An Entamoeba histolytica rab-like encoding gene and protein: function and cellular location

We identified here a 576 bp rab-like gene (EhrabB) in Entamoeba histolytica. EhrabB is located 332 bp upstream from the start codon of the Ehcp112 encoding gene, but is transcribed from the complementary strand. The EhrabB open reading frame predicts a 192 amino acid polypeptide (EhRabB) with 40-42% identity to Rab proteins, involved in vesicle docking regulation in endo and exocytic pathways of eukaryotic cells. Transcripts of 0.6 and 0.97 kb were detected by the EhrabB probe in northern blot assays. Using specific antibodies, EhRabB was located in small cytoplasmic vesicles by confocal microscopy. During phagocytosis, EhRabB was initially translocated to the plasma membrane and to the phagocytic mouths. The protein diminished after 10 min phagocytosis, suggesting that EhRabB could be participating in the regulation of the endocytosis process.

Entamoeba histolytica : a novel cysteine protease and an adhesin form the 112 kDa surface protein

Here, we present evidence that a cysteine protease (EhCP112) and a protein with an adherence domain (EhADH112) form the Entamoeba histolytica 112 kDa adhesin. Immunoelectron microscopy and immunofluorescence assays using monoclonal antibodies (mAbAdh) revealed that, during phagocytosis, the adhesin is translocated from the plasma membrane to phagocytic vacuoles. mAbAdh inhibited 54% adherence, 41% phagocytosis, and 35% and 62% destruction of MDCK cell monolayers by live trophozoites and their extracts respectively. We cloned a 3587 bp DNA fragment (Eh112 ) with two open reading frames (ORFs) separated by a 188 bp non-coding region. The ORF at the 5' end (Ehcp112 ) encodes a protein with a cysteine protease active site, a transmembranal segment and an RGD motif. The second ORF (Ehadh112 ) encodes a protein recognized by mAbAdh with three putative transmembranal segments and four glycosylation sites. Northern blot, primer extension and Southern blot experiments revealed that Ehcp112 and Ehadh112 are two adjacent genes in DNA. Ehcp112 and Ehadh112 genes were expressed in bacteria. The recombinant peptides presented protease activity and inhibited adherence and phagocytosis, respectively, and both were recognized by mAbAdh. The EhCP112 and EhADH112 peptides could be joined by covalent or strong electrostatic forces, which are not broken during phagocytosis.

Entamoeba histolytica: signaling through G proteins

The intracellular signaling pathways of Entamoeba histolytica are largely unknown. Although the expression of guanine nucleotide binding proteins (G proteins) is expected from functional studies, their biochemical characterization remains elusive in this protozoan. Using a combination of biochemical and immunological studies, we provide strong evidence for the presence of a Gs protein in amoeba. Our results strengthen our understanding of the signal transduction mechanisms in E. histolytica as potential sites of a new therapeutic strategy.

Family responses to HIV/AIDS in Mexico

This paper presents findings from a qualitative study of household and community responses to HIV/AIDS in Mexico. Fieldwork took place in two contrasting settings: (a) Ciudad Netzahualcóyotl, a socially marginalized urban community and (b) the homosexual community of Mexico City, a sexually marginalized social network. 113 in-depth interviews were conducted with people with HIV/AIDS, their relatives and members of their social networks. This paper describes findings from interviews conducted with family members of persons with AIDS. Four stages of response are identified and characterized within each community: (i) life before AIDS, (ii) life during the discovery of AIDS, (iii) living with a person with AIDS and (iv) surviving those who have died from AIDS. The social marginalization of both communities is central in explaining how families respond to the disease. In Ciudad Netzahualcoyotl, social support derives from a local culture of kinship. In the gay community, on the other hand, solidarity arises out of friendship. Between social support and discrimination, many more "ambivalent" behaviours (neither fully supportive nor discriminating) are displayed by family members and friends. Fear, pre-existing family conflicts and prejudice nurture these negative responses. Family responses and the processes to which they give rise, also differ depending on whether or not a male or female household member is affected. Policy recommendations are made concerning how best to promote positive family and household responses to persons with HIV/AIDS and how to inhibit negative ones.

AIDS-related illness trajectories in Mexico: findings from a qualitative study in two marginalized communities

This paper describes findings from a recent study examining how people affected directly and indirectly by the HIV/AIDS epidemic cope with HIV-related illness in Mexico. One-hundred-and-thirteen in-depth interviews were conducted with key informants in two contrasting communities: Ciudad Netzahualcóyotl (an economically marginalized community) and the gay community in Mexico City (a sexually marginalized community). This paper describes the AIDS-related wellness/illness careers or trajectories followed by individuals in both communities, and identifies critical points for material and emotional intervention. This career comprises four stages: (1) life before infection; (2) life surrounding the discovery of seropositivity; (3) living as an HIV-positive person; and (4) facing death. Comparisons are drawn between the processes of adjustment and coping found in both communities. In Ciudad Netzahualcóyotl, wellness/illness careers are closely linked to prevailing poverty and oppression, as well as the sense of urgency in which local people live their lives. In the case of the gay community, wellness/illness careers are associated with the intolerance and social repression faced by homosexual men. The paper concludes by suggesting possible interventions to improve the lives of people with HIV/AIDS in Mexico today.

