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1.
Abstract

Carbonic anhydrases (CAs) are metalloenzymes, and classified into the evolutionarily distinct α, β, γ, δ, ζ, and η classes. α-CAs are present in many living organisms. β- and γ-CAs are expressed in most prokaryotes and eukaryotes, except for vertebrates. δ- and ζ-CAs are present in phytoplanktons, and η-CAs have been found in Plasmodium spp. Since the identification of α- and β-CAs in Caenorhabditis elegans, the nematode CAs have been considered as an emerging target in research focused on antiparasitic CA inhibitors. Despite the presence of α-CAs in both helminths and vertebrates, structural studies have revealed different kinetic and inhibition results. Moreover, lack of β-CAs in vertebrates makes this enzyme as an attractive target for inhibitory studies against helminthic infection. Some CA inhibitors, such as sulfonamides, have been evaluated against nematode CAs. This review article aims to present comprehensive information about the nematode CAs and their inhibitors as potential anthelminthic drugs.  相似文献   

2.
The antibacterial activity of propolis has been widely investigated. Since reports dealing with antimicrobial activity of the origin of propolis are not available, this study was carried out aiming to analyse the in vitro antimicrobial activity of the methanol extracts of poplar type propolis and Populus (Populus nigra, P. alba, P. tremuloides) buds as its sources against standard strains of a panel of microorganisms by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The concentrations of the “poplar” phenolics were relatively high (4.5%) and some compounds typical for P. nigra such as pinobanksin and 4,3 acetyloxycaffeate were found in the propolis sample by GC-MS. The poplar type propolis and Populus bud exudates were found to inhibit most clinically important microorganisms in a wide spectrum including pathogenic yeasts but not Gram-negative bacteria.  相似文献   

3.
There is an urgent need for safe and effective antifilarials. Prior studies have shown that the nitazoxanide (NTZ) exhibits broad activity against anaerobic bacteria, protozoa, and certain intestinal helminths. We examined the effects of NTZ and tizoxanide (TZ) on Brugia malayi nematodes in vitro and in vivo. In vitro, NTZ and TZ reduced worm motility and viability in a dose-dependent manner. Worm viability was reduced by 50% with both compounds at 2.5 and 20 μg/ml killed adult worms. NTZ or TZ (5 μg/ml) significantly reduced microfilaria release. These compounds blocked worm’s embryogenesis, and decreased microfilarial motility and viability. Treated worms had damaged cuticles and abnormal mitochondria. Wolbachia were not cleared by NTZ or TZ treatment. Neither NTZ nor TZ cleared adult worms or microfilariae in infected gerbils. These results show that NTZ and TZ have potent effects on B. malayi nematodes in vitro. However, they were not effective in vivo.  相似文献   

4.
Sensitivity of parasites to free radical damage by antiparasitic drugs   总被引:4,自引:0,他引:4  
Over the last few years a remarkable progress has been made in the understanding of parasites biochemistry, molecular biology, and immunology. This progress is especially encouraging in that emphasis on drug development is shifting from random screening towards a more rational approach. A number of peculiar aspects characteristic of parasites which are not present in other organisms and that might be exploitable for the design of specific agents have been described recently. One of these aspects is their deficiency in defense mechanisms against oxygen toxicity. Catalase is absent in many parasites. Distinct superoxide dismutases have been detected and specific inhibitors of these enzymes have been investigated. Glutathione is absent in some anaerobic protozoa. Peroxidase and reductase activities dependent on a glutathione-spermidine cofactor termed trypanothione have been detected in several trypanosomatids and apparently replace the glutathione peroxidase-glutathione reductase system of other eukaryotic cells. Free radical intermediates have been shown to be involved in the reaction of enzymes present in anaerobic protozoa. In addition, a number of antiparasitic agents have been shown to exert their actions through a free radical metabolism: nitro compounds used against trypanosomatids, anaerobic protozoa and helminths; crystal violet used in blood banks to prevent blood transmission of Chagas' disease; the antimalarial primaquine, chloroquinine, and quinhasou; and quinones active in vitro and in vivo against different parasites.  相似文献   

