PubMed Health⌕ Search

Biomedical subjects

M Segovia

Publications and source records attributed to M Segovia.

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

Characterisation of the novel junctions of two minichromosomes of Leishmania major.

The minichromosomes M210 and M230 of Leishmania major are linear amplicons which have an inverted repeat structure. We report here the molecular cloning of the megabasic chromosome region where M210 and M230 recombination points are located. The analysis of this chromosomal region revealed a 374 bp fragment directly repeated 3 times, which was also repeated elsewhere in the genome. DNA fragments containing the novel junctions of the minichromosomes M210 and M230 have been likewise cloned. The nucleotide sequence of these fragments was determined and compared with their corresponding DNAs in the source chromosome. It revealed that M210 contains a central 226 bp non-repeated fragment, whereas the central fragment of M230 was 5 kb long. A 9 bp sequence which was repeated in inverted orientation around the recombination points of M230 was found. M210 showed instead an A + T rich DNA which could be implicated in its generation.

Animals↗
PubMed1996

[Use of alcoholism psychiatric services during an 18-month follow-up of alcoholic men].

BACKGROUND: The paper assesses the use of public psychiatric services by alcoholic patients for a period of 18 months, and looks for possible sociodemographic and clinical variables associated with higher use of services. MATERIAL AND METHODS: A prospective study of a cohort of male alcoholics (n = 137) from Alava (Spain). Information was gathered at the beginning of a treatment episode using a structured interview on sociodemographic and clinical variables, including Michigan Alcoholism Screening Test (MAST), and General Health Questionnaire (GHQ-60). At 18 month follow-up, clinical records were used to examine psychiatric inpatient and outpatient use in Alava (Spain). A service use score was set up to measure global use of services. RESULTS: Eighty-three percent of alcoholics used outpatient services at least once, 48% attended the day-care service at least once, and 24% were admitted in a psychiatric unit at least once, during 18 month follow-up. Twenty percent of patients used 80% of services. The logistic regression models point to the age, civil status, alcohol consumption amount and previous history of alcoholic treatments as the main predictors for heavy use of psychiatric services. CONCLUSIONS: A small percentage of alcoholics in treatment use the main part of psychiatric resources.

Adolescent↗
PubMed1996

Differentiation between Mycobacterium tuberculosis and Mycobacterium bovis by a multiplex-polymerase chain reaction.

A multiplex-polymerase chain reaction (PCR) assay, based on one-step amplification and detection of three different mycobacterial genomic fragments, was designed for differentiation between Mycobacterium bovis and Mycobacterium tuberculosis. The oligonucleotide primers were chosen from the groEL gene, present in the genus Mycobacterium sp., from the IS6110 insertion sequence, present in Myco. tuberculosis complex and from the mtp40 gene, identified as a specific-species Myco. tuberculosis genomic fragment. This amplification method allowed the detection of two fragments of 576 and 317 base pairs in Myco. bovis and three fragments of 576, 396 and 317 base pairs in Myco. tuberculosis strains, including atypical strains of Myco. tuberculosis where the copy number of the IS6110 element is low. The multiplex-PCR assay described may be a very useful tool for the rapid and specific differentiation of these related mycobacteria and easy to use in medical and veterinary microbiology laboratories.

Base Sequence↗
PubMed1996

Evaluation of mtp40 genomic fragment amplification for specific detection of Mycobacterium tuberculosis in clinical specimens.

A PCR assay based on the species-specific mtp40 genomic fragment was developed for the specific detection and identification of Mycobacterium tuberculosis in different uncultured clinical specimens. The aim of the study was to evaluate the clinical applicability of this target DNA in comparison with those of conventional microbiological methods and to compare the results obtained with those obtained after amplification with the IS6110 repetitive element. Discrepant results were interpreted in conjunction with the patients' clinical data, medical histories, and response to therapy. A total of 172 specimens from 162 patients with respiratory symptoms were tested, 101 specimens were obtained from 92 patients clinically suspected of having tuberculosis, and 71 specimens were obtained from 70 patients without known mycobacterial infection. The results of our study suggest that PCR amplification with the mtp40 genomic fragment provides a highly sensitive and specific technique for the detection of M. tuberculosis strains in clinical samples. It allows for the differentiation between M. tuberculosis and other related mycobacteria, including M. bovis, and is more specific than the IS6110 target. For these and other reasons, we propose that the mtp40 assay is a possible alternative for the specific direct detection of M. tuberculosis in clinical laboratories.

