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Ramos FO, Leyria J, Nouzova M, Fruttero LL, Noriega FG, Canavoso LE. Juvenile hormone mediates lipid storage in the oocytes of Dipetalogaster maxima. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2021; 133:103499. [PMID: 33212190 DOI: 10.1016/j.ibmb.2020.103499] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/20/2020] [Accepted: 11/06/2020] [Indexed: 06/11/2023]
Abstract
Triatomines are vectors of Chagas disease and important model organisms in insect physiology. "Kissing bugs" are obligatory hematophagous insects. A blood meal is required to successfully complete oogenesis, a process primarily controlled by juvenile hormone (JH). We used Dipetalogaster maxima as an experimental model to further understand the roles of JH in the regulation of vitellogenesis and oogenesis. A particular focus was set on the role of JH controlling lipid and protein recruitment by the oocytes. The hemolymph titer of JH III skipped bisepoxide increased after a blood meal. Following a blood meal there were increased levels of mRNAs in the fat body for the yolk protein precursors, vitellogenin (Vg) and lipophorin (Lp), as well as of their protein products in the hemolymph; mRNAs of the Vg and Lp receptors (VgR and LpR) were concomitantly up-regulated in the ovaries. Topical administration of JH induced the expression of Lp/LpR and Vg/VgR genes, and prompted the uptake of Lp and Vg in pre-vitellogenic females. Knockdown of the expression of LpR by RNA interference in fed females did not impair the Lp-mediated lipid transfer to oocytes, suggesting that the bulk of lipid acquisition by oocytes occurred by other pathways rather than by the endocytic Lp/LpR pathway. In conclusion, our results strongly suggest that JH signaling is critical for lipid storage in oocytes, by regulating Vg and Lp gene expression in the fat body as well as by modulating the expression of LpR and VgR genes in ovaries.
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Affiliation(s)
- Fabian O Ramos
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Córdoba, Argentina.
| | - Jimena Leyria
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Córdoba, Argentina.
| | - Marcela Nouzova
- Department of Biological Sciences and Biomolecular Science Institute, Florida International University, Miami, FL, USA; Institute of Parasitology, Biology Centre CAS, Ceske Budejovice, Czech Republic.
| | - Leonardo L Fruttero
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Córdoba, Argentina.
| | - Fernando G Noriega
- Department of Biological Sciences and Biomolecular Science Institute, Florida International University, Miami, FL, USA.
| | - Lilian E Canavoso
- Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Córdoba, Argentina.
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Vieira CS, Figueiredo MB, Moraes CDS, Pereira SB, Dyson P, Mello CB, Castro DP, Azambuja P. Azadirachtin interferes with basal immunity and microbial homeostasis in the Rhodnius prolixus midgut. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2021; 114:103864. [PMID: 32918931 DOI: 10.1016/j.dci.2020.103864] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 05/08/2023]
Abstract
Rhodnius prolixus is an insect vector of two flagellate parasites, Trypanosoma rangeli and Trypanosoma cruzi, the latter being the causative agent of Chagas disease in Latin America. The R. prolixus neuroendocrine system regulates the synthesis of the steroid hormone ecdysone, which is essential for not only development and molting but also insect immunity. Knowledge for how this modulates R. prolixus midgut immune responses is essential for understanding interactions between the vector, its parasites and symbiotic microbes. In the present work, we evaluated the effects of ecdysone inhibition on R. prolixus humoral immunity and homeostasis with its microbiota, using the triterpenoid natural product, azadirachtin. Our results demonstrated that azadirachtin promoted a fast and lasting inhibitory effect on expression of both RpRelish, a nuclear factor kappa B transcription factor (NF-kB) component of the IMD pathway, and several antimicrobial peptide (AMP) genes. On the other hand, RpDorsal, encoding the equivalent NF-kB transcription factor in the Toll pathway, and the defC AMP gene were upregulated later in azadirachtin treated insects. The treatment also impacted on proliferation of Serratia marcescens, an abundant commensal bacterium. The simultaneous administration of ecdysone and azadirachtin in R. prolixus blood meals counteracted the azadirachtin effects on insect molting and also on expression of RpRelish and AMPs genes. These results support the direct involvement of ecdysone in regulation of the IMD pathway in the Rhodnius prolixus gut.
