bone

Warden, Stuart J.; Galley, Matthew R.; Richard, Jeffrey S.; George, Lydia A.; Dirks, Rachel C.; Guildenbecher, Elizabeth A.; Judd, Ashley M.; Robling, Alexander G.; Fuchs, Robyn K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.75%
Intramuscular injection of botulinum toxin (botox) into rodent hindlimbs has developed as a useful model for exploring muscle–bone interactions. Botox-induced muscle inhibition rapidly induces muscle atrophy and subsequent bone loss, with the latter hypothesized to result from reduced muscular loading of the skeleton. However, botox-induced muscle inhibition also reduces gravitational loading (as evident by reduced ground reaction forces during gait) which may account for its negative skeletal effects. The aim of this study was to investigate the skeletal effect of botox-induced muscle inhibition in cage control and tail suspended mice, with tail suspension being used to control for the reduced gravitational loading associated with botox. Female C57BL/6J mice were injected unilaterally with botox and contralaterally with vehicle, and subsequently exposed to tail suspension or normal cage activities for 6 weeks. Botox-induced muscle inhibition combined with tail suspension had the largest detrimental effect on the skeleton, causing the least gains in midshaft tibial bone mass, cortical area and cortical thickness, greatest gains in midshaft tibial medullary area, and lowest proximal tibial trabecular bone volume fraction. These data indicate botox-induced muscle inhibition has skeletal effects over and above any effect it has in altering gravitational loading...

Direct Effect of Two Naphthalene-Sulfonyl-Indole Compounds on Toxoplasma gondii Tachyzoite

Asgari, Qasem; Keshavarz, Hossein; Rezaeian, Mostafa; Motazedian, Mohammad Hossein; Shojaee, Saeedeh; Mohebali, Mehdi; Miri, Ramin
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.69%
Past studies have stated that the parasitostatic effect of IFN-γ is most likely due to the starvation of Toxoplasma gondii for tryptophan in the host cell. The aim of this study was to evaluate the direct effect of two new Naphthalene-Sulfonyl-Indole compounds as competitive molecules for tryptophan on viability and infectivity of Toxoplasma tachyzoites. Tachyzoites of RH strain were incubated in various concentrations (25–800 μM) of 1-(naphthalene-2-sulfonyl)-2,3-dihydro-1H-indole and 1-[5-(2,3-dihydro-1H-indole-1-sulfonyl)naphthalene-1-sulfonyl]-2,3-dihydro-1H-indole for 1.5 hours. Then, they were stained by PI and analyzed by FACS. To evaluate the infectivity, 2 × 106 tachyzoites exposed to the concentrations mentioned above were intraperitoneally inoculated into five mice from each group. Also, naïve parasites and parasites exposed to DMSO (control) were inoculated in both groups of mice. The LD50 of 1-(naphthalene-2-sulfonyl)-2,3-dihydro-1H-indole was 62 μmol whilst the quantity of 1-[5-(2,3-dihydro-1H-indole-1-sulfonyl)naphthalene-1-sulfonyl]-2,3-dihydro-1H-indole was more than 800 μmol. The infectivity of tachyzoites exposed to both of the compounds preserved and killed mice. No statistical correlation was seen between longevity of mice groups and different doses of the compounds. If we consider a well-organized transporter mechanism for indole compounds in the parasite...

Supremacy, direct effect, and dairy products in the early history of European law

PHELAN, William
Fonte: Instituto Universitário Europeu Publicador: Instituto Universitário Europeu
Tipo: Trabalho em Andamento Formato: application/pdf; digital
Português
Relevância na Pesquisa
45.71%
As the ECJ’s two most famous decisions, Van Gend en Loos and Costa v. ENEL, which established the direct effect and supremacy of European law, are commemorated on their fiftieth anniversaries, attention has also turned to another of the ECJ’s early decisions. On 13th November 1964, in Commission v. Luxembourg & Belgium, the Dairy Products case, the ECJ rejected the use of ‘self-help’ countermeasures in the Community legal order, and therefore marked the fundamental distinction between European law and general international law. Drawing on writings by Robert Lecourt, Paul Reuter, and Paul Kapteyn, this paper demonstrates that a direct causal link between these three cases was recognized by ECJ judges and legal scholars as early as 1965. The historical evidence presented here therefore supports previous comparative analysis that has argued that these three decisions – Van Gend, Costa, and Luxembourg & Belgium – should be acknowledged as profoundly inter-connected, in that national court application of European obligations should be understood as a substitute for the enforcement of European obligations through inter-state countermeasures.

