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PubMed1992

The arginine-dependent cytolytic mechanism plays a role in destruction of Naegleria fowleri amoebae by activated macrophages.

Mouse peritoneal macrophages activated by different immunomodulators (Mycobacterium bovis bacillus Calmette-Guérin or Propionibacterium acnes) destroy Naegleria fowleri amoebae by a contact-dependent process and by soluble cytolytic molecules secreted by macrophages in response to lipopolysaccharide. The goal of this study was to determine whether the arginine-dependent cytolytic mechanism which results in the production of nitric oxide from arginine by activated macrophages destroys the amoebae. Amoebicidal activity of activated macrophages was determined by coculturing macrophages with N. fowleri amoebae radiolabeled with 3H-uridine. The percent specific release of radiolabel was used as an index of cytolysis of the amoebae. The inhibitors NG-monomethyl-L-arginine and arginase were used to determine whether the arginine pathway was a major effector mechanism responsible for amoebicidal activity of activated macrophages. Both the arginine analog NG-monomethyl-L-arginine and arginase, which breaks down arginine, decreased macrophage amoebicidal activity. Addition of arginine to arginine-free medium restores amoebicidal activity to activated macrophage cultures. These results demonstrate that the arginine pathway is an important mechanism for the destruction of susceptible N. fowleri amoebae.

Animals↗

PubMed1994

Microtubules are required in amoeba chemotaxis for preferential stabilization of appropriate pseudopods.

Amoebae of Physarum polycephalum exhibit chemotactic responses to glucose and to cAMP. The chemotaxing amoebae exhibit alternating locomotive movements: relatively linear locomotion and movements that change the direction of the locomotion. Such locomotive activity is tightly coupled with the changes in the number and the positions of the pseudopods; cells have one pseudopod at the leading edge during their linear locomotion, while they have multiple pseudopods when they are changing the direction of locomotion. Treatment of cells with microtubule-disrupting reagents inhibited the chemotaxis of the cells. To characterize the role of the microtubule system in chemotaxis, we quantitatively analyzed the relationship between the positions of multiple pseudopods of the amoebae and the relative stability of the pseudopods during reorientation. No significant differences were observed in the pseudopod dynamics between the untreated and the treated amoebae. In both cases, one pseudopod at the leading edge continued to expand during linear locomotion. It then split into two to three pseudopods in the reorientation phase, and the positions of the multiple pseudopods were random. Among multiple pseudopods, however, the pseudopods closer to the microneedle tip were selectively stabilized more often than those distant from the tip in the presence of the microtubule system. By contrast, such preferential stabilization of the appropriate pseudopods was completely abolished by microtubule inhibitors. The microtubule-dependent selection of appropriately located pseudopods enables amoebae to turn correctly at the reorientation step.

Animals↗

PubMed2003

[Isolation of potencially pathogenic free-living amoebas in hospital dust].

OBJECTIVE: To evaluate the occurrence of free-living amoebas of the genera Acanthamoeba and Naegleria is dust samples colleted in two hospitals. METHODS: One-hundred and thirty-two dust samples were collected in two hospitals in Brazil. Hospital collection sites were the following: intensive care unit, operation rooms, nursery, kitchen, emergency and infectious diseases isolation room. The isolation of the amoebas was performed in three culture media: non-nutrient agar inoculated with Escherichia coli, soy agar, and microculture in Giazzi-modified Pavlova's medium. The amoebas were identified according to morphological criteria. RESULTS: Amoebas of the genera Acanthamoeba and Naegleria were found in 45.5% of the samples, of which 41.6% were collected in the university hospital and 50% in the state hospital. Of all, 45.5% were positive for the genera Acanthamoeba and 3.8% for genera Naegleria. CONCLUSIONS: Potentially pathogenic free-living amoebas were seen in all sites of the two hospitals and Acanthamoeba was the most frequently isolated genera.

Acanthamoeba↗

PubMed2000

Horizontal Distribution Patterns of Testate Amoebae (Protozoa) in a Sphagnum magellanicum Carpet.

