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PubMed1984

[Acanthamoebae, Naegleria and other free-living Amoebae in cooling and rinsing water of dental treatment units].

215 water samples were taken from 49 dental treatment units and investigated for the existence of free-living amoebae. In all water-carrying systems of the dental treatment units it was possible to verify the incidence of one or more amoeba species. In 8.2 per cent of the units Naegleria species was found and in 12.2 per cent Acanthamoeba species was present. Seven Naegleria and six Acanthamoeba strains (2 A. castellanii and 4 A. polyphaga) were isolated. From samples originating from 12 dental treatment units (DTU) another 42 amoeba strains were isolated which consisted of 14 different species within 9 classes. Among them Vannella mira (in 19 per cent of samples) and Hartmannella vermiformis (10.6 per cent) were found to be the most frequent species, followed by H. cantabrigensis (9.5 per cent), V. platypodia, Platyamoeba stenopodia and V. simplex (7.1 per cent each). In 10 per cent of samples monotrichous and bitrichous flagellates such as the Bodo species were found, whereas two samples contained ova, larvae and adult free-living nematodes. Among the isolated Naegleria strains no thermophilic strain was present. Consequently they belong to the N. gruberi complex. Among the Acanthamoebae five of the six strains were thermophilic. All strains were investigated for pathogenic properties by means of the mice inoculation test. Two strains proved pathogenic - it was possible to isolate them from the brain and lung of dead mice. Another two strains proved to have invasive properties because they were isolated from the brain of infected animals; however, they did not give rise to disease or death of the respective animals. Supplementary microbiological tests demonstrated the existence of bacteria and fungi in 84 per cent of dental treatment units. Pseudomonas spec. were detected in 75% of dental units, Serratia marcescens in 2% and fungi in nearly 3%. 58.3% of all water samples contained total germ counts of more than 100/ml.

Amebiasis↗
PubMed1978

Ultrastructure of the frontal cap of monotactic forms of Amoeba proteus.

The frontal cap of the monotactic form of Amoeba proteus is separated from other cell components by a continuous structure defined as the "membrane-like envelope" (MLE). It originates from the membranes of cytoplasmic vesicles and vacuoles. The border zone between the cap and the cytoplasm is strongly vacuolized. Structural differences between frontal caps, depending on the degree of their development, indicate that the growing cap gradually fills up the whole tip of an advancing pseudopodium, and at the front it reduces the cortical layer in the interstice between the MLE and the outer cell membrane, up to its eventual disrupture. This is probably the efficient cause of the specific morphological and motory pattern of monotactic amoebae. These results and conclusions are supported by an ultrastructural analysis of the artificial frontal caps obtained by injecting oil droplets into polytactic cells, a procedure transforming polytactic forms into forms morphodynamically analogous to the natural monotactic amoebae.

Amoeba↗
PubMed1978

Response to light-shade difference in anucleate and polynucleate specimens of Amoeba proteus.

The enucleated specimens of Amoeba proteus, the anucleate fragments, and the polynucleate individuals which all are capable of cortical contraction but not of locomotion, may be reactivated by the light-shade difference established across their body. Individual cells or fragments migrate toward the shade. The motory polarity and coordinated movement disappear immediately after cessation of the stimulus. The results are interpreted according to the earlier hypothesis that the necessary to maintain the motory polarity of amoebae. It is suggested that the anucleate and polynucleate specimens are incapable of coordinated movements when non-stimulated, because of a deficiency or an excess, respectively, of the regulatory relaxing factor secreted by the nucleus of Amoeba proteus.

Amoeba↗
PubMedDate not supplied

[Little savage mammalians: free-living amoebae vectors? (author's transl)].

We tried to prove the part of the little savage mammalians as active intermediate hosts to the intestine level for some free-living limax amoebae of limax group. For this we participated to several trapping-season in Britanny and in Tunisia. From 273 samplings, we studied 224 with the results thereafter: the rodents are the first (213/224) and the 3 most frequent species are also the most often hosts: 20/128 A. sylvaticus, 9/58 C. glareolus and 4/16 M. spretus. There must be a double positive factor: life in burrow near the earth and meal type. The 78 samplings for which we checked the free-living amoebae by stool examination, are the most poor by culture: 2/78 (2.5 p. 100). This lack explains the negative stool examination. The isolated amoebae belong for 31/34 to the genus Acanthamoeba, of one potentially pathogenic: A. hatchetti. Moreover the Finistere biotop appears particularly poor (2.5 p. 100 carriers in front of 21 p. 100 in Ille-et-Vilaine and 24 p. 100 in Tunisia).

