Shallow slow earthquakes to decipher future catastrophic earthquakes in the Guerrero seismic gap.

The Guerrero seismic gap is presumed to be a major source of seismic and tsunami hazard along the Mexican subduction zone. Until recently, there were limited observations at the shallow portion of the plate interface offshore Guerrero, so we deployed instruments there to better characterize the extent of the seismogenic zone. Here we report the discovery of episodic shallow tremors and potential slow slip events in Guerrero offshore. Their distribution, together with that of repeating earthquakes, seismicity, residual gravity and bathymetry, suggest that a portion of the shallow plate interface in the gap undergoes stable slip. This mechanical condition may not only explain the long return period of large earthquakes inside the gap, but also reveals why the rupture from past M < 8 earthquakes on adjacent megathrust segments did not propagate into the gap to result in much larger events. However, dynamic rupture effects could drive one of these nearby earthquakes to break through the entire Guerrero seismic gap.

In search of the grail: A race for acid suppression. / La búsqueda del Grial: una carrera por la supresión ácida.

Proton pump inhibitors are the reference standards for the treatment of acid-related diseases. Acid suppression in gastroesophageal reflux disease is associated with a high rate of mucosal cicatrization, but symptom response differs among endoscopic phenotypes. Extraesophageal manifestations have a good clinical response in patients that present with abnormal acid exposure (diagnostic test) in the esophagus. Proton pump inhibitors have shown their effectiveness for reducing symptom intensity in nighttime reflux and sleep disorders, improving quality of life and work productivity. That can sometimes be achieved through dose modifications by splitting or increasing the dose, or through galenic formulation. Proton pump inhibitors are not exempt from controversial aspects related to associated adverse events. Technological development is directed at improving proton pump inhibitor performance through increasing the half-life, maximum concentration, and area under the curve of the plasma concentrations through galenic formulation, as well as creating safer and more tolerable drugs. The present review is focused on the mechanisms of action, pharmacokinetic properties, and technological advances for increasing the pharmacologic performance of a proton pump inhibitor.

Systematic alphanumeric-coded endoscopy versus chromoendoscopy for the detection of precancerous gastric lesions and early gastric cancer in subjects at average risk for gastric cancer. / Aplicación de la endoscopia sistemática alfanumérica codificada más cromoendoscopia para la detección de lesiones precancerosas gástricas y cáncer gástrico temprano en sujetos con riesgo promedio de cáncer gástrico.

INTRODUCTION AND AIMS: Gastric cancer is one of the main causes of cancer worldwide, but there is currently no global screening strategy for the disease. Endoscopy is the screening method of choice in some Asian countries, but no standardized technique has been recognized. Systematic alphanumeric-coded endoscopy can increase gastric lesion detection. The aim of the present article was to compare the usefulness of systematic alphanumeric-coded endoscopy with conventional endoscopy for the detection of premalignant lesions and early gastric cancer in subjects at average risk for gastric cancer. MATERIALS AND METHODS: A cross-sectional, comparative, prospective, randomized study was conducted on patients at average risk for gastric cancer (40-50 years of age, no history of H. pylori infection, intestinal metaplasia, gastric atrophy, or gastrointestinal surgery). Before undergoing endoscopy, the patients had gastric preparation (200mg of oral acetylcysteine or 50mg of oral dimethicone). Conventional chromoendoscopy was performed with indigo carmine dye for contrast enhancement. RESULTS: Fifty consecutive cases (mean age 44.4 ± 3.34 years, 60% women, BMI 27.6 ± 5.82 kg/m2) were evaluated. Endoscopic imaging quality was satisfactory in all the cases, with no differences between methods (p = 0.817). The detection rate of premalignant lesions and early gastric cancer was 14% (6 cases of intestinal metaplasia and one case of gastric adenocarcinoma). Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 100, 95, 80, 100 and 96%, respectively, for systematic alphanumeric-coded endoscopy, and 100, 45, 20, 100, and 52%, respectively, for conventional endoscopy. Lesion detection through systematic alphanumeric-coded endoscopy was superior to that of conventional endoscopy (p = 0.003; OR = 12). CONCLUSION: Both techniques were effective, but systematic alphanumeric-coded endoscopy significantly reduced the false positive rate.

