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Biomedical subjects

A R Gray

Publications and source records attributed to A R Gray.

At least 37 records · Page 2Linked to original sources
PubMed1976

Observations on a herd of beef cattle maintained in a tsetse area. II. Assessment of the development of immunity in association with trypanocidal drug treatment.

Three groups of Boran cattle were maintained under different trypanocidal drug regimes for 29 months in an area of "medium" tsetse challenge. The development of immunity to trypanosmiasis in the cattle was assessed on the basis of changes in trypanocidal drug requirement, development of parasitaemia, ability to maintain normal blood values, growth and response to challenge after the withdrawal of the drugs. Observations were also made on serum antibody content by immunofluorescence and on serum immunoglobulin levels. Cattle treated with Berenil on the development of clinical disease developed a partial immunity to trypanosomiasis after two years. Cattle treated as a group with Berenil on the development of patent parasitaemia in any one animal of the group did not develop immunity. Cattle treated as a group with Samorin using the same criterion for treatment developed a degree of immunity to the disease. It was concluded that group treatment with Samorin was the most suitable of the three regimes examined for the maintenance of beef cattle is a tsetse infested area.

Animals↗
PubMed1976

A study of the antigenic relationships of isolates of Trypanosoma brucei from three areas in East Africa.

Eleven stabilates of T. brucei, prepared from isolates collected from cattle and tsetse flies in three areas of East Africa, were compared serologically by direct agglutination tests, using (a) stabilate-specific antisera prepared in rats and (b)antisera to the predominant variant antigens of each isolate prepared in rabbits. The results indicated that groups of isolates from any one area tended to produce antigens in common, whereas isolates from different areas were generally antigenically distinct. The comparison of isolates of T. brucei on the basis of their predominant variant antigens, as a technique, was more simple to effect, and more sensitive in the detection of antigenic relationships, than comparison founded on basic strain antigens.

Agglutination Tests↗
PubMed1975

A pattern in the development of agglutinogenic antigens of cyclically transmitted isolates of Trypanosoma gambiense.

Three isolates of T. gambiense, belonging to 2 serologically different substrains of the species, were cyclically transmitted to rabbits and monkeys by G. morsitans or G. tachinoides. Sera collected from the infected animals were tested for agglutinating antibodies to 17 different serotype antigens prepared from rodent-adapted isolates of T. gambiense. The first antibodies detected in sera from all of the animals agglutinated the same serotype antigen L2, indicating that it possibly consisted of trypanosomes bearing a basic antigen of T. gambiense. In 2 animals infected with 1 isolate the development of antibody to the common serotype L2 was accompanied by the development of antibody to a second serotype U1. Comparisons of the patterns in which antibodies were produced to other serotype antigens in different animals indicated that there were many similarities in the sequences in which they developed in different rabbits infected with (a) any 1 isolate (b) 2 different isolates of 1 substrain and (c) isolates of 2 serologically different substrains. There were also similarities in the sequences in which the antigens developed in rabbits and monkeys infected with an isolate by the same fly or by different tsetse flies. The ordered sequence in which these 3 cyclically transmitted isolates of T. gambiense, of significantly varied origin and laboratory history, produced variant antigens in hosts of different species provides further evidence to support previous suggestions that antigenic variation in trypanosomes is an adaptive process, rather than one involving selection of mutants.

Adaptation, Biological↗
PubMed1969

The epidemiological significance of some recent findings from research on antigenic variation in trypanosomes.

Antigenic variation in trypanosomes has been recognized for many years and is of epidemiological significance because of the way in which it enables the organisms to resist the natural defence mechanisms of the host and thus to survive in parasitized animals, causing disease and providing a reservoir of further infection. Antigenic variation also limits attempts to use serological methods to type and determine the species of trypanosome isolates, to diagnose trypanosome infections and to immunize against trypanosomiasis.Recent research on antigenic variation in syringe-passaged and cyclically transmitted strains of brucei subgroup trypanosomes has indicated that each strain produces a characteristic basic antigen and a group of predominant variant antigens and that the over-all antigenic character of a strain remains stable under field conditions for periods of at least 2 years. It might be possible to classify isolates of brucei subgroup trypanosomes on the basis of their predominant variant antigens and to determine the species of new isolates by comparing their patterns of variant antigen production with those of fully identified type-strains in rabbits. The significance of results from the application of these findings in the field are discussed. Little progress has been made towards solving the problem of differentiating between antibodies to different species of trypanosomes in the serum of infected animals or with the development of methods of immunization against trypanosomiasis.

Animals↗