RESUMO
AIMS: Dinoponera quadriceps venom (DqV) was examined to evaluate the antibacterial activity and its bactericidal action mechanism against Staphylococcus aureus. METHODS AND RESULTS: DqV was tested against a standard strain of methicillin-sensitive Staphylococcus aureus (MSSA), Staph. aureus ATCC 6538P and two standard strains of methicillin-resistant Staphylococcus aureus (MRSA), Staph. aureus ATCC 33591 and Staph. aureus CCBH 5330. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the rate of kill and pH sensitivity of the DqV were determined by microdilution tests. Bactericidal and inhibitory concentrations of DqV were tested to check its action on Staph. aureus membrane permeability and cell morphology. The MIC and MBC of DqV were 6·25 and 12·5 µg ml(-1) for Staph. aureus ATCC 6538P, 12·5 and 50 µg ml(-1) for Staph. aureus CCBH 5330 and 100 and 100 µg ml(-1) for Staph. aureus ATCC 33591, respectively. Complete bacterial growth inhibition was observed after 4 h of incubation with the MBC of DqV. A lowest MIC was observed in alkaline pH. Alteration in membrane permeability was observed through the increase in crystal violet uptake, genetic material release and morphology in atomic force microscopy. CONCLUSIONS: The results suggest antibacterial activity of DqV against Staph. aureus and that the venom acts in the cell membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: Alteration in membrane permeability may be associated with the antimicrobial activity of hymenopteran venoms.
Assuntos
Venenos de Formiga/farmacologia , Antibacterianos/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Animais , FormigasRESUMO
Greenhouse and laboratory studies were conducted to evaluate feeding activity and superficial damage to soybean seed by the brown-winged stink bug, Edessa meditabunda (F.), and the Neotropical brown stink bug, Euschistus heros (F.). Soybean plants (cv. BRS 282), at R6 stage of development were used. Thirty pairs of each species were used individually for 48 h. Two daily observations (9:00 AM and 3:00 PM) were taken to record the number of bugs (feeding/resting) on plant parts. Harvested seeds imbibed in tetrazolium solution were photographed for measurement of the damaged surface. Adult E. meditabunda significantly preferred soybean stems (19.7 bugs) to pods (2.7). Feeding/resting was similar at 9:00 AM (mean number of 28.0 bugs) and 3:00 PM (24.3). Euschistus heros equally fed/stayed on stems (7.3 bugs) and pods (6.9), although most bugs (12.3) remained on the cage net; feeding/resting on all plant structures amounted to 13.7 bugs at 9:00 AM and 17.7 bugs at 3:00 PM. Amylase activity was greater for E. heros (41.61 ± 0.89 U/mg) and almost none for E. meditabunda (2.35 ± 0.14 U/mg). The superficial damage to seeds was significantly greater for E. meditabunda (22. 9 mm(2)) compared to E. heros (12.5 mm(2)). However, E. meditabunda caused less shrinkage of the seed tegument, while E. heros damage was deeper and seeds showed reduction in size.
Assuntos
Amilases/metabolismo , Comportamento Alimentar , Glycine max/parasitologia , Hemípteros/fisiologia , Saliva/enzimologia , Sementes/parasitologia , Animais , HeterópterosRESUMO
Limited information exists on the insecticide susceptibility of redbanded stink bug, Piezodorus guildinii (Westwood) (Heteroptera: Pentatomidae), despite its impact on soybean, Glycine max (L.) Merr., production in Brazil and the United States. Therefore, this study set out to 1) determine baseline levels of susceptibility to currently recommended pesticides using topical and vial bioassays, 2) determine the levels of esterase activity in populations in the United States and Brazil, and 3) compare control among products in field trials. In topical bioassays conducted in the United States using technical grade materials, the LC50 values of lambda-cyhalothrin, acephate, and methamidophos were 4-25, 141-295, and 40-151 ng per insect, respectively. The LC50 values of imidacloprid and thiamethoxam were 11 and 27 ng per insect, respectively. In vial bioassays conducted in the United States using technical grade materials, the LC50 values of cypermethrin, acephate, and methamidophos were 0.4-0.9, 3.8, and 1.6 microg per vial, respectively. In topical bioassays conducted in Brazil by using commercially formulated products, the LC50 values of acephate, methamidophos, endosulfan, and imidacloprid were 0.90-1.9, 0.4-0.6, 1.5-6.6, and 0.2-0.3 microg per insect, respectively. In vial bioassays conducted in Brazil using commercially formulated products, the LC50 values of endosulfan, methamidophos, and lambda-cyhalothrin were 4-32 and 2-24 microg/cm2 for thiamethoxam and imidacloprid. Esterase activity in Louisiana (United States) populations ranged from 251 to 658 nmol alpha-naphthol formed/min/mg protein. Esterase activity levels in Londrina (Brazil) populations averaged 163 nmol/min/mg. In field tests, P. guildinii in Louisiana were controlled by organophosphates thiamethoxam and imidacloprid and in Brazil, with combinations of neonicotinoids and pyrethroids.
