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Biomedical subjects

R B Gasser

Publications and source records attributed to R B Gasser.

At least 127 records · Page 7Linked to original sources
PubMed1997

Echinococcus granulosus myophilin--relationship with protein homologues containing "calponin-motifs".

Myophilin, a smooth-muscle protein of the tapeworm Echinococcus granulosus, was recently postulated to be a member of the calponin family of proteins. A detailed genetic analysis revealed that 17 proteins had significant homology with the amino-acid sequence of the N-terminal region of myophilin and/or possessed one or more "calponin-motifs". Comparison of the amino-acid sequences of the N-terminus showed that the homologous proteins clustered into distinct groups based on the number of calponin-motifs. The calponin-motif of myophilin was genetically more similar to that present in the muscle protein mp20 of Drosophila melanogaster than to those in any other homologous proteins of vertebrates. The existence of a distinct motif which is "conserved" in other proteins across a range of species suggests an important functional role for the motif.

Amino Acid Sequence↗
PubMed1997

Myophilin of Echinococcus granulosus: isoforms and phosphorylation by protein kinase C.

Myophilin is a muscle-associated antigen of the taeniid cestode Echinococcus granulosus. This protein shows a high amino acid sequence homology with calponins and calponin-like proteins, which are proposed to be associated with the regulation of smooth muscle contraction. In order to provide supportive evidence for a relationship between these proteins, we characterized myophilin using electrophoretic, biochemical and molecular biological approaches. Two-dimensional protein electrophoretic separation of E. granulosus larval proteins defined 4 isoelectric isoforms of myophilin (alpha, beta, gamma and delta), which appeared to be a consequence of post-translational modification of a single gene product. It was also demonstrated biochemically that E. granulosus myophilin undergoes specific phosphorylation in vitro by protein kinase C (PKC). Finally, myophilin homologues were identified in extracts of Taenia hydatigena and T. ovis by immunoblot. A partial cDNA of the closely related species, E. multilocularis, was isolated by cloning procedures and showed 99% homology with the E. granulosus myophilin gene. The similarities of E. granulosus myophilin with calponins in their tissue localization, protein isoforms patterns, ability to be phosphorylated in vitro by PKC, and the relatively conserved nature of the protein among related parasites suggest that myophilin may be associated with smooth muscle contraction.

Animals↗
PubMed1997

Characterization of Oesophagostomum bifurcum and Necator americanus by PCR-RFLP of rDNA.

Esophagostomiasis in humans due to infection with Oesophagostomum bifurcum (nodular worm) is of major human health significance in northern Togo and Ghana, where Necator americanus (human hookworm) also exists at high prevalence. Yet, very little is known about the transmission patterns of O. bifurcum, which is in part due to the difficulties in diagnosis and in differentiating some life-cycle stages of O. bifurcum from N. americanus using morphological features. As a first step toward developing a molecular-diagnostic assay, it was evaluated whether ribosomal (r)DNA could provide genetic markers for the identification of O. bifurcum and N. americanus to species. Internal transcribed spacer rDNA (plus flanking and intervening sequences) was analyzed by polymerase chain reaction-linked restriction fragment length polymorphism (PCR-RFLP) using several restriction endonucleases. The analysis showed that there was no detectable intraspecific difference in the size of the PCR products among multiple samples, that there was a consistent size difference in the products (of 110 bp or 350 bp, depending on region amplified) between the species, and that there was no significant variation in restriction patterns within each species. These results indicate that the rDNA spanning the internal transcribed spacers provides useful genetic markers for the identification of O. bifurcum and N. americanus to species, which has important implications for developing PCR-based tools to study the epidemiology and population biology of O. bifurcum.

Animals↗
PubMed1997

Prevalence of antibodies to Neospora caninum in different canid populations.