The distribution of soil microorganisms is generally believed to be patchy and to reflect habitat heterogeneity. Despite this general rule, the amount of existing data on species distribution patterns is scarce. Testate amoebae (Protozoa; Rhizopoda) are an important component of soil microbial communities and are increasingly used in ecological and paleoecological studies of Sphagnum-dominated peatlands, but data on the spatial structure of communities are completely lacking. This is an important aspect since quantitative models used for paleoecological reconstruction and monitoring are based on species assemblages. We explored the distribution patterns of testate amoebae distribution in a macroscopically homogeneous Sphagnum carpet, down to a scale of several centimeters. Distributions maps of the species and spatially constrained sample groups were produced. Multivariate and individual spatial autocorrelations were calculated. The importance of spatial structure was quantified by canonical correspondence analysis. Our ultimate goal is to find the finest resolution of environmental monitoring using testate amoebae. The distribution patterns differed among species, resulting in a complex spatial structure of the species assemblage in a whole. Spatial structure accounted for 36% of the total variation of species abundance in a canonical correspondence analysis constrained by spatial variables. This structure was partly correlated to altitude (microtopography) at a very fine scale. These results confirmed the existence of significant broad- and fine-scale spatial structures within testate amoebae communities that could in part be interpreted as effects of ecological gradients. This shows that, on a surface area of 0.25 m(2), ecological conditions which look uniform from a macroscopic point of view are not perceived as such by Sphagnum-inhabiting organisms. Therefore, testate amoebae could prove very useful to monitor fine-scale ecological processes or disturbances. Studies of the species' spatial distribution patterns in combination with autoecological studies are needed and should be included in the toolbox of biomonitoring itself.

Journal Article↗

PubMed2004

Advances in the knowledge of amphizoic amoebae infecting fish.

Free-living amoebae infecting freshwater and marine fish include those described thus far as agents of fish diseases, associated with other disease conditions and isolated from organs of asymptomatic fish. This survey is based on information from the literature as well as on our own data on strains isolated from freshwater and marine fish. Evidence is provided for diverse fish-infecting amphizoic amoebae. Recent progress in the understanding of the biology of Neoparamoeba spp., agents responsible for significant direct losses in Atlantic salmon and turbot industry, is presented. Specific requirements of diagnostic procedures detecting amoebic infections in fish and taxonomic criteria available for generic and species determination of amphizoic amoebae are analysed. The limits of morphological and non-morphological approaches in species determination are exemplified by Neoparamoeba, Vannella and Platyamoeba spp., which are the most common amoebae isolated from fish gills, Acanthamoeba and Naegleria spp. isolated from various organs of freshwater fish, and by other unique fish isolates of the genera Nuclearia, Thecamoeba and Filamoeba. Advances in molecular characterisation of SSU rRNA genes and phylogenetic analyses based on their sequences are summarised. Attention is particularly given to specific diagnostic tools for fish-infecting amphizoic amoebae and ways for their further development.

Animals↗

PubMed2005

Early detection and identification of amphizoic amoebae from nasal exudates of a symptomatic case.

A man visited the Out Patient Department of the hospital for Tropical Diseases in February 2004 with low grade fever and severe headache for a week. He had the history of diving in a natural pond 2-3 days before the onset of the disease. A thick bloody mucous was observed from the nasal discharge. Fresh microscopic observation of the exudates in 0.85% sodium chloride revealed numerous active amoeba trophozoites. Two groups of the trophozoites were observed The first group was 10 micro sized amoeba with active directional movement by lobopodia and the second group was 15-30 micro sized amoeba with active multiprogressive movement by filopodia. Few flagellate forms were observed after exflagellation in distilled water and some polygonal cysts were also found. Giemsa' stain was used to differentiate the amoeba trophozoites from the leukocytes. It was concluded that this patient was infected by both Naegleria spp. and Acanthamoeba spp. This is the first report of double infection of free-living amoeba in a symptomatic and non-fatal patient.

Acanthamoeba↗

PubMed1964

ELECTRON MICROSCOPY OF MITOSIS IN A RADIOSENSITIVE GIANT AMOEBA.

Various aspects of the ultrastructure of the dividing nuclei in the large radiosensitive amoeba Pelomyxa illinoisensis are demonstrated. Evidence of nuclear envelope breakdown is presented, and membrane fragments are traced throughout metaphase to envelope reconstruction in anaphase and telophase. Annuli in the nuclear envelope and its fragments are shown throughout mitosis. During metaphase and anaphase some 15 to 20 mitochondria are aligned at each end of the spindle, and are called polar mitochondria. The radioresistant amoebae Pelomyxa carolinensis and Amoeba proteus do not have polar mitochondria, and Pelomyxa illinoisensis is unique in this regard. The shape of the P. illinoisensis interphase nucleoli differs from that in the two radioresistant species, and certain aspects of nucleolar dissolution in the prophase vary. Helical coils in the interphase nucleoplasm are similar to those in the radioresistant amoebae. A "blister" phase in the flatly shaped telophase nuclei of P. illinoisensis is described which is interpreted to be the result of a rapid nuclear expansion leading to the formation of the normal spherical interphase nuclei.