Efficacy of narrow-band imaging for detecting intestinal metaplasia in adult patients with symptoms of dyspepsia. / La eficacia de la imagen de banda estrecha para la detección de metaplasia intestinal en pacientes adultos con síntomas de dispepsia.

INTRODUCTION AND OBJECTIVE: Atrophy and intestinal metaplasia are early phenotypic markers in gastric carcinogenesis. White light endoscopy does not allow direct biopsy of intestinal metaplasia due to a lack of contrast of the mucosa. Narrow-band imaging is known to enhance the visibility of intestinal metaplasia, to reduce sampling error, and to increase the diagnostic yield of endoscopy for intestinal metaplasia in Asian patients. The aim of our study was to validate the diagnostic performance of narrow-band imaging using 1.5× electronic zoom endoscopy (with no high magnification) to diagnose intestinal metaplasia in Mexican patients. MATERIALS AND METHODS: A retrospective cohort study was conducted on consecutive patients with dyspeptic symptoms at a private endoscopy center within the time frame of January 2015 to December 2016. RESULTS: A total of 338 patients (63±8.4 years of age, 40% women) were enrolled. The prevalence of H. pylori infection was 10.9% and the incidence of intestinal metaplasia in the gastric antrum and corpus was 23.9 and 5.9%, respectively. Among the patients with intestinal metaplasia, 65.3% had the incomplete type, 42.7% had multifocal disease, and one third had extension to the gastric corpus. Two patients had low-grade dysplasia. The sensitivity of white light endoscopy was 71.2%, with a false negative rate of 9.9%. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of narrow-band imaging (with a positive light blue crest) were 85, 98, 86.8, 97.7, and 87.2%, respectively. CONCLUSION: The prevalence of H. pylori infection and intestinal metaplasia in dyspeptic Mexican patients was not high. Through the assessment of the microsurface structure and light blue crest sign, non-optical zoom narrow-band imaging had high predictive values for detecting intestinal metaplasia in patients from a general Western setting.

Post-fundoplication symptoms and complications: Diagnostic approach and treatment. / Síntomas y complicaciones posfunduplicatura: abordaje diagnóstico y tratamiento.

Laparoscopic Nissen fundoplication is currently considered the surgical treatment of choice for gastroesophageal reflux disease (GERD) and its long-term effectiveness is above 90%. Adequate patient selection and the experience of the surgeon are among the predictive factors of good clinical response. However, there can be new, persistent, and recurrent symptoms after the antireflux procedure in up to 30% of the cases. There are numerous causes, but in general, they are due to one or more anatomic abnormalities and esophageal and gastric function alterations. When there are persistent symptoms after the surgical procedure, the surgery should be described as "failed". In the case of a patient that initially manifests symptom control, but the symptoms then reappear, the term "dysfunction" could be used. When symptoms worsen, or when symptoms or clinical situations appear that did not exist before the surgery, this should be considered a "complication". Postoperative dysphagia and dyspeptic symptoms are very frequent and require an integrated approach to determine the best possible treatment. This review details the pathophysiologic aspects, diagnostic approach, and treatment of the symptoms and complications after fundoplication for the management of GERD.

Rhodnius prolixus: from physiology by Wigglesworth to recent studies of immune system modulation by Trypanosoma cruzi and Trypanosoma rangeli.

