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Traits related to biomass production were analyzed for the presence of quantitative trait loci (QTLs) in a Populus trichocarpa × P. deltoides F(2) population. A genetic linkage map composed of 841 SSR, AFLP, and RAPD markers and phenotypic data from 310 progeny were used to identify genomic regions harboring biomass QTLs. Twelve intervals were identified, of which BM-1, BM-2, and BM-7 were identified in all three years for both height and diameter. One putative QTL, BM-7, and one suggestive QTL exhibited significant evidence of over-dominance in all three years for both traits. Conversely, QTLs BM-4 and BM-6 exhibited evidence of under-dominance in both environments for height and diameter. Seven of the nine QTLs were successfully anchored, and QTL peak positions were estimated for each one on the P. trichocarpa genome assembly using flanking SSR markers with known physical positions. Of the 3,031 genes located in genome-anchored QTL intervals, 1,892 had PFAM annotations. Of these, 1,313, representing 255 unique annotations, had at least one duplicate copy in a QTL interval identified on a separate scaffold. This observation suggests that some QTLs identified in this study may have shared the same ancestral sequence prior to the salicoid genome duplication in Populus.

The genus Populus consists of dioecious woody species with largely unknown genetic mechanisms for gender determination. We have discovered genetic and genomic features in the peritelomeric region of chromosome XIX that suggest this region of the Populus genome is in the process of developing characteristics of a sex chromosome. We have identified a gender-associated locus that consistently maps to this region. Furthermore, comparison of genetic maps across multiple Populus families reveals consistently distorted segregation within this region. We have intensively characterized this region using an F(1) interspecific cross involving the female genotype that was used for genome sequencing. This region shows suppressed recombination and high divergence between the alternate haplotypes, as revealed by dense map-based genome assembly using microsatellite markers. The suppressed recombination, distorted segregation, and haplotype divergence were observed only for the maternal parent in this cross. Furthermore, the progeny of this cross showed a strongly male-biased sex ratio, in agreement with Haldane's rule that postulates that the heterogametic sex is more likely to be absent, rare, or sterile in interspecific crosses. Together, these results support the role of chromosome XIX in sex determination and suggest that sex determination in Populus occurs through a ZW system in which the female is the heterogametic gender.

Elucidation of the mechanisms of dehydration tolerance in poplar (Populus sp.) trees will permit development of biochemical and molecular indicators to identify dehydration-tolerant genotypes during genetic selection. The objectives of this study were to characterize the degree of phenotypic variation in osmotic potential (a determinant of dehydration tolerance), determine the relationship between osmotic potential at full turgor and relative growth rate, and identify quantitative trait loci (QTL) for osmotic potential in an advanced-generation, interspecific poplar pedigree established in contrasting environments. A three-generation, sib-mated black cottonwood (Populus trichocarpa Torr. & Gray) and eastern cottonwood (P. deltoides Bartr.) segregating F(2) family (Family 331) was analyzed at a dry site east of the Cascade Mountain Range (Boardman, OR) and at a wet site west of the mountains (Clatskanie, OR). At the Boardman site, 2-year-old trees (59 clones) were either irrigated everyday (wet) or every other day (dry), whereas 3- and 4-year-old trees (58 clones) at the Clatskanie site were unirrigated. At the Boardman site, the typically narrow range of osmotic potentials exhibited by grandparents and parents was greatly expanded in the F(2) population, spanning from -1.38 to -2.35 MPa under wet conditions, with a similar range under dry conditions (-1.40 to -2.15 MPa). Clones that had osmotic potentials < or = -1.90 MPa generally displayed full maintenance of stem relative growth rates under dry conditions in contrast to clones with osmotic potentials that were < or = -1.60 MPa, in which stem relative growth rates were reduced by an average of 38% in the dry treatment relative to the wet treatment. Although osmotic adjustments of 0.13 to 0.36 MPa were observed in nine out of 59 clones, adjustment typically occurred from relatively high baseline osmotic potentials. The range in osmotic potential at the wetter Clatskanie site at age three was higher (-1.27 to -1.84 MPa) and was further expanded the following year (-1.14 to -1.94 MPa), which had a wetter spring than the previous year, followed by a typically dry July. Seven QTL for osmotic potential were identified that each explained > 7.5% of the variation in osmotic potential. Given that four clones (7%) had osmotic potentials of -2.00 MPa or less and that QTL for osmotic potential have been identified, we suggest that there are opportunities to extend the limit of dehydration tolerance in Populus.

