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At least 19 recordsLinked to original sources
PubMed2025

Spiroplasma endosymbiont reduction of host lipid synthesis and Stomoxyn-like peptide contribute to trypanosome resistance in the tsetse fly Glossina fuscipes.

Tsetse flies (Glossina spp.) vector African trypanosomes that cause devastating diseases in humans and domestic animals. Within the Glossina genus, species in the Palpalis subgroup exhibit greater resistance to trypanosome infections compared to those in the Morsitans subgroup. Varying microbiota composition and species-specific genetic traits can significantly influence the efficiency of parasite transmission. Notably, infections with the endosymbiotic bacterium Spiroplasma have been documented in several Palpalis subgroup species, including Glossina fuscipes fuscipes (Gff). While Spiroplasma infections in Gff are known to hinder trypanosome transmission, the underlying mechanisms remain unknown. To investigate Spiroplasma-mediated factors affecting Gff vector competence, we conducted high-throughput RNA sequencing of the gut tissue along with functional assays. Our findings reveal elevated oxidative stress in the gut environment in the presence of Spiroplasma, evidenced by increased expression of nitric oxide synthase, which catalyzes the production of trypanocidal nitric oxide. Additionally, we observed impaired lipid biosynthesis leading to a reduction of this important class of nutrients essential for parasite and host physiologies. In contrast, trypanosome infections in Gff's midgut significantly upregulated various immunity-related genes, including a small peptide, Stomoxyn-like, homologous to Stomoxyn first discovered in the stable fly, Stomoxys calcitrans. We observed that the Stomoxyn-like locus is exclusive to the genomes of Palpalis subgroup tsetse species. GffStomoxyn is constitutively expressed in the cardia (proventriculus) and synthetic GffStomoxyn exhibits potent activity against Escherichia coli and bloodstream form of Trypanosoma brucei parasites, while showing no effect against insect stage procyclic forms or tsetse's commensal endosymbiont Sodalis in vitro. Reducing GffStomoxyn levels significantly increased trypanosome infection prevalence, indicating its potential trypanocidal role in vivo. Collectively, our results suggest that the enhanced resistance to trypanosomes observed in Spiroplasma-infected Gff may be due to the reduced lipid availability necessary for parasite metabolic maintenance. Furthermore, GffStomoxyn could play a crucial role in the initial immune response(s) against mammalian parasites early in the infection process in the gut and prevent gut colonization. We discuss the molecular characteristics of GffStomoxyn, its spatial and temporal expression regulation and its microbicidal activity against Trypanosome parasites. Our findings reinforce the nutritional influences of microbiota on host physiology and host-pathogen dynamics.

Animals↗
PubMed1978

Cyclic AMP is a likely mediator of ovulation in the tsetse fly.

Ovulation in tsetse flies is normally induced by mating, but virgins can be stimulated to ovulate with an injection of dibutyryl cyclic AMP, cholera toxin (a cyclic AMP generator), or aminophylline (a phosphodiesterase inhibitor). Thus, elevation of cyclic AMP is a likely link in the events leading to ovulation.

Aminophylline↗
PubMed1975

The micro-organisms of tsetse flies.

Micro-organisms from tsetse fly mycetomes were maintained in culture, where they were more pleomorphic than in the mycetomes, but were in some cases very similar to those observed in ovaries by other authors. Agglutination tests on the cultured forms indicated in affinity to Rickettsia. They were sensitive to antibiotics introduced by feeding flies on hosts treated with Ampicillin; this reduced the longevity and fecundity of the tsetse flies and appeared to disturb normal digestion of bloodmeals.

Agglutination Tests↗
PubMed1979

[Effect of bacterial infections and antibiotics on tsetse flies (Diptera, Glossinidae) (author's transl)].

