Pyruvate Kinase Deficiency in Sub-Saharan Africa: Identification of a Highly Frequent Missense Mutation (G829A;Glu277Lys) and Association with Malaria

Background

Pyruvate kinase (PK) deficiency, causing hemolytic anemia, has been associated to malaria protection and its prevalence in sub-Saharan Africa is not known so far. This work shows the results of a study undertaken to determine PK deficiency occurrence in some sub-Saharan African countries, as well as finding a prevalent PK variant underlying this deficiency.

Materials and Methods

Blood samples of individuals from four malaria endemic countries (Mozambique, Angola, Equatorial Guinea and Sao Tome and Principe) were analyzed in order to determine PK deficiency occurrence and detect any possible high frequent PK variant mutation. The association between this mutation and malaria was ascertained through association studies involving sample groups from individuals showing different malaria infection and outcome status.

Results

The percentage of individuals showing a reduced PK activity in Maputo was 4.1% and the missense mutation G829A (Glu277Lys) in the PKLR gene (only identified in three individuals worldwide to date) was identified in a high frequency. Heterozygous carrier frequency was between 6.7% and 2.6%. A significant association was not detected between either PK reduced activity or allele 829A frequency and malaria infection and outcome, although the variant was more frequent among individuals with uncomplicated malaria.

Conclusions

This was the first study on the occurrence of PK deficiency in several areas of Africa. A common PKLR mutation G829A (Glu277Lys) was identified. A global geographical co-distribution between malaria and high frequency of PK deficiency seems to occur suggesting that malaria may be a selective force raising the frequency of this 277Lys variant.     

Colonization of Abandoned Land by Juniperus thurifera Is Mediated by the Interaction of a Diverse Dispersal Assemblage and Environmental Heterogeneity

Land abandonment is one of the most powerful global change drivers in developed countries where recent rural exodus has been the norm. Abandonment of traditional land use practices has permitted the colonization of these areas by shrub and tree species. For fleshy fruited species the colonization of new areas is determined by the dispersal assemblage composition and abundance. In this study we showed how the relative contribution to the dispersal process by each animal species is modulated by the environmental heterogeneity and ecosystem structure. This complex interaction caused differential patterns on the seed dispersal in both, landscape patches in which the process of colonization is acting nowadays and mature woodlands of Juniperus thurifera, a relict tree distributed in the western Mediterranean Basin. Thrushes (Turdus spp) and carnivores (red fox and stone marten) dispersed a high amount of seeds while rabbits and sheeps only a tiny fraction. Thrushes dispersed a significant amount of seeds in new colonization areas, however they were limited by the presence of high perches with big crop size. While carnivores dispersed seeds to all studied habitats, even in those patches where no trees of J. thurifera were present, turning out to be critical for primary colonization. The presence of Pinus and Quercus was related to a reduced consumption of J. thurifera seeds while the presence of fleshy fruited shrubs was related with higher content of J. thurifera seeds in dispersers’ faeces. Therefore environmental heterogeneity and ecosystem structure had a great influence on dispersers feeding behaviour, and should be considered in order to accurately describe the role of seed dispersal in ecological process, such as regeneration and colonization. J. thurifera expansion is not seed limited thanks to its diverse dispersal community, hence the conservation of all dispersers in an ecosystem enhance ecosystems services and resilience.     

Structural characterization of the acetylated heteroxylan from the natural hybrid Paulownia elongata/Paulownia fortunei

