Effects of thermal acclimation and photoacclimation on lipophilic pigments in an invasive and a native cyanobacterium of temperate regions

The freshwater cyanobacterium Cylindrospermopsis raciborskii spreads from tropical to temperate regions worldwide. This entails acclimation to varied light and temperature conditions. We studied the thermal and light acclimation of the photosynthetic machinery of C. raciborskii by monitoring alteration of the chlorophyll a and carotenoid content in German strains of C. raciborskii, in African and Australian strains of C. raciborskii, and in German strains of Aphanizomenon gracile, a native cyanobacterium belonging to the same order (Nostocales). Our results showed that temperate and tropical C. raciborskii strains did not differ in pigment acclimation to light and temperature. In contrast, the ratio of photoprotective carotenoids (namely the carotenoid glycoside 4-hydroxymyxol glycoside [aphanizophyll]) to chlorophyll a increased significantly more in C. raciborskii in comparison with A. gracile (1) with decreasing temperatures from 20 to 10°C and a moderate light intensity of 80?µmol photons m^?2?s^?1 and (2) with increasing light intensities at a suboptimal temperature of 15°C, compared to 20°C. We conclude that below 20°C photoinhibition is avoided by greater photoprotection in the invasive species C. raciborskii compared to the native species A. gracile.     

Uptake and subcellular partitioning of trivalent metals in a green alga: comparison between Al and Sc

Despite 40+ years of research on aluminum (Al) toxicity in aquatic organisms, Al transport mechanisms through biological membranes, and the intracellular fate of Al once assimilated, remain poorly understood. The trivalent metal scandium shares chemical similarities with Al and, unlike Al, it has a convenient radioactive tracer (Sc-46) allowing for relatively simple measurements at environmentally relevant concentrations. Thus, we investigated the potential of Sc to substitute for Al in uptake and intracellular fate studies with the green alga Chlamydomonas reinhardtii. Short-term (<60 min) competitive uptake experiments indicated that Al does not inhibit Sc influx, implying that these metals do not share a common transport mechanism. Also, internalized Al concentrations were ~4 times higher than Sc concentrations after long-term (72 h) exposures under similar conditions (4.5 μM Al_T or Sc_T, 380 μM F_T, pH 7.0, 3.8 pM Al _calc ³⁺ and 1.0 pM Sc _calc ³⁺ ). However, interesting similarities were observed in their relative subcellular distributions, suggesting possible common toxicity/tolerance mechanisms. Both metals mostly distributed to the organelles fraction and almost no association was found with the cytosolic proteins. The greatest difference was observed in the cellular debris fraction (membranes and nucleus) where Al was much more concentrated than Sc. However, it is not clear whether or not this fraction contained extracellular metal associated with the algal surface. To summarize, Sc does not seem to be an adequate substitute of Al for transport/uptake studies, but could be for investigations of toxicity/tolerance mechanisms in C. reinhardtii. Further work is needed to verify this latter suggestion.     

HIV coreceptors,cell tropism and inhibition by chemokine receptor ligands

HIV is a persistent virus that survives and replicates despite an onslaught by the host's immune system. A strategy for cell entry, requiring the use of two receptors, has evolved that may help evade neutralizing antibodies. HIV and SIV usually require both CD4 and a seven transmembrane (7TM) coreceptor for infection. At least eleven different 7TM coreceptors have been identified that confer HIV and/ or SIV entry. For HIV-1, the major coreceptors are CCR5 and CXCR4, while the role of other coreceptors for replication and cell tropism in vivo is currently unclear. Polymorphisms in the CCR5 gene that reduce CCR5 expression levels, protect against disease progression, suggesting that drugs targeted to CCR5 could be effective. Such therapies however will not work if HIV simply adapts to use alternative coreceptors. In the light of these themes, this review will discuss the following topics: (i) the coreceptors used by primary HIV-1 and HIV-2 viruses, (ii) the properties and coreceptors of HIV-2 strains that infect cells without CD4, (iii) the role of coreceptors in HIV cell tropism and particularly macrophage infection and (iv) the properties of chemokine receptor ligands that block HIV infection.     

