Hugh L. Fletcher

Stage-specific differences in fecundity over the life-cycle of two characterized isolates of the liver fluke, Fasciola hepatica.

The variability inherent in different isolates of Fasciola hepatica has been evident from reports in the literature but to date there has been no systematic examination of the relationship between these differences and the fecundity of the parasite. In this study we have attempted to remedy this situation by comparing the relative efficiencies with which 2 well-characterized isolates of the liver fluke (Oberon and Fairhurst) progress through both their definitive and intermediate hosts. We did not observe a reduction in fitness in the Oberon isolate which has been reported to be triclabendazole-resistant, compared to the triclabendazole-susceptible Fairhurst isolate, but considerable inter- and intra-isolate variability at different life-cycle stages was recorded. Thus the Oberon isolate gave 4-fold the number of cercariae when 100 snails were each challenged with a single miracidium and was more successful in establishing productive infections in rats. Fairhurst metacercariae excysted at a higher rate than those from the Oberon isolate and Fairhurst flukes produced 4-fold more eggs. The extent of the intra- and inter-isolate variability revealed in this work will provide a basis for the development of models of population dynamics aimed at predicting the response of the liver fluke to changing environmental conditions such as the use of anthelmintics or climatic change.

HIGH INCIDENCE OF CRYPTIC REPEATED ELEMENTS IN MICROSATELLITE FLANKING REGIONS OF GALATHEID GENOMES AND ITS PRACTICAL IMPLICATIONS FOR MOLECULAR MARKER DEVELOPMENT

Abstract During the development of PCR primer sets for microsatellite marker loci from enriched genomic libraries for three squat lobster species from Galatheidae (Decapoda: Anomura); Munida rugosa (Fabricius, 1775), M. sarsi (Huus, 1935), and Galathea strigosa (Linnaeus, 1761) (collectively known as squat lobsters), a number of unforeseen problems were encountered. These included PCR amplification failure, lack of amplification consistency, and the amplification of multiple fragments. Careful examination of microsatellite containing sequences revealed the existence of cryptic repeated elements on presumed unique flanking regions. BLAST analysis of these and other VNTR containing sequences (N  =  252) indicates that these cryptic elements can be grouped into families based upon sequence similarities. The unique features characterising these families suggest that different molecular mechanisms are involved. Of particular relevance is the association of microsatellites with mobile elements. This is the first reported observation of this phenomenon in crustaceans, and it also helps to explain why microsatellite primer development in galatheids has been relatively unsuccessful to date. We suggest a number of steps that can be used to identify similar problems in microsatellite marker development for other species, and also alternative approaches for both marker development and for the study of molecular evolution of species characterised by complex genome organisation. More specifically, we argue that new generation sequencing methodologies, which capitalise on parallel and multiplexed sequencing may pave the way forward for future crustacean research.

Reduction in attainment with increasing student numbers in a university first-level genetics class

The marks for a first year university genetics course for the period 1988/9 to 1995/6 have been analysed. This period was substantially free from changes in course content or assessment, but there was an increase in class size, from 68 to 151 students. The mean final mark fell by approximately 17 per cent (when effects of assessment changes are removed). The largest reductions in marks coincided with greatest increases in numbers of students. The absolute numbers of high attainment students was unchanged. Most students who attempted resit examinations then passed and, ultimately, obtained honours degrees. The evidence suggests that, whilst modification of teaching methods could help alleviate the problem, the increased numbers of students contained a proportion of less able students, who may have benefited from alternative courses.

The radial positions of metaphase chromosomes may be a consequence of the relative strength of their interaction with the spindle and their size

Microtubule orientated forces acting on chromosomes on spindles in mitosis and meiosis will produce a radial component of force in the plane of the metaphase plate. The strength of this vector will depend on the angle at which the microtubule meets the plate. Radial forces will tend to segregate chromosomes to peripheral or central positions, depending on their size, and also on the strength of the activity of individual centromeres. In prometaphase, forces pushing chromosomes from the poles will tend to force them to the periphery of the metaphase plate, as seen in radial metaphases. Tension towards the poles at late metaphase will pull smaller chromosomes and those with more powerfully active kinetochores towards the centre of the plate. If the two genomes in a hybrid cell have different centromeric activities, their chromosomes will be segregated. Microtubule assembly and disassembly, and motor proteins such as the kinesins and dynein which haul organelles along microtubules, can provide forces in both directions.

Intracellular antigenic changes associated with meiosis in the orthopteran Stauroderus scalaris

Monoclonal antibodies have been prepared against purified pachytene cells from grasshopper testes. Immunoblotting and immunofluorescence analyses identified those monoclonal antibodies which showed specificity for antigens in pachytene cells. Several antigenic changes were found to be associated with meiotic cells. Five monoclonal antibodies detected antigens which were located in the cytoplasm of premeiotic cells but were nuclear during meiosis. One monoclonal antibody showed a discrete cytoplasmic fluorescent pattern in meiotic, but not in premeiotic, cells. Another bound specifically to the nuclei of some epithelial cells at the base of follicles in mature testes.

How Homo became Sapiens — On the Evolution of Thinking

Peter Gärdenfors Oxford University Press ISBN: 0198528515 £17.99 250pp Reviewed by Hugh Fletcher Snakes The Natural History Museum Peter Stafford ISBN: 0565091492 £9.95 112pp Reviewed by Sue Howarth Medical Biochemistry: A core text with self-assessment Alexander Brownie and John Kernohan Elsevier, Churchill, Livingstone Second Edition, 2005 ISBN: 0443100152 £16.99 319pp Reviewed by Myles Ripley Ecology: From Individuals to Ecosystems Michael Begon, Colin R Townsend and John L Harper Blackwell Publishing UK Fourth Edition 2006 ISBN: 1405111178 £37.50 738pp Reviewed by Jean Wilson MBE Lapland — A Natural History Derek Ratcliffe A&C Black Publishers ISBN: 0713665297 £38.00 320pp Reviewed by Michael Reiss Medical Bacteriology — A Practical Approach (second edition) Peter Hawkey and Diedre Lewis (eds) Oxford University Press, 2005 ISBN: 0199637784 £40 436pp Reviewed by Richard O Jenkins The Neurobiology of Pain Stephen Hunt and Martin Koltzenburg (Eds) Oxford University Press ISBN: 0198515618 £60.00 403pp Reviewed by Kevin Coward Health & Disease — Presentation Media (Version 2) BIOZONE Learning Media (UK) Ltd www.biozone.co.uk CD-ROM £99.95 Reviewed by Richard O Jenkins Statistics explained — an introductory guide for life scientists Steve McKillup Cambridge University Press ISBN 0521543169 £19.99 267pp Reviewed by Mark Winterbottom

A cell surface antigen associated with meiosis in male Staurdoderus scalaris (Orthopteran)

Immunofluorescence has identified seven monoclonal antibodies reactive with the surface of meiotic cells and absent in premeiotic cells. Analysis by immunogold electron microscopy indicated that these antigens were present on the external surface of the cells and were coincident with the presence of synaptonemal complexes in the nucleus. On immunoblots a common glycosylated protein of 205 kDa was recognized, in addition to smaller subunits, suggesting the presence of a protein complex comprised of smaller peptides.