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H Momen

Publications and source records attributed to H Momen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Disseminated American cutaneous leishmaniasis.

BACKGROUND: While studying cutaneous leishmaniasis in the central part of western Venezuela, we found four cases of disseminated American cutaneous leishmaniasis, three from the Lara State and one from Portuguesa State. METHODS: A clinical history was taken for each of these patients, followed by microscopic examination of the Giemsastained smears from their cutaneous lesions and by a Montenegro skin test. Serum from a skin lesion were grown in Novy-MacNeal-Nicolle medium (NNN). Hamsters were inoculated with suspension of tissues taken from the patient's lesions. Biopsies were taken for histopathologic examination. Isolates from cultures on NNN medium and from hamsters were subcultured in Schneider's medium for parasite identification, using molecular techniques. Treatment with injections of N-methyl glucamine antimonate, 25 mg/kg/day was prescribed for each patient for 20 consecutive days and, after a week of rest, a second course of injections was administered. RESULTS: Patients had disseminated papular, ulcerous, nodular, and ulceronodular lesions on the skin. Smears of the skin lesions from all of the patients showed abundant amastigotes within histiocytes or free in the tissues. The skin test was negative in two patients. On histopathologic examination of skin lesions, mainly numerous vacuolated histiocytes filled with amastigotes were observed. Isolates from all the patients were identified as Leishmania venezuelensis. One of the patients healed after treatment with N-methyl glucamine antimonate. The others were resistant to this therapy. CONCLUSIONS: Diffuse cutaneous leishmaniasis can be caused also by Leishmania venezuelensis. Patients with nodular lesions who presented a negative Montenegro skin test were more resistant to treatment with specific pentavalent antimonials.

Adolescent↗
PubMed1995

Genotypic polymorphisms in experimental metastatic dermal leishmaniasis.

Molecular karyotype and kDNA restriction analyses were utilized to examine the genetic heterogeneity and plasticity of the Leishmania (Viannia) guyanensis strain WHI/BR/78/M5313, composed of metastatic and non-metastatic populations. Cloning revealed that the strain was constituted by multiple closely related populations that were distinguishable by restriction fragment polymorphisms in kDNA. Size polymorphisms in molecular karyotype were not detected. Passage of clones in hamsters and recovery of parasites from cutaneous metastatic lesions yielded evidence of further genetic heterogeneity among some of the progeny populations. Overall, six kDNA minicircle restriction patterns or schizodemes were observed among clones, subclones and progeny. Although the possibility that population heterogeneity was not resolved by cloning cannot be ruled out, subcloning and kDNA restriction analysis to determine whether the putative clones consisted of homogeneous populations showed the schizodeme of subclones of 3 out of 4 clones to be identical to the clone of origin, while a subclone of the fourth had a co-efficient of similarity of 0.95. Metastasis did not segregate with a particular schizodeme: all six restriction profiles were represented among populations isolated from metastatic lesions and some clones with the same restriction profile did not produce metastatic lesions. The strain from which the clones, subclones and progeny were derived had a kDNA restriction pattern identical to the most prevalent schizodeme (38%) among these subpopulations. This finding together with the reappearance of the repertoire of schizodemes found among clones in the populations recovered from metastatic lesions in hamsters inoculated with a single clone, suggest that sequence polymorphisms in kDNA can emerge during infection.

Animals↗
PubMed1995

Intergenic region typing (IRT): a rapid molecular approach to the characterization and evolution of Leishmania.

