In vitro activity of Camellia sinensis (green tea) against trophozoites and cysts of Acanthamoeba castellanii

The effect of Camellia sinensis (green tea) on the growth of Acanthamoeba castellanii trophozoites was examined using a microplate based-Sulforhodamine B (SRB) assay. C. sinensis hot and cold brews at 75% and 100% concentrations significantly inhibited the growth of trophozoites. We also examined the structural alterations in C. sinensis-treated trophozoites using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This analysis showed that C. sinensis compromised the cell membrane integrity and caused progressive destruction of trophozoites. C. sinensis also significantly inhibited the parasite's ability to form cysts in a dose-dependent manner and reduced the rate of excystation from cysts to trophozoites. C. sinensis exhibited low cytotoxic effects on primary corneal stromal cells. However, cytotoxicity was more pronounced in SV40-immortalized corneal epithelial cells. Chromatographic analysis showed that both hot and cold C. sinensis brews contained the same number and type of chemical compounds. This work demonstrated that C. sinensis has anti-acanthamoebic activity against trophozoite and cystic forms of A. castellanii. Further studies are warranted to identify the exact substances in C. sinensis that have the most potent anti-acanthamoebic effect.

Balantioides coli: morphological and ultrastructural characteristics of pig and non-human primate isolates

Balantioides coli is a ciliated protozoon that inhabits the intestine of pigs, non-human primates and humans. Light microscopy studies have described over 50 species of the genus Balantioides but their validity is in doubt. Due to the limited information about this genus, this study is aimed to identify morphological characteristics of Balantioides coli isolated using fluorescence microscopy and both scanning (SEM) and transmission electron microscopy (TEM). Trophozoites isolated from the feces of pig and macaque were washed and subjected to centrifugation. These cells were fixed with paraformaldehyde for immunofluorescence. Other aliquots of these trophozoites were fixed with glutaraldehyde, post fixed with osmium tetroxide and processed for SEM and TEM. Immunofluorescence studies revealed microtubules with a longitudinal distribution to the main axis of the parasite and in the constitution of cilia. SEM demonstrated a high concentration of cilia covering the oral apparatus and a poor presence of such structures in cytopyge. TEM revealed in the plasma membrane, several associated structures were observed to delineate the cellular cortex and mucocysts. The cytoskeleton of the oral region was observed in detail and had an organization pattern consisting of microtubules, which formed files and nematodesmal networks. Organelles such as hydrogenosomes like and peroxisomes were observed close to the cortex. Macronuclei were observed, but structures that were consistent with micronuclei were not identified. Ultrastructural morphological analysis of isolates confirms its similarity to Balantioides coli. In this study were identified structures that had not yet been described, such as hydrogenosomes like and cytoskeletal structures.

Acanthamoeba castellanii is not be an adequate model to study human adenovirus interactions with macrophagic cells

Free living amoebae (FLA) including Acanthamoeba castellanii, are protozoa that feed on different microorganisms including viruses. These microorganisms show remarkable similarities with macrophages in cellular structures, physiology or ability to phagocyte preys, and some authors have therefore wondered whether Acanthamoeba and macrophages are evolutionary related. It has been considered that this amoeba may be an in vitro model to investigate relationships between pathogens and macrophagic cells. So, we intended in this study to compare the interactions between a human adenovirus strain and A. castellanii or THP-1 macrophagic cells. The results of molecular and microscopy techniques following co-cultures experiments have shown that the presence of the adenovirus decreased the viability of macrophages, while it has no effect on amoebic viability. On another hand, the viral replication occurred only in macrophages. These results showed that this amoebal model is not relevant to explore the relationships between adenoviruses and macrophages in in vitro experiments.

An Interactome-Centered Protein Discovery Approach Reveals Novel Components Involved in Mitosome Function and Homeostasis in Giardia lamblia