This review is dedicated to the memory of Professor Sir Vincent B. Wigglesworth (VW) in recognition of his many pioneering contributions to insect physiology which, even today, form the basis of modern-day research in this field. Insects not only make vital contributions to our everyday lives by their roles in pollination, balancing eco-systems and provision of honey and silk products, but they are also outstanding models for studying the pathogenicity of microorganisms and the functioning of innate immunity in humans. In this overview, the immune system of the triatomine bug, Rhodnius prolixus, is considered which is most appropriate to this dedication as this insect species was the favourite subject of VW's research. Herein are described recent developments in knowledge of the functioning of the R. prolixus immune system. Thus, the roles of the cellular defences, such as phagocytosis and nodule formation, as well as the role of eicosanoids, ecdysone, antimicrobial peptides, reactive oxygen and nitrogen radicals, and the gut microbiota in the immune response of R. prolixus are described. The details of many of these were unknown to VW although his work gives indications of his awareness of the importance to R. prolixus of cellular immunity, antibacterial activity, prophenoloxidase and the gut microbiota. This description of R. prolixus immunity forms a backdrop to studies on the interaction of the parasitic flagellates, Trypanosoma cruzi and Trypanosoma rangeli, with the host defences of this important insect vector. These parasites remarkably utilize different strategies to avoid/modulate the triatomine immune response in order to survive in the extremely hostile host environments present in the vector gut and haemocoel. Much recent information has also been gleaned on the remarkable diversity of the immune system in the R. prolixus gut and its interaction with trypanosome parasites. This new data is reviewed and gaps in our knowledge of R. prolixus immunity are identified as subjects for future endeavours. Finally, the publication of the T. cruzi, T. rangeli and R. prolixus genomes, together with the use of modern molecular techniques, should lead to the enhanced identification of the determinants of infection derived from both the vector and the parasites which, in turn, could form targets for new molecular-based control strategies.

Trypanosoma cruzi: effects of azadirachtin and ecdysone on the dynamic development in Rhodnius prolixus larvae.

The effects of azadirachtin and ecdysone on the Trypanosoma cruzi population in the Rhodnius prolixus gut were investigated. T. cruzi were rarely found in the gut compartments of azadirachtin-treated larvae. High parasite numbers were observed in the stomach of the control and ecdysone groups until 10 days after treatment and in the small intestine and rectum until 25 days after treatment. High percentages of round forms developed in the stomachs of all groups, whereas azadirachtin blocked the development of protozoan intermediate forms. This effect was counteracted by ecdysone therapy. In the small intestine and rectum, epimastigotes predominated for all groups, but more of their intermediates developed in the control and ecdysone groups. Azadirachtin supported the development of round forms and their intermediates into trypomastigotes. In the rectum, trypomastigotes did not develop in the azadirachtin group and developed much later after ecdysone therapy. The parallel between the effects of azadirachtin and ecdysone on the host and parasite development is discussed on the basis of the present results because ecdysone appears to act directly or indirectly in determining the synchronic development of T. cruzi forms from round to epimastigotes, but not metacyclic trypomastigotes, in the invertebrate vector.

Phenol oxidases from Rhodnius prolixus: temporal and tissue expression pattern and regulation by ecdysone.

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.

Physalin B inhibits Rhodnius prolixus hemocyte phagocytosis and microaggregation by the activation of endogenous PAF-acetyl hydrolase activities.

The effects of physalin B (a natural secosteroidal chemical from Physalis angulata, Solanaceae) on phagocytosis and microaggregation by hemocytes of 5th-instar larvae of Rhodnius prolixus were investigated. In this insect, hemocyte phagocytosis and microaggregation are known to be induced by the platelet-activating factor (PAF) or arachidonic acid (AA) and regulated by phospholipase A(2) (PLA(2)) and PAF-acetyl hydrolase (PAF-AH) activities. Phagocytic activity and formation of hemocyte microaggregates by Rhodnius hemocytes were strongly blocked by oral treatment of this insect with physalin B (1mug/mL of blood meal). The inhibition induced by physalin B was reversed for both phagocytosis and microaggregation by exogenous arachidonic acid (10microg/insect) or PAF (1microg/insect) applied by hemocelic injection. Following treatment with physalin B there were no significant alterations in PLA(2) activities, but a significant enhancement of PAF-AH was observed. These results show that physalin B inhibits hemocytic activity by depressing insect PAF analogous (iPAF) levels in hemolymph and confirm the role of PAF-AH in the cellular immune reactions in R. prolixus.

