A NASP (N1/N2)-related protein, Sim3, binds CENP-A and is required for its deposition at fission yeast centromeres

A defining feature of centromeres is the presence of the histone H3 variant CENP-A(Cnp1). It is not known how CENP-A(Cnp1) is specifically delivered to, and assembled into, centromeric chromatin. Through a screen for factors involved in kinetochore integrity in fission yeast, we identified Sim3. Sim3 is homologous to known histone binding proteins NASP(Human) and N1/N2(Xenopus) and aligns with Hif1(S. cerevisiae), defining the SHNi-TPR family. Sim3 is distributed throughout the nucleoplasm, yet it associates with CENP-A(Cnp1) and also binds H3. Cells defective in Sim3 function have reduced levels of CENP-A(Cnp1) at centromeres (and increased H3) and display chromosome segregation defects. Sim3 is required to allow newly synthesized CENP-A(Cnp1) to accumulate at centromeres in S and G2 phase-arrested cells in a replication-independent mechanism. We propose that one function of Sim3 is to act as an escort that hands off CENP-A(Cnp1) to chromatin assembly factors, allowing its incorporation into centromeric chromatin.     

In vitro cultured peripheral blood mononuclear cells from patients with chronic schistosomiasis mansoni show immunomodulation of cyclin D1,2,3 in the presence of soluble egg antigens

Infection with Schistosoma mansoni induces a wide range of effects on the immune responses of the host. In the present study we investigated the influence of soluble egg antigens (SEA) on the cell cycle of peripheral blood mononuclear cells (PBMC) from infected and non-infected individuals with S. mansoni resident in an endemic area and blood donors from non-endemic area. The cell cycle, the expression of activation markers and cyclin D(+)(1,2,3) CD3(+) frequency was assessed by flow cytometry. Stimulation of PBMC from infected patients with SEA resulted in a lower frequency of CD3(+) T cells in S phase when compared with the non-infected group. In addition, infected patients presented a decrease of activation marker expression (CD69(+), HLA-DR(+) and CD28(-) on CD4(+) cells and CD25(+), HLA-DR(+) on CD8(+) cells). A reduced frequency was observed of cyclin D(1,2,3) expression in SEA-stimulated T cells from infected individuals when compared with those from the non-infected group. The decreased expression of activation markers and frequency of cyclin D(1,2,3) in T cells may result in arrest of T cells in the G(0)/G(1) phase of the cell cycle, thus explaining the down-regulation observed in chronic schistosomiasis.     

Seed Rain and Seed Dispersal Agents in Pure and Mixed Plantations of Native Trees and Abandoned Pastures at La Selva Biological Station, Costa Rica

Lack of seed dispersal can be an important obstacle to natural regeneration (NR) of degraded pastures in the humid tropics. Tree plantations can facilitate secondary forest succession by attracting seed dispersal agents from nearby forests. We studied seed rain and seed dispersal agents in 12–13 years old pure and mixed native tree plantations at La Selva Biological Station, Costa Rica from July to December 2004. Plantations of Balizia elegans (5,522), Dipteryx panamensis (2,263), and Jacaranda copaia (2,091) had the greatest total seed abundance; treatments with the least total seed abundance were Calophyllum brasiliense (56), nonplanted abandoned pasture control 2 (353), Mixed Species 2 (389), and control 1 (836). Plantations of J. copaia and Hyeronima alchorneoides had the greatest seed species richness density, whereas the lowest seed species richness was found in the control treatments. The NR plots had more seeds dispersed by wind, whereas in the plantations, the most important dispersal agents were birds and mammals. The most abundant seeds were those of Miconia spp. (14,492), Psychotria bracheata (2,252), and the Poaceae family (1,346), all species from early successional stages. Plantations of native species are effective in attracting seed dispersal agents and thus facilitating regeneration of degraded pasturelands in the region.     

