University of Seville

About: University of Seville is a education organization based out in Seville, Andalucía, Spain. It is known for research contribution in the topics: Population & Context (language use). The organization has 20098 authors who have published 47317 publications receiving 947007 citations. The organization is also known as: Universidad de Sevilla.

The variable incidence of hip fracture in southern Europe: the MEDOS Study.

Abstract: We assessed the incidence of hip fracture and ecological correlates in residents of 14 communities in six countries of Southern Europe. Hip fracture cases were recorded prospectively in defined catchment areas over a 1-year interval. A retrospective questionnaire was used to assess ecological differences between communities. During a 1-year period of observation a total of 3629 men and women over the age of 50 years were identified with hip fracture from a catchment of 3 million. In all communities the fracture rate increased exponentially with age. There were large and significant differences between centres in the doubling time for hip fracture risk with age and in crude and age-standardized rates. Greater than 4-fold and 13-fold differences in age-standardized risk were found amongst men and women respectively. The lowest rates were observed from Turkey and the highest from Seville, Crete and Porto. Fractures were significantly more frequent among women than men with the exception of three rural Turkish centres. Indeed, in rural Turkey the normal female/male ratio was reserved. Variations in incidence between regions were greater than the differences within centres between sexes, and there was a close and significant correlation between incidence rates for men and those for women in the regions studied. Excess female morbidity increased progressively from the age of 50 years but attained a plateau after the age of 80 years, suggesting a finite duration of the effect of the menopause. The retrospective questionnaire completed by 80% of cases suggested that differences in incidence between the communities studied could not be explained by differences in gonadal status in women. In both men and women cross-cultural associations were found with factors related to age or socioeconomic prosperity, the majority of which disappeared after adjustment for age. We conclude that there are marked and sizeable differences in the incidence rates of hip fracture throughout Southern Europe. The reasons for these differences are not known but affect both men and women, and are likely to be related to lifestyle or genetic factors rather than to differences in endocrine status.

Mediation Analyses in Partial Least Squares Structural Equation Modeling: Guidelines and Empirical Examples

Abstract: Partial least squares structural equation modeling (PLS-SEM) is one of the options used to analyze mediation effects. Over the past few years, the methods for testing mediation have become more sophisticated. However, many researchers continue to use outdated methods to test mediation effects in PLS-SEM, which can lead to erroneous results in some cases. One reason for the use of outdated methods is that PLS-SEM tutorials do not draw on the newest statistical findings. This chapter illustrates how to perform modern procedures in PLS-SEM by challenging the conventional approach to mediation analysis and providing better alternatives.

Rice NTRC Is a High-Efficiency Redox System for Chloroplast Protection against Oxidative Damage

Abstract: One of the mechanisms plants have developed for chloroplast protection against oxidative damage involves a 2-Cys peroxiredoxin, which has been proposed to be reduced by ferredoxin and plastid thioredoxins, Trx x and CDSP32, the FTR/Trx pathway. We show that rice (Oryza sativa) chloroplast NADPH THIOREDOXIN REDUCTASE (NTRC), with a thioredoxin domain, uses NADPH to reduce the chloroplast 2-Cys peroxiredoxin BAS1, which then reduces hydrogen peroxide. The presence of both NTR and Trx-like domains in a single polypeptide is absolutely required for the high catalytic efficiency of NTRC. An Arabidopsis thaliana knockout mutant for NTRC shows irregular mesophyll cell shape, abnormal chloroplast structure, and unbalanced BAS1 redox state, resulting in impaired photosynthesis rate under low light. Constitutive expression of wild-type NTRC in mutant transgenic lines rescued this phenotype. Moreover, prolonged darkness followed by light/dark incubation produced an increase in hydrogen peroxide and lipid peroxidation in leaves and accelerated senescence of NTRC-deficient plants. We propose that NTRC constitutes an alternative system for chloroplast protection against oxidative damage, using NADPH as the source of reducing power. Since no light-driven reduced ferredoxin is produced at night, the NTRC-BAS1 pathway may be a key detoxification system during darkness, with NADPH produced by the oxidative pentose phosphate pathway as the source of reducing power.

The dark side of curcumin.

