Study of the mechanism of vanadate inhibition of the dynein cross-bridge cycle in sea urchin sperm flagella

The effect of vanadate on the ATP-induced disruption of trypsin-treated axonemes and the ATP-induced straightening of rigor wave preparations of sea urchin sperm was investigated. Addition of ATP to a suspension of trypsin-treated axonemes results in a rapid decrease in turbidity (optical density measured at 350 nm) concomitant with the disruption of the axonemes by sliding between microtubules to form tangles of connected doublet microtubules (Summers and Gibbons, 1971; Sale and Satir, 1977). For axonemes digested to approximately 93 percent of their initial turbidity, 5 {muM} vanadate completely inhibits the ATP-induced decrease in turbidity and the axonemes maintain their structural integrity. However, with axonemes digested to approximately 80 percent of their initial turbidity, vanadate fails to inhibit the ATP-induced decrease in turbidity and the ATP-induced structural disruption of axonemes, even when the vanadate concentration is raised as high as 100 μm. For such axonemes digested to 80 percent of their initial turbidity, the form of ATP-induced structural changes, in the presence of 25 μM vanadate, was observed by dark-field light microscopy and revealed that the axonemes become disrupted into curved, isolated doublet microtubules, small groups of doublet microtubules, and “banana peel” structures in which tubules have peeled back from the axoneme. Addition of 5 μM ATP to rigor wave sperm, which were prepared by abrupt removal of ATP from reactivated sperm, causes straightening of the rigor waves within 1 min, and addition of more than 10 μM ATP causes resumption of flagellar beating. Addition of 40 μM vanadate to the rigor wave sperm does not inhibit straightening of the rigor waves of 2 μM-1 mM ATP, although oscillatory beating is completely inhibited. These results suggest that vanadate inhibits the mechanochemical cycle of dyein at a step subsequent to the MgATP(2-)-induced release of the bridged dynein arms.     

Compositional dissimilarity patterns of reptiles and amphibians in insular systems around the world

Several studies have shown that taxa with poor dispersal ability have a higher level of compositional dissimilarity than good dispersers. However, compositional dissimilarity patterns between islands with respect to dispersal ability of taxa have never been investigated before. In this study, we investigated compositional dissimilarity patterns of three taxonomic groups, namely amphibians, lizards, and snakes, differing in their dispersal abilities, in various insular systems around the world. We compiled presence–absence matrices, based on which we calculated several metacommunity indices to check for differences among taxonomic groups and island types (oceanic and continental shelf) using classical statistical tests and generalized linear mixed-effects models. According to our results, compositional dissimilarity was positively affected by the isolation of the insular system, in accordance to theory. In particular, oceanic systems were characterized by a high level of compositional dissimilarity between islands and subsequently by a low level of nestedness. SIEs may be generating these patterns causing distortions from expected levels of nestedness. Similar to our predictions, compositional dissimilarity patterns were also dependent on taxon-specific dispersal ability, with good dispersers showing lower levels of between-island compositional dissimilarity than poor dispersers in continental shelf systems. However, this pattern was not observed in oceanic systems. In conclusion, compositional dissimilarity in insular systems is dependent on both taxon and island type.     

Immunopositivity for Siglec-15 in gastric cancer and its association with clinical and pathological parameters

The sialic acid-binding immunoglobulin-type lectin Siglec-15 is a promising target for cancer immunotherapy in several tumor types. The present study aimed to investigate Siglec-15 expression in gastric cancer (GC) patient tissues and to evaluate its clinical value. Siglec-15 expression was evaluated by immunohistochemistry in 71 patients. Siglec-15 staining was observed in tumor cells of 53 (74.64%) patients, with significant association with histologic classification and angiolymphatic invasion (p<0.05). Immunohistochemistry analysis also detected Siglec-15 in tumor-associated stroma cells (macrophages/myeloid cells). There was no significant association with outcome parameters. Siglec-15 expression in well differentiated histological GC tissues and in the tumor microenvironment are potential targets to be further investigated as a novel prognostic factor for GC.Key words: Siglec, sialic acid, immunohistochemistry, clinical-pathological analyses     

Planktonic food web in marine mesocosms in the Eastern Mediterranean: bottom-up or top-down regulation?