A long-term series of experiments to map QTL influencing wood property traits in loblolly pine has been completed. These experiments were designed to identify and subsequently verify QTL in multiple genetic backgrounds, environments, and growing seasons. Verification of QTL is necessary to substantiate a biological basis for observed marker-trait associations, to provide precise estimates of the magnitude of QTL effects, and to predict QTL expression at a given age or in a particular environment. Verification was based on the repeated detection of QTL among populations, as well as among multiple growing seasons for each population. Temporal stability of QTL was moderate, with approximately half being detected in multiple seasons. Fewer QTL were common to different populations, but the results are nonetheless encouraging for restricted applications of marker-assisted selection. QTL from larger populations accounted for less phenotypic variation than QTL detected in smaller populations, emphasizing the need for experiments employing much larger families. Additionally, 18 candidate genes related to lignin biosynthesis and cell wall structure were mapped genetically. Several candidate genes colocated with wood property QTL; however, these relationships must be verified in future experiments.

Chemical wood property traits were analyzed for the presence of quantitative trait loci (QTLs) in a three-generation outbred pedigree of loblolly pine ( Pinus taeda L.). These traits were assayed using pyrolysis molecular beam mass spectrometry and include mass spectrum peak intensities associated with carbohydrates, alpha-cellulose and hemicellulose sugars, and lignin. Models for projection to latent structures (PLS) were used to also estimate the chemical composition of cell walls (i.e., alpha-cellulose, galactan and lignin) from mass spectrum data using multivariate regression. Both earlywood and latewood fractions from the fifth annual ring were analyzed for each trait. An interval mapping approach designed for an outbred pedigree was used to estimate the number of QTLs, the magnitude of QTL effects, and their genomic position. Eight unique QTLs influencing cell wall chemistry were detected from multiple peak intensities and/or PLS estimates using the one- and two-QTL models. Significant differences in chemical contents were observed among the populations from North Carolina vs Oklahoma, and results from QTLxenvironment analyses suggest that QTLs interact with environmental location. QTLs should be verified in larger experiments and in different genetic and environmental backgrounds. QTL mapping will help towards eventually identifying genes having a major effect on chemical wood properties.

Anchored reference loci provide a framework for comparative mapping. They are landmarks to denote conserved chromosomal segments, allowing the synthesis of genetic maps from multiple sources. We evaluated 90 expressed sequence tag polymorphisms (ESTPs) from loblolly pine (Pinus taeda L.) for this function. Primer sets were assayed for amplification and polymorphism in six pedigrees, representing two subgenera of Pinus and a distant member of the Pinaceae, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). On average, 89% of primer sets amplified in four species of subgenus Pinus, 49% in one species of subgenus Strobus, and 22% in Douglas-fir. Polymorphisms were detected for 37-61% of the ESTPs within each pedigree. Comparative mapping in loblolly and slash pine (P. elliottii Englm.) revealed that ESTPs mapped to the same location. Disrupted synteny or significant disruptions in colinearity were not detected. Thirty-five ESTPs met criteria established for anchor loci. The majority of those that did not meet these criteria were excluded when map location was known in only a single species. Anchor loci provide a unifying tool for the community, facilitating the creation of a "generic" pine map and serving as a foundation for studies on genome organization and evolution.

The effect of dose and duration of immunizing infections of Heligmosomoides polygyrus on protection against homologous challenge was studied in female TO mice. Primary infections were terminated at various levels with pyrantel embonate (adult infections) or ivermectin (larval infections) and mice were then challenged with 500 infective larvae (L3). The level of protection to secondary challenge positively correlated with the intensity of the primary immunizing infection but truncation of larval infection produced significantly better protection than termination of the adult nematode infection. The duration of the primary larval infection (1-6 days) positively correlated with the level of protection to secondary challenge, antibody responses and the proportion of circulating eosinophils. Histological changes in the gastrointestinal tract, peripheral leucocytic changes and antibody responses of the mice to H. polygyrus adult somatic antigens indicate both a cellular and humoral basis of host immunity to secondary challenge. Although the TO mice are slow responders in that they harbour chronic infections, immunization by intramucosal killing of the larval stage produced strong protection against secondary challenge infection. The presence of dead immunogenic larval stages within the intestinal wall may well be an important factor, since it exposes the host to stage specific antigens at an appropriate location. The implications of the findings for the control of gastrointestinal nematode infections are also discussed.

