Showing papers by "Universidade Federal de Minas Gerais published in 2009"

Regulation of inflammatory responses by gut microbiota and chemoattractant receptor GPR43

Abstract: The immune system responds to pathogens by a variety of pattern recognition molecules such as the Toll-like receptors (TLRs), which promote recognition of dangerous foreign pathogens. However, recent evidence indicates that normal intestinal microbiota might also positively influence immune responses, and protect against the development of inflammatory diseases. One of these elements may be short-chain fatty acids (SCFAs), which are produced by fermentation of dietary fibre by intestinal microbiota. A feature of human ulcerative colitis and other colitic diseases is a change in 'healthy' microbiota such as Bifidobacterium and Bacteriodes, and a concurrent reduction in SCFAs. Moreover, increased intake of fermentable dietary fibre, or SCFAs, seems to be clinically beneficial in the treatment of colitis. SCFAs bind the G-protein-coupled receptor 43 (GPR43, also known as FFAR2), and here we show that SCFA-GPR43 interactions profoundly affect inflammatory responses. Stimulation of GPR43 by SCFAs was necessary for the normal resolution of certain inflammatory responses, because GPR43-deficient (Gpr43(-/-)) mice showed exacerbated or unresolving inflammation in models of colitis, arthritis and asthma. This seemed to relate to increased production of inflammatory mediators by Gpr43(-/-) immune cells, and increased immune cell recruitment. Germ-free mice, which are devoid of bacteria and express little or no SCFAs, showed a similar dysregulation of certain inflammatory responses. GPR43 binding of SCFAs potentially provides a molecular link between diet, gastrointestinal bacterial metabolism, and immune and inflammatory responses.

The genome of the blood fluke Schistosoma mansoni

Abstract: Schistosoma mansoni is responsible for the neglected tropical disease schistosomiasis that affects 210 million people in 76 countries. Here we present analysis of the 363 megabase nuclear genome of the blood fluke. It encodes at least 11,809 genes, with an unusual intron size distribution, and new families of micro-exon genes that undergo frequent alternative splicing. As the first sequenced flatworm, and a representative of the Lophotrochozoa, it offers insights into early events in the evolution of the animals, including the development of a body pattern with bilateral symmetry, and the development of tissues into organs. Our analysis has been informed by the need to find new drug targets. The deficits in lipid metabolism that make schistosomes dependent on the host are revealed, and the identification of membrane receptors, ion channels and more than 300 proteases provide new insights into the biology of the life cycle and new targets. Bioinformatics approaches have identified metabolic chokepoints, and a chemogenomic screen has pinpointed schistosome proteins for which existing drugs may be active. The information generated provides an invaluable resource for the research community to develop much needed new control tools for the treatment and eradication of this important and neglected disease.

A new consensus for Trypanosoma cruzi intraspecific nomenclature: second revision meeting recommends TcI to TcVI.

Abstract: In an effort to unify the nomenclature of Trypanosoma cruzi, the causative agent of Chagas disease, an updated system was agreed upon at the Second Satellite Meeting. A consensus was reached that T. cruzi strains should be referred to by six discrete typing units (T. cruzi I-VI). The goal of a unified nomenclature is to improve communication within the scientific community involved in T. cruzi research. The justification and implications will be presented in a subsequent detailed report.

Characterizing user behavior in online social networks

Abstract: Understanding how users behave when they connect to social networking sites creates opportunities for better interface design, richer studies of social interactions, and improved design of content distribution systems. In this paper, we present a first of a kind analysis of user workloads in online social networks. Our study is based on detailed clickstream data, collected over a 12-day period, summarizing HTTP sessions of 37,024 users who accessed four popular social networks: Orkut, MySpace, Hi5, and LinkedIn. The data were collected from a social network aggregator website in Brazil, which enables users to connect to multiple social networks with a single authentication. Our analysis of the clickstream data reveals key features of the social network workloads, such as how frequently people connect to social networks and for how long, as well as the types and sequences of activities that users conduct on these sites. Additionally, we crawled the social network topology of Orkut, so that we could analyze user interaction data in light of the social graph. Our data analysis suggests insights into how users interact with friends in Orkut, such as how frequently users visit their friends' or non-immediate friends' pages. In summary, our analysis demonstrates the power of using clickstream data in identifying patterns in social network workloads and social interactions. Our analysis shows that browsing, which cannot be inferred from crawling publicly available data, accounts for 92% of all user activities. Consequently, compared to using only crawled data, considering silent interactions like browsing friends' pages increases the measured level of interaction among users.

