A high‐throughput method to quantify feeding rates in aquatic organisms: A case study with Daphnia

1. Food ingestion is one of the most basic features of all organisms. However, obtaining precise—and high‐throughput—estimates of feeding rates remains challenging, particularly for small, aquatic herbivores such as zooplankton, snails, and tadpoles. These animals typically consume low volumes of food that are time‐consuming to accurately measure.
2. We extend a standard high‐throughput fluorometry technique, which uses a microplate reader and 96‐well plates, as a practical tool for studies in ecology, evolution, and disease biology. We outline technical and methodological details to optimize quantification of individual feeding rates, improve accuracy, and minimize sampling error.
3. This high‐throughput assay offers several advantages over previous methods, including i) substantially reduced time allotments per sample to facilitate larger, more efficient experiments; ii) technical replicates; and iii) conversion of in vivo measurements to units (mL^‐1 hr^‐1 ind^‐1) which enables broad‐scale comparisons across an array of taxa and studies.
4. To evaluate the accuracy and feasibility of our approach, we use the zooplankton, Daphnia dentifera, as a case study. Our results indicate that this procedure accurately quantifies feeding rates and highlights differences among seven genotypes.
5. The method detailed here has broad applicability to a diverse array of aquatic taxa, their resources, environmental contaminants (e.g., plastics), and infectious agents. We discuss simple extensions to quantify epidemiologically relevant traits, such as pathogen exposure and transmission rates, for infectious agents with oral or trophic transmission.

     

Manganese-54 accumulation by Chlorella spp., Daphnia magna and yellow perch (Perca flavescens)

Concentration factor and biological half-life of ⁵⁴Mn were determined in three species representing an ecologically and economically important food chain. Green algae (Chlorella spp.), Daphnia magna and yellow perch (Perca flavescens) were exposed to ⁵⁴Mn in water and assayed for ⁵⁴Mn uptake. Steady state concentration factors computed from the laboratory data for algae, Daphnia and perch were 4230, 17 000 and 11, respectively. Respective biological half-lives were 1.6, 1.2 and 8.3 days.     

Personality,Relationship Conflict,and Teamwork-Related Mental Models

This study seeks to explore whether neuroticism, agreeableness, and conscientiousness moderate the influence of relationship conflict experienced in groups on changes in group members'' evaluative cognitions related to teamwork quality (teamwork-related mental models). Data from 216 students, nested in 48 groups were analyzed using a multilevel modeling approach. Our results show that the experience of relationship conflict leads to a negative shift from the pre-task to the post-task teamwork-related mental models. Moreover, the results indicate that conscientiousness buffered the negative association between relationship conflict and the change in teamwork-related mental models. Our results did not support the hypothesized moderating effect of agreeableness and show that the detrimental effect of relationship conflict on the shift in teamwork-related mental models is accentuated for group members scoring low rather than high on neuroticism. These findings open new research venues for exploring the association between personality, coping styles and change in teamwork-related mental models.     

Structural and Functional Impact of SRP54 Mutations Causing Severe Congenital Neutropenia

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Biomechanical rationale of coronary artery bypass grafting of multivessel disease

The biomechanical model of human coronary arteries was modified for improving the quality of diagnosis and surgical treatment for coronary heart disease. The problem of hemodynamics in the left coronary artery with multivessel bed disease – 45% stenosis of the anterior descending branch and 75% stenosis of the circumflex branch – was particularly considered. Numerical simulation of the coronary arterial bypass of the main trunk was carried out to estimate the functional condition of the coronary arteries after restoring myocardial blood supply by surgery.     

Kinetics of the reaction of streptokinase-plasmin complex with purified human and mouse alpha 2-macroglobulin. Implications for mechanism.