Amoeba↗

PubMed2001

Minipodia and rosette contacts are adhesive organelles present in free-living amoebae.

Using scanning electron microscopy, Amoeba proteus cells migrating on the glass have been shown to develop dense coats of minipodia, which are discrete microprotrusions up to 8 microm long and approximately 0.5 microm across. They cover the middle-anterior area of the ventral cell surface, i.e. the region previously determined as the zone of most efficient adhesion of an amoeba to its substratum. Minipodia are sparse underneath the frontal zone and lacking from the tail region. In amoebae that adhere to the glass without moving, have just started moving, or show unstable motor polarity, minipodia are grouped in rosette contacts, cauliflower-like papillae composed of supporting platforms with crowns of minipodia emerging from them. Both structures abound with cytoskeletal F-actin, as shown by staining with fluorescein-conjugated phalloidin. Amoebae experimentally prevented from adhering to the substratum neither develop discrete minipodia nor rosette contacts.

Amoeba↗

PubMed1993

Pathogenic and free-living amoebae isolated from swimming pools and physiotherapy tubs in Mexico.

A protozoological survey was done to isolate free-living amoebae from swimming pools and physiotherapy tubs in Mexico City. Amoebae were isolated by culture in nonnutritive agar medium combined with Escherichia coli. Identification of the isolates was done by morphology using specialized taxonomic keys and by isoelectric focusing of total proteins and isoenzymes in agarose. Pathogenicity of the isolates was determined in 3-week-old mice by intracerebral and intranasal inoculations. Statistical tools were used to determine the existence of significant differences on the incidence and diversity of the isolates in relation to the two types of water bodies analyzed. Water and environmental temperatures, pH, and chloride concentrations were determined at each sampling site. Twenty-nine amoebic strains from eight genera were isolated. Most frequently found were specimens of the genera (Acanthamoeba (with four pathogenic strains), Vahlkampfia, Hartmannella, and Naegleria. Amoebae were isolated more frequently in spring and summer, and could not be recovered from pools with chloride levels of 5.31 mg/ml or more. This survey demonstrates that chloride concentrations commonly used in recreative pools and therapy tubs are not sufficient to eliminate viable cysts of most free-living amoebae. Significantly higher numbers of isolates were retrieved from the pools than from the tubs.

Amebiasis↗

PubMed1996

Cytotoxicity of polyamines to Amoeba proteus: role of polyamine oxidase.

It has been shown that oxidation of polyamines by polyamine oxidases can produce toxic compounds (H2O2, aldehydes, ammonia) and that the polyamine oxidase-polyamine system is implicated, in vitro, in the death of several parasites. Using Amoeba proteus as an in vitro model, we studied the cytotoxicity to these cells of spermine, spermidine, their acetyl derivatives, and their hypothetical precursors. Spermine and N1-acetylspermine were more toxic than emetine, an amoebicidal reference drug. Spermine presented a short-term toxicity, but a 48-h contact time was necessary for the high toxicity of spermidine. The uptake by Amoeba cells of the different polyamines tested was demonstrated. On the other hand, a high polyamine oxidase activity was identified in Amoeba proteus crude extract. Spermine (theoretical 100%) and N1-acetylspermine (64%) were the best substrates at pH 9.5, while spermidine, its acetyl derivatives, and putrescine were very poorly oxidized by this enzyme (3-20%). Spermine oxidase activity was inhibited by phenylhydrazine (nil) and isoniazid (approximately 50%). Mepacrine did not inhibit the enzyme activity at pH 8. Neither monoamine nor diamine oxidase activity (approximately 10%) was found. It must be emphasized that spermine, the best enzyme substrate, is the most toxic polyamine. This finding suggests that knowledge of polyamine oxidase specificity can be used to modulate the cytotoxicity of polyamine derivatives. Amoeba proteus was revealed as a simple model for investigation of the connection between cytotoxicity and enzyme activity.