Search for new tools to combat Gram-negative resistant bacteria among amine derivatives of 5-arylidenehydantoin

A series of amine-alkyl derivatives of 5-arylidenehydantoin 3–21 was evaluated for their ability to improve antibiotic effectiveness in two strains of Gram-negative Enterobacter aerogenes: the reference strain (ATCC-13048) and the chloramphenicol-resistant derivative over-producing the AcrAB-TolC efflux pump (CM-64). Three antibiotics, chloramphenicol, nalidixic acid and sparfloxacin were used as markers of efflux pump activity. New compounds (5–16) were obtained within 3–4 step synthesis using Knoevenagel condensation, Mitsunobu reaction and microwave aided N-alkylation. Molecular modeling based structure–activity relationship (SAR) studies were performed. The most active compounds: (Z)-5-(4-(diethylamino)benzylidene)-3-(2-hydroxy-3-(4-(2-hydroxyethyl)piperazin-1-yl)propyl)imidazolidine-2,4-dione (14) and (Z)-5-(2,4-dimethoxybenzylidene)-3-(2-hydroxy-3-(isopropylamino)propyl)imidazolidine-2,4-dione (15) induced fourfold decrease of minimal inhibition concentration (MIC) of all tested antibiotics in the strain CM-64 overexpressing the AcrAB-TolC pump.     

Omi, a recessive mutation on chromosome 10, is a novel allele of Ostm1

Large-scale N-ethyl-N-nitrosourea (ENU) mutagenesis has provided many rodent models for human disease. Here we describe the initial characterization and mapping of a recessive mutation that leads to degeneration of the incisors, failure of molars to erupt, a grey coat colour, and mild osteopetrosis. We mapped the omi mutation to chromosome 10 between D10Mit214 and D10Mit194. The Ostm1 gene is a likely candidate gene in this region and the grey-lethal allele, Ostm1 ^gl , and omi mutations fail to complement each other. We show that om/om mice have reduced levels of Ostm1 protein. To date we have not been able to identify the causative mutation. We propose that omi is a novel hypomorphic mutation affecting Ostm1 expression, potentially in a regulatory element.     

Indigenous Vibrio cholerae strains from a non-endemic region are pathogenic

Of the 200+ serogroups of Vibrio cholerae, only O1 or O139 strains are reported to cause cholera, and mostly in endemic regions. Cholera outbreaks elsewhere are considered to be via importation of pathogenic strains. Using established animal models, we show that diverse V. cholerae strains indigenous to a non-endemic environment (Sydney, Australia), including non-O1/O139 serogroup strains, are able to both colonize the intestine and result in fluid accumulation despite lacking virulence factors believed to be important. Most strains lacked the type three secretion system considered a mediator of diarrhoea in non-O1/O13 V. cholerae. Multi-locus sequence typing (MLST) showed that the Sydney isolates did not form a single clade and were distinct from O1/O139 toxigenic strains. There was no correlation between genetic relatedness and the profile of virulence-associated factors. Current analyses of diseases mediated by V. cholerae focus on endemic regions, with only those strains that possess particular virulence factors considered pathogenic. Our data suggest that factors other than those previously well described are of potential importance in influencing disease outbreaks.     

Feedback GAP: pragmatic,cluster-randomized trial of goal setting and action plans to increase the effectiveness of audit and feedback interventions in primary care

Background

Audit and feedback to physicians is a commonly used quality improvement strategy, but its optimal design is unknown. This trial tested the effects of a theory-informed worksheet to facilitate goal setting and action planning, appended to feedback reports on chronic disease management, compared to feedback reports provided without these worksheets.

Methods

A two-arm pragmatic cluster randomized trial was conducted, with allocation at the level of primary care clinics. Participants were family physicians who contributed data from their electronic medical records. The ‘usual feedback’ arm received feedback every six months for two years regarding the proportion of their patients meeting quality targets for diabetes and/or ischemic heart disease. The intervention arm received these same reports plus a worksheet designed to facilitate goal setting and action plan development in response to the feedback reports. Blood pressure (BP) and low-density lipoprotein cholesterol (LDL) values were compared after two years as the primary outcomes. Process outcomes measured the proportion of guideline-recommended actions (e.g., testing and prescribing) conducted within the appropriate timeframe. Intention-to-treat analysis was performed.

Results

Outcomes were similar across groups at baseline. Final analysis included 20 physicians from seven clinics and 1,832 patients in the intervention arm (15% loss to follow up) and 29 physicians from seven clinics and 2,223 patients in the usual feedback arm (10% loss to follow up). Ten of 20 physicians completed the worksheet at least once during the study. Mean BP was 128/72 in the feedback plus worksheet arm and 128/73 in the feedback alone arm, while LDL was 2.1 and 2.0, respectively. Thus, no significant differences were observed across groups in the primary outcomes, but mean haemoglobin A1c was lower in the feedback plus worksheet arm (7.2% versus 7.4%, p<0.001). Improvements in both arms were noted over time for one-half of the process outcomes.

Discussion

Appending a theory-informed goal setting and action planning worksheet to an externally produced audit and feedback intervention did not lead to improvements in patient outcomes. The results may be explained in part by passive dissemination of the worksheet leading to inadequate engagement with the intervention.

