The role of predator overlap in the robustness and extinction of a four species predator-prey network

Predators and preys often form species networks with asymmetric patterns of interaction. We study the dynamics of a four species network consisting of two weakly connected predator-prey pairs. We focus our analysis on the effects of the cross interaction between the predator of the first pair and the prey of the second pair. This is an example where the predator overlap, which is the proportion of predators that a given prey shares with other preys, is not uniform across the network due to asymmetries in patterns of interaction. We explore the behavior of the system under different interaction strengths and study the dynamics of survival and extinction. In particular, we consider situations in which the four species have initial populations lower than their long-term equilibrium, simulating catastrophic situations in which their abundances are reduced due to human action or environmental change. We show that, under these reduced initial conditions, and depending on the strength of the cross interaction, the populations tend to oscillate before re-equilibrating, disturbing the community equilibrium and sometimes reaching values that are only a small fraction of the equilibrium population, potentially leading to their extinction. We predict that, contrary to one`s intuition, the most likely scenario is the extinction of the less predated preys. (C) 2010 Elsevier B.V. All rights reserved.

Prevalence of GJB2 (Connexin-26) and GJB6 (Connexin-30) Mutations in a Cohort of 300 Brazilian Hearing-Impaired Individuals: Implications for Diagnosis and Genetic Counseling

Objective: Hereditary nonsyndromic deafness is an autosomal recessive condition in about 80% of cases, and point mutations in the GJB2 gene (connexin 26) and two deletions in the GJB6 gene (connexin 30), del(GJB6-D13S1830) and del(GJB6-D13S1854), are reported to account for 50% of recessive deafness, Aiming at establishing the frequencies of GJB2 mutations and GJB6 deletions in the Brazilian population, we screened 300 unrelated individuals with hearing impairment, who were not affected by known deafness related syndromes. Methods: We firstly screened the most frequently reported mutations, c.35delG and c.167delT in the GJB2 gene, and del(GJB6-D13S1830) and del(GJB6-D13S1854) in the GJB6 gene, through specific techniques. The detected c.35delG and c.167delT mutations were validated by sequencing. Other mutations in the GJB2 gene were screened by single-strand conformation polymorphism and the coding region was sequenced when abnormal patterns were found. Results: Pathogenic mutations in GJB2 and GJB6 genes were detected in 41 individuals (13.7%), and 80.5% (33/41) presented these mutations in homozygosis or compound heterozygosis, thus explaining their hearing defect. The c.35delG in the GJB2 gene was the most frequent mutation (37/300; 12.4%), detected in 23% familial and 6.2% the sporadic cases. The second most frequent mutation (1%; 3/300) was the del(GJB6- D13S1830), always found associated with the c.35delG mutation. Nineteen different sequence variations were found in the GJB2 gene. In addition to the c.35delG mutation, nine known pathogenic alterations were detected 0 67delT, p.Trp24X, p.Val37lle, c.176_191del16, c.235delC, p.Leu90Pro, p.Arg127His, c.509insA, and p.Arg184Pro, Five substitutions had been previously considered benign polymorphisms: c.-15C>T, p.Val27lle, p.Met34hr, p.Ala40Ala, and p.Gly160Ser. Two previously reported Mutations of unknown pathogenicity were found (p.Lys168Arg, and c.684C>A), and two novel substitutions, p.Leu81Val (c.G241C) and p.Met195Val (c.A583G), both in heterozygosis without an accompanying mutation in the other allele. None of these latter four variants of undefined status was present in a sample of 100 hearing controls. Conclusions: The present study demonstrates that Mutations in the GJB2 gene and del(GJB6 D13S1830) are important causes of hearing impairment in Brazil, thus justifying their screening in a routine basis. The diversity of variants in our sample reflects the ethnic heterogeneity of the Brazilian population.

CONSIDERATIONS ON THE REINTRODUCTION AND RECOVERY OF THE ALAGOAS CURASSOW MITU MITU (LINNAEUS, 1766) FROM EXTINCTION USING A POTENTIALLY HYBRID CAPTIVE STOCK

The Alagoas Curassow Mitu mitu is considered extinct in the wild. Since 1979, two females and a male caught in the wild have bred successfully in captivity, and, in 1990, hybridizations between M. mitu and Razor-billed Mitu M. tuberosum were performed. By June 2008, there were around 130 living birds in two different aviaries. We sequenced two regions of the mitochondrial DNA of both captive stocks of Alagoas Curassows. We unequivocally identified hybrids that have haplotype typical of M. tuberosum. However, unless the original studbook can be recovered there is no confident way to discriminate ""pure"" M. mitu birds for breeding and reintroduction purposes. Allied with morphological data gathered in an independent study, we suggest that conservation actions need to focus on specimens with diagnostic phenotypic characters of M. mitu, and avoid birds with mitochondria, genetic contribution of M. tuberosum. Although we have detected low levels of genetic variability among captive birds, the steady increase of the captive population suggests that inbreeding depression and hybridization are not a reproductive hindrance. Reintroduction of some of these potential hybrid birds in the original area of occurrence of the Alagoas Curassow may be the only hope to fill in the ecological niche left vacant. An educational program involving local communities to conserve future reintroduction of curassows and their restored habitat is highly recommended. Accepted 12 November 2009.

