RESUMO
Triatoma infestans (Klug) is an insect recognized as not only an important vector of South American trypanosomiasis (Chagas disease) but also a model of specific cellular morphofunctional organization and epigenetic characteristics. The purpose of the present review is to highlight certain cellular processes that are particularly unveiled in T. infestans, such as the following: (1) somatic polyploidy involving nuclear and cell fusions that generate giant nuclei; (2) diversification of nuclear phenotypes in the Malpighian tubules during insect development; (3) heterochromatin compartmentalization into large bodies with specific spatial distribution and presumed mobility in the cell nuclei; (4) chromatin remodeling and co-occurrence of necrosis and apoptosis in the Malpighian tubules under stress conditions; (5) epigenetic markers; and (6) response of heterochromatin to valproic acid, an epidrug that inhibits histone deacetylases and induces DNA demethylation in other cell systems. These cellular processes and epigenetic characteristics emphasize the role of T. infestans as an attractive model for cellular research. A limitation of these studies is the availability of insect supply by accredited insectaries. For studies that require the injection of drugs, the operator's dexterity to perform insect manipulation is necessary, especially if young nymphs are used. For studies involving in vitro cultivation of insect organs, the culture medium should be carefully selected to avoid inconsistent results.
RESUMO
Fipronil has been widely used in agriculture and forestry in Brazil to control several pests. However, this insecticide may be hazardous to non-target organisms, including stingless bees, which are essential pollinators of crops and natural environments. Here, we investigated the effect of 24-h acute oral exposure to LC50 of fipronil on the Malpighian tubules of the stingless bee Partamona helleri (Friese). Insecticide exposure decreases the respiration rate of forager bees, and the Malpighian tubules are severely affected, as shown by the epithelial architecture disorganization, loss of cytoplasmic content, degradation of the brush border, and nuclear pyknosis. In addition, fipronil ingestion increases the number of Malpighian cells positive for peroxidase, LC3, cleaved caspase-3, and JNK. However, Notch and ERK1/2-positive cells decrease in the exposed bees. These changes in the signaling proteins indicate an increase in oxidative stress, autophagy and apoptosis, and impairment of cell recovery. Overall, our results demonstrate the toxicological effects of fipronil on a stingless bee, which compromises the physiology of this important pollinator.
Assuntos
Himenópteros , Inseticidas , Abelhas , Animais , Inseticidas/toxicidade , Túbulos de Malpighi , RespiraçãoRESUMO
Thiamethoxam is a neonicotinoid that has been used to control insect pests. The literature reports a few behavioral studies evaluating the toxic effect of thiamethoxam in ants; however, there are scarce studies at the cellular level. The present research evaluated the effects of thiamethoxam in labial (LG) and mandibular glands (MG), fat bodies (FB), and Malpighian tubules (MT) of workers of Atta sexdens, using transmission electron microscopy. The duct and secretory cells of LG were profoundly affected, then the production of saliva can be compromised, as well as its quality and subsequent use. In MG, reservoir and canaliculi cells presented slight alterations; however, MG secretory cells presented vacuoles containing lamellar structures, increased lipid production, and a large amount of mitochondria, which may lead to organ's malfunctioning. The FB cell alterations do not seem enough to cause significant changes that lead to cell death. Prominent changes in MT, such as loss of the electron-dense concentric ring, increased smooth endoplasmic reticulum, loss of basal infolds, vacuoles containing mineralized granules, and lamellar structures associated with mitochondria, suggest that their excretory function is compromised. In conclusion, thiamethoxam acts not only in the nervous system but also contributes to systemic toxicity on the target organism.