The End of Deforestation in the Brazilian Amazon

Abstract: Brazil has two major opportunities to end the clearing of its Amazon forest and to reduce global greenhouse gas emissions substantially. The first is its formal announcement within United Nations climate treaty negotiations in 2008 of an Amazon deforestation reduction target, which prompted Norway to commit $1 billion if it sustains progress toward this target ( 1 ). The second is a widespread marketplace transition within the beef and soy industries, the main drivers of deforestation, to exclude Amazon deforesters from their supply chains ( 2 ) [supplementary online material (SOM), section (§) 4]. According to our analysis, these recent developments finally make feasible the end of deforestation in the Brazilian Amazon, which could result in a 2 to 5% reduction in global carbon emissions. The $7 to $18 billion beyond Brazil's current budget outlays that may be needed to stop the clearing [a range intermediate to previous cost estimates ( 3 , 4 )] could be provided by the REDD (Reducing Emissions from Deforestation and Forest Degradation) mechanism for compensating deforestation reduction that is under negotiation within the UN climate treaty ( 5 ), or by payments for tropical forest carbon credits under a U.S. cap-and-trade system ( 6 ).

Anisotropic etching and nanoribbon formation in single-layer graphene.

Abstract: We demonstrate anisotropic etching of single-layer graphene by thermally activated nickel nanoparticles. Using this technique, we obtain sub-10-nm nanoribbons and other graphene nanostructures with edges aligned along a single crystallographic direction. We observe a new catalytic channeling behavior, whereby etched cuts do not intersect, resulting in continuously connected geometries. Raman spectroscopy and electronic measurements show that the quality of the graphene is resilient under the etching conditions, indicating that this method may serve as a powerful technique to produce graphene nanocircuits with well-defined crystallographic edges.

Review: A review of machine learning approaches to Spam filtering

Abstract: In this paper, we present a comprehensive review of recent developments in the application of machine learning algorithms to Spam filtering, focusing on both textual- and image-based approaches. Instead of considering Spam filtering as a standard classification problem, we highlight the importance of considering specific characteristics of the problem, especially concept drift, in designing new filters. Two particularly important aspects not widely recognized in the literature are discussed: the difficulties in updating a classifier based on the bag-of-words representation and a major difference between two early naive Bayes models. Overall, we conclude that while important advancements have been made in the last years, several aspects remain to be explored, especially under more realistic evaluation settings.

Pentavalent antimonials: new perspectives for old drugs.

Abstract: Pentavalent antimonials, including meglumine antimoniate and sodium stibogluconate, have been used for more than half a century in the therapy of the parasitic disease leishmaniasis. Even though antimonials are still the first-line drugs, they exhibit several limitations, including severe side effects, the need for daily parenteral administration and drug resistance. The molecular structure of antimonials, their metabolism and mechanism of action are still being investigated. Some recent studies suggest that pentavalent antimony acts as a prodrug that is converted to active and more toxic trivalent antimony. Other works support the direct involvement of pentavalent antimony. Recent data suggest that the biomolecules, thiols and ribonucleosides, may mediate the actions of these drugs. This review will summarize the progress to date on the chemistry and biochemistry of pentavalent antimony. It will also present the most recent works being done to improve antimonial chemotherapy. These works include the development of simple synthetic methods for pentavalent antimonials, liposome-based formulations for targeting the Leishmania parasites responsible for visceral leishmaniasis and cyclodextrin-based formulations to promote the oral delivery of antimony.