5.
Despite the chronic and debilitative nature of the infection they cause, several species of microsporidia and neogregarines offer a good potential as microbial control agents, particularly against insect pests of high economic thresholds. Techniques for mass production of protozoa have usually involved per os, inoculation or injection of the protozoa into their usual or alternate hosts. The spores are harvested subsequently from heavily infected host tissues by grinding, filtration, and differential centrifugation. Although fresh spores are used in most field tests, the spores of many species can be stored with high survival either frozen or in water at low temperatures (0–4°C) for up to several months. Sunlight or ultraviolet (UV) radiation is a serious factor limiting spore persistence. However, the protozoa do not appear to be significantly limiting spore persistence. However, the protozoa do not appears to be significantly more susceptible to UV radiation than other insect pathogens and persistence can be prolonged with UV protectants. Most field tests with protozoa have involved the application of spores in sprays and have usually resulted in a high degree of infection in the target host species. The potential for control of few species has been improved by formulation of spores in to baits, and the potential of other species will likely increase if suitable bait formulation can be devised in the future. One species, Nosema locustae, formulated as a bait, has been successfully used to control grasshoppers on rangelands. Limited laboratory and field studies have also suggested that increased short-term control might be obtained if candidate protozoan species can be combined with certain insecticides. While recent and increased efforts have been devoted to assess the potential of protozoa as microbial control agents, potential hazards to nontarget organism have been investigated for only three species. Their close relation taxonomically to protozoa pathogenic for mammals will necessitate careful evaluation of the safety of candidate control species for nontarget organisms.  相似文献   

6.
Abstract: The faunistic results regarding intestinal parasitism by protozoa and helminths in 21 primate species (three Cebidae, thirteen Cercopithecidae, one Hylobatidae, one Lemuridae, three Pongidae) are reported. The primate species were housed in four separate galleries. Six faecal samples of each host species were subjected to coprological analysis. Fifteen parasite species were detected: 11 protozoa (Entamoeba coli, E. chattoni, E. hartmanni, Iodamoeba bütschlii, Endolimax nana, Giardia intestinalis, Chilomastix mesnilii, Enteromonas hominis, Trichomonas intestinalis, Balantidium coli, and Blastocystis hominis) and 4 helminths (Ancylostoma sp., Strongyloides fuelleborni, Strongyloides sp., and Trichuris trichiura). The results reveal certain parasitic similarities between host species housed in the same gallery; however, these primate species do not always carry identical parasite species.  相似文献   

7.
Propolis is a plant-based sticky substance that is produced by honeybees. It has been used traditionally by ancient civilizations as a folk medicine, and is known to have many pharmaceutical properties including antioxidant, antibacterial, antifungal, anti-inflammatory, antiviral, and antitumour effects. Worldwide, researchers are still studying the complex composition of propolis to unveil its biological potential, and especially its antimicrobial activity against a variety of multidrug-resistant microorganisms. This review explores scientific reports published during the last decade on the characterization of different types of propolis, and evaluates their antimicrobial activities against Staphylococcus aureus and Candida albicans. Propolis can be divided into different types depending on their chemical composition and physical properties associated with geographic origin and plant sources. Flavonoids, phenols, diterpenes, and aliphatic compounds are the main chemicals that characterize the different types of propolis (Poplar, Brazilian, and Mediterranean), and are responsible for their antimicrobial activity. The extracts of most types of propolis showed greater antibacterial activity against Gram-positive bacteria: particularly on S. aureus, as well as on C. albicans, as compared to Gram-negative pathogens. Propolis acts either by directly interacting with the microbial cells or by stimulating the immune system of the host cells. Some studies have suggested that structural damage to the microorganisms is a possible mechanism by which propolis exhibits its antimicrobial activity. However, the mechanism of action of propolis is still unclear, due to the synergistic interaction of the ingredients of propolis, and this natural substance has multi-target activity in the cell. The broad-spectrum biological potentials of propolis present it as an ideal candidate for the development of new, potent, and cost-effective antimicrobial agents.  相似文献   