Abstract: Dear Editor, Curcumin is a yellow–orange pigment obtained from the plant Curcuma longa. The powdered rhizome of this plant, called turmeric, is a common ingredient in curry powders and has a long history of use in traditional Asian medicine for a wide variety of disorders. In the last decade a large number of reports have been published on the beneficial effects of curcumin, and it has repeatedly been claimed that this natural product is efficient and safe for the prevention and treatment of several diseases including cancer. It is not surprising, therefore, that curcumin is currently sold as a dietary supplement and that numerous clinical trials are ongoing or recruiting participants to evaluate curcumin activity. But there is accumulating evidence that curcumin may not be so effective and safe. Because such evidence is not generally acknowledged, the purpose of this letter is to briefly review the negative properties of curcumin so that they can be balanced against its beneficial effects. Most of the evidence that supports the therapeutic potential of curcumin is mainly based on in vitro studies in which curcumin was tested at concentrations in the micromolar range. Several reports have demonstrated, however, that the plasma concentrations of curcumin in people taking relatively high oral doses of this compound are very low, typically in the nanomolar range (reviewed in Ref. 4). For instance, a recent study examined the pharmacokinetics of a curcumin preparation in 12 healthy human volunteers 0.25–72 hr after an oral dose of 10 or 12 g. Using a high-performance liquid chromatography assay with a limit of detection of 50 ng mL , only 1 subject had detectable free curcumin at any of the time points assayed. The fact that curcumin also undergoes extensive metabolism in intestine and liver means that high concentrations of curcumin cannot be achieved and maintained in plasma and tissues after oral ingestion. This is a major obstacle for the clinical development of this agent and suggests that the therapeutic potential of oral curcumin is limited. The low clinical efficiency of curcumin in the treatment of several chronic diseases such as Alzheimer’s disease and cardiovascular diseases has been discussed recently. As far as cancer is concerned, in vitro studies have demonstrated that cancer cells do not die unless they are exposed to curcumin concentrations of 5–50 lM for several hours. Because of its poor bioavailability, these concentrations are not achieved outside the gastrointestinal tract when curcumin is taken orally. Because of its extensive metabolism in intestine and liver, these concentrations cannot be maintained for several hours in the gastrointestinal tract. This suggests that the chemotherapeutic potential of oral curcumin is limited even for the treatment of cancers of the gastrointestinal tract. Accordingly, when 15 patients with advanced colorectal cancer were treated with curcumin at daily doses of 3.6 g for up to 4 months, no partial responses to treatment or decreases in tumor markers were observed. A search of the website www.clinicaltrials.gov in July 2009 showed 34 clinical trials using curcumin in a wide variety of diseases, particularly in cancer. In some of these trials, patients with several types of cancer are receiving or will receive curcumin through the oral route. For instance, in an ongoing Phase II clinical trial (NCT00094445), participants with pancreatic cancer are receiving 8 g of curcumin by mouth every day for several 8-week-periods. As discussed before, the plasma concentrations of curcumin in people taking relatively high oral doses of curcumin are very low, typically in the nanomolar range. This means that the oral administration of curcumin does not lead to cytotoxic concentrations outside the gastrointestinal tract. If one assumes that tumor cell death is necessary to achieve an efficient therapeutic response, one should not expect a very positive outcome from this trial. A Phase II Trial is also recruiting participants to test if a daily oral dose of 8 g of curcumin can improve the efficacy of the standard chemotherapy gemcitabine in patients with locally advanced or metastatic adenocarcinoma of the pancreas (NCT00192842). The rationale for this trial is based on in vitro and in vivo data that suggest that noncytotoxic concentrations of curcumin may sensitize cancer cells to the effects of anticancer drugs such as gemcitabine. Although a daily dose of 1 g kg 1 of curcumin increased the antitumor effects of gemcitabine in an orthotopic model of pancreatic cancer, this dose of curcumin (e.g. 70 g in a 70-kg person) is almost 10 times higher than that used in the clinical trial testing the combination of curcumin and gemcitabine (8 g). This makes the outcome of this trial uncertain, as curcumin can either increase or reduce the efficiency of chemotherapy depending on the concentration at which it is used. Several strategies have been proposed to overcome the low oral bioavailability of curcumin. One of these strategies has entered clinical trials and consists of using the black pepper alkaloid piperine (bioperine) to increase the bioavailability of curcumin. This strategy, however, should be used cautiously, as piperine is a potent inhibitor of drug Le tt er s to th e E di to r