In the New World, Leishmania of the Viannia subgenus cause both cutaneous and mucocutaneous disease. These parasites show considerable intra-species genetic diversity and variation, which complicates taxonomic classification and epidemiology. We have used the variability of the transcribed noncoding regions between the small and large subunit rRNA genes to examine relationships in this group. In a method termed intergenic region typing (IRT), PCR amplification products were obtained for the rapidly evolving 1-1.2-kb internal transcribed spacers (ITS) between the SSU and LSU rRNAs, from 50 parasites isolated from different hosts and geographic areas. Amplified DNAs were digested with 10 different enzymes, and fragment patterns compared after acrylamide gel electrophoresis. High levels of intra- and inter-specific variation were observed, and quantitative similarity comparisons were used to associate different lineages. A complex evolutionary tree was obtained. Some species formed tight clusters (L. equatorensis, L. panamensis, L. guyanensis, L. shawi), while L. braziliensis was highly polymorphic and L. naiffi showed intraspecific distances comparable to the largest obtained within all Viannia. L. colombiensis, L. equatorensis and L. lainsoni clearly represent distinct lineages. Good agreement was obtained with molecular trees based upon isoenzyme or mini-exon repeat sequence comparisons. Overall, IRT appears to be a superb method for epidemiological and taxonomic studies of Leishmania, being sensitive, rapid and quantitative while simultaneously revealing considerable molecular diversity. IRT could also be applied to other nonconserved intergenic regions, including those separating protein-coding genes.

Animals↗
PubMed1995

The distinction of pathogenic Vibrio cholerae groups using arbitrarily primed PCR fingerprints.

Pathogenic Vibrio cholerae strains were compared by fingerprinting with arbitrarily primed polymerase chain reaction (AP-PCR). They were O1 classical and El Tor strains and recent non-O1 Bengal strains. Ten oligonucleotides from a total of fifty-two tested gave distinctive patterns, and these strains were separated into four groups. A second technique, amplification of 16S/23S rRNA spacers with a pair of oligonucleotides, was also used. Various bands were obtained, and the result can be treated as an additional fingerprint with a different pattern for each of the groups. The method of AP-PCR fingerprinting is fast and sensitive. A test of the stability of the El Tor patterns was done with a set of strains isolated during the present Brazilian epidemics. Examples of AP-PCRs with non-O1 strains are given. A typing scheme is proposed in which oligo 1 is first used, and depending on the fingerprint obtained, additional oligonucleotides are used to confirm the classification of the strain. It is proposed that the AP-PCR technique be used for epidemiological studies, analysing strains reaching new locations or environmental isolates suspected of being pathogenic. It will be particularly helpful in cases in which traditional methods cannot clearly classify the strain.

DNA Fingerprinting↗
PubMed1995

Discrimination of Leishmania isolates using a limited set of enzymatic loci.

The characterization of more than 200 Leishmania isolates, using 18 enzymatic loci, indicated that only a limited number of enzymes produces diagnostic alleles which are potentially useful in the identification of species or zymodemes. 6-Phospho-gluconate dehydrogenase was the most polymorphic enzyme, containing enzyme, containing the majority of diagnostic alleles, and could be used to separate strains of the subgenus Leishmania from those of Viannia. It appears that just a few enzymatic loci, chosen a priori, are all that are needed in many taxonomic and epidemiological studies of Leishmania.

Alleles↗
PubMed1994

An analysis of the V1 and V2 regions of Vibrio cholerae and Vibrio mimicus 16S rRNA.

The V1 and V2 variable regions of the 16S rRNA gene of three strains of V. cholerae and one strain of V. mimicus were amplified by PCR. Fragments containing both regions were cloned into M13mp18 using Smal and sequenced by the dideoxy method. The 263-bp sequence from a strain isolated during the 1991 cholera outbreak in Brazil was deposited in Genbank under the accession number L05178. Except for an extra G in one of the strains, the three V. cholerae sequences were identical. The V. mimicus sequence was very similar, with only two substitutions. We compared these sequences with the Vibrio 16S rRNA sequences described by Dorsch et al. in 1992. It was noted that the V1 region, including helix 6 and its associated loop, comprised two different sizes and sequences in the various Vibrio species. While V. cholerae, V. mimicus, V. vulnificus, V. anguillarum and V. diazotrophicus had a 46-nucleotide V1, other species such as V. parahaemolyticus, V. proteolyticus, V. alginolyticus, V. campbellii and V. hollisae had longer 54- or 55-nucleotide regions, with a different consensus sequence. The phylogeny of Vibrio was analysed using the sequenced region and its equivalent in other species, by means of the "Phylip" software package. Species with a short helix 6 were grouped together, as were species with a long helix. Dorsh et al.'s analysis is discussed in relation to this "helix 6 split".