Amoeba↗
PubMed1982

Incidence of free-living amoebae in the nasal passages of local population in Zaria, Nigeria.

Following the observation of cases of primary amoebic meningoencephalitis (PAME) during the dusty harmattan period in Zaria, a survey was carried out in randomly selected local populations of Zaria, to find out the incidence of free-living amoebae in the nasal passages. The times of sampling were spaced so as to cover both the rainy (non-harmattan) abd dry (harmattan) seasons. In all 1250 individuals were sampled, and were grouped in the three age groups of above 18 years, between 4 and 18 years and below 4 years. The overall incidence was 4.2% (52 out of 1250). There was no marked difference in the three age groups studied. The incidence rate in males was 4.8% (30 of 630) and that in females was 3.5% (22 of 620). Nine different species of free-living amoebae were isolated. Six belonged to the Genus Hartmannella, two to the genus Naegleria, and one to the genus Schizopyrenus. Three species were found to be pathogenic for mice: H. culbertsoni, H. rhysodes and N. fowleri. It was observed from this study that a significant percentage of the Zaria population carry free-living amoebae in the nasal passages. The monthly incidence rate in population ranged from 1.8 to 3.1% during the rainy (non-harmattan) season whereas in the dry (harmattan) season it ranged from 4.2 to 7.9%. The highest incidence rate coincided with the peak of the dry (harmattan) season. The possible role of harmattan winds on the nasal carriage as well as the necessity to investigate fully the disease PAME in this environment is discussed.

Adolescent↗
PubMed1980

[Examinations on the occurrence of free-living amoebae with possible pathogenic traits in swimming pools (author's transl)].

Water of basins and filters taken from 9 indoor-pools and 5 heated outdoor-pools has been tested for free-living amoebae by means of filtration and subsequent cultivation on agar and in fluid media. In 94.6% of the samples taken from basins and in 60.7% of the samples taken from flushing back filter water, amoebae could be cultivated which all belonged to the genus of Acanthamoeba. They were tested for pathogenic symptoms by means of mouse inoculation tests, temperature tolerance tests, cross-reaction in the immunofluorescence test, and on tissue culture. 19 strains of amoebae could be re-isolated from lungs and brains of healthy mice. Only after the third series of inoculation from animal to animal, for mice characteristic pathogenic symptoms could be observed. The importance of acanthamoebae in swimming pools to the health of men cannot be estimated yet. But existing findings did not deliver reason for grave concern.

Amoeba↗
PubMed1980

[Studies of limax-amoebae in a physiotherapeutical indoor-swimming-pool (author's transl)].

A physiotherapeutical indoor swimmingpool in a hospital was inspected for the presence of potentially pathogenic Limax-amoebae. In cultures inoculated with material from water samples and from cotton swabs taken from the bottom and walls of the pool the following species of Limax-amoebae could be cloned and identified: Naegleria gruberi, Hartmannella vermiformis, Acanthamoeba castellamii, A. polyphaga, A. palestinesis, Vannella mira, V. platypodia, Platyamoeba stenopodia, Echinamoebia exundans and Vexillifera bacilipedes. Two further strains of unidentified Acanthamoeba and 1 of the genus Vanella were observed. 3 to 5 species remained unidentified. Beyond this numerous monotrichous flagellates and Colpoda steini, a holotrichous ciliate, multiplied in water samples and agar plates. The concentration of the total number of pelagic amoebae increased from 10 to 20/liter one week after exchange of the pool-water to 100-1000/liter after 3 weeks and finally to more than 10(4) per liter after a period of 2 months. The isolated strains of Nageleria, Acanthamoeba and Hartmannella were tested for pathogenicity by means of the intranasal mice inoculation test. The clones of Naegleria were submitted to a temperature- and salt-tolerance test. All of the strains tested by these methods proved to be nonpathogenic.