Protozoan parasites of the genus Giardia are highly prevalent globally, and infect a wide range of vertebrate hosts including humans, with proliferation and pathology restricted to the small intestine. This narrow ecological specialization entailed extensive structural and functional adaptations during host-parasite co-evolution. An example is the streamlined mitosomal proteome with iron-sulphur protein maturation as the only biochemical pathway clearly associated with this organelle. Here, we applied techniques in microscopy and protein biochemistry to investigate the mitosomal membrane proteome in association to mitosome homeostasis. Live cell imaging revealed a highly immobilized array of 30–40 physically distinct mitosome organelles in trophozoites. We provide direct evidence for the single giardial dynamin-related protein as a contributor to mitosomal morphogenesis and homeostasis. To overcome inherent limitations that have hitherto severely hampered the characterization of these unique organelles we applied a novel interaction-based proteome discovery strategy using forward and reverse protein co-immunoprecipitation. This allowed generation of organelle proteome data strictly in a protein-protein interaction context. We built an initial Tom40-centered outer membrane interactome by co-immunoprecipitation experiments, identifying small GTPases, factors with dual mitosome and endoplasmic reticulum (ER) distribution, as well as novel matrix proteins. Through iterative expansion of this protein-protein interaction network, we were able to i) significantly extend this interaction-based mitosomal proteome to include other membrane-associated proteins with possible roles in mitosome morphogenesis and connection to other subcellular compartments, and ii) identify novel matrix proteins which may shed light on mitosome-associated metabolic functions other than Fe-S cluster biogenesis. Functional analysis also revealed conceptual conservation of protein translocation despite the massive divergence and reduction of protein import machinery in Giardia mitosomes.

Organelles with endosymbiotic origin are present in virtually all extant eukaryotes and have undergone considerable remodeling during > 1 billion years of evolution. Highly diverged organelles such as mitosomes or plastids in some parasitic protozoa are the product of extensive secondary reduction. They are sufficiently unique to generate interest as targets for pharmacological intervention, in addition to providing a rich ground for evolutionary cell biologists. The so-called mitochondria-related organelles (MROs) comprise mitosomes and hydrogenosomes, with the former having lost any role in energy metabolism along with the organelle genome. The mitosomes of the intestinal pathogen Giardia lamblia are the most highly reduced MROs known and have proven difficult to investigate because of their extreme divergence and their unique biophysical properties. Here, we implemented a novel strategy aimed at systematic analysis of the organelle proteome by iterative expansion of a protein-protein interaction network. We combined serial forward and reverse co-immunoprecipitations with mass spectrometry analysis, data mining, and validation by subcellular localization and/or functional analysis to generate an interactome network centered on a giardial Tom40 homolog. This iterative ab initio proteome reconstruction provided protein-protein interaction data in addition to identifying novel organelle proteins and functions. Building on this data we generated information on organelle replication, mitosome morphogenesis and organelle dynamics in living cells.

Morphological diversity of Paramoeba perurans trophozoites and their interaction with Atlantic salmon, Salmo salar L., gills

Amoebic gill disease (AGD) caused by the ectoparasite Paramoeba perurans affects several cultured marine fish species worldwide. In this study, the morphology and ultrastructure of P. perurans in vitro and in vivo was investigated using scanning and transmission electron microscopy (SEM and TEM, respectively). Amoebae cultures contained several different morphologies ranging from a distinct rounded cell structure and polymorphic cells with pseudopodia of different lengths and shapes. SEM studies of the gills of AGD-affected Atlantic salmon, Salmo salar L., revealed the presence of enlarged swellings in affected gill filaments and fusion of adjacent lamellae. Spherical amoebae appeared to embed within the epithelium, and subsequently leave hemispherical indentations with visible fenestrations in the basolateral surface following their departure. These fenestrated structures corresponded to the presence of pseudopodia which could be seen by TEM to penetrate into the epithelium. The membrane-membrane interface contained an amorphous and slightly fibrous matrix. This suggests the existence of cellular glycocalyces and a role for extracellular products in mediating pathological changes in amoebic gill disease.

ANTI-AMEBIC ACTIVITY OF DIOSGENIN ON NAEGLERIA FOWLERI TROPHOZOITES

The aim of this study was to investigate the activity of diosgenin against Naegleria fowleri trophozoites at the cellular and molecular levels. Diosgenin (100 μg/ml; 241.2 μM) had a 100% inhibitory effect on N. fowleri trophozoites (5 x 10(5) cell/ml). Scanning electron micrograph revealed diosgenin decreased the number of sucker-like apparatuses and food cup formation among N. fowleri trophozoites at 3 and 6 hours post-exposure, respectively. Diosgenin down-regulated the nf cysteine protease gene expression of N. fowleri trophozoites at 6 and 12 hours post-exposure. The toxicity to mammalian cells caused by diosgenin at therapeutic dose was less than amphotericin B, the current drug used to treat N. fowleri infections. Our findings suggest diosgenin has activity against the surface membrane and the nf cysteine pro tease of N. fowleri trophozoites. However, the other mechanisms of action of diosgenin against N. fowleri trophozoites require further exploration.