8.
Introduction – Because of its chemical diversity, the only way to standardise propolis is to specify multiple standards for different propolis types according to the corresponding chemical profile. So far, this has been done only for European propolis. Objective – To develop a rapid low‐cost spectrophotometric procedure for quantification of bioactive prenylated flavanones in Taiwanese propolis. Methodology – The proposed method quantifies the total flavanones on the basis of their absorption as coloured phenylhydrazones formed by interaction with 2,4‐dinitrophenylhydrazine. The procedure was validated through model mixture of compounds representing the composition of Taiwanese propolis according to previous studies. The major flavanones of the propolis samples (propolins C, D, F and G) were quantified by HPLC. Antiradical activity against DPPH was also measured. The DNP (dinitrophenylhydrazine) spectrophotometric method is applied for the first time for quantification of prenylated flavanones. Results – Spectophotometric procedure applicable to new type propolis (Macaranga type) was developed with recovery between 105 and 110% at the concentration range of 0.573–1.791 mg/mL. Six propolis samples were analysed by spectrophotometry using the procedure developed and validated, and by HPLC as the results demonstrated satisfactory agreement. Neither the spectrophotometric data nor the values measured by HPLC showed significant correlation with the antiradical activity against DPPH. Conclusion – The proposed spectrophotometric procedure is useful for routine analyses of Macaranga‐type propolis, because of its simplicity, repeatability and acceptable accuracy. Its application to a number of commercial samples could be used as a basis for standardisation and quality control of Pacific propolis. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
Hydroalcoholic propolis extracts from the bee species Melipona quadrifasciata have been shown to possess antimicrobial activity against different mollicute strains, but a methanolic extract (ME) could contain an increased diversity of nonpolar bioactive components with a potentially higher antimicrobial activity. The ME obtained by maceration of the propolis sample was fractionated with solvents of different polarities and then, purified by silica gel column chromatography through biomonitoring of its antimicrobial activity against mollicute strains. Analysis by gas chromatography-mass spectrometry (GC/MS) enabled the identification of compounds using the NIST library. Minimum inhibitory concentrations (MICs) of the samples were determined by broth microdilution. Anti-adhesive assays were performed with Mycoplasma pneumoniae cells. The hexane (MIC=62.5 mg/L) and dichloromethane (MIC=125 mg/L) fractions presented the most promising results against M. pneumoniae. They were fractionated into 74 subfractions, and even the best ones did not show better results (MIC>250 mg/L) than their original fractions, likely due to the loss of terpene compounds that seem to act in synergy. The dichloromethane subfraction FD4 was highlighted in the anti-adhesive assay with an inhibitory activity of 21.6 %. A synergistic effect of the nonpolar compounds in M. quadrifasciata propolis may be responsible for its antibacterial activity, but several purified components can improve its anti-adhesive properties.  相似文献   

10.
Protozoan parasites are responsible for severe disease and suffering in humans worldwide. Apart from disease transmission via insect vectors and contaminated soil, food, or water, transmission may occur congenitally or by way of blood transfusion and organ transplantation. Several recent outbreaks associated with fresh produce and potable water emphasize the need for vigilance and monitoring of protozoan parasites that cause severe disease in humans globally. Apart from the tropical parasite Plasmodium spp., other protozoa causing debilitating and fatal diseases such as Trypanosoma spp. and Naegleria fowleri need to be studied in more detail. Climate change and socioeconomic issues such as migration continue to be major drivers for the spread of these neglected tropical diseases beyond endemic zones. Due to the complex life cycles of protozoa involving multiple hosts, vectors, and stringent growth conditions, studying these parasites has been challenging. While in vivo models may provide insights into host–parasite interaction, the ethical aspects of laboratory animal use and the challenge of ready availability of parasite life stages underline the need for in vitro models as valid alternatives for culturing and maintaining protozoan parasites. To our knowledge, this review is the first of its kind to highlight available in vitro models for protozoa causing highly infectious diseases. In recent years, several research efforts using new technologies such as 3D organoid and spheroid systems for protozoan parasites have been introduced that provide valuable tools to advance complex culturing models and offer new opportunities toward the advancement of parasite in vitro studies. In vitro models aid scientists and healthcare providers in gaining insights into parasite infection biology, ultimately enabling the use of novel strategies for preventing and treating these diseases.  相似文献   