Cloning, Molecular↗
PubMed1994

Multilocus enzyme electrophoresis on agarose gel as an aid to the identification of entomopathogenic Bacillus sphaericus strains.

Sixty strains of Bacillus sphaericus, including 31 insect pathogens were studied by multilocus enzyme electrophoresis and were classified into 44 zymovars (electrophoretic types). Among the entomopathogenic strains, 11 belong to the same zymovar (Z59) indicating a widespread frequent genotype. Bands of enzyme activity were not detected among the strains for the loci GPI (E.C.5.3.1.9), G6P (E.C.1.1.1.49), 6PG (E.C.1.1.1.44) and ME (E.C.1.1.1.40). The enzymatic loci NP (E.C.2.4.2.1) and ACON (E.C.4.2.1.3) were monomorphic while the other enzymes, MDH (E.C.1.1.1.37), LeDH (E.C.1.4.1.9), ADH (E.C.1.4.1.1), EST (E.C.3.1.1.1), PEP-2 (E.C.3.4.11.1), PEP-3 (E.C.3.4.11) and PEP-D (E.C. 3.4.13.9) were polymorphic. The genetic variation in the non-insect pathogenic group seemed to be greater than in the entomopathogenic group. This latter group appears to be distinct from other strains of these species. All insect pathogens were recovered in the same phenetic cluster and a diagnostic allele is reported for the identification of entomopathogenic strains.

Animals↗
PubMed1994

A general classification of New World Leishmania using numerical zymotaxonomy.

More than 250 strains of Leishmania isolated from different localities and hosts in the New World were analyzed by enzyme electrophoresis, and their electromorphic profiles were compared with 19 reference strains representing most of the described species of this parasite. The 18 enzymic loci analyzed were very polymorphic, and the strains were classified into 44 zymodemes, each grouping strains with the same enzyme profiles. Each zymodeme was considered as an elementary taxon and the phenetic and phylogenetic relationships were determined by agglomerative hierarchical, ordination, and cladistic techniques. The different classification methods produced very similar results. The 44 zymodemes could be clustered into two groups, corresponding to the subgenera Leishmania and Viannia, by the numerical methods. The subgenus Viannia was shown to be monophyletic and could be further divided into species complexes representing L. braziliensis, L. naiffi, and L. guyanensis/L. panamensis/L. shawi, as well as some isolated taxa including L. lainsoni. The subgenus Leishmania, on the other hand, was polyphyletic, with New World isolates related to L. major clustered separately from the L. mexicana species complex. Most of the other zymodemes in this group represented independent taxa. The results confirm Viannia as a valid taxon but suggest that the status of the subgenus Leishmania should be further investigated. Leishmania braziliensis and L. naiffi were shown to be the most polymorphic species, while L. guyanensis, in spite of being the most common species found in this study, was remarkably homogeneous. The only variants were found south of the Amazon river. North of this river, the species was monomorphic.

Animals↗
PubMed1993

Trypanosoma rangeli: sequence analysis of beta-tubulin gene suggests closer relationship to Trypanosoma brucei than to Trypanosoma cruzi.

Trypanosoma rangeli, the only trypanosome besides Trypanosoma cruzi to infect humans in the Americas, shows an important geographical overlap with the agent of Chagas disease, and its taxonomic position has been the source of some controversy. This study utilizes beta-tubulin gene sequences for investigating the phylogeny of this species. All trees, produced with the different algorithms utilized, always grouped T. rangeli with Trypanosoma brucei in preference to T. cruzi. In addition evidence suggesting that the genus Trypanosoma may be polyphyletic was found.

Animals↗
PubMed1993

Molecular evidence for the importation of Old World Leishmania into the Americas.

