scholarly journals Molecular approaches for a better understanding of the epidemiology and population genetics ofLeishmania

Parasitology ◽  
2010 ◽  
Vol 138 (4) ◽  
pp. 405-425 ◽  
Author(s):  
G. SCHÖNIAN ◽  
K. KUHLS ◽  
I. L. MAURICIO
Keyword(s):  
Gold Standard ◽  
Population Genetic ◽  
Field Studies ◽  
Epidemiological Studies ◽  
Small Sample ◽  
Clinical Samples ◽  
Molecular Approaches ◽  
Sexual Recombination ◽  
Small Sample Sizes ◽  
Analytical Tools

SUMMARYMolecular approaches are being used increasingly for epidemiological studies of visceral and cutaneous leishmaniases. Several molecular markers resolving genetic differences betweenLeishmaniaparasites at species and strain levels have been developed to address key epidemiological and population genetic questions. The current gold standard, multilocus enzyme typing (MLEE), needs cultured parasites and lacks discriminatory power. PCR assays identifying species directly with clinical samples have proven useful in numerous field studies. Multilocus sequence typing (MLST) is potentially the most powerful phylogenetic approach and will, most probably, replace MLEE in the future. Multilocus microsatellite typing (MLMT) is able to discriminate below the zymodeme level and seems to be the best candidate for becoming the gold standard for distinction of strains. Population genetic studies by MLMT revealed geographical and hierarchic population structure inL. tropica, L. majorand theL. donovanicomplex. The existence of hybrids and gene flow betweenLeishmaniapopulations suggests that sexual recombination is more frequent than previously thought. However, typing and analytical tools need to be further improved. Accessible databases should be created and sustained for integrating data obtained by different researchers. This would allow for global analyses and help to avoid biases in analyses due to small sample sizes.

scholarly journals An investigation of the population genetic structure of pollack (Pollachius pollachius) based on microsatellite markers

2006 ◽  
Vol 63 (9) ◽  
pp. 1705-1709 ◽  
Author(s):  
Grégory Charrier ◽  
Jean-Dominique Durand ◽  
Louis Quiniou ◽  
Jean Laroche
Keyword(s):  
Genetic Structure ◽  
Genetic Differentiation ◽  
Population Genetic Structure ◽  
Population Genetic ◽  
Small Sample ◽  
Significant Genetic Differentiation ◽  
Small Sample Sizes ◽  
Southern Norway ◽  
Passive Drift ◽  
Oceanic Currents

Abstract In order to explore the population genetic structure of pollack (Pollachius pollachius) along the European coast, of 282 fish sampled from four locations along the Atlantic French coast and from one location off southern Norway were genotyped at six microsatellite loci. The limited genetic differentiation among samples may be due to high levels of larval dispersal, through passive drift with oceanic currents. Alternatively, populations may have diverged too recently for significant genetic differentiation to have become evident. Furthermore, small sample sizes and the limited number of loci may have hampered the detection of genetic structure. Nevertheless, a weak but significant genetic differentiation was detected between samples originating from the western English Channel and the Bay of Biscay.

scholarly journals Exposure to Vitamin D Fortification Policy in Prenatal Life and the Risk of Childhood Asthma: Results From the D-Tect Study

Nutrients ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 924
Author(s):  
Thorsteinsdottir ◽  
Maslova ◽  
Jacobsen ◽  
Frederiksen ◽  
Keller ◽  
...  
Keyword(s):  
Vitamin D ◽  
Study Design ◽  
Childhood Asthma ◽  
Proportional Hazards ◽  
Epidemiological Studies ◽  
Vitamin D Insufficiency ◽  
Cox Proportional Hazards ◽  
Small Sample ◽  
Increased Risk ◽  
Small Sample Sizes