11.
Social insects construct nests that protect their brood and food resources from both the physical environment and natural enemies. Stingless bees use plant‐derived resins, mixed with wax to form propolis, in the construction of their nests, and these products can be effective sources of defense against natural enemies, including ants. However, it is not known whether this defense, in the form of deterring or repelling workers, derives from the physical properties or chemical compounds of these products. The nest entrance of Tetragonula carbonaria is constructed with propolis and Corymbia resins, and we ask whether nonvolatile chemicals present in these products act as a defense against ants. Our field experiments revealed that workers of Iridomyrmex mayri Forel were deterred from crossing a chemical barrier comprising nonvolatile, nonpolar (hexane) extracts of propolis and Corymbia tree resin. However, polar (ethanol) extracts did not have this effect. These data are the first to demonstrate that the chemical components alone of entrance propolis and resins can provide a nest‐defense function against ants.  相似文献   

12.
While the susceptibility to infection with blood protozoa, particularly Plasmodium spp. and Leucocytozoon, of a wide range of species of penguins held in captivity is well established, the parasitism of penguins in the wild has been less studied. It appears, however, that free-living penguins from temperate locations exhibit infrequent parasitism, with the exception of Spheniscus demersus in Southern Africa in which infection with Babesia peircei is endemic, while the few available reports suggest that Antarctic and sub-antarctic species exhibit a generalised absence of blood-borne parasites. We have extended these studies by examining 194 thin blood smears for blood protozoa obtained from 4 species of free-living penguins from 5 sites, and have detected no blood parasites in penguins from either Antarctic (Aptenodytes forsteri, Pygoscelis adeliae) or temperate (Eudyptulaminor, Spheniscus humboldti) locations. We discuss the possible reasons for the relative scarcity of blood protozoa in wild penguins, which include biting preferences or absence of suitable vectors, host specificity of the parasites, and long periods spent at sea by most penguin species, resulting in reduced opportunity for maintenance of parasite life-cycles. Accepted: 6 July 1998  相似文献   

13.
t Social insects have evolved colony behavioral, physiological, and organiza. tional adaptations (social immunity) to reduce the risks of parasitization and/or disease transmission. The collection of resin from various plants and its use in the hive as propolis is a clear example of behavioral defense. For Apis mellifera, an increased propolis content in the hive may correspond to variations in the microbial load of the colony and to a downregulation of an individual bee's immune response. However, many aspects of such antimicrobial mechanism still need to be clarified. Assuming that bacterial and fungal infection mechanisms differ from the action of a parasite, we studied the resin collection dynamics in Varroa destructor-infested honeybee colonies. Comparative experiments involving hives with different mite infestation levels were conducted in order to assess the amount of resin collected and propolis quality within the hive, over a 2-year period (2014 and 2015). Our study demonstrates that when A. mellifera colonies are under stress because of Varroa infestation, an increase in the number of resin foragers is recorded, even if a general intensification of the foraging activity is not observed. A reduction in the total polyphenolic content in propolis produced in infested versus uninfested hives was also noticed. Considering that different propolis types show varying levels of inhibition against a variety of honey bee pathogens in vitro, it would be very important to study the effects against Varroa of two diverse types of propolis: from Varroa-free and from Varroa-infested hives.  相似文献   