Effect of synthetic antimicrobial peptides on Naegleria fowleri trophozoites

We evaluated the effect of tritrpticin, lactoferrin, killer decapeptide and scrambled peptide in vitro against Naegleria fowleri trophozoites compared with amphotericin B. Tritrpticin (100 microg/ml) caused apoptosis of N. fowleri trophozoites (2x10(5) cells/ml), while lactoferrin, killer decapeptide and scrambled peptide did not. On Gormori trichrome staining, tritrpticin affected the elasticity of the surface membrane and reduced the size of the nuclei of N. fowleri trophozoites. The ultrastructure surface membrane and food cup formation of the trophozoites were 100% inhibited. These results are consistent with inhibition of the nfa1, Mp2CL5 of the treated trophozoite, which plays a role in food cup formation. Tritrpticin 100 microg/ml was not toxic against SK-N-MC cells. Our findings suggest tritrpticin has activity against the surface membrane and nfa1 and Mp2CL5 of N. fowleri trophozoites and could be developed as a potential therapeutic agent.

Effects of metronidazole analogues on Giardia lamblia: experimental infection and cell organization

The chemotherapeutic agents used for the treatment of giardiasis are often associated with adverse side effects and are refractory cases, due to the development of resistant parasites. Therefore the search for new drugs is required. We have previously reported the giardicidal effects of metronidazole (MTZ) and its analogues (MTZ-Ms, MTZ-Br, MTZ-N(3), and MTZ-I) on the trophozoites of Giardia lamblia. Now we evaluated the activity of some giardicidal MTZ analogues in experimental infections in gerbils and its effects on the morphology and ultrastructural organization of Giardia. The giardicidal activity in experimental infections showed ED(50) values significantly lower for MTZ-I and MTZ-Br when compared to MTZ. Transmission electron microscopy was employed to approach the mechanism(s) of action of MTZ analogues upon the protozoan. MTZ analogues were more active than MTZ in changing significantly the morphology and ultrastructure of the parasite. The analogues affected parasite cell vesicle trafficking, autophagy, and triggered differentiation into cysts. These results coupled with the excellent giardicidal activity and lower toxicity demonstrate that these nitroimidazole derivates may be important therapeutic alternatives for combating giardiasis. In addition, our results suggest a therapeutic advantage in obtaining synthetic metronidazole analogues for screening of activities against other infectious agents.

High sensitivity of Giardia duodenalis to tetrahydrolipstatin (orlistat) in vitro

Giardiasis, a gastrointestinal disease caused by Giardia duodenalis, is currently treated mainly with nitroimidazoles, primarily metronidazole (MTZ). Treatment failure rates of up to 20 percent reflect the compelling need for alternative treatment options. Here, we investigated whether orlistat, a drug approved to treat obesity, represents a potential therapeutic agent against giardiasis. We compared the growth inhibitory effects of orlistat and MTZ on a long-term in vitro culture adapted G. duodenalis strain, WB-C6, and on a new isolate, 14-03/F7, from a patient refractory to MTZ treatment using a resazurin assay. The giardiacidal concentration of the drugs and their combined in vitro efficacy was determined by median-effect analysis. Morphological changes after treatment were analysed by light and electron microscopy. Orlistat inhibited the in vitro growth of G. duodenalis at low micromolar concentrations, with isolate 14-03/F7 (IC50_24h = 2.8 µM) being more sensitive than WB-C6 (IC50_24h = 6.2 µM). The effect was significantly more potent compared to MTZ (IC50_24h = 4.3 µM and 11.0 µM, respectively) and led to specific undulated morphological alterations on the parasite surface. The giardiacidal concentration of orlistat was >14 µM for 14-03/F7 and >43 µM for WB-C6, respectively. Importantly, the combination of both drugs revealed no interaction on their inhibitory effects. We demonstrate that orlistat is a potent inhibitor of G. duodenalis growth in vitro and kills parasites at concentrations achievable in the gut by approved treatment regimens for obesity. We therefore propose to investigate orlistat in controlled clinical studies as a new drug in giardiasis.

