PubMed Health⌕ Search

Biomedical subjects

D H Molyneux

Publications and source records attributed to D H Molyneux.

At least 73 records · Page 4Linked to original sources
PubMed1990

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↗
PubMed1990

The possible role of Rickettsia-like organisms in trypanosomiasis epidemiology.

A simple model of human and animal trypanosomiasis is proposed in which the Ross equation for disease transmission is supplemented by a differential equation describing the inheritance of susceptibility in the vector. The model predicts an equilibrium state of balanced polymorphism for the fraction, theta, of susceptible tsetse and the occurrence of periodic epidemics at roughly the observed intervals. A loss of infectivity to tsetse of mechanically transmitted strains of trypanosome would seem to be a good evolutionary strategy for the trypanosome. The main implication for disease control is that measures initially reducing trypanosomiasis incidence could trigger off subsequent epidemics. Since theta leads incidence, monitoring theta could give several years advance warning of major epidemics. The model leads to oscillations in prevalence which are only lightly damped. Other mechanisms producing periodic epidemics would interact with this mechanism, and result in only one sequence of recurrent epidemics. With typical random variation of tsetse numbers about the seasonal norm the model shows the behaviour of a narrow-band system excited by broad-band noise, i.e. predicted trypanosomiasis incidence exhibits an undamped series of oscillations of variable amplitude and phase, similar to what is actually observed.

Animals↗
PubMed1990

Avian trypanosomes in Simulium and sparrowhawks (Accipiter nisus).

Isolates of avian trypanosomes from nestling sparrowhawks (Accipiter nisus) and from Simulium latipes were compared by isoenzyme electrophoresis with the previously described avian trypanosomes Trypanosoma corvi and T. everetti. Simulium isolates developed into trypomastigotes in semi-defined medium at 37 degrees C confirming that they belong to the genus Trypanosoma. Cellulose acetate electrophoresis (CAE) and polyacrylamide gel electrophoresis (PAGE) methods were employed. A total of 11 enzymes was examined, of which 8 gave satisfactory results for all lysates (MDH, ICD, PGM, 6PGD, SOD, PEP I, PEP II and PEP D). The zymograms of 3 isolates from Simulium and 4 from A. nisus were similar indicating that they were the same organism and the isoenzyme patterns coincided with those of T. corvi. It is concluded that A. nisus and S. latipes are infected with T. corvi. Flagellate infections were found in the midgut, hindgut and rectum of Simulium where large numbers of epimastigotes were found in the lumen and attached to the cuticular intima of the rectal ampullae by hemidesmosomes at the distal end of an expanded flagellum. Out of 285 nestling sparrowhawks 13 (5%) were infected with trypanosomes. In view of their age and inability to preen themselves it is suggested they became infected via infected prey.

Animals↗
PubMed1990

Trypanocidal effects of catecholamines and indolealkylamines.

Catecholamines, indolealkylamines and their analogues are oxidized at neutral or alkaline pH, producing hydrogen peroxide, quinones and free radicals. Several of these amines were tested for trypanocidal effects on Trypanosoma brucei, which possess a well-documented vulnerability to such oxidation products. Dopamine, 5-hydroxydopamine (5-OHDA), 6-hydroxydopamine (6-OHDA), 5-hydroxytryptamine (5-HT), 5,6-dihydroxytryptamine (5,6-DHT) and 5,7-dihydroxytryptamine (5,7-DHT) killed the parasites in vitro, using a fibroblast feeder layer cell culture system, in four to 48 hours at concentrations of 10(-5)-10(-7) M. The 5-OHDA, 6-OHDA, 5,6-DHT and 5,7-DHT were also effective in vivo when tested by intraperitoneal injection of infected mice.

Animals↗
PubMed1990

Intraspecific variation in the cuticular hydrocarbons of the sandfly Phlebotomus perfiliewi from Italy.

