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G Langsley

Publications and source records attributed to G Langsley.

At least 55 records · Page 3Linked to original sources
PubMed1991

A Plasmodium falciparum blood stage antigen highly homologous to the glycophorin binding protein GBP.

We have isolated a gene coding for a protein highly homologous to an antigen known as the glycophorin binding protein (GBP) which was therefore called GBPH. The gene consists of 2 exons interrupted by an intron located at a position corresponding to that of the GBP gene. The deduced amino acid sequence of GBPH comprises 427 residues and is characterized by a signal sequence and by an extended repeat region consisting of 8 units of 40 amino acid residues. The comparison of the amino acid sequences of GBPH and GBP reveals an identity of 69%. Antisera raised against a GBPH fragment that carries part of the repetitive region cross-react with GBP (105 kDa) and additionally detect some bands between 40 and 70 kDa, one of which may correspond to GBPH. The genes coding for GBP and GBPH are located on chromosomes 10 and 14, respectively. The GBP gene is transcribed as a highly abundant 6.5 kb mRNA in the blood-stage form, whereas Northern blot analysis using a GBPH specific probe detects 2 less abundant mRNAs of 2.3 kb and 2.7 kb. Southern blot analysis of P. falciparum DNA identifies a third member of the GBP gene family.

Amino Acid Sequence↗
PubMed1991

Polymorphism of the alleles of the merozoite surface antigens MSA1 and MSA2 in Plasmodium falciparum wild isolates from Colombia.

The degree of polymorphism and the allelic distribution of 2 major Plasmodium falciparum merozoite surface antigens (MSA1 and MSA2) have been analysed in clinical isolates from Colombia. DNA was prepared directly from patients' blood and used in PCR reactions to amplify block 2 of MSA1 and the central region from MSA2. Thirty one samples were analysed and a marked degree of length polymorphism was detected, especially for MSA2. A high proportion of multiple bands was also observed, most probably resulting from mixed infections. Allele-specific oligonucleotides were used to type both alleles. For MSA1, 26 out of 31 clinical isolates were of the RO33 type, 15 were MAD20 and three were typed as KI. When the MSA2 allele was analysed, 7 isolates hybridised with a CAMP specific probe and 6 hybridised strongly with an FC27-derived oligonucleotide. Two samples, which showed multiple bands, hybridised with both probes. Interestingly, in 14 out of 27 isolates the MSA2 allele remained unassigned by the specific probes. Five of these were cloned and their DNA sequenced; these sequences are discussed.

Adolescent↗
PubMed1988

Chromosome size polymorphism in Plasmodium falciparum can involve deletions of the subtelomeric pPFrep20 sequence.

The P. falciparum pPFrep20 repetitive element from the Palo Alto Uganda strain has been isolated and sequenced. The Palo Alto pPFrep20 repeat (pPFPArep20) has a clustered subtelomeric location and on chromosome 1 has been deleted from one end. Analysis of chromosome 1 from 5 other strains has revealed that pPFrep20 sequences have been deleted from one end in 3 of them. Thus, deletion of pPFrep20 appears to be a frequent event that could significantly contribute to chromosome size polymorphism in P. falciparum.

Animals↗
PubMed1988

The S-antigen of Plasmodium falciparum Palo Alto represents a new S-antigen serotype.

The S-antigen from the Palo Alto isolate of Plasmodium falciparum has been characterized. The partial sequence for the gene coding for this antigen (clone 281) reveals the presence of tandem repeats of eight amino acids which defines a new S-antigen serotype. Antibodies raised against the 281 recombinant clone reacted with a 140 kDa antigen by immunoblotting with parasite extracts and culture supernatants. The 140 kDa peptide was also identified by immunoprecipitation of metabolic labelled parasites. The 281 mouse antiserum was used to localize the antigen on parasite smears by indirect immunofluorescence assay and more precisely by immunoelectron microscopy. The S-antigen is localized within the parasitophorous vacuole. Furthermore, different isolates were examined for the presence of the Palo Alto S-antigen specificity.

Amino Acid Sequence↗
PubMed1988

Plasmodium vivax: karyotype polymorphism of field isolates.

Pulse-field gradient electrophoresis (PFG) has been applied to the karyotype analysis of Plasmodium vivax isolates obtained directly from infected patients in Sri Lanka. Detection of separated chromosomes was performed either by ethidium bromide staining of gels or by hybridization with a telomer specific probe. Each of the 15 different isolates examined exhibited a different chromosome migration pattern, indicating that a high level of polymorphism prevailed in wild populations of P. vivax. Chromosome size variation was further confirmed using a P. vivax chromosome-specific probe which also demonstrated that, in each isolate, the parasite population appeared to be homogeneous. These observations were made directly on parasites from infected blood, without the necessity for culture amplification, indicating that PFG can be used on a large scale for the epidemiological analysis of wild parasite populations.

