Vector-borne parasites decrease host mobility: a field test of freeze or flee behaviour of willow ptarmigan

Transmission mode has been suggested to be a strong predictor of virulence. According to theory, the transmission of vector-borne parasites should be less dependent on host mobility than directly transmitted parasites. This could select for increased exploitation of host resources in parasites transmitted by vectors, which may be manifested as higher virulence. Here, we test the prediction that there is an association between transmission mode and the effect on host mobility by comparing parasite infection levels and mobility in willow ptarmigan (Lagopus lagopus L.). We examined the endoparasite infracommunities of individual hosts to obtain annual, quantitative data on four vector-transmitted species (Leucocytozoon lovati, Trypanosoma avium, Haemoproteus mansoni and microfilaria), two directly transmitted species (Trichostrongylus tenuis and Eimeria sp.) and two species with indirect life cycles (Hymenolepis microps and Parionella urogalli). We then used observed variations in freeze-or-flee responses of individual willow ptarmigan to assess whether parasite intensities were related to scored freezing responses. From a field data set covering a period of 9 years from a single area, we found that stronger freezing responses were associated with higher intensities of vector-borne parasites, especially with higher intensities of the haemosporidian L. lovati. Freezing responses were not associated with parasites transmitted in other ways. Thus, high intensities of vector-borne parasites tended to reduce host movements, while parasites with other transmission modes did not.     

Feeding,resting and social behaviour in ewes housed in two different group sizes

The aim of this experiment was to investigate the effects of increased group size on eating- and resting behaviour, aggression and feed intake in housed ewes. During an initial period of 14 days 36 adult (2–6 years old) ewes of the domestic Norwegian Dala breed were divided into four groups of 9. In the second period (14 days), these ewes were merged into one group of 36 ewes. This experiment was repeated with a second batch of ewes, but this time starting with a group of 36 individuals in the first period, then splitting them up into four groups of 9 ewes in the second period. From 24 h video recordings we scored activity behaviours using instantaneous sampling every 10 min. Aggressive interactions were continuously observed the first 10 min every hour during the 24 h (4 h in total). A mixed statistical procedure with group size, day, batch and the interactions between them were included as fixed effects, whereas individual and group were specified as random effects.Ewes in large groups (36) had a larger variation in lying time at day one (P < 0.01), less synchronized lying (P < 0.05) and eating behaviour (P < 0.01), and spent less time queuing at the feed barrier (P < 0.001) compared to in the small group size (9). There were no effects of group size on aggressive interactions or feed intake.In conclusion, a larger group size decreased synchrony in resting and feeding behaviour and reduced the time spent queuing in front of the feed barrier. It is possible that the aggression level in sheep is more sensitive to changes in space allowance than to changes in group size per se.     

The timely deposition of callose is essential for cytokinesis in Arabidopsis

The primary plant cell wall is laid down over a brief period of time during cytokinesis. Initially, a membrane network forms at the equator of a dividing cell. The cross-wall is then assembled and remodeled within this membrane compartment. Callose is the predominant luminal component of the nascent cross-wall or cell plate, but is not a component of intact mature cell walls, which are composed primarily of cellulose, pectins and xyloglucans. Widely accepted models postulate that callose comprises a transient, rapid spreading force for the expansion of membrane networks during cytokinesis. In this study, we clone and characterize an Arabidopsis gene, MASSUE / AtGSL8 , which encodes a putative callose synthase. massue mutants are seedling-lethal and have a striking cytokinesis-defective phenotype. Callose deposition was delayed in the cell plates of massue mutants. Mutant cells were occasionally bi- or multi-nucleate, with cell-wall stubs, and we frequently observed gaps at the junction between cross-walls and parental cell walls. The results suggest that the timely deposition of callose is essential for the completion of plant cytokinesis. Surprisingly, confocal analysis revealed that the cell-plate membrane compartment forms and expands, seemingly as far as the parental wall, prior to the appearance of callose. We discuss the possibility that callose may be required to establish a lasting connection between the nascent cross-wall and the parental cell wall.     