The heteroxylan from the hybrid Paulownia elongata/Paulownia fortunei is an O-acetyl-(4-O-methylglucurono)xylan with an acetylation degree (DS) of 0.59 and a molecular weight (M(w)) of 29 kDa. The heteroxylan backbone is composed by (1-->4)-linked beta-d-xylopyranosyl units (Xylp) partially ramified with terminal (1-->2)-linked 4-O-methyl-alpha-D-glucuronosyl (MeGlcpA) and a small proportion of alpha-D-glucuronosyl (GlcpA) residues in a molar ratio of Xylp:(MeGlcpA+GlcpA) of 20:1. Roughly half of the beta-D-xylopyranosyl units in the backbone are acetylated: 3-O-acetylated (22 mol %), 2-O-acetylated (23 mol %) or 2,3-di-O-acetylated (7 mol %). ESI-MS and MALDI-MS studies of partially hydrolyzed heteroxylan revealed a random distribution of O-Ac and MeGlcpA within the backbone. However, the frequency of substitution with O-Ac along the backbone is not uniform and the molecular regions that did not contain MeGlcpA substituents possessed an acetylation degree significantly lower than the average DS of the xylan.     

Comparison between indirect enzyme-linked immunosorbent assays for Anaplasma marginale antibodies with recombinant major surface protein 5 and initial body antigens

Indirect enzyme-linked immunosorbent assays (ELISAs) based on recombinant major surface protein 5 (rMSP5) and initial body (IB) antigens from a Brazilian isolate of Anaplasma marginale were developed to detect antibodies against this rickettsia in cattle. Both tests showed the same sensitivity (98.2%) and specificities (100% for rMSP5 and 93.8% for IB ELISA) which did not differ statistically. No cross-reactions were detected with Babesia bigemina antibodies, but 5 (rMSP5 ELISA) to 15% (IB ELISA) of cross-reactions were detected with B. bovis antibodies. However, such difference was not statistically significant. Prevalences of seropositive crossbred beef cattle raised extensively in Miranda county, state of Mato Grosso do Sul, Brazil, were 78.1% by rMSP5 ELISA and 79.7% by IB ELISA. In the analysis of sera from dairy calves naturally-infected with A. marginale, the dynamics of antibody production was very similar between both tests, with maternal antibodies reaching the lowest levels at 15-30 days, followed by an increase in the mean optical densities in both ELISAs, suggesting the development of active immunity against A. marginale. Results showed that all calves were seropositive by one-year old, characterizing a situation of enzootic stability. The similar performances of the ELISAs suggest that both tests can be used in epidemiological surveys for detection of antibodies to A. marginale in cattle.     

Optimizing control programmes by integrating data from fine-scale space use by introduced predators

The control of introduced mammalian predators (IMP) through trapping campaigns relies on operator experience to deploy traps in sites with an expected high probability of IMP presence, where the maximum number of captures is anticipated. We tested the limitations of available information on fine-scale spatial use by feral cats modelled from remote data collection methods (small-resolution satellite imagery and GPS-telemetry) in an intensive control campaign conducted over 8 years in an ecologically sensitive area of New Zealand. We calculated dichotomous optimal/sub-optimal areas for cats and found that operators placed traps in or close to optimal areas. Over a continuous range of probabilities of cat use, trap sites were not principally placed in hot spots of cat use. Logistic regression revealed that the probability of cat use was significantly associated with the probability of capture. However, regressing catch-effort against the probability of cat use showed no association between sites of high probability of cat use and higher capture rates. The incorporation in the models of bait, trap type, and habitat suitability for rabbits, as variables of operator’s choice showed that rabbit suitability, and the combination of baits/traps were significant. Results suggest that trapping feral cats is a complex process that likely relies on variables of space, time, and individual cognition. However, control programmes could improve trap deployment by identifying sites of high probability of cat use to maximize capture probability, while traps in sub-optimal areas could be removed (cost reduction), reallocated to optimal areas, or used to “fence” core conservation areas.     

