Competitive dominance among Cladocera: Are single-factor explanations enough?

I examine several hypotheses for competitive dominance among zooplankton using data from 20 studies containing field and laboratory experiments on competition between cladoceran species. In threeDaphnia species from rockpools studied in the laboratory, the largeD. magna was the superior competitor at higher food levels and at 15°, while the smallerD. pulex andD. longispina were dominants at low food levels at 20°.D. pulex usually excludedD. longispina. No single-factor hypothesis gives a satisfying explanation for these results. A review of the literature data suggests that none of the following hypotheses for competitive dominance have sufficient support to be considered general: The size-efficiency hypothesis (supported in 60% of the tests), ther-max hypothesis (68% support), efficiency at low food levels (36% support), and that small species are superior competitors (only 17% support). Competitive ability and susceptibility to predation appear to be positively related (9 out of 10 cases). 76% of the experiments carried out under different environmental conditions showed varying outcomes. Competition between cladocerans should evidently be studied within a multi-factor framework. Since shifts in competitive advantage with environmental changes were common, the competitive exclusion principle may often not apply in zooplankton assemblages. Non-equilibrium coexistence of competitors in a variable environment, i.e. the paradox of the plankton, is a framework worthy of consideration in zooplankton, and possibly also in many other natural communities.     

Labeling with fluorescent carbocyanine dyes of cultured endothelial and smooth muscle cells by growth in dye-containing medium

Summary We describe a method for labeling cultured endothelial cells (ECs) and smooth muscle cells (SMCs) by letting the cells grow for three days in culture medium containing a low concentration of the fluorescent carbocyanine dyes DiI and DiO. We show that good labeling can be obtained with considerably lower concentrations (2.5 g/ml) than has previously been described. With optimal concentration the labeling is very strong and seems to label all membranous structures in the cells. It was possible to clearly distinguish differentially pre-labeled cells both in coculture and seeded on denaturated vascular grafts. The cells remain fluorescent for more than seven days and may be passaged with retained proliferative capability. We suggest that DiI/DiO-labeling using dye-containing medium may be used for several cell types and is applicable in tissue culture and in the detection of implanted cells in vivo.     

The Effect of Oxytetracycline on Leukocyte Migration into Inflammatory Exudate

The migration of leukocytes to sites of infec-tion and tissue injury is a primary defence mechanism. When localized at the infection site polymorphonuclear leucocytes phagocy-tose bacteria and other foreign particles. The leukocyte is also of interest as a source of inflammation mediators e.g. metabolites of arachidonic acid (Simmons et al 1983).     

Calcium dependency of pregnant rat myometrium: comparison of circular and longitudinal muscle

The purpose of this study was to determine if the changes in spontaneous contractions of circular uterine muscle during pregnancy were related to alterations in calcium (Ca) sensitivity or dependence. Circular muscle (CM) and longitudinal muscle (LM) segments from rats on Days 16-17 of gestation and at term were compared with respect to: sensitivity of potassium (K)-induced contractions to changes in extracellular Ca, and rate and magnitude of decrease of K- and acetylcholine (ACh)-induced contractions in Ca-free medium and in methoxyverapamil (D-600). The effects of low Ca and D-600 on spontaneous electrical activity of CM were also studied. Ca sensitivity was no different in CM and LM and did not change between Day 16 and term. There was no difference in the Ca-dependence of K- or ACh-induced contractions during this time. Potassium contractions declined more rapidly than ACh contractions in Ca-free media, especially in CM. Spontaneous action potentials in CM were Ca-dependent and disappeared in low Ca or D-600 on Days 16-17 and at term. Therefore the changes in contractions of CM during pregnancy are not related directly to Ca sensitivity or dependence, but indirectly via Ca modulation of the action potentials.     

Proteomic investigation of the secretome of Cellvibrio japonicus during growth on chitin

Studies of the secretomes of microbes grown on insoluble substrates are important for the discovery of novel proteins involved in biomass conversion. However, data in literature and this study indicate that secretome samples tend to be contaminated with cytoplasmic proteins. We have examined the secretome of the Gram‐negative soil bacterium Cellvibrio japonicus using a simple plate‐based culturing technique that yields samples with high fractions (60–75%) of proteins that are predicted to be secreted. By combining this approach with label‐free quantification using the MaxLFQ algorithm, we have mapped and quantified proteins secreted by C. japonicus during growth on α‐ and β‐chitin. Hierarchical clustering of the detected protein quantities revealed groups of up‐regulated proteins that include all five putative C. japonicus chitinases as well as a chitin‐specific lytic polysaccharide monooxygenase (CjLPMO10A). A small set of secreted proteins were co‐regulated with known chitin‐specific enzymes, including several with unknown catalytic functions. These proteins provide interesting targets for further studies aimed at unraveling the enzymatic machineries used by C. japonicus for recalcitrant polysaccharide degradation. Studies of chitin degradation indicated that C. japonicus indeed produces an efficient chitinolytic enzyme cocktail. All MS data have been deposited in the ProteomeXchange with the dataset identifier PXD002843 ( http://proteomecentral.proteomexchange.org/dataset/PXD002843 ).     

Backbone Assignment of the MALT1 Paracaspase by Solution NMR

Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a unique paracaspase protein whose protease activity mediates oncogenic NF-κB signalling in activated B cell-like diffuse large B cell lymphomas (ABC-DLBCLs). ABC-DLBCLs are aggressive lymphomas with high resistance to current chemotherapies. Low survival rate among patients emphasizes the urgent need for alternative treatment options. The characterization of the MALT1 will be an essential tool for developing new target-directed drugs against MALT1 dependent disorders. As the first step in the atomic-level NMR studies of the system, here we report, the ¹⁵N/¹³C/¹H backbone assignment of the apo form of the MALT1 paracaspase region together with the third immunoglobulin-like (Ig3) domain, 44 kDa, by high resolution NMR. In addition, the non-uniform sampling (NUS) based targeted acquisition procedure is evaluated as a mean of decreasing acquisition and analysis time for larger proteins.     

metaxa2: improved identification and taxonomic classification of small and large subunit rRNA in metagenomic data

The ribosomal rRNA genes are widely used as genetic markers for taxonomic identification of microbes. Particularly the small subunit (SSU; 16S/18S) rRNA gene is frequently used for species‐ or genus‐level identification, but also the large subunit (LSU; 23S/28S) rRNA gene is employed in taxonomic assignment. The metaxa software tool is a popular utility for extracting partial rRNA sequences from large sequencing data sets and assigning them to an archaeal, bacterial, nuclear eukaryote, mitochondrial or chloroplast origin. This study describes a comprehensive update to metaxa – metaxa 2 – that extends the capabilities of the tool, introducing support for the LSU rRNA gene, a greatly improved classifier allowing classification down to genus or species level, as well as enhanced support for short‐read (100 bp) and paired‐end sequences, among other changes. The performance of metaxa 2 was compared to other commonly used taxonomic classifiers, showing that metaxa 2 often outperforms previous methods in terms of making correct predictions while maintaining a low misclassification rate. metaxa 2 is freely available from http://microbiology.se/software/metaxa2/ .     

The growth of some Ephemeropteran nymphs during winter in a North Swedish River

The growth of the Ephemeroptera species Heptagenia fuscogrisea Retzius, Leptophlebia marginata L. and Ephemerella mucronata Bengtsson was studied from the middle of September 1967 to the middle of May 1968 in the River Rickleån in northern Sweden. Sampling was performed also during periods with ice cover. Growth was estimated from four different body measures and proceeded fairly steady through all the winter for the three species. There were no indications of changed body proportions during the investigation period.