Biomedical subjects
K R Wallbanks
Publications and source records attributed to K R Wallbanks.
In vitro cultivation of Trypanosoma acomys: production of insect stages and bloodstream forms.
When Trypanosoma acomys bloodstream forms were cultivated at 37 degrees C in Schneider's Drosophila medium supplemented with 20% (v/v) heat-inactivated foetal calf serum (FCS), with Microtus agrestis embryonic fibroblasts in RPMI 1640 medium supplemented with 20% FCS or in Baltz's medium supplemented with 10% FCS, the parasites transformed and largely remained as epimastigotes. Epimastigotes were also usually the commonest stage observed when the parasites were co-cultivated with a mosquito cell line at 27 degrees C. However, if these cultures were initiated with the supernatant suspensions from fibroblast cultures that had been cryopreserved, trypomastigotes, including bloodstream-like forms, were the predominant stage for the first 4 days of culture. It is suggested that the glycerol supplement or the temperature changes stimulated this unusual morphogenesis. At 27 degrees C, T. acomys was incapable of multiplying and died when cultured in fresh Schneider's Drosophila medium supplemented with 20% FCS, but co-cultivation with the mosquito cell lines or cultivation in cell-free supernatants from 1-week-old mosquito cell cultures was successful at this temperature; most of the parasites multiplied as epimastigotes.
Oral transmission of trypanosomes of the subgenus Herpetosoma from small mammals.
The rodents Microtus agrestis, Clethrionomys glareolus, Apodemus sylvaticus and white BK rats were given either a single intraperitoneal (i.p.) injection, an intragastric (i.g.) inoculation or an oral (p.o.) inoculation of the culture forms, including metacyclic trypomastigotes, of Trypanosoma microti, T. evotomys, T. grosi and T. lewisi, respectively. Similar levels of parasitaemia were produced by each of the three routes of infection, although the prepatent period was 3-5 days shorter in the case of the i.p.-injected animals. The oral inoculation of blood from mice infected with T. musculi into uninfected mice (outbred) and from rats infected with T. lewisi into uninfected BK rats produced parasitaemia after 6-8 days. This is the first report of the oral and i.g. transmission of T. microti, T. evotomys and T. grosi into their specific homologous hosts.
Comparison of Trypanosoma grayi-like isolates from west and east Africa.
Three flagellates recently isolated from the hindguts of tsetse flies in West Africa were compared with a previously described T. grayi-like trypanosome isolated in East Africa. In media with Microtus agrestis feeder layer cells, the flagellates developed into bloodstream-like trypomastigotes, which resembled the description of T. grayi from the blood of crocodiles. The results of isoenzyme electrophoresis suggest that the isolates are T. grayi-like trypanosomes, and that some variation exists between the West and East African stocks of these reptile trypanosomes.
Aphid derived sugars in the neotropical sandfly--Lutzomyia peruensis.
It is known that a sugar meal is a prerequisite for the transmission of Leishmania by sandflies in the laboratory. Lutzomyia peruensis the proven vector of Leishmania peruviana, was caught by aspiration from crevices in rocks near Chaute in the Rimac Valley, Peru, cryopreserved and analysed for sugars using HPLC. The major sugars present are glucose and fructose as well as smaller amounts of sucrose, maltose, melibiose, turanose and a trisaccharide, probably raffinose. The results indicate that the major carbohydrate sugar meal of Lutzomyia peruensis is aphid honeydew. This is the first report of such behaviour in Neotropical sandflies.
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.
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.
Metacyclogenesis of Trypanosoma vivax in vitro: attachment to chitosan gel.
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Surface carbohydrate differences of Glossina salivary glands and infectivity of Trypanosoma brucei gambiense to Glossina.
Incubation of fluorescein- and biotin-lectin conjugates with the salivary glands of Glossina spp has revealed inter- and intraspecific variation in the surface carbohydrates of the glands. The degree of Con A binding to the basal laminae of the glands of the two Glossina palpalis subspecies, G.p. palpalis and G.p. gambiensis was markedly different. The infectivity of T.b. gambiense sensu lato isolates to G.p. palpalis and G.p. gambiensis was compared. G.p. gambiensis from the field and from laboratory colonies transmitted T.b. gambiense sensu lato isolated from patients in Ivory Coast whereas G.p. palpalis appears totally refractory to all T.b. gambiense isolates used. Although the relationship between the surface of the basal laminae of the salivary gland exposed to the haemocoele and trypanosome infection is not known the consistent differences observed in lectin binding to the salivary glands suggest that differences in basic physiology of the glands exist which might correlate with susceptibility to trypanosome infection.
Comparative studies on Megatrypanum trypanosomes from cervids.
Trypanosomes were isolated by culture from 2 out of 50 blood samples collected from reindeer (Rangifer tarandus L.) in northern Sweden and from a blood sample from a moose (Alces alces) from Southern Sweden. The parasites were indistinguishable morphologically from other trypanosomes reported from cervids, both as epimastigotes in axenic culture at 27 degrees C and as bloodstream-like trypomastigotes cultured on mammalian fibroblasts at 37 degrees C. Surface carbohydrate and isoenzyme comparison of these isolates with four American isolates, from reindeer (Rangifer tarandus), mule deer (Odocoileus hemionus), moose (Alces alces) and elk (Cervus canadensis), are reported. The isoenzyme patterns of the isolate from the Swedish moose were similar to those of the isolates from America while the patterns of the 2 isolates from the Swedish reindeer were considerably different from the others; these 2 isolates may represent a new species. Lectins can be used to distinguish between the trypanosomes of cervids.