Concurrent African trypanosome and gastrointestinal helminth infections are prevalent in sub-humid savannah where they are endemic. However, acquired resistance in animals varies with their responder status and exposure. As a guide to study in the definitive hosts, the effects of Trypanosoma congolense infection on the development and maintenance of homologous Heligmosomoides polygyrus resistance were investigated in outbred TO mice. These mice were immunised by abbreviation of larval infection. Immune or naive mice were either infected with 500 infective larvae (L3) of H. polygyrus and/or 10(4) bloodstream forms of T. congolense or were not infected. The outcome of infection was monitored by routine parasitological and immunological techniques for 30 days after the day of the T. congolense infection. Significantly more immune mice concurrently infected with both parasites survived than did immune mice in which H. polygyrus was superimposed on a 10-day-old T. congolense infection. Although all the mice in this latter group died before the end of the experiment, larval immunisation prolonged their survival, relative to similarly treated naive mice. The antibody titres to H. polygyrus in the sera of immune mice challenged with H. polygyrus alone were significantly higher than those of immune mice concurrently infected with both parasites but the levels of protection obtained were comparable. It is concluded that T. congolense may not completely block the strong acquired resistance induced by abbreviated H. polygyrus larval infection in TO mice but is capable of interfering with protective responses, especially if the trypanosome infection occurs prior to H. polygyrus challenge infection.

Genetic linkage maps were constructed for loblolly pine (Pinus taeda L.) and radiata pine (P. radiata D. Don) using a common set of RFLP and microsatellite markers. The map for loblolly pine combined data from two full-sib families and consisted of 20 linkage groups covering 1281 cM. The map for radiata pine had 14 linkage groups and covered 1223 cM. All of the RFLP probes readily hybridise between loblolly and radiata pine often producing similar hybridisation patterns. There were in total 60 homologous RFLP loci mapped in both species which could be used for comparative purposes. A set of 20 microsatellite markers derived from radiata pine were also assayed; however, only 9 amplified and revealed polymorphic loci in both species. Single-locus RFLP and microsatellite markers were used to match up linkage groups and compare order between species. Twelve syntenic groups were obtained each consisting of from 3 to 9 homologous loci. The order of homologous loci was colinear in most cases, suggesting no major chromosomal rearrangements in the evolution of these species. Comparative mapping between loblolly and radiata pine should facilitate genetic research in both species and provide a framework for mapping in other pine species.

A consensus map for loblolly pine (Pinus taeda L.) was constructed from the integration of linkage data from two unrelated three-generation outbred pedigrees. The progeny segregation data from restriction fragment length polymorphism, random amplified polymorphic DNA, and isozyme genetic markers from each pedigree were recoded to reflect the two independent populations of parental meioses, and genetic maps were constructed to represent each parent. The rate of meiotic recombination was significantly greater for males than females, as was the average estimate of genome length for males (1983.7 cM [Kosambi mapping function (K)]) and females [1339.5 cM(K)]. The integration of individual maps allows for the synthesis of genetic information from independent sources onto a single consensus map and facilitates the consolidation of linkage groups to represent the chromosomes n = 12 of loblolly pine. The resulting consensus map consists of 357 unique molecular markers and covers approximately 1300 cM(K).

The effects of concurrent Heligmosomoides polygyrus and Trypanosoma congolense infection on the expression of acquired resistance to homologous nematode challenge were studied in female outbred TO mice. Mice were infected with 500 infective larvae (L3) of H. polygyrus and the infection was terminated by anthelminthic treatment on Day 12, when the worms were adults. Eight days later sub-groups of these pre-exposed mice, and of similar mice which had not experienced the previous infection with H. polygyrus, were either simultaneously infected with 500 L3 of H. polygyrus and 10(4) bloodstream forms of T. congolense, or with only one of these parasites, or were not infected. The experiment was monitored by routine parasitological and immunological techniques, including quantitative assessment of worm burden, trypanosome parasitaemia, growth of nematodes and measurement of the parameters reflecting pathological and antibody responses for 30 days after immunization. Concurrent H. polygyrus and T. congolense infection resulted in abrogation of the partial immunity against challenge infection with H. polygyrus in the pre-exposed mice, and in depressed humoral antibody responses following infection. Mortality was greatly reduced in pre-exposed mice infected with T. congolense alone compared to naive mice. The growth of male H. polygyrus worms was not affected by either the immune or infection status of their host. Although the increased size of the female worms from pre-exposed and then concurrently infected mice compared to similar mice infected only with H. polygyrus was significant, the egg production per worm was not affected.

