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B Fenton

Publications and source records attributed to B Fenton.

At least 37 records · Page 2Linked to original sources
PubMed1998

Analysis of clonal diversity of the peach-potato aphid, Myzus persicae (Sulzer), in Scotland, UK and evidence for the existence of a predominant clone.

Clones of the peach-potato aphid, Myzus persicae (Sulzer), mostly from Scotland, UK were examined using an rDNA fingerprinting technique. Eighty patterns (genotypes) were found amongst the 276 clones. A large number of clones (30%) from all sample areas in Scotland exhibited the same simple pattern, suggesting the presence of a single M. persicae clone. There was no difference in genotype distributions between M. persicae collected from brassica or potato crops, suggesting that host-adapted genotypes have no advantage in the field. Different fingerprints were randomly distributed in the environment, although clones taken from the same leaf were more often the same fingerprint. Highly distinctive fingerprints, which were more widely distributed, suggest that this technique could be used to follow individual clones. In addition to the common clonal type, multiple fingerprint bands were found over successive years, implying that, in Scotland, local overwintering asexual populations are the most common source of M. persicae in the following year.

Animals↗
PubMed1998

A study of variation in rDNA ITS regions shows that two haplotypes coexist within a single aphid genome.

We report variation in the rDNA internal transcribed spacers (ITSs) of aphid species, the first for these insects. Variation at 6 sites within ITS1 sequences of the green peach aphid, Myzus persicae, identified two haplotypes coexisting within the same individuals, indicating that molecular drive has not homogenised different copies of rDNA. During this study, we found that PCR can cause a precise 58-bp loss in the amplified copies of an ITS haplotype (type 1). This occurs in all detectable copies under routine PCR conditions, at different annealing temperatures and with Pfu and Taq polymerases. In addition, "hot-start" PCR exclusively copied a different, rare haplotype (type 2). These observations have important considerations for using PCR, as large deletions in PCR products may not reflect real deletions in the genome, and changes in PCR conditions may be needed to copy cryptic haplotypes.

Animals↗
PubMed1997

Analysis of eriophyid mite rDNA internal transcribed spacer sequences reveals variable simple sequence repeats.

Ribosomal DNA internal transcribed spacers of the eriophyid mites Cecidophyopsis ribis, C. selachodon, C. spicata, C. alpina, C. aurea, C. grossulariae and Phylocoptes gracillis were amplified using PCR, cloned and sequenced. Sequences for the ITS1 of Cecidophyopsids were 92-99% homologous. Cecidophyopsis inter-specific differences were found in seventeen simple sequence repeats (vSSRs), fourteen point mutations and two indels. No intra-specific variation in vSSRs was detected. A hypothetical structure for ITS1 was obtained and vSSRs were mapped onto this. Changes in vSSRs were compensated for by changes in complementary vSSRs or through multiple point mutations. A comparison with vSSRs of other arthropods suggested that the levels of intra-specific variation in Cecidophyopsis mites was less than in organisms which do not use arrhentoky for male determination.

Animals↗
PubMed1997

Kinetic characterisation of skin inner-ring deiodinative pathway and its correlation with circulating levels of reverse tri-iodothyronine in developing rainbow trout.

The present study has demonstrated the presence of circulating reverse tri-iodothyronine (rT3) levels and its main generating pathway in rainbow trout. A specific rT3, RIA using thyronine-stripped sera in the standard curve was standardised, allowing precise and accurate quantification of radioimmunoassayable rT3. We also demonstrated that trout skin is an important source of rT3 production. T3 or thyroxine trout skin inner-ring deiodination (IRD) activity was assessed by using rT3 RIA and/or paper chromatography. The kinetic characterisation of this deiodinative pathway disclosed a typical deiodinase type III (DIII) enzyme, except for its conspicuous thermodependency which attained its maximal catalytic efficiency at 15 degrees C. This finding suggested the expression of enzymatic variants, which is a common functional array in teleosts. Both circulating rT3 and DIII activity were present in juvenile and adult individuals and were inversely correlated with age, weight and length. In conclusion, this study demonstrated that (1) skin IRD activity and its product rT3 are present throughout the development of rainbow trout, and (2) trout skin DIII activity attains its higher catalytic efficiency in the physiological range of temperature for this species, thus suggesting the expression of enzymatic variants.