How Tax Policy and Incentives Affect Foreign Direct Investment : A Review

Morrisset, Jacques; Pirnia, Neda
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Policy Research Working Paper; Publications & Research
Português
Relevância na Pesquisa
45.84%
With an increasing number of governments competing to attract multinational companies, fiscal incentives have become a global trend that has grown considerably in the 1990s. Poor African countries rely on tax holidays, and import duty exemptions, while industrial Western European countries allow investment allowances, or accelerated depreciation. Have governments offered unreasonably large incentives to entice firms to invest in their countries? The authors review the literature on tax policy, and foreign direct investment, and explore possibilities for research. They observe that tax incentives neither make up for serious deficiencies in a country's investment environment, nor generate the desired externalities. Long-term strategies to improve human, and physical infrastructure - and, where necessary, to streamline government policies and procedures - are more likely than incentives to attract genuine long-term investment. But more recent evidence has shown that when other factors - such as infrastructure...

The Primacy of Institutions Reconsidered : Direct Income Effects of Malaria Prevalence

Carstensen, Kai; Gundlach, Erich
Fonte: Oxford University Press on behalf of the World Bank Publicador: Oxford University Press on behalf of the World Bank
Tipo: Publications & Research :: Journal Article; Publications & Research :: Journal Article
Português
Relevância na Pesquisa
45.74%
Some recent empirical studies deny any direct effect of geography on development and conclude that institutions dominate all other potential determinants of development. An alternative view emphasizes that geographic factor such as disease ecology, as proxied by the prevalence of malaria, may have a large negative effect on income, independent of the quality of a country's institutions. For instance, pandemic malaria may create a large economic burden beyond medical costs and forgone earnings by affecting household behavior and such macroeconomic variables as international investment and trade. After controlling for institutional quality, malaria prevalence is found to cause quantitatively important negative effects on income. The robustness of this finding is checked by employing alternative instrumental variables, tests of over-identification restrictions, and tests of the validity of the point estimates and standard errors in the presence of weak instruments. The baseline findings appear to be robust to using alternative specifications...

A proposed clinical and biological interpretation of mediated interaction

Ikram, M. Arfan; VanderWeele, Tyler J.
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.83%
Understanding of causal pathways in epidemiology involves the concepts of direct and indirect effects. Recently, causal mediation analysis has been formalized to quantify these direct and indirect effects in the presence of exposure–mediator interaction and even allows for four-way decomposition of the total effect: controlled direct effect, reference interaction, mediated interaction, pure indirect effect. Whereas the other three effects can be intuitively conceptualized, mediated interaction is often considered a nuisance in statistical analysis. In this paper, we focus on mediated interaction and contrast it against pure mediation. We also propose a clinical and biological interpretation of mediated interaction using three hypothetical examples. With these examples we aim to make researchers aware that mediated interaction can actually provide important clinical and biological information.

On Partial Identification of the Pure Direct Effect

Miles, Caleb H.; Kanki, Phyllis; Meloni, Seema; Tchetgen, Eric J. Tchetgen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/09/2015 Português
Relevância na Pesquisa
45.69%
In causal mediation analysis, nonparametric identification of the pure (natural) direct effect typically relies on, in addition to no unobserved pre-exposure confounding, fundamental assumptions of (i) so-called "cross-world-counterfactuals" independence and (ii) no exposure- induced confounding. When the mediator is binary, bounds for partial identification have been given when neither assumption is made, or alternatively when assuming only (ii). We extend existing bounds to the case of a polytomous mediator, and provide bounds for the case assuming only (i). We apply these bounds to data from the Harvard PEPFAR program in Nigeria, where we evaluate the extent to which the effects of antiretroviral therapy on virological failure are mediated by a patient's adherence, and show that inference on this effect is somewhat sensitive to model assumptions.; Comment: 24 pages, 4 figures

The direct effect of EU directives: Fresh controversy or a storm in a teacup?

Albors-Llorens, Albertina
Fonte: Sweet & Maxwell Publicador: Sweet & Maxwell
Tipo: Article; accepted version
Português
Relevância na Pesquisa
45.84%
This is the author accepted manuscript. The final version is available from Sweet & Maxwell.; The judgment of the Court of Justice in Portg?s v Minist?rio da Agricultura, do Mar, do Ambiente e do Ordenamento do Territ?rio can be read as adding a new twist to the drawn-out saga on the direct effect of unimplemented directives in EU law. It essentially concludes that a defaulting State can enforce a non-implemented directive against one of its own emanations. Thus, it can be construed as endorsing a new type of direct effect that might be classified as ?intermediate? horizontal direct effect. However, the Court reached that conclusion using a rationale based on the duty to ensure the effective implementation of directives that binds the Member States and without explicitly recognising the existence of a new direct effect dimension. This comment evaluates the potential repercussions of the judgment.