Restriction site variation in chloroplast DNA (cpDNA) was surveyed to analyze population dynamics in Liriodendron tulipifera L., a woody angiosperm found in eastern North America. Two cpDNA haplotypes, differing by the presence or absence of five restriction site changes (nucleotide sequence divergence estimated as approximately 0.15%) are geographically structured; 61 widespread populations possess the "northern" haplotype and three isolated populations of central Florida possess the "southern" haplotype. This geographic break in cpDNA distribution corresponds to patterns of geographic distribution revealed by a previous survey of allozyme variation, with the exception that analyses of allozyme data further divided the populations containing the northern cpDNA haplotype into two groups, a widespread upland group and a coastal intermediate group. Analyses of these two independent data sets together support the hypothesis that L. tulipifera survived the glacial advances of the Pleistocene in two distinct refugia, possibly as different taxa, and the intermediate coastal group was putatively formed from recent hybridizations between these entities., (© 1996 The Society for the Study of Evolution.)

The research work relating to helminths, which has been conducted within the Helminthology Section of the CTVM, often in collaboration with colleagues from the tropics is reviewed and placed into a historical perspective. The research has, in the main, concentrated on the trematodes Fasciola hepatica and Fasciola gigantica and the cestodes Taenia saginata and Taenia solium, but work on other parasites including gastro-intestinal nematodes is also considered. All of these parasites are of obvious veterinary/economic importance particularly in the tropics and subtropics. While the zoonotic importance of T. saginata and T. solium has been recognised for many years, it is only more recently that the zoonotic impact of Fasciola spp. has been generally acknowledged.

A murine model using Heligmosomoides polygyrus and Trypanosoma congolense has been developed for studying the effects of concurrent chronic gastrointestinal nematode and trypanosome infections. Female outbred mice were infected either with 500 infective larvae (L3) of H. polygyrus or with 10(4) bloodstream forms of T. congolense or both. In concurrent infections, animals were dosed with both parasites simultaneously or the trypanosomes were injected 5 or 10 days after the mice were infected with the nematode. The course of infection was monitored by routine parasitological and immunological techniques for 30 days after the H. polygyrus infection. Concurrently infected mice were severely compromised, except when T. congolense was superimposed on a 10-day-old (adult) H. polygyrus infection. In H. polygyrus-infected mice, simultaneous or subsequent infection with trypanosomes did not markedly influence worm establishment or fecundity, but the female worms were slightly stunted. Surviving mice displayed a markedly reduced antibody response to H. polygyrus antigens and a slightly reduced antibody response to T. congolense antigens.

Following the routine use of tiabendazole at monthly intervals for several years, the trichostrongyle parasites of sheep and goats on a government research station in North-West Cameroon had become resistant to benzimidazole anthelmintics.

Taenia saginata cyst fluid proteins from 4, 8, 12 and 16-week-old cysticerci were analysed by a combination of direct 125I radio-isotope labelling, immunoprecipitation using a panel of sera from infected cattle infected with T. saginata and SDS-PAGE. Protein antigens of 12, 14, 16, 20 and 26 kDa were identified in all of the cyst fluids examined. These were immunogenic and were precipitated by serum taken from cattle from 8 weeks after infection onwards and were therefore considered to be of diagnostic potential. A 185 kDa protein antigen found only in the cyst fluid of 4-week-old cysticerci and a 43 kDa protein antigen first detected in cyst fluid from 8-week-old cysticerci were also identified but were considered to be of more limited diagnostic potential due to their restricted presence. An apparently non-immunogenic 67 kDa protein, found in all the cyst fluids examined, may have been host serum albumin.

