A Novel Porous Diamond - Titanium Biomaterial: Structure, Microstructure, Physico-Mechanical Properties and Biocompatibility

ABSTRACT With the aim of introducing permanent prostheses with main properties equivalent to cortical human bone, Ti-diamond composites were processed through powder metallurgy. Grade 1 titanium and mixtures of Ti powder with 2%, 5% and 10 wt% diamond were compacted at 100MPa, and then sintered at 1250°C/2hr/10-6mbar. Sintered samples were studied in the point of view of their microstructures, structures, yield strength and elastic modulus. The results showed that the best addition of diamonds was 2 wt%, which led to a uniform porosity, yield strength of 370MPa and elastic modulus of 13.9 GPa. Samples of Ti and Ti-2% diamond were subjected to in vitro cytotoxicity test, using cultures of VERO cells, and it resulted in a biocompatible and nontoxic composite material.

Infection of Aedes aegypti (Diptera: Culicidae) larvae and Adults by the Entomopathogenic Fungus Metarhizium anisopliae (Metschn.) Sorokin.

Aims: The dengue vector Aedes aegypti is currently a target for control by entomopathogenic fungi. We have previously shown the susceptibility of both larvae and adult A. aegypti to fungal infection by Metarhizium anisopliae and strategies are being developed for control of both stages in the field. Study Design: Few studies have been carried out on the early stages of the infection process of entomopathogenic fungi in mosquitoes, especially in the case of adult infection. Place and Duration of Study: Department of Entomology and Plant Pathology and the Department of Cell Biology at the State University of North Fluminense. May 2010 – July 2011. Methodology: Conidia were obtained for all experiments by culturing M. anisopliae in SDA. Conidial suspensions were standardized by serial dilution following quantification using a hemocytometer. Larvae were infected by addition of conidial suspensions to the water in which they were being maintained. Larvae were removed at specific time intervals for observation using a scanning electron microscope. Adult A. aegypti were infected by spraying with conidial suspensions at a concentration previously established. Following inoculation, mosquitoes were maintained in cages and cohorts were removed for observation using a scanning electron microscopy at specific time intervals. Results: The initial stage of the infection process of larvae and adults (females) was described here. Conidia were found to attach to specific regions of the larvae, associated with thoracic hairs. Saprophytic fungal development was observed on the integument of larvae 36 hours after exposure to the fungus. For infection of adults, adhesion and germination of conidia were only observed on the thorax. Conclusion: The pattern of fungal infection of mosquito larvae was different to that previously documented in the literature. The integument of the larvae was found to be a favorable environment for fungal development. This did not appear to be the case in colonization of the adult integument, which was a more hostile environment for the fungus. However, the microbial control of adult mosquitoes is thought to be more promising than that of larvae due to reduced half-life of the conidia in aqueous environments.

Brazilian contribution for a better knowledge on the biology of Toxoplasma gondii

Historically, scientists in Brazil has significantly contributed to the biology, cultivation and structural organization of the pathogenic protozoan Toxoplasma gondiiand its interaction with host cells, starting with the description of the protozoan by Splendore in 1908. The intracellular and extracellular corpuscoli observed in rabbits, corresponded to what we now as tachyzoites. Later on, a pioneering method to grow T. gondii in tissue cultures was developed by Guimarães and Meyer, 1942. They also observed for the first time T. gondii by transmission electron microscopy and made the initial description of the cytoskeleton of T. gondii by observing negatively stained cells. In the 1980's, the relation of the cytoskeleton with the sub-pellicular microtubules was reveled by freeze-fracture. More recently, several Brazilian groups have analyzed in detail basic aspects of the early interaction of the protozoan with the host cell, such as the role of protein phosphorylation, transfer of host cell surface components to the protozoan and genesis and organization of the parasitophorous vacuole. Tachyzoites strategically inhibit nitric oxide production during active invasion of activated macrophages. In vitro studies on the sexual cycle of T. gondii using primary cultures of cat enterocytes and the egress from host cells are being carried out. Perspectives are that the contribution of Brazilian science to the knowledge on T. gondii biology will continue to flourish in years to come.

Programmed cell death in Trypanosoma cruzi induced by Bothrops jararaca venom

Cells die through a programmed process or accidental death, know as apoptosis or necrosis, respectively. Bothrops jararaca is a snake whose venom inhibits the growth of Trypanosoma cruzi epimastigote forms causing mitochondrion swelling and cell death. The aim of the present work was to determine the type of death induced in epimastigotes of T. cruzi by this venom. Parasite growth was inhibited after venom treatment, and 50 percent growth inhibition was obtained with 10 æg/ml. Ultrastructural observations confirmed mitochondrion swelling and kinetoplast disorganization. Furthermore, cytoplasmic condensation, loss of mitochondrion membrane potential, time-dependent increase in phosphatidylserine exposure at the outer leaflet plasma membrane followed by permeabilization, activation of caspase like protein and DNA fragmentation were observed in epimastigotes throughout a 24 h period of venom treatment. Taken together, these results indicate that the stress induced in epimastigote by this venom, triggers a programmed cell death process, similar to metazoan apoptosis, which leads to parasite death.