Animals↗
PubMed1995

Species identification of Cecidophyopsis mites (Acari: Eriophyidae) from different Ribes species and countries using molecular genetics.

Cecidophyopsis mites were studied by PCR amplification of parts of their ribosomal DNA, followed by restriction enzyme analysis. Mite specimens on Ribes nigrum (black currant) from six countries gave the same digestion pattern, which was distinct from the pattern for mites found on R. rubrum from Poland and Finland and for R. grossularia from the USA. This suggests that each Ribes species is host to a different mite species: C. ribis, C. selachodon and C. grossulariae, respectively. Two other mite samples from R. alpinum and R. aureum were identical but were distinct from each of the other species.

Animals↗
PubMed1995

Investigative approach to frog gastrocnemius laboratory: potential impact on animal use in teaching laboratories.

With growing concern over the use of animal experimentation in the teaching of physiology, many biology departments are reassessing the use of animal experiments in the teaching lab. However, it may be just as important to assess how animal experimentation is used in the undergraduate teaching laboratory rather than simply assessing if animal experimentation should be used at all. In our study, sophomore-level life science students enrolled in a core organismal biology course undertook a laboratory exercise designed to elucidate properties of muscles and neuromuscular communication following two protocols: 1) a standard demonstrational model wherein students were told to undertake the exercise as a means to understand physiological processes that they had been exposed to previously in lecture or 2) an investigative model wherein the use of the gastrocnemius preparation was a logical next step in an ongoing investigation, the content of which was driven by student-generated hypotheses. We have observed a significant decrease in a number of the negative comments concerning the use of animals in experimentation (25.6 vs. 3.6%) since the implementation of the investigative approach to the laboratory, suggesting that curricular approaches to the use of animals in the teaching laboratory may have an impact on student attitudes concerning animal experimentation.

Animal Welfare↗
PubMed1994

Molecular analysis of ribosomal DNA from the aphid Amphorophora idaei and an associated fungal organism.

The ribosomal DNA cistron from the large raspberry aphid, Amphorophora idaei (Hemiptera: Aphididae), has been mapped by restriction analysis. The results showed that the map of A. idaei was similar to those of the previously characterized aphids Schizaphis graminum and Acyrthosiphon pisum. An extra Bgl II site was found in some of the ribosomal DNA intergenic spacer repeats in A. idaei. Using in-situ hybridization to aphid mitotic chromosomes it was demonstrated that probes derived from this region mapped to the pair of X chromosomes and it was therefore aphid in origin. Polymerase chain reaction using conserved rDNA primers also detected significant amounts of a fungal genome in the DNA samples. Microscopic investigation showed that the external surface of A. idaei harboured fungal propagules, hyphae and yeast-like organisms.

Animals↗
PubMed1994

Ribosomal spacer length variability in the large raspberry aphid, Amphorophora idaei (Aphidinae: macrosiphini).

The large raspberry aphid, Amphorophora idaei, has several biotypes described by their abilities to overcome plant resistance genes. Bioassays of field populations showed a strong shift towards A1 resistance-breaking biotypes since the 1960s. RFLP analysis of the rDNA cistron was used to study variation found within and between standard clones of three A. idaei biotypes and twenty-nine field populations collected over 3 years. Probing genomic DNA with the ribosomal DNA probe pBG 35 produced consistent differences in RFLPs between standard clones of biotypes. However, analysis of field populations gave more complex RFLP patterns that were not biotype-specific, unlike characteristic intergenic spacer (IGS) patterns reported for Schizaphis graminum biotypes. All but one sample collected from separate fields showed considerable genetic diversity within populations, attributed to alate migrations of parthenogenetic females in summer and males in autumn.