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Affiliation(s)
- Cecilia Stahl Vieira
- Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (IOC/FIOCRUZ), Rio de Janeiro, RJ, Brazil; Departamento de Entomologia Molecular, Instituto Nacional de Entomologia Molecular (INCT-EM), Rio de Janeiro, RJ, Brazil
| | - Marcela Barbosa Figueiredo
- Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (IOC/FIOCRUZ), Rio de Janeiro, RJ, Brazil
| | - Caroline da Silva Moraes
- Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (IOC/FIOCRUZ), Rio de Janeiro, RJ, Brazil
| | - Suelen Bastos Pereira
- Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (IOC/FIOCRUZ), Rio de Janeiro, RJ, Brazil
| | - Paul Dyson
- School of Medicine, Swansea University, Swansea, UK
| | - Cícero Brasileiro Mello
- Laboratório de Biologia de Insetos, Universidade Federal Fluminense, Niteroi, RJ, Brazil; Departamento de Entomologia Molecular, Instituto Nacional de Entomologia Molecular (INCT-EM), Rio de Janeiro, RJ, Brazil; Programa de Pós-Graduação Em Ciências e Biotecnologia, Universidade Federal Fluminense, Niteroi, RJ, Brazil
| | - Daniele Pereira Castro
- Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (IOC/FIOCRUZ), Rio de Janeiro, RJ, Brazil; Departamento de Entomologia Molecular, Instituto Nacional de Entomologia Molecular (INCT-EM), Rio de Janeiro, RJ, Brazil
| | - Patrícia Azambuja
- Departamento de Entomologia Molecular, Instituto Nacional de Entomologia Molecular (INCT-EM), Rio de Janeiro, RJ, Brazil; Programa de Pós-Graduação Em Ciências e Biotecnologia, Universidade Federal Fluminense, Niteroi, RJ, Brazil.
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Leyria J, Orchard I, Lange AB. What happens after a blood meal? A transcriptome analysis of the main tissues involved in egg production in Rhodnius prolixus, an insect vector of Chagas disease. PLoS Negl Trop Dis 2020; 14:e0008516. [PMID: 33057354 PMCID: PMC7591069 DOI: 10.1371/journal.pntd.0008516] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/27/2020] [Accepted: 09/23/2020] [Indexed: 12/17/2022] Open
Abstract
The blood-sucking hemipteran Rhodnius prolixus is a vector of Chagas disease, one of the most neglected tropical diseases affecting several million people, mostly in Latin America. The blood meal is an event with a high epidemiological impact since adult mated females feed several times, with each meal resulting in a bout of egg laying, and thereby the production of hundreds of offspring. By means of RNA-Sequencing (RNA-Seq) we have examined how a blood meal influences mRNA expression in the central nervous system (CNS), fat body and ovaries in order to promote egg production, focusing on tissue-specific responses under controlled nutritional conditions. We illustrate the cross talk between reproduction and a) lipids, proteins and trehalose metabolism, b) neuropeptide and neurohormonal signaling, and c) the immune system. Overall, our molecular evaluation confirms and supports previous studies and provides an invaluable molecular resource for future investigations on different tissues involved in successful reproductive events. These analyses serve as a starting point for new investigations, increasing the chances of developing novel strategies for vector population control by translational research, with less impact on the environment and more specificity for a particular organism.
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Affiliation(s)
- Jimena Leyria
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Ian Orchard
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Angela B. Lange
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
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Alzogaray RA, Zerba EN. Rhodnius prolixus intoxicated. JOURNAL OF INSECT PHYSIOLOGY 2017; 97:93-113. [PMID: 27113321 DOI: 10.1016/j.jinsphys.2016.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 04/08/2016] [Accepted: 04/20/2016] [Indexed: 06/05/2023]
Abstract
Rhodnius prolixus (Hemiptera: Reduviidae) is a hematophagous insect native from South America. By the end of the 20th century, it was one of the main vectors of Chagas disease in Venezuela, Colombia, several Central American countries and southern Mexico. The aim of the present article is to review the literature regarding R. prolixus toxicology. British entomologist Vincent B. Wigglesworth carried out the first studies on this subject over seventy years ago. A wide bibliographical search allowed to locate one hundred and thirty scientific articles describing the effects of different insecticides on R. prolixus. About one-third of these articles report the acute toxicity and/or sublethal effects produced by the main synthetic neurotoxic families of insecticides (organochlorines, organophosphates, carbamates and pyrethroids). Only a couple of these studies have regarded the toxicokinetics or toxicodynamics of these insecticides. Insect growth or development disruptors, such as juvenoids, chitin synthesis inhibitors, precocenes, azadirachtin and lignoids, have been thoroughly studied in R. prolixus. Important aspects on the mode of action of ureases were also described in this species. By the end of the 1960's, resistance to insecticides was detected in R. prolixus from Venezuela. Some years later, the existence of pyrethroid-resistant individuals was also reported. Control programmes for R. prolixus in countries where Chagas is endemic have only used synthetic neurotoxic insecticides. In 2011, Central America and southern Mexico were declared free of this insect. The recent sequencing of the R. prolixus genome will provide valuable information to understand the molecular basis of insecticide resistance in this species.