Immune depression in Rhodnius prolixus by seco-steroids, physalins.

A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (Solanaceae), on the immune reactions of R. prolixus was carried out. Ecdysis and mortality were not affected by treatment with physalins B, D, F or G (1-10 microg/ml of blood meal). R. prolixus larvae fed with blood containing physalins and inoculated with 1 microl of Enterobacter cloacae beta12 (5 x 10(3)/insect) exhibited mortality rates three times higher than controls. The insects treated with physalin B, and F (1 microg/ml) and inoculated with E. cloacae beta12 showed significant differences on lysozyme activity in the hemolymph compared to untreated insects. Furthermore, physalin D (1 microg/ml) significantly reduced the antibacterial activity. Concerning cellular immune reactions, all insects treated with physalins (1 microg/ml), exhibited drastic reductions in the quantity of yeast cell-hemocyte binding and subsequent internalization. Insects inoculated with bacteria and treated with physalins B, F and G showed reductions of microaggregate formation but physalin D did not. Physalins B and F also reduced total hemocyte count in the hemolymph. These results suggest that, in different ways, probably due to their different chemical structures, physalin B, D, F and G are immunomodulatory substances for the bloodsucking insect, R. prolixus.

Trypanosoma cruzi: attachment to perimicrovillar membrane glycoproteins of Rhodnius prolixus.

Studies were carried out to identify proteins involved in the interface of Trypanosoma cruzi with the perimicrovillar membranes (PMM) of Rhodnius prolixus. Video microscopy experiments demonstrated high level of adhesion of T. cruzi Dm 28c epimastigotes to the surface of posterior midgut cells of non-treated R. prolixus. The parasites however were unable to attach to gut cells obtained from decapitated or azadirachtin-treated insects. The influence of carbohydrates on the adhesion to insect midgut was confirmed by inhibition of parasite attachment after midgut incubation with N-acetylgalactosamine, N-acetylmannosamine, N-acetylglucosamine, D-galactose, D-mannose or sialic acid. We observed that hydrophobic proteins in the surface of epimastigotes bind to polypeptides with 47.7, 45.5, 44, 43, 40.5, 36, 31 and 13kDa from R. prolixus PMM and that pre-incubation of lectins specifically inhibited binding to 31, 40.5, 44 and 45.5kDa proteins. We suggest that glycoproteins from PMM and hydrophobic proteins from epimastigotes are important for the adhesion of the parasite to the posterior midgut cells of the vector.

Antiserum against perimicrovillar membranes and midgut tissue reduces the development of Trypanosoma cruzi in the insect vector, Rhodnius prolixus.

Antiserum raised against Rhodnius prolixus perimicrovillar membranes (PMM) and midgut tissue interfered with the midgut structural organization and reduced the development of Trypanosoma cruzi in the R. prolixus insect vector. SDS-PAGE and Western blot analyses confirmed the specific recognition of midgut proteins by the antibody. Feeding, mortality, molt, and oviposition of the insects were unaffected by feeding with the antiserum. However, the eclosion of the eggs were reduced from R. prolixus females treated with antiserum. Additionally, in vivo evaluation showed that after oral treatment with the antiserum, the intensity of infection with the Dm-28c clone of T. cruzi decreased in the digestive tract of fifth-instar nymphs and in the excretions of R. prolixus adults. These results suggest that the changes observed in the PMM organization in the posterior midgut of R. prolixus may not be important for triatomine survival but the antiserum acts as a transmission-reduction vaccine able to induce significant decreases in T. cruzi infection in the vector.