14.
FK506 (tacrolimus) and polyketide macrolides such as rapamycin and its derivates bind to FK506-binding proteins (FKBPs). These proteins display a peptidyl-prolyl rotamase function that is believed to catalyze protein folding and they are well-validated anti-proliferative drug targets in certain pathogenic microorganisms, and their functions have been characterized in parasitic protozoa. However, much less is known in helminths and trials with rapalogs on cestoda have not yet been reported. Due to a growing need for new treatment options for human cystic echinococcosis, the in vitro efficacy of rapalogs in Echinococcus granulosus was investigated. We determined the effect of ramapycin, FK506 and everolimus against this cestode, demonstrating their protoscolicidal ability. Also, we observed synergic scolicidal actions during combined therapy with rapalogs plus cyclosporine A, proposing dual administration of drugs to improve pharmacological effects in vivo. We have identified an E. granulosus (Eg)-fkb1 gene that encodes Eg-FKBP, an archetypal protein of the FKBP family, which includes all residues implicated in the binding of pharmacological ligands, in the enzymatic activity and in interactions with possible target proteins. Levels of Eg-fkb1 mRNA are over-expressed by acid but not rapalog treatment. We also described the presence of receptor-operated calcium channels in the larval stage, suggesting that exogenous ligands may dissociate the interaction of Eg-FKBP from these intracellular channels, enhancing the activity of the Ca2+ release and interfering with their normal regulatory functions. As rapamycin sensitivity is the major criterion used to detect targets of rapamycin kinase, we identified and analyzed in silico critical residues of putative homologs in the Echinococcus genome. These preliminary results will allow us to continue subsequent studies that could reveal the precise intracellular functions of Eg-FKBP, providing greater knowledge for further identification of downstream target proteins, a promising target for chemotherapy of cystic echinococcosis.  相似文献   

15.
Blood-feeding organisms digest hemoglobin, releasing large quantities of heme inside their digestive tracts. Free heme is very toxic, and these organisms have evolved several mechanisms to protect against its deleterious effects. One of these adaptations is the crystallization of heme into the dark-brown pigment hemozoin (Hz). Here we review the process of Hz formation, focusing on organisms other than Plasmodium that have contributed to a better understanding of heme crystallization. Hemozoin has been found in several distinct classes of organisms including protozoa, helminths and insects and Hz formation is the predominant form of heme detoxification. The available evidence indicates that amphiphilic structures such as phospholipid membranes and lipid droplets accompanied by specific proteins play a major role in heme crystallization. Because this process is specific to a number of blood-feeding organisms and absent in their hosts, Hz formation is an attractive target for the development of novel drugs to control illnesses associated with these hematophagous organisms.  相似文献   

16.
Dual biological control, of both insect pests and plant pathogens, has been reported for the fungal entomopathogens, Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycota: Hypocreales) and Lecanicillium spp. (Ascomycota: Hypocreales). However, the primary mechanisms of plant disease suppression are different for these fungi. Beauveria spp. produce an array of bioactive metabolites, and have been reported to limit growth of fungal plant pathogens in vitro. In plant assays, B. bassiana has been reported to reduce diseases caused by soilborne plant pathogens, such as Pythium, Rhizoctonia, and Fusarium. Evidence has accumulated that B. bassiana can endophytically colonize a wide array of plant species, both monocots and dicots. B. bassiana also induced systemic resistance when endophytically colonized cotton seedlings were challenged with a bacterial plant pathogen on foliage. Species of Lecanicillium are known to reduce disease caused by powdery mildew as well as various rust fungi. Endophytic colonization has been reported for Lecanicillium spp., and it has been suggested that induced systemic resistance may be active against powdery mildew. However, mycoparasitism is the primary mechanism employed by Lecanicillium spp. against plant pathogens. Comparisons of Beauveria and Lecanicillium are made with Trichoderma, a fungus used for biological control of plant pathogens and insects. For T. harzianum Rifai (Ascomycota: Hypocreales), it has been shown that some fungal traits that are important for insect pathogenicity are also involved in biocontrol of phytopathogens.  相似文献   

17.
Summary The red sandy loam soils of Bangalore were found to contain Colpoda spp. and Uroleptus spp. as the predominant protozoa. The effect of these protozoa on Rhizobium S-12 and Azotobacter chroococcum which gain entry into soil as bacterial inoculants was studied. In the presence of protozoa a fall in the population of Rhizobium S-12 and A. chroococcum in soil suggested that these bacteria serve as prey for the protozoa. But complete devouring of the prey by the predators never occurred. In broth culture decline in the population of the two bacteria in the presence of protozoa was much quicker compared to soil. Several bacteria survived in broth too suggesting that soil does not prevent the predator from finding its prey. This upholds the recent view that the protozoa devour bacteria if they are sufficiently close to each other, that the energy gained by devouring the cell is greater than that required for hunting. Reduced nodulation and not absence of nodules, in soybean by Rhizobium S-12 in presence of protozoa further supports this view. re]19751105  相似文献   