Environmental Shaping of Ribosomal RNA Nucleotide Composition

Ribosomal RNA (rRNA) is one of the most important macromolecules in the cell. It is well established that high-temperature environmental conditions destabilize rRNA, leading to a selection for G+C-rich stabilizing structures. Our knowledge about the nucleotide composition effect of other environmental conditions, however, is limited. In the present work, I addressed this by correlating the rRNA nucleotide composition to known environmental habitats for bacteria. The bacterial phyla Firmicutes, Actinobacteria, and Proteobacteria were chosen for in-depth analyses due to the abundance of information available in the databases. Major differences in nucleotide composition were identified between these phyla. In addition to the G+C-->A+T gradients, a main gradient of G+A-->C+T was identified for Firmicutes, while a G+T-->A+C gradient was identified for Actinobacteria. With respect to correlation to environmental conditions, the Firmicutes showed a main structure of high G+C being correlated to thermophilic conditions, high A+T to anaerobic conditions, and high C+T to halophilic conditions. The main patterns detected for Firmicutes can be explained by structural stability for high G+C, chemical instability of G under aerobic conditions, and structural stability by purine/pyrimidine skew for halophilic conditions. On the contrary, the correlations for Actinobacteria cannot easily be explained by chemical and/or structural stability. This may indicate interference with factors not included in my work. Finally, I found a main correlation between high A+T and endosymbiosis for Proteobacteria. High A+T probably reflects adaptation to cell internal growth. Further support for environmentally driven nucleotide composition shaping was found and that polyphyletic bacteria were associated with the same environment/nucleotide correlations. My conclusion is that environmental conditions and habitats have a major effect on rRNA nucleotide composition but that the effects may differ between the bacterial phyla.     

Temporal and Spatial Diversity of the Tap Water Microbiota in a Norwegian Hospital

We analyzed the temporal and spatial diversity of the microbiota in a low-usage and a high-usage hospital tap. We identified a tap-specific colonization pattern, with potential human pathogens being overrepresented in the low-usage tap. We propose that founder effects and local adaptation caused the tap-specific colonization patterns. Our conclusion is that tap-specific colonization represents a potential challenge for water safety.Humans are exposed to and consume large amounts of tap water in their everyday life, with the tap water microbiota representing a potent reservoir for pathogens (8). Despite the potential impact, our knowledge about the ecological diversification processes of the tap water microbiota is limited (4, 11).The aim of the present work was to determine the temporal and spatial distribution patterns of the planktonic tap water microbiota. We compared the summer and winter microbiota from two hospital taps supplied from the same water source. We analyzed 16S rRNA gene clone libraries by using a novel alignment-independent approach for operational taxonomic unit (OTU) designation (6), while established OTU diversity and richness estimators were used for the ecological interpretations.Tap water samples (1 liter) from a high-usage kitchen and a low-usage toilet cold-water tap in Akershus University Hospital, Lørenskog, Norway, were collected in January and July 2006. The total DNA was isolated and the 16S rRNA gene PCR amplified and sequenced. Based on the sequences, we estimated the species richness and diversity, we calculated the distances between the communities, and trees were constructed to reflect the relatedness of the microbiota in the samples analyzed. Details about these analytical approaches are given in the materials and methods section in the supplemental material.Our initial analysis of species composition was done using the RDPII hierarchical classifier. We found that the majority of pathogen-related bacteria in our data set belonged to the class Gammaproteobacteria. The genera encompassed Legionella, Pseudomonas, and Vibrio (Table ​(Table1).1). We found a significant overrepresentation of pathogen-related bacteria in the toilet tap (P = 0.04), while there were no significant differences between summer and winter samples. Legionella showed the highest relative abundance for the pathogen-related bacteria. With respect to the total diversity, we found that Proteobacteria dominated the tap water microbiota (representing 86% of the taxa) (see Table S1 in the supplemental material). There was, however, a large portion (56%) of the taxa that could not be assigned to the genus level using this classifier.

TABLE 1.