Prenatal vitamin D insufficiency may be associated with an increased risk of developing childhood asthma. Results from epidemiological studies are conflicting and limited by short follow-up and small sample sizes. The objective of this study was to examine if children born to women exposed to the margarine fortification policy with a small dose of extra vitamin D during pregnancy had a reduced risk of developing asthma until age 9 years, compared to children born to unexposed women. The termination of a Danish mandatory vitamin D fortification policy constituted the basis for the study design. We compared the risk of inpatient asthma diagnoses in all Danish children born two years before (n = 106,347, exposed) and two years after (n = 115,900, unexposed) the termination of the policy. The children were followed in the register from 0–9 years of age. Data were analyzed using Cox proportional hazards regression. The Hazard Ratio for the first inpatient asthma admission among exposed versus unexposed children was 0.96 (95%CI: 0.90–1.04). When stratifying by sex and age, 0–3 years old boys exposed to vitamin D fortification showed a lower asthma risk compared to unexposed boys (HR 0.78, 95%CI: 0.67–0.92). Prenatal exposure to margarine fortification policy with extra vitamin D did not affect the overall risk of developing asthma among children aged 0–9 years but seemed to reduce the risk among 0–3 years old boys. Taking aside study design limitations, this could be explained by different sensitivity to vitamin D from different sex-related asthma phenotypes in children with early onset, and sex differences in lung development or immune responses.

Prey Behavior Leads to Predator: A Case Study of the Himalayan Tahr and the Snow Leopard in Sagarmatha (Mt. Everest) National Park, Nepal

2009 ◽  
Vol 55 (4) ◽  
pp. 315-327 ◽  
Author(s):  
Som B. Ale ◽  
Joel S. Brown
Keyword(s):  
Field Studies ◽  
Small Sample ◽  
Snow Leopard ◽  
Vigilance Behavior ◽  
Prey Behavior ◽  
Himalayan Tahr ◽  
Snow Leopards ◽  
Small Sample Sizes ◽  
Large Predators

Rare, elusive predators offer few sightings, hindering research with small sample sizes and lack of experimentation. While predators may be elusive, their prey are more readily observed. Prey respond to the presence of a predator, and these fear responses may have population- and community-level consequences. Anti-predator behaviors, such as vigilance, allow us to sidestep the difficulty of direct field studies of large predators by studying them indirectly. Here we used a behavioral indicator, the vigilance behavior of the Himalayan tahr, the snow leopard's main local prey, to reveal the distribution and habitat use of snow leopards in the Mt. Everest region of Nepal. We combined techniques of conventional field biology with concepts of foraging theory to study prey behavior in order to obtain insights into the predator's ecology. The Himalayan tahr's vigilance behavior correlates with the distribution of snow leopard signs. Tahr actually led us to six sightings of snow leopards. We conclude that behavioral indicators provided by prey offer a valuable tool for studying and monitoring stealthy and rare carnivores.

scholarly journals Frontiers in RNA biology: advances from a small fly Drosophila melanogaster

2016 ◽  
Vol 38 (2) ◽  
pp. 21-25
Author(s):  
James B. Brown ◽  
Susan E. Celniker
Keyword(s):  
Rna Processing ◽  
Small Sample ◽  
Rna Seq ◽  
Ribonucleoprotein Complexes ◽  
Rna Biology ◽  
Cell Type Specific ◽  
Exciting Time ◽  
Small Sample Sizes ◽  
Analytical Tools ◽  
Processing Mechanisms

In this article, we discuss emerging frontiers in RNA biology from a historical perspective. The field is currently undergoing yet another transformative expansion. RNA-seq has revealed that splicing, and, more generally, RNA processing is far more complex than expected, and the mechanisms of regulation are correspondingly sophisticated. Our understanding of the molecular machines involved in RNA metabolism is incomplete and derives from small sample sizes. Even if we manage to complete a catalogue of molecular species, RNA isoforms and the ribonucleoprotein complexes that drive their genesis, the horizons of molecular dynamics and cell-type-specific processing mechanisms await. This is an exciting time to enter into the study of RNA biology; analytical tools, wet and dry, are advancing rapidly, and each new measurement modality brings into view another new function or activity of versatile RNA. Since the dawn of sequence-based RNA biology, we have come a long way.