A total of 1,554 dogs from 5 countries on 3 continents were tested for antibodies to Neospora caninum using an indirect fluorescent antibody test. In Australia, overall, 42/451 (9%, 95% confidence interval [CI] 6-12%) dogs were seropositive (Melbourne 11/207 [5%, 95% CI 2-9%]; Sydney 18/150 [12%, 95% CI 7-18%]; Perth 13/94 [14%, 95% CI 8-22%]). Antibodies to N. caninum were also detected in dogs in South America (Uruguay [20%, 95% CI 16-24%, n = 414]) and sub-Saharan Africa (Tanzania [22%, 95% CI 12-36%, n = 49]). In contrast, only 1 of 500 dogs tested from the Falkland Islands and none of 140 dogs from Kenya was seropositive. Of wild canids, 1/54 (2%, 95% CI 0-10%) British foxes and 15/169 (9%, 95% CI 5-14%) Australian dingoes had antibodies to N. caninum.

Africa, Eastern↗
PubMed1996

Rapid delineation of closely-related filarial parasites using genetic markers in spacer rDNA.

Two closely-related species of filarial parasite, Litomosoides galizai and L. sigmodontis, were characterised using a polymerase chain reaction-linked restriction fragment length polymorphism (PCR-RFLP) technique. The rDNA region spanning the first and second internal transcribed spacers as well as the 5.8S gene (ITS+) was amplified by PCR from each of the species using conserved primers to the 18S and 28S ribosomal genes, digested separately with a range of restriction endonucleases and the fragments separated by agarose gel electrophoresis. PCR-RFLP of ITS+ using endonucleases Alu I, Cfo I, Dra I, Rsa I and Vsp I produced characteristic patterns for each species. No variation in RFLP patterns was detected among different DNA sample preparations or the sexes of each species. The present study demonstrates that the ITS+ provides genetic markers for the differentiation of L. galizai from L sigmodontis and suggests that internal transcribed spacer rDNA may provide species markers for other filarioid nematodes. Such markers have implications for diagnosis and for studying the biology, pathogenesis and systematics of filarial parasites.

Animals↗
PubMed1996

Use of RAPD for the detection of genetic variation in the human blood fluke, Schistosoma japonicum, from mainland China.

A random amplified polymorphic DNA (RAPD) technique using 16 decamer oligonucleotide primers was employed to characterize isolates of Schistosoma japonicum from seven geographical locations (Sj1: Zhejiang; Sj2: Anhui; Sj3: Jiangxi; Sj4: Hunan; Sj5: Hubei; Sj6: Sichuan; Sj7: Yunnan) of the People's Republic of China. Distinct differences between some isolates were reproducibly detected in RAPD patterns produced using five of the primers. The analyses showed that both Sj6 and Sj7 were quite distinct genetically from Sj1-Sj5 based on the presence/absence of particular bands (A10-200 bp, A9-220 bp, B17-520 bp, P205-680 bp and P235-930 bp). These findings are in line with previous reports on the biological, biochemical, immunological and chemotherapeutic differences of S. japonicum from Sichuan and Yunnan compared with other geographical regions. The present study showed, based on RAPD profiles, that genetic differences exist within S. japonicum from mainland China. This finding may have important implications for studying the population biology, epidemiology and clinical forms of the disease in China, as well as for developing vaccines and diagnostic test systems.

Animals↗
PubMed1996

Species markers for equine strongyles detected in intergenic rDNA by PCR-RFLP.

Five species of equine strongyle belonging to the subfamily Strongylinae (Strongylus edentatus, S. equinus, S. vulgaris, Oesophagodontus robustus and Triodontophorus serratus) and 11 species belonging to the subfamily Cyathostominae (Poteriostomum imparidentatum, P. ratzii, Cylicocyclus insignis, Cc. leptostomus, Cc. nassatus, Cylicostephanus calicatus, Cs. longibursatus, Cs. goldi, Cyathostomum catinatum, Cy. labiatum and Cy. pateratum) were characterized using a polymerase chain reaction-linked restriction fragment length polymorphism technique (PCR-RFLP). Internal transcribed spacer ribosomal DNA was amplified from genomic DNA by polymerase chain reaction (PCR) using conserved primers, digested separately with six restriction endonucleases (AluI, BfaI, CfoI, Hae III, VSpI and XbaI) and the fragments separated by agarose gel electrophoresis. The PCR products of the three Strongylus species were approx. 90-100 bp smaller in size compared with those of the other 13 species. The PCR-RFLP analysis of the rDNA region spanning the first and second internal transcribed spacers plus the 5.85 rDNA gene (ITS+) produced characteristic patterns for each of the 16 species examined, and no variation in RFLP patterns was detected within the species Cy. catinatum, where multiple isolates were analysed. The study demonstrates that the internal transcribed spacer sequences provide genetic markers for the species identification of a range of equine strongyles. These markers will be of use for the identification of egg and larval stages, where morphological characters alone are unreliable. The results also indicate that the spacer sequences will be of use to study the systematics of equine strongyles.

