Requirement for MHC class II positive accessory cells in an antigen specific bovine T cell response

Purified populations of bovine antigen presenting cells (APCs) and T cells have been isolated from peripheral blood and characterised using various monoclonal antibodies (mAbs) for cell surface markers. Bovine APCs were found in an adherent cell fraction and were non-specific esterase positive, phagocytic and expressed bovine major histocompatibility complex (MHC) class II determinants, all of which are typical macrophage characteristics. T cells were rigorously depleted of accessory cell function before being used in an antigen presenting cell assay. The generation of T helper cells in response to the soluble antigen, ovalbumin, was entirely dependent upon a critical number of APCs. Further the proliferative response was inhibited by several mAbs to bovine MHC class II molecules. Thus the interaction between bovine APCs and helper/inducer T lymphocytes (TH/I) appears to be similar to that in other species.     

Common and stage-specific antigens of Theileria annulata.

Western blot analysis of Theileria annulata antigens was carried out using sera collected from cattle which had been immunised and challenged with either T. annulata sporozoites or schizont-infected cells. Three antigens between 71 and 73 kDa proved to be common to the three stages of parasite studied: sporozoites, schizonts and piroplasms. An antigen was found at 32 kDa which was specific to T. annulata piroplasms. Results were reproducible using sera from Morocco and the UK. At least one of the proteins at 71-73 kDa, but not that at 32 kDa were also recognised by sera from animals infected with Babesia species.     

Molecular and immunological characterisation of Theileria parva stocks which are components of the 'Muguga cocktail' used for vaccination against East Coast fever in cattle

The 'Muguga cocktail' which is composed of three Theileria parva stocks Muguga, Kiambu 5 and Serengeti-transformed has been used extensively for live vaccination against East Coast fever in cattle in eastern, central and southern Africa. Herein we describe the molecular characterisation of the T. parva vaccine stocks using three techniques, an indirect fluorescent antibody test with a panel of anti-schizont monoclonal antibodies (MAb), Southern blotting with four T. parva repetitive DNA probes and polymerase chain reaction (PCR)-based assays detecting polymorphism within four single copy loci encoding antigen genes. The Muguga and Serengeti-transformed stocks exhibited no obvious differences in their reactivity with the panel of MAbs, whereas Kiambu 5 differed with several MAbs. Kiambu 5 DNA was very distinct from the Muguga and Serengeti-transformed isolates in the hybridisation pattern with all four nucleic acid probes, whereas Muguga and Serengeti-transformed isolates exhibited minor differences and could not be discriminated with one of the probes. PCR amplification in combination with restriction fragment length polymorphism analysis indicated that Kiambu 5 was also markedly divergent from the Muguga and Serengeti-transformed stocks within two of the four antigen coding genes. The T. parva Serengeti-transformed stock did not contain a 130 base pair insert within the p67 sporozoite antigen gene, which has been observed previously in most T. parva parasites isolated from buffalo, and could not be discriminated from T. parva Muguga at any of the four single copy loci. Collectively the data indicate that two of the cocktail components T. parva Serengeti-transformed and Muguga are genetically closely related, while the third component Kiambu 5 is quite distinct. Based on the findings, there may be a need to include only one of the T. parva Muguga and Serengeti-transformed components in the immunising cocktail. The study demonstrates the value of molecular characterisation data for monitoring of live vaccines.     

The effect of dose and line on immunisation of cattle with lymphoblastoid cells infected with Theileria annulata

Thirty-one Friesian calves in Morocco susceptible to tropical theileriosis were protected against a lethal sporozoite challenge by prior infection with lymphoblastoid cell lines infected and transformed in vitro by a Moroccan stock of Theileria annulata. The challenge infection of cryopreserved sporozoites killed all four susceptible control calves within 20 days. Four schizont-infected cell cultures at Passage 3 were inoculated at four different doses, 10(8), 10(6), 10(4) and 10(2), into pairs of calves. The recipient animals showed great variation in severity of disease symptoms, which did not show a linear correlation with the cell dose inoculated. The most severe disease symptoms were recorded, prior to challenge, in the 10(2) cell dose recipients; one animal died of acute theileriosis and another had to be treated. One of the four cell lines used was more virulent than the other three. Two years after the completion of this experiment, immunised animals have shown normal productivity traits.     

