Aspects of the maintenance of the life cycle of Fasciola hepatica in Lymnaea columella in Minas Gerais,Brazil

Fascioliasis is a parasitic disease of domestic ruminants that occurs worldwide. The lymnaeid intermediate hosts of Fasciola hepatica include Lymnaea columella, which is widely distributed in Brazil. A colony of L. columella from Belo Horizonte, MG, was reared in our laboratory to be used in studies of the F. hepatica life cycle, the intermediate host-parasite relationship and development of an anti-helminthic vaccine. In the first experiment 1,180 snails were exposed to miracidia of F. hepatica eggs removed from the biliary tracts of cattle from the State of Rio Grande do Sul. In the second and third experiments the snails were exposed to miracidia that had emerged from F. hepatica eggs from Uruguay, maintained in rabbits. The rates of infection in the first, second and third experiments were 0, 42.1 and 0% respectively. Over 15,806 metacercariae were obtained and stored at 4 degrees C. Four rabbits weighing 1.5 kg each were infected with 32-44 metacercariae and two with 200. Three rabbits begin to eliminate eggs of the parasite in the feces from 84 days after infection onwards. The biological cycle of F. hepatica in L. columella and the rabbit was completed within 124 days.     

Phene Synergism between Root Hair Length and Basal Root Growth Angle for Phosphorus Acquisition