Streptokinase-human plasmin complex (Sk-hPm) reacted rapidly with purified mouse alpha 2-macroglobulin (m alpha 2M) in vitro at 37 degrees C. Approx. 98% of the plasmin in Sk-hPm bound covalently to at least one m alpha 2M subunit. Most of the streptokinase dissociated (95%). The rate of Sk-hPm inactivation clearly depended on the m alpha 2M concentration. With 1.2 microM-m alpha 2M, 50% of the Sk-hPm (0.02 microM) reacted in less than 50 s. A double-reciprocal plot comparing pseudo-first-order rate constants (kapp.) and m alpha 2M concentration yielded a second-order rate constant of 2.3 x 10(4) M-1.s-1 (r = 0.97). This value is an approximation, since Sk-hPm preparations are heterogeneous. Sk-hPm reacted with human alpha 2M (h alpha 2M), forming alpha 2M-plasmin complex (98% covalent). More than 99% of the streptokinase dissociated. The rate of reaction of Sk-hPm with h alpha 2M did not clearly depend on inhibitor concentration. The kapp. values determined with 0.6-1.2 microM-h alpha 2M were decreased 10-20-fold compared with m alpha 2M. In order to study the effect of Sk-hPm heterogeneity on the reaction with alpha 2M, the proteinase was incubated for various amounts of time at 37 degrees C before addition of inhibitor. The enzyme amidase activity was maximal within 5 min; however, reaction of Sk-hPm with m alpha 2M or h alpha 2M was most extensive after 20 min and 2 h respectively. After incubation for more than 1 h, Sk-hPm acquired fibrinogenolytic activity, suggesting plasmin dissociation. Therefore the enhanced reaction of h alpha 2M with 'older' Sk-hPm preparations may have resulted in part from dissociated plasmin or 'plasmin-like' species. By contrast, the reaction of Sk-hPm with m alpha 2M was most rapid when the proteinase preparation was free of plasmin, indicating direct reaction of Sk-hPm with m alpha 2M as the only major mechanism. Finally, streptokinase-cat plasminogen complex reacted more extensively with m alpha 2M than with h alpha 2M, suggesting that m alpha 2M may be a superior inhibitor with this class of plasminogen activators in general.     

Fish oil affects phosphoinositide turnover and thromboxane A metabolism in cultured vascular muscle cells

Fish oil has been reported as having beneficial effects on cardiovascular diseases. Elevated serum lipoproteins, prostaglandins and intracellular free calcium concentrations [( Ca2+]i) of the vasculature and thus the phosphoinositide (PI) turnover may be involved in the pathogenesis of these disorders. Therefore, the effect of fish oil on the potency of both low-density lipoprotein (LDL) and angiotensin II (AII) to stimulate the PI turnover in cultured rat vascular smooth muscle cells (VSMC) has been studied. Furthermore, a possible link between PI turnover activity and thromboxane A2 (TXA2) metabolism in these cells has been investigated. In VSMC cultured for up to 7 weeks with either fish oil or n-3 eicosapentaenoic acid (EPA) a decrease to 5-48% of the LDL-induced inositol trisphosphate (IP3) formation (= 100%) was found. A similar range of decreased IP3 synthesis was observed, when AII was used instead of LDL. Both LDL- and AII-stimulated TXA2 synthesis was suppressed concomitantly within the range 34-60%. Blockade of VSMC TXA2 biosynthesis with either indomethacin or TXA2 synthetase blocker (SQ-80338) inhibited LDL-induced formation of IP3 in a dose-dependent manner. Similar results were obtained, when TXA2 receptor coupling antagonists (SQ-27427 or BM-13177) were used. However, blockers of TXA2 synthesis and of TXA2 receptor binding failed to affect AII-induced formation of IP3.     

Structure of the sugar-phosphate moiety of lipid A from lipooligosaccharide of Neisseria meningitidis group B,strain BC5S No. 125

On the basis of chemical and NMR data the partial structure of lipid A from lipooligosaccharide (LOS) of Neisseria meningitidis group B, strain BC₅S No 125 was established. Lipid A consisted of disaccharide 2-deoxy-6-O-[2-deoxy-2-(3-hydroxytetradecanoylamino)--gluco-pyranosyl]-2-(3-hydroxytetradecanoylamino)--glucopyranose carrying the -(2-aminoethyl)pyrophosphate residue at 0–4 and the pyrophosphate or phosphate residue at 0–1. On hydrolysis of the acidic form of LOS with 1% acetic acid the substituent at 0–1 was practically completely removed whereas that at 0–4 was stable. The analogous hydrolysis of the Mg-salt of LOS was accompanied by splitting off the pyrophosphate linkage in the substituent at 0–4. Hydrolysis of LOS at pH 4.5 in the presence of SDS led mainly to a lipid A preparation retaining both pyrophosphate residues.Abbreviations KDO 2-keto-3-deoxyoctulosonic acid - LA-I, LA-II preparations of lipid A - LOS lipooligosaccharide - LOS-H⁺ the acidic form of LOS - OS oligosaccharide - TLC thin-layer chromatography - GLC-MS gas-liquid chromatography/mass spectrometry