Entamoeba histolytica: gene linkage groups and relevant features of its karyotype.

We identified some gene linkage groups in Entamoeba histolytica using a 4-M urea improved transversal alternating field electrophoresis (TAFE) method. Complex rosette-structured DNA molecules were found trapped along the gel lanes, explaining the fuzziness of the patterns. Using several episomal probes, including 16 S, 5.

Cloning and expression of an Entamoeba histolytica NAPD+(-)dependent alcohol dehydrogenase gene.

In this paper we cloned, sequenced and expressed a novel Entamoeba histolytica alcohol dehydrogenase gene (Ehadh3). Ehadh3 has a predicted 383 amino acids open reading frame, encoding for a 42.3 kDa protein.

Gene amplification in Entamoeba histolytica.

We show here data suggesting that Entamoeba histolytica, the protozoan responsible for human amebiasis, presents DNA amplification in a fashion similar to that described for transformed mammalian cells. By transmission electron microscopy (TEM), we found linear, circular and concentric circular DNA molecules exhibiting the main events of the unscheduled DNA amplification process. Loops were formed after the recombination of two nonadjacent DNA regions, and bubbles appeared from the recombinant strands without involving the looped-out sequences.

Physiology and molecular biology of multidrug resistance in Entamoeba histolytica.

In this paper, we present the most relevant facts on multidrug resistance (MDR) in the protozoan parasite Entamoeba histolytica. MDR in E. histolytica presents characteristics similar to transformed mammalian cells.

Transcription termination at the Escherichia coli thra terminator by spinach chloroplast RNA polymerase in vitro is influenced by downstream DNA sequences.

We have investigated the mechanism of transcription termination in vitro by spinach chloroplast RNA polymerase using templates encoding variants of the transcription-termination structure (attenuator) of the regulatory region of the threonine (thr) operon of Escherichia coli. Fourteen sequence variants located within its d(G+C) stem-loop and d(A+T)-rich regions were studied. We found that the helix integrity in the stem-loop structure is necessary for termination but that its stability is not directly correlated with termination efficiency.

Increase in mRNA of multiple Eh pgp genes encoding P-glycoprotein homologues in emetine-resistant Entamoeba histolytica parasites.

With the goal of understanding possible mechanisms of drug resistance by the protozoan parasite Entamoeba histolytica (Eh), two novel Eh P-glycoprotein (Pgp) genes (Eh pgp5 and Eh pgp6) were sequenced, and the expression of four Eh pgp genes determined in wild-type (wt) clone A and emetine-resistant (EmR) clone C2 amebae. The Eh pgp5 gene encodes a 1301-amino acid (aa) protein that is similar to those of Eh pgp1 (64% aa identity), Eh pgp2 (61%), Eh pgp6 (39%) and Homo sapiens MDR (multidrug-resistance-encoding)(Hs MDR1; 38%) genes. The 1282-aa Eh pgp6 open reading frame (ORF), which is 19-28 aa shorter than those encoded by other Eh pgp, is also similar to those of Eh pgp1 (46% aa identity), Eh pgp2 (38%), and Hs MDR1 (39%).

Effect of etofibrate on bile production in the normolipidemic rat.

1. The effect of etofibrate, the ethandiol-1,2 diester of nicotinic and clofibric acids on bile production was studied in male rats that received a daily dose of 300 mg of etofibrate/kg body weight by stomach tube for 10 days and were compared with control rats receiving the medium. 2.

Cloning, genomic organization and transcription of the Entamoeba histolytica alpha-tubulin-encoding gene.

We have isolated and characterized an Entamoeba histolytica alpha-tubulin (alpha Tub)-encoding gene (Eh alpha tub). A 700-bp DNA fragment was amplified by PCR using primers derived from consensus alpha- and beta-Tub amino acid (aa) sequences from different organisms and E. histolytica DNA as the template.

Proteins of Entamoeba histolytica trophozoites involved in the adhesion to target cells.

To identify the molecules involved in the adhesion of Entamoeba histolytica trophozoites to target cells we used monoclonal antibodies (MAbs) and adhesion-deficient mutants. Human red blood cells (RBCs) were also used as specific carriers to identify the ameba molecules with affinity to the target cell receptors. MAbs Adh-1 and Adh-2 inhibited adhesion of RBCs to the trophozoites and recognized a 112-kDa surface protein that was present in the wild type strain, but was absent or modified in adhesion-deficient mutants.

A variable DNA region of Entamoeba histolytica is expressed in several transcripts which differ in genetically related clones.

A highly variable DNA region (EhVR1), isolated from Entamoeba histolytica clone A, strain HM1:IMSS, is transcribed into several transcripts, which differ in genetically related clones. EhVR1 (3.5 kb) is composed of two contiguous fragments; one of these 1.