Animals↗
PubMed1993

A conserved mitotic kinase active at late anaphase-telophase in syncytial Drosophila embryos.

Mutations in the Drosophila gene polo cause abnormal mitotic and meiotic divisions. This gene encodes a 577-amino-acid protein that has an N-terminal putative kinase domain and a 300-residue C-terminal domain. In budding yeast, a homologous kinase is encoded by CDC5 (ref. 3), a gene required for nuclear division late in the mitotic cycle and during meiosis. Murine homologues have also been described. Here we show that the polo gene product immunoprecipitated from extracts of single Drosophila embryos can phosphorylate casein in vitro, and that the kinase activity peaks cyclically at late anaphase/telophase. This contrasts with the cyclical activity of cyclin B-associated p34cdc2 kinase, which is maximal upon entry into mitosis during the rapid cycles of mitosis in the syncytium.

Anaphase↗
PubMed1993

Environmental medicine: its introduction into a medical school primary care requirement.

One hundred and twelve medical students participating in a required 6-week primary-care rotation completed a pretest of environmental medicine knowledge and attitudes at the start of the rotation and a similar posttest on the last day of the rotation. Control group students were to participate in the usual weekly didactic sessions of the clerkship. Intervention students were given a booklet describing environmental considerations in clinical medicine and introducing them to the concept of risk assessment, three computer-assisted instruction cases, and a problem-based learning (PBL) exercise involving role-play. Because voluntary compliance with evaluation forms was poor during year one, during the second year students in the intervention group were required to return evaluation forms in order to sit for the course final examination. Knowledge and attitudes of both intervention and control groups were compared at baseline and at the end of the rotation. Students in the intervention group also completed process evaluations of the intervention materials. Students in both intervention and control groups increased knowledge gains significantly during the second year of the intervention, while neither group improved during year 1. This may have been due to a 'spill-over' effect among primary-care teachers implementing the intervention. Students ranked both environmental and occupational medicine of least importance in their training compared with eight other aspects of medicine, and this ranking did not improve with intervention. The PBL exercise was well received by the students. Of 28 evaluations, 27 ranked the session in the highest 3 of a 5-part Likert scale for worthwhile content, and 24 would recommend the session to a friend.(ABSTRACT TRUNCATED AT 250 WORDS)

Curriculum↗
PubMed1992

Superimposing two-dimensional gels to study genetic variation in malaria parasites.

Two-dimensional polyacrylamide gel electrophoresis is a valuable tool for studying genetic variation in the human malaria parasite, Plasmodium falciparum. It involves examining the position of protein spots in gel produced from different isolates. Some spots have been seen to vary, while others have had a constant position in all isolates so far examined. These invariant spots provide a reference frame to compare variations in other spots. This paper discusses the usefulness of digital image handling, warping and superimposition in a personal computer environment. Rather than produce a fully automatic interpretation system, we show how the computer may be used as a tool for manipulating gel images, although interpretation of the gels' features remains with the human expert. Autoradiographs are scanned on a desktop scanner, and the images in digital form can be displayed on a monitor attached to a personal computer. The coordinates of the invariant spots on each of several gels are identified by the user. Each of the gels is then warped so that the invariant spots of all the gels coincide as closely as possible. The variable spots are then examined. We have used both affine warping transformations, which match the invariant spots as closely as possible, and thin plate spline transformations, which match them exactly. Colour superimposition proved a useful way of examining the gels.

Animals↗
PubMed1991

Structural and antigenic polymorphism of the 35- to 48-kilodalton merozoite surface antigen (MSA-2) of the malaria parasite Plasmodium falciparum.

