PubMed Health⌕ Search

Biomedical subjects

I Beveridge

Publications and source records attributed to I Beveridge.

At least 73 records · Page 4Linked to original sources
PubMed1997

The 5.8S rDNA sequences of 18 species of bursate nematodes (order Strongylida): comparison with rhabditid and tylenchid nematodes.

The 5.8S rDNA sequences of 18 species of bursate nematode were 153 bp in length and had a G + C content of 47-50%. Interspecific differences in rDNA sequence among the bursate nematodes were low (0-5.2%), but the extent of the sequence differences between the parasitic bursate nematodes, a free-living rhabditid nematode and 2 species of parasitic tylenchid nematodes (12-33%) suggests that the 5.8S rRNA gene may provide useful phylogenetic information with respect to the relationships of the different orders within the phylum Nematoda.

Animals↗
PubMed1997

Molecular delineation of Cylicocyclus nassatus and C. ashworthi (Nematoda:Strongylidae).

The nucleotide sequences of the first internal transcribed spacer (ITS-1), 5.8S gene and second internal transcribed spacer (ITS-2) of ribosomal DNA have been determined for Cylicocyclus nassatus, C. ashworthi and C. insignis. Pairwise comparisons revealed sequence differences between the taxa ranging from 3.8 to 6.2% for the ITS-2 and 2.2-2.7% for the ITS-1. For the ITS-1, the level of the sequence difference between C. ashworthi and C. nassatus (2.2%) was equivalent to that between C. nassatus and C. insignis (2.2%), indicating that C. ashworthi and C. nassatus represent separate species. Theoretical restriction maps were constructed from the sequence data, and a polymerase chain reaction-linked restriction fragment length polymorphism (PCR-linked RFLP) technique was established to unequivocally distinguish C. ashworthi from C. nassatus.

Animals↗
PubMed1997

Evidence for hybridisation between Paramacropostrongylus iugalis and P. typicus (Nematoda:Strongyloidea) in grey kangaroos, Macropus fuliginosus and M. giganteus, in a zone of sympatry in eastern Australia.

Specimens of Paramacropostrongylus iugalis and P. typicus, collected from eastern (Macropus giganteus) and western (M. fuliginosus) grey kangaroos in New South Wales and Queensland, were examined morphologically and electrophoretically at 4 enzyme loci previously demonstrated to be diagnostic between the 2 species. Collections of P. iugalis from M. giganteus from outside the zone of sympatry of the 2 kangaroo species conformed electrophoretically and morphologically with previous studies. Within the zone of sympatry, the 2 nematode species were distinguishable electrophoretically, with most P. iugalis occurring in M. giganteus and all P. typicus occurring in M. fuliginosus. Some specimens of P. iugalis were identified in M. fuliginosus and, in both host species, nematodes were encountered with electrophoretic profiles intermediate between P. iugalis and P. typicus. The frequent occurrence in these specimens of heterozygotes suggested that the genetic barriers between the 2 nematode species were not complete and that genetic interchange (i.e. hybridisation) was occurring.

Alleles↗
PubMed1997

An electrophoretic analysis of patterns of speciation in Cloacina clarkae, C. communis, C. petrogale and C. similis (Nematoda:Strongyloidea) from macropodid marsupials.

An electrophoretic study was conducted on Cloacina clarkae, C. communis, C. petrogale and C. similis based on 19 enzyme loci. C. communis was widely distributed in Macropus robustus, showing some genetic variation among populations but occasionally switching to other macropodid hosts (M. agilis, M. antilopinus). C. similis occurred in members of the Petrogale penicillata complex, Macropus dorsalis and Thylogale billardierii, but showed no evidence of genetic differentiation in spite of its occurrence in different host species and in geographically distinct regions of Australia. C. clarkae from Macropus eugenii was genetically indistinguishable from C. similis and was considered synonymous with it. C. petrogale occurred in a similarly diverse range of hosts and geographical regions to C. similis, but was represented electrophoretically as 4 distinct genetic species, 1 in Petrogale assimilis, a second in P. lateralis purpureicollis, a third in Macropus parryi in Queensland and a fourth in M. eugenii in South Australia. Although the host and geographical ranges of C. similis and C. petrogale are analogous, the genetic uniformity of the former and diversity of the latter illustrate the incomplete understanding we have of the immediate causes of speciation in nematodes.

Alleles↗
PubMed1997

Phylogenetic relationships of Australian strongyloid nematodes inferred from ribosomal DNA sequence data.

