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  • 1
    Electronic Resource
    Electronic Resource
    Incorporation and Toxicity of 32P-Orthophosphate and Occurrence of Poly phosphate in Entamoeba Trophozoites (1985)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 32 (1985), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We explored the requirements of inorganic phosphate (Pi), the incorporation of 32P-orthophosphate (32Pi), and the occurrence of inorganic polyphosphate (polyP) in axenic Entamoeba cultures. Maximal population densities and growth rates of Entamoeba histolytica trophozoites were attained in complete TP-S-1 medium. As 32Pi concentration was increased in the medium, its own incorporation and the culture growth rate were progressively inhibited, especially in Pi-deficient medium. PolyP grains were found in the cytoplasm and occasionally in the nuclear membrane of E. histolytica, E. histolytica-like, E. invadens, and E. moshkovskii trophozoites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1985.tb03065.x
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  • 2
    Electronic Resource
    Electronic Resource
    Isolation and characterization of mammalian cell lines carrying suppressible mutations (1988)
    Springer
    Molecular genetics and genomics 213 (1988), S. 105-111 
    Details
    ISSN: 1617-4623
    Keywords: Nonsense suppressors ; Hypoxanthine-guanine phosphoribosyltransferase ; Thymidine kinase ; Double revertants ; Lesch-Nyhan syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To obtain animal cell lines carrying nonsense mutations and the corresponding suppressors, we used a “supersuppressor” selection strategy on the CHO cell line. The wild-type strain is resistant to the aminopterin present in HAT medium (i.e., it is HATr) because it contains the enzymes hypoxanthine-guanine phosphoribosyl transferase (HPRT) and thymidine kinase (TK), whereas both HPRT mutants — selected by their resistance to 6-thioguanine (TGr) — and TK- mutants — selected by their resistance to 5-bromodeoxyuridine (BrdUrdr) — are HATs. Therefore, from HPRT- TK- double nonsense mutants, whose phenotype would be TGr BrdUrdr (HATs), simultaneous HPRT+ TK+ double phenotypic revertants could be obtained by selecting HATr (TGs BrdUrds) variants carrying the corresponding nonsense supersuppressors. Through ethylmethane sulfonate (EMS) mutagenesis of the CHO cell line we obtained 65 TGr variants, 53 of which were HATs and the rest HATr. Among 36 TGr (HATs) variants tested, 23 did not revert to HATr, 4 reverted spontaneously and with EMS, and 9 reverted only with EMS. Some of the latter were probably HPRT- nonsense mutants because they were very stringent (had less than 2% of wild-type [3H]hypoxanthine incorporation and HPRT enzyme activity), and did not complement genetically. The introduction of a second marker (BrdUrdr) in 7 of these strains allowed us to isolate 29 TGr BrdUrdr (HATs) double drug-resistant lines. Through one-step mutagenesis and selection in HAT medium, from two double resistant strains we could isolate HATr (TGs BrdUrds) wild-type phenotypic revertants, each of which probably carries suppressible HPRT and TK nonsense (or missense) alleles and the corresponding supersuppressor. Our strategy could now be extended to obtain variants carrying suppressors in other cell lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333405
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  • 3
    Electronic Resource
    Electronic Resource
    Immediate deterioration of rabbit colon preparations byEntamoeba histolytica trophozoite lysates (1992)
    Springer
    Parasitology research 78 (1992), S. 260-262 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931737
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristic protein electrophoretic patterns of fourEntamoeba strains (1978)
    Springer
    Parasitology research 56 (1978), S. 219-225 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Total proteins from trophozoites of four axenized strains of the histolytica group ofEntamoeba (twoE. histolytica, oneE. invadens, and oneE. moshkovskii) were analyzed by disc-electrophoresis in polyacrylamide sodium dodecyl sulphate slab gels and by radial immunodiffusion. Each strain had a characteristic and reproducible electrophoretic pattern with about 30 major protein bands distributed between molecular weights 12,000 and 110,000. A striking similarity was found between the protein patterns of bothE. histolytica strains. Immunodiffusion also resulted in characteristic patterns, in which the greatest resemblance occurred in the same strains. The sensitivity and high resolution of the electrophoretic method for protein analysis and its correlation with antigenic characterization suggests its use as a taxonomic criterion of the histolytica group of the genusEntamoeba.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931715
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  • 5
    Electronic Resource
    Electronic Resource
    Dose- and time-dependent functional and structural damage to the colon mucosa byEntamoeba histolytica trophozoite lysates (1993)
    Springer
    Parasitology research 79 (1993), S. 517-522 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Analysis of the initial interaction betweenEntamoeba histolytica trophozoites and the large intestine is impossible in humans and very difficult in experimental animals. To circumvent this obstacle we treated the luminal side of full-thickness rabbit colon segments mounted in Ussing-type chambers with trophozoite lysates of theE. histolytica HM1 virulent strain. Exposure to lysates for up to 90 min produced dose- and time-dependent effects on the colon, consisting of (a) increased decay rates for potential difference, short-circuit current, and transmural resistance and (b) mucosal damage ranging from vacuolation at the bases and shortening of epithelial cells to the loss of intercellular junctions, destruction of microvilli, and necrosis of interglandular epithelial zones. This acute model of intestinal amebiasis is sensitive, fast, and reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931595