Merozoite surface antigen MSA-2 of the human parasite Plasmodium falciparum is being considered for the development of a malaria vaccine. The antigen is polymorphic, and specific monoclonal antibodies differentiate five serological variants of MSA-2 among 25 parasite isolates. The variants are grouped into two major serogroups, A and B. Genes encoding two different variants from serogroup A have been sequenced, and their DNA together with deduced amino acid sequences were compared with sequences encoded by other alleles. The comparison shows that the serological classification reflects differences in DNA sequences and deduced primary structure of MSA-2 variants and serogroups. Thus, the overall homologies of DNA and amino acid sequences are over 95% among variants in the same serogroup. In contrast, similarities between the group A variants and a group B variant are only 70 and 64% for DNA and amino acid sequences, respectively. We propose that the MSA-2 protein is encoded by two highly divergent groups of alleles, with limited additional polymorphism displayed within each group.

Amino Acid Sequence↗
PubMed1990

Genetic analysis of polymorphic proteins of the human malaria parasite Plasmodium falciparum.

Five polymorphic proteins, detected by two-dimensional electrophoresis, were analysed in the parents and progeny of a cross between two clones of the malaria parasite Plasmodium falciparum. The information obtained showed that different forms of each protein were determined by allelic variants of each respective gene. One protein was identified as the parasite enzyme adenosine deaminase. Recombinant parasites were produced at a higher than expected frequency.

Adenosine Deaminase↗
PubMed1990

Genetic diversity of Plasmodium falciparum shows geographical variation.

Sixty Plasmodium falciparum isolates, 20 each from Thailand, Zimbabwe, and Brazil, were characterized for 20 variant genetic markers, including the enzymes glucose phosphate isomerase, adenosine deaminase and peptidase, 11 other proteins detected by 2-dimensional electrophoresis (2D-PAGE), 2 merozoite surface antigens (MSA-1 and MSA-2), one exported antigen (Exp-1), and sensitivity to the drugs chloroquine, pyrimethamine, and mefloquine. The study examines the extent of diversity between individual isolates and the differences in the frequency of certain variants of the markers between the 3 countries. The principal conclusions to be drawn from the study are that there is extensive polymorphism in many of the genetically determined characters of this parasite, multiple infections with greater than 1 genetically distinct parasite are common, and there are geographical variations in the frequencies with which variant forms of certain markers occur.

Alleles↗
PubMed1989

Plasmodium falciparum: an abundant stage-specific protein expressed during early gametocyte development.

A stage-specific protein has been identified in gametocytes of Plasmodium falciparum. The protein is represented on two-dimensional electrophoresis by peptides of two apparent Mr of 27,000 and 25,000, each of which has at least four different isoelectric points between pH 6.0 and 5.0. The protein is designated Pfg 27/25 (P. falciparum gametocyte-specific antigen of 27 and 25 kDa). By indirect immunofluorescence with a monoclonal antibody 1H12 specific for Pfg 27/25, this protein is present in gametocytes within 30 to 40 hr after invasion of a red blood cell by a merozoite and is present throughout subsequent maturation of the gametocyte; Pfg 27/25 is not detectable on the surface of extracellular gametes by immunofluorescence with Mab 1H12. Pfg 27/25 is absent from asexual stages of P. falciparum at any stage in their development. Pfg 27/25 is an abundant protein in gametocytes and represents between 5 and 10% of total protein of these stages. Pfg 27/25 is also a major immunogen in man during P. falciparum infection. Antibodies to this protein were readily detected in human sera from an area of holoendemic P. falciparum and also from an individual following a primary attack of P. falciparum.

Animals↗
PubMed1989

Polymorphism of a 35-48 kDa Plasmodium falciparum merozoite surface antigen.

Glycoproteins of the asexual blood stages of Plasmodium falciparum were labelled with radioactive glucosamine and analysed by two-dimensional electrophoresis. Four major glycoproteins were detected in all eight parasite isolates studied. Two of the glycoproteins, designated GP2 and GP4, were invariant among the isolates, while the other two GP1 and GP3 were found to be polymorphic in both their biochemical and antigenic properties. By immunoblotting and immunoprecipitation with specific monoclonal antibodies, the two polymorphic glycoproteins were identified as surface antigens of merozoites.

Animals↗