Effect of blood components, abdominal distension, and ecdysone therapy on the ultrastructural organization of posterior midgut epithelial cells and perimicrovillar membranes in Rhodnius prolixus

The effects of blood components, nerve-cord severance, and ecdysone therapy on the posterior midgut epithelial cells of 5th-instar Rhodnius prolixus nymphs 10 days after feeding were analyzed by transmission electron microscopy. Cutting the nerve-cord of the blood-fed insects partially reduced the development of microvilli and perimicrovillar membranes (PMM), and produced large vacuoles and small electrondense granules; insects fed on Ringer's saline diet exhibited well developed microvilli and low PMM production; swolled rough endoplasmatic reticulum and electrondense granules; Ringer's saline meal with ecdysone led to PMM development, glycogen particles, and several mitochondria in the cytoplasm; epithelial cells of the insects fed on Ringer's saline meal whose nerve-cord was severed showed heterogeneously distributed microvilli with reduced PMM production and a great quantity of mitochondria and glycogen in the cytoplasm; well developed microvilli and PMM were observed in nerve-cord severed insects fed on Ringer's saline meal with ecdysone; Ringer's saline diet containing hemoglobin recovered the release of PMM; and insects fed on human plasma showed slightly reduced PMM production, although the addition of ecdysone in the plasma led to a normal midgut ultrastructural organization. We suggest that the full development of microvilli and PMM in the epithelial cells depends on the abdominal distension in addition to ingestion of hemoglobin, and the release of ecdysone.

Lignoids in insects: chemical probes for the study of ecdysis, excretion and Trypanosoma cruzi-triatomine interactions.

The effects of phytochemicals (lignans and neolignans) are reviewed in a variety of insect species with special focus on the recent advances on feeding, excretion and Trypanosoma cruzi interactions with Rhodnius prolixus. Burchellin, podophyllotoxin, pinoresinol, sesamin, licarin A, and nordihydroguaiaretic acid (NDGA) added to the diet of Rhodnius prolixus larvae induce antifeedant effects only in doses up to 100 microg/ml of blood meal. Additionally, pinoresinol and NDGA significantly inhibit ecdysis (ED(50)<20 microg/ml). Simultaneous application of ecdysone (1 microg/ml) counteracts ecdysial stasis as induced by NDGA in 5th-instar larvae. Experiments in vivo demonstrate that burchellin and podophyllotoxin (100 microg/ml) diminish excretion post-feeding. Simultaneous treatment with 5-hydroxytryptamine (1 mM, 5-HT), a diuretic hormone, partially reverses this effect of burchellin. Experiments in vitro, using isolated Malpighian tubules of R. prolixus, indicate that burchellin (i) decreases diuretic hormone levels in the hemolymph but not the amount of diuretic hormone stored in the thoracic ganglionic masses (including axons); (ii) reduces the volume of urine secreted by isolated Malpighian tubules; and (iii) 5-HT therapy cannot overcome the effect of burchellin on the Malpighian tubules. In R. prolixus fed on blood containing T. cruzi epimastigotes, the number of parasites in the digestive tract decreases drastically in the presence of burchellin and NDGA (10 microg/ml). When these phytochemicals are applied 20 days after T. cruzi infection, burchellin significantly reduces the gut infection, whereas NDGA does not. However, if the insects are pretreated with both compounds 20 days before subsequent infection with epimastigotes, the parasite infection is almost completely abolished. The same holds true when 5th-instar of R. prolixus are inoculated with 0.5 microg/microl/larva of both neolignans 1 day before infection. Taken together, these findings not only provide a better understanding of the lignoid function in insects, but also offer novel insights into basic physiological processes, which make lignoids interesting candidates for new types of insecticides.

Isolation of Serratia marcescens in the midgut of Rhodnius prolixus: impact on the establishment of the parasite Trypanosoma cruzi in the vector.

