Coexistence of helminth species in Lysapsus limellus (Anura: Pseudidae) from an Argentinean subtropical area: influence of biotic and abiotic factors

The need for studies on helminth communities of South American amphibians was addressed by examining changes in composition and population dynamics of the helminth component and infracommunities in the frog Lysapsus limellus Cope, 1862, from 1994 to 1996. Two pond types were considered, one permanent and one semipermanent. The main goals of this study were (1) to investigate the relationships between pond type, season, study time, frog body size, and frog sex and the presence-absence and counts of helminth parasite species in the frog host, L. limellus, and (2) to examine the co-occurrence of the different parasite species in the frog host in terms of the structure, assembly, and dynamics of the helminth infracommunity. Parasite presence and absence were analyzed using logistic regression and parasite counts were analyzed using log-linear modeling. To examine the association between parasite species, a principal components analysis was carried out on the correlation matrix for the counts. The pattern of co-occurrences was also examined through a randomization test. The main results were as follows: (1) five parasite species were found in the infracommunity; (2) the pond type and the host size class were the principal factors related to the presence and absence of parasites for the three dominant species, while the year of study and the host sex were only important for one of the species; (3) for the parasite counts, many more factors were significant, with body size class and pond type always important factors for the three core species of the infracommunity, with season, year of study, and sex also sometimes important, and (4) strong associations were observed between some helminth species of the host from the permanent pond, but the same species did not co-occur in frogs in the semipermanent pond. The life histories of the five species can be considered as opportunistic or "r strategists."     

The association between familial distal renal tubular acidosis and mutations in the red cell anion exchanger (band 3, AE1) gene.

In distal renal tubular acidosis (dRTA) the tubular secretion of hydrogen ion in the distal nephron is impaired, leading to the development of metabolic acidosis, frequently accompanied by hypokalemia, nephrocalcinosis, and metabolic bone disease. The condition can be familial, when it is usually inherited as an autosomal dominant, though there is a rarer autosomal recessive form associated with nerve deafness. It has been shown that the autosomal dominant form of dRTA is associated with a defect in the anion exchanger (AE1) of the renal collecting duct intercalated cell. This transporter is a product of the same gene (AE1) as the erythrocyte anion exchanger, band 3. In this review we will look at the evidence for this association. Studies of genomic DNA from families with this disorder have shown, both by genetic linkage studies and by DNA sequencing, that affected individuals are heterozygous for mutations in the AE1 gene whilst unaffected family members have a normal band 3 sequence. Mutations have been found in the region of proposed helices 6 and 7 of the membrane domain of band 3 and involve amino acids Arg-589 and Ser-613, and in the COOH-terminal domain of band 3. Studies of red cell band 3 from these families have provided information on the effect these mutations have on the structure and function of erythrocyte band 3. Expression studies of the erythroid and kidney isoforms of the mutant AE1 proteins, in Xenopus laevis oocytes, have shown that they retained chloride transport activity, suggesting that the disease in the dRTA families is not related simply to the anion transport activity of the mutated proteins. A possible explanation for the dominant effect of these mutant AE1 proteins in the kidney cell is that these mutations affect the targeting of AE1 from the basolateral to the apical membrane of the alpha-intercalated cell.     

Effective Coverage and Systems Effectiveness for Malaria Case Management in Sub-Saharan African Countries

Scale-up of malaria preventive and control interventions over the last decade resulted in substantial declines in mortality and morbidity from the disease in sub-Saharan Africa and many other parts of the world. Sustaining these gains will depend on the health system performance. Treatment provides individual benefits by curing infection and preventing progression to severe disease as well as community-level benefits by reducing the infectious reservoir and averting emergence and spread of drug resistance. However many patients with malaria do not access care, providers do not comply with treatment guidelines, and hence, patients do not necessarily receive the correct regimen. Even when the correct regimen is administered some patients will not adhere and others will be treated with counterfeit or substandard medication leading to treatment failures and spread of drug resistance. We apply systems effectiveness concepts that explicitly consider implications of health system factors such as treatment seeking, provider compliance, adherence, and quality of medication to estimate treatment outcomes for malaria case management. We compile data for these indicators to derive estimates of effective coverage for 43 high-burden Sub-Saharan African countries. Parameters are populated from the Demographic and Health Surveys and other published sources. We assess the relative importance of these factors on the level of effective coverage and consider variation in these health systems indicators across countries. Our findings suggest that effective coverage for malaria case management ranges from 8% to 72% in the region. Different factors account for health system inefficiencies in different countries. Significant losses in effectiveness of treatment are estimated in all countries. The patterns of inter-country variation suggest that these are system failures that are amenable to change. Identifying the reasons for the poor health system performance and intervening to tackle them become key priority areas for malaria control and elimination policies in the region.     

Effect of Roadside Vegetation Cutting on Moose Browsing

Moose (Alces americanus ) vehicle collisions (MVCs) are an issue throughout the distribution of moose. Many mitigation strategies have been tested and implemented to reduce the number of MVCs, but there have been few empirical analyses of the effectiveness of roadside vegetation cutting. The goal of this study was to determine if roadside vegetation cutting attracted moose into roadside areas to browse on the vegetation regrowth. We hypothesized that moose would be attracted to roadside areas with cut vegetation. Consequently, we predicted that there would be higher levels of browsing in cut areas compared to uncut areas. To determine if moose were browsing more in cut or uncut areas, we measured the number of plants browsed by moose in paired treatment (cut on or after 2008) and control (not cut since at least 2008) sites, along with a suite of potential environmental covariates. Using a model selection approach, we fit generalized linear mixed-effects models to determine the most parsimonious set of environmental variables to explain variation in the proportion of moose browse among sites. In contrast to our hypothesis, our results show that the proportion of moose browse in the uncut control areas was significantly higher than in the cut treatment areas. The results of this study suggest that recently cut roadside areas (7 years or less based on our work) may create a less attractive foraging habitat for moose. The majority of the variance in the proportion of moose browse among sites was explained by treatment type and nested plot number within site identification (34.16%), with additional variance explained by traffic region (5.00%) and moose density (4.35%). Based on our study, we recommend that vegetation cutting be continued in roadside areas in Newfoundland as recently cut areas may be less attractive browsing sites for moose.     