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  • 6
    Electronic Resource
    Electronic Resource
    Stimulation of DNA synthesis on animal cell microcultures by a heat-stable cytoplasmic factor ofEntamoeba histolytica (1986)
    Springer
    Parasitology research 72 (1986), S. 133-136 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00927744
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  • 7
    Electronic Resource
    Electronic Resource
    Cytopathogenicity ofEntamoeba histolytica: Trophozoite homogenates modulate DNA synthesis in a mammalian cell line (1981)
    Springer
    Parasitology research 65 (1981), S. 11-17 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We examined the effect of total trophozoite homogenates from four axenized strains ofEntamoeba histolytica (HK9, HM1, HM2, and HM3) on the DNA synthesis of subconfluent cultures of Chinese hamster ovary (CHO) cells incubated at low (0.1%) serum concentration. HM1, HM2, and HM3 extracts increased [3H]thymidine incorporation to acidinsoluble material in CHO cells up to a maximum of 2.5, 1.5, and 1.5 times respectively, at doses of amebal protein ranging from 16 to 125 μg/ml. HM1 and HM2 extracts at doses higher than those causing maximal stimulation, and HM3 and HK9 extracts above 250 μg protein per ml, progressively inhibited [3H]thymidine incorporation by CHO cells at a strain-specific rate. The extracts with both the most potent stimulatory and inhibitory effects were those from HM1 and HM2, also the most virulent strains. This strain-specific ability of amebal products to modulate cell DNA synthesis may play a significant role in amebal virulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00926549
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  • 8
    Electronic Resource
    Electronic Resource
    Proteinases resistant to sodium dodecyl sulfate-induced autoproteolysis ofEntamoeba histolytica HK9 trophozoites (1993)
    Springer
    Parasitology research 79 (1993), S. 168-171 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932265
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  • 9
    Electronic Resource
    Electronic Resource
    In vivo and in vitro experimental intestinal amebiasis in Mongolian gerbils (Meriones unguiculatus ) (1997)
    Springer
    Parasitology research 83 (1997), S. 170-176 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract   One of the main drawbacks of experimental amebiasis is the lack of an adequate animal model for invasive intestinal lesions. Mongolian gerbils are useful because both intestinal and hepatic amebiasis can be produced experimentally with Entamoeba histolytica trophozoites. In this paper we show results obtained with in vivo and in vitro models of intestinal amebiasis in gerbils. We inoculated gerbils intracecally with monoxenic cultures of a highly virulent E. histolytica HM1:IMSS substrain. In the in vivo model an increase in mucus production was observed during the first 6 h of interaction. Microulcerative mucosal lesions appeared at 24–72 h postinoculation. Inflammatory infiltrate and edema of the lamina propria were associated with superficial foci of necrosis. At 96 h the cecal mucosa had an almost normal appearance and live amebas were no longer detected. In the in vitro model, early damage was detected in cecal strips mounted in Ussing chambers as a rapid fall in potential difference, short-circuit current, and transepithelial resistance that correlated with the extent of the microscopic lesions produced. The latter consisted of cellular edema and the appearance of small, translucent vacuoles at the base of epithelial cells. Further damage led to loss of intercellular junctions, destruction of interglandular epithelial cells, and edema of the lamina propria. The present results demonstrate that the gerbil is useful as an experimental model for the analysis of early stages of invasive intestinal amebiasis both in vivo and in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004360050228
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  • 10
    Electronic Resource
    Electronic Resource
    Subcellular distribution and stability of the major hemolytic activity ofEntamoeba histolytica trophozoites (1982)
    Springer
    Parasitology research 67 (1982), S. 249-254 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Since the hemolytic activity of extracts fromEntamoeba histolytica trophozoites previously described by us might determine at least partially the necrotic lesions of amebiasis, we have continued its characterization in vitro. Using rat erythrocytes as target cells, we have found that cytolysis byE. histolytica trophozoite extracts was (1) dose dependent, (2) localized mainly in a vesicular fraction whose absolute and specific activities were respectively 1.9 and 4.0 times higher than those of total extracts, (3) maximal at pH 8 in the presence of 1 mM Ca++, and (4) progressively lost by heating at 90°C or repeated freezing and thawing. From these results we infer that the major hemolytic factor ofE. histolytica may be a protein normally neutralized by an intracellular inhibitor or activated during fractionation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00927659
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