Scanning electron microscopic study of trophozoite and cyst stages of Naegleria fowleri

Whole trophozoites and cysts of axenically cultivated Naegleria fowleri were prepared for study of their surface morphology by scanning electron microscopy (SEM). Trophozoites and cyst stages were studied from Chang's culture media. Some trophozoites were examined after animal inoculation and brain isolation to compare the changes in surface features. Photomicrographs of freeze-dried and critical point-dried organisms fixed with glutaraldehyde were presented along with views of both isolates of trophozoites to compare the surface features. SEM revealed the surface of trophozoites to be undulating, wrinkled and covered at irregular intervals by protruding vesicles. There were also surface extensions which were long and thin in brain isolates which may help in the contact and cytolysis of host cells at some distance from the trophozoite. Some cysts appeared wrinkled while others smooth, and empty cysts were also seen with many pores on the surface.

Imaging and analysis of the microtubule cytoskeleton in giardia

Giardia intestinalis, a common parasitic protist, possesses a complex microtubule cytoskeleton critical for cellular function and transitioning between the cyst and trophozoite life cycle stages. The giardial microtubule cytoskeleton is comprised of highly dynamic and stable structures. Novel microtubule structures include the ventral disc that is essential for the parasite's attachment to the intestinal villi to avoid peristalsis. The completed Giardia genome combined with new molecular genetic tools and live imaging will aid in the characterization and analysis of cytoskeletal dynamics in Giardia. Fundamental areas of giardial cytoskeletal biology remain to be explored and knowledge of the molecular mechanisms of cytoskeletal functioning is needed to better understand Giardia's unique biology and pathogenesis.

Fine structure of a septate gregarine trophozoite in the black tiger shrimp Penaeus monodon

Gregarines are parasitic protozoa that occasionally parasitize the gut lumen of penaeid shrimp and other crustaceans. Here we describe the morphology of gregarine trophozoites found in the black tiger shrimp Penaeus monodon using light microscopy (LM) and scanning (SEM) and transmission (TEM) electron microscopy. Using LM with fresh preparations and with paraffin sectioning followed by hematoxylin-eosin staining, several trophozoites were discovered in the foregut and midgut, and gametocysts were found in the hindgut. Trophozoites existed both as solitary individuals and in association and exhibited either caudofrontal or lateral patterns. They were cylindrical in shape, 60 to 300 microm long by 10 to 60 microm wide, and consisted of 2 parts: a small anterior portion known as a protomerite, which was separated by a septum from a larger posterior portion known as a deutomerite. Under SEM, both the protomerite and deutomerite were found to be entirely covered with longitudinal, parallel pellicular folds 0.1 microm thick. Under TEM, the deutomerite was seen to contain a nucleus with a single eccentric nucleolus and several areas of peripherally located chromatin. The cytoplasm of both the protomerite and deutomerite contained abundant vesicles and granules of different sizes. The pellicle consisted of a double layer of electron-dense membranes separated by an electron-lucent area 30 nm wide and containing a microfilament. A few microfilaments were also observed in the cytoplasm underneath the pellicle, possibly serving as locomotive apparatus for the parasite. Based on its morphology, this gregarine appears similar to those of the genus Nematopsis.

Light and transmission electron microscopic studies on trophozoites and cyst-like stages of Histomonas meleagridis from cultures

The present study deals with Berlin strains of Histomonas meleagridis, the specimens of which were cultivated in Dwyer's medium. The light and electron microscopic examination revealed that the cultivated trophozoite stages (reaching about 10 mum in size) appeared more or less spherical, although their surface (covered by a single membrane) showed amoeba-like waves. All stages were uni-nucleated and reproduced by binary fission with an extranuclear spindle apparatus. Some trophozoites appeared ovoid and possessed a single flagellum with a typical microtubular 9 x 2 + 2 arrangement. Furthermore, the latter were characterized by an inner row of typical microtubules (remnant of an axostyle) and a Golgi apparatus (both adjacent to the nucleus), multivesicular structures, hydrogenosomes, and many food vacuoles containing either starch grains or bacteria. Their cytoplasm was densely filled with glycogen granules and ribosomes. Similar stages were also documented in the caeca and cloaca of chicken when being inoculated (via cloaca) with such culture stages. In addition to these typical trophozoites, the cultures contained a low number of 10-mum-sized spherical cyst-like stages with a surrounding amorphous layer. The cytoplasm of some of these cyst-like stages-when studied by electron microscopy-appeared with two membranes or had formed an amorphic, cyst-wall-like layer at their surface, apparently corresponding to their light microscopical appearance. Such stages might be involved in transmission from one host to another and probably have been missed before in microscopical examinations of infected poultry.

