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N J Campbell

Publications and source records attributed to N J Campbell.

At least 19 recordsLinked to original sources
PubMed2001

A total-evidence phylogeny of ticks provides insights into the evolution of life cycles and biogeography.

We inferred the phylogeny of 33 species of ticks from the subfamilies Rhipicephalinae and Hyalomminae from analyses of nuclear and mitochondrial DNA and morphology. We used nucleotide sequences from 12S rRNA, cytochrome c oxidase I, internal transcribed spacer 2 of the nuclear rRNA, and 18S rRNA. Nucleotide sequences and morphology were analyzed separately and together in a total-evidence analysis. Analyses of the five partitions together (3303 characters) gave the best-resolved and the best-supported hypothesis so far for the phylogeny of ticks in the Rhipicephalinae and Hyalomminae, despite the fact that some partitions did not have data for some taxa. However, most of the hidden conflict (lower support in the total-evidence analyses compared to that in the individual analyses) was found in those partitions that had taxa without data. The partitions with complete taxonomic sampling had more hidden support (higher support in the total-evidence analyses compared to that in the separate-partition analyses) than hidden conflict. Mapping of geographic origins of ticks onto our phylogeny indicates an African origin for the Rhipicephalinae sensu lato (i.e., including Hyalomma spp.), the Rhipicephalus-Boophilus lineage, the Dermacentor-Anocentor lineage, and the Rhipicephalus-Booophilus-Nosomma-Hyalomma-Rhipicentor lineage. The Nosomma-Hyalomma lineage appears to have evolved in Asia. Our total-evidence phylogeny indicates that (i) the genus Rhipicephalus is paraphyletic with respect to the genus Boophilus, (ii) the genus Dermacentor is paraphyletic with respect to the genus Anocentor, and (iii) some subgenera of the genera Hyalomma and Rhipicephalus are paraphyletic with respect to other subgenera in these genera. Study of the Rhipicephalinae and Hyalomminae over the last 7 years has shown that analyses of individual datasets (e.g., one gene or morphology) seldom resolve many phylogenetic relationships, but analyses of more than one dataset can generate well-resolved phylogenies for these ticks.

Animals↗
PubMed2001

Recurrent gains and losses of large (84-109 bp) repeats in the rDNA internal transcribed spacer 2 (ITS2) of rhipicephaline ticks.

We studied the internal transcribed spacer 2 (ITS2) in twenty-two spp. of ticks from the subfamily Rhipicephalinae. A 104-109 base pair (bp) region was imperfectly repeated in most ticks studied. Mapping the number of repeat copies on to a phylogeny from the ITS2 showed that there have been many independent gains and losses of repeats. Comparison of the sequences of the repeat copies indicated that in most taxa concerted evolution had played little if any role in the evolution of these regions, as the copies clustered by sequence position rather than species. In our putative secondary structure, each repeat copy can fold into a distinct and almost identical stem-loop complex; a gain or loss of a repeat copy apparently does not impair the function of the ITS2 in these ticks.

Animals↗
PubMed2001

Numerous gene rearrangements in the mitochondrial genome of the wallaby louse, Heterodoxus macropus (Phthiraptera).

The complete arrangement of genes in the mitochondrial (mt) genome is known for 12 species of insects, and part of the gene arrangement in the mt genome is known for over 300 other species of insects. The arrangement of genes in the mt genome is very conserved in insects studied, since all of the protein-coding and rRNA genes and most of the tRNA genes are arranged in the same way. We sequenced the entire mt genome of the wallaby louse, Heterodoxus macropus, which is 14,670 bp long and has the 37 genes typical of animals and some noncoding regions. The largest noncoding region is 73 bp long (93% A+T), and the second largest is 47 bp long (92% A+T). Both of these noncoding regions seem to be able to form stem-loop structures. The arrangement of genes in the mt genome of this louse is unlike that of any other animal studied. All tRNA genes have moved and/or inverted relative to the ancestral gene arrangement of insects, which is present in the fruit fly Drosophila yakuba. At least nine protein-coding genes (atp6, atp8, cox2, cob, nad1-nad3, nad5, and nad6) have moved; moreover, four of these genes (atp6, atp8, nad1, and nad3) have inverted. The large number of gene rearrangements in the mt genome of H. macropus is unprecedented for an arthropod.

Adenine↗
PubMed2000

Phylogenetic analyses of the rhipicephaline ticks indicate that the genus Rhipicephalus is paraphyletic.