Shallow basal root growth angle (BRGA) increases phosphorus acquisition efficiency by enhancing topsoil foraging because in most soils, phosphorus is concentrated in the topsoil. Root hair length and density (RHL/D) increase phosphorus acquisition by expanding the soil volume subject to phosphorus depletion through diffusion. We hypothesized that shallow BRGA and large RHL/D are synergetic for phosphorus acquisition, meaning that their combined effect is greater than the sum of their individual effects. To evaluate this hypothesis, phosphorus acquisition in the field in Mozambique was compared among recombinant inbred lines of common bean (Phaseolus vulgaris) having four distinct root phenotypes: long root hairs and shallow basal roots, long root hairs and deep basal roots, short root hairs and shallow basal roots, and short root hairs and deep basal roots. The results revealed substantial synergism between BRGA and RHL/D. Compared with short-haired, deep-rooted phenotypes, long root hairs increased shoot biomass under phosphorus stress by 89%, while shallow roots increased shoot biomass by 58%. Genotypes with both long root hairs and shallow roots had 298% greater biomass accumulation than short-haired, deep-rooted phenotypes. Therefore, the utility of shallow basal roots and long root hairs for phosphorus acquisition in combination is twice as large as their additive effects. We conclude that the anatomical phene of long, dense root hairs and the architectural phene of shallower basal root growth are synergetic for phosphorus acquisition. Phene synergism may be common in plant biology and can have substantial importance for plant fitness, as shown here.Suboptimal phosphorus availability is a primary limitation to plant growth in terrestrial ecosystems (Vance et al., 2003). Large areas of tropical and subtropical soils in Africa, Latin America, and Asia have phosphorus availability limited by low total phosphorus content as well as high phosphorus fixation (Sanchez and Uehara, 1980). The use of phosphorus fertilizer to correct phosphorus deficiency is only a partial solution, since phosphorus fertilizers are costly, nonrenewable, potentially harmful to the environment, and often marginally effective in tropical soils because of immobilization by the soil (Cathcart, 1980). Therefore, the development of crop cultivars with enhanced ability to acquire phosphorus is an important strategy to increase agricultural productivity in low-input agroecosystems and to reduce input requirements in intensive agriculture (Vance et al., 2003; Gahoonia and Nielsen, 2004; Lambers et al., 2006; Lynch, 2007, 2011).Several root phenes (i.e. basic units of the phenotype; Serebrovsky, 1925; Lynch, 2011; for discussion, see York et al., 2013) enhance phosphorus acquisition, including root architectural phenes for topsoil foraging (Lynch and Brown, 2001), such as shallow root growth angles (Liao et al., 2004; Ho et al., 2005), increased basal root whorl number (Lynch and Brown, 2012; Miguel et al., 2013), and adventitious rooting (Miller et al., 2003); phenes to enhance soil exploitation, including root hair length and density (RHL/D; Bates and Lynch, 2000a, 2000b, 2001; Ma et al., 2001a; Gahoonia and Nielsen, 2004; Yan et al., 2004) and phosphorus-solubilizing root exudates (Ryan et al., 2001); mycorrhizal symbioses (Smith and Read, 2008); and phenes that reduce the metabolic cost of soil exploration (Lynch and Ho, 2005), such as root etiolation and root cortical aerenchyma (Fan et al., 2003; Postma and Lynch, 2010, 2011). It is probable that interactions among these phenes are important in determining the phosphorus acquisition of integrated phenotypes. Results from the structural-functional model SimRoot indicate that RHL/D, the distance from the root tip to the first appearance of root hairs, and the pattern of root hair-bearing epidermal cells (trichoblasts) among non-hair-bearing cells (atrichoblasts) are synergetic for phosphorus acquisition in Arabidopsis (Arabidopsis thaliana; Ma et al., 2001b). Another SimRoot study showed that on low-phosphorus soils, the utility of root cortical aerenchyma in maize (Zea mays) may be 2.9 times greater in plants with increased lateral branching density than in plants with normal branching (Postma and Lynch, 2011). Morphological, anatomical, symbiotic, and biochemical phenes expressed by root axes should have significant synergies with architectural phenes, since architectural phenes determine the position of root axes in time and space and, therefore, the soil domain in which spatially localized phenes are expressed (Lynch, 2011).Phosphorus availability is greater in the topsoil, with a steep decline with depth. Therefore, root architectural phenes that increase topsoil foraging can improve phosphorus acquisition (Lynch and Brown, 2001). Root shallowness regulated by basal root growth angle (BRGA) has been demonstrated to be of particular importance for topsoil foraging (Bonser et al., 1996; Liao et al., 2001; Rubio et al., 2001; Ho et al., 2005). These studies show that common bean (Phaseolus vulgaris) genotypes with smaller BRGA (i.e. shallower roots) have better performance in low-phosphorus soils. Shallow root distribution is also important for phosphorus acquisition in maize (Zhu et al., 2005).RHL/D are also important for phosphorus acquisition (Bates and Lynch, 2000a, 2000b, 2001; Gahoonia and Nielsen, 2004). Since phosphorus mobility in soil is governed by diffusion rather than mass flow, phosphorus uptake by roots is limited by localized phosphorus depletion in the rhizosphere (Barber, 1995). Long root hairs extend the phosphorus depletion zone surrounding the root, thereby increasing the total amount of phosphorus accessible by the roots and phosphorus acquisition. In many plant species, the length and density of root hairs increase in response to low phosphorus availability (Bates and Lynch, 1996; Ma et al., 2001a). Increased RHL/D increases phosphorus accumulation in Arabidopsis growing in low-phosphorus conditions (Bates and Lynch, 2000a, 2000b), and mutants lacking root hairs have reduced phosphorus acquisition (Bates and Lynch, 2000b; Gahoonia et al., 2001). Species that develop more and/or longer root hairs (e.g. Lolium perenne) are more efficient in accessing inorganic phosphorus from soils and thus show greater growth response to phosphorus fertilization than species that lack these traits (e.g. Podocarpus totara). Genotypic variation for root hairs is associated with increased phosphorus acquisition in several species, including barley (Hordeum vulgare; Gahoonia and Nielsen, 2004), common bean (Miguel, 2004; Yan et al., 2004), and maize (Zhu et al., 2010).We hypothesize that the utilities of BRGA and RHL/D for phosphorus acquisition are synergetic. Root hairs will be more valuable for phosphorus acquisition if located in surface soil horizons by arising from roots with a shallow growth angle; shallow roots will have greater benefit for phosphorus acquisition if they have long and dense hairs. Therefore, genotypes possessing long, dense root hairs on shallow roots should have greater phosphorus acquisition than genotypes with either long root hairs on deep roots or short root hairs on shallow roots. We expect the combined benefit of long root hairs and shallow root growth angles to exceed the sum of their individual effects, since they permit greater exploitation of soil strata with the greatest phosphorus availability.In this study, we evaluated the potential synergism between the architectural phene of BRGA and the morphological phene of RHL/D for phosphorus acquisition by comparison of contrasting phenotypes of common bean growing in a weathered tropical soil.     