Entamoeba histolytica: Fibrilar aggregates in dividing trophozoites

Entamoeba histolytica trophozoite cytokinesis is dependent upon cytoskeletal elements such as filamentous actin and myosin. Here we present confocal and transmission electron microscopy studies of this process. A sequence in the formation of the contractile ring was shown with rhodamine-phalloidine staining. Ultrastructural analysis revealed the presence of fibrilar aggregates in the cytoplasm of dividing trophozoites. Among them two filaments of different diameter were identified. These aggregates presented repeating assemblies of thin and thick filaments that in cross section revealed a muscle-like appearance. Our results suggest that these aggregates constitute the contractile ring responsible for the separation of daughter cells.

An extraordinary endocytobiont in Acanthamoeba sp. isolated from a patient with keratitis

In the present article, the detection and the development of a parasitic endocytobiont within host amoebae (Acanthamoeba sp.) recently isolated from the contact lens and the inflamed eye of a patient with keratitis is presented. An otherwise healthy 55-year-old female patient presented with keratitis in her inflamed left eye. She was a contact lens wearer and had no history of a corneal trauma. Acanthamoebae as well as other smaller free-living amoebae could be detected from the fluid of the contact lens storage cases by culture methods. A successful therapy could be provided consequently. Two of these Acanthamoeba strains showed intracellular aggregating organisms. Within 2 to 3 days, the host amoebae ruptured, and numerous microorganisms were released. We succeeded in detecting the mechanism of infection and intrusion of this organisms by using light and electron microscopy. Infection with this endocytobiont is a suitable model for studying the host-parasite relations while the parasites use their hosts as so-called Trojan horses (see Barker, Lambert, Brown, Infect Immun 61:3503-3510, 1992).

alpha14-Giardin (annexin E1) is associated with tubulin in trophozoites of Giardia lamblia and forms local slubs in the flagella

In a previous study, we reported that the novel annexin XX1 (annexin E1), identical to alpha14-giardin, is specifically localized to the flagella and to the median body of the trophozoites. However, the mode of interaction and the direct partners involved remained unclear. In the present study, we show that alpha4-giardin obviously does not evenly distribute over the full length of the axonemes, but rather, resides at local slubs near the proximal part and the ends of the flagella. In immunocytochemical co-localization studies, the anti-giardin primary antibody exclusively reacted with distinct regions of the flagella in permeabilized cells, whereas the anti-tubulin antibody bound to all areas of the axonemes in the cells and to isolated cytoskeletons. Isolated cytoskeletons did not react with anti-giardin antibodies. alpha14-Giardin itself is able to assemble to multimeric structures. Taken together, our findings suggest that alpha14-giardin adheres to microtubules of the flagella via self-assembly that may regulated by Ser/Thr-phosphorylation.

Morphological aspects of Monocercomonas sp. and investigation on probable pseudocysts occurrence

Monocercomonas sp. is a flagellate protozoan found in the large intestine of snakes and in insects. Light microscopy revealed the measurements of morphological features of the trophozoites. Scanning electron microscopy showed in detail the emergence of the three anterior flagella, the recurrent flagellum, the axostyle, and the absence of undulating membrane. In addition, we described spherical forms which are probably pseudocysts. The investigation on the occurrence of this process was carried out through the incubation of Monocercomonas sp. trophozoites in several stressful conditions, such as pH change, nutrient depletion and different temperatures. Results revealed high pseudocyst formation at acidic pH values (4.0, 5.0, and 6.0), in absence of serum and in incubation at 37 degrees C. The occurrence of these pseudocystic forms in trichomonads life cycle is under investigation. This study describes the external structure of Monocercomonas sp., as demonstrated by light and scanning electron microscopy. Moreover, to our knowledge, this is the first time that formation of probable pseudocysts is shown in Monocercomonas sp., contributing to the research field on termite protozoa biology.