Animals↗
PubMed1996

Antibody responses of patients with cystic hydatid disease to recombinant myophilin of Echinococcus granulosus.

Hydatid patients were investigated for the presence of specific serum antibodies against a recombinant Echinococcus granulosus antigen, designated myophilin. The clinical history of each patient was examined to determine any correlation between factors such as cyst location and medical treatment on the presence or absence of antibodies to myophilin. Specific antibodies against recombinant myophilin were detected by Western blot analysis in 38.8% (7 of 18) of the hydatid patients examined. These patients also had the highest titres in ELISA against sheep hydatid cyst fluid antigen. There was an association between the presence of antibodies to myophilin and the patients having undergone recent treatment by chemotherapy and/or surgery, suggesting that the destruction of hydatid cysts may lead to an immune response against myophilin.

Adult↗
PubMed1996

Genetic markers in ribosomal DNA for hookworm identification.

Polymerase chain reaction-linked restriction fragment length polymorphism (PCR-RFLP) analysis of ribosomal (r) DNA was conducted on Uncinaria stenocephala, Ancylostoma caninum, A. tubaeforme and A. ceylanicum. The rDNA region spanning the first and second internal transcribed spacers (ITS1 and ITS2) plus the 5.8S (ITS+) gene was amplified by PCR from each of the species, digested separately with 9 restriction endonucleases and the fragments separated by agarose gel electrophoresis. Characteristic PCR-RFLP patterns were produced for each morphologically defined species using some of the endonucleases. The present study demonstrated that the ITS+ provides genetic markers for the delineation of each species examined and suggests that this region of rDNA will be useful for the identification of other hookworms from a range of hosts. The results are likely to have important implications for studying the genetic structure of hookworm populations, the systematics and the epidemiology of hookworm infections.

Ancylostomatoidea↗
PubMed1996

Strongylus asini (Nematoda, Strongyloidea): genetic relationships with other Strongylus species determined by ribosomal DNA.

Genomic DNA was isolated from adult Strongylus asini collected from zebra. The second ribosomal transcribed spacer (ITS-2) was amplified and sequenced using polymerase chain reaction (PCR) based techniques. The DNA sequence was compared with previously published data for 3 related Strongylus species. A PCR-linked restriction fragment length polymorphism method allowed the 4 species to be differentiated unequivocally. The ITS-2 sequence of S. asini was found to be more similar to those of S. edentatus (87.1%) and S. equinus (95.3%) than to that of S vulgaris (73.9%). This result confirms that S. Asini and S vulgaris represent separate species and supports the retention of the 4 species within 1 genus.

Animals↗
PubMed1996

The structure of the community of strongyloid nematodes of domestic equids.

The community structure exhibited by strongyloid nematodes from the large intestines of horses was examined using data from autopsies of 150 horses. Thirty-one species of nematodes were encountered, but they were not clearly divisible into core and satellite species. Multiple congeneric, consubfamilial and confamilial species were a prominent feature of the community and were more common than singleton infections. Multivariate analyses provided evidence of a stable community of helminths dominated by positive interactions but with few negative interactions, suggesting the absence of competition within the community.

Animals↗
PubMed1996

The ITS-2 rDNA of Teladorsagia circumcincta, T. trifurcata and T. davtiani (Nematoda: Trichostrongylidae) indicates that these taxa are one species.

There remains uncertainty about the species status of Teladorsagia circumcincta, T. davtiani and T. trifurcata. In this study, the second internal transcribed spacer (ITS-2) sequences of these taxa and 2 other members within the same subfamily (Ostertagiinae) were examined. Although some sequence variation was detected between and within single worms of each taxon of Teladorsagia, no unequivocal base differences were detected among their consensus ITS-2 sequence. In comparison, there was 9% sequence difference between O. ostertagi and O. leptospicularis and 13-15% difference between the genera Teladorsagia and Ostertagia. These findings indicate that T. circumcincta, T. davtiani and T. trifurcata represent a single species, T. circumcincta.