An extinction-survival-type phase transition in the probabilistic cellular automaton p182-q200

We investigate the critical behaviour of a probabilistic mixture of cellular automata (CA) rules 182 and 200 (in Wolfram`s enumeration scheme) by mean-field analysis and Monte Carlo simulations. We found that as we switch off one CA and switch on the other by the variation of the single parameter of the model, the probabilistic CA (PCA) goes through an extinction-survival-type phase transition, and the numerical data indicate that it belongs to the directed percolation universality class of critical behaviour. The PCA displays a characteristic stationary density profile and a slow, diffusive dynamics close to the pure CA 200 point that we discuss briefly. Remarks on an interesting related stochastic lattice gas are addressed in the conclusions.

Factors associated with increased prevalence of human papillomavirus infection in a cohort of HIV-Infected Brazilian women

Objectives: Human papillomavirus (HPV) infection is a major risk factor for cervical disease. Using baseline data from the HIV-infected cohort of Evandro Chagas Clinical Research Institute at Fiocruz, Rio de Janeiro, Brazil, factors associated with an increased prevalence of HPV were assessed. Methods: Samples from 634 HIV-infected women were tested for the presence of HPV infection using hybrid capture 11 and polymerase chain reaction. Prevalence ratios (PR) were estimated using Poisson regression analysis with robust variance. Results: The overall prevalence of HPV infection was 48%, of which 94% were infected with a high-risk HPV. In multivariate analysis, factors independently associated with infection with high-risk HPV type were: younger age (<30 years of age; PR 1.5, 95% confidence interval (CI) 1.1-2.1), current or prior drug use (PR 1.3, 95% CI 1.0-1.6), self-reported history of HPV infection (PR 1.2, 95% CI 0.96-1.6), condom use in the last sexual intercourse (PR 1.3, 95% CI 1.1-1.7), and nadir CD4+ T-cell count <100 cells/mm(3) (PR 1.6, 95% CI 1.2-2.1). Conclusions: The estimated prevalence of high-risk HPV-infection among HIV-infected women from Rio de Janeiro, Brazil, was high. Close monitoring of HPV-related effects is warranted in all HIV-infected women, in particular those of younger age and advanced immunosuppression. (C) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Biomarkers of extracellular matrix metabolism (MMP-9 and TIMP-1) and risk of stroke, myocardial infarction and cause-specific mortality : cohort study

Objective: Turnover of the extracellular matrix in all solid organs is governed mainly by a balance between the degrading matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). An altered extracellular matrix metabolism has been implicated in a variety of diseases. We investigated relations of serum levels of MMP-9 and TIMP-1 to mortality risk from an etiological perspective. Design: The prospective Uppsala Longitudinal Study of Adult Men (ULSAM) cohort, followed from 1991–1995 for up to 18.1 years. A random population-based sample of 1,082 71-year-old men, no loss to follow-up. Endpoints were all-cause (n = 628), cardiovascular (n = 230), non-cardiovascular (n = 398) and cancer mortality (n = 178), and fatal or non-fatal myocardial infarction (n = 138) or stroke (n = 163). Results: Serum MMP-9 and TIMP-1 levels were associated with risk of all-cause mortality (Cox proportional hazard ratio [HR] per standard deviation 1.10, 95% confidence interval [CI] 1.03–1.19; and 1.11, 1.02–1.20; respectively). TIMP-1 levels were mainly related to risks of cardiovascular mortality and stroke (HR per standard deviation 1.22, 95% CI 1.09–1.37; and 1.18, 1.04–1.35; respectively). All relations except those of TIMP-1 to stroke risk were attenuated by adjustment for cardiovascular disease risk factors. Relations in a subsample without cardiovascular disease or cancer were similar to those in the total sample. Conclusion: In this community-based cohort of elderly men, serum MMP-9 and TIMP-1 levels were related to mortality risk. An altered extracellular matrix metabolism may be involved in several detrimental pathways, and circulating MMP-9 or TIMP-1 levels may be relevant markers thereof.