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Affiliation(s)
- Raúl A Alzogaray
- UNIDEF, CITEDEF, CONICET, CIPEIN, Villa Martelli, Argentina; Instituto de Investigación e Ingeniería Ambiental (3IA), Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.
| | - Eduardo N Zerba
- UNIDEF, CITEDEF, CONICET, CIPEIN, Villa Martelli, Argentina; Instituto de Investigación e Ingeniería Ambiental (3IA), Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina
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Mesk M, Mahdjoub T, Gourbière S, Rabinovich JE, Menu F. Invasion speeds of Triatoma dimidiata, vector of Chagas disease: An application of orthogonal polynomials method. J Theor Biol 2016; 395:126-143. [PMID: 26807809 DOI: 10.1016/j.jtbi.2016.01.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 12/12/2015] [Accepted: 01/06/2016] [Indexed: 11/18/2022]
Abstract
Demographic processes and spatial dispersal of Triatoma dimidiata, a triatomine species vector of Chagas disease, are modeled by integrodifference equations to estimate invasion capacity of this species under different ecological conditions. The application of the theory of orthogonal polynomials and the steepest descent method applied to these equations, allow a good approximation of the abundance of the adult female population and the invasion speed. We show that: (1) under the same mean conditions of demography and dispersal, periodic spatial dispersal results in an invasion speed 2.5 times larger than the invasion speed when spatial dispersal is continuous; (2) when the invasion speed of periodic spatial dispersal is correlated to adverse demographic conditions, it is 34.7% higher as compared to a periodic dispersal that is correlated to good demographic conditions. From our results we conclude, in terms of triatomine population control, that the invasive success of T. dimidiata may be most sensitive to the probability of transition from juvenile to adult stage. We discuss our main theoretical predictions in the light of observed data in different triatomines species found in the literature.
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Affiliation(s)
- Mohammed Mesk
- Laboratoire d'Analyse Non Linéaire et Mathématiques Appliquées, Université de Tlemcen, BP 119 Imama (Pôle2), Tlemcen 13000, Algeria.
| | - Tewfik Mahdjoub
- Laboratoire d'Analyse Non Linéaire et Mathématiques Appliquées, Université de Tlemcen, BP 119 Imama (Pôle2), Tlemcen 13000, Algeria.
| | - Sébastien Gourbière
- Université de Perpignan Via Domitia, EA 4218 ׳Institut de Modélisation et d׳Analyse en Géo-Environnements et Santé' (IMAGES), Perpignan 66100, France.
| | - Jorge E Rabinovich
- Centro de Estudios Parasitológicos y de Vectores, Universidad Nacional de La Plata, La Plata, Provincia de Buenos Aires, Argentina.
| | - Frédéric Menu
- Laboratoire de Biométrie et Biologie Evolutive (UMR 5558), Université de Lyon, Université Lyon 1, UMR CNRS 5558, 43 Bd du 11 Novembre 1918, 69 622 Villeurbanne Cedex, France.
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Genta FA, Souza RS, Garcia ES, Azambuja P. Phenol oxidases from Rhodnius prolixus: temporal and tissue expression pattern and regulation by ecdysone. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:1253-1259. [PMID: 20361973 DOI: 10.1016/j.jinsphys.2010.03.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 03/22/2010] [Accepted: 03/23/2010] [Indexed: 05/29/2023]
Abstract
Rhodnius prolixus 5th instar nymphs have significant PO enzymatic activity in the anterior midgut, fat body and hemolymph. The tissue with the major amount of PO activity is the anterior midgut while those with higher specific activities are the fat body and hemolymph. In this work the temporal pattern of PO enzymatic activity in different tissues was investigated. In fat body, PO peaks occur at 7, 12 and 16 days after a blood meal. In hemolymph, PO diminishes until day 7, and then recovers by day 14. In the anterior midgut tissue, PO peaks on day 9 and just before ecdysis; a similar pattern was observed in the anterior midgut contents. Some of these activities are dependent on the release of ecdysone, as feeding blood meal containing azadirachtin suppresses them and ecdysone treatment counteracts this effect. These results suggest that during the development of the 5th instar, the insect has natural regulating cycles of basal PO expression and activation, which could be related to the occurrence of natural infections. The differences in temporal patterns of activity and the effects of azadirachtin and ecdysone in each organ suggest that, at least in R. prolixus, different tissues are expressing different PO genes.