Amebicides↗

PubMed1989

Prostaglandins may play a signal-coupling role during phagocytosis in Amoeba proteus.

Phagocytosis in Amoeba proteus can be induced with prostaglandins (PG). In addition, arachidonic acid (the fatty acid precursor to the PG-2 series) also induces phagocytosis. The induction of phagocytosis with arachidonic acid can be partially inhibited by the cyclooxygenase inhibitor indomethacin. Phagocytosis in the amoeba can also be induced with the chemotactic peptide N-formylmethionyl-leucylphenylalanine (NFMLP). The peptide presumably induces phagocytosis by interacting with receptors on the amoeba surface, which may initiate the release of arachidonic acid from membrane lipids. NFMLP-induced phagocytosis can also be partially inhibited by indomethacin. It is suggested that PG's or biochemically related substances may play a signal-coupling role during phagocytosis in the amoeba.

Amoeba↗

PubMed1980

Capacity of enucleated amoebae to recognize and respond to heterologous cytoplasm.

When amoebae are injected with heterologous cytoplasm from another type of amoeba, cellular organelles are segregated and degenerate within membrane-bounded spaces in the host's cytoplasm. In the present study, the role of the nucleus in this response was tested by injecting heterologous cytoplasm from Pelomyxa carolinensis into enucleate and enucleate Amoeba discoides. Samples were prepared for ultrastructural study at intervals between 15 min and 2d after the operation. In enucleate recipients of heterologous cytoplasm, organelles and cellular debris were observed in vacuole-like spaces indistinguishable in morphology and frequency from those of nucleated recipients. When donor cytoplasm included thoria particles, the electron-dense tracer was found along with degenerating organelles in the vacuole-like structures, confirming the presence there of injected cytoplasm. changes of comparable magnitude were not observed when either nucleated or enucleated cells were injected with homologous cytoplasm. The results indicate that nuclear activity is not necessary for the ultrastructurally observable responses of amoebae to heterologous cytoplasm. It is suggested therefore that the cytoplasm possesses a mechanism for recognition of at least some types of heterologous organelles.

Amoeba↗

PubMed1976

Microfilaments in Naegleria fowleri amoebae.

Examination by electron microscopy has revealed 2 types of microfilament in the cytoplasm of 3 strains of axenically grown Naegleria fowleri amoebae. Thin, actin-like microfilaments 5-7 nm in diameter are randomly oriented in the nonmotile amoebae, and are concentrated near the plasma membrane. In the actively motile amoebae these microfilaments aggregate to form colateral bundles in close proximity to the plasma membrane. Thick, myosin-like microfilaments 17-19 nm in diameter also occur in the amoebae cytoplasm. The significance of these 2 kinds of microfilament in amoeboid motion is discussed.

Actins↗

PubMed2005

The ecology of testate amoebae (Protists) in sphagnum in North-western Poland in relation to peatland ecology.

We studied the relationship between testate amoebae (Protozoa) communities and the depth to the water table (DWT), pH, conductivity, and microhabitat type in Sphagnum dominated peatlands of north-western Poland and built predictive (transfer function) models for inferring DWT and pH based on the testate amoebae community structure. Such models can be used for peatland monitoring and paleoecology. A total of 52 testate amoebae taxa were recorded. In a redundancy analysis, DWT and pH explained 20.1% of the variation in the species data and allowed us to identify three groups of taxa: species that are associated with (1) high DWT and low pH, (2) low DWT and low pH, and (3) high pH and mid-range DWT. Our transfer function models allow DWT and pH to be estimated with mean errors of 9.89 cm and 0.71 pH units. The prediction error of the DWT model and the tolerance of the species both increase with increasing dryness. This pattern mirrors the ecology of Sphagnum mosses: Species growing in wet habitats are more sensitive to change in water table depth than the species growing in drier microhabitats. Our results are consistent with studies of testate amoeba ecology in other regions, and they provide additional support for the use of these organisms in paleoecological and biomonitoring contexts.

Adaptation, Physiological↗

PubMed1989

A spectrin-like protein present on membranes of Amoeba proteus as studied with monoclonal antibodies.

