Search results for "Protozoa"
showing 10 items of 222 documents
Cytotoxicity and antileishmanial activity of Annona muricata pericarp
2000
Abstract Hexane, ethyl acetate and methanol extracts of Annona muricata pericarp were tested in vitro against Leishmania braziliensis and L. panamensis promastigotes, and against cell line U-937. The ethyl acetate extract was more active than the other extracts and even of Glucantime® used as reference substance. Its fractionation led to the isolation of three acetogenins — annonacin, annonacin A and annomuricin A.
Binding and activation of human and mouse complement by Cryptosporidium parvum (Apicomplexa) and susceptibility of C1q- and MBL-deficient mice to inf…
2008
Cryptosporidium parvum is a protozoan parasite (Apicomplexa) that causes gastrointestinal disease in animals and humans. Whereas immunocompetent hosts can limit the infection within 1 or 2 weeks, immunocompromised individuals develop a chronic, life-threatening disease. The importance of the adaptive cellular immune response, with CD4+ T-lymphocytes being the major players, has been clearly demonstrated. Several non-adaptive immune mechanisms have been suggested to contribute to the host defence, such as interferon-gamma (IFN-gamma) from NK cells, certain chemokines, beta-defensins and pro-inflammatory cytokines, but the influence of the complement systems has been less well studied. We ana…
Advances in the understanding of mast cell function
2008
Mast cells were formerly thought to contribute mainly to, sometimes even, fatal allergic reactions through the release of biologically highly active cytokines, chemokines, lipid mediators, proteases and biogenic amines. This potential harmful response is triggered by crosslinking of cell-bound IgE by the respective allergen. This review updates our current understanding of the emerging roles of mast cells with an emphasis on their relevance in protective host immunity. The activation of mast cells independently of Immunoglobulin E can lead to the initiation of fast inflammatory reactions, which were shown to be life-saving in murine models of bacterial infections. Besides their critical fun…
Chlamydomonas reinhardtii in the landscape of pigments.
2004
▪ Abstract This review focuses on the biosynthesis of pigments in the unicellular alga Chlamydomonas reinhardtii and their physiological and regulatory functions in the context of information gathered from studies of other photosynthetic organisms. C. reinhardtii is serving as an important model organism for studies of photosynthesis and the pigments associated with the photosynthetic apparatus. Despite extensive information pertaining to the biosynthetic pathways critical for making chlorophylls and carotenoids, we are just beginning to understand the control of these pathways, the coordination between pigment and apoprotein synthesis, and the interactions between the activities of these…
Transition from Protozoa to Metazoa: An Experimental Approach
1998
Until recently, stromatolites were thought to be the oldest fossils on earth that were very abundant 2000 to 3000 Ma (million years) ago (Walter 1994). Recently, the biological origin of these fossils has been questioned (Walter 1996). The universal phylogenetic tree exhibits a tripartite division of the living world into Bacteria (“eubacterial”), Archaea (“archebacterial”), and Eucarya [“eukaryotic” (Woese 1987; Woese et al. 1991)]. Based on comparisons of amino acid (aa) sequence data from enzymes, it has been proposed that the common ancestor of prokaryotes and eukaryotes lived about 2000 Ma ago (Doolittle et al. 1996). Phylogenetic analysis of the 70kDa heat-shock proteins suggested tha…
Endogenous fluctuations of DNA topology in the chloroplast of Chlamydomonas reinhardtii.
1998
DNA supercoiling in the chloroplast of the unicellular green alga Chlamydomonas reinhardtii was found to change with a diurnal rhythm in cells growing in alternating 12-h dark-12-h light periods. Highest and lowest DNA superhelicities occurred at the beginning and towards the end of the 12-h light periods, respectively. The fluctuations in DNA supercoiling occurred concurrently and in the same direction in two separate parts of the chloroplast genome, one containing the genes psaB, rbcL, and atpA and the other containing the atpB gene. Fluctuations were not confined to transcribed DNA regions, indicating simultaneous changes in DNA conformation all over the chloroplast genome. Because the d…
Ancistectorine D, a naphthylisoquinoline alkaloid with antiprotozoal and antileukemic activities, and further 5,8'- and 7,1'-linked metabolites from …
2016
From the twigs and stems of the Chinese liana Ancistrocladus tectorius (Ancistrocladaceae), two new 5,8'-coupled naphthylisoquinolines, ancistectorine D (5) and its 6-O-demethyl derivative 6, were isolated, along with two new 7,1'-linked alkaloids, 6-O-methylancistectorine B1 (7) and ancistectorine B2 (8). Two further compounds, ancistroealaine A (4) and 6-O-demethyl-8-O-methyl-7-epi-ancistrobrevine D (10), already known from related Asian and African Ancistrocladus species, were discovered for the first time in A. tectorius. The structure elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (circular di…
Strategies for improving production and purification of a recombinant protein: rP30 of Toxoplasma gondii expressed in the yeast Schizosaccharomyces p…
2007
Abstract Many problems concerned with the production and the purification of recombinant proteins must be addressed prior to launching an industrial production process. Among these problems, attention is focused on low-level expression that complicates the purification step and can jeopardise the process. The expression of a membrane protein, rP30, of Toxoplasma gondii in the yeast Schizosaccharomyces pombe led to a secretion of only 0.5 μg ml−1. In order to obtain a sufficient quantity for biochemical characterization and evaluation in vitro diagnostic test development, strategies for both production and purification had to be optimized. First, the influence of four nitrogen sources (three…
Evidence for Conformational Mechanism on the Binding of TgMIC4 with β-Galactose-Containing Carbohydrate Ligand
2015
A deeper understanding of the role of sialic/desialylated groups during TgMIC4-glycoproteins interactions has importance to better clarify the odd process of host cell invasion by members of the apicomplexan phylum. Within this context, we evaluated the interaction established by recombinant TgMIC4 (the whole molecule) with sialylated (bovine fetuin) and desialylated (asialofetuin) glycoproteins by using functionalized quartz crystal microbalance with dissipation monitoring (QCM-D). A suitable receptive surface containing recombinant TgMIC4 for monitoring β-galactose-containing carbohydrate ligand (limit of quantification ∼ 40 μM) was designed and used as biomolecular recognition platform t…
Ultrastructure, fractionation and biochemical analysis of Cryptosporidium parvum sporozoites.
1999
Abstract Sporozoites of the apicomplexan parasite Cryptosporidium parvum were subjected to cell disruption and subcellular fractionation using a sucrose density step gradient. With this procedure, highly enriched preparations of the parasite membrane, the micronemes, dense granules and amylopectin granules were produced. No separate fraction containing rhoptries was obtained, however this organelle was found in defined fractions of the gradient, still associated with the apical tip of the sporozoites. Using negative staining, the internal structure of the micronemes was revealed by transmission electron microscopy. Micronemes and dense granules showed characteristic protein compositions by …