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Affiliation(s)
- F A Genta
- Oswaldo Cruz Institute, Oswaldo Cruz Foundation (FIOCRUZ), Rio de Janeiro, Brazil.
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7
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Andrade Coelho CA, de Souza NA, Feder MD, da Silva CE, Garcia EDS, Azambuja P, Gonzalez MS, Rangel EF. Effects of azadirachtin on the development and mortality of Lutzomyia longipalpis larvae (Diptera: Psychodidae: Phlebotominae). JOURNAL OF MEDICAL ENTOMOLOGY 2006; 43:262-6. [PMID: 16619609 DOI: 10.1603/0022-2585(2006)043[0262:eoaotd]2.0.co;2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The effects of azadirachtin A added to the standard diet on the development, mortality, and metamorphosis of Lutzomyia longipalpis Lutz & Neiva, 1912 were studied. Concentrations of 0.1, 1.0, and 10.0 microg of azadirachtin/mg of diet significantly increased larval mortality in comparison with nontreated insects. Concentrations 0.1 and 1.0 microg blocked the molt of larvae, which remained as third instars until the end of the experiment. The 10 microg/mg concentration resulted in greater molt inhibition. In this group, all insects stopped their development as second instars. Simultaneous addition of ecdysone (1 microg/mg) to the standard diet containing azadirachtin counteracted the effects of azadirachtin on mortality and inhibition of ecdysis. These results indicate that azadirachtin is a potent growth inhibitor of L. longipalpis.
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Affiliation(s)
- Claudia Alves Andrade Coelho
- Department of Entomology, Fundação Oswaldo Cruz, Av. Brasil, 4365, Manguinhos, Rio de Janeiro, RJ 21045-900, Brazil
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Garcia ES, Cabral MM, Schaub GA, Gottlieb OR, Azambuja P. Effects of lignoids on a hematophagous bug, Rhodnius prolixus: feeding, ecdysis and diuresis. PHYTOCHEMISTRY 2000; 55:611-616. [PMID: 11130672 DOI: 10.1016/s0031-9422(00)00228-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The effects of lignoids on feeding, ecdysis and diuresis in fourth-instar larvae of Rhodnius prolixus (Hemiptera) were investigated. Up to 100 microg/ml burchellin, podophyllotoxin, pinoresinol, sesamin, licarin A, or nordihydroguaiaretic acid (NDGA) in the diet did not induce antifeedant effects. Pinoresinol and NDGA significantly inhibited ecdysis. In experiments in vivo, burchellin and podophyllotoxin reduced the production of urine after feeding. 5-Hydroxytryptamine (5-HT), a diuretic hormone, partially counteracted this effect of burchellin. In experiments in vitro, using isolated Malpighian tubules, (i) burchellin reduced diuretic hormone levels in the hemolymph but not the amount of diuretic hormone stored in the thoracic ganglionic masses (including axons), (ii) burchellin decreased the volume of urine secreted by isolated Malpighian tubules, and (iii) 5-HT could not overcome the effect of burchellin upon the Malpighian tubules. We conclude that burchellin interfered with the release, but not with the production of diuretic hormone by the thoracic ganglionic mass or induced an antidiuretic hormone and directly affected the Malpighian tubules.
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Affiliation(s)
- E S Garcia
- Department of Biochemistry and Molecular Biology, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
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Garcia E, Gonzalez M, Azambuja P. Biological factors involving Trypanosoma cruzi life cycle in the invertebrate vector, Rhodnius prolixus. Mem Inst Oswaldo Cruz 2000; 94 Suppl 1:213-6. [PMID: 10677719 DOI: 10.1590/s0074-02761999000700033] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- E Garcia
- Departamento de Bioquímica e Biologia Molecular, Instituto Oswaldo Cruz, Rio de Janeiro, Brasil.