Camel trypanosomiasis and its vectors in Somalia.
Blood samples from 3000 Somali camels (Camelus dromedarius) were examined for trypanosome infection. Of these, 160 (5.33%) were infected with Trypanosoma evansi, one (0.03%) with T. congolense and one (0.03%) with T. brucei. Camel trypanosomiasis occurred in most areas of tabanid infestation throughout the country. The tabanids Philoliche zonata and P. magretti are incriminated as the major vectors of the disease.
Host-parasite relationship of Trypanosoma corvi in Ornithomyia avicularia.
The first description of an electron microscopic study of Trypanosoma corvi in the vector Ornithomyia avicularia is reported. There is a close association between vector and parasite in the midgut, ileum and rectum of the vector. The midgut distribution of parasites is determined by the peritrophic membrane, which confines the early infection to the endoperitrophic space. Parasites escape from the ruptured region of the peritrophic membrane at the pylorus to gain access to the ectoperitrophic space, where intense multiplication occurs. The resulting, smaller epimastigotes attach to the cuticle in the pylorus, ileum and rectum, where they continue multiplying to give rise to mature, short, stumpy trypomastigotes (metacyclics) that are not attached. Attachment to these cuticularly lined regions occurs by the formation of dense, hemidesmosome-like plaques at the extremities of the expanded flagella. A fibrous matrix surrounds the parasites in the ileum. For the first time, intracellular midgut forms are reported for T. corvi in O. avicularia. These parasites enter the cells between the microvilli and penetrate deeply between the folds of the midgut. In the midgut of O. avicularia, the cells of a mycetome region are packed with Rickettsia-like organisms. The significance of these intracellular parasites in the relationship of T. corvi in O. avicularia remains unknown.
Chitin derivatives as novel substrates for Trypanosoma brucei brucei attachment in vitro.
Procyclic trypomastigotes of Trypanosoma brucei brucei, cultured in Cunningham's medium with 20% heat-inactivated foetal calf serum at 27 degrees C, attached to chitosan and to gels of N-acetyl chitosan and glycol chitosan. Following attachment, epimastigotes, metacyclic-like trypomastigotes and multinucleate parasites appeared in the culture supernatant.
Differentiation of rodent trypanosomes of the subgenus Herpetosoma by lectins.
Trypomastigote forms of Trypanosoma microti, T. evotomys, T. grosi, T. musculi, and T. lewisi and trypomastigote and epimastigote forms of T. acomys were differentiated using 34 lectins and the Aminoff test for N-acetylneuraminic acid (NANA). Twelve of the lectins failed to agglutinate any of the above species. The number of lectins which agglutinated each species differed; T. mciroti, T. evotomys, T. grosi, T. musculi, T. lewisi and T. acomys (trypomastigote and epimastigote forms) were agglutinated by 7, 14, 7, 13, 11 and (11 and 10) lectins respectively. Some of the lectins were common in agglutinating all species of parasites, for example Bauhinia purpurea, Caragana aborescens and Viscum album. The minimum concentration of lectins which agglutinated each parasite was quite different. The agglutinations were cell body-cell body, flagellum-flagellum or flagellum-cell body. Most of the agglutinations were inhibited by their specific carbohydrates. The lowest concentrations of NANA was observed in T. lewisi (0.3 micrograms/ml) and the highest in T. musculi (4.5 micrograms/ml). The concentrations of NANA in T. microti, T. grosi and in T. acomys (trypomastigote and epimastigote forms) were 2, 1.8, 2.9, and (1.4 and 1.2) micrograms/ml respectively.
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.
The ultrastructure of Leishmania major in the foregut and proboscis of Phlebotomus papatasi.
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The peritrophic membrane of the female sandfly Phlebotomus papatasi.
The ultrastructure of the peritrophic membrane of the female sandfly Phlebotomus papatasi has been studied at various times after blood meals. The membrane begins to form within four hours of the blood meal with the secretion by the entire midgut epithelium of an electron-dense amorphous material. Subsequently, the membrane is stabilized and strengthened by the production of a layer of irregular chitinous microfibres, the whole membrane then forming a complete and resilient sac apparently unaffected by boiling 9 M potassium hydroxide. The membrane appears redundant 48 hours after the blood meal and fragments, possibly as a result of chitinase activity. The membrane's main functions are probably the prevention of clogging of the microvillous brush border by the blood meal and the confinement of large proteins, particularly serum trypsin inhibitors, to the endoperitrophic space while allowing sandfly proteases access to the blood meal periphery. Blood is not required to stimulate membrane production. Saline taken by blood feeding into the midgut also stimulates membrane formation. Phlebotomus papatasi females may lack an efficient anticoagulant, at least in the midgut, as blood meals frequently include fibrin clots.
Haemorrhagic syndrome associated with T. vivax infections of cattle in Somalia.
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