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101.
L. GÓMEZ‐VALERO A. LATORRE R. GIL J. GADAU H. FELDHAAR F. J. SILVA 《Molecular ecology》2008,17(19):4382-4392
Genome reduction is a general process that has been studied in numerous symbiotic bacteria associated with insects. We investigated the last stages of genome degradation in Blochmannia floridanus, a mutualistic bacterial endosymbiont of the ant Camponotus floridanus. We determined the tempo (rates of insertion and deletion) and mode (size and number of insertion–deletion events) of the process in the last 200 000 years by analysing a total of 16 intergenic regions in several strains of this endosymbiont from different ant populations. We provide the first calculation of the reduction rate for noncoding DNA in this endosymbiont (2.2 × 10?8 lost nucleotides/site/year) and compare it with the rate of loss in other species. Our results confirm, as it has been observed in other organisms like Buchnera aphidicola or Rickettsia spp., that deletions larger than one nucleotide can still appear in advanced stages of genome reduction and that a substitutional deletion bias exists. However, this bias is not due to a higher proportion of deletion over insertion events but to a few deletion events being larger than the rest. Moreover, we detected a substitutional AT bias that is probably responsible for the increase in the number of the small and moderate indel events in the last stages of genome reduction. Accordingly, we found intrapopulational polymorphisms for the detected microsatellites in contrast to the stability associated with these in free‐living bacteria such as Escherichia coli. 相似文献
102.
SANTIAGO MERINO JUAN. MORENO RODRIGO A. VÁSQUEZ JAVIER MARTÍNEZ INOCENCIA SÁNCHEZ‐MONSÁLVEZ CRISTIÁN F. ESTADES SILVINA IPPI PABLO SABAT RICARDO ROZZI STEVEN MCGEHEE 《Austral ecology》2008,33(3):329-340
Abstract The existence of latitudinal gradients in species richness and their abundance is known for many free living organisms but few cases have been reported for parasitic diseases. In addition, asymmetries between the Northern and Southern Hemispheres in several characteristics may affect the distribution and diversity of species at all ecological levels. In this respect, we study the distribution of several genera of blood parasites infecting birds along a latitudinal gradient that includes the world's southernmost forests ecosystems. Birds were mist‐netted and sampled for blood in localities across Chile ranging from 33°S to 55°S during the years 2003–06. Overall, 26 bird species were sampled and 27 parasite lineages were identified. The latter belonged to three genera: Plasmodium (8), Haemoproteus (8) and Leucocytozoon (11). We found a positive significant relationship between prevalence and latitude for Leucocytozoon lineages and a negative relationship for Haemoproteus, Plasmodium and mixed infections. However, we did not find a significant relationship between parasite diversity and latitude. We found 18 lineages infecting only one species of host, and 19 lineages appear in only one of the localities of sampling. This pattern implies that some parasite lineages may evolve in isolation in some species/localities. In addition, specificity at the host‐family level was only found for Haemoproteus lineages infecting birds in the family Emberizidae. Individuals of the long distance migrant bird white‐crested elaenia (Elaenia albiceps), were found infected by the same parasite lineages in localities separated by 20° of latitude. Infections by these lineages were detected in other sedentary birds including juveniles and nestlings of different bird species. Therefore, long distance migrants are able to distort the presence of latitudinal gradients of diseases due to the potential role of migrants in spreading infections. Geographical gradients in prevalence of avian haematozoa differ between parasite genera and hemispheres, probably in relation to the existence of appropriate vector–parasite–host interactions. 相似文献
103.
- 1 The direct effect of sunlight on the conditioning, breakdown and incorporation of leaf litter in stream food webs has not yet been considered. The aim here was to evaluate the effects of light intensity on the colonization of leaf litter by microorganisms and its resulting quality as food for the stonefly shredder Klapopteryx kuscheli.
- 2 Leaf litter was conditioned for 2 months in an open reach of a second‐order stream in litter bags either exposed to or shaded from direct sunlight. Subsequently, we performed laboratory experiments to test larval consumption, growth, growth efficiency and feeding preference fed on both leaf litter treatments.
- 3 Leaf litter in the unshaded treatment had three times more chlorophyll‐a (Chl‐a) than that in the shaded treatment, 50% lower fungal biomass and similar bacterial abundance. Although larvae did not prefer either food and fed at the same rate on both leaf litter treatments, they grew twice as fast on the shade‐conditioned leaves and attained a two‐fold higher growth efficiency.
- 4 Sunlight can have significant effects on detritus‐based food webs. Riparian modification induced by human activities in forested catchments increases the potential for sunlight to influence detritus dynamics.
104.
