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J K Stiles

Publications and source records attributed to J K Stiles.

6 recordsLinked to original sources

Trypanosomatid--vector interactions.

Over recent years there has been an increasing interest in the interaction between Trypanosomatids and in particular the genera Trypanosoma and Leishmania and their vectors. These studies on the "vector parasite interface" have been wide ranging but often suffer from the difficulties of manipulating some of the vector systems. It is now likely that molecular biological and protein analysis techniques can be more effectively applied in dissecting these interactions with a view to identification and characterisation of molecules which control parasite behaviour in vectors. This presentation will review recent studies on Glossina lectins in relation to trypanosome behaviour in flies including recent studies on different G. palpalis subspecies as well as review evidence that trypanosomatids have an effect on their insect hosts for example, on feeding behaviour, susceptibility to insecticides and longevity of infected vectors. Sugars are known to influence development and transmission of Leishmania and recent studies have indicated that aphid/or coccid honeydew is taken by sandflies, the relevance of this to Leishmania/sandfly interactions will be discussed. The basic mechanisms of attachment observed in all trypanosomatid interactions are described and the presence of molecules associated with attachment have been identified. The genetic basis of susceptibility is also becoming better understood and it is to be expected that modern molecular techniques when applied to well defined systems can give results which could permit an attempt at intervention; even if this is not achieved the basic understanding of a widespread phenomenon of the insect/parasite association will have been furthered to permit a better epidemiological knowledge.

Animals

Zymogram and life-history studies on trypanosomes of the subgenus Megatrypanum.

Of 13 Swedish dairy cows examined, 12 (92.3%) were found to be infected with trypanosomes by cultivation of blood samples. Of the two species of tabanid fly caught close to the cattle, 33.3% of the Tabanus bromius and 8.6% of the Haematopota pluvialis were also found to be infected with trypanosomes on dissection. Isoenzyme patterns of trypanosome isolates from one H. pluvialis and from six cattle were identical, incriminating this fly species as a vector of the trypanosome. Comparison of these isolates with other Megatrypanum isolates indicated that the Swedish parasites were a form of Trypanosoma theileri and that T. theileri and the badger parasite T. pestanai are closely related. An isolate of a Megatrypanum from a buffalo (Syncerus caffer) in Kenya was entirely different from T. theileri.

Animals

Identification of midgut trypanolysin and trypanoagglutinin in Glossina palpalis sspp. (Diptera: Glossinidae).

A midgut trypanolysin and an agglutinin from Glossina palpalis subspecies were isolated and partially characterized using anion-exchange chromatography and polyacrylamide gel electrophoresis. FPLC fractions of midgut extracts of Glossina palpalis palpalis caused agglutination and lysis of two trypanosome species (Trypanosoma congolense and Trypanosoma brucei brucei), although Glossina palpalis gambiensis caused only agglutination. The trypanolysin and agglutinin were active only in the posterior midguts, were heat labile above 50 degrees C, had a periodic cycle of 'activity' in response to bloodmeal intake and were not affected by protease inhibitors or trypsin but were inactivated by pronase. The lytic substance contained two proteins with approximate molecular weights (Mr) of 12,000 and 10,000 Da respectively. The agglutinin had an approximate Mr of 67,000 Da. Gamma-irradiation of the two subspecies caused a temporary inhibition of trypanolytic and agglutinin activities in midgut extracts.

Agglutination

Effects of gamma irradiation on the midgut ultrastructure of Glossina palpalis subspecies.

In the sterile insect technique, insects are sterilized prior to release in areas where they are pests. The sterile males compete for and with fertile wild individuals for mates, thus reducing the population's reproductive rate. Tsetse fly (Glossina spp.) populations have been eradicated after release of laboratory-bred flies sterilized by gamma irradiation. However, no studies exist on radiation-induced damage to the midgut morphology and function of the radiation-sterilized insects. After G. palpalis palpalis and G. p. gambiensis were subjected to 130 Gy gamma radiation, their midgut damage and recovery were monitored by electron microscopy. The first sign of damage was atrophy and loss of the microvillous border from epithelial cells. The rate of cell degeneration increased, with young as well as old cells being affected and cellular debris filling the ectoperitrophic space. Muscle cells were destroyed, patches of basal lamina were left bare, intracellular virus- and rickettsia-like organisms became more frequent, and many replacement cells became unusually large. Partial recovery occurred from the 10th day postirradiation. Such changes in midgut ultrastructure and the corresponding inhibition of functions may increase the susceptibility of the fly to trypanosome infection.

Animals