Heritability of P. falciparum and P. vivax Malaria in a Karen Population in Thailand

The majority of studies concerning malaria host genetics have focused on individual genes that confer protection against rather than susceptibility to malaria. Establishing the relative impact of genetic versus non-genetic factors on malaria infection and disease is essential to focus effort on key determinant factors. This relative contribution has rarely been evaluated for Plasmodium falciparum and almost never for Plasmodium vivax. We conducted a longitudinal cohort study in a Karen population of 3,484 individuals in a region of mesoendemic malaria, Thailand from 1998 to 2005. The number of P. falciparum and P. vivax clinical cases and the parasite density per person were determined. Statistical analyses were performed to account for the influence of environmental factors and the genetic heritability of the phenotypes was calculated using the pedigree-based variance components model. The genetic contribution to the number of clinical episodes resulting from P. falciparum and P. vivax were 10% and 19% respectively. There was also moderate genetic contribution to the maximum and overall parasite trophozoite density phenotypes for both P. falciparum (16%&16%) and P. vivax (15%&13%). These values, for P. falciparum, were similar to those previously observed in a region of much higher transmission intensity in Senegal, West Africa. Although environmental factors play an important role in acquiring an infection, genetics plays a determinant role in the outcome of an infection with either malaria parasite species prior to the development of immunity

Hydrogen recycling during RF plasma heating in the U-3M torsatron

The hydrogen recycling behavior has been studied during the plasma experiments in torsatron U-3M. For this purpose, the time dependence of the molecular hydrogen pressure in the U-3M torsatron vacuum chamber in the modes of RF wall conditioning and RF plasma heating has been measured. The experimental results show that the hydrogen pumping from the vacuum chamber runs at constant rate during the RF discharge for each mode. After RF power switching-off the inverse desorption of hydrogen, accumulated during the RF discharge in the vacuum chamber walls and helical coil surfaces, is observed. When the antenna anode voltages and the RF pulse duration in both modes are increasing, the character of the time dependences of hydrogen pressure does not change significantly.Изучено поведение рециклинга водорода во время плазменных экспериментов на торсатроне У-3М. Для этой цели было проведено измерение временных зависимостей давления водорода в вакуумной камере торсатрона У-3М в режимах ВЧ-чистки стенок камеры и ВЧ-нагрева плазмы. Экспериментальные результаты показали, что в обоих режимах во время ВЧ-разряда скорость откачки водорода из вакуумной камеры остается постоянной для каждого из режимов. После выключения ВЧ-мощности наблюдается обратная десорбция водорода, накопленного во время ВЧ-разряда в стенках вакуумной камеры и винтовых катушек. Повышение анодных напряжений на ВЧ-антеннах и увеличение длительности ВЧ-импульса существенно не влияют на характер временных зависимостей давления водорода.Вивчено поведінку рециклінгу водню під час плазмових експериментів на торсатроні У-3М. Для цієї мети було проведено вимірювання часових залежностей тиску водню у вакуумній камері торсатрона У-3М в режимах ВЧ-чистки стінок камери і ВЧ-нагріву плазми. Експериментальні результати показали, що в обох режимах під час ВЧ-розряду швидкість відкачування водню з вакуумної камери залишається постійною для кожного з режимів. Після виключення ВЧ-потужності спостерігається зворотна десорбція водню, накопиченого під час ВЧ-розряду в стінках вакуумної камери і гвинтових котушок. Підвищення анодних напруг на ВЧ-антенах і збільшення тривалості ВЧ-імпульсу істотно не впливають на характер тимчасових залежностей тиску водню

Contribution (%) of genetic (heritability, h²) and house (c²) effects to variability in malaria and non-malaria clinical and biological phenotypes of <i>P. falciparum</i> (Pf) and <i>P. vivax</i> (Pv).

<p>h², variance due to genetics, c², variance due to house effect, S.E. the standard error; NS, not significant (<i>p-value</i>>0.05); NE, not estimated.</p>a<p>Retained because of marginal significance.</p

Summary of samples used in epidemiological and genetic analyses.

<p>For epidemiological analyses, presented are the number of data points (observations and calculated mean/max values) analyzed for each phenotype category, the corresponding number of individuals implicated and hence residual values generated. For genetic analyses, presented are the number of these individuals for whom pedigree information was available and thus the number of independent families and relative pairs count for each phenotype in the heritability analyses. In parentheses, the number belonging to the large complex family.</p

Pair-wise correlation between phenotypes studied.

<p>PFA, Number of visits Pf+; NMF, Number of non-malaria fever visits; PVA, Number of visits Pv+; mx-PFD, Pf max parasite density; PFD, Overall Pf parasite densities; mx-PVD, Pv max parasite density; PVD, Overall Pv parasite densities. In bold, highly significant p value (≤10⁻⁴); in italic, significant p value that becomes not significant after Bonferroni correction for multiple testing (21 hypotheses tested).</p

Number of pairs of individuals as defined by genetic relationship (phi2) and household relationship.

<p>Number of pairs of individuals as defined by genetic relationship (phi2) and household relationship.</p

Family statistics.

<p>Family statistics.</p

Proportions of variation explained by genetic heritability, house and environmental factors found to have a significant effect on the phenotype measured (Table 3&6).

<p>(A) Number of clinical episodes of <i>P. falciparum</i> (PFA); (B) Number of clinical episodes of <i>P. vivax</i> (PVA); (C) Number of non-malaria clinical episodes (NMF); (D) Maximum <i>P. falciparum</i> parasite density (mx-PFD); (E) Overall <i>P. falciparum</i> parasite density (PFD); (F) Maximum <i>P. vivax</i> parasite density (mx-PVD); (G) Overall <i>P. vivax</i> parasite density (PVD). Values of 1% or less not indicated numerically in the figure.</p

Percentage of variation in <i>P. falciparum</i> (Pf) and <i>P. vivax</i> (Pv) phenotypes explained by environmental factors (and their interactions) in the statistical analyses.

<p>In parentheses, <i>p</i> is the <i>p-value</i>; in bold, <i>p-value</i><10⁻³.</p>a<p>Retained because of significant interaction with Age.</p