Structure and absolute configuration of the sesquiterpenoid emmotins

The trunk wood of Emmotum nitens (Icacinaceae) contains the aromatic sesquiterpenes (2R,3S)-2-hydroxy-3-(2′-hydroxyisopropyl)-5,8-dimethyl-1-oxo-1,2,3,4-tetrahydronaphthalene (emotin-F), 2-hydroxy-3-(2′-hydroxyisopropyl)-5,8-dimethylnaphthalene (emmotin-G) and 3-(2′-hydroxyisopropyl)-5,8-dimethyl-1,2-naphtho-quinone (emmotin-H). The identity of the carbon skeletons of these emmotins was proved by conversion of all three into an identical quinoxaline derivative. The nature of this skeleton and the absolute configuration of emmotin-F, as well as of the previously described emmotins A and B, was established by conversion of emmotin-F into (+)-occidol.     

Nitric oxide affecting root growth,lignification and related enzymes in soybean seedlings

This study analyzed the involvement of nitric oxide (NO) in the root lignification of soybean seedlings. To this end, changes in root cell viability; phenylalanine ammonia-lyase (PAL) and soluble and cell wall bound peroxidase (POD) activities and lignin and hydrogen peroxide (H₂O₂) contents of soybean roots treated with the NO-donor sodium nitroprusside (SNP) and its relationships with root growth were evaluated. Seedlings were cultivated in a nutrient solution supplemented with 5 to 1,000 μM SNP for 24 h. At an extremely low concentration (5 μM), SNP induced root growth and increased lignification and activities of related enzymes (PAL and cell wall-bound POD). At a high concentration (1,000 μM), SNP reduced root growth and lignification (PAL activity and H₂O₂ and lignin contents) and caused a loss of cell viability. Application of potassium ferrocyanide (an analog of SNP that cannot release NO) and PTIO (2-phenyl-4,4,5,5,-tetramethylimidazoleline-1-oxyl-3-oxide, a scavenger of NO) revealed that the inhibitory/stimulatory effects on root lignification may be due to NO itself. These results indicate that NO, depending on its concentration, may act as a stress factor, due to its toxic action, or as a signal molecule, inducing soybean root growth and lignification.     

Cell resilience in species life spans: a link to inflammation?

Species differences in life span have been attributed to cellular survival during various stressors, designated here as ‘cell resilience’. In primary fibroblast cultures, cell resilience during exposure to free radicals, hypoglycemia, hyperthermia, and various toxins has shown generally consistent correlations with the species characteristic life spans of birds and mammals. However, the mechanistic links of cell resilience in fibroblast cultures to different species life spans are poorly understood. We propose that certain experimental stressors are relevant to somatic damage in vivo during inflammatory responses of innate immunity, particularly, resistance to reactive oxygen species (ROS), low glucose, and hyperthermia. According to this hypothesis, somatic cell resilience determines species differences in longevity during repeated infections and traumatic injuries in the natural environment. Infections and injury expose local fibroblasts and other cells to ROS generated by macrophages and to local temperature elevations. Systemically, acute phase immune reactions cause hypoglycemia and hyperthermia. We propose that cell resilience to somatic stressors incurred in inflammation is important in the evolution of longevity and that longer‐lived species are specifically more resistant to immune‐related stressors. This hypothesis further specifies Kirkwood’s disposable soma theory. We suggest expanding the battery of stressors and markers used for comparative studies to additional cell types and additional parameters relevant to host defense and to their ecological specificities.     

