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Biomedical subjects

D Blair

Publications and source records attributed to D Blair.

At least 73 records · Page 4Linked to original sources
PubMed1995

Nuclear rDNA ITS sequence variation in the trematode genus Echinostoma: an aid to establishing relationships within the 37-collar-spine group.

The taxonomic history of members of the 37-collar-spine group within the genus. Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5.8S and ITS2 of 7 nominal species belonging to this group, Echinostoma trivolvis (Cort, 1914), E. revolutum (Frölich, 1802), E. caproni Richard, 1964, E. liei Jeyarasasingam et al. 1972, E. paransei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. hortense (Asada, 1926). Five of the eight species were clearly distinguishable using ITS data. Sequences from the remaining three taxa, E. caproni, E. sp.II and E. liei were identical to one another and the group containing these taxa was distant from other 37-collar-spine species on a phylogenetic tree. E. trivolvis and E. paraensei form a second, but less distinct group within the 37-collar-spine group. The resolution obtained using DNA sequencing will assist in the current reclassification of the group. It also provides a model for future work on sibling species.

Animals↗
PubMed1995

A molecular phylogeny of the genus Echinococcus.

Three nucleotide data sets, two mitochondrial (COI and ND1) and one nuclear (ribosomal ITS1), have been investigated in order to resolve relationships among species and strains of the genus Echinococcus. The data have some unusual properties in that mitochondrial heteroplasmy was detected in one strain of E. granulosus, and more than one class of ITS1 sequence variant can occur in a single isolate. The data failed to support the hypothesis that E. granulosus, as it is currently viewed, is a single valid species. Rather, the strains of E. granulosus seem to comprise at least three evolutionarily diverse groups, the sheep strain group, bovine strain group and horse strain group. Molecular distances between them are comparable to, or greater than, molecular evolutionary distances observed between recognized species. The affinities of the cervid strain of E. granulosus are unclear because of ambiguous data, but this strain does not appear to be ancestral to others. E. multilocularis may not be distinct from E. granulosus. However, the remaining two species. E. vogeli and E. oligarthrus appear distinct and rather distant from the first two. Based on the results presented here, taxonomic revision of the genus is clearly warranted.

Animals↗
PubMed1994

Genetic variation in the triploids of Japanese Fasciola species, and relationships with other species in the genus.

Twelve enzymes (encoded by 14 loci) in liver flukes of Fasciola species originating from Japan (parthenogenetic triploids), Korea (parthenogenetic diploids), the United States of America (USA) and Australia (all sexual diploids) were analysed using starch gel electrophoresis. Variation in electrophoretic patterns between samples was detected at fic enzyme loci (Ak, Got, Gpi, 6-Pgd and Pgm-2). Japanese worms (31, of which six were established as uniparental laboratory strains), which reproduce by parthenogenesis, exhibited three different isozyme patterns. This indicates that triploidy has arisen more than once in Japanese flukes. Japanese Fasciola sp. can be separated into three types on morphological grounds. For the six laboratory strains of Japanese worms, the parental morphological type was known. Each of the three isozyme patterns observed was restricted to one morphological type. Most alleles detected in the Japanese triploids were also found in diploid worms from the other countries: the only alleles not represented elsewhere were four at the Got locus and two at the Pgm locus. Flukes from a laboratory strain derived from a single Korean diploid worm resembled the Japanese worms in genotype more closely than did America (seven uniparental laboratory strains) or Australian (30 worms) specimens. Worms from the last two countries were closely related.

Animals↗
PubMed1994

Molecular genetic characterization of the cervid strain ('northern form') of Echinococcus granulosus.

