A cholesterol-rich emulsion (LDE) is taken up by malignant cells which over-express low-density lipoprotein (LDL) receptors and thus may be used as a carrier for drugs directed against neoplastic cells. In this study, we associated the antineoplastic agent paclitaxel to LDE and analysed the new formulation's incorporation efficiency, chemical and physical stability, cellular uptake and cytostatic activity against a neoplastic cell line and the acute toxicity to rats. A paclitaxel incorporation efficiency of approximately 75% was achieved when paclitaxel was mixed with LDE at a 6:1 lipid-to-drug molar ratio. The association of paclitaxel with LDE increased by 54% the mean diameter of the emulsion particles but did not damage the paclitaxel chemical structure as analysed by HPLC. Results from gradient ultracentrifugation and Sephadex G25 gel filtration indicated that the binding of the drug to the emulsion was stable. It was shown that the cellular uptake and the cytotoxic activity of LDE-paclitaxel by a neoplastic cell line (NCI-H292 cells) was indeed mediated by the LDL receptors. The antiproliferative activity of LDE-paclitaxel against NCI-H292 cells was less than that of a commercial paclitaxel preparation (50% inhibitory concentration, IC50 = 2.60 and 0.45 microM, respectively). This difference, however, can be ascribed to the in-vitro anti-proliferative activity of the commercial paclitaxel vehicle Cremophor EL; when Cremophor EL was added to the cultures with LDE-paclitaxel, the IC50 value was reduced to 0.45 microM, attaining that of the commercial paclitaxel preparation. The tolerability of LDE-paclitaxel in rats was remarkable, such that its lethal dose (LD50) was ten-fold greater than that of the commercial formulation (LD50 = 324 and 31.8 mg kg(-1), respectively). Therefore, LDE-paclitaxel association is stable and the cytostatic activity of the drug is preserved while its toxicity to rats is small. By diminishing the side effects and directing paclitaxel to neoplastic tissues, LDE may be useful as adjuvant in chemotherapy with this drug.

There are evidences that Giardia trophozoites contain and/or release proteolytic enzymes that may be implicated in pathogenesis of giardiasis. This report describes a preliminary characterization of the proteolytic activity in excretory/secretory (E/S) products of Giardia duodenalis trophozoites of an axenic Brazilian strain (BTU-11) and the reference strain Portland 1 (P1). The protease activity of E/S products in conditioned medium by trophozoites of each strain was analyzed using substrate (gelatin and collagen) impregnated SDS-PAGE and hemoglobin assay. The protease characterization was based on inhibition assays including synthetic inhibitors. Proteolytic products were detected in the conditioned medium by trophozoites of both assayed strains. In the gels containing copolymerized gelatin and collagen, E/S products promoted degradation of the substrates and the most evident proteolysis zones were distributed in the migration regions of 77 to 18 kDa and 145 to 18 kDa, respectively, in the patterns of gelatinolytic and collagenolytic activities. Degradation of hemoglobin was also observed, and the pattern of hydrolysis was similar in both E/S products assayed. Inhibition assays showed that the main proteolytic activity in both E/S products is due to cysteine proteases although the presence of serine proteases was also indicated, mainly in the hydrolysis of hemoglobin.

No abstract

The present investigation was undertaken to identify and characterize trophozoite proteases of five axenic strains of Giardia duodenalis isolated in Brazil and the reference strain Portland 1 isolated in the United States. Trophozoite cell lysates of each strain were analysed for the pattern of proteins and for proteolytic activity. Samples were tested in SDS-polyacrylamide gel electrophoresis for the protein profiles, and the detection of proteases in cell lysates was performed using substrate gel electrophoresis [gelatin, collagen, bovine serum albumin (BSA) and haemoglobin] and azocasein assays. Indeed, synthetic inhibitors were included in the assays to characterize the protease classes. Differences on the hydrolysis patterns of protein substrates were observed in relation to the substrate composition as much as the Giardia trophozoite strain. The substrate-containing gels revealed hydrolysis bands with molecular masses ranging from >97 to 20-15 kDa, and most zones were common to the five strains. However, some pronounced differences could be detected in the BTU-11 pattern. Azocasein was also degraded; however, depending on the lysate assayed, the degree of substrate degradation was variable. It was observed that inhibitory effects are substrate-dependent since the activity was predominantly due to cysteine proteases against gelatin, collagen, BSA and azocasein substrates and due to serine against haemoglobin. The presence of aspartic protease and aminopeptidase activity in the lysates was also indicated.

Hookworm infection stands out for its worldwide distribution and for its veterinary and public health relevance. Based on copromicroscopic examinations and polymerase chain reaction (PCR) amplification of the ITS1-5.8S-ITS2 region, we assessed, respectively, the prevalence of intestinal parasites and the identification of canine hookworm species in faeces recovered from 278 dogs living in households of an inland municipality of São Paulo State, Brazil. Intestinal parasites were found in 67.3% of dogs and hookworm infection was found at the highest prevalence rate (56.6%), followed by Toxocara canis (11.9%), Isospora spp. (11.9%), Giardia spp. (5.8%), Sarcocystis spp. (4.0%), 'Hammondia-like' (1.4%), Dipylidium caninum (1.1%) and Trichuris vulpis (0.7%). Of 158 samples positive for hookworm eggs, 106 (67.1%) were amplified by PCR and, of those, 88 (55.7%) were successfully sequenced for species identification. Single infections with Ancylostoma caninum and Ancylostoma braziliense were recorded in 61.4% and 12.5%, respectively, and mixed infections were found in 26.1%. The nucleotide sequences of both species showed high identity rates (98-100%) when compared with reference sequences. Although A. caninum was the most prevalent hookworm in the dogs assessed, the occurrence of both A. caninum and A. braziliense in single and/or mixed infections poses a potential risk for the local population in a low-income area, especially children, to acquire cutaneous larva migrans (CLM).