The membrane feeding technique (in vitro feeding) used for the rearing of tsetse flies has advantages over the conventional method of feeding the flies on host animals. However, as long as blood remains the sole source of tsetse fly nutrition, the risk remains of blood being contaminated during collection, storage or feeding with bacteria pathogenic to the flies. The resulting high mortality of the tsetse flies endangers the success of this rearing. The experiments described here have shown that Glossina m. morsitans Westw. are more sensitive to Pseudomonas aeruginosa than G. p. palpalis Rob.-Desv. Rearing experiments over several years have confirmed this finding in that the latter species has never been threatened by high bacterial-induced mortality, whereas in 1973-74, due to contamination of the in vitro fed blood, a population of G. m. morsitans was difficult to colonize. The quantity of infected blood intake (14 to 70 mg) had no influence on the survival rate. However, when flies were infected once with Pseudomonas aeruginosa (dilution stage of 10(-3)), the organisms were eliminated after only nine days in living G. p. palpalis, but after 14 days in living G. m. morsitans. Females were infected at different stages of pregnancy but the same bacteria were not isolated in any puparia. Therefore, transmission of the bacteria to larvae growing in the uterus could not be demonstrated. All antibiotics used, to which bacteria isolated from tsetse flies in the laboratory were sensitive, caused a reduction in productivity. Parental females as well as females which emerged from larvae deposited by these flies (= F1-generation) 6 days after the administration of the drug to the pregnant females showed a similar loss in productivity. This corresponds with a degeneration of mesenteric symbionts. The most successful way to cope with bacterial infection in the membrane feeding technique in the rearing of tsetse flies has proved to be prophylactic measures, i.e. sterile membranes, sterile underlying aluminium trays and sterile blood. The methods employed at this laboratory, where up to 20 000 flies are being fed daily through membranes, have prevented dangerous bacterial infections in both species.

Animals↗
PubMed1979

Tsetse fly reactions to light and humidity gradients.

Tsetse flies are positively phototactic below about 30 degree C and negatively phototactic above it. The flies show a preference for the wet end of a humidity gradient and the bright end of a dorsal light intensity gradient. Studies of activity levels indicate that tsetse flies should aggregate in damp situations where the activity levels is minimal, whereas in practice the flies are distributed throughout the whole of gradient. Analyses of the water and fat content of experimental flies indicates that the reactions of individual flies is determined by their physiological condition and the conditions under which the flies have previously been kept. Previous ecological studies on the reactions of flies to humidity and light stimuli need to be reassessed in the light of these findings.

Animals↗
PubMed1992

Proline transport by tsetse fly Glossina morsitans flight muscle mitochondria.

1. Proline accumulation by tsetse fly Glossina morsitans flight muscle mitochondria was studied in vitro by the swelling technique and direct measurement of (U-14C) proline. 2. Proline transport was inhibited by the uncharged liposoluble -SH reagent, N-ethylmaleimide but not by ionic reagent, mersalyl, suggesting that the -SH groups involved in the transport of proline are located in a hydrophobic part of the membrane or on the matrix side of the membrane. 3. The kinetic study of proline accumulation revealed saturation kinetics and a high temperature dependence. It gave a Km of 85 microM and a Vmax of 962 pmol/min/mg protein and an activation energy (Ea) of 11 kcal/mol. 4. Certain other amino acids (L-valine, L-alanine, L-methionine, L-phenylalanine, L-tryptophan and L-hydroxyproline) significantly stimulated proline uptake. 5. These observations indicate that tsetse fly Glossina morsitans flight muscle mitochondria contain a proline transport mechanism.

Adenosine Diphosphate↗
PubMed1977

Lethal effect of tetracycline on tsetse flies following damage to bacterioid symbionts.

High mortality was observed in tsetse flies, Glossina morsitans morsitans, that had had a single blood meal on rabbits which had previously been administered tetracycline complex salts. The death of the flies was apparently effected by the killing of the fly symbionts and the destruction of the mycetomes of the gut. It is suggested that tetracycline complex salts in the food or drink of livestock may be tried for the control of tsetse flies.

Animals↗
PubMed1975

Salivary secretion in three species of tsetse flies (Glossinidae).

The study of the mechanism and process of salivation in tsetse flies is of paramount importance towards a fuller understanding of the transmission of trypanosomiasis and nagana diseases. Gordon, Crewe and Willett (1956) made direct observations, through a microscope, of the haustellum of G. morsitans as it penetrated into the ear of an anesthetised mouse and found that probing was accompanied by a copious but intermittent ejection of saliva from the hypopharynx. The outpouring of the saliva commenced during penetration of the stratum corneum and was maintained throughout probing of the tissues. During engorgement, blood is taken in through the labium while saliva was discharged from the hypopharynx at the same time. Besides this work, very little else seems to have been done on the salivary secretion by tsetse flies especially in relation to the hunger cycle of the fly and to the species of tsetse. These aspects were studied on three important species of tsetse and are reported upon in this paper.