The sequence of the second internal transcribed spacer of the ribosomal DNA was determined for the following strongyloid nematodes: Cylicocyclus insignis, Chabertia ovina, Oesophagostomum venulosum, Cloacina communis, Cloacina hydriformis, Labiostrongylus labiostrongylus, Parazoniolaimus collaris, Macropostrongylus macropostrongylus, Macropostrongylus yorkei, Rugopharynx australis, Rugopharynx rosemariae, Macropostrongyloides baylisi, Oesophagostomoides longispicularis and Paramacropostrongylus toraliformis, and compared with published sequences for species of Strongylus and for Hypodontus macropi. The resultant phylogenetic trees supported current hypotheses based on morphological evidence for the separation of the families Strongylidae and Chabertiidae, but did not support the separation of the endemic Australian genera as a distinctive clade within the Chabertiidae. The implications of this finding for the phylogenetic origins of the Australian strongyloids are discussed.

Animals↗
PubMed1997

Abnormal spicule development in a laboratory strain of trichostrongylus vitrinus

The occurrence of specimens in a laboratory strain of Trichostrongylus vitrinus exhibiting unusual spicules resembling those of T. minor and T. angistris is reported and the abnormal spicules described. The specimens include individuals with one spicule typical of T. vitrinus and the other spicule of the abnormal type. Possible reasons for the occurrence of such abnormalities are discussed.

Journal Article↗
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

Development of morphological changes and ileal glucagon gene expression in the small intestine of lambs infected with Trichostrongylus colubriformis.

To investigate the consequences of subclinical Trichostrongylus colubriformis infection on the intestinal mucosa and the associated changes in entero-glucagon gene expression, sheep were infected with 30000 larvae and killed 5, 10, 15 or 20 days after infection. Histological and cytological changes were examined. In the main site of infection, the upper duodenum, villous atrophy associated with crypt hyperplasia developed gradually. Cytological changes in the enterocytes appeared concurrently, characterized by a progressive reduction in brush border and in the number of ribosomes in the cytoplasm, changes in the internal structure of mitochondria, and enlargement of the intercellular spaces. Neither histological nor cytological modifications were found before day 15. At the same time, villous hypertrophy developed distally, beyond the main site of infection; this was interpreted as an adaptive response to parasitism. Enteroglucagon gene expression in the ileum was measured in parallel with the mucosal changes but did not reveal any difference between infected and control sheep. The results indicate that this gastrointestinal hormone does not have a major role in the response to nematode parasitism.

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↗
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 morphologically indistinguishable species within the Hypodontus macropi complex (Nematoda: Strongyloidea).

The nucleotide sequence of the second internal transcribed spacer (ITS-2) from ribosomal DNA has been determined for 3 members of the Hypodontus macropi species complex. Sequences were compared from nematodes collected from 3 species of Australian macropodid marsupial, Petrogale persephone, Macropus robustus robustus and Thylogale billardierii. The ITS-2 of each operational taxonomic unit ranged from 287 to 292 bases in length, and had a GC content of 36.6-40.1%. Differences in nucleotide sequence between nematodes from the different host species ranged from 25.0% to 28.3%. The data suggest that H. macropi from P. persephone represents a different species to those in M. r. robustus and T. billardierii. The unique feature of this study is that it represents a comparison of the ribosomal DNA sequences of nematode species which are morphologically indistinguishable but which have been demonstrated to be genetically distinct (i.e. cryptic) species based on electrophoretic data. The results also demonstrate further that morphological characters alone are often not adequate for species recognition. Differences between these 3 species of H. macropi in their recognition sites for restriction endonucleases, indicates that a PCR-RFLP approach could be used, in conjunction with allozyme electrophoresis, to establish how many species are present within the H. macropi complex.

Animals↗
PubMed1995

The prevalence and epidemiology of gastrointestinal parasites of horses in Victoria, Australia.

A quantitative post mortem study of 150 horses from Victoria was conducted to determine the prevalence and epidemiology of gastrointestinal parasites. A total of 42 species of metazoan parasite was found. The following species of non-cyathostome parasite were found (% prevalence): Trichostrongylus axei (51%); Habronema muscae (13%); H. majus (2%); Draschia megastoma (5%); Gastreophilus intestinalis (81%); G. nasalis (29%); Parascaris equorum (5%); Anoplocephala perfoliata (29%); Fasciola hepatica (0.7%); Oxyuris equi (7%); Strongylu vulgaris (23%); S. edentatus (23%); S. equinus (3%); Craterostomum acuticaudatum (7%); Triodontophorus serratus (8%); T. tenuicollis (8%); T. brevicauda (3%). Ninety-five per cent of horses were infected with gut-wall encysted stages of cythostomes with a mean intensity of 113,000 larvae per horse. Ninety-three per cent of all horses harboured adult cyathosome worms; 24 species representing 6 genera were found. The 3 most prevalent species were Cylicostephanus longiburstatus (76%); Cyathostomum catinatum (68%) and Cylicocyclus nassatus (54%). Seventeen species of strongyle were present in high abundance, which allowed their site distribution in the large intestine to be determined. Twelve species preferred the large colon to the small colon and caecum, and the remaining 5 species preferred the caecum. Statistical analysis of the parasitological data set allowed effects of sex, age, type, and physical condition of the horse as well as the season and environment on the prevalence and mean intensity of infection to be determined.