Bacterial Proteins↗
PubMed1995

Location in the source chromosome of the 180-kb minichromosome of Leishmania major and characterization of the novel junction.

The 180-kb LD1 minichromosome of Leishmania major (M180) is a large inverted duplication which arises spontaneously from a megabasic chromosome. In this work this locus has been located in the source chromosome at a telomeric position. Both the novel junction created in the middle of the minichromosome, as well as its counterpart region in the source chromosome were cloned and sequenced. Two inverted repeats, which could give rise to two imperfect stem-loops, and an A + T-rich DNA sequence were the only particular features observed in this region. A putative model for the formation of the minichromosome is proposed.

Animals↗
PubMed1995

Complement-mediated lysis and infectivity for mouse macrophages and sandflies of virulent and attenuated Leishmania major promastigotes varying in expression of the major surface protease and lipophosphoglycan.

The infectivity to mouse macrophages and sandflies, the expression and enzymatic activity of the major surface glycoprotein (gp63), the developmental modification of lipophosphoglycan (LPG) and three metacyclogenesis markers (promastigote body size, lectin agglutination and complement resistance) were compared in four related Leishmania major promastigote lines. The lines, which differed in their virulence for BALB/c mice, were examined in both logarithmic and stationary phase. Although the two non-virulent lines were unable to survive and multiply within the macrophages, they were better at attaching to the macrophages and infecting sandflies than the two virulent lines, which were highly infective for macrophages. Except for the higher resistance of the attenuated parasites to complement-mediated lysis, there were no clear differences between the metacyclogenesis markers of the four lines. The amount and enzymatic activity of surface gp63 was relatively high in the attenuated promastigotes and this appears to be related to a higher expression of gp63 genes. In terms of LPG, cells of all the lines had approximately twice the number of galactose and mannose residues per molecule when in logarithmic phase than when in stationary phase. LPG of the virulent lines also contained approximately twice the mannose and galactose residues of the attenuated line. Although L. major gp63 could therefore be important for promastigote survival in the sandfly and for the resistance to complement-mediated lysis, there was no apparent correlation between gp63 expression and promastigote survival in the macrophage. A very elongated LPG could be necessary for the survival and proliferation of the parasite in macrophages.

Animals↗
PubMed1995

Evidence from genotypic and phenotypic markers that an attenuated line outgrows a virulent one in a mixed population of Leishmania major promastigotes cultured in vitro.

Two cloned lines of Leishmania major promastigotes, one attenuated (CO1H) and one virulent (CO1R), differing in molecular karyotype and expression of the major surface glycoprotein (gp63), were mixed to produce two heterogeneous populations: MP-1 (100 CO1R promastigotes/CO1H promastigote); and MP-2 (10,000 CO1R promastigotes/CO1H promastigote). The mixed populations were cultured for 1 month in vitro in HO-MEM medium and sub-samples taken on days 4 and 30 were subjected to electrophoresis so that the molecular karyotypes and gp63-expression characteristics of the promastigote populations could be determined. In spite of the initial predominance of the virulent CO1R, the attenuated CO1H always outgrew it. The patterns of growth of pure cultures of CO1H or CO1R did not fully explain this observation. When grown alone, CO1H acidified the culture medium much more and much faster than CO1R, low pH values eventually inhibiting multiplication. Decreasing the medium's initial glucose concentration or increasing its initial pH prolonged the growth phase of CO1H, probably by slowing its acidification of the medium to inhibitory values. It is possible that, in mixed populations, the CO1R promastigotes help to buffer the medium, permitting faster and longer multiplication of the CO1H promastigotes than occurs when they are cultured alone. CO1H promastigotes may also inhibit CO1R multiplication; CO1H promastigotes in mid-logarithmic phase entered stationary phase within a day of being transferred into cell-free supernatants from 3-day-old CO1R cultures.

Animals↗
PubMed1995

The management information system and change processes in health systems.