We have used a number of molecular genetic approaches to characterize the cervid strain ('northern form') of Echinococcus granulosus. PCR-RFLP analysis of the nuclear ITS1 region of the rDNA repeat can readily distinguish the cervid form from other strains of E. granulosus. The complexity of the RFLP patterns obtained suggests that a number of distinct ITS1 types are present in this strain which may represent an inter-strain E. granulosus hybrid. Mitochondrial CO1 sequence of the cervid genotype was ambiguous at 18 positions and closely resembles a cluster of previously characterized E. granulosus genotypes, G1 (common, domestic sheep)/G2 (Tasmanian sheep)/G3 (buffalo). In contrast, mitochondrial ND1 sequence, although unique, suggests that the cervid form is most similar to strains represented by the G6 (camel)/G7 (pig) genotypes. We assume that the CO1 and ND1 sequences obtained for the cervid genotype are linked in a single mitochondrial genome although this is difficult to explain if conventional molecular genetics of mitochondrial DNA are assumed. Based on its unique ND1 sequence and ITS1 PCR-RFLP pattern, the cervid strain appears to represent a distinct genotype (designated G8) of E. granulosus.

Amino Acid Sequence↗
PubMed1993

Molecular variation in fasciolids and Paragonimus.

Molecular variation, both intra- and inter-specific, in fasciolids and Paragonimus has been detected in isozymes and other proteins, antigens and nucleic acid sequences. The use of such data is reviewed for studies on population genetics, taxonomy, phylogeny, immunodiagnosis, ontogeny and host-induced variation.

Animals↗
PubMed1993

Comparison of the second internal transcribed spacer (ribosomal DNA) from populations and species of Fasciolidae (Digenea).

The nucleotide sequence of the 3' end of the second internal transcribed spacer region (ITS2) was determined for four isolates of Fasciola hepatica, two isolates of Fasciola gigantica, one isolate of Fascioloides magna and one isolate of Fasciola sp. from Japan. Intraspecific sequence divergence was negligible. Sequence divergence between F. hepatica and F. gigantica was 2.8% and between Fasciola hepatica and Fascioloides magna was 13.2%. The sequence of Fasciola sp. from Japan matched closely that of F. gigantica. This study demonstrates variability in nucleotide sequence within the ITS2 region which allows discrimination between species of Fasciolidae.

Animals↗
PubMed1993

Affinities of the Gyliauchenidae: utility of the 18S rRNA gene for phylogenetic inference in the Digenea (Platyhelminthes).

18S rRNA sequences were analysed using parsimony and distance matrix methods to infer relationships among 8 species of trematodes. In particular, the disputed relationships of the digenean family Gyliauchenidae were examined. This family is regarded by some to be close to the Lepocreadiidae, and by others to be close to the Paramphistomidae. The data gave very strong support for placing the Gyliauchenidae close to the Lepocreadiidae, and almost no support for the alternative hypothesis. This support was found, regardless of the method of analysis, using data from different regions of the molecule as well as from the entire molecule. Morphological features are re-interpreted in the light of this conclusion.

Animals↗
PubMed1993

Phylogenetic position of Heronimus mollis (Digenea): evidence from 18S ribosomal RNA.

Most (1918bp) of the nucleotide sequence of the 18S ribosomal RNA gene of Heronimus mollis was determined. We aligned this sequence with 18S rRNA sequences from 7 other digeneans and an aspidobothrean. Using these data we explored the phylogenetic position of H. mollis. No support was found for the hypothesis that H. mollis is the sister taxon of the remaining digeneans examined here; similarly, no support was found for the hypothesis that H. mollis is closely related to the paramphistomes. These analysis together with the skewness of the frequency distribution of the lengths of 100,000 trees sampled randomly from the set of all possible trees (generated from these data) indicate that 18S rRNA sequences are valuable for phylogenetic inference in the Digenea.

Animals↗
PubMed1993

The phylogenetic position of the Aspidobothrea within the parasitic flatworms inferred from ribosomal RNA sequence data.

Sequence data from parts of the small subunit ribosomal RNA gene (18s rRNA) from an aspidobothrean and two digeneans have been added to a published data set which includes sequences from a number of parasitic and non-parasitic flatworms. Parsimony and distance matrix analyses of the data were carried out. Tests for particular clades were done using bootstrap resampling methods, and tests of particular topologies done using 4- and 5-taxon tests. The aspidobothrean Lobatostoma manteri emerges from near the base of the Neodermata, but whether as a sister group to the rest of the Neodermata or as a sister to the Digenea alone cannot be determined from the number of nucleotide sites available. Gyrocotyle is included with the cestodes in a very strongly supported clade in all analyses. There is evidence that the Monogenea is a paraphyletic group, although more data are needed to confirm this possibility.