Relative value of riparian woodlands in landscapes with different forest cover for medium-sized Iberian carnivores

This study analyses the role of riparian woodland in the conservation of five common carnivore species as compared with other non-riparian habitats according to woodland cover on the landscape scale (>60, 20–35 and <15% on 20 × 20-km surface area). I hypothesised that the importance of riparian woodlands in carnivore conservation on the regional scale would be greater in landscapes with low forest cover than in those with intermediate or high forest cover. To test this hypothesis, in each landscape type I sampled five riparian forests and 10–15 non-riparian habitats and recorded species richness and frequency of occurrence (number of sampled sites with species presence/total sampled sites) in both habitat types. The presence of (or use by) species at each particular sampling site was recorded using sign-surveys (search for scats and badger dens). The relative importance of riparian and non-riparian habitats in each landscape type was analysed by comparing species richness and frequency of occurrence for each species. Comparison of species richness and frequency of occurrence between landscape types indicate that riparian woodlands are important habitats in all landscape contexts. However, in accordance with the initial hypothesis, riparian woodlands are essential for carnivore conservation in the most deforested areas. Any agricultural or development policy should take into account the need to maintain and preserve riparian woodlands in landscapes, especially in intensively cultivated landscapes.     

Hyperaluminemia and parathormone release

Previous studies have shown that aluminum (Al) could inhibit parathyroid function. However, controversy still remains about the possible mechanisms implicated. Thus, the aim of this study was to evaluate the acute parathyroid hormone (PTH) response to intravenous Al infusion. Male Wistar rats were divided into two groups: Group A (n = 5): received 0.1 ml of saline. Group B (n = 5): received 0.5 mg of Cl3Al in 0.1 ml of saline. In both groups ionized calcium (Ca(+)+) decreased, but despite a similar degree of haemodilution, this change was only significant in group A. This variable Ca(+)+ decrease was followed by different responses in the PTH secretion. In group B there was a significantly (p less than 0.05) lower PTH release compared with control group. These results suggest that Al could directly inhibit the PTH secretion, and at the same time might exert an indirect effect on PTH release "blunting" the serum Ca(+)+ variations.     

Respiratory allergy to Blomia tropicalis: Immune response in four syngeneic mouse strains and assessment of a low allergen-dose,short-term experimental model

Background

The dust mite Blomia tropicalis is an important source of aeroallergens in tropical areas. Although a mouse model for B. tropicalis extract (BtE)-induced asthma has been described, no study comparing different mouse strains in this asthma model has been reported. The relevance and reproducibility of experimental animal models of allergy depends on the genetic background of the animal, the molecular composition of the allergen and the experimental protocol.

Objectives

This work had two objectives. The first was to study the anti-B. tropicalis allergic responses in different mouse strains using a short-term model of respiratory allergy to BtE. This study included the comparison of the allergic responses elicited by BtE with those elicited by ovalbumin in mice of the strain that responded better to BtE sensitization. The second objective was to investigate whether the best responder mouse strain could be used in an experimental model of allergy employing relatively low BtE doses.

Methods

Groups of mice of four different syngeneic strains were sensitized subcutaneously with 100 μg of BtE on days 0 and 7 and challenged four times intranasally, at days 8, 10, 12, and 14, with 10 μg of BtE. A/J mice, that were the best responders to BtE sensitization, were used to compare the B. tropicalis-specific asthma experimental model with the conventional experimental model of ovalbumin (OVA)-specific asthma. A/J mice were also sensitized with a lower dose of BtE.

Results

Mice of all strains had lung inflammatory-cell infiltration and increased levels of anti-BtE IgE antibodies, but these responses were significantly more intense in A/J mice than in CBA/J, BALB/c or C57BL/6J mice. Immunization of A/J mice with BtE induced a more intense airway eosinophil influx, higher levels of total IgE, similar airway hyperreactivity to methacholine but less intense mucous production, and lower levels of specific IgE, IgG1 and IgG2 antibodies than sensitization with OVA. Finally, immunization with a relatively low BtE dose (10 μg per subcutaneous injection per mouse) was able to sensitize A/J mice, which were the best responders to high-dose BtE immunization, for the development of allergy-associated immune and lung inflammatory responses.

Conclusions

The described short-term model of BtE-induced allergic lung disease is reproducible in different syngeneic mouse strains, and mice of the A/J strain was the most responsive to it. In addition, it was shown that OVA and BtE induce quantitatively different immune responses in A/J mice and that the experimental model can be set up with low amounts of BtE.