Susceptibility of Biomphalaria straminea (Dunker, 1848) from Serra da Mesa Dam,Goiás,Brazil to infection with three strains of Schistosoma mansoni Sambon, 1907

Ecological changes from water resources development projects often affect the epidemiology of water-associated diseases. In order to investigate the occurrence and distribution of freshwater snails of medical and veterinary importance in the area of influence of the Serra da Mesa Hydroelectric a survey has been performed since 1997 and revealed the occurrence of well-established populations of Biomphalaria straminea (Dunker, 1848) in the 8 municipalities surrounding the lake. Areas of epidemiologic risk for schistosomiasis were selected and studies of parasite-mollusc compatibility were undertaken using specimens from 19 populations of B. straminea and 3 strains (CM, EC and PB) originally isolated from B. straminea. Among 1,135 specimens used 15 became infected (infection index of 1.3%) and 8 populations were susceptible to the schistosome strains: B. straminea from Campinorte (Castel?o, susceptible to CM and EC strains, and Planeta Agua, EC strain), Colinas (Tocantinzinho river, CM and EC strains), Mina?u (Canabrava river, EC strain), Niquelandia (Codemin, CM and PB strains, and Almas river, CM strain), Urua?u (touristic area, PB strain) and Santa Rita do Novo Destino (Maranh?o river, CM and EC strains). These results, associated with marked social and ecological changes occurred, strongly suggest the possibility of B. straminea coming to act as a vector of schistosomiasis in the studied area.     

Dendritic cells (DC) promote natural killer (NK) cell functions: dynamics of the human DC/NK cell cross talk

Dendritic cells (DC) were originally found critical in the setting of cognate immune responses. We first demonstrated that DC can also induce mouse NK cell activation and NK cell dependent-antitumor effects in mice. Here we analyzed the dynamics between DC and NK cells in human in vitro model systems. In the absence of LPS, DC do not trigger resting NK cells. Conversely, in the presence of LPS, resting bulk NK cells interacting with DC acquire CD25 and CD69 surface expression, produce high levels of IFN-gamma and lyse DAUDI cells. On activated IL-2 dependent NK cell lines, regardless of their differentiation stage, DC maintain or enhance NK cell proliferation and effector functions in the absence of exogenous cytokines. While IL-12, IL-15 and IL-18 are not critical, a direct cell-to-cell contact is mandatory for NK activation by DC and required for optimal proliferation. These data imply that DC also modulate human NK cell innate effector functions.     

A newborn mouse model for the study of intestinal pathogenesis of shigellosis

Shigella infection is characterized by the induction of acute inflammation, which is responsible for the massive tissue destruction of the intestinal mucosa. A murine model would be a valuable tool for gaining a better understanding of the physiopathology of shigellosis and the host immune response to Shigella infection, but adult mice do not develop disease upon oral inoculation. We therefore attempted to develop a model of infection in newborn mice. Four-day-old mice inoculated with 50 microl of 5 x 10(9) invasive wild-type Shigella flexneri 5a were susceptible to bacterial infection, but mice inoculated with the non-invasive strain BS176 were not. Histologically, 4-day-old mice infected with the invasive strain presented intestinal lesions and inflammation similar to those described in patients with shigellosis. Moreover, cytokine and chemokine responses consistent with inflammation were observed. Lower bacterial inocula induced less severe intestinal damage. In contrast, 5-day-old mice inoculated with either the invasive or the non-invasive strain were not infected. We have thus established a mouse model that is suitable for the study of the pathogenesis of intestinal Shigella infection.     

Caution regarding the combined effects of extracellular matrices and nutrient media on cultured endothelial cells

To study the influence of smooth muscle cells (SMC) on endothelial cells (EC), different co-culture designs are available, including EC seeding on SMC extracellular matrix (ECM). We explored human umbilical vein endothelial cell (HUVEC) adhesion and proliferation on either in situ or coated ECM, elaborated by HUVECs or human arterial smooth muscle cells (HUASMCs), in the presence of different nutrient media containing varying amounts of fetal calf serum. Coating wells with HUVEC or HUASMC ECMs did not improve HUVEC adhesion 1 h after cell seeding, compared with uncoated wells. HUVEC adhesion on in situ HUVEC-ECM and HUASMC-ECM was significantly increased compared with uncoated wells. The substratum upon which cells are maintained was found to play a crucial role, in conjunction with the medium to which HUVECs are exposed for their proliferative response. These results stress the importance of selecting media in relation to the particular substratum, in order to avoid misinterpretation of data.     

In vitro effects of Clostridium perfringens type D epsilon toxin on water and ion transport in ovine and caprine intestine

Clostridium perfringens type D produces enterotoxaemia in sheep, goats and other animals. The disease is caused by C. perfringens epsilon toxin, and while enterotoxaemia in goats is usually characterized by enterocolitis, the disease in sheep is characterized by systemic lesions (such as lung and brain oedema) with minor and inconsistent changes observed in the intestine. A possible explanation for these differences is that epsilon toxin is more promptly absorbed by sheep than goat intestine. In an attempt to clarify this, we examined the in vitro effects of epsilon toxin on sheep and goat intestine. Pieces of intestinal mucosa from recently slaughtered animals were mounted in a modified Ussing-type chamber where net water flux (J(w)), short-circuit current (I(sc)) and tissue conductance (G(t)) were simultaneously recorded. After 70 min of incubation with epsilon toxin a reduction in absorptive J(w) and an increase in I(sc) and G(t) were observed in colonic tissues of both sheep and goats, but no alterations were registered in the ileum of either species. These in vitro results show that epsilon toxin affects the transport function of the colonic mucosa but it does not seem to produce any transport alteration in the ileum mucosa.     

Mechanical design of proteins studied by single-molecule force spectroscopy and protein engineering

Mechanical unfolding and refolding may regulate the molecular elasticity of modular proteins with mechanical functions. The development of the atomic force microscopy (AFM) has recently enabled the dynamic measurement of these processes at the single-molecule level. Protein engineering techniques allow the construction of homomeric polyproteins for the precise analysis of the mechanical unfolding of single domains. alpha-Helical domains are mechanically compliant, whereas beta-sandwich domains, particularly those that resist unfolding with backbone hydrogen bonds between strands perpendicular to the applied force, are more stable and appear frequently in proteins subject to mechanical forces. The mechanical stability of a domain seems to be determined by its hydrogen bonding pattern and is correlated with its kinetic stability rather than its thermodynamic stability. Force spectroscopy using AFM promises to elucidate the dynamic mechanical properties of a wide variety of proteins at the single molecule level and provide an important complement to other structural and dynamic techniques (e.g., X-ray crystallography, NMR spectroscopy, patch-clamp).     

Palm heart harvesting in the Brazilian Atlantic forest: changes in industry structure and the illegal trade

1. Until the late 1960s, Euterpe edulis was the most important edible palm species in the Brazilian markets. Since then, overharvesting of natural stands and the limited scope of plantations have caused the industry to shift to the multistemmed E. oleracea from the Amazon river estuary.
2. As a result of the relocation of the industry, the structure of the palm harvesting industry has changed and illegal trade has continued to exploit the remaining natural stands of E. edulis .
3. It is suggested that, to avoid the total harvesting of E. edulis and to achieve sustainable management of the palm heart, it will be necessary to diversify the local economy, create incentives for small land owners to improve their management practices, while keeping their competitiveness against the illegal trade, create the incentive of new sources of palm hearts and create a 'green stamping' for management palms.
4. Transformation of the illegal structure of the palm heart industry is probably the only solution to avoid the total depletion of the wild stands of E. edulis .