Conceptual bases and methodology for the evaluation of women's and providers' perception of the quality of antenatal care in the WHO Antenatal Care Randomised Controlled Trial

In this paper, we describe the conceptual bases and methodology used to assess women's and providers' perception of the quality of antenatal care, as part of a large randomised trial in four developing countries. Information has been obtained by applying both qualitative and quantitative methodologies. The focus group discussions and in-depth interviews have contributed useful insights into the cultural milieu in which care is provided, users' and providers' expectations, and their concept of quality. Based on these findings, we developed two standardised questionnaires, one being administered to a representative sample of pregnant women (n = 1600) and the other for all care providers. In this paper we present some of the findings of the focus group discussions and in-depth interviews with women in one country as an example of the kind of information we have obtained. Women expressed their point of view concerning a reduced number of visits, type of provider, information that they get during clinical encounters and interpersonal relations with health professionals. The qualitative information, together with the data we obtain from the surveys, will highlight the aspects that will have be to considered if the new model of care is to be introduced on a routine basis.

The pyruvate:ferredoxin oxidoreductase enzyme is located in the plasma membrane and in a cytoplasmic structure in Entamoeba

This work investigated the cellular location of the pyruvate:ferredoxin oxidoreductase (PFO) enzyme in Entamoeba. A 1.9 kb fragment located at the 3' end of the Ehpfo gene was cloned in the pRSETB vector and expressed. The recombinant peptide was purified and inoculated in rabbits. By Western blot assays the antibodies detected a single 130 kDa band in all E. histolytica strains tested and in E. moshkovskii. By immunofluorescence, the antibodies showed the presence of PFO in the plasma membrane and in a cytoplasmic structure that appeared as a ring or as a compact small body in E. histolytica strains. In E. invadens and E. moshkovskii (strains FIC and Laredo) PFO was located in the plasma membrane showing different fluorescence patterns. Immunofluorescence on E. histolytica synchronized cultures showed that the cytoplasmic structure appeared in 85, 60, 20 and 10% of the trophozoites in mitosis, G1, S and G2 phases, respectively. By in situ hybridization the Ehpfo gene was found in the nuclei and the trophozoites of the clone A, strain HM1:IMSS, differed in the Ehpfo gene content.

Comparison of DNA migrations in two clamped homogeneous electric field chambers of different sizes. Relation between sample thickness and electrophoresis time

We present here a method to compare the mathematical descriptions of DNA migration per pulse as a function of pulse time. It is based on obtaining robust estimates and variances of DNA reorientation time, migration velocities during and after DNA reorientation; and on the statistical comparisons of these estimates. We demonstrated an equal description for the migration per pulse of each DNA molecule separated under identical conditions in clamped homogeneous electric field (CHEF) and miniCHEF chambers. However, miniCHEF resolved the patterns in shorter times, because it uses thinner samples. The relationship between sample thickness and CHEF run time is also presented.

Transcriptional analysis of the EhPgp5 promoter of Entamoeba histolytica multidrug-resistant mutant

We report here the cloning and transcriptional characterization of the EhPgp5 multidrug resistance gene promoter isolated from the drug-resistant clone C2 of Entamoeba histolytica. The EhPgp5 promoter has the TATA-like motif at -31 base pairs; transcription initiates three nucleotides upstream from the ATG in trophozoites grown in 225 microM emetine (clone C2(225)), whereas in those grown without the drug (clone C2) a product with no open reading frame was detected. The promoter was active in transfected clone C2 trophozoites, its activity increased when trophozoites were cultured in 40 microM emetine, while it was turned off in the drug-sensitive clone A. The first -235 base pair kept full promoter activity, suggesting that it has important drug responsive elements. Gel shift assays detected the complex Ib in clone C2, which was augmented in clone C2(225). Competition experiments suggested that complex Ib may be constituted by HOX and AP-1 like factors in clone C2, whereas in clone C2(225), complex Ib was only competed by the HOX sequence. Complexes Ie, detected in clones A and C2 but not in C2(225), and Ia, present in all clones, were competed by the TATA box oligonucleotide. Our results suggest that proteins forming complexes Ib and Ie may be participating in the regulation of the EhPgp5 gene expression.

Transcriptional analysis of the EhPgp1 promoter of Entamoeba histolytica multidrug-resistant mutant

We present here the cloning and characterization of the EhPgp1 multidrug resistance gene promoter isolated from the Entamoeba histolytica drug-resistant mutant clone C2. The EhPgp1 promoter lacks the typical TATA box and the transcriptional initiation sequences described for other E. histolytica promoters. The major transcription initiation site of the EhPgp1 gene was located at the ATG start codon. The EhPgp1 core promoter located within the first 244 base pairs showed a higher chloramphenicol acetyltransferase expression in the transfected trophozoites of clone C2 than in those of the sensitive clone A. Gel shift assays revealed three specific DNA-protein complexes (Ia, IIa, and IIIc) using nuclear extracts from clone C2, whereas three main complexes (If, IIf, and IIg) were limited to clone A. Competition assays suggested the presence of C/EBP-like and OCT-like proteins in complexes Ia and IIa, respectively, probably involved in the expression of the EhPgp1 gene, whereas complex IIIc was competed by GATA-1, C/EBP, OCT, and HOX oligonucleotides. Thus, differential DNA-protein complexes may be formed by transcriptional factors involved in the regulation of the EhPgp1 gene expression.