Internações por condições sensíveis à atenção primária: a construção da lista brasileira como ferramenta para medir o desempenho do sistema de saúde (Projeto ICSAP - Brasil)

Abstract: Ambulatory care sensitive hospitalizations are a set of conditions for which access to effective primary care can reduce the likelihood of hospitalization. These hospitalizations have been used as an indicator of primary care performance in several countries and in three Brazilian states, but there is little consensus on which conditions should be included in this indicator. This paper presents a description of the steps undertaken to construct and validate a list for Brazil. The final list includes 20 groups of diagnostic conditions that represented 28.3% of a total of 2.8 million hospitalizations in the National Unified Health System in 2006. Gastroenteritis and complications, congestive heart failure, and asthma represented 44.1% of all ambulatory care sensitive hospitalizations. From 2000 to 2006, ambulatory care sensitive hospitalizations decreased by 15.8%, and this reduction was more significant than that observed in all other hospitalizations. The article concludes with potential applications and limitations of the proposed Brazilian list.

Ants on plants: a meta-analysis of the role of ants as plant biotic defenses

Abstract: We reviewed the evidence on the role of ants as plant biotic defenses, by conducting meta-analyses for the effects of experimental removal of ants on plant herbivory and fitness with data pooled from 81 studies. Effects reviewed were plant herbivory, herbivore abundance, hemipteran abundance, predator abundance, plant biomass and reproduction in studies where ants were experimentally removed (n = 273 independent comparisons). Ant removal exhibited strong effects on herbivory rates, as plants without ants suffered almost twice as much damage and exhibited 50% more herbivores than plants with ants. Ants also influenced several parameters of plant fitness, as plants without ants suffered a reduction in biomass (-23.7%), leaf production (-51.8%), and reproduction (-24.3%). Effects were much stronger in tropical regions compared to temperate ones. Tropical plants suffered almost threefold higher herbivore damage than plants from temperate regions and exhibited three times more herbivores. Ant removal in tropical plants resulted in a decrease in plant fitness of about 59%, whereas in temperate plants this reduction was not statistically significant. Ant removal effects were also more important in obligate ant-plants (=myrmecophytes) compared to plants exhibiting facultative relationships with hemiptera or those plants with extrafloral nectaries and food bodies. When only tropical plants were considered and the strength of the association between ants and plants taken into account, plants with obligate association with ants exhibited almost four times higher herbivory compared to plants with facultative associations with ants, but similar reductions in plant reproduction. The removal of a single ant species increased plant herbivory by almost three times compared to the removal of several ant species. Altogether, these results suggest that ants do act as plant biotic defenses, but the effects of their presence are more pronounced in tropical systems, especially in myrmecophytic plants.

Phosphate solubilizing microorganisms isolated from rhizosphere of maize cultivated in an oxisol of the Brazilian Cerrado Biome.

Abstract: Many soil microorganisms are able to transform insoluble forms of phosphorus to an accessible soluble form, contributing to plant nutrition as plant growth-promoting microorganisms (PGPM). The objective of this work was to isolate, screen and evaluate the phosphate solubilization activity of microorganisms in maize rhizosphere soil to manage soil microbial communities and to select potential microbial inoculants. Forty-five of the best isolates from 371 colonies were isolated from rhizosphere soil of maize grown in an oxisol of the Cerrado Biome with P deficiency. These microorganisms were selected based on the solubilization efficiency of inorganic and organic phosphate sources in a modified Pikovskaya’s liquid medium culture containing sodium phytate (phytic acid), soybean lecithin, aluminum phosphate (AlPO4), and tricalcium phosphate (Ca3(PO4)2). The isolates were identified based on nucleotide sequence data from the 16S ribosomal DNA (rDNA) for bacteria and actinobacteria and internal transcribed spacer (ITS) rDNA for fungi. Bacteria produced the greatest solubilization in medium containing tricalcium phosphate. Strains B17 and B5, identified as Bacillus sp. and Burkholderia sp., respectively, were the most effective, mobilizing 67% and 58.5% of the total P (Ca3(PO4)2) after 10 days, and were isolated from the rhizosphere of the P efficient L3 maize genotype, under P stress. The fungal population was the most effective in solubilizing P sources of aluminum, phytate, and lecithin. A greater diversity of P-solubilizing microorganisms was observed in the rhizosphere of the P efficient maize genotypes suggesting that the P efficiency in these cultivars may be related to the potential to enhance microbial interactions of P-solubilizing microorganisms.