Trial registration

ClinicalTrials.gov NCT00996645

     

Dynamics of Peripheral Blood Lymphocyte Subpopulations in the Acute and Subacute Phase of Legionnaires’ Disease

Study Objective

Absolute lymphocytopenia is recognised as an important hallmark of the immune response to severe infection and observed in patients with Legionnaires’ disease. To explore the immune response, we studied the dynamics of peripheral blood lymphocyte subpopulations in the acute and subacute phase of LD.

Methods and Results

EDTA-anticoagulated blood was obtained from eight patients on the day the diagnosis was made through detection of L. pneumophila serogroup 1 antigen in urine. A second blood sample was obtained in the subacute phase. Multiparametric flow cytometry was used to calculate lymphocyte counts and values for B-cells, T-cells, NK cells, CD4⁺ and CD8⁺ T-cells. Expression of activation markers was analysed. The values obtained in the subacute phase were compared with an age and gender matched control group. Absolute lymphocyte count (×10⁹/l, median and range) significantly increased from 0.8 (0.4–1.6) in the acute phase to 1.4 (0.8–3.4) in the subacute phase. B-cell count showed no significant change, while T-cell count (×10⁶/l, median and range) significantly increased in the subacute phase (495 (182–1024) versus 979 (507–2708), p = 0.012) as a result of significant increases in both CD4⁺ and CD8⁺ T-cell counts (374 (146–629) versus 763 (400–1507), p = 0.012 and 119 (29–328) versus 224 (107–862), p = 0.012). In the subacute phase of LD, significant increases were observed in absolute counts of activated CD4⁺ T-cells, naïve CD4⁺ T-cells and memory CD4⁺ T-cells. In the CD8⁺ T-cell compartment, activated CD8⁺ T-cells, naïve CD8⁺ T-cell and memory CD8⁺ T-cells were significantly increased (p<0.05).

Conclusion

The acute phase of LD is characterized by absolute lymphocytopenia, which recovers in the subacute phase with an increase in absolute T-cells and re-emergence of activated CD4⁺ and CD8⁺ T cells. These observations are in line with the suggested role for T-cell activation in the immune response to LD.     

CT Coronary Angiography Is Feasible for the Assessment of Coronary Artery Disease in Chronic Dialysis Patients,Despite High Average Calcium Scores

Purpose

Significant obstructive coronary artery disease (CAD) is common in asymptomatic dialysis patients. Identifying these high risk patients is warranted and may improve the prognosis of this vulnerable patient group. Routine catheterization of incident dialysis patients has been proposed, but is considered too invasive. CT-angiography may therefore be more appropriate. However, extensive coronary calcification, often present in this patient group, might hamper adequate lumen evaluation. The objective of this study was to assess the feasibility of CT-angiography in this patient group.

Methods

For this analysis all patients currently participating in the ICD2 trial (ISRCTN20479861), with no history of PCI or CABG were included. The major epicardial vessels were evaluated on a segment basis (segment 1–3, 5–8, 11 and 13) by a team consisting of an interventional and an imaging specialist. Segments were scored as not significant, significant and not interpretable.

Results

A total of 70 dialysis patients, with a mean age of 66±8 yrs and predominantly male (70%) were included. The median calcium score was 623 [79, 1619].Over 90% of the analyzed segments were considered interpretable. The incidence of significant CAD on CT was 43% and was associated with cardiovascular events during follow-up. The incidence of cardiovascular events after 2-years follow-up: 36% vs. 0% in patients with no significant CAD (p<0.01).

Conclusion

Despite the high calcium scores CT-angiography is feasible for the evaluation of the extent of CAD in dialysis patients. Moreover the presence of significant CAD on CT was associated with events during follow-up.     

Extent and Degree of Shoreline Oiling: Deepwater Horizon Oil Spill,Gulf of Mexico,USA

The oil from the 2010 Deepwater Horizon spill in the Gulf of Mexico was documented by shoreline assessment teams as stranding on 1,773 km of shoreline. Beaches comprised 50.8%, marshes 44.9%, and other shoreline types 4.3% of the oiled shoreline. Shoreline cleanup activities were authorized on 660 km, or 73.3% of oiled beaches and up to 71 km, or 8.9% of oiled marshes and associated habitats. One year after the spill began, oil remained on 847 km; two years later, oil remained on 687 km, though at much lesser degrees of oiling. For example, shorelines characterized as heavily oiled went from a maximum of 360 km, to 22.4 km one year later, and to 6.4 km two years later. Shoreline cleanup has been conducted to meet habitat-specific cleanup endpoints and will continue until all oiled shoreline segments meet endpoints. The entire shoreline cleanup program has been managed under the Shoreline Cleanup Assessment Technique (SCAT) Program, which is a systematic, objective, and inclusive process to collect data on shoreline oiling conditions and support decision making on appropriate cleanup methods and endpoints. It was a particularly valuable and effective process during such a complex spill.