We inferred the phylogeny of 21 species and subspecies of ticks from the subfamilies Rhipicephalinae and Hyalomminae using cytochrome c oxidase subunit I (COI) and 12S rRNA mitochondrial gene sequences. Two members of the subfamily Haemaphysalinae were used for outgroup reference. The largest rhipicephaline genus, Rhipicephalus, was represented by ticks from six of the species groups, the second largest genus, Dermacentor, by species from two of three of its subgenera, and the genus Boophilus by 3 of its 5 species. We analyzed the 12S and COI sequences separately and together; statistically significant incongruence between the 12S rDNA and the COI sequences was not detected in the combined dataset using the incongruence length difference test. The combined dataset provided greater phylogenetic resolution than the individual datasets, and although the 12S rDNA data had only 25% of the parsimony-informative characters, it provided half of the total partitioned Bremer support for the combined dataset. We present the first hypothesis of phylogenetic relationships among some species groups of Rhipicephalus but our most controversial result was that the genus Rhipicephalus is apparently paraphyletic, unless species of Boophilus are included in it. The species of Rhipicephalus most closely related to Boophilus spp. were from the R. pravus and R. evertsi species groups, which may implicate an African origin for this important group of ticks.

Animals↗
PubMed1999

The novel mitochondrial gene arrangement of the cattle tick, Boophilus microplus: fivefold tandem repetition of a coding region.

We sequenced across all of the gene boundaries in the mitochondrial genome of the cattle tick, Boophilus microplus, to determine the arrangement of its genes. The mtDNA of B. microplus has a coding region, composed of tRNA(Glu) and 60 bp of the 3' end of ND1, that is repeated five times. Boophilus microplus is the first coelomate animal known to have more than two copies of a coding sequence. The mitochondrial genome of B. microplus has other unusual features, including (1) reduced T arms in tRNAs, (2) an AT bias in codon use, (3) two control regions that have evolved in concert, (4) three gene rearrangements, and (5) a stem-loop between tRNA(Gln) and tRNA(Phe). The short T arms and small control regions (CRs) of B. microplus and other ticks suggest strong selection for small genomes. Imprecise termination of replication beyond its origin, which can account for the evolution of tandem repeats of coding regions in other mitochondrial genomes, cannot explain the evolution of the fivefold repeated sequence in the mitochondrial genome of B. microplus. Instead, slipped-strand mispairing or recombination are the most plausible explanations for the evolution of these tandem repeats.

Amino Acid Sequence↗
PubMed1996

Contagious ecthyma in the live sheep export industry.

OBJECTIVE: To investigate control options for contagious ecthyma (scabby mouth) in Australian sheep exported live to the Middle East. DESIGN: Prevalence, vaccination and modelling studies. PROCEDURE: One hundred and forty weaner sheep (less than 1 year old) on each of 106 farms in Western Australia (WA) and 18 farm groups of adult wethers received at a WA commercial feedlot were examined for lesions of scabby mouth. Sheep on a total of 26 farms in 3 States were divided into treatment and control groups for the vaccination study. A simple deterministic compartmental model was developed to establish which parameters had the greater effect on disease prevalence. RESULTS: The proportion of farms with evidence of scabby mouth in weaner sheep was 23.6% and, on those farms with the disease, the overall prevalence was 6.1%. At the feedlot, 4 out of 18 farm groups had 5 or more sheep with lesions on arrival. The overall prevalence in the 4 diseased groups was 5.2%. Sheep vaccinated on farm before trucking to the feedlot had a lower prevalence of scabby mouth at the end of simulated shipping than controls. The main determinant of scabby mouth prevalence was the proportion of sheep immune to the disease. CONCLUSION: A program of vaccination for scabby mouth will reduce the prevalence of disease during live export. However, using current technology it is not possible to deliver shipments of sheep to the Middle East that are guaranteed completely free of scabby mouth.

Animals↗
PubMed1995

Outgroup heteroduplex analysis using temperature gradient gel electrophoresis: high resolution, large scale, screening of DNA variation in the mitochondrial control region.

The ability of DNA screening techniques such as Temperature Gradient Gel Electrophoresis (TGGE) and Heteroduplex Analysis to provide resolution approaching that provided by DNA sequencing for a fraction of the time, effort and expense point to them as the logical successor to allozyme electrophoresis for population genetics. Here we present a novel alternative to the standard TGGE/Heteroduplex Analysis protocol - Outgroup Heteroduplex Analysis (OHA). We assess this technique's sensitivity in comparison to previous screening approaches using a known hierarchy of sequence differences. Our data show that Outgroup Heteroduplex Analysis has greatly increased sensitivity for screening DNA variants from that of TGGE used alone and is easily applicable to large numbers of samples. Using this technique we can consistently detect differences of as small as one base change in a 433-base-pair fragment of Control Region mitochondrial DNA from Melomys cervinipes (an Australian rodent). The approach should easily be extendable to nuclear loci and is not necessarily dependent on the use of a denaturing gradient. When combined with a targeted sequencing effort, OHA provides a sensitive and simple means of obtaining allele/haplotype frequencies and their phylogenies for population and phylogeographic studies in molecular ecology.

Animals↗
PubMed1991

Fasciola hepatica: immunoprecipitation analysis of biosynthetically labelled antigens using sera from infected sheep.