Assuntos
Esterases/metabolismo , Heterópteros , Inseticidas , Animais , Brasil , Heterópteros/enzimologia , LouisianaRESUMO
Cachaça (aguardente) is a rum-style spirit made from sugar cane juice by artisanal methods in Brazil. A study was made of the production, biochemistry and microbiology of the process in fifteen distilleries in Sul de Minas. Identification of 443 yeasts showed Saccharomyces cerevisiae to be the predominant yeast but Rhodotorula glutinis and Candida maltosa were predominant in three cases. Bacterial infection is a potential problem, particularly in older wooden vats, when the ratio of yeasts:bacteria can be 10:1 or less. A study of daily batch fermentations in one distillery over one season in which 739 yeasts were identified revealed that S. cerevisiae was the predominant yeast. Six other yeast species showed a daily succession: Kluyveromyces marxianus, Pichia heimii and Hanseniaspora uvarum were present only at the beginning, Pichia subpelliculosa and Debaryomyces hansenii were detected from mid to the end of fermentation, and Pichia methanolica appeared briefly after the cessation of fermentation. Despite a steady influx of yeasts from nature, the species population in the fermenter was stable for at least four months suggesting strong physiological and ecological pressure for its maintenance. Cell densities during the fermentation were: yeasts - 4 x 108/ml; lactic acid bacteria -4 x 10(5)/ml; and bacilli - 5 x 10(4)/ml. Some acetic acid bacteria and enterobacteriaceae appeared at the end. Sucrose was immediately hydrolysed to fructose and glucose. The main fermentation was complete after 12 hours but not all fructose was utilised when harvesting after 24 hours.
Assuntos
Bebidas Alcoólicas/microbiologia , Leveduras/isolamento & purificação , Leveduras/metabolismo , Brasil , Metabolismo dos Carboidratos , Etanol/metabolismo , Fermentação , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/isolamento & purificação , Saccharomyces cerevisiae/metabolismo , Leveduras/classificação , Leveduras/citologiaRESUMO
The hemorrhagic syndrome of leptospirosis was studied in guinea pigs. The study correlates hematological, histopathological and immunohistochemical alterations in sixty animals inoculated by the intraperitoneal route with 1ml of the culture of virulent strain of Leptospira interrogans serovar copenhageni. Leptospirae antigens were detected by immunoperoxidase, chiefly in liver, kidney and heart muscle capillaries. Possible pathogenic mechanisms responsible for hemorrhagic syndrome are discussed with emphasis on toxic and anoxic attacks causing damage to endothelia, platelet depletion and alterations to hemostasia rates: prothrombin time [PT], partial thromboplastin time [PTT] and fibrinogen concentrations. The clinical-laboratory picture is compatible with the histopathological observation of disseminated intravascular coagulation [DIC] in most of the guinea pigs from day 4 of infection.
Assuntos
Hemorragia/microbiologia , Leptospirose , Animais , Cobaias , SíndromeRESUMO
The stability constants for a series of oxovanadium(IV) complexes of polyaminocarboxylic acids were determined by potentiometry. The values obtained are almost equal to those of the corresponding nickel(II) complexes. The complexes formed by terdentate and quadridentate ligands contain 2 and 1 co-ordinated water molecules, respectively. These dissociate at pH ~4 in the first case, to give dimers-(VO)(2)(OH)(2)L(2),-and at about pH ~7, in the second case, to give the mononuclear hydroxo species VO(OH)L. Hydrolysis of the 1:1 aquo-complexes is preferred to the formation of 2:1 ligand: metal complexes even in the presence of a 10-fold molar excess of ligand. These results are of interest for better understanding of the behaviour of oxovanadium(IV) in biological systems.
RESUMO
The authors discuss the microscopic changes in gastrocnemius muscle in Leptospirosis in 63 patients. The hyaline necrosis frequently associated to a hemorrhagic infiltrate represented the most important feature in the lesional picture of the disease. Other findings were swelling, loss of cross striations, vacuolation and regenerative changes of muscle fibres. This last one was represented by multinucleated sarcoblasts and the presence of thin and strongly basophilic new-formed fibres. Interstitial hemorrhage was frequently seen and an inflammatory afflux was only rarely observed. This histological picture was considered as characteristic and highly significant for the diagnosis of Leptospirosis.