cAMP: A second messenger involved in the mechanism of midgut alkalinization in Lutzomyia longipalpis.

The sand fly Lutzomyia longipalpis is the main vector of Leishmania infantum in the Americas. Female sand flies ingest sugar-rich solutions and blood, which are digested in the midgut. Digestion of nutrients is an essential function performed by digestive enzymes, which require appropriate physiological conditions. One of the main aspects that influence enzymatic activity is the gut pH, which must be tightly controlled. Considering second messengers are frequently involved in the coordination of tightly regulated physiological events, we investigated if the second messenger cAMP would participate in the process of alkalinization in the abdominal midgut of female L. longipalpis. In midguts containing the indicator dye bromothymol-blue, cAMP stimulated the alkalinization of the midgut lumen. Through another technique based on the use of fluorescein as a pH indicator, we propose that cAMP is involved in the alkalinization of the midgut by activating HCO3- transport from the enterocyte's cytoplasm to the lumen. The results strongly suggested that the carrier responsible for this process would be a HCO3- /Cl- antiporter located in the enterocytes' apical membrane. Hematophagy promotes the release of alkalinizing hormones in the hemolymph; however, when the enzyme adenylyl cyclase, responsible for cAMP production, was inhibited, we observed that the hemolymph from blood-fed L. longipalpis' females did not stimulate midgut alkalinization. This result indicated that hormone-stimulated alkalinization is mediated by cAMP. In the present study, we provide evidences that cAMP has a key role in the control of intestinal pH.

The role of LuloPAT amino acid/proton symporters in midgut alkalinization in the sandfly Lutzomyia longipalpis (Diptera - Psychodidae).

In Lutzomyia longipalpis females, which are the main vectors of Leishmania infantum in the Americas, hematophagy is crucial for ovary development. The control of pH in the midgut during blood digestion is important to the functioning of the digestive enzymes, which release amino acids in the luminal compartment that are then transported through the enterocytes to the hemolymph for delivery to the ovary and other organs. In the present work, we investigated transport systems known as LuloPATs that are present in the midgut of L. longipalpis but not in other organs. These transporters achieve symport of amino acids with H+ ions, and one of them (LuloPAT1) is orthologous to a transporter described in Aedes aegypti. According to our results, the transcription levels of LuloPAT1 increased significantly immediately after a blood meal. Based on the variation of the fluorescence of fluorescein with the pH of the medium, we developed a technique that shows the acidification of the cytoplasm of gut cells when amino acids are cotransported with H+ from the lumen into the enterocytes. In our experiments, the midguts of the sandflies were dissected and opened longitudinally so that added amino acids could enter the enterocytes via the lumen (PAT carriers are apical). LuloPAT1 transporters are part of a complex of mechanisms that act synergistically to promote gut alkalinization as soon as blood intake by the vector occurs. In dissected but not longitudinally opened midguts, added amino acids could only enter through the basolateral region of enterocytes. However, alkalinization of the lumen was observed because the entry of some amino acids into the cytoplasm of enterocytes triggers a luminal alkalinization mechanism independent of LuloPATs. These findings provide new perspectives that will enable the characterization of the set of signaling pathways involved in pH regulation within the L. longipalpis midgut.

Evaluation of disinfectants in order to eliminate fungal contamination in computer keyboards of an integrated health center in Piauí, Brazil.

This quantitative and qualitative study aimed to evaluate the level of fungal contamination in computer keyboards from an Integrated Health Center (IHC) at Piauí, Brazil, and to evaluate the efficacy of 50% sodium bicarbonate and 50% alcoholic vinegar solutions to eliminate these microorganisms. Ten keyboards from six sectors of the IHC were chosen randomly, and the collection was performed in three situations: (i) before of disinfection, (ii) after disinfection with solution of sodium bicarbonate, and (iii) after disinfection with solution of alcoholic vinegar. Samples were inoculated in Petri dishes with dextrose agar potato plus chloramphenicol and incubated at room temperature for 72 h. All keyboards were contaminated with opportunistic fungi, with Cladosporium cladosporioides (29.4%) being the most frequent species, followed by Curvularia lunata (17.6%) and Aspergillus niger, Alternaria alternata, and Curvularia clavata with 11.8% each. The two solutions were proven to be efficient in eliminating fungal contamination; however, the sodium bicarbonate solution caused esthetic damages in keyboards. In addition, this study is the first report of the antifungal activity of alcoholic vinegar in filamentous fungi. Based on our findings, we suggest a daily disinfection of keyboards with a 50% vinegar solution plus adequate hygiene from the hands of professionals before and after the use of the computer and its annexes, as key actions to reduce nosocomial infections, particularly in economically disadvantaged countries.

pH control in the midgut of Aedesaegypti under different nutritional conditions.

Aedes aegypti is one of the most important disease vectors in the world. Because their gut is the first site of interaction with pathogens, it is important to understand A. aegypti gut physiology. In this study, we investigated the mechanisms of pH control in the midgut of A. aegypti females under different nutritional conditions. We found that unfed females have an acidic midgut (pH âˆ¼6). The midgut of unfed insects is actively maintained at pH 6 regardless of the ingestion of either alkaline or acidic buffered solutions. V-ATPases are responsible for acidification after ingestion of alkaline solutions. In blood-fed females, the abdominal midgut becomes alkaline (pH 7.54), and the luminal pH decreases slightly throughout blood digestion. Only ingested proteins were able to trigger this abrupt increase in abdominal pH. The ingestion of amino acids, even at high concentrations, did not induce alkalinisation. During blood digestion, the thoracic midgut remains acidic, becoming a suitable compartment for carbohydrate digestion, which is in accordance with the higher alpha-glucolytic activity detected in this compartment. Ingestion of blood releases alkalising hormones in the haemolymph, which induce alkalinisation in ex vivo preparations. This study shows that adult A. aegypti females have a very similar gut physiology to that previously described for Lutzomyia longipalpis It is likely that all haematophagous Nematocera exhibit the same type of physiological behaviour.