Animals↗
PubMed1979

Serratia marcescens as a pathogen of tsetse flies.

When applied to the ears of rabbits used as hosts for tsetse flies, the bacterium Serratia marcescens produced significant mortality in populations of Glossina m. morsitans and G. pallidipes. After being ingested during the blood meal, cells of S. Marcescens multiplied in the intestine of the flies and entered the hemocoel. Using the brush method of applying the bacterium, 100% mortality of both Glossina species occurred within 10 days after application. In newly killed flies, the bacteria could be found free in the hemocoel as well as in the fat body and blood cells. The supernatant of a liquid culture of S. marcescens did not produce fly mortality when applied to rabbit ears. The results indicate that S. marcescens is able to invade the hemocoel of "normal" laboratory-reared tsetse flies.

Animals↗
PubMed1978

In vitro feeding in the rearing of tsetse flies (Glossina m. morsitans and G.p. palpalis, Diptera: Glossinidae).

The increasing demand for laboratory reared tsetse flies for research and biological control makes it necessary to develop effective and standardized tsetse fly feeding methods without using live animals for the daily blood uptake. The in vitro feeding technique, described in this paper, has been used for rearing G. m. morsitans by feeding them defibrinated equine blood through a silicone membrane. The results obtained for female longevity and productivity and mean weight of puparia are satisfactory. However, feeding defibrinated bovine blood results in significantly lighter puparia. A colony of G. p. palpalis feeding on defibrinated bovine blood is the only colony of this species that has been successfully maintained by in vitro feeding over several years. The survival rate of the females being fed defibrinated bovine, equine or porcine blood is equal. The number of larvae produced by females being fed defibrinated equine blood is significantly lower. Females younger than 50 days produce larvae which form a heavier puparia than females aged between 51 to 80 or 100 days, irrespective of blood source. Bovine blood used within the first 3 days after its collection leads to significantly higher mean weights of puparia than bovine blood used therafter. The increasing degree of haemolysis is most probably not the reason for this observation. A colony production model based on the performance of both species, G. m. morsitans and G. p. palpalis, fed in vitro, shows the importance of the first five age group periods (i.e. 45 to 50 days after emergence) for the overall performance of the flies. According to the results obtained, about 2,3 puparia per female are needed to maintain the same number of females in the colony. This level of production is reached in the fifth age group period. All larvae produced thereafter are available for colony expansion or experimental purposes. Rearing of both species with in vitro feeding is now a matter of routine.

Animal Feed↗
PubMed1975

Diuresis in the tsetse fly Glossina austeni.

After taking a blood meal, the tsetse fly Glossina austeni excretes the excess water and salts of the meal in approximately 30 min. During this period a volume of fluid equivalent to 80% of the unfed weight of the fly passes through the haemolymph, whose composition nevertheless remains almost constant. The fluid excreted has a higher sodium and lower potassium concentration than the haemolymph, indicating that sodium may be the prime mover in urine formation in Glossina.

Animals↗
PubMed1992

Sequential infection of tsetse flies with Trypanosoma congolense and Trypanosoma brucei.

The question whether tsetse flies can be experimentally infected with more than one trypanosome species or strain by sequential feeding was investigated using DNA probe technology to identify directly the small numbers of trypanosomes in the fly gut. Bloodstream form trypanosomes of Trypanosoma congolense or T. brucei ssp. were used for initial infection, followed by sequential feeds using either T. congolense or T. brucei ssp. Midgut trypanosome populations were subsequently analysed by hybridising dot blots with species-specific DNA probes. Two different T. brucei stocks were also fed in succession and the midgut trypanosome populations analysed by molecular karyotype. Contrary to expectations from previous reports, it was comparatively easy to superinfect flies with a second trypanosome species or stock, although the presence of trypanosomes already in the gut did not aid establishment of those incoming. Thus, to develop a mixed infection, a prerequisite for trypanosome mating, flies do not necessarily have to pick up both parental trypanosomes on their first feed.