The antigenicity of the biosynthetically labelled somatic and excretory/secretory proteins of adult Fasciola hepatica was investigated over 20 weeks of an infection with F. hepatica in sheep. The antibody response was initially detected by ELISA 2 weeks after infection, and was sustained at this level for the remainder of the infection. Immunoprecipitation analysis indicated that a large number of proteins were recognized by the sheep, with several dominant antigens occurring in the 29-31 kilodalton molecular weight range. No differences were found between the antigens recognized by sheep in the early or late stages of infection suggesting that there are similarities between the antigens of the immature and mature forms of the parasite.

Animals↗
PubMed1987

Autoradiographic localization and biochemical characterization of peripheral type CCK receptors in rat CNS using highly selective nonpeptide CCK antagonists.

Two potent and highly selective nonpeptide antagonists, L-365,031 [1-methyl-3-(4-bromobenzoyl)amino-5-phenyl-3H-1,4 benzodiazepin-2-one] and 3H-L-364,718 [1-methyl-3-(2-indoloyl)amino-5-phenyl-3H-1,4 benzodiazepin-2-one] were used to localize "peripheral" CCK receptors in rat brain. In autoradiographic experiments, L-365,031 displaced 125I-Bolton Hunter CCK-8 binding from the interpeduncular nucleus (IPN) (IC50 = 7 X 10(-8) M), the area postrema (AP), and the nucleus tractus solitarius (NTS) without influencing specific binding to other areas, such as the cerebral cortex or the spinal tract of the trigeminal nerve. Desulfated CCK preferentially inhibited 125I-CCK binding to cerebral cortex (IC50 = 7 X 10(-8) M) rather than IPN (IC50 greater than 1 X 10(-6) M) or AP-NTS. In the medulla the localization of 3H-L-364,718 binding was similar to L-365,031-sensitive 125I-CCK-8 binding and was found in the AP and medial, but not lateral, aspects of the NTS. In membranes prepared from IPN, NTS, and AP, 3H-364,718 binding was of high affinity (Kd = 0.14 nM), saturable (Bmax = 20 fmol/mg protein), and inhibited by compounds previously shown to act at pancreatic CCK receptors. The receptors labeled by 3H-364,718 were modulated by guanyl nucleotide, which reduced agonist affinity 10-fold without affecting antagonist binding. The localization and high density of CCK receptors in AP and NTS suggest that these receptors may play an important role in processing sensory afferent information.

Animals↗
PubMed1986

Multiple tachykinin binding sites in peripheral tissues and in brain.

Tachykinin binding sites in guinea pig urinary bladder (GPUB), rat salivary gland (RSG), hamster urinary bladder (HUB), rat vas deferens (RVD) and rat cerebral cortex (RCC) were compared using 125I-Bolton Hunter conjugates of substance P (125I-BHSP), eledoisin (125I-BHE) and neurokinin A (125I-BHNKA). In typical SP-P tissues (GPUB, RSG) and in RCC, SP was the most potent displacer of 125I-BHSP and [Glp6,D-Pro9]-SP(6-11) was 90 times less active than [Glp6,L-Pro9]-SP(6-11) while SP methyl ester (SPOMe) was 5-10 times more active than the Bolton Hunter conjugate of SPOMe (I-BHSPOMe). On the other hand, in typical SP-E tissues (HUB, RVD), neurokinin A was most potent in displacing 125I-BHE and [Glp6,D-Pro9]-SP(6-11) was over 300 times more active than [Glp6,L-Pro9]-SP(6-11) while SPOMe was 160 times less active than I-BHSPOMe. In rat cerebral cortex, the rank order of potency of tachykinins and related analogues in displacing 125I-BHE was distinct from that of peripheral SP-E sites, with neurokinin B being the most potent displacer, and SPOMe was over 1,000 times more active than I-BHSPOMe; 125I-BHE binding sites in CNS may represent a third category of tachykinin receptor, designated SP-N.

Animals↗
PubMed1980

An attempt to vaccinate sheep against Fasciola hepatica using a juvenile fluke antigen sheep antibody complex.

Sheep were injected intramuscularly with a mixture of Freund's complete adjuvant and a precipitated fluke antigen-antibody complex isolated from in vitro cultures of excysted metacercariae of Fasciola hepatica in serum from infected sheep. Control groups of sheep were given Freund's complete adjuvant or were untreated. All sheep were then challenged with 200 metacercariae of F hepatica. Assays of antibody and liver enzymes in serum collected during the experiment indicated that although vaccination with the complex resulted in a pronounced antibody response to its antigenic component(s), there was no apparent effect on the migratory activity of the juvenile flukes in these animals. Failure to confer protection on vaccinated sheep was confirmed at autopsy when no significant difference was found between the worm burden of these animals and the controls.

Animals↗