Animals↗
PubMed1988

Plasmodium falciparum: analysis of karyotype polymorphism using chromosome-specific probes.

Chromosome size variation in Plasmodium falciparum has been examined using a double heterogenous pulse field gradient electrophoresis apparatus and a series of chromosome-specific probes. In the 11 different isolates analyzed the chromosomal markers always hybridized to the corresponding chromosome, indicating that translocations do not significantly contribute to chromosome size variations. Furthermore, despite probes specific for chromosomes 5 and 6 no evidence was obtained to support the hypothesis of a chromosome duplication involving these chromosomes. The double heterogenous electric field combined with longer pulse times allowed the genome to be resolved into a larger number of chromosomal bands and as a result permitted the more precise mapping of cloned genes.

Animals↗
PubMed1988

Chromosome size variation in the malaria parasite of rodents, Plasmodium chabaudi.

Pulsed field gradient gel electrophoresis has been used to identify at least 10 large DNA fragments in the genome of the rodent malaria species Plasmodium chabaudi. The fragments range in size from approximately 650 to 5000 kb. All the fragments contain sequences homologous to a P. berghei telomere probe, suggesting that they represent intact chromosomes. Ribosomal RNA genes and P. chabaudi cDNA sequences have been mapped to specific fragments. The fragments vary in size in different cloned isolates of the parasite. In a cross between two cloned parasites differing in the sizes of chromosomes 4 and 5, independent segregation of each chromosome occurred during meiosis.

Animals↗
PubMed1987

Karyotype comparison between P. chabaudi and P. falciparum: analysis of a P. chabaudi cDNA containing sequences highly repetitive in P. falciparum.

The molecular karyotypes of P. chabaudi and P. falciparum have been compared by pulse field gradient electrophoresis. P. chabaudi has 3 extra chromosomes in the 750-2000 Kb range although the overall number appears to be 14 as is the case for P. falciparum. The chromosomal location of the rRNA genes has been determined for P. chabaudi together with that of a 24 Kd antigen gene. The corresponding cDNA 443 may code for a protein unusually rich in tyrosine and contains sequences highly repetitive in P. falciparum.

Animals↗
PubMed1987

Characterization and complete nucleotide sequence of a 5.8S ribosomal RNA gene from Plasmodium falciparum.

The 5.8S and 5S rRNA components from the FCR-3/The Gambia strain of Plasmodium falciparum have been identified and the complete nucleotide sequence of a 5.8S ribosomal RNA gene determined. Unlike the 5S rRNA species, the 5.8S is a single homogeneous population of molecules of 157 nucleotides. Comparison of its nucleotide sequence with previously reported 5.8S rRNA sequences indicates that it is homologous to these molecules, but distantly related to them. The sequence of the 5.8S rRNA coding region from the pfrib-2 recombinant of the HG13 Gambian isolate of P. falciparum is identical.

Animals↗
PubMed1987

The polymorphic 11.1 locus of Plasmodium falciparum.

Clone pPF11.1 encodes a Plasmodium falciparum antigen expressed during the intraerythrocytic cycle and containing tandem repeats of a 9 amino acid unit. We report here an analysis of the genomic region specific for 11.1, which extends over 30 kb. It contains two blocks of repeats, spanning 13 kb and 9 kb. The restriction map suggests that the locus may result from a gene duplication. The 11.1 region is present in all P. falciparum strains examined so far. Southern analysis of 8 distinct isolates indicates that the locus is highly polymorphic. Thus the pPF11.1 repeats constitute a sensitive and discriminating probe to type P. falciparum strains.

Alleles↗
PubMed1987

Antigenic variation in parasitic protozoa.

Antigenic variation in the protozoan parasites responsible for malaria and African sleeping sickness is examined. Some of the molecular mechanisms responsible for the generation of new variant antigens are reviewed and the possible problems posed by this process in the development of vaccines against these parasites are discussed.

Animals↗
PubMed1986

Characterisation of a repetitive DNA sequence from the malaria parasite, Plasmodium falciparum.

A repetitive DNA fragment cloned from the malaria parasite, Plasmodium falciparum, has been analysed. It contains a 21 base pair sequence which occurs in multiple tandem repeats. Two clusters of the same repeat are found in opposite orientations on the same DNA fragment. The repetitive DNA provides an additional way to distinguish between different strains of parasite by hybridisation to genomic blots and may serve as a species-specific probe for diagnosis.

Animals↗