Prevalence of dementia in Latin America: a collaborative study of population-based cohorts.

Abstract: Background: Dementia is becoming a major public health problem in Latin America (LA), yet epidemiological information on dementia remains scarce in this region. This study analyzes data from epidemiological studies on the prevalence of dementia in LA and compares the prevalence of dementia and its causes across countries in LA and attempts to clarify differences from those of developed regions of the world. Methods: A database search for population studies on rates of dementia in LA was performed. Abstracts were also included in the search. Authors of the publications were invited to participate in this collaborative study by sharing missing or more recent data analysis with the group. Results: Eight studies from six countries were included. The global prevalence of dementia in the elderly (≥65 years) was 7.1% (95% CI: 6.8-7.4), mirroring the rates of developed countries. However, prevalence in relatively young subjects (65-69 years) was higher in LA studies The rate of illiteracy among the elderly was 9.3% and the prevalence of dementia in illiterates was two times higher than in literates. Alzheimer's disease was the most common cause of dementia. Conclusions: Compared with studies from developed countries, the global prevalence of dementia in LA proved similar, although a higher prevalence of dementia in relatively young subjects was evidenced, which may be related to the association between low educational level and lower cognitive reserve, causing earlier emergence of clinical signs of dementia in the LA elderly population.

Warfare in Biodiversity Hotspots

Abstract: Conservation efforts are only as sustainable as the social and political context within which they take place. The weakening or collapse of sociopolitical frameworks during wartime can lead to habitat destruction and the erosion of conservation policies, but in some cases, may also confer ecological benefits through altered settlement patterns and reduced resource exploitation. Over 90% of the major armed conflicts between 1950 and 2000 occurred within countries containing biodiversity hotspots, and more than 80% took place directly within hotspot areas. Less than one-third of the 34 recognized hotspots escaped significant conflict during this period, and most suffered repeated episodes of violence. This pattern was remarkably consistent over these 5 decades. Evidence from the war-torn Eastern Afromontane hotspot suggests that biodiversity conservation is improved when international nongovernmental organizations support local protected area staff and remain engaged throughout the conflict. With biodiversity hotspots concentrated in politically volatile regions, the conservation community must maintain continuous involvement during periods of war, and biodiversity conservation should be incorporated into military, reconstruction, and humanitarian programs in the world's conflict zones.

Relationship between body image disturbance and incidence of depression: the SUN prospective cohort

Abstract: Body image disturbance is an increasing problem in Western societies and is associated with a number of mental health outcomes including anorexia, bulimia, body dysmorphia, and depression. The aim of this study was to assess the association between body image disturbance and the incidence of depression. This study included 10,286 participants from a dynamic prospective cohort of Spanish university graduates, who were followed-up for a median period of 4.2 years (Seguimiento Universidad de Navarra – the SUN study). The key characteristic of the study is the permanently open recruitment that started in 1999. The baseline questionnaire included information about body mass index (BMI) and the nine figure schemes that were used to assess body size perception. These variables were grouped according to recommended classifications and the difference between BMI and body size perception was considered as a proxy of body image disturbance. A subject was classified as an incident case of depression if he/she was initially free of depression and reported a physician-made diagnosis of depression and/or the use of antidepressant medication in at least one of the follow-up questionnaires. The association between body image disturbance and the incidence of depression was estimated by calculating the multivariable adjusted Odds Ratio (OR) and its 95% Confidence Interval (95% CI), using logistic regression models. The cumulative incidence of depression during follow-up in the cohort was 4.8%. Men who underestimated their body size had a high percentage of overweight and obesity (50.1% and 12.6%, respectively), whereas women who overestimated their body size had a high percentage of underweight (87.6%). The underestimation exhibited a negative association with the incidence of depression among women (OR: 0.72, 95% CI: 0.54 – 0.95), but this effect disappeared after adjusting for possible confounding variables. The proportion of participants who correctly perceived their body size was high (53.3%) and gross misperception was seldom found, with most cases selecting only one silhouette below (42.7%) or above (2.6%) their actual BMI. We found no association between body image disturbance and subsequent depression in a cohort of university graduates in Spain.