Molecular karyotype of related clones of Entamoeba histolytica.

The molecular karyotype of 3 clones derived from strain HM1:IMSS of Entamoeba histolytica was studied by transverse alternating field electrophoresis. 11-20 bands ranging between 0.3 and over 3 Mb were resolved.

Expression of sequences related to c-myc in Entamoeba.

The evolutionarily conserved proto-oncogene c-myc is involved in both proliferation and differentiation processes of higher eukaryotic cells. We report here the identification and characterization of sequences homologous to c-myc in different Entamoeba species using a fragment of the mammalian c-myc gene as a probe. This probe hybridized with fragments of 3.

Entamoeba histolytica: changes in the zymodeme of cloned nonpathogenic trophozoites cultured under different conditions.

In this paper we report the occurrence of changes in the migration of certain isoenzymes of a cloned strain (MAV-CINVESTAV) of Entamoeba histolytica. This strain was isolated from an asymptomatic carrier and showed an initial nonpathogenic zymodeme I. The transfer of polyxenic trophozoites from Robinson's medium (7% serum) to Jones' medium (30% serum) provoked changes in isoenzyme expression, resulting in the conversion of zymodeme I to a zymodeme that was similar to the XVII zymodeme except for two slow-running bands and a single fast-running band that were detected for hexokinase (HK).

Primary sequences of two P-glycoprotein genes of Entamoeba histolytica.

Two P-glycoprotein genes (EhPgp1 and EhPgp2) from the protozoan parasite Entamoeba histolytica were sequenced from a genomic library made with the DNA of an emetine-resistant ameba mutant, which overexpresses mRNAs homologous to segments of the human mdr1 (P-glycoprotein) gene. The open reading frames for EhPgp1 and EhPgp2 were 1302 and 1310 amino acids long, respectively, and showed a 67% positional identity with each other and 41% and 40% positional identities, respectively, with human mdr1 gene. Within each ameba P-glycoprotein were the ATP-binding sites found twice in eukaryotic P-glycoproteins and once in prokaryotic transport proteins.

A rapid and sensitive method for HPLC cholesterol determination in bile.

A relatively little time consuming simple method based on the treatment of bile with cholesterol oxidase and subsequent high performance liquid chromatography measurement of the 3-ketocholesterol produced in order to determine the level of the cholesterol concentration is described. The method avoids bilirubin interferences, has high reproducibility and recovery assays give 100% values. It is highly sensitive and suitable for use in the determination of cholesterol concentrations in bile and other bilirubin containing biological fluids.

MURCS association and hypothalamic anovulation.

A new case of MURCS association (mullerian duct aplasia, renal aplasia and cervicothoracic somite dysplasia) in an 18 year old patient is reported. In addition to other minor phenotypical features, hypothalamic chronic anovulation was documented. Basal concentrations of PRL, TSH, GH, F and E were within reference values for adult women.

P-glycoprotein genes of Entamoeba histolytica.

Six different P-glycoprotein gene segments were identified from an emetine-resistant E. histolytica mutant, which overexpresses mRNAs homologous to segments of the human mdr1 (P-glycoprotein) gene. The open reading frames of two completely sequenced genes EhPgp1 and EhPgp2 were 1,302 and 1,310 amino acids long, respectively, and showed a 67% positional identity with each other and 41 and 40% positional identities, respectively, with human mdr1 gene.

Improved molecular karyotype of Entamoeba histolytica.

Different electrophoretic conditions were used to improve the molecular karyotype of Entamoeba histolytica clone L6 derived from the heterogeneous strain HM1:IMSS. Eleven to 17 bands ranging between 0.3 and over 3 megabases (Mb) were resolved by transverse alternating field electrophoresis (TAFE).

Use of polymerase chain reaction and nonradioactive DNA probes to diagnose Entamoeba histolytica in clinical samples.

E. histolytica parasites in Mexican children's stools were identified and typed as pathogenic or non-pathogenic using the polymerase chain reaction (PCR) and nonradioactive probes. PCRs were performed with primers specific for 145 base pair (bp) pathogenic or 133 bp non-pathogenic DNA sequences, which are highly repeated in E.

Purification and functional characterization of the 112 kDa adhesin of Entamoeba histolytica.

The 112 kDa adhesin of E. histolytica is directly involved in the cytopathogenic activity of the parasite. We describe here the purification of the 112 kDa protein by electroelution and immunoaffinity chromatography using a monoclonal antibody against the adhesin.

Neutral proteinase activities in different strains and clones of Entamoeba histolytica. Correlation with virulence.

Although several factors are involved in the invasive behavior of E. histolytica, proteinases seem to play a key role. Different proteinases have been found in virulent trophozoites of this parasite.