Predictive vs. Empiric Assessment of Schistosomiasis: Implications for Treatment Projections in Ghana

BackgroundMapping the distribution of schistosomiasis is essential to determine where control programs should operate, but because it is impractical to assess infection prevalence in every potentially endemic community, model-based geostatistics (MBG) is increasingly being used to predict prevalence and determine intervention strategies.Conclusions/SignificanceUsing the current predictive map for Ghana as a spatial decision support tool by aggregating prevalence estimates to the district level was clearly not adequate for guiding the national program, but the alternative of assessing each school in potentially endemic areas of Ghana or elsewhere is not at all feasible; modelling must be a tool complementary to empiric assessments. Thus for practical usefulness, predictive risk mapping should not be thought of as a one-time exercise but must, as in the current study, be an iterative process that incorporates empiric testing and model refining to create updated versions that meet the needs of disease control operational managers.     

Spatiotemporal Patterns of Japanese Encephalitis in China, 2002–2010

Objective

The aim of the study is to examine the spatiotemporal pattern of Japanese Encephalitis (JE) in mainland China during 2002–2010. Specific objectives of the study were to quantify the temporal variation in incidence of JE cases, to determine if clustering of JE cases exists, to detect high risk spatiotemporal clusters of JE cases and to provide evidence-based preventive suggestions to relevant stakeholders.

Methods

Monthly JE cases at the county level in mainland China during 2002–2010 were obtained from the China Information System for Diseases Control and Prevention (CISDCP). For the purpose of the analysis, JE case counts for nine years were aggregated into four temporal periods (2002; 2003–2005; 2006; and 2007–2010). Local Indicators of Spatial Association and spatial scan statistics were performed to detect and evaluate local high risk space-time clusters.

Results

JE incidence showed a decreasing trend from 2002 to 2005 but peaked in 2006, then fluctuated over the study period. Spatial cluster analysis detected high value clusters, mainly located in Southwestern China. Similarly, we identified a primary spatiotemporal cluster of JE in Southwestern China between July and August, with the geographical range of JE transmission increasing over the past years.

Conclusion

JE in China is geographically clustered and its spatial extent dynamically changed during the last nine years in mainland China. This indicates that risk factors for JE infection are likely to be spatially heterogeneous. The results may assist national and local health authorities in the development/refinement of a better preventive strategy and increase the effectiveness of public health interventions against JE transmission.     

Incomplete transfer of accessory loci influencing SbMATE expression underlies genetic background effects for aluminum tolerance in sorghum

Impaired root development caused by aluminum (Al) toxicity is a major cause of grain yield reduction in crops cultivated on acid soils, which are widespread worldwide. In sorghum, the major Al‐tolerance locus, Alt_SB, is due to the function of SbMATE, which is an Al‐activated root citrate transporter. Here we performed a molecular and physiological characterization of various Alt_SB donors and near‐isogenic lines harboring various Alt_SB alleles. We observed a partial transfer of Al tolerance from the parents to the near‐isogenic lines that was consistent across donor alleles, emphasizing the occurrence of strong genetic background effects related to Alt_SB. This reduction in tolerance was variable, with a 20% reduction being observed when highly Al‐tolerant lines were the Alt_SB donors, and a reduction as great as 70% when other Alt_SB alleles were introgressed. This reduction in Al tolerance was closely correlated with a reduction in SbMATE expression in near‐isogenic lines, suggesting incomplete transfer of loci acting in trans on SbMATE. Nevertheless, Alt_SB alleles from the highly Al‐tolerant sources SC283 and SC566 were found to retain high SbMATE expression, presumably via elements present within or near the Alt_SB locus, resulting in significant transfer of the Al‐tolerance phenotype to the derived near‐isogenic lines. Allelic effects could not be explained by coding region polymorphisms, although occasional mutations may affect Al tolerance. Finally, we report on the extensive occurrence of alternative splicing for SbMATE, which may be an important component regulating SbMATE expression in sorghum by means of the nonsense‐mediated RNA decay pathway.