Rotifers from the Balearic archipelago

Ecological and historical factors of the Balearic archipelago (Western Mediterranean Sea) result is some peculiarities to its rotifer fauna. A group of warm-stenothermous species are frequent seasonally in the islands. Among them the occurrence of Keratella procurva (Thorpe, 1912), a pantropical species, is remarkable, and this is found more or less abundantly on each island. We briefly describe the different habitat categories of the archipelago. Clustering the collected species we relate each community type to its habitat; in this sense we distinguish 4 community type in the islands corresponding to different environments. This work also summarizes all the obtainable data on the rotifer fauna of the Balearic archipelago, adding the results of the investigations done in the last survey (spring, 1989); a checklist, including 100 species from the archipelago, is shown (69 Majorca, 72 Minorca, 24 Ibiza, 25 Formentera). Some examples of pantropical distribution are given, and the biotic and abiotic factors which determine the colonization of the islands by these species are discussed.     

Preservation of fresh edible cactus stems (<i>Opuntia ficus indica</i> Mill.) by modified atmosphere packaging

Cactus stems, the cladodes of Opuntia spp. cacti, are consumed in Mexico and other countries due to their fresh and herbaceous flavor, and because of their widely known nutraceutical benefits. In order to extend the postharvest life of this vegetable, the effect of a modified atmosphere packaging (MAP) was studied in cactus stems of the cultivar Atlixco stored at 4 ± 1 °C for 20 days under three types of atmospheres: (1) air (passive atmosphere), (2) 5 kPa O₂ + 4 kPa CO₂, and (3) N₂. During storage, the titratable acidity decreased and the color of cladodes became darker and less green; however, the 5 kPa O₂ + 4 kPa CO₂ atmosphere was able to preserve both quality characteristics. All modified atmospheres reduced weight loss (from 8 to <2%) and the symptoms of chilling injury, and this physiological disorder appeared earlier in controls than in MAP-stored cladodes. The levels of fermentation metabolites were low in all three evaluated atmospheres. Because of this, only cladodes stored under the N₂ atmosphere were selected for furthersensory analysis of the MAP effect on odor perception as evaluated by a trained panel. Results indicated that there was no detrimental effect (atypical odors) of MAP on this sensory characteristic. We conclude that cultivar Atlixco is suitable for preservation using MAP technology.     

Listeria protein ActA mimics WASp family proteins: it activates filament barbed end branching by Arp2/3 complex

Actin-based propulsion of the bacteria Listeria and Shigella mimics the forward movement of the leading edge of motile cells. While Shigella harnesses the eukaryotic protein N-WASp to stimulate actin polymerization and filament branching through Arp2/3 complex, the Listeria surface protein ActA directly activates Arp2/3 complex by an unknown mechanism. Here we show that the N-terminal domain of ActA binds one actin monomer, in a profilin-like fashion, and Arp2/3 complex and mimics the C-terminal domain of WASp family proteins in catalyzing filament barbed end branching by Arp2/3 complex. No evidence is found for side branching of filaments by ActA-activated Arp2/3 complex. Mutations in the conserved acidic (41)DEWEEE(46) and basic (146)KKRRK(150) regions of ActA affect Arp2/3 binding but not G-actin binding. The motility properties of wild-type and mutated Listeria strains in living cells and in the medium reconstituted from pure proteins confirm the conclusions of biochemical experiments. Filament branching is followed by rapid debranching. Debranching is 3-4-fold faster when Arp2/3 is activated by ActA than by the C-terminal domain of N-WASp. VASP is required for efficient propulsion of ActA-coated beads in the reconstituted motility medium, but it does not affect the rates of barbed end branching/debranching by ActA-activated Arp2/3 nor the capping of filaments. VASP therefore affects another still unidentified biochemical reaction that plays an important role in actin-based movement.     

Actin lessons from pathogens

Salmonella typhimurium secretes proteins that co-opt the host actin cytoskeleton to induce membrane ruffling, leading to the uptake of the bacterium. New information about the biochemical activities of the Salmonella protein SipA suggests that this protein might inhibit host cell actin dynamics by competing with ADF/cofilin and gelsolin, two key proteins that promote the turnover of actin filaments.     

Development of 22 new microsatellite loci for fishers (Martes pennanti) with variability results from across their range

We developed 22 new microsatellite loci for the fisher (Martes pennanti), a North American mesocarnivore. The loci were developed with samples from the southern Sierra Nevada Mountains in California, and were screened with samples from this population and four other populations. We observed a range of six to 21 polymorphic loci per population, with the Sierra Nevada population exhibiting markedly lower levels of variation compared to the other four.     

Abatacept decreases disease activity in a absence of CD4+ T cells in a collagen-induced arthritis model

IntroductionAbatacept is a fusion protein of human cytotoxic T-lymphocyte–associated protein (CTLA)-4 and the Fc portion of human immunoglobulin G1 (IgG1). It is believed to be effective in the treatment of rheumatoid arthritis by inhibiting costimulation of T cells via blocking CD28–B7 interactions as CTLA-4 binds to both B7.1 (CD80) and B7.2 (CD86). However, the interaction of CD28 with B7 molecules is crucial for activation of naive cells, whereas it is unclear whether the action of already activated CD4⁺ T cells, which are readily present in established disease, also depends on this interaction. The aim of this study was to determine whether the mode of action of abatacept depends solely on its ability to halt T cell activation in established disease.MethodsArthritis was induced in thymectomized male DBA/1 mice by immunisation with bovine collagen type II. The mice were subsequently depleted for CD4⁺ T cells. Abatacept or control treatment was started when 80 % of the mice showed signs of arthritis. Arthritis severity was monitored by clinical scoring of the paws, and anti-collagen antibody levels over time were determined by enzyme-linked immunosorbent assay.ResultsTreatment with abatacept in the absence of CD4⁺ T cells resulted in lower disease activity. This was associated with decreasing levels of collagen-specific IgG1 and IgG2a antibodies, whereas the antibody levels in control or CD4⁺ T cell–depleted mice increased over time.ConclusionsThese results show that abatacept decreased disease activity in the absence of CD4⁺ T cells, indicating that the mode of action of abatacept in established arthritis does not depend entirely on its effects on CD4⁺ T cell activation.