Animals↗
PubMed1993

Time-to-contact judgment in the locomotion of adults and preschool children.

The hypothesis of Lee (1976)--that approach and deceleration toward a surface can be controlled through the rate of change of the optic variable tau--was examined for natural human locomotion. In Experiment 1, 12 adults were asked to perform locomotor tasks that required running at speed and then decelerating so that either the hand or head made a controlled contact with a door. In Experiment 2, 12 preschool children performed a relay-running task that required similar control. In Experiment 3, 12 children and 12 adults ran with a stick as an extension to their arm length and performed the same task. The results supported Lee's hypothesis for the initial phase of approach, but subjects switched to a separate adjustment phase 2 to 3 arm lengths from the target. Children did not adopt an appropriate tau strategy for collision avoidance and appeared unable to modify their approach strategy to allow for a hand-held stick.

Acceleration↗
PubMed1992

Genetic variants within the genus Echinococcus identified by mitochondrial DNA sequencing.

The pattern of species and strain variation within the genus Echinococcus is complex and controversial. In an attempt to characterise objectively the various species and strains, the sequence of a region of the mitochondrial cytochrome c oxidase subunit I (CO1) gene was determined for 56 Echinococcus isolates. Eleven different genotypes were detected, including 7 within Echinococcus granulosus, and these were used to categorise the isolates. The 4 generally accepted Echinococcus species were clearly distinguishable using this approach. In addition, the consensus view of the strain pattern within E. granulosus, based on a variety of criteria of differentiation, was broadly upheld. Very little variation was detected within Echinococcus multilocularis. Remarkable intra-strain homogeneity was found at the DNA sequence level. This region of the rapidly evolving mitochondrial genome is useful as a marker of species and strain identity and as a preliminary indication of evolutionary divergence within the genus Echinococcus.

Amino Acid Sequence↗
PubMed1992

Tumorigenicity of the met proto-oncogene and the gene for hepatocyte growth factor.

The met proto-oncogene is the tyrosine kinase growth factor receptor for hepatocyte growth factor/scatter factor (HGF/SF). It was previously shown that, like the oncogenic tpr-met, the mouse met proto-oncogene transforms NIH 3T3 cells. We have established NIH 3T3 cells stably expressing both human (Methu) and mouse (Metmu) met proto-oncogene products. The protein products are properly processed and appear on the cell surface. NIH 3T3 cells express endogenous mouse HGF/SF mRNA, suggesting an autocrine activation mechanism for transformation by Metmu. However, the tumor-forming activity of Methu in NIH 3T3 cells is very low compared with that of Metmu, but efficient tumorigenesis occurs when Methu and HGF/SFhu are coexpressed. These results are consistent with an autocrine transformation mechanism and suggest further that the endogenous murine factor inefficiently activates the tumorigenic potential of Methu. The tumorigenicity observed with reciprocal chimeric human and mouse receptors that exchange external ligand-binding domains supports this conclusion. We also show that HGF/SFhu expressed in NIH 3T3 cells produces tumors in nude mice.

3T3 Cells↗
PubMed1992

Population structure of Lankatrematoides gardneri (Digenea: Opisthotrematidae) in the pancreas of the dugong (Dugong dugon) (Mammalia: Sirenia).

The distribution among size and reproductive classes of the digenean Lankatrematoides gardneri was recorded from the pancreatic ducts of 41 dugongs from the Gulf of Papua, Papua New Guinea. Infrapopulation sizes ranged from 5 to 921 worms and showed no correlation with host age, sex, or month of capture. Immature worms tended to be concentrated in intermediate size classes, the largest immatures being no more numerous than matures. The mean proportion of mature worms in the 29 infrapopulations containing them was small (9.8%). Mature worms were significantly greater in mass than the largest immatures. There is evidence of an interaction between the presence or absence of mature worms and the distribution of immatures among classes.

Age Factors↗