Life situations and the care burden for stroke pa­tients and their informal caregivers in a prospective cohort study

Background. The purpose of this study was to analyse whether the parallel life situation between stroke patients and their informal caregivers (dyads) shown in cross-sectional studies prevails also in a longitudinal perspective. Methods. A total of 377 Swedish stroke patients, aged ‡65 years, and their 268 informal caregivers were followed from hospital admission and one year on. Analyses were based on patient interviews, functional ability (MMSE) score, Nottingham Health Profile (NHP) score, Hospital Anxiety and Depression (HAD) score, self-rated health score, and the Gothenburg Quality of Life (GQL) activity score. Similar information was obtained by postal questionnaires from informal caregivers, also including information on the nature and amount of assistance provided and on Caregiver Burden (CB) score. Results. Before index admission informal caregivers provided care on average 5 h per week and after discharge 11 h per week (P < 0.0001). Support volume was associated with patient sex (more for men), low patient’s functional ability, low received municipal social service support, closeness of patient–caregiver relation, and short distance to patient’s home. Significant positive associations within the dyads were found for HAD anxiety score (P < 0.0001), total NHP score (P < 0.0001), and GQL activity score (P < 0.0001) after adjustment for patient’s age, sex, functional ability, and patient–caregiver relationship. CB score increased with amount of informal caregiver support, patient’s age, and with low functional ability and low amount of municipal social service support. All these associations were constant across time. Conclusions. There was an association within the dyads regarding anxiety score, NHP score, and activity score. CB score was generally high.

The impact of daycare attendance on math test scores for a cohort of 4th graders in Brazil

We estimate the impact of having attended center-based daycare institutions during early childhood on Math test scores at the 4th grade of elementary school. Because enrollment in daycare centers may depend on unobservable character-istics of the family and the child, we build and estimate a structural model of endogeneous choice of school to deal with the selectivity problem. We nd that attendance to daycare institutions is associated with a gain of approximately 0,04 standard deviation in Math test scores. This result is important to the extent our OLS results as well as most of the studies for Brazil nd no e¤ect associated to daycare attendance, suggesting selectivity may play a role on this finding.

Extinction, pollution, and the sustainable use of exhaustible and renewable resources

Single ownership of natural resources is conunon in many developing countries and socialist economies. The sole owner is usually the .state or society at large, and governments are responsible for either distributing exploitation rights or engaging in exploitation through their own corporations. • Under this circumstance, the notion of externality may not fully explain pollution problems existent in these nations. This paper studies the case where a single agent owns both exhaustible and renewable resources, and attempts to maximize its welfare. The resources are either perfect or imperfect substitutes. Initially, exhaustible resource extraction does not affect the renewable resource, and sustainable growth is attainable. A lactor of pollution flowing from the extraction of the nc.nrenewable resource into the growth of the renewable resource is introduced. The continuous exploitation of the exhaustible resource leads to the " optimal " extinction of the renewable resource, and sustainable growth is no longer reached. Regulation from a supra governmental agency such as an multinational institution may prove to be of utmost importance, if sustainability is to be achieved. The paper is divided into five sections. Section two provides a brief survey of the relevant literature. Section three presents the model without pollution. This factor is introduced in section four. The final section discusses some possible approaches for attaining sustainable growth, and contains the concluding remarks .

A Mismatch-Based Model for Memory Reconsolidation and Extinction in Attractor Networks

OSAN, R. , TORT, A. B. L. , AMARAL, O. B. . A mismatch-based model for memory reconsolidation and extinction in attractor networks. Plos One, v. 6, p. e23113, 2011.

Prior exposure to stress delays extinction but does not modify reinstatement of nicotine-induced conditioned place preference

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Glargine vs. NPH insulin therapy in pregnancies complicated by diabetes: An observational cohort study

Aims: The effects of glargine insulin therapy in pregnancies are not well established. We compared maternal and neonatal outcomes of women with pregestational and gestational diabetes treated with glargine or NPH insulin.Methods: A prospective cohort study was conducted analyzing outcomes from 56 women with pregestational and 82 with gestational diabetes treated with either insulin regimen.Results: Comparisons were performed among 138 women: 56 with pregestational and 82 with gestational diabetes. In relation to maternal complications, worsening of retinopathy and nephropathy, preeclampsia, micro and macroalbuminuria, and all kinds of hypoglycemia were found higher in women with pregestational diabetes NPH-treated vs. glargine-treated. In women with gestational diabetes NPH-treated, it was observed increased incidence of prepregnancy and new-onset pregnancy hypertension, micro and macroalbuminuria, as well as mild and frequent hypoglycemia, compared to glargine-treated. Among the neonatal outcomes, 1-min Apgar score <7, necessity of intensive care unit and fetal death in pregestational, while jaundice and congenital malformations in gestational diabetes, respectively, were more frequently observed in infants born to NPH-treated, compared to glargine-treated.Conclusions: Glargine use during pregnancy from preconception through delivery, showed to be safe since it is associated with decreased maternal and neonatal adverse outcomes compared with NPH insulin-treated patients. (C) 2010 Elsevier B.V. All rights reserved.