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Gonzalez MS, Nogueira NF, Mello CB, De Souza W, Schaub GA, Azambuja P, Garcia ES. Influence of brain and azadirachtin on Trypanosoma cruzi development in the vector, Rhodnius prolixus. Exp Parasitol 1999; 92:100-8. [PMID: 10366535 DOI: 10.1006/expr.1998.4387] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies on the effects of decapitation, head transplantation, azadirachtin, and ecdysone therapy on the ultrastructural organization of the midgut of Rhodnius prolixus, a vector of the protozoan Trypanosoma cruzi, show a distinct effect on the organization of the epithelial cells. When insects are decapitated or treated with azadirachtin, the ultrastructural organiza tion of these compartments changed significantly and drastically blocked the development of T. cruzi infection. In converse experiments, head transplantation or oral therapy with ecdysone significantly re versed the T. cruzi infectivity and reestablished the organization of the stomach and intestine in decapitated or azadirachtin-treated insects. These results indicat that a brain factor, possibly the prothoracicotropic hormone which stimulates ecdysteroid production on the prothoracic glands, may act directly or indirectly on both the midgut cell organiza tion and the intestinal microenvironment, interfering in the trypanosome survival and infection of the vector R. prolixus.
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Affiliation(s)
- M S Gonzalez
- Departamento de Biologia Geral, Instituto de Biologia, Universidade Federal Fluminense, Morro do Valonguinho SIN degrees, Niterói, RJ, CEP 24001-970, Brazil
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Kollien AH, Schaub GA. The effect of azadirachtin on Blastocrithidia triatomae and Trypanosoma cruzi in Triatoma infestans (Insecta, Hemiptera). Int J Parasitol 1999; 29:403-14. [PMID: 10333323 DOI: 10.1016/s0020-7519(98)00219-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effect of azadirachtin on Blastocrithidia triatomae and Trypanosoma cruzi, which colonise the intestinal tract of the blood-sucking bug Triatoma infestans, was investigated. In established infections of controls without azadirachtin treatment, the small intestine of fifth-instar T. infestans contained up to 7 x l0(6) B. triatomae and the rectum 3 x 10(6). In comparison to this homoxenous flagellate, the population densities of T. cruzi in the respective regions were 99.3 and 76% lower. Treatment with azadirachtin (1 microg ml(-1)) via a blood meal and a concurrent infection with B. triatomae resulted in an increase of the population density (3 weeks p.i.), caused mainly by the mastigote stages in the rectum. In an established B. triatomae infection (12 weeks p.i.), feeding of azadirachtin did not affect the population density and composition. In an optimal T. cruzi-vector system, i.e. parasite and bug originate from the same locality, the treatment with azadirachtin at 20 weeks p.i. strongly reduced the population density in the small intestine of all bugs up to 100 days after treatment, but only in a minor percentage of the bugs in the rectum. Trypanosoma (cruzi incubated for up to 24 h in faeces of azadirachtin-treated bugs were not affected, indicating that the rectum of these bugs contained no toxic substances. The importance of these findings is that investigations of the mechanisms of action of azadirachtin offer a possibility to identify vector-derived compounds, which are necessary for the development of T. cruzi, thereby, giving us a possible new strategy to combat Chagas' disease.
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Affiliation(s)
- A H Kollien
- Department of Special Zoology, Ruhr-University, Bochum, Germany
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Garcia ES, Azambuja P, de Souza W, Feder D, Nogueira NF, Gonzalez MS. Role of the head in the ultrastructural midgut organization in Rhodnius prolixus larvae: evidence from head transplantation experiments and ecdysone therapy. JOURNAL OF INSECT PHYSIOLOGY 1998; 44:553-560. [PMID: 12769937 DOI: 10.1016/s0022-1910(98)00048-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Studies on the effects of decapitation, head transplantation and ecdysone therapy on the ultrastructural organization of the midgut in 5th-instar larvae of Rhodnius prolixus, were carried out. Control insects had a typical and significant organization of the epithelial cells (mainly microvilli, extracellular membrane layers and basal portion of the epithelial cells) of the midgut (stomach and intestine) during the entire period of the experiment. However, the host larvae, when decapitated 1 day after feeding, demonstrated significant changes in the ultrastructural organization of the epithelial cells of these compartments. In converse experiments, head transplantations from untreated donors 4-5 days after feeding into headless larvae sustained the ultrastructural organization of the epithelial cells in the midgut. Oral therapy with ecdysone (5 &mgr;g/mL of blood meal) in decapitated insects significantly reversed the altered organization of the stomach and intestine. These results point to a brain factor, possibly the prothoracicotropic hormone (PTTH) which stimulates ecdysteroid production in the prothoracic glands, may be a factor responsible, directly or indirectly, for the midgut cell organization in R. prolixus.
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Affiliation(s)
- E S. Garcia
- Department of Biochemistry and Molecular Biology, Fundação Oswaldo Cruz, Av. Brasil 4365, Castel Mourisco-5o Andar, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil
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