The effects of resident bacteria in the stomach of 5th-instar larvae of Rhodnius prolixus on the erythrocyte lysis and Trypanosoma cruzi infection were studied. The bacteria population increased approximately 10,000-fold after feeding. Hemolysis rose to approximately 28% within 24h postfeeding and then linearly grew until day 4 attaining almost 100%. The number of surviving Y strain of T. cruzi in the stomach declined drastically, while the infection with Dm28c clone was maintained stable. Five days after feeding, few different types of bacterial colonies were obtained when stomach content suspensions were spread onto BHI agar plates. The hemolytic bacteria were isolated and identified as Serratia marcescens biotype A1a (referenced as RPH), which produces the pigment prodigiosin. In vitro experiments, comparing incubations of RPH with S. marcescens SM365, a prodigiosin pigment producer, and S. marcescens DB11, a nonpigment variant, as a control, with erythrocytes and T. cruzi demonstrated that: (i) at 30 degrees C, SM365 and RPH diminished the populations of Y strain, but not DM28c clone, and DB11 was unable to lyse both T. cruzi strains; (ii) at 0 degrees C, SM263 and RPH killed the flagellates, but DB11 did not; and (iii) all three strains of S. marcescens were able to lyse erythrocytes. These results suggest that S. marcescens trypanolytic activity from the SM365 and RPH strains is distinct from the hemolytic activity and that prodigiosin is an important factor for the trypanolytic action of the bacteria.

Effect of blood components, abdominal distension, and ecdysone therapy on the ultrastructural organization of posterior midgut epithelial cells and perimicrovillar membranes in Rhodnius prolixus.

The effects of blood components, nerve-cord severance, and ecdysone therapy on the posterior midgut epithelial cells of 5th-instar Rhodnius prolixus nymphs 10 days after feeding were analyzed by transmission electron microscopy. Cutting the nerve-cord of the blood-fed insects partially reduced the development of microvilli and perimicrovillar membranes (PMM), and produced large vacuoles and small electrondense granules; insects fed on Ringer's saline diet exhibited well developed microvilli and low PMM production; swolled rough endoplasmatic reticulum and electrondense granules; Ringer's saline meal with ecdysone led to PMM development, glycogen particles, and several mitochondria in the cytoplasm; epithelial cells of the insects fed on Ringer's saline meal whose nerve-cord was severed showed heterogeneously distributed microvilli with reduced PMM production and a great quantity of mitochondria and glycogen in the cytoplasm; well developed microvilli and PMM were observed in nerve-cord severed insects fed on Ringer's saline meal with ecdysone; Ringer's saline diet containing hemoglobin recovered the release of PMM; and insects fed on human plasma showed slightly reduced PMM production, although the addition of ecdysone in the plasma led to a normal midgut ultrastructural organization. We suggest that the full development of microvilli and PMM in the epithelial cells depends on the abdominal distension in addition to ingestion of hemoglobin, and the release of ecdysone.

In vivo and in vitro metacyclogenesis tests of two strains of Trypanosoma cruzi in the triatomine vectors Triatoma pseudomaculata and Rhodnius neglectus: short/long-term and comparative study.

Metacyclogenesis of Trypanosoma cruzi of the Y and Berenice strains was studied in Triatoma pseudomaculata and Rhodnius neglectus. Results in vivo showed a higher production of metacyclic trypomastigotes in R. neglectus' digestive tube than in T. pseudomaculata. In vitro experiments were also carried out in order to compare the behavior of culture forms of T. cruzi incubated in extracts of different compartments (stomach, intestine, and rectum) of the digestive tract of both species of triatomines. A higher percentage of metacyclic trypomastigotes for both parasite strains, Y and Berenice, was detected in the rectum extract of R. neglectus in comparison to that from T. pseudomaculata. The same results were obtained with in vitro experiments, using parasites incubated in urine from each of those vectors. The adhesion of parasites to the incubated rectum epithelial cells was also compared. In incubations with the Y strain no significant differences were detected between the two triatomine species but, however, with the Berenice strain the mean percentage of cells with adhered parasites was higher in R. neglectus than in T. pseudomaculata.

Suppression of the prophenoloxidase system in Rhodnius prolixus orally infected with Trypanosoma rangeli.