Detecting spammers and content promoters in online video social networks

Abstract: A number of online video social networks, out of which YouTube is the most popular, provides features that allow users to post a video as a response to a discussion topic. These features open opportunities for users to introduce polluted content, or simply pollution, into the system. For instance, spammers may post an unrelated video as response to a popular one aiming at increasing the likelihood of the response being viewed by a larger number of users. Moreover, opportunistic users--promoters--may try to gain visibility to a specific video by posting a large number of (potentially unrelated) responses to boost the rank of the responded video, making it appear in the top lists maintained by the system. Content pollution may jeopardize the trust of users on the system, thus compromising its success in promoting social interactions. In spite of that, the available literature is very limited in providing a deep understanding of this problem. In this paper, we go a step further by addressing the issue of detecting video spammers and promoters. Towards that end, we manually build a test collection of real YouTube users, classifying them as spammers, promoters, and legitimates. Using our test collection, we provide a characterization of social and content attributes that may help distinguish each user class. We also investigate the feasibility of using a state-of-the-art supervised classification algorithm to detect spammers and promoters, and assess its effectiveness in our test collection. We found that our approach is able to correctly identify the majority of the promoters, misclassifying only a small percentage of legitimate users. In contrast, although we are able to detect a significant fraction of spammers, they showed to be much harder to distinguish from legitimate users.

Histological and Stereological Evaluation of Zebrafish (Danio rerio) Spermatogenesis with an Emphasis on Spermatogonial Generations

Abstract: The zebrafish has become an important vertebrate model for basic and biomedical research, including the research field of the biology of reproduction. However, very few morphological and stereological data are available regarding zebrafish testis structure and spermatogenesis. In this careful histomorphometric evaluation of the testis, we studied spermatogonial cells using molecular markers, determined the combined duration of meiotic and spermiogenic phases, and examined the formation of the Sertoli cell barrier (tight junctions). We found at least nine spermatogonial generations and propose a morphology-based nomenclature for spermatogonial generations that is compatible with the one used in higher vertebrates. The number of germ cells per cyst increased dramatically (1 to approximately 1360 cells) from undifferentiated spermatogonia type A to early spermatids. The combined duration of meiotic and spermiogenic phases is approximately 6 days, one of the shorter periods among the teleost fish investigated to date. The number of Sertoli cells per cyst increased 9-fold during the maturational cycle of spermatogenic cysts and stabilized in the meiotic phase at a ratio of approximately 100 early spermatids per Sertoli cell (Sertoli cell efficiency). Similarly to mammals, Sertoli cell proliferation ceased in the meiotic phase, coinciding with the formation of tight junctions between Sertoli cells. Hence, the events taking place during puberty in the germinal epithelium of mammals seem to recapitulate the "life history" of each individual spermatogenic cyst in zebrafish.

Construction Learning as a Function of Frequency, Frequency Distribution, and Function.