Animals↗
PubMed1996

First record of Giardia in cattle in Denmark.

Faecal samples from asymptomatic dairy cows and calves from a farm on the Island Falster, Denmark, were examined by a sucrose gradient flotation technique. Giardia cysts were found in 7.6% of the 92 samples, and estimated cyst excretion rates ranged from 50-200 cysts per gram faeces. Given that Giardia has the potential to cause clinical disease in cattle and to be transmitted to other animal species and humans, finding the parasite in cattle may be of major epidemiological significance. Future work should focus on elucidating the pathogenicity, transmission patterns and the genetic structure of Giardia populations in cattle in Denmark.

Animals↗
PubMed1995

Characterisation of taeniid cestode species by PCR-RFLP of ITS2 ribosomal DNA.

Seven species of taeniid cestode (Echinococcus granulosus. E. multilocularis, Taenia hydatigena, T. ovis, T. pisiformis, T. multiceps and T. serialis) were characterised using a polymerase chain reaction-based restriction fragment length polymorphism technique (PCR-RFLP). The second internal transcribed spacer of ribosomal DNA (ITS2) was amplified from various geographical isolates of each of the seven species, digested separately with four restriction endonucleases and the fragments were separated by conventional agarose gel electrophoresis. PCR-RFLP produced characteristic patterns for each taeniid species examined. No variation in RFLP patterns was observed among different isolates of E. multilocularis and the species of Taenia, but distinct intraspecific variation was detected in E. granulosus. The present study indicates the usefulness of the PCR-RFLP of ITS2 for systematic, epidemiological and diagnostic purposes.

Animals↗
PubMed1995

Differences in the second internal transcribed spacer (ribosomal DNA) between five species of Trichostrongylus (Nematoda: Trichostrongylidae).

The second internal transcribed spacer (ITS-2) of the ribosomal DNA of 5 species of Trichostrongylus has been sequenced. The ITS-2 of the 5 species was 237 or 238 bases in length, and had a GC content of approximately 30%. No evidence of intraspecific variation was detected in the ITS-2 sequence of T. colubriformis, T. vitrinus or T. retortaeformis, irrespective of the life cycle stage examined. There was evidence, however, of variation at five positions in the ITS-2 sequence of T. vitrinus samples and at one position in T. axei, indicating intra-individual variation in the sequence of different copies of the ribosomal DNA. Nonetheless, there were consistent sequence differences between the five Trichostrongylus species examined. The level of interspecific differences in nucleotide sequence was low (1.3-7.6%), with the species infecting birds (T. tenuis) being genetically more different to the four species found in mammals. Some of the nucleotide differences between species occurred at the recognition sites of endonucleases, which makes them of important diagnostic value for species identification. Also of significance are the recognition sites for several enzymes located within the regions of sequence homology for the five species of Trichostrongylus. These may prove useful in distinguishing between genera of trichostrongyle nematodes.

Animals↗
PubMed1995

Differences in a ribosomal DNA sequence of Strongylus species allows identification of single eggs.

In the current study, molecular techniques were evaluated for the species identification of individual strongyle eggs. Adult worms of Strongylus edentatus, S. equinus and S. vulgaris were collected at necropsy from horses from Australia and the U.S.A. Genomic DNA was isolated and a ribosomal transcribed spacer (ITS-2) amplified and sequenced using polymerase chain reaction (PCR) techniques. The length of the ITS-2 sequence of S. edentatus, S. equinus and S. vulgaris ranged between 217 and 235 nucleotides. Extensive sequence analysis demonstrated a low degree (0-0.9%) of intraspecific variation in the ITS-2 for the Strongylus species examined, whereas the levels of interspecific differences (13-29%) were significantly greater. Interspecific differences in the ITS-2 sequences allowed unequivocal species identification of single worms and eggs using PCR-linked restriction fragment length polymorphism. These results demonstrate the potential of the ribosomal spacers as genetic markers for species identification of single strongyle eggs from horse faeces.

Animals↗