Monoclonal antibodies against a spectrin-like membrane-associated protein of xD amoebae. (Amoeba proteus) were used to determine the distribution of the protein and some of its characteristics. A total of 34 monoclonal antibodies recognizing different epitopes of the protein were obtained, of which seven stained cell membranes by indirect immunofluorescence. The spectrin-like protein had two subtypes of 225 and 220 kDa and several monoclonal antibodies cross-reacted with human erythrocyte spectrin when checked by indirect immunofluorescence staining and immunoblotting. Some of the antibodies also cross-reacted with antigens in HeLa cells and chick embryo fibroblasts. Polyclonal and monoclonal antibodies against Drosophila and human erythrocyte spectrins cross-reacted with the spectrin-like protein from amoebae. On the basis of these results, it was concluded that the protein is a spectrin. The protein was found on most cellular membranes of amoebae, including the plasma, nuclear, and phagosomal membranes, as well as symbiosome membranes.

Amoeba↗

PubMed1985

Peptides as modifiers of Na+-induced pinocytosis in starved Amoeba proteus.

Low concentrations of six peptide hormones; glucagon, vasoactive intestinal peptide, substance P, angiotensin II, lysine-vasopressin, arginine-vasopressin, and the chemotactic peptide fMet-Leu-Phe, activated the capacity for pinocytosis in starved Amoeba proteus. Competitive inhibitors of the chemotactic peptide in leucocytes inhibited activation by fMet-Leu-Phe, suggesting that its action in the amoeba is mediated by specific receptors. The opioid peptides, beta-endorphin, dynorphin (1-13) and leu-enkephalin abolished through a naloxone-sensitive mechanism activation by hormones and several other activating agents. Also, low concentrations of beef and pork insulin inhibited activation by peptide hormones. An insulin analogue of low potency in mammalian cells was inactive in the amoeba. These results support the hypothesis that besides opioid receptors, there may be insulin receptors and possibly receptors for several other peptide hormones in Amoeba proteus.

Amoeba↗

PubMed2006

Influence of amoebae and physical and chemical characteristics of water on presence and proliferation of Legionella species in hospital water systems.

The reservoir for hospital-acquired Legionnaires' disease has been shown to be the potable water distribution system. The objectives of the present study were as follows: (1) to examine the possible relationship between physical-chemical characteristics of water such as temperature, pH, hardness, conductivity, and residual chlorine and the presence of amoebae as growth-promoting factors for Legionella species and (2) to determine eradication measures for water distribution systems to seek ways of reducing the risk of legionellosis. Ten hospitals in southwest France took part in this study. Water samples were collected from 106 hot water faucets, showers, hot water tanks, and cooling towers. Two analyses were performed to analyze the association between water characteristics and (1) the presence of Legionella species and (2) the proliferation of Legionella species. Of the 106 water samples examined, 67 (63.2%) were positive for Legionella species. Amoebae were detected in 73 of 106 (68.9%) samples and in 56 of 67 (86.6%) Legionella species-positive samples (P < 10(-6)). In these positive samples, conductivity was lower than 500 microOmega(-1).cm(-1) in 58.2% (P = .026), temperature was below 50 degrees C in 80.6% (P = .004), and hardness was significantly higher (P = 002) than in Legionella species-negative samples. Neither Legionella species nor amoebae were isolated from any sampling point in which the water temperature was above 58.8 degrees C. Multivariate analysis shows that high hardness and presence of amoebae were strongly correlated statistically with the presence of Legionella when showers, tanks, pH, and temperature promoted their proliferation. This study shows the importance of water quality evaluation in assessing environmental risk factors and in selecting the most appropriate prevention and control measures in hospital water systems.

Amoeba↗

PubMed2004

Amoebae and other protozoa in material samples from moisture-damaged buildings.

Mold growth in buildings has been shown to be associated with adverse health effects. The fungal and bacterial growth on moistened building materials has been studied, but little attention has been paid to the other organisms spawning in the damaged materials. We examined moist building materials for protozoa, concentrating on amoebae. Material samples (n = 124) from moisture-damaged buildings were analyzed for amoebae, fungi, and bacteria. Amoebae were detected in 22% of the samples, and they were found to favor cooccurrence with bacteria and the fungi Acremonium spp., Aspergillus versicolor, Chaetomium spp., and Trichoderma spp. In addition, 11 seriously damaged samples were screened for other protozoa. Ciliates and flagellates were found in almost every sample analyzed. Amoebae are known to host pathogenic bacteria, such as chlamydiae, legionellae, and mycobacteria and they may have a role in the complex of exposure that contributes to the health effects associated with moisture damage in buildings.

Amoeba↗