Amoeba↗
PubMed1994

[The resistance of Amoeba proteus amebae with different levels of nuclear DNA to the action of high temperature and ethyl alcohol].

Thermotolerance and resistance to ethyl alcohol were investigated in Amoeba proteus of polyploid series. Thermoresistance of these amoebae was determined by measuring the mean time of survival at the lethal temperature (43 degrees C). The resistance to ethyl alcohol was estimated by the mean percentage of individuals that survived following a 5-minute treatment with 7.5% ethyl alcohol. Neither thermotolerance, nor ethyl alcohol resistance were found to depend on the amount of nuclear DNA. It was also established that colchicine did not induce a hereditary instability of thermoresistance in amoebae.

Amoeba↗
PubMed1994

Isolation and identification of free-living amoebae from some water sources in Alexandria.

Samples from different water sources of Alexandria, and from nasal passages of 500 healthy children inhabiting areas nearby these sources were examined for the presence of free-living amoebae. These samples were cultured on 1.5% non nutrient agar streaked with bacteria. Amoebae were isolated and identified by means of their morphological characters and ability to produce flagellated forms. Characteristics of the cystic stages and pattern of excystation also aided in the identification of the various species. Nine species, Naegleria gruberi, N. fowleri, Acanthamoeba rhysodes, A. glebae, A. culbertsoni, A. astronyxis, A. palestinensis, V. avara and V. inornata were isolated from the water of canals and drains. N. gruberi and A. rhysodes were found in the nasal passages of six healthy children living near the contaminated canals. No amoebae were encountered in the drinking water, swimming pools, sea and lake water included in this study.

Acanthamoeba↗
PubMed1997

Unusual distribution of gamma-tubulin in the giant fresh water amoeba Reticulomyxa filosa.

We have isolated a cDNA encoding gamma-tubulin of Reticulomyxa. The deduced amino acid sequence revealed a high homology to known gamma-tubulin sequences from other organisms, underlining the hypothesis of conserved functions for gamma-tubulin in the cell. After introduction of restriction sites by site-directed mutagenesis and polymerase chain reaction (PCR), we cloned the cDNA into a bacterial expression vector. Recombinant gamma-tubulin was expressed in considerable amounts. Polyclonal antibodies raised against the recombinant material recognized in Western blots the bacterially expressed gamma-tubulin and in the amoeba crude extract a single band representing most likely the amoebal gamma-tubulin. In immunofluorescence studies the antibody showed a diffuse staining in the cytoplasm and no enrichment at centrosome-like structures. Because the assembly of centrosome-independent microtubules can be observed in the far extensions of the amoeba, the data suggest that in this amoeba gamma-tubulin might be involved in the centrosome-independent assembly of microtubules.

Amino Acid Sequence↗
PubMed1977

[Stable inheritable increase in the level of cell mortality (experiments on Amoeba proteus exposed to heat and radiation)].

Amoeba proteus cultivated as individual lines qt 24 degrees C were exposed to heating at 29 degrees C during three days or to X-rays of 200 kv at a dose of 5 kh or to combination of both. The original method -- periodical resumption of individual lines from sister-cells -- was used to observe the offspring of amoebae during 8 months. It is found that not only radiation but slight heating as well induce unusual hereditary effect in amoebae: stable increase of cell mortality level. The effect was the same at combination of both radiation and heating. It is likely that radiation as well as temperature act on one and the same cell responsible system.

Amoeba↗
PubMed1992

Behavior of Dictyostelium amoebae is regulated primarily by the temporal dynamic of the natural cAMP wave.

The instantaneous velocity plots of Dictyostelium discoideum amoebae responding to natural waves and simulated temporal waves of cAMP with periods of 7 min are highly similar. This similarity has been used to deduce the dynamics of a natural wave crossing an amoeba, and the behavior of amoebae has been characterized during the different phases of a natural wave with a computer-assisted dynamic image analyzing system. During the first approximately 150 sec of the front of a natural wave, cells move persistently toward the aggregation center, with high instantaneous velocity and a decreased frequency of lateral pseudopod formation. During the last 30 sec of the front of the wave and the first 30 sec of the back of the wave, there is a "freeze" in cell shape and a dramatic depression in cell motility, pseudopod formation, and intracellular particle movement. During the last 180 sec of the back of the wave, there is a rebound in pseudopod formation, but it is random in direction and leads to no net cellular translocation. The data suggest that all of the behavior of a cell but orientation during the translocation phase is mediated by the temporal dynamics of the wave. The data also suggest that orientation toward the aggregation center occurs early in the front of the wave and that, once oriented, cells move in a blind fashion during the translocation phase.

