Determinants of Serum PCBs in Adolescents and Adults: Regression Tree Analysis and Linear Regression Analysis

Regression tree analysis, a non-parametric method, was undertaken to identify predictors of the serum concentration of polychlorinated biphenyls (sum of marker PCB ¹ ABBREVIATIONS: BMI: body-mass index, CV: cross validation, ln: natural logarithm, ns: not significant, PCAHs: polychlorinated aromatic hydrocarbons, PCBs: polychlorinated biphenyls, R² _a: adjusted coefficient of determination, VIF: variance inflation factor. View all notes 138, 153, and 180) in humans. This method was applied on biomonitoring data of the Flemish Environment and Health study (2002–2006) and included 1679 adolescents and 1583 adults. Potential predictor variables were collected via a self-administered questionnaire, assessing information on lifestyle, food intake, use of tobacco and alcohol, residence history, health, education, hobbies, and occupation. Relevant predictors of human PCB exposure were identified with regression tree analysis using ln-transformed sum of PCBs, separately in adolescents and adults. The obtained results were compared with those from a standard linear regression approach. The results of the non-parametric analysis confirm the selection of the covariates in the multiple regression models. In both analyses, blood fat, gender, age, body-mass index (BMI) or change in bodyweight, former breast-feeding, and a number of nutritional factors were identified as statistically significant predictors in the serum PCB concentration, either in adolescents, in adults or in both. Regression trees can be used as an explorative analysis in combination with multiple linear regression models, where relationships between the determinants and the biomarkers can be quantified.     

A universal approach to eliminate antigenic properties of alpha-gliadin peptides in celiac disease

Celiac disease is caused by an uncontrolled immune response to gluten, a heterogeneous mixture of wheat storage proteins, including the α-gliadins. It has been shown that α-gliadins harbor several major epitopes involved in the disease pathogenesis. A major step towards elimination of gluten toxicity for celiac disease patients would thus be the elimination of such epitopes from α-gliadins. We have analyzed over 3,000 expressed α-gliadin sequences from 11 bread wheat cultivars to determine whether they encode for peptides potentially involved in celiac disease. All identified epitope variants were synthesized as peptides and tested for binding to the disease-associated HLA-DQ2 and HLA-DQ8 molecules and for recognition by patient-derived α-gliadin specific T cell clones. Several specific naturally occurring amino acid substitutions were identified for each of the α-gliadin derived peptides involved in celiac disease that eliminate the antigenic properties of the epitope variants. Finally, we provide proof of principle at the peptide level that through the systematic introduction of such naturally occurring variations α-gliadins genes can be generated that no longer encode antigenic peptides. This forms a crucial step in the development of strategies to modify gluten genes in wheat so that it becomes safe for celiac disease patients. It also provides the information to design and introduce safe gluten genes in other cereals, which would exhibit improved quality while remaining safe for consumption by celiac disease patients.     

Flexible nest-site selection under anthropogenic habitat change in an Afrotropical understorey insectivore

Human activities impact upon natural habitats used by birds for breeding and foraging, and lead to changes in the composition and spatial distribution of predator communities, mainly through loss, fragmentation and disturbance of formerly pristine habitat. Yet possible fitness consequences of such changes through impacts on bird nest-site selection remain poorly known. Here we study nest-site selection and reproductive success of Placid Greenbuls Phyllastrephus placidus in the Taita Hills, southeast Kenya. We show that habitat features associated with nest-site selection by this insectivorous, open-cup-nesting bird species vary among forest fragments that are exposed to different levels of habitat disturbance. Such differences in sites selected for breeding result from a plastic response to fragment-specific conditions or may be driven by fragment-specific variation in the distribution and availability of certain habitat features. Given the overall high nest predation rates in our study area, we expected variation in nest-site selection to correlate with reproductive success and nestling condition, but detected no such relationship. Because predator density and nest predation rates may vary strongly in space and time, a better understanding of spatio-temporal variation in predator communities is needed to assess the possible adaptive value of nest-site selection strategies for reducing the high predation rates that are typical for this and many other open-cup-nesting tropical passerines.     

Influence of cryopreservation on human periodontal ligament cells in vitro

Cryopreservation of teeth before autotransplantation may create new possibilities in dentistry. The purpose of this study was to examine the effect of a standardised cryopreservation procedure on human periodontal ligament (PDL) cell cultures. Human PDL fibroblasts obtained from immature third molars of 11 patients were cultured and divided into two groups. The experimental group was cryopreserved and cultured after thawing. The control group was cultured without cryopreservation. A comparison was made between cryopreserved and control cells. To evaluate possible differences in the characteristics of the fibroblasts, the cells in both groups were tested for viability (membrane integrity), growth capacity and alkaline phosphatase (ALP) expression. The Wilcoxon test for paired comparison between cryopreserved and non-cryopreserved cells was performed for each characteristic. The results showed that membrane integrity of cells was not influenced by cryopreservation. There was no statistically significant difference in growth capacity between cryopreserved and control cells. Non-cryopreserved cells were slightly stronger positive for ALP, but the difference was not statistically significant. From these experiments it can be concluded that the observed parameters are not influenced by cryopreservation.     