The epidemiology and possible mechanisms of disinfection by-products in drinking water

2009 ◽  
Vol 367 (1904) ◽  
pp. 4043-4076 ◽  
Author(s):  
Mark J. Nieuwenhuijsen ◽  
James Grellier ◽  
Rachel Smith ◽  
Nina Iszatt ◽  
James Bennett ◽  
...  
Keyword(s):  
Drinking Water ◽  
Health Effects ◽  
Semen Quality ◽  
Epidemiological Studies ◽  
Small Sample ◽  
Epidemiological Evidence ◽  
Adverse Health Effects ◽  
Adverse Health ◽  
Small Sample Sizes ◽  
By Products

This paper summarizes the epidemiological evidence for adverse health effects associated with disinfection by-products (DBPs) in drinking water and describes the potential mechanism of action. There appears to be good epidemiological evidence for a relationship between exposure to DBPs, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers including colorectal cancer is inconclusive and inconsistent. There appears to be some evidence for an association between exposure to DBPs, specifically THMs, and little for gestational age/intrauterine growth retardation and, to a lesser extent, pre-term delivery, but evidence for relationships with other outcomes such as low birth weight, stillbirth, congenital anomalies and semen quality is inconclusive and inconsistent. Major limitations in exposure assessment, small sample sizes and potential biases may account for the inconclusive and inconsistent results in epidemiological studies. Moreover, most studies have focused on total THMs as the exposure metric, whereas other DBPs appear to be more toxic than the THMs, albeit generally occurring at lower levels in the water. The mechanisms through which DBPs may cause adverse health effects including cancer and adverse reproductive effects have not been well investigated. Several mechanisms have been suggested, including genotoxicity, oxidative stress, disruption of folate metabolism, disruption of the synthesis and/or secretion of placental syncytiotrophoblast-derived chorionic gonadotropin and lowering of testosterone levels, but further work is required in this area.

A novel confidence interval for a single proportion in the presence of clustered binary outcome data

2019 ◽  
Vol 29 (1) ◽  
pp. 111-121
Author(s):  
Meghan I Short ◽  
Howard J Cabral ◽  
Janice M Weinberg ◽  
Michael P LaValley ◽  
Joseph M Massaro
Keyword(s):  
Confidence Interval ◽  
Clustered Data ◽  
Epidemiological Studies ◽  
Outcome Data ◽  
Small Sample ◽  
Interval Methods ◽  
Sample Sizes ◽  
Wide Range ◽  
Small Sample Sizes ◽  
Over Dispersion

Estimating the precision of a single proportion via a 100(1−α)% confidence interval in the presence of clustered data is an important statistical problem. It is necessary to account for possible over-dispersion, for instance, in animal-based teratology studies with within-litter correlation, epidemiological studies that involve clustered sampling, and clinical trial designs with multiple measurements per subject. Several asymptotic confidence interval methods have been developed, which have been found to have inadequate coverage of the true proportion for small-to-moderate sample sizes. In addition, many of the best-performing of these intervals have not been directly compared with regard to the operational characteristics of coverage probability and empirical length. This study uses Monte Carlo simulations to calculate coverage probabilities and empirical lengths of five existing confidence intervals for clustered data across various true correlations, true probabilities of interest, and sample sizes. In addition, we introduce a new score-based confidence interval method, which we find to have better coverage than existing intervals for small sample sizes under a wide range of scenarios.

Current challenges in metabolomics for diabetes research: a vital functional genomic tool or just a ploy for gaining funding?

2008 ◽  
Vol 34 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Julian L. Griffin ◽  
Antonio Vidal-Puig
Keyword(s):  
Animal Studies ◽  
Gene Knockout ◽  
Tca Cycle ◽  
Small Sample ◽  
Human Populations ◽  
Diabetes Research ◽  
Functional Genomic ◽  
High Concentration ◽  
Small Sample Sizes ◽  
Analytical Tools