Previously described techniques for hatching eggs of Taenia taeniaeformis were found to give inconsistent and generally ineffective results, even the degree of disaggregation of the embryophore varying with the strain of parasite. Furthermore, the hatched and activated oncospheres did not survive in the hatching fluid. Following a series of studies on the composition of the hatching fluids, a more reliable procedure was developed. Pretreatment with hypochlorite, at 0.67% w/w available chlorine, caused disaggregation of the embryophoral blocks of virtually all the eggs. When this was followed by exposure to a solution containing 10 mg.ml-1 trypsin, 10% ox bile and 10% heat-inactivated foetal calf serum in modified RPMI with HEPES buffer and L-glutamine, about 50% of the viable oncospheres were activated and escaped from the oncospheral membrane. Most of the activated oncospheres survived in this hatching fluid for at least three hours.

A survey showed that in the North West Province of Cameroon 92% of the farmers rear goats as against only 21% who rear sheep. The main constraint on sheep husbandry appeared to be a traditional belief that keeping sheep adversely affects a woman's fertility. Flock sizes are small (three to 48, median seven) but there was some tendency towards larger numbers in mixed flocks. There were considerably more females than males. Six systems for managing small ruminants were identified. The most widely practised was housing at night and tethering in daytime during the cropping season with either tethering or free-range grazing during the daytime in the non-cropping season. The most common housing system was an enclosed shed with walls of sticks, tree fern or bamboo. Floors of planks laid on the earth or slightly raised were used by about 48% of the farmers while 22% constructed raised slatted floors. Most farmers gave their animals salt on a more or less regular basis but otherwise intentional feed supplementation was rare. About 43% of the farmers thought it unnecessary to provide water. Breeding was generally uncontrolled and the progeny of the most active breeding ram or buck was often the main source of replacement males. The overall offtake rates were 20% for sheep and 24% for goats. Several flocks had no offtake while four (three flocks of goats and one of sheep) reported offtake rates of 65 to 80%.

The susceptibility of naive cattle to infection with cysticerci of Taenia crocutae was tested using three six- to nine-month-old Ayrshire bull calves, previously unexposed to infection with taeniid eggs. One calf was given 10,000 T crocutae eggs orally, another 5000 hatched unactivated oncospheres orally and the third 5000 hatched and activated oncospheres by intravenous injection. None of the calves contained viable cysticerci at post mortem examination 15 to 17 weeks later. All three calves contained small numbers of lesions in the liver and lesions were also present in the lungs of the calf which received oncospheres intravenously. All the calves developed an antibody response which was most pronounced in the calf given hatched unactivated oncospheres orally.

Two groups of calves aged 10 to 15 weeks were orally infected with either 6000 or 30,000 Taenia saginata eggs. Three to four months later they were treated with praziquantel, three doses of 50 mg kg-1 on three consecutive days. All the cysticerci were killed by the drug and most were absorbed by between six and nine months after treatment. From then on there was little further absorption and residual calcified cysts were still found in the carcases up to 24 months after drug treatment. These residual calcified cysts were particularly common in the heart muscles and would probably have been detected at meat inspection.

The antibody response of the appropriate hosts (cattle) to Taenia saginata larvae was compared with that of an inappropriate host (Balb/c mice) using gel electrophoresis followed by immunoelectrotransfer blot techniques (Western blotting). Three groups of cattle were included, those known to be resistant to challenge infection because of repeated oral challenge with T. saginata eggs over a 1-year period, a previously infected but known susceptible group and a group of uninfected controls. Serum from the mice and the two groups of infected cattle contained antibodies recognizing different 'target' antigens, some of which may be related to host resistance. The potential value of the technique of Western blotting in dissecting the humoral response of a particular host species to parasitic infection and in the identification of those antigens suitable for the production of effective vaccines is discussed.

The parasites which occurred most frequently in 175 owned or stray dogs in Sabah were Ancylostoma spp. present in 68% of the animals. Dirofilaria immitis occurred in 70% of the adult dogs but neither D. immitis nor Spirocerca lupi were present in puppies under four months of age. The latter attained a prevalence of 30% in the adults. In contrast Toxocara canis occurred in 81% of the puppies but infrequently in older dogs. Dipylidium caninum was moderately prevalent (15 to 25%) in dogs of all ages. Ticks were the most common arthropod parasite being present on 26% of the dogs and were mainly Rhipicephalus sanguineus. Demodectic and sarcoptic mange were confirmed and fleas and lice were also recovered.