The cuticular hydrocarbons of Phlebotomus perfiliewi Parrot from representative localities on both sides of Italy show contrasts which support the view of Ward et al., (1981) that there are distinguishable populations of this sandfly on the Adriatic and Tyrrhenian coasts. It is suggested that the Appennine mountains form a barrier between the Adriatic and Tyrrhenian populations. A third distinct hydrocarbon type of P. perfiliewi was detected in Calabria, southern Italy, where contact between the Adriatic and Tyrrhenian types of flies is most likely to occur. P. perfiliewi from a trans-Appennine pass were also of the Calabrian hydrocarbon type. These hydrocarbon contrasts between allopatric populations of P. perfiliewi may result from clinical variation across the Appennines, associated with different host preferences, or they may represent apomictic populations with differential mate recognition systems.

Animals↗
PubMed1990

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.

Animals↗
PubMed1990

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.

Agglutination Tests↗
PubMed1989

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.

Animals↗
PubMed1989

Studies on cross-immunity in Herpetosoma trypanosomes of Microtus, Clethrionomys and Apodemus.

Laboratory-bred rodents of three species were inoculated with heterologous Herpetosoma trypanosome species as follows: Microtus agrestis with Trypanosoma evotomys or T. grosi, Apodemus sylvaticus with T. evotomys or T. microti and Clethrionomys glareolus with T. grosi or T. microti. The three rodent species were subsequently challenged with their natural trypanosome parasite, i.e. T. microti for M. agrestis, T. grosi for A. sylvaticus and T. evotomys for C. glareolus. The parasitaemias and courses of infection that developed were followed. All challenged animals showed some degree of cross-immunity; not all became infected, and those that did had lower levels of parasitaemia and shorter patent periods than control animals. No C. glareolus previously inoculated with T. microti developed T. evotomys infections on challenge, and an infection was observed in just one of ten M. agrestis inoculated first with T. evotomys and later with T. microti.

Animals↗
PubMed1989

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.

Animals↗
PubMed1989

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.

Agglutination↗
PubMed1989

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↗
PubMed1988

Effects of trypanocides on Herpetosoma in a mammalian feeder layer cell culture.

Limited studies have been undertaken on the treatment of infections with trypanosomes of the subgenus Herpetosoma, either in comparative studies on the effects of trypanocidal drugs or as potential non-pathogenic models for evaluating trypanocidal activities. The development of an in vitro cell culture system is described which enabled testing of trypanocides against 5 different species of Herpetosoma. The trypanocides used were Samorin, Novidium, Trypacide and Berenil. Variations were observed in the trypanocidal activity of the drugs on the different Herpetosoma parasites, e.g. T. lewisi and Samorin and T. microti and Novidium, compared with other parasites. Minimum effective concentration of Trypacide and Berenil against 5 Herpetosoma trypanosomes were of the order 10 mg ml-1. The results indicate that these parasites are much less sensitive to the drugs used than pathogenic, salivarian trypanosomes.

Animals↗
PubMed1988

Schizotrypanum in British bats.

Two species of Schizotrypanum, T. (S.) dionisii and T. (S.) vespertilionis, were identified from British bats. Laboratory studies on stocks of isolated trypanosomes from 5 species of bat (Pipistrellus pipistrellus, Nyctalus leisleri, N. noctula, Eptesicus serotinus and Myotis brandti) indicated that the predominant species was T. d. dionisii. Collections and dissection of the bat bug Cimex pipistrelli from bat roosts revealed flagellate infection in a total of 12 out of 20 bugs; 7 of these bugs had metacyclic trypanosomes present. C. pipistrelli and the human bed bug, C. lectularius were reared in the laboratory and allowed to feed on wild-caught bats known to be infected with T. d. dionisii. Development occurred in both species of Cimex. Cimex spp. could be used to detect subpatent Schizotrypanum infections by xenodiagnosis. This technique was used to test the parasitological status of bats collected in the wild or reared in captivity. On a single occasion an apparent transmission of T. d. dionisii to an uninfected (by xenodiagnosis) laboratory reared bat was achieved. A stock of Schizotrypanum isolated from a wild-caught C. pipistrelli collected in a N. leisteri roost was identified by DNA buoyant density centrifugation as T. (S.) vespertilionis. A P. pipistrellus known to be infected with T. d. dionisii was found to have cyst-like structures in thoracic skeletal muscle containing amastigotes. The study provided the strongest evidence yet that C. pipistrelli is the vector of Schizotrypanum in British bats.

Animals↗