Metabolomics aims to profile all the small molecule metabolites found within a cell, tissue, organ, or organism and use this information to understand a biological manipulation such as a drug intervention or a gene knockout. While neither mass spectrometry or NMR spectroscopy, the two most commonly used analytical tools in metabolomics, can provide a complete coverage of the metabolome, compared with other functional genomic tools for profiling biological moieties the approach is cheap and high throughput. In diabetes and obesity research this has provided the opportunity to assess large human populations or investigate a range of different tissues in animal studies both rapidly and cheaply. However, the approach has a number of major challenges, particularly with the interpretation of the data obtained. For example, some key pathways are better represented by high concentration metabolites inside the cell, and thus, the coverage of the metabolome may become biased towards these pathways (e.g., the TCA cycle, amino acid metabolism). There is also the challenge of statistically modeling datasets with large numbers of variables but relatively small sample sizes. This perspective discusses our own experience of some of the benefits and pitfalls with using metabolomics to understand diseases associated with type 2 diabetes.

scholarly journals How to prove that your therapy is effective, even when it is not: a guideline

2015 ◽  
Vol 25 (5) ◽  
pp. 428-435 ◽  
Author(s):  
P. Cuijpers ◽  
I. A. Cristea
Keyword(s):  
Gold Standard ◽  
Treatment Guidelines ◽  
Randomised Trial ◽  
Small Sample ◽  
Risk Of Bias ◽  
Randomised Trials ◽  
Control Groups ◽  
Policy Makers ◽  
Small Sample Sizes ◽  
Positive Effect

Aims.Suppose you are the developer of a new therapy for a mental health problem or you have several years of experience working with such a therapy, and you would like to prove that it is effective. Randomised trials have become the gold standard to prove that interventions are effective, and they are used by treatment guidelines and policy makers to decide whether or not to adopt, implement or fund a therapy.Methods.You would want to do such a randomised trial to get your therapy disseminated, but in reality your clinical experience already showed you that the therapy works. How could you do a trial in order to optimise the chance of finding a positive effect?Results.Methods that can help include a strong allegiance towards the therapy, anything that increases expectations and hope in participants, making use of the weak spots of randomised trials (risk of bias), small sample sizes and waiting list control groups (but not comparisons with existing interventions). And if all that fails one can always not publish the outcomes and wait for positive trials.Conclusions.Several methods are available to help you show that your therapy is effective, even when it is not.

scholarly journals Effects of Ayahuasca on Personality: Results of Two Randomized, Placebo-Controlled Trials in Healthy Volunteers

2021 ◽  
Vol 12 ◽  
Author(s):  
Juliana Mendes Rocha ◽  
Giordano Novak Rossi ◽  
Flávia L. Osório ◽  
José Carlos Bouso Saiz ◽  
Gabriela De Oliveira Silveira ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Controlled Trial ◽  
Small Sample ◽  
Group Differences ◽  
Clinical Samples ◽  
Controlled Trials ◽  
Parallel Group ◽  
Neo Five Factor Inventory ◽  
Small Sample Sizes ◽  
Induced Changes

Rationale: Previous studies with the serotonergic hallucinogens LSD and psilocybin showed that these drugs induced changes in personality traits, such as increases in Openness. However, results are inconsistent, and the effects of ayahuasca on personality were never investigated in a controlled trial.Objectives: To assess the effects of ayahuasca on personality in two randomized, placebo-controlled trials in healthy volunteers.Methods: Data from two parallel-group, randomized, placebo-controlled trials in healthy volunteers were included. In the first trial, 15 volunteers ingested ayahuasca or placebo, while in the second trial 15 volunteers received placebo+ayahuasca or cannabidiol (CBD)+ayahuasca. Personality was assessed with the NEO-Five Factor Inventory (NEO-FFI) at baseline and 21 days post-treatment.Results: There were significant differences between groups in baseline Openness scores, but not on day 21. A significant increase in Openness scores was observed in the placebo + ayahuasca group in study 2. No other within-group differences were observed for any other domain.Conclusions: Ayahuasca produced inconsistent effects on personality since it induced significant increase in Openness 21 days post-drug intake only in one of the trials. The absence of significant differences in the other ayahuasca groups could be due to small sample sizes and baseline differences among groups. The effects of ayahuasca and other serotonergic hallucinogens on personality should be further investigated in clinical samples.

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