A brief review of work carried out by the laboratory on the systematics of trypanosomatids during the last three years is given. The principal line of research has been on the taxonomy of New World Leishmania and one of the topics studied has been the determination of the autochthonous origin of certain Leishmania species found in the New World. Controversy exists as to whether the etiological agent of American Visceral Leishmaniasis is indigenous. Here, we present evidence from enzyme electrophoresis and schizodeme analysis indicating that L. chagasi has a recent origin and that it is similar to L. infantum. We also describe L. major-like isolates which have been found in the New World and present evidence suggesting that some of these populations may have been imported into the Americas. Reference strains from the subgenus Viannia are examined and compared with other Old World and New World species by enzyme electrophoresis. The results are analyzed numerically and we show that the Viannia species are a group of parasites indigenous to the New World that cluster separately from other Leishmania species. The numerical analyses also indicate that the subgenus forms a monophyletic group in contrast to the subgenus Leishmania which appears to be polyphyletic.

Americas↗
PubMed1993

[Cutaneous parasitism by Leishmania (Leishmania) chagasi during South American visceral leishmaniasis].

Eighteen patients from the northeastern Brazilian State of Ceara with proven kala-azar were studied for evidence of skin parasitism: two had ulcerative or papular skin lesions and 16 had clinically normal skin. Punch biopsies (3 mm) of intact paraspinal subscapular skin were performed on all patients; in those with papular or ulcerative lesions biopsies also were taken from an active site. One of each of the subscapsular biopsies and half of each biopsy from an active lesion were studied; the other specimens were seeded on NNN Difco Blood Agar Base Medium for parasite culture. The biopsies revealed a discrete to intense mononuclear inflammatory infiltrate, predominantly perivascular in nature. No amastigotes were observed in any tissue sections but 7 of the 18 patients yielded promastigotes on skin culture identified by monoclonal antibodies and by enzyme electrophoresis as Leishmania (Leishmania) chagasi [L. (L.) chagasi]. The isolation of Leishmania (Leishmania) chagasi, the recognized aetiologic agent of visceral leishmaniasis in the New World, from the skin of nearly 40% of 18 AVL patients proves dermatotropism of L. (L.) chagasi occurs and may be frequent in neotropical human visceral leishmaniasis (AVL.). Infected persons with skin parasites could act as a reservoir of infection and allow human to human transmission.

Adolescent↗
PubMed1992

Cuticular hydrocarbons, isoenzymes and behavior of three populations of Anopheles darlingi from Brazil.

Three populations of Anopheles darlingi were studied for cuticular hydrocarbons, isoenzymes and patterns of peak biting activity. Differences were found in specimens from Costa Marques, a malaria endemic area; Dourado, a site with a very exophilic population and Juturnaíba, located near the type locality. Twelve hour collections from sunset to sunrise showed that An. darlingi from Costa Marques had a bimodal biting activity profile with a major peak at sunset and a minor peak at sunrise. At Dourado, the pattern was trimodal, with peaks at both morning and evening periods of twilight and near midnight. The Juturnaíba population showed a slight increase in activity near 2000 and 0100 h. Nei's genetic distances, determined by isoenzyme electrophoresis between pairs of populations, were low (D < or = 0.049). Using discriminant analysis for the cuticular hydrocarbons, 92.4% of the specimens from Costa Marques, 91.2% of the specimens from Dourado and 61.3% from Juturnaíba were correctly identified. Cuticular hydrocarbon and isoenzyme results matched very well: the smaller the Nei's distance, the more misidentifications occurred in the jackknife estimator used in the cuticular hydrocarbon analysis. This is the first report of cuticular hydrocarbon analysis in combination with isoenzymes to investigate neotropical anopheline species.

Animals↗
PubMed1991

Leishmaniasis in Bahia, Brazil: evidence that Leishmania amazonensis produces a wide spectrum of clinical disease.