Infection of Suffolk lambs with Dictyocaulus filaria larvae beginning at two months of age with one larva per day, six days per week, and doubling every four weeks to reach a final infection rate of 64 larvae per day gave rise to a pattern of larval excretion in the faeces which approximated to that seen in naturally infected Suffolk lambs in Midlothian in 1974. Several of the lambs were still infected with adult D filaria and were excreting larvae in their faeces 28 weeks after the infection began. However, when some of the lambs were challenged at this time, those which had received the previous escalating infection were resistant to the challenge infection.

Whereas one mature or two immature infections with Fasciola hepatica, which had been eliminated by anthelmintic treatment, conferred resistance to reinfection in rats, this did not occur with rabbits. The differences between the hosts were shown by the numbers of flukes which developed following challenge ands by the changes in peripheral eosinophil counts and serum glutamic dehydrogenase levels. In contrast, rabbits gave a stronger serological response (ELISA) than rats but this was not affected by treatment or challenge in either host.

The serological response of 6 calves to experimental oral infection with between 60,000 and 100,000 Taenia saginata eggs at 3-12 months of age was monitored by the enzyme-linked immunosorbent assay (ELISA) and the tanned cell indirect haemagglutination technique (IDH). A serum antibody response was detected by both techniques by 2-3 weeks post infection, rising to a plateau about 4-6 weeks post infection. The serum antibody levels began to decline by about 30 weeks post infection. Two uninfected control cattle gave negative reactions. In addition, the serological response of 5 calves which had received a dose of 10,000 T. saginata eggs at 2-3 days of age and then weekly serial doses of 500 eggs for 12 months thereafter, was compared with a similar group of 5 calves, which had received the single infection of 10,000 eggs at 2-3 days of age only. Calves in both groups developed an antibody response detectable by the ELISA technique whereas those in a group of 5 control calves did not show such a response. When studied individually however there was marked variation in the serum antibody levels of these young cattle, as although some calves gave a relatively strong serological response, others hardly varied from the controls.

An experiment in which groups of calves were repeatedly treated with thiabendazole and compared with similar untreated groups suggested that parasitic gastroenteritis is not a problem in calves kept under traditional management during the wet season on the Jos plateau in northern Nigeria. On the other hand, as the dry season advanced, the effect of earlier treatment during the wet season showed in better weight gains, higher serum albumin concentrations and higher packed cell volumes compared to the controls. The epidemiological significance of this is discussed in relation to the nutritional stresses of the dry season.

Following intramuscular inoculation of Taenia saginata eggs hatched in vitro, 1-month-old calves were capable of developing a complete immunity to the establishment of a living infection by oral challenge. Cysticerci developed at the injection sites and produced an effective immunity whether the hatched oncospheres were activated in vitro or not. A few living cysticerci found at sites other than the inoculation sites were derived from the inoculation dose and parasite migration from the inoculation sites was also observed in control calves which had not been orally challenged. Such migration was much less frequent in adult cattle. Adult cattle which had been orally infected many times were resistant to infection by intramuscular inoculation. Disseminated infections developed in young calves infected by the intravenous and intraperitoneal routes with hatched eggs. The ELISA test was found to be more sensitive at detecting serological antibodies in infected calves than the IHA test.

Three groups of calves aged 6 months were completely protected against oral challenge with Taenia saginata eggs following immunisation by three different methods. These were hyperimmunisation with six serial inoculations of a homogenate of T. saginata strobila in Freund's complete adjuvant, a single intramuscular inoculation with hatched T. saginata eggs or a single oral dose of unhatched T. saginata eggs. The calves immunised with tapeworm homogenate developed the strongest haemagglutinating and precipitating antibody response to the complex of antigens in an extract of tapeworm strobila, cysticercus tissue or cysticercus fluid. The orally infected calves developed a moderate antibody response to these antigens but the calves inoculated with hatched eggs showed only a very weak antibody response. The calves infected orally with eggs developed a peripheral eosinophilia but the other two methods of immunisation did not evoke this response. After challenge infection all groups showed an increase in peripheral eosinophil counts except the group immunised with tapeworm homogenate.