Mechanism of intrusion of a microspordian-like organism into the nucleus of host amoebae (Vannella sp.) isolated from a keratitis patient

Free-living amoebae (FLA) occur ubiquitously in many aquatic habitats and humid soils as well as in "artificial" water samples. In addition to their role as pathogens, FLA are known to serve as natural hosts and vehicles of transmission for various intracellular organisms. An otherwise healthy 24-year-old female patient presented with keratitis in her inflamed left eye. She was a contact lens wearer and had no history of corneal trauma. No acanthamoebae could be determined by culture methods. A Vannella strain (called VanAun0) isolated from corneal scrapings showed intracellular aggregating organisms. Within 1-2 days, the host amoebae ruptured, and numerous coccoid organisms (called Kaun1) were released. We succeeded in detecting the mechanisms of infection and intrusion of this eukaryotic organism, growing within the nucleus of the FLA, by light and electron microscopy. It could be shown that the spores at the cell membrane of strain KAun1 resemble Microsporidia and were taken up into the Amoeba by phagocytosis after adhesion of the spores and food cup formation (infective phase). The spores were transported into the cytoplasm of the vannellae in food vacuoles. Phase contrast microscopy revealed early stages of the parasites moving through the cytoplasm into the nucleus of the host amoeba. Electron microscopy showed the proliferation of polymorphic stages within the karyoplasm. The life cycle of these microsporidian-like organisms ended up with a sporogenic phase in which a terminal differentiation took place and numerous spores were released by rupture of the host cell wall. With the rupture of the host amoeba's cell membrane, the cycle started again from the beginning, the released infectious spores being ingested by other host amoebae. In particular, the morphology of the organelles made visible by electron microscopy finally allowed us to classify the endocytobionts as a microsporidan-like organism. Infection of Vannella sp. with the microsporidia-like organism strain KAun1 is a suitable model for studying the host-parasite relations of organisms using their hosts as so-called Trojan horses.

Didymium-like myxogastrids (class Mycetozoa) as endocommensals of sea urchins (Sphaerechinus granularis)

This paper sums up the results of light microscopical, ultrastructural and molecular studies of five strains of amoeboid organisms isolated as endocommensals from coelomic fluid of sea urchins, Sphaerechinus granularis (Lamarck), collected in the Adriatic Sea. The organisms are reported as Didymium-like myxogastrids. Of the life-cycle stages, the attached amoeboids, flagellated trophozoites, cysts and biflagellated swarmers are described. Formation of fruiting bodies was not observed. Although phylogenetic analyses of SSU rDNA sequences indicated a close relationship with Hyperamoeba dachnaya, our sea-urchin strains have not been assigned to the genus Hyperamoeba Alexeieff, 1923. The presence of either one or two flagella reported in phylogenetically closely related organisms and mutually distant phylogenetic positions of strains declared as representatives of the genus Hyperamoeba justify our approach. Data obtained in this study may be useful in future analyses of relationships of the genera Didymium, Hyperamoeba, Physarum and Pseudodidymium as well as in higher-order phylogeny of Myxogastrea.

Phylogeny of Neoparamoeba strains isolated from marine fish and invertebrates as inferred from SSU rDNA sequences

We characterised 9 strains selected from primary isolates referable to Paramoeba/Neoparamoeba spp. Based on ultrastructural study, 5 strains isolated from fish (amoebic gill disease [AGD]-affected Atlantic salmon and dead southern bluefin tuna), 1 strain from netting of a floating sea cage and 3 strains isolated from invertebrates (sea urchins and crab) were assigned to the genus Neoparamoeba Page, 1987. Phylogenetic analyses based on SSU rDNA sequences revealed affiliations of newly introduced and previously analysed Neoparamoeba strains. Three strains from the invertebrates and 2 out of 3 strains from gills of southern bluefin tunas were members of the N. branchiphila clade, while the remaining, fish-isolated strains, as well as the fish cage strain, clustered within the clade of N. pemaquidensis. These findings and previous reports point to the possibility that N. pemaquidensis and N. branchiphila can affect both fish and invertebrates. A new potential fish host, southern bluefin tuna, was included in the list of farmed fish endangered by N. branchiphila. The sequence of P. eilhardi (Culture Collection of Algae and Protozoa [CCAP] strain 1560/2) appeared in all analyses among sequences of strain representatives of Neoparamoeba species, in a position well supported by bootstrap value, Bremer index and Bayesian posterior probability. Our research shows that isolation of additional strains from invertebrates and further analyses of relations between molecular data and morphological characters of the genera Paramoeba and Neoparamoeba are required. This complexity needs to be considered when attempting to define molecular markers for identification of Paramoeba/Neoparamoeba species in tissues of fish and invertebrates.

