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D H Molyneux

Publications and source records attributed to D H Molyneux.

At least 19 recordsLinked to original sources
PubMed1992

Carbohydrate-binding specificities of anti-erythrocyte lectins (haemagglutinins) in Anopheles gambiae gut extracts and haemolymph.

Lectins that agglutinate red blood cells (RBC) were demonstrated in Anopheles gambiae mosquito haemolymph and gut extracts. No apparent differences in haemagglutinin titres were detected between male and female mosquitoes and overall agglutinin levels were not increased following a bloodmeal. Titres were highest in the haemolymph and midgut extracts versus human AB, horse, chicken and goat RBCs and in hindgut against human AB, chicken and sheep; foregut extract gave relatively low titres. Adsorption of haemolymph and gut extracts with selected RBCs coupled with carbohydrate inhibition and the use of enzyme-treated RBCs revealed the presence of multiple (hetero-) agglutinins. An.gambiae lectins were specific for (1-1)-, (1-4)- or (1-6)-linked glucose based disaccharides, glucose and its (1-2) or (1-3) linkages with fructose and, to a lesser extent, aminated or N-acetylated glucose, or galactose and its deoxy derivatives. This study presents the first report of the occurrence of heterogenous anti-RBC agglutinins in haemolymph and gut extracts of the mosquito An.gambiae, together with the sugar-binding specificities of these lectins.

Adsorption↗
PubMed1992

Cuticular hydrocarbons, isoenzymes and behavior of three populations of Anopheles darlingi from Brazil.

Three populations of Anopheles darlingi were studied for cuticular hydrocarbons, isoenzymes and patterns of peak biting activity. Differences were found in specimens from Costa Marques, a malaria endemic area; Dourado, a site with a very exophilic population and Juturnaíba, located near the type locality. Twelve hour collections from sunset to sunrise showed that An. darlingi from Costa Marques had a bimodal biting activity profile with a major peak at sunset and a minor peak at sunrise. At Dourado, the pattern was trimodal, with peaks at both morning and evening periods of twilight and near midnight. The Juturnaíba population showed a slight increase in activity near 2000 and 0100 h. Nei's genetic distances, determined by isoenzyme electrophoresis between pairs of populations, were low (D < or = 0.049). Using discriminant analysis for the cuticular hydrocarbons, 92.4% of the specimens from Costa Marques, 91.2% of the specimens from Dourado and 61.3% from Juturnaíba were correctly identified. Cuticular hydrocarbon and isoenzyme results matched very well: the smaller the Nei's distance, the more misidentifications occurred in the jackknife estimator used in the cuticular hydrocarbon analysis. This is the first report of cuticular hydrocarbon analysis in combination with isoenzymes to investigate neotropical anopheline species.

Animals↗
PubMed1991

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.

Africa, Western↗
PubMed1991

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↗
PubMed1991

Urbanization--how does it affect the behaviour of sandflies?

The effect of building activities on the abundance of sandflies was investigated in Jordan. A total of 3442 sandflies were collected. The largest collections were made from natural habitats, uninhabited and inhabited houses. Collections from the latter two often included a larger number of Phlebotomus species. It was evident from this study that sandfly populations are able to recover to, and often exceed their original natural densities in man-made artificial habitats.

Animals↗
PubMed1991

The behaviour and dispersal of sandflies in Ras el Naqb, south Jordan with particular emphasis on Phlebotomus kazeruni.

The behaviour and dispersal of sandflies from an enclosed cave were investigated during the summer of 1988 in Ras el Naqb by the mark-release-recapture technique. Nine species of sandflies were reported during this study including 5 Phlebotomus and 4 Sergentomyia species. P. sergenti, P. alexandri, S. adleri/S. clydei and S. taizi were reported for the first time from Jordan. P. kazeruni was the most abundant sandfly species inside the cave. The maximum distance travelled by a single P. kazeruni was 340m. However, the majority were recaptured within 10m of the cave. It seems likely that an independent "population" of sandflies which breeds inside the cave is developing.

Animals↗
PubMed1991

Sugars in sandflies.

The evidence for the acquisition of different types of sugars by wild caught sandflies is reviewed and the recent results summarised. Studies on Phlebotomus ariasi, P. perfiliewi and P. perniciosus in the Mediterranean region has shown that these sandflies take honeydew derived sugars from aphids or coccids; in a similar study in the New World, Lutzomyia peruensis has also been shown to have taken sugar from such sources. The use of High Performance Liquid Chromatography (HPLC) as a technique for identification of such sugars is used as a more sensitive method for identifying trisaccharides and disaccharides; this method should supersede the van Handel cold anthrone test for sugar identification which only identifies the presence of fructose moieties. The possible significance of sugar feeding in the biology of sandflies and for the transmission of Leishmania are discussed.

Animals↗
PubMed1991

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.

Animals↗
PubMed1990

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↗
PubMed1990

Separation of Psychodopygus carrerai carrerai and P. yucumensis (Diptera: Psychodidae) by gas chromatography of cuticular hydrocarbons.

Specimens of two species of sandfly, Psychodopygus carrerai carrerai and P. yucumensis, vectors of Leishmania braziliensis braziliensis in the subandean lowlands of Bolivia, were subjected to cuticular hydrocarbon analysis to ascertain if the technique could separate the females. A high degree of separation (87%) was obtained based on significant differences in the cuticular hydrocarbon composition of these two species. Statistical treatment of the data shows that these species, initially identified by the colour of the mesonotum, can also be distinguished by their hydrocarbons.

Animals↗
PubMed1990

The effect of Blastocrithidia triatomae (Trypanosomatidae) on the midgut of the reduviid bug Triatoma infestans.

The pathogenic flagellate Blastocrithidia triatomae disrupts the digestion of Triatoma infestans; the midgut ultrastructure of bugs infected with the flagellate and of uninfected bugs is compared. Third or fourth instar larvae were dissected either unfed or 1 week after feeding. In all uninfected bugs extracellular membrane layers (e.m.l.) covered the apical microvillar border of the epithelial cells. Some midgut regions of bugs infected with B. triatomae appeared normal but often adjacent cells showed pathological effects. In affected cells the e.m.l. and the microvilli and finally the cells themselves were reduced or destroyed. Correlated with these observations of pathogenicity the method of attachment of parasites changed. When the e.m.l. were present only rarely were flagella found, but on extracellular membrane-free cells B. triatomae attached by flagellar enlargement to the microvillar border or, if this was reduced, to the apical host cell membrane. No hemidesmosome-like plaques were found at the attachment site. Although some flagella were inserted into the apical region of the cells no intracellular flagellates were observed.

Animals↗
PubMed1990

Developmental stages of Cyclospora talpae in the liver and bile duct of the mole (Talpa europaea).

The completed life-cycle of Cyclospora talpae, an extra-intestinal coccidian (Apicomplexa) of the liver of the mole (Talpa europaea), is reported. Oocysts sporulated within 12-14 days at room temperature (20-22 degrees C). Both macro- and microgametocytes developed independently within the nucleus of epithelial cells lining the bile duct as demonstrated by both light and electron microscopy. Merogony was seen in the mononuclear cells in the capillary sinusoids of the liver. Merozoites showed the typical ultrastructural features of the Apicomplexa. The life-cycle of C. talpae and the ultrastructure of the gametogonic and merogonic stages are reported; the ultrastructure of the merozoites is reported as the first description of this stage for the genus Cyclospora.

Animals↗
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↗