Age Factors↗
PubMed1994

Comparative ultrastructure of the cuticle of trichostrongyle nematodes.

The ultrastructure of the cuticle was examined in Austrostrongylus victoriensis, Patricialina birdi and Woolleya monodelphis (Herpetostrongylidae) from marsupials, Paraustrostrongylus ratti (Herpetostrongylidae) from rodents, Nippostrongylus magnus and Odilia bainae (Heligmonellidae) from rodents, Cooperia oncophora and Camelostrongylus mentulatus (Trichostrongylidae) from ruminants, and Nematodirus spathiger (Molineidae) from ruminants. The principal cuticular layers described previously were present in all species investigated. Major differences in the shape and composition of cuticular struts were observed as well as differences in components of the median zone of the cuticle, including the fluid-filled regions present in several species. Several different types of strut were observed. Although strut structure within the Heligmonellidae appeared to be constant, there were variations within both the Herpetostrongylidae and Trichostrongylidae. In Nem. spathiger the cuticular ridges lacked struts. The diversity of structures found in the species examined suggests that more extensive comparative studies of the trichostrongyle cuticle are warranted.

Animals↗
PubMed1994

The origins and evolutionary expansion of the Strongylida (Nematoda).

The Strongylida are thought to have arisen from free-living rhabditoid nematodes, but the relationships between the major groupings within the Strongylida, the Strongylina, the Metastrongylina, Trichostrongylina and the Ancylostomatina are far from clear in spite of the abundance of morphological data now available for analysis. Evolutionary mechanisms including co-evolution, host switching, host dispersal, use of intermediate hosts, various sites of localisation within the definitive host and modifications of life-cycle strategies appear to have been utilised in the expansion of the Strongylida, with different mechanisms predominating in different families or superfamilies. Co-evolution appears to have been a major mode of evolution in the Strongylina, in contrast to the Trichostrongylina, which have used host dispersal and host-switching to great advantage. The phylogeny of the Ancylostomatina shows little association with host evolution, but does match the feeding preferences of the hosts. The Metastrongylina have utilised intermediate hosts and life cycle modifications including a shift to extra-intestinal sites as major means of diversification, in contrast to the other sub-orders. The review, while indicating much progress in our understanding of the phylogeny of the Strongylida, also reveals that enormous gaps still exist, and emphasises the tentative nature of many of the phylogenetic hypotheses tendered to date.

Animals↗
PubMed1993

Sibling species within Macropostrongyloides baylisi (Nematoda: Strongyloidea) from macropodid marsupials.

Macropostrongyloides baylisi from four different species or subspecies of host were analysed electrophoretically at 27 enzyme loci. The results revealed the existence of two species, one in Macropus giganteus and the other in M. robustus robustus, M.r. erubescens and M.r. parryi, that had fixed genetic differences at 33% of loci. Populations of nematodes from two subspecies of M. robustus, M.r. robustus from Queensland and M.r. erubescens from South Australia, had fixed genetic differences at two (7.4%) of 27 loci and were considered to belong to the same species. No fixed genetic differences were detected between nematodes from M. parryi and M.r. robustus. A discriminant function analysis of morphological data assigned 96% of specimens to groups defined on the basis of the host species or subspecies from which they were obtained. This separation of Ma. baylisi into host-specific groups did not, however, totally correlate with the electrophoretic data. The species of M. baylisi in M. giganteus was genetically more distinct from the sibling species in M. robustus/M. parryi than to a related but morphologically dissimilar nematode, Ma. yamagutii from M. fuliginosus. This suggests an evolutionary parallel between host and parasite at the genetic level which is not reflected by morphological differences.

Alleles↗
PubMed1993

Lack of intraspecific variation in the second internal transcribed spacer (ITS-2) of Trichostrongylus colubriformis ribosomal DNA.

The nucleotide sequence of the second internal transcribed spacer (ITS-2) was determined for three populations of the parasitic nematode Trichostrongylus colubriformis which differed in their susceptibility to benzimidazole anthelmintics and/or in their geographical origin. No intraspecific variation was found in the ITS-2 sequence, indicating that this region of rDNA is inadequate to discriminate between resistant and susceptible populations of T. colubriformis, but it may prove useful for distinguishing between species of Trichostrongylus.

Animals↗
PubMed1992

Apparent lack of genetic variation within Pelecitus roemeri (Nematoda: Filarioidea) from three Australian species of macropodid marsupial.

An electrophoretic study of Pelecitus roemeri from Macropus robustus, M. giganteus and Wallabia bicolor revealed no genetic differences at 23 enzyme loci. The genetic data support the existing morphological evidence that P. roemeri from these three hosts represents a single species. The data show no genetic variation between nematodes from the same or different host species collected in northern and southern Australia. This result is discussed briefly in relation to Price's model of parasite speciation.

Animals↗