One hundred fourteen Leishmania isolates from patients with different clinical forms of leishmaniasis in the State of Bahia, Brazil, were characterized by indirect radioimmune binding assay using specific monoclonal antibodies (serodeme analysis). Seventy-five of these isolates were also analyzed by enzyme electrophoresis, based on 11 enzyme loci; parasite species were compared, according to their characteristic zymodemes, to those of WHO Leishmania reference strains. All isolates could be classified into one of three species: Leishmania amazonensis (n = 40), L. braziliensis (n = 39) or L. chagasi (n = 35). The most interesting information obtained from this study is the realization that L. amazonensis is capable of producing a wide spectrum of disease in humans. Infection with this parasite was associated with many different clinical presentations, including cutaneous leishmaniasis [CL] (20/49 cases), mucocutaneous leishmaniasis [MCL] (5/13 cases) and, of special note, visceral leishmaniasis [VL] (11/46 cases), as well as four cases of post kalaazar dermal leishmaniasis [PKDL]. In situ tissue parasite characterization, by immunoperoxidase assay and employing anti-L. amazonensis amastigote monoclonal antibodies, confirmed the infection with this species in two cases of CL, one case of DCL, one case of MCL and one case of PKDL. Our results also demonstrate the difficulty of parasite differentiation based on clinical grounds, since at least L. amazonensis infection can be associated with all types of leishmanial diseases, and different Leishmania species may be associated with indistinguishable clinical presentations. Since leishmanial parasites may vary in their biological behavior or in their response to treatment, it is important that their identification be made by reliable methods.

Animals↗
PubMed1991

Characterization and classification of leishmanial parasites from humans, wild mammals, and sand flies in the Amazon region of Brazil.

Ninety-four leishmanial isolates from the Brazilian Amazon Region (Amapá, Amazonas, Pará, and Rondônia) were identified and classified using specific monoclonal antibodies and an indirect radioimmunoassay (serodeme analysis); eighty-two were also characterized by enzyme electrophoresis (zymodeme analysis), the results of which were subjected to a numerical phenetic analysis. Six isolates from humans (3), Didelphis marsupialis (1), Lutzomyia olmeca nociva (1), and Lu, reducta (1) showed reactivity patterns and isoenzyme profiles similar to those obtained with the Leishmania amazonensis reference strains, and were identified as this species. Eighty-six stocks were classified as members of the L. braziliensis complex; of these, 61 were L. guyanensis or variants, which presented three serodeme subtypes, but whose isoenzyme profiles were all similar to the reference strain. A total of 15 isolates were distinguished as L. braziliensis or variants and were classified into five serodeme subtypes. The isolate from Psychodopugus davisi appeared, from the numerical analysis, to be a distinct parasite species. Ten isolates showed reactivity patterns and isoenzyme profiles similar to those obtained with the L. naiffi reference strain. A parasite isolated from Ps. claustrei appeared to be different from all reference strains by both techniques, and was classified as probably being a new species. The importance of these results with respect to the taxonomic status of the New World Leishmania, and their implications for both clinical and epidemiologic data are discussed.

Animals↗
PubMed1991

Lutzomyia ovallesi (Diptera: Psychodidae) as a vector of cutaneous leishmaniasis in Venezuela.

In the search for vectors of cutaneous leishmaniasis in the Barro Negro forest, Duaca, Lara State, Venezuela, 4,864 wild-caught Lutzomyia females were dissected and examined for promastigotes. Natural infection was found in 25 (0.5%) Lu. ovallesi. By biological parameters and enzyme electrophoresis all isolates from Lu. ovallesi were indistinguishable from those obtained from humans and dogs in the same Region. The isoenzyme profile of these isolates appear to indicate that strains were a hybrid between Leishmania braziliensis and L. guyanensis.

Animals↗
PubMed1990

Population heterogeneity among clones of New World Leishmania species.

Cell cloning techniques and schizodeme analysis were used to detect mixtures of subpopulations in Leishmania parasites, isolated from humans and a reservoir host. Clones were obtained by plating promastigotes, at limited dilution, on solid medium. The resultant colonies were analysed by the restriction profile of kinetoplast DNA minicircles (schizodeme analysis). The efficiency of plating was around 40-60%, and subpopulations of different schizodemes, in stocks of Leishmania isolated from 2 cases of human cutaneous leishmaniasis were detected. The presence of different schizodemes in one isolate from a sylvatic animal suggested the possibility of a mixed natural infection.

Animals↗