Abstract: This article considers effects of construction frequency, form, function, and prototypicality on second language acquisition (SLA). It investigates these relationships by focusing on naturalistic SLA in the European Science Foundation corpus ( Perdue, 1993 ) of the English verb–argument constructions (VACs): verb locative (VL), verb object locative (VOL), and ditransitive (VOO). Goldberg (2006) argued that Zipfian type/token frequency distributions ( Zipf, 1935 ) in natural language constructions might optimize learning by providing one very high-frequency exemplar that is also prototypical in meaning. This article tests and confirms this proposal for naturalistic English as a second language. We show that VAC type/token distribution in the input is Zipfian and that learners first use the most frequent, prototypical, and generic exemplar (e.g., put in the VOL VAC, give in the VOO ditransitive, etc.). Learning is driven by the frequency and frequency distribution of exemplars within constructions and by the match of their meaning to the construction prototype. [ABSTRACT FROM AUTHOR]

Drug-Drug Interactions Associated with Length of Stay and Cost of Hospitalization

Abstract: Purpose To evaluate the prevalence of drug-drug interactions (DDI) in prescriptions of hospitalized patients and to identify risk factors associated. Methods A retrospective cross-sectional analysis of prescription data and medical records from a public hospital in Brazil was conducted to identify potential DDI. An inappropriate drug combination was identified and classified with a standard drug interaction source. The main diagnoses were classified with Charlson Comorbidity Index (CCI). Sex, age, polypharmacy and length of stay, among other variables, were correlated with the frequency of potential DDI. Results The study included 589 patients and 3,585 prescriptions. Thirty-seven percent of the patients were exposed to at least one potential interaction during their stay in the hospital. The most frequent interacting pair was Digoxin+Furosemide (11%). In univariate analysis, several variables were associated with DDI, including sex, age, number of prescribed drugs, length and cost of hospitalization and CCI. Multivariate analysis showed that the adjusted odds of being prescribed a potential DDI among patients in polypharmacy was almost five-fold that of patients taking less than five drugs. Further, length of stay, CCI and cost of hospitalization were independently associated with DDI. Conclusion Analysis of prescription data found that a substantial number of potential DDI were identified. Results of this study indicate that DDI is associated with number of prescribed drugs, increased duration of stay in the hospital and cost, which suggest that DDI are a significant clinical and economic problem. Potential damage to patients could be avoided.

The potential ecological costs and cobenefits of REDD: a critical review and case study from the Amazon region

Abstract: The United Nations climate treaty may soon include a mechanism for compensating tropical nations that succeed in reducing carbon emissions from deforestation and forest degradation, source of nearly one fifth of global carbon emissions. We review the potential for this mechanism [reducing emissions from deforestation and degradation (REDD)] to provoke ecological damages and promote ecological cobenefits. Nations could potentially participate in REDD by slowing clear-cutting of mature tropical forest, slowing or decreasing the impact of selective logging, promoting forest regeneration and restoration, and expanding tree plantations. REDD could also foster efforts to reduce the incidence of forest fire. Potential ecological costs include the accelerated loss (through displaced agricultural expansion) of low-biomass, high-conservation-value ecosystems, and substitution of low-biomass vegetation by monoculture tree plantations. These costs could be avoided through measures that protect low-biomass native ecosystems. Substantial ecological cobenefits should be conferred under most circumstances, and include the maintenance or restoration of (1) watershed functions, (2) local and regional climate regimes, (3) soils and biogeochemical processes, (4) water quality and aquatic habitat, and (5) terrestrial habitat. Some tools already being developed to monitor, report and verify (MRV) carbon emissions performance can also be used to measure other elements of ecosystem function, making development of MRV systems for ecological cobenefits a concrete possibility. Analysis of possible REDD program interventions in a large-scale Amazon landscape indicates that even modest flows of forest carbon funding can provide substantial cobenefits for aquatic ecosystems, but that the functional integrity of the landscape's myriad small watersheds would be best protected under a more even spatial distribution of forests. Because of its focus on an ecosystem service with global benefits, REDD could access a large pool of global stakeholders willing to pay to maintain carbon in forests, thereby providing a potential cascade of ecosystem services to local stakeholders who would otherwise be unable to afford them.