Extraction methods for phycocyanin determination in freshwater filamentous cyanobacteria and their application in a shallow lake

Phycocyanin (PC) is one of the water-soluble accessory pigments of cyanobacteria species, and its concentration in aquatic systems is used to estimate the presence and relative abundance of blue-green algae. PC concentration and the PC/Chl-a ratio of four N2-fixing filamentous cyanobacteria strains (Cylindrospermopsis raciborskii, Anabaena spiroides, Aphanizomenon flos-aquae and Aphanizomenon issatschenkoi) common to Lake Balaton (Hungary) were determined using repeated freezing and thawing. A strong linear correlation was found between the extracted PC and Chl-a concentrations for all strains at high Chl-a concentrations (almost stable PC/Chl-a ratio in the range of 20−100 µg l−1 Chl-a). Extraction of PC and Chl-a from samples with low biomass of cyanobacteria (less than 20 µg l−1 Chl-a) proved to be unreliable using the standard protocol of freeze–thaw cycles (coefficients of variation exceeding 10–15%). In order to find an extraction method that is robust in fresh waters characterized by low algae biomass (e.g. Lake Balaton), the effectiveness of four extraction methods (repeated freeze–thaw method and homogenization with mortar and pestle, Ultrasonic, and Polytron homogenizer) were compared using C. raciborskii. It was found that the efficiency of extraction of phycocyanin was highest when a single freeze–thaw cycle was followed by sonication (25% additional yield compared with using the freeze–thaw method alone). Applying this combined method to surface water samples of Lake Balaton, a strong correlation was found between PC concentration and cyanobacterial biomass (R 2 = 0.9436), whilst the repeated freezing–thawing method found no detectable PC content. Here we show that the combined sonication/freeze–thaw method could be suitable for measuring filamentous cyanobacteria PC content, even at low concentrations; as well as for the estimation of cyanobacterial contribution to total biomass in fresh waters

Prophylaxis of Cyanobacterial and Mushroom Cyclic Peptide Toxins1

ABSTRAC

Not just for romance: applications of speed dating in social work education

In this article we address how a contemporary adaptation of the \u27speed dating\u27 model was used for educational purposes with two cohorts of social work students. We outline the dimensions of \u27speed dating\u27 as a contemporary social phenomenon, then address how this model relates specifically to groupwork process, and can be used to facilitate social work student learning. The curriculum for two classroom group activities using the \u27speed dating\u27 model are outlined, the first to develop university level study skills, the second for debriefing field placement learning experiences. Finally we examine why the \u27speed dating\u27 metaphor was successful in provoking a playful yet constructively creative space for students to engage in groupwork process.<br /

Receptors for Hyaluronic Acid and Poliovirus: A Combinatorial Role in Glioma Invasion?

Background: CD44 has long been associated with glioma invasion while, more recently, CD155 has been implicated in playing a similar role. Notably, these two receptors have been shown closely positioned on monocytes. Methods and Findings: In this study, an up-regulation of CD44 and CD155 was demonstrated in established and earlypassage cultures of glioblastoma. Total internal reflected fluorescence (TIRF) microscopy revealed close proximity of CD44 and CD155. CD44 antibody blocking and gene silencing (via siRNA) resulted in greater inhibition of invasion than that for CD155. Combined interference resulted in 86 % inhibition of invasion, although in these investigations no obvious evidence of synergy between CD44 and CD155 in curbing invasion was shown. Both siRNA-CD44 and siRNA-CD155 treated cells lacked processes and were rounder, while live cell imaging showed reduced motility rate compared to wild type cells. Adhesion assay demonstrated that wild type cells adhered most efficiently to laminin, whereas siRNA-treated cells (p,0.0001 for both CD44 and CD155 expression) showed decreased adhesion on several ECMs investigated. BrdU assay showed a higher proliferation of siRNA-CD44 and siRNA-CD155 cells, inversely correlated with reduced invasion. Confocal microscopy revealed overlapping of CD155 and integrins (b1, avb1 and avb3) on glioblastoma cell processes whereas siRNAtransfected cells showed consequent reduction in integrin expression with no specific staining patterns. Reduced expression of Rho GTPases, Cdc42, Rac1/2/3, RhoA and RhoB, was seen in siRNA-CD44 and siRNA-CD155 cells. In contrast t

High and Low Molecular Weight Hyaluronic Acid Differentially Regulate Human Fibrocyte Differentiation

Following tissue injury, monocytes can enter the tissue and differentiate into fibroblast-like cells called fibrocytes, but little is known about what regulates this differentiation. Extracellular matrix contains high molecular weight hyaluronic acid (HMWHA; ∼2×10(6) Da). During injury, HMWHA breaks down to low molecular weight hyaluronic acid (LMWHA; ∼0.8-8×10(5) Da).In this report, we show that HMWHA potentiates the differentiation of human monocytes into fibrocytes, while LMWHA inhibits fibrocyte differentiation. Digestion of HMWHA with hyaluronidase produces small hyaluronic acid fragments, and these fragments inhibit fibrocyte differentiation. Monocytes internalize HMWHA and LMWHA equally well, suggesting that the opposing effects on fibrocyte differentiation are not due to differential internalization of HMWHA or LMWHA. Adding HMWHA to PBMC does not appear to affect the levels of the hyaluronic acid receptor CD44, whereas adding LMWHA decreases CD44 levels. The addition of anti-CD44 antibodies potentiates fibrocyte differentiation, suggesting that CD44 mediates at least some of the effect of hyaluronic acid on fibrocyte differentiation. The fibrocyte differentiation-inhibiting factor serum amyloid P (SAP) inhibits HMWHA-induced fibrocyte differentiation and potentiates LMWHA-induced inhibition. Conversely, LMWHA inhibits the ability of HMWHA, interleukin-4 (IL-4), or interleukin-13 (IL-13) to promote fibrocyte differentiation.We hypothesize that hyaluronic acid signals at least in part through CD44 to regulate fibrocyte differentiation, with a dominance hierarchy of SAP>LMWHA≥HMWHA>IL-4 or IL-13

A Reliability-Generalization Study of Journal Peer Reviews: A Multilevel Meta-Analysis of Inter-Rater Reliability and Its Determinants

Background: This paper presents the first meta-analysis for the inter-rater reliability (IRR) of journal peer reviews. IRR is defined as the extent to which two or more independent reviews of the same scientific document agree. Methodology/Principal Findings: Altogether, 70 reliability coefficients (Cohen’s Kappa, intra-class correlation [ICC], and Pearson product-moment correlation [r]) from 48 studies were taken into account in the meta-analysis. The studies were based on a total of 19,443 manuscripts; on average, each study had a sample size of 311 manuscripts (minimum: 28, maximum: 1983). The results of the meta-analysis confirmed the findings of the narrative literature reviews published to date: The level of IRR (mean ICC/r 2 =.34, mean Cohen’s Kappa =.17) was low. To explain the study-to-study variation of the IRR coefficients, meta-regression analyses were calculated using seven covariates. Two covariates that emerged in the metaregression analyses as statistically significant to gain an approximate homogeneity of the intra-class correlations indicated that, firstly, the more manuscripts that a study is based on, the smaller the reported IRR coefficients are. Secondly, if the information of the rating system for reviewers was reported in a study, then this was associated with a smaller IRR coefficient than if the information was not conveyed. Conclusions/Significance: Studies that report a high level of IRR are to be considered less credible than those with a low level o