Assuntos
Formigas , Corpo Adiposo , Glândulas Salivares , Tiametoxam , Animais , Corpo Adiposo/efeitos dos fármacos , Corpo Adiposo/ultraestrutura , Inseticidas , Microscopia Eletrônica de Transmissão , Mitocôndrias , Saliva , Glândulas Salivares/efeitos dos fármacos , Glândulas Salivares/ultraestruturaRESUMO
Given that hematophagous insects ingest large quantities of blood in a single meal, they must undergo a rapid post-prandial diuresis in order to maintain homeostasis. In the kissing bug Rhodnius prolixus (Hemiptera: Reduviidae), the coordinated activity of the Malpighian tubules and anterior midgut maintains water and ion balance during the post-prandial diuresis. Three to four hours after the meal, the diuretic process finishes, and the animal enters an antidiuretic state to ensure water conservation until the next blood intake. The diuretic and antidiuretic processes are tightly regulated by serotonin and neuropeptides in this insect. In the present work, we report that the neuropeptide precursor CCHamide2 is involved in the regulation of the post-prandial diuresis in R. prolixus Our results suggest a dual effect of RhoprCCHamide2 peptide, enhancing the serotonin-induced secretion by Malpighian tubules, and inhibiting serotonin-induced absorption across the anterior midgut. To our knowledge, this is the first report of a hormone presenting opposite effects in the two osmoregulatory organs (i.e. midgut and Malpighian tubules) in insects, probably reflecting the importance of a well-tuned diuretic process in hematophagous insects during different moments after the blood meal.
Assuntos
Diurese , Proteínas de Insetos/metabolismo , Insetos Vetores/fisiologia , Neuropeptídeos/metabolismo , Rhodnius/fisiologia , Animais , Doença de Chagas , Túbulos de Malpighi/fisiologiaRESUMO
Recently, ureases were included in the arsenal of plant defense proteins, alongside many other proteins with biotechnological potential such as insecticides. Isoforms of Canavalia ensiformis urease (canatoxin-CNTX and jack bean urease-JBURE-I) are toxic to insects of different orders. This toxicity is due in part to the release of a 10 kDa peptide from the native protein, by cathepsin-like enzymes present in the insect digestive tract. The entomotoxic peptide, Jaburetox-2Ec, exhibits potent insecticidal activity against several insects, including many resistant to the native ureases. JBURE-I and Jaburetox-2Ec cause major alterations of post-feeding physiological processes in insects, which contribute to, or can be the cause of, their entomotoxic effect. An overview of the current knowledge on plant urease processing and mechanisms of action in insects is presented in this review.
Assuntos
Canavalia/enzimologia , Inseticidas/metabolismo , Controle Biológico de Vetores , Proteínas de Plantas/metabolismo , Toxinas Biológicas/metabolismo , Urease/metabolismo , Animais , Insetos/efeitos dos fármacos , Insetos/fisiologia , Inseticidas/toxicidade , Estágios do Ciclo de Vida/efeitos dos fármacos , Proteínas de Plantas/toxicidade , Isoformas de Proteínas , Toxinas Biológicas/toxicidade , Urease/toxicidadeRESUMO
Bees are important pollinators that, because of extensive deforestation of their natural habitats, now forage widely in agricultural areas. This interaction with human agricultural activity has led to a reduction in the number of bee species because of contact with widely used pesticides. However, little is known about the adverse effects that exposure to such agents has on bee tissues and organs. In this review, we discuss the morphological alterations induced by environmental contaminants in the midgut and Malpighian tubules of bees; these two organs are involved in the absorption and excretion of toxic compounds, respectively. We also discuss the role of heat shock proteins, also known as stress proteins, in the cellular response to chemical compounds, and the importance of cell death as an indicator of the toxicity of these compounds. The analysis of these two cellular markers may be useful for monitoring bees that forage in agricultural areas.
Assuntos
Animais , Glândulas Salivares/fisiologia , Proteínas de Choque Térmico , Proteínas de Choque Térmico/intoxicação , Glândulas Salivares , Túbulos de Malpighi/citologia , Abelhas , Morte Celular , Praguicidas/toxicidadeRESUMO
Whole-mounted Malpighian tubules of larvae from two meliponid bee species fixed in acetic acid-ethanol showed apositive cytoplasmic staining with Schiff reagent when submitted to the Feulgen reaction in which acid hydrolysiswas done in 4 M HCl at room temperature. The ability of various treatments applied before the Feulgen acid hydrolysisto abolish this cytoplasmic staining was examined. The aldehyde groups of phospholipids present in the cytoplasm ofthe Malpighian tubules were blocked or removed by sequential treatment with 5% sodium borohydride and acetonechloroform(1:1, v/v) for 15 min each prior to HCl hydrolysis. This treatment is recommended in order to abolish thecytoplasmic (plasmal) reaction and to allow the reliable quantification of DNA by the Feulgen reaction and thediscrimination of nuclear phenotypes in the Malpighian tubules of meliponid bees.