Investigations were carried out to compare aspects of the prophenoloxidase (proPO)-activating pathway in Rhodnius prolixus hemolymph in response to oral infection and inoculation of the insects with two developmental forms of Trypanosoma rangeli epimastigotes strain H14. In vivo experiments demonstrated that in control insects fed on uninfected blood, inoculation challenge with short epimastigotes resulted in high phenoloxidase (PO) activity. In contrast, previous feeding on blood containing either short or long epimastigotes was able to suppress the proPO activation induced by thoracic inoculation of the short forms. In vitro assays in the presence of short epimastigotes demonstrated that control hemolymph or hemolymph provided by insects previously fed on blood containing epimastigotes incubated with fat body homogenates from control insects significantly increased the PO activity. However, fat body homogenates from insects previously fed on blood containing epimastigotes, incubated with hemolymph taken from insects fed on control blood or blood infected with epimastigotes, drastically reduced the proPO activation. The proteolytic activity in the fat body homogenates of control insects was significantly higher than in those obtained from fat body extracts of insects previously fed on blood containing epimastigotes. These findings indicate that the reduction of the proteolytic activities in the fat body from insects fed on infected blood no longer allows a significant response of the proPO system against parasite challenge. It also provides a better understanding of T. rangeli infection in the vector and offer novel insights into basic immune processes in their invertebrate hosts.

Effects of gamma irradiation on the development of Trypanosoma rangeli in the vector Rhodnius prolixus.

Studies on the effects of gamma radiation on the infectivity of Trypanosoma rangeli (strain H14) for the vector Rhodnius prolixus revealed that (i) the LD(50) (lethal dose for 50% of bugs) for uninfected insects was 4147 rads; (ii) irradiated insects with a dose of 1200 rads subsequently infected with the flagellates exhibited a mortality of 45%, while uninfected irradiated insects showed a mortality of 5%, and infected nonirradiated insects exhibited 10% mortality; (iii) flagellates were present in the hemolymph of irradiated insects 7 days postinfection (p.i.), while in nonirradiated insects the parasites appeared in the hemocoel 18 days p.i.; (iv) T. rangeli infection decreased the number of hemocytes significantly and induced the formation of nodules in the hemolymph of both irradiated and nonirradiated insects; and (v) gamma irradiation affected the ultrastructural organization of the epithelial cells of the small intestine, principally the perimicrovillar membranes and microvilli. In this paper, we discuss the significance of the intestinal microenvironment of R. prolixus with regard to its interaction with T. rangeli.

Dynamic development of Trypanosoma cruzi in Rhodnius prolixus: role of decapitation and ecdysone therapy.

Decapitation and ecdysone therapy on the population dynamics of the Trypanosoma cruzi Dm28c clone in the stomach, small intestine and rectum of fifth-instar larvae of Rhodnius prolixus were investigated. Parasites were not found in the small intestine and rectum of decapitated insects after 10 days post-infection (p.i.). Decapitated ecdysone-supplemented insects sustained the flagellate infection in both gut compartments. In the rectum, the population density of parasites increased 5-fold in ecdysone-treated decapitated larvae and 7-fold in control insects. Epimastigote forms dominated with 40-65%, intermediate stages and round forms varied over 10-35% in the stomach, small intestine and rectum in both insect groups. Low numbers of metacyclic trypomastigotes were observed in the stomach and small intestine of the control group and decapitated insects supplemented with ecdysone but, at 15 days p.i., this form of flagellate reached about 20% in the rectum of the control insects. In the entire gut, at 30 days p.i., 23% of parasites in the control group and 8% in the decapitated insects treated with ecdysone were found. These results indicate that a head factor, possibly the prothoracicotropic hormone from the brain which stimulates ecdysone production by the prothoracic glands, may act directly or indirectly to stimulate the development of epimastigotes and round forms of the parasite and that a single ecdysone treatment is not able to fully reverse metacyclogenesis in decapitated R. prolixus.