Use of artificial substrata by introduced and cryptogenic marine species in Paranaguá Bay, southern Brazil

Ports are important locations for the introduction of marine species, while marinas and pontoons often serve as secondary habitats for these species. In a marina near Paranaguá Port, a major international port in southern Brazil, the encrusting community was studied to (i) identify possibly introduced species, and (ii) examine the use of artificial substrata by these species. Samples (20 x 20 cm) were taken from fibreglass floats (boardwalks and boat hulls) and concrete columns. A total of 85 species were found of which 50 were classified into three categories: four introduced, 33 cryptogenic and 13 native. The introduced species were the hydrozoan Garveia franciscana (on floats, boats and submerged concrete), the polychaete Polydora cornuta (more abundant on floats and submerged concrete) and the barnacles Amphibalanus reticulatus (equally abundant on the three substrata) and Striatobalanus amaryllis (only on floats and submerged concrete). Organisms were most abundant on floating boardwalks, while species richness and composition were similar to that on boat hulls (32 and 37, respectively), which are an important vector for intraregional transport. All substrata supported at least three of the four introduced, and many of the cryptogenic species. The proportion of introduced to the total number of species was greater than observed in other ports. This demonstrates that the introduction potential is great in Paranaguá Bay, especially considering that this study was restricted to one site and sampled only hard substrata. None of the introduced species has yet been identified as invasive, but all are generalists with respect to substratum, indicating their invasive potential. The ability to colonise stable concrete walls shows that they could also colonise the natural granite rocky substrata in the bay, and the ability to colonise floating surfaces indicate their capability of spreading in the region on the hulls of recreational boats.     

Style morphological diversity of some Asteraceae species from Argentina: systematic and functional implications

Stylar micromorphological diversity of 42 Asteraceae species from Argentina was analysed considering species phylogenetic membership and some floral reproductive functions (pollen presentation and pollen reception). In particular, the morphology and organisation of pollen presenter (sweeping hairs) and pollen receptive structures (stigmatic papillae) were described. Results showed that style morphology of the studied species is far more diverse than the categories previously established for Asteraceae, and that it is problematic to relate the sweeping-hair arrangement of species to the only three modes of pollen presentation described for the family, indicating that the hypothesised relationship could be more complex than was formerly thought. For all species with di- or trimorphic florets, the styles of female florets were more slender and without or with more reduced sweeping hairs than the styles of hermaphrodite florets, and divergences of sweeping hair arrangements and morphology were higher among phylogenetically related species. These results suggest that functional aspects of floral morphology seem to be more important than phylogenetic constraints as selective forces determining stylar pollen presentation structures. In contrast, stigmatic-area organisation as well as the morphology of stigmatic papillae remain identical between female and hermaphrodite florets and among phylogenetically related species. Thus, stigmatic papilla morphology seems to be a phylogenetically constrained character in the studied species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Systemic macrophage and neutrophil destruction by secondary necrosis induced by a bacterial exotoxin in a Gram-negative septicaemia

Bacterial modulation of phagocyte cell death is an emerging theme in pathogenesis. Here we describe the systemic destruction of macrophages and neutrophils by the Gram-negative Photobacterium damselae ssp. piscicida (Phdp) in fish pasteurellosis, a deadly systemic infection. Following experimental inoculation, Phdp spreads by bacteraemia and colonizes the organs, producing a septicaemic infection, and secretes the apoptogenic exotoxin AIP56 which is systemically disseminated. In experimental and natural pasteurellosis, destruction of macrophages and neutrophils by secondary necrosis following caspase-3-associated apoptosis was seen predominantly in the spleen, head kidney and gut lamina propria. Identical phagocyte destruction occurred after injection of rAIP56, but not of heat-inactivated rAIP56, or AIP56-negative Phdp strains, indicating that AIP56 is responsible for phagocyte destruction occurring in pasteurellosis. Active caspase-3 and active neutrophil elastase are present in the blood in advanced infection, indicating that phagocyte lysis by secondary necrosis is accompanied by release of tissue-damaging molecules. The AIP56-induced lysis of phagocytes represents a very efficient, self-amplifying etiopathogenic mechanism, because it results in two effects that operate in concert against the host, namely, evasion of the pathogen from a crucial defence mechanism through the destruction of both professional phagocytes, and release of tissue-damaging molecules. The induction by a bacterial exotoxin of in vivo systemic lysis of both professional phagocytes by secondary necrosis, now described for the first time, may represent an overlooked etiopathogenic mechanism operating in other infections of vertebrates.     

Y-chromosomal diversity in the population of Guinea-Bissau: a multiethnic perspective

Background  

The geographic and ethnolinguistic differentiation of many African Y-chromosomal lineages provides an opportunity to evaluate human migration episodes and admixture processes, in a pan-continental context. The analysis of the paternal genetic structure of Equatorial West Africans carried out to date leaves their origins and relationships unclear, and raises questions about the existence of major demographic phenomena analogous to the large-scale Bantu expansions. To address this, we have analysed the variation of 31 binary and 11 microsatellite markers on the non-recombining portion of the Y chromosome in Guinea-Bissau samples of diverse ethnic affiliations, some not studied before.