Animals↗
PubMed1988

Contact alters cAMP metabolism in aggregation-competent Dictyostelium amoebae.

cAMP and cell-cell contact are involved in the coordination of differentiation and morphogenesis in Dictyostelium discoideum. The experiments described in this paper establish a relationship between cAMP and cell-cell contact. Contact between Enterobacter aerogenes and aggregation-competent Dictyostelium amoebae and contact between Dictyostelium amoebae themselves results in the transient secretion of cAMP and an alteration in the amount of cAMP secreted in response to subsequent stimulation by cAMP, i.e., an alteration in magnitude of a cAMP relay response. The subsequent cAMP relay response can be enhanced or diminished depending upon the number of contacts formed and the concentration of cAMP present at the time of contact. Latex beads are capable of evoking cAMP secretion. However, the bead/amoebal contact is unable to alter the magnitude of a subsequent response to cAMP. This suggests that a nonspecific interaction via cell-cell contact elicits transient cAMP secretion in aggregation-competent Dictyostelium amoebae. The two responses to cell-cell contact are distinct from each other and distinct from the cAMP relay response. 1) The dose-response curves for the responses to Enterobacter contact are clearly different. 2) Contact with latex beads can elicit cAMP secretion but not alter the magnitude of a subsequent cAMP relay response. 3) The temperature dependences of the contact-induced responses and the cAMP relay response show that only the contact-induced cAMP secretion is inhibited at 12 and 15 degrees C, while only the cAMP relay response is inhibited at 28 degrees C. A 4-second application of cAMP at the time that contact is initiated enhances both contact-induced responses. Whether the relationship between these two developmental regulators is important for the regulation of Dictyostelium development has yet to be established.

Cell Communication↗
PubMed1990

Caffeine, an inhibitor of endocytosis in Dictyostelium discoideum amoebae.

The effect of the trimethylxanthine, caffeine, was examined on the growth and endocytosis pathways of the vegetative amoebae of the cellular slime mold Dictyostelium discoideum. Caffeine at concentrations of 1.5-3 mM was found to inhibit axenic growth, fluid-phase pinocytosis, and secretion of lysosomal enzymes. Cell viability was unaffected by incubation for 16 hours with 5 mM caffeine but decreased markedly thereafter. Phagocytosis of the bacterium Escherichia coli by Dictyostelium amoebae was also inhibited by caffeine, although at concentrations twofold to threefold higher. Caffeine rapidly entered into amoebae to reach an equilibrium between extracellular and intracellular concentrations, and it was not appreciably metabolized by Dictyostelium. Inhibition of growth and endocytosis was reversible upon removal of the drug and was partially counteracted by 10 mM adenosine. As caffeine discharged intracellular calcium stores in Dictyostelium (Abe et al., 1988), its inhibitory effect on endocytosis could result from the perturbation of calcium homeostasis. In agreement with this hypothesis, the cation La3+ (10 microM), a Ca2(+)-transport inhibitor, also strongly reduced fluid-phase pinocytosis.

Acid Phosphatase↗
PubMed1995

Bacteriolytic activities of the free-living soil amoebae, Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis.

Bacteriolytic activities of axenically grown free-living soil amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis towards various Gram-positive and Gram-negative bacteria were determined. A spectrophotometric assay revealed that the specific bacteriolytic activities of both Acanthamoeba species were higher as those of the three Hartmannella strains. Bacillus megaterium, Bacillus subtilis, Chromatium vinosum, Micrococcus luteus and Pseudomonas fluorescens were more easily lysed than the other bacteria tested. Agrobacterium tumefaciens, Klebsiella aerogenes and Serratia marcescens were hardly affected at all by the amoebal bacteriolytic activities. Among the Gram-negative bacteria we observed differences in lysis sensitivity while the Gram-positive bacteria tested were sensitive to lysis. Isoelectric focusing (IEF) gel-electrophoresis in the pH range 3-10 was performed to separate the bacteriolytic isoenzymes of amoebae. Bacteriolytic patterns were shown by using an activity assay in which lysis bands were formed in the agar/bacteria gel-overlay. The activity assay revealed remarkable differences in typical banding patterns for bacteriolytic activities among amoebae. Distinct differences between typical pI points of bacteriolytic activities in Acanthamoeba and Hartmannella were shown. Bacteriolytic activities of Hartmannella were more pronounced and observed in the isoelectric points (pI) range of 4.0-9.3 while for Acanthamoeba the range was pI 4.5-8.9.