Anti-Inflammatory Effects of IL-27 in Zymosan-Induced Peritonitis: Inhibition of Neutrophil Recruitment Partially Explained by Impaired Mobilization from Bone Marrow and Reduced Chemokine Levels

Rapid activation of the innate immune system is critical for an efficient host response to invading pathogens. However, the inflammatory reaction has to be strictly controlled to minimize harmful immunopathology. A number of mediators including the cytokine interleukin-27 (IL-27) appear to be responsible for limitation and resolution of inflammation. Despite increasing knowledge of its suppressive effects on T cells, the influence on neutrophils and macrophages is poorly understood. To determine the role of IL-27 in innate immune responses we analysed the effect of IL-27 in a T cell independent model of zymosan-induced peritonitis. Early administration of recombinant IL-27 strongly reduced the number of neutrophils recruited to the peritoneal cavity after zymosan application as well as the neutrophil frequency in the blood. Simultaneously, IL-27 reduced the release of neutrophils from the bone marrow upon inflammation. Although cytokine levels were not affected by IL-27 treatment, the levels of the chemokines KC, MCP-1 and MIP-1α in the peritoneal fluid were strongly decreased. These findings demonstrate that IL-27 is able to control mobilisation and recruitment of neutrophils into the peritoneal cavity and identify a novel mechanism to limit inflammation caused by innate immune cells.     

Acute Dietary Nitrate Supplementation and Exercise Performance in COPD: A Double-Blind,Placebo-Controlled,Randomised Controlled Pilot Study

Background

Dietary nitrate supplementation can enhance exercise performance in healthy people, but it is not clear if it is beneficial in COPD. We investigated the hypotheses that acute nitrate dosing would improve exercise performance and reduce the oxygen cost of submaximal exercise in people with COPD.

Methods

We performed a double-blind, placebo-controlled, cross-over single dose study. Subjects were randomised to consume either nitrate-rich beetroot juice (containing 12.9mmoles nitrate) or placebo (nitrate-depleted beetroot juice) 3 hours prior to endurance cycle ergometry, performed at 70% of maximal workload assessed by a prior incremental exercise test. After a minimum washout period of 7 days the protocol was repeated with the crossover beverage.

Results

21 subjects successfully completed the study (age 68±7years; BMI 25.2±5.5kg/m²; FEV₁ percentage predicted 50.1±21.6%; peak VO₂ 18.0±5.9ml/min/kg). Resting diastolic blood pressure fell significantly with nitrate supplementation compared to placebo (-7±8mmHg nitrate vs. -1±8mmHg placebo; p = 0.008). Median endurance time did not differ significantly; nitrate 5.65 (3.90–10.40) minutes vs. placebo 6.40 (4.01–9.67) minutes (p = 0.50). However, isotime oxygen consumption (VO₂) was lower following nitrate supplementation (16.6±6.0ml/min/kg nitrate vs. 17.2±6.0ml/min/kg placebo; p = 0.043), and consequently nitrate supplementation caused a significant lowering of the amplitude of the VO₂-percentage isotime curve.

Conclusions

Acute administration of oral nitrate did not enhance endurance exercise performance; however the observation that beetroot juice caused reduced oxygen consumption at isotime suggests that further investigation of this treatment approach is warranted, perhaps targeting a more hypoxic phenotype.

Trial Registration

ISRCTN Registry ISRCTN66099139     

Erratum to “Helminth communities in the burrowing toad, Rhinella fernandezae, from Northeastern Argentina” by Monika Inés Hamann, Arturo Ignacio Kehr & Cynthya Elizabeth González

The original version of the article was published in Biologia 68 (6): 1155–1163 (2013), DOI: 10.2478/s11756-013-0272-5. Unfortunately, the original version of this article contains a mistake in Table 1 and in left collumn, line 8 on page 1157. Here we display the corrected version of the table and text.     

The PhoU Protein from Escherichia coli Interacts with PhoR,PstB, and Metals To Form a Phosphate-Signaling Complex at the Membrane

Robust growth in many bacteria is dependent upon proper regulation of the adaptive response to phosphate (P_i) limitation. This response enables cells to acquire P_i with high affinity and utilize alternate phosphorous sources. The molecular mechanisms of P_i signal transduction are not completely understood. PhoU, along with the high-affinity, P_i-specific ATP-binding cassette transporter PstSCAB and the two-component proteins PhoR and PhoB, is absolutely required for P_i signaling in Escherichia coli. Little is known about the role of PhoU and its function in regulation. We have demonstrated using bacterial two-hybrid analysis and confirmatory coelution experiments that PhoU interacts with PhoR through its PAS (Per-ARNT-Sim) domain and that it also interacts with PstB, the cytoplasmic component of the transporter. We have also shown that the soluble form of PhoU is a dimer that binds manganese and magnesium. Alteration of highly conserved residues in PhoU by site-directed mutagenesis shows that these sites play a role in binding metals. Analysis of these phoU mutants suggests that metal binding may be important for PhoU membrane interactions. Taken together, these results support the hypothesis that PhoU is involved in the formation of a signaling complex at the cytoplasmic membrane that responds to environmental P_i levels.