This report describes a management information system (MIS) designed by PAHO's Health Systems and Services Division in collaboration with technical experts from a number of different countries. This MIS, a methodology currently used at the institutional or national level in more than 21 countries of the Americas, is a strategic and practical instrument that is easy to apply, interpret, and use, and whose purpose is to facilitate fundamental changes in health management. Based on the management concept that inputs, processes, and outputs are quantifiable, the MIS places special emphasis on health system productivity, an essential condition for achieving health coverage that is both adequate and equitable.

Community Mental Health Services↗
PubMed1994

Inverted repeat structure and homologous sequences in the LD1 amplicons of Leishmania spp.

In the parasitic trypanosomatids of the genus Leishmania, novel circular (CD) and linear (LD) multicopy genetic elements arise de novo either spontaneously or as a result of drug selection. We report that the LD1 minichromosomes of L. donovani, L. major and L. mexicana (ranging in size from 180 to 230 kb) have an inverted repeat structure and contain homologous sequences located at similar distances from the telomere; one half of the chromosome being the mirror image of the other. They must therefore have originated from a unique conserved source chromosome; the size polymorphism being generated by the point at which inversion occurs. The circular CD1 elements appear to be circularised segments of the LD1 elements. These observations lead to a unified concept of how minichromosomes LD1 and circular CD1 genetic elements emerge within the Leishmania and contribute to evolution of karyotype.

Animals↗
PubMed1994

Leishmania gene amplification: a mechanism of drug resistance.

Leishmania spp. are excellent models for analysing the mechanisms of drug resistance, one of the major barriers to the treatment and control of several major diseases. They may become refractory to drugs as the result of gene amplification. Amplified Leishmania DNA are extrachromosomal, usually circular, and arise from a source chromosome. Several multicopy extrachromosomal DNA have been identified, either spontaneously in unselected stocks or, more commonly, in response to multiple rounds of step-wise increases in drug concentration. R circles, G circles and ODC140-L minichromosomes are extrachromosomal amplifications encoding copies of dihydrofolate reductase-thymidylate synthase, glycosyltransferase, and ornithine decarboxylase, respectively, and conferring resistance to inhibitors of these gene products (methotrexate, tunicamycin and alpha-difluoromethylornithine, respectively). Another DNA amplification, named the H circle, has been detected in response to several unrelated drugs and confers drug resistance. Leishmania spp. represent a unique model since, even without drug pressure, gene amplifications appear and remain as extrachromosomal circular and linear amplicons. The CD1/LD1 elements, of unknown biological role, arise de novo in cultures in the absence of drug pressure.

Animals↗
PubMed1992

Dynamics and size polymorphisms of minichromosomes in Leishmania major LV-561 cloned lines.

Various lines and cloned lines of Leishmania major of varying degrees of virulence in BALB/c mice possessed size polymorphic multicopy minichromosomes related to previously described LD1/CD1 and 715-class DNAs of Leishmania. The minichromosomes were not necessary for virulence. Two of these DNAs (M180 and M210), coexisting in a single cloned line, showed remarkable dynamics in terms of loss or gain when followed through multiple transfers during in vitro culture and in vivo passage in BALB/c mice. Although there was significant sequence heterogeneity among minichromosomes, M180 sequences were present within large (megabase) and in intermediate (550-760 kb) chromosomes in the L. major lines analysed. M180 related small DNAs were also detected in Leishmania mexicana and Leishmania donovani isolates, suggesting that the generation of these molecules involves a common, probably functional basic mechanism widespread in Leishmania.

Animals↗
PubMed1992

Effects of long-term in vitro cultivation on the virulence of cloned lines of Leishmania major promastigotes.

The virulences of several clones from a single Leishmania major strain were studied in BALB/c mice. Clones showed the same pattern of infectivity and virulence two months after cloning as the parental population. After prolonged in vitro culture, however, it was apparent that two types of virulent clones existed: although the level of virulence remained stable in some clones, in others, such as C-11, it progressively decreased, as in the parental population. The progressive loss in virulence in a continuously cultured mixed population was probably due to selection, as the initial mixture of a stable virulent clone and a stable avirulent clone eventually yielded a totally avirulent promastigote population. After cultivation for 12 months, neither clone C-11 nor the parental population produced lesions in inoculated mice but virulent parasites were recovered from the inguinal nodes of the mice, possibly as a result of selection in vivo for virulent parasites.

Animals↗