18.
Methotrexate has been widely used in the treatment of osterosarcoma, intracranial lymphomas and leukemia. However, patients are also at high risk of opportunist pathogens such as Aspergillus spp. infection for their deeply depressed immunity. The optimal choice of antifungal agents during the infection of Aspergillus for these patients is necessary to be explored. In this study, we investigated the interactions between antifungals and methotrexate against Aspergillus in vitro. A total of 23 clinical isolates of Aspergillus spp. were studied. Microdilution checkerboard technique was performed to evaluate the interaction of methotrexate with voriconazole, itraconazole, terbinafine and amphotericin B. The highest rate of synergy was obtained for the combination of terbinafine and methotrexate, which exhibited synergy against 60.9% (14/23) of strains. No interaction was detected for the combinations of methotrexate plus itraconazole or amphotericin B against 95.7% (22/23) or 100% of strains, respectively. Although voriconazole exhibited indifferent against 87% (20/23) of strains when combined with methotrexate, antagonism effect was found against 13% (3/23) of strains. The positive interactions of terbinafine and methotrexate were also certified by disk diffusion assay. In addition, we observed the morphological changes for the interaction of methotrexate with terbinafine against Aspergillus. Further inhibition and distortion of growth were found after the combination of terbinafine and methotrexate compared with the drugs treated alone. Clinical studies are warranted to further elucidate optimal treatments for the immucompromised patients with Aspergillus infection.  相似文献   

19.
Isavuconazole is a new triazole currently undergoing phase III clinical trials. This compound has shown in vitro activity against a large number of clinically important yeasts and moulds including Aspergillus spp., Fusarium spp., Scedosporium spp., Candida spp., the Zygomycetes and Cryptococcus spp. Similar to voriconazole, reduced in vitro activity is seen against Histoplasma capsulatum. In vivo efficacy has been demonstrated in murine models of invasive aspergillosis and candidiasis. Additionally, there are several potential pharmacokinetic and drug–drug interaction advantages of this compound over existing antifungal agents. This review summarizes existing data that has been either published or presented at international symposia.  相似文献   

20.
The relationship between Bactrocera oleae (Rossi 1790) and its endosymbiont Candidatus Erwinia dacicola is important to achieving effective control of the olive fly population in the field. This bacterium plays a crucial role in the life of B. oleae and is necessary for its fitness. Thus, in the absence of the endosymbiont, B. oleae wild populations in the field might decrease considerably. Copper is one of the most used antimicrobials for horticultural crops worldwide, and its efficacy against Ca. E. dacicola has been demonstrated in field trials. Propolis is another natural antimicrobial compound largely used for its activity in several fields. If propolis and copper prove to be efficient against wild populations of the endosymbiont B. oleae in the field, such a biological restraint might improve sustainable agriculture. We evaluated, under laboratory conditions, the effect of two different copper products (at two different concentrations, 5% and 20%) and propolis on the content of Ca. E. dacicola in the eggs and in the adult oesophageal bulbs of B. oleae. Bulbs were extracted twice, after 2 and 5 weeks of exposure. Real‐time PCR on the bulbs showed a reduction in Ca. E. dacicola content in flies treated with copper (at both 5% and 20%), and from the first to the second extraction, while flies treated with propolis showed an increment of the relative abundance of Ca. E. dacicola. Both copper products (5% and 20%) reduced the egg production after 2 and 5 weeks in comparison with the control and propolis treatments. Moreover, adult mortality was significantly higher with propolis compared with the other treatments. Thus, our results encourage further research in order to develop new tools for the control of the olive fly in the framework of an integrated pest management strategy.  相似文献   

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