Genetics of disease resistance and the potential of genome mapping

Tropical Animal Health and Production -     

A thermogravimetric study of the pyrolysis of the bark and chemically-modified bark of jack pine,pinus banksiana lamb

The pyrolysis of native jack pine bark has been studied from 200 to 340°C by thermogravimetric (TG), and isothermal weight-loss methods. The effects of particle size, solvent extraction and additions of zinc (II) and iron (III) chlorides on the pyrolysis behaviour have also been examined. The bark was characterized by infrared spectroscopy and low-temperature gas adsorption. Residues were analysed for CHN contents and structural changes which occurred on heating were examined by optical and scanning electron microscopy. The TG characteristics were not affected by solvent extraction or particle size variation while the metal chloride additions inhibited the loss of volatile materials from the bark probably by stabilizing chemical bonding in the bark components. Isothermal decomposition data were found to fit established kinetic expressions associated with inorganic decompositions. The physical mechanics of pyrolysis have been interpreted on the assumption that pyrolysis is initiated through the formation of planes of lateral strain which are sites for decomposition and which decrease in number inversely with time. It is suggested that these sites are produced by an oxidation mechanism which may be rate-controlling in the pyrolysis. This hypothesis is supported by the observation that the data fit a reaction rate compensation curve, often associated with oxidation processes but more generally with heterogeneous catalytic reactions. The compensation curve also relates the kinetic parameters found by other workers for a large variety of wood-derived materials.     

A weight‐of‐evidence approach for defining thermal sensitivity in a federally endangered species

1. Managing for threatened and endangered species under changing environmental conditions is a challenge faced by resource managers worldwide. Lack of basic knowledge of the biology and habitat requirements of these species can contribute to this difficulty but is exacerbated by the limitations of working with rare species (i.e. few individuals) or unrefined and non‐lethal methods for evaluating stress.
2. A weight‐of‐evidence approach was used to evaluate the thermal biology of the federally endangered dwarf wedgemussel (Alasmidonta heterodon), using cumulative results from multiple experimental assessments, co‐occurring species, and their host fish to begin defining the thermal limits and optimal conditions for the species.
3. Results suggest that dwarf wedgemussel and its host fish are thermally sensitive species compared with other Atlantic‐slope mussels, with a lower critical thermal maximum (CTM) and the selection of reduced temperatures during choice experiments.
4. Physiological studies resulted in a lack of statistical significance, primarily owing to low power, which was a function of sample size – an unavoidable problem when studying rare species. Given these limitations, thermal choice and CTM may be more useful end points than physiological processes such as clearance and respiration rates when dealing with sample‐size limitations.
5. These results suggest that management strategies that avoid exposing dwarf wedgemussel and its thermally sensitive host fish to extreme temperatures could be important for species conservation.

     

Ecuador, 1991 potato germplasm collecting expedition: taxonomy and new germplasm resources

Summary We conducted a joint Ecuador/Colombia/United States wild potato (Solanum sect. Petota) germplasm collecting expedition in Ecuador from April 13–July 1, 1991. The goals of the expedition were to collect germplasm and study the species boundaries of all of the 25 Ecuadorian taxa accepted by current taxonomists. We made 126 collections of 24 of these 25 taxa, 113 as germplasm samples, 13 only as herbarium collections. We synonymize six of these 25 names (S. baezense Ochoa, S. cyanophyllum Correll, S. pichinchense Bitter & Sodiro, S. serratoris Ochoa, S. suffrutescens Correll as synonyms of S. andreanum Baker; S. correllii Ochoa as a synonym of S. regularifolium Correll). Four other names (S. chomatophilum f. angustifoliolum Correll, S. moscopanum Hawkes, S. solisii Hawkes, S. tundalomense Ochoa) could not be consistently distinguished from S. colombianum Dunal in the field. We are currently investigating them to determine their species status.