A mesocosm experiment was conducted in order to studythe structure of the planktonic food web. The dynamicsof pico-, nano- and microplankton populations werefollowed during 40 days in four large (40 m³)enclosures. In three tanks a gradient of addednutrients (nitrogen and phosphorus) was applied, whilea fourth tank was used as a control. On day 14, thetop predator (sea bream Sparus aurata larvae)was introduced into the tanks and part of the watercolumn in each tank was isolated in a plastic bagwithout fish larvae, to act as a control forpredation. Physical parameters, chlorophyll aand nutrient concentrations, as well as planktonconcentrations were monitored. A diatom bloom wasobserved in all four tanks, in the first phase endingwith silicate depletion. Flagellate and dinoflagellateabundance subsequently increased, these organismsbeing limited by zooplankton grazing. The zooplanktonpopulations were controlled by both resources (mostlyflagellates) and predation (by fish larvae) asindicated by the results of the control experiments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Decreased serum interleukin 27 in Brazilian systemic lupus erythematosus patients

The immunological role of interleukin 27 has been reported in various inflammatory diseases, but its importance in systemic lupus erythematosus pathogenesis is not completely established. The aim of this study was to evaluate serum levels of IL-27 in SLE patients and its correlation with clinical manifestations and disease activity. IL-27 levels were assessed in 70 SLE patients and 30 healthy controls by ELISA. Clinical and laboratory parameters were recorded. Statistic analyzes were performed by Graph Prism 3.02 software. The IL-27 serum levels were significantly decreased in SLE patients compared with controls (mean 899.92 and 1,531.22 pg/ml, P = 0.0005). There was a correlation between IL-27 levels and C3 levels (P = 0.004). Nevertheless, there was no association of serum IL-27 levels with disease activity evaluated by SLEDAI score (P = 0.9605). No significant difference was found regarding IL-27 levels between SLE patients with and without nephritis, haematuria, proteinuria and positive anti-dsDNA. Correlation analysis between serum IL-27 levels and SLEDAI, SLICC, proteinuria levels, C4 and CH50 levels also showed no association. These data demonstrated decreased serum levels of IL-27 in SLE patients but further studies are needed to clarify the precise role of this cytokine and its potential use as therapeutic target.     

Natural vs. mariculture induced variability in nutrients and plankton in the eastern Mediterranean

The water column in three Mediterranean fish farms was investigated in terms of physical, chemical and biological characteristics. A significant increase in concentrations of phosphate and ammonium was detected within the cages over the control site in one of the farms but without any significant effect on chlorophyll concentration. Analysis of variation within the data set identified location and season as the major factors of variability in most of the variables examined except phosphate and ammonium for which variability induced by fish farming seemed to be of major importance. Plankton abundance for the major taxonomic groups (diatoms, flagellates, dinoflagellates and ciliates), microplankton species diversity and community structure were also determined by the effects of season and location rather than by fish farming.     

Between-island compositional dissimilarity of avian communities

Compositional dissimilarity patterns of biotic communities can vary among different types of insular systems and among taxa with different dispersal abilities. In this work we examined compositional dissimilarity patterns of four avian groups, namely birds of prey, waterbirds, seabirds and landbirds, in various insular systems around the world. Compositional dissimilarity of avian communities was calculated for 25 presence-absence matrices compiled from the literature. We used generalized linear mixed-effects models to check for differences in between-island compositional dissimilarity among the aforementioned avian groups that differ in their dispersal abilities, as well as between two different types of insular systems, oceanic and continental shelf. In agreement with our original hypothesis, landbirds which have relatively poorer dispersal abilities than birds of prey and waterbirds, exhibit higher between-island compositional dissimilarity compared to these two avian groups. On the contrary, seabirds present a deviation from the expected pattern, since they show higher between-island compositional dissimilarity compared to landbirds, even though they also have better dispersal abilities than landbirds, which can be explained by the relatively irregular occurrence of proper breeding habitats among islands for this avian group. Island type (oceanic or continental shelf) does not appear to affect between-island compositional dissimilarity of avian communities. Distance, area and elevation differences among islands are positively related to compositional dissimilarity. In conclusion, compositional dissimilarity of avian communities differs between avian groups but cannot always be associated with differences in the dispersal ability among these groups.