HELENA C. BARROS NEWTON V. VERBISCK SOLANGE DA SILVA MARCIA F. ARAGUTH RENATO A. MORTARA 《The Journal of eukaryotic microbiology》1997,44(4):332-344
ABSTRACT. In this study we have examined the distribution of epitopes defined by monoclonal antibodies raised against Trypanosoma cruzi amastigotes during the intraceullar life cycle of the parasite. We have raised monoclonal antibodies towards amastigote forms and performed preliminary immunochemical characterization of their reactivities. MAB 1D9, 3G8, 2B7, 3B9, and 4B9, and 4B9 react with carbohydrate epitopes of the parasite major surface glycoprotein—Ssp-4 defined by MAB 2C2 [5]: MAB 4B5 reacts with a noncarbohydrate epitope in all developmental stages of the parasite, and MAB 3B2 also detects a noncarbohydrate epitope preferentially in T. cruzi flagellared forms. Vero cells infected with tissue culture-derived trypomastigotes of clone D11 (G strain) were fixed at different times during the intraceullular proliferation of parasites, and processed for immjno-electron microscopy and confocal immunoflurescence with the different monoclonal antibodies. We observed that while the surface distribution of MAB 2C2 and 4B9 epitopes was uniform throughout the cycle, MAB 1D9, 3G8, and 2B7 reacted with cytoplasmic membrance-bound compartments of the amastigotes. MAB 3B9 displayed a unique surface dentate pattern in some amastigotes. MAB 4B5 recognized a curved-shaped structure at the flagellar pocket region in some intracellular amastigotes and localized to the membrane in dividing forms. In intracellular trypomastigotes, MAB 4B5 also displayed a punctate pattern near the flagellar pocket. 相似文献
105.
Life history strategy of Leptinaria unilamellata (d'Orbigny, 1835) (Mollusca,Pulmonata, Subulinidae)
CAMILLA DE MEDEIROS CARVALHO JAIRO PINHEIRO DA SILVA CRISTIANE LAFETÁ FURTADO MENDONÇA ELISABETH CRISTINA DE ALMEIDA BESSA STHEFANE D'ÁVILA 《Invertebrate reproduction & development.》2013,57(4):211-222
Abstract Life history theory predicts that the patterns of resource allocation in animals are associated with different strategies, selected in the course of evolution. In the present study, the life history of Leptinaria unilamellata was characterized under laboratory conditions. We determined the growth, reproduction, and longevity patterns of this species and elucidated the strategy related to the development of embryos, through direct observations and examination of the morphology of the gravid uterus. Furthermore, we attempted to analyze the glycogen and galactogen contents of the albumen gland, digestive gland and cephalopedal mass in order to understand energy allocation to life history traits, for three life stages. Leptinaria unilamellata's life history is characterized by great longevity, a short juvenile phase, early sexual maturity, and repeated reproductive events, with little reproductive effort at each event and some mortality shortly after the first reproduction. In the terraria, we found juveniles but no eggs. However, the results of the anatomical study showed no morphological connection between the embryos and the parental organism. Thus, this species should be described as ovoviviparous rather than viviparous. Egg retention in the parent organism is the primary cause of the release of juveniles, instead of eggs, enabling the offspring to withstand environmental stress. The higher quantity of galactogen found in the adults' albumen gland, as compared to juveniles and senescent individuals, as well as the ratio of glycogen to galactogen, reveal the allocation of energy to reproduction rather than to growth. The remaining energy is directed to the maintenance of omeostasis. Such pattern was confirmed by the low levels of glycogen and galactogen observed in the senescent stage, compared to the juvenile and adult stages. In the life strategy of L. unilamellata, the distribution of the reproductive effort among many events associated with ovoviviparity indicates a long-term investment in reproductive success. 相似文献
106.
SUDIPTO CHATTERJEE NEERJA CHOWDHARY SULOCHANA PEDNEKAR ALEX COHEN GRACY ANDREW GRACY ANDREW RICARDO ARAYA GREGORY SIMON MICHAEL KING SHIRLEY TELLES HELENA VERDELI KATHLEEN CLOUGHERTY BETTY KIRKWOOD VIKRAM PATEL 《World psychiatry》2008,7(1):39-46
Common mental disorders, such as depression and anxiety, pose a major public health burden in developing countries. Although these disorders are thought to be best managed in primary care settings, there is a dearth of evidence about how this can be achieved in low resource settings. The MANAS project is an attempt to integrate an evidence based package of treatments into routine public and private primary care settings in Goa, India. Before initiating the trial, we carried out extensive preparatory work, over a period of 15 months, to examine the feasibility and acceptability of the planned intervention. This paper describes the systematic development and evaluation of the intervention through this preparatory phase. The preparatory stage, which was implemented in three phases, utilized quantitative and qualitative methods to inform our understanding of the potential problems and possible solutions in implementing the trial and led to critical modifications of the original intervention plan. Investing in systematic formative work prior to conducting expensive trials of the effectiveness of complex interventions is a useful exercise which potentially improves the likelihood of a positive result of such trials. 相似文献
107.
The role of Ca2+