Animals↗
PubMed1992

Isolation and properties of 600-kDa and 23-kDa haemolymph proteins from the tsetse fly, Glossina morsitans: their possible role as biological insecticides.

The haemolymph of the tsetse fly, Glossina morsitans morsitans, contains a high (lipophorin) and a low molecular weight protein of high densities, 1.11 and 1.29 g/ml, respectively. The purification of the proteins was achieved by a combination of density gradient ultracentrifugation and reported gel permeation chromatography. The lipophorin is of high molecular weight (M(r) integral of 600,000) and consists of two apoproteins, apolipophorin I (M(r) integral of 250,000) and apolipophorin II (M(r) integral of 80,000) both of which are glycosylated. Lipophorin also has a pI of 6.1. However, electrophoresis under non-denaturing and denaturing conditions showed the low molecular weight protein to be a single polypeptide chain (M(r) integral of 23,000). Amino acid analysis revealed a relatively high content of the acidic amino acids as well as serine and glycine. The protein contained lipids as shown by Sudan Black staining but was unglycosylated. Using rabbit antiserum against the isolated protein in immunodiffusion and immunoblotting experiments, no cross-reactivity was detected with haemolymph samples from insects representing six orders. In conclusion, the finding of lipophorin suggests that, although flies primarily utilize proline for their energy needs, there is an active transport mechanism for the supply of lipid requirements. However, the results for the low molecular weight protein indicate that the protein is unique to Glossina, suggesting that it may have an important role in the physiology of this insect and is therefore a significant target for vector management.

Animals↗
PubMed1978

A microscopical study of the innervation of flight muscles in the tsetse fly.

The gross morphology of the nervous system supplying the dorsal longitudinal flight muscles of tsetse flies is described. Electron microscopical investigation of the nerves reveals that the dorsal longitudinal muscles are innervated by branches from four main axons. A detailed description of the neuromuscular junctions in the flight muscle is presented.

Animals↗
PubMed1978

Sex pheromone of the tsetse fly: isolation, identification, and synthesis of contact aphrodisiacs.

Sex pheromones isolated from the cuticle of the female tsetse fly, Glossina morsitans morsitans Westwood, release mating behavior in the male fly at ultrashort range or upon contact with baited decoys. Three active components were identified as 15,19-dimethylheptatriacontane, 17,21-dimethylheptatriacontane, and 15,19,23-trimethylheptatriacontane. Chemical and biological comparisons show that the natural and synthetic compounds are identical.

Animals↗
PubMed1975

Structural modulations in the tsetse fly milk gland during a pregnancy cycle.

Gross ultrastructural and histochemical details of the integumental milk glands of the tsetse fly Glossina morsitans have been examined during the pregnancy cycle. Structural evidence for protein secretion is found between Days 3-8 of the nine-day cycle: termination of activity is completed on the day of parturition. Onset of lactation is synchronized with the eclosion of the first instar larva. The changes in cell volume (notably in the extracellular reservoir) occurring throughout the pregnancy cycle are illustrated in electron micrographs, and a one hundred-fold volume increase in the reservoir volume between the inactive phase and the active period is illustrated and discussed in terms of membrane modulation of the limiting membrane of the reservoir. Intracellular membrane changes during the cycle, particularly the development of extensive ER arrays in the actively secreting cell, are illustrated and discussed. It is suggested that cytoplasmic microtubules play a part in maintaining the form of the distended secretory cell, at the height of secretory release and storage. Histochemical observations on the milk secretion, and the contents of the larval gut are presented.

Animals↗
PubMed1979

Cyclical transmission of Trypanosoma brucei rhodesiense and Trypanosoma congolense by tsetse flies infected with culture-form procyclic trypanosomes.

Culture procyclic forms of Trypanosoma brucei rhodesiense and Trypanosoma congolense were fed to Glossina morsitans morsitans through artificial membranes. A very high percentage of the flies so fed produced established midgut infections, a proportion of which went on to develop into mature metacyclic trypanosomes capable of infecting mammalian hosts. The method offers a safe, clean way of infecting tsetse flies with African trypanosomes which reduces the need for trypanosome-infected animals in the laboratory.

Animals↗