Forty-four Taenia saginata and seven T. solium specimens were collected in Nigeria. Extracts of these worms and of their metacestodes were compared by enzyme electrophoresis. The mobility of glucose phosphate isomerase was consistently faster with T. saginata than with T. solium. Extracts of the strobilate and cysticercus forms of the same species gave identical results. It was thus possible to distinguish clearly between material of either species.

An experiment was conducted to determine the pre- and posttest performance of subjects on a signal-detection task for the following three experimental conditions: sensory isolation, sensory alertness, and sensory relaxation. All subjects were assessed on 36 pretest and 36 posttest trials. Each block of 36 trials consisted of 12 "strong signals," 12 "weak signals," and 12 "no signals." Exposure durations for each experimental condition lasted for one hour. Analyses showed significant improvements in hits from the pretest trials to the posttest trials on the "strong" and "weak signals" for the sensory isolation condition. Moreover, on the posttest "weak signal" trials, subjects in the sensory isolation condition scored a significantly greater number of hits than did those in the sensory alertness or sensory relaxation conditions. It was concluded that sensory isolation produces perceptual enhancement, as measured by a signal-detection task.

Excretory-secretory and somatic preparations of Taenia taeniaeformis contained shared immunologically-active components although immunoelectrophoresis indicated that the major antigen present in the excretory-secretory preparation was only a minor component of the somatic preparation. Both antigens gave similar immunoelectrophoretic reactions with sera from mice infected with either T. taeniaeformis or Taenia crassiceps, but there was evidence from the results using the ELISA technique that the excretory-secretory components showed more species specificity than those of somatic origin.

Strains of Taenia taeniaeformis were shown to possess markedly differing infectivities for Sprague-Dawley rats and CFI mice. Strains from Scotland, Belgium and Iraq were more infective for mice than rats while this situation was reversed with a Malaysian strain. There were also differences in their ability to infect hosts of different ages within the range 3-12 weeks of age.

The excretion of Dictyocaulus filaria larvae in the faeces of Blackface sheep on a heavily stocked lowland farm in south east Scotland, showed considerable individual, week to week and year to year variation. Patent infections were first observed in lambs in May or June but the heaviest and most prevalent infections occurred in the autumn. Infection levels were generally low but infections tended to be prolonged and reinfection occurred following anthelmintic treatment until the late autumn or winter. Only a few very light, short-lived, patent infections were observed in yearlings or adult ewes. Pasture sampling and the use of tracer animals showed that the numbers of infective larvae on the pasture were minimal during the summer months but reached a low peak in the autumn.

The serum antibody levels to Taenia saginata of three groups of cattle were assessed by an enzyme-linked immunosorbent assay (ELISA). The first group of cattle were from four farms which had a confirmed T saginata cysticercosis outbreak, all of which had cattle classed as infected by ELISA. The second group were from four farms where sewage sludge had been applied to pasture subsequently grazed by the cattle. One of these farms had cattle classed as infected by ELISA. The control cattle, which were all classed as uninfected by ELISA, came from five farms whose pasture had not been treated with sewage sludge. In a wider survey, involving sera from 47 additional farms, the majority could not be distinguished from the control farms in the earlier survey. However, samples from three of the farms had a similar number of positives to two of the known infected farms in the initial survey. Since the ELISA assay may indicate infected herds, farms such as these warrant further investigation.

Hydatid cysts of bovine, equine, porcine, ovine, caprine and human origin and also from gerbils used to passage cysts of human origin were obtained from various geographical locations. Extracts from these cysts were compared for the electrophoretic forms of glucose phosphate isomerase. Equine and porcine cyst extracts had identical zymogram patterns. These differed markedly from the zymogram patterns of cysts of ovine, caprine and human origin which appeared identical to the ovine strain. In contrast both types of zymogram patterns were found in extracts from cysts obtained from cattle. This variation seemed to be associated with both geographical location and the fertility of the cysts.

Resistance to Fasciola hepatica could be elicited in rats by implanting mature flukes subcutaneously or intraperitoneally in diffusion chambers. A similar resistance occurred even when the implants were removed two weeks before challenge. This excluded the possibility that the continuing presence of the sensitising flukes was necessary for the maintenance of resistance and also showed that the resistance could be elicited by only two weeks exposure to diffusible immunogens emanating from the flukes.