A Comparative Study of Different Leishmania Tropica Isolates from Iran: Correlation between Infectivity and Cytochemical Properties *

Ebrahimzadeh, A.; Jones, Thomas C.

doi:10.4269/ajtmh.1983.32.694

Cited by 29 publications

(9 citation statements)

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“…Membrane composition has been shown to in¯uence the ability of Leishmania to infect macrophages (Ebrahimzadeh and Jones 1983;Almeida et al 1993). Membrane composition has been shown to in¯uence the ability of Leishmania to infect macrophages (Ebrahimzadeh and Jones 1983;Almeida et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Cell surface carbohydrates and in vivo infectivity of glucantime-sensitive and resistant Leishmania (Viannia) guyanensis cell lines

et al. 2001

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The cell surface plays an important role in the interaction of parasites with their hosts. Drug resistance in the protozoan Leishmania may involve changes in cell-surface composition, although it is not known whether infectivity is also aected. One sensitive and two glucantime-resistant lines of Leishmania (Viannia) guyanensis previously isolated were inoculated into hamsters. The sensitive line caused the disease to manifest earlier than the resistant lines. Imprinting analyses of infected macrophages showed that the sensitive line was more infective than the resistant cell lines. In vitro drug resistance was evaluated and the comparative analyses of dose±response curves showed that the susceptibility pattern of the sensitive line did not change after passage in animals, but a decrease in drug resistance was observed in resistant cell lines recovered from the mammalian host. Cell surface carbohydrates of sensitive and resistant cell lines were analysed before and after passage in animals by agglutination tests with several plant lectins. Passage in animals changed the agglutination pattern for many lectins from all three cell lines. Loss of reactivity to lectins seemed to be correlated with a decrease in infectivity of the parasite-resistant cell lines. This study opens possibilities for exploring the relationship between drug susceptibility, infectivity and surface carbohydrate composition of protozoan parasites.

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Section: Discussionmentioning

confidence: 99%

Cell surface carbohydrates and in vivo infectivity of glucantime-sensitive and resistant Leishmania (Viannia) guyanensis cell lines

et al. 2001

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“…The wildtype LT252 line of L. major (10,20) and its methotrexate (MTX)-resistant derivative R1000-3 line bearing R region amplification (7) were studied. Promastigotes were propagated in M199 medium as previously described (14).…”

Section: Methodsmentioning

confidence: 99%

Transcriptional mapping of the amplified region encoding the dihydrofolate reductase-thymidylate synthase of Leishmania major reveals a high density of transcripts, including overlapping and antisense RNAs.

Kapler¹,

Beverley²

1989

Mol. Cell. Biol.

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We have examined the transcriptional organization of the R region of the protozoan parasite Leishmania major. This region encodes the bifunctional enzyme dihydrofolate reductase-thymidylate synthase (DHFR-TS) and is frequently amplified as a 30-kilobase (kb) extrachromosomal circular DNA in methotrexate-resistant lines. Northern (RNA) blot analysis shows that the R region encodes at least 10 stable cytoplasmic polysomal poly(A)+ RNAs, ranging in size from 1.7 to 13 kb and including the 3.2-kb DHFR-TS mRNA. Transcriptional mapping reveals that these RNAs are closely spaced and collectively cover more than 95% of the 30-kb amplified R region. The organization is complex, including several overlapping RNAs 3' of DHFR-TS and two examples of antisense RNAs 5' of DHFR-TS. The R region RNAs can be grouped into two empirical domains, with eight contiguous RNAs transcribed in the same direction as that of DHFR-TS and two contiguous RNAs transcribed in the orientation opposite to that of DHFR-TS. The two 5'-most RNAs of the DHFR-TS-containing domain overlap the RNAs transcribed from the opposite strand. These data are relevant to models of transcription, including recent studies suggesting polycistronic transcription in trypanosomatids. The abundance of R region RNAs increases uniformly 10-to 15-fold in the amplified R1000-3 line relative to the wild type, and no new RNAs were observed. This suggests that all elements required in cis for DHFR-TS expression are contained within the 30-kb circular DNA. Quantitative analysis reveals that the steady-state DHFR-TS mRNA and protein levels are not growth phase regulated, unlike the monofunctional mouse DHFR. DHFR-TS is developmentally regulated, however, declining about fivefold in lesion amastigotes relative to promastigotes.Trypanosomatid protozoan parasites comprise a group of eucaryotic organisms which use a number of unconventional strategies for gene expression. These include obligatory trans-splicing of a common nucleotide sequence, the miniexon, onto the 5' ends of all mRNAs (17, 57, 63, 70, 74; reviewed in 11), as well as editing of mitochondrial mRNAs (4,26). An increasing body of data suggests that some protein-coding mRNAs may be synthesized as larger polycistronic precursors, up to 60 kilobases (kb) in length, which are subsequently cleaved and processed into mature mRNAs. Evidence supporting this view includes the following: (i) determination of the size of a variant surface glycoprotein gene transcriptional unit by UV inactivation (38); (ii) demonstration of comparable transcription rates for flanking, mRNA-coding, and intergenic regions (30,46,72); and (iii) the identification of a putative polycistronic mRNA precursor (56). Whether this process is ubiquitous and what DNA sequences are involved in transcription initiation and mRNA processing remain to be determined because of the lack of striking sequence homology with consensus eucaryotic elements and the lack of in vitro or in vivo functional assays such as DNA transfection.We have examined the gene encoding ...

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“…However, they can be distinguished on the basis of their isoenzymes. There is further scope for distinction by lectin agglutination, although the interpretation of the results is not unambiguous (EBRAHIMZADEH and JONES, 1983). Typical differences also occur in the buoyant density of kinetoplast DNA, which allows one to differentiate, for example, among the South American species or subspecies (BARKER and BUTCHER, 1983).…”

Section: Morphology and Developmentmentioning

confidence: 99%

Medical Parasitology

Piekarski

1989

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A Comparative Study of Different Leishmania Tropica Isolates from Iran: Correlation between Infectivity and Cytochemical Properties *

Cited by 29 publications

References 0 publications

Cell surface carbohydrates and in vivo infectivity of glucantime-sensitive and resistant Leishmania (Viannia) guyanensis cell lines

Cell surface carbohydrates and in vivo infectivity of glucantime-sensitive and resistant Leishmania (Viannia) guyanensis cell lines

Transcriptional mapping of the amplified region encoding the dihydrofolate reductase-thymidylate synthase of Leishmania major reveals a high density of transcripts, including overlapping and antisense RNAs.

Medical Parasitology

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