Cloned sequences related to human pathogens^a

Ambulatory-Based Standardized Therapy for Multi-Drug Resistant Tuberculosis: Experience from Nepal, 2005–2006

Objective

The aim of this study was to describe treatment outcomes for multi-drug resistant tuberculosis (MDR-TB) outpatients on a standardized regimen in Nepal.

Methodology

Data on pulmonary MDR-TB patients enrolled for treatment in the Green Light Committee-approved National Programme between 15 September 2005 and 15 September 2006 were studied. Standardized regimen was used (8Z-Km-Ofx-Eto-Cs/16Z-Ofx-Eto-Cs) for a maximum of 32 months and follow-up was by smear and culture. Drug susceptibility testing (DST) results were not used to modify the treatment regimen. MDR-TB therapy was delivered in outpatient facilities for the whole course of treatment. Multivariable analysis was used to explain bacteriological cure as a function of sex, age, initial body weight, history of previous treatment and the region of report.

Principal Findings

In the first 12-months, 175 laboratory-confirmed MDR-TB cases (62% males) had outcomes reported. Most cases had failed a Category 2 first-line regimen (87%) or a Category 1 regimen (6%), 2% were previously untreated contacts of MDR-TB cases and 5% were unspecified. Cure was reported among 70% of patients (range 38%–93% by Region), 8% died, 5% failed treatment, and 17% defaulted. Unfavorable outcomes were not correlated to the number of resistant drugs at baseline DST. Cases who died had a lower mean body weight than those surviving (40.3 kg vs 47.2 kg, p<0.05). Default was significantly higher in two regions [Eastern OR = 6.2; 95%CL2.0-18.9; Far West OR = 5.0; 95%CL1.0-24.3]. At logistic regression, cure was inversely associated with body weight <36 kg [Adj.OR = 0.1; 95%CL0.0-0.3; ref. 55–75 kg] and treatment in the Eastern region [Adj.OR = 0.1; 95%CL0.0-0.4; ref. Central region].

Conclusions

The implementation of an ambulatory-based treatment programme for MDR-TB based on a fully standardized regimen can yield high cure rates even in resource-limited settings. The determinants of unfavorable outcome should be investigated thoroughly to maximize likelihood of successful treatment.     

The Type 2 Diabetes Associated Minor Allele of rs2237895 KCNQ1 Associates with Reduced Insulin Release Following an Oral Glucose Load

Background

Polymorphisms in the potassium channel, voltage-gated, KQT-like subfamily, member 1 (KCNQ1) have recently been reported to associate with type 2 diabetes. The primary aim of the present study was to investigate the putative impact of these KCNQ1 polymorphisms (rs2283228, rs2237892, rs2237895, and rs2237897) on estimates of glucose stimulated insulin release.

Methodology/Principal Findings

Genotypes were examined for associations with serum insulin levels following an oral glucose tolerance test (OGTT) in a population-based sample of 6,039 middle-aged and treatment-naïve individuals. Insulin release indices estimated from the OGTT and the interplay between insulin sensitivity and insulin release were investigated using linear regression and Hotelling T2 analyses.Applying an additive genetic model the minor C-allele of rs2237895 was associated with reduced serum insulin levels 30 min (mean±SD: (CC) 277±160 vs. (AC) 280±164 vs. (AA) 299±200 pmol/l, p = 0.008) after an oral glucose load, insulinogenic index (29.6±17.4 vs. 30.2±18.7vs. 32.2±22.1, p = 0.007), incremental area under the insulin curve (20,477±12,491 vs. 20,503±12,386 vs. 21,810±14,685, p = 0.02) among the 4,568 individuals who were glucose tolerant. Adjustment for the degree of insulin sensitivity had no effect on the measures of reduced insulin release. The rs2237895 genotype had a similar impact in the total sample of treatment-naïve individuals. No association with measures of insulin release were identified for the less common diabetes risk alleles of rs2237892, rs2237897, or rs2283228.

Conclusion

The minor C-allele of rs2237895 of KCNQ1, which has a prevalence of about 42% among Caucasians was associated with reduced measures of insulin release following an oral glucose load suggesting that the increased risk of type 2 diabetes, previously reported for this variant, likely is mediated through an impaired beta cell function.