Giardia lamblia: The effects of extracts and fractions from Mentha x piperita Lin. (Lamiaceae) on trophozoites

Giardia lamblia is a parasite that causes giardiasis in humans and other mammals. The common treatment includes different classes of drugs, which were described to produce unpleasant side effects. Mentha x piperita, popularly known as peppermint, is a plant that is frequently used in the popular medicine to treat gastrointestinal symptoms. We examined the effects of crude extracts and fractions from peppermint against G. lamblia (ATCC 30888) on the basis of trophozoite growth, morphology and adherence studies. The methanolic, dichloromethane and hexanic extracts presented IC(50) values of 0.8, 2.5 and 9.0microg/ml after 48h of incubation, respectively. The aqueous extract showed no effect against the trophozoites with an IC(50)>100microg/ml. The aqueous fraction presented a moderate activity with an IC(50) of 45.5microg/ml. The dichloromethane fraction showed the best antigiardial activity, with an IC(50) of 0.75microg/ml after 48h of incubation. The morphological and adhesion assays showed that this fraction caused several alterations on plasma membrane surface of the parasite and inhibited the adhesion of G. lamblia trophozoites. Cytotoxic assays showed that Mentha x piperita presented no toxic effects on the intestinal cell line IEC-6. Our results demonstrated antigiardial activity of Mentha x piperita, indicating its potential value as therapeutic agent against G. lamblia infections.

Fine structure and putative feeding mechanism of the archigregarine Selenidium orientale (Apicomplexa: Gregarinomorpha)

Archigregarines are considered one of the most plesiomorphic groups of Apicomplexa. Until recently, however, this viewpoint was based mainly on the results of the detailed investigation of a single species, Selenidium hollandei. The present study of the fine structure of trophozoites of another archigregarine species Selenidium orientale Bogolepova, 1953. (Apicomplexa, Archigregarinida, as proposed by Grassé and Schrével), with special reference to the forebody structure of the attached individuals, allows more confident discussion of the plesiomorphic status of the archigregarines. Specimens of S. orientale were collected from the midgut of the Pacific sipunculid Themiste pyroides Chamberlain, 1920. The ultrastructure of the trophozoites generally corresponds to that of other studied species of Selenidium. Differences in the forebody structure between S. orientale and S. hollandei do not conflict with Schrével's hypothesis on the feeding function of the apical complex in archigregarine trophozoites, although they suggest that, in S. orientale at least, the cytostome is not a persistent structure, but re-opens for each sucking event, and Selenidium trophozoites feed by intermittent sucking of host cytoplasm. Microtubules in the axial zone of the mucron neck may mediate the transport of food vacuoles.

[The injury of metronidazole on morphology of Giardia lamblia in vitro]

Trophozoites of Giardia lamblia were axenically cultivated with modified TYI-S-33 medium contained 500 microg/ml metronidazole (12h LC50). The morphology of drug-treated trophozoites was observed with light and electron micro-scopes at 2, 4, 8, 12 h respectively. The light microscopy revealed that the trophozoites treated with MTZ showed swollen, detached from the wall of the culture tube, and were with vacuoles in the cytoplasm. Movement of the flagella become slowly or stopped. Electronic microscopy showed that the trophozoites were swollen and deformed; lots of vacuoles were seen in the cytoplasm; the contents of cytoplasm were depleted and the nuclei deformed. This study indicated that MTZ has injured the morphology of G. lamblia.

Ultrastructural assessment of Plasmodium falciparum in age-fractionated thalassaemic erythrocytes

Culture of Plasmodium falciparum in age-fractionated thalassaemic red blood cells (RBC) has shown evidence of parasite damage on light microscopy in older cells during the third culture cycle (96-144 h). In this report, parasites growing in thalassaemic trait and normal RBC were examined ultrastructurally from 96 to 144 h. All parasite stages in old thalassaemic RBC showed evidence of damage worsening with culture duration. There were cytoplasmic alterations with ribosomal damage, and parasite cytoplasm became increasingly loose and grainy, with multiple fissures. Discontinuity of the nuclear membrane with an abnormal nucleolus was seen at l20 h. Cytosomes remained normal, but damage to the food vacuole and shrunken disintegrating parasites were observed at 144 h. These changes are compatible with cellular degeneration and developmental retardation and would account for the schizont maturation arrest and reduced reinvasion rates previously reported. Increased free radicals associated with thalassaemic erythrocytes would explain these changes, further supporting the role for oxidant stress in the protective mechanism.