Acanthamoeba↗
PubMed1985

Polypeptide compositions of amoebae of the cellular slime mould Dictyostelium discoideum separated by partitioning during development.

Amoebae of the cellular slime mould Dictyostelium discoideum at 8 h or 10 h development were separated into two populations by countercurrent distribution in a dextran-poly (ethylene glycol), two-phase system. Two-dimensional, polyacrylamide-gel electrophoresis was then used to separate the polypeptides from the populations of amoebae. The two populations of amoebae at 8 h development differed 9n polypeptide composition as did the populations separated at 10 h development. This confirms that cell differentiation is initiated in D. discoideum prior to 8 h development.

Countercurrent Distribution↗
PubMed2005

Acto-myosin cytoskeleton dependent viscosity and shear-thinning behavior of the amoeba cytoplasm.

The mechanical behavior of the human parasite Entamoeba histolytica plays a major role in the invasive process of host tissues and vessels. In this study, we set up an intracellular rheological technique derived from magnetic tweezers to measure the viscoelastic properties within living amoebae. The experimental setup combines two magnetic fields at 90 degrees from each other and is adapted to an inverted microscope, which allows monitoring of the rotation of pairs of magnetic phagosomes. We observe either the response of the phagosome pair to an instantaneous 45 degrees rotation of the magnetic field or the response to a permanent uniform rotation of the field at a given frequency. By the first method, we concluded that the phagosome pairs experience a soft viscoelastic medium, represented by the same mechanical model previously described for the cytoplasm of Dictyostelium discoideum [Feneberg et al. in Eur Biophys J 30(4):284-294 2001]. By the second method, the permanent rotation of a pair allowed us to apply a constant shear rate and to calculate the apparent viscosity of the cytoplasm. As found for entangled polymers, the viscosity decreases with the shear rate applied (shear-thinning behavior) and exhibits a power-law-type thinning, with a corresponding exponent of 0.65. Treatment of amoeba with drugs that affect the actin polymer content demonstrated that the shear-thinning behavior of the cytoplasm depends on the presence of an intact actin cytoskeleton. These data present a physiologic relevance for Entamoeba histolytica virulence. The shear-thinning behavior could facilitate cytoplasm streamings during cell movement and cell deformation, under important shear experienced by the amoeba during the invasion of human tissues. In this study, we also investigated the role of the actin-based motor myosin II and concluded that myosin II stiffens the F-actin gel in living parasites likely by its cross-linking activity.

Actins↗
PubMed2003

Cultivation and properties of Echinamoeba thermarum n. sp., an extremely thermophilic amoeba thriving in hot springs.

Here we describe a new, extremely thermophilic amoeba growing between 33 degrees C and 57 degrees C ( Topt.=50 degrees C). Isolates had been obtained from hot springs at Agnano Terme (Italy), Yellowstone National Park (USA), Kamchatka (Russia), and the Arenal Volcano (Costa Rica). They could be cultured monoxenically on a thermophilic alpha-proteobacterium. The morphology of the amoeba was studied using a microscope situated under a heatable polyacrylate hood. At 50 degrees C, the cells appeared flat with an irregular triangular or elongate shape, sometimes exhibiting fine spine-like subpseudopodia. On average, they were 22 microm long and 11 microm wide and had one nucleus with a central nucleolus. Based on morphology and on SSU rRNA comparisons, the amoeba belonged to the genus Echinamoeba, where it represents a new species. Referring to its extremely thermophilic lifestyle and its hydrothermal habitat, we name it E. thermarum.

Amoebida↗