Thiamine pyrophosphate biosynthesis and transport in the nematode Caenorhabditis elegans

Thiamine (vitamin B1) is required in the diet of animals, and thiamine deficiency leads to diseases such as beri-beri and the Wernicke-Korsakoff syndrome. Dietary thiamine (vitamin B1) consists mainly of thiamine pyrophosphate (TPP), which is transformed into thiamine by gastrointestinal phosphatases before absorption. It is believed that TPP itself cannot be transported across plasma membranes in significant amounts. We have identified a partial loss-of-function mutation in the Caenorhabditis elegans gene (tpk-1) that encodes thiamine pyrophosphokinase, which forms TPP from thiamine at the expense of ATP inside cells. The mutation slows physiological rhythms and the phenotype it produces can be rescued by TPP but not thiamine supplementation. tpk-1 functions cell nonautonomously, as the expression of wild-type tpk-1 in one tissue can rescue the function of other tissues that express only mutant tpk-1. These observations indicate that, in contrast to expectation from previous evidence, TPP can be transported across cell membranes. We also find that thiamine supplementation partially rescues the phenotype of partial loss-of-function mutants of the Na/K ATPase, providing genetic evidence that thiamine absorption, and/or redistribution from the absorbing cells, requires the full activity of this enzyme.     

Pseudorabies virus US3 protein kinase mediates actin stress fiber breakdown

Disruption of specific components of the host cytoskeleton has been reported for several viruses and is thought to be beneficial for viral replication and spread. Our previous work demonstrated that infection of swine kidney (SK-6) cells with pseudorabies virus (PRV), a swine alphaherpesvirus, induced actin stress fiber breakdown. In the present study, using several PRV deletion mutants, we found that the US3 serine/threonine (S/T) protein kinase is involved in breakdown of actin stress fibers in different PRV-infected cell lines. Further, by transfection assays, we showed that PRV US3 itself, in the absence of other viral proteins, is able to trigger actin stress fiber breakdown when it is localized in sufficient amounts in the nucleus.     

Development of a questionnaire to determine the case detection delay of leprosy: A mixed-methods cultural validation study

BackgroundDelay in case detection is a risk factor for developing leprosy-related impairments, leading to disability and stigma. The objective of this study was to develop a questionnaire to determine the leprosy case detection delay, defined as the period between the first signs of the disease and the moment of diagnosis, calculated in total number of months. The instrument was developed as part of the PEP4LEP project, a large-scale intervention study which determines the most effective way to implement integrated skin screening and leprosy post-exposure prophylaxis with a single-dose of rifampicin (SDR-PEP) administration in Ethiopia, Mozambique and Tanzania.Methodology/Principal findingsA literature review was conducted and leprosy experts were consulted. The first draft of the questionnaire was developed in Ethiopia by exploring conceptual understanding, item relevance and operational suitability. Then, the first draft of the tool was piloted in Ethiopia, Mozambique and Tanzania. The outcome is a questionnaire comprising nine questions to determine the case detection delay and two annexes for ease of administration: a local calendar to translate the patient’s indication of time to number of months and a set of pictures of the signs of leprosy. In addition, a body map was included to locate the signs. A ‘Question-by-Question Guide’ was added to the package, to provide support in the administration of the questionnaire. The materials will be made available in English, Oromiffa (Afaan Oromo), Portuguese and Swahili via https://www.infolep.org.Conclusions/SignificanceIt was concluded that the developed case detection delay questionnaire can be administered quickly and easily by health workers, while not inconveniencing the patient. The instrument has promising potential for use in future leprosy research. It is recommended that the tool is further validated, also in other regions or countries, to ensure cultural validity and to examine psychometric properties like test-retest reliability and interrater reliability.     

The SNARE protein vti1a functions in dense‐core vesicle biogenesis

The SNARE protein vti1a is proposed to drive fusion of intracellular organelles, but recent data also implicated vti1a in exocytosis. Here we show that vti1a is absent from mature secretory vesicles in adrenal chromaffin cells, but localizes to a compartment near the trans‐Golgi network, partially overlapping with syntaxin‐6. Exocytosis is impaired in vti1a null cells, partly due to fewer Ca²⁺‐channels at the plasma membrane, partly due to fewer vesicles of reduced size and synaptobrevin‐2 content. In contrast, release kinetics and Ca²⁺‐sensitivity remain unchanged, indicating that the final fusion reaction leading to transmitter release is unperturbed. Additional deletion of the closest related SNARE, vti1b, does not exacerbate the vti1a phenotype, and vti1b null cells show no secretion defects, indicating that vti1b does not participate in exocytosis. Long‐term re‐expression of vti1a (days) was necessary for restoration of secretory capacity, whereas strong short‐term expression (hours) was ineffective, consistent with vti1a involvement in an upstream step related to vesicle generation, rather than in fusion. We conclude that vti1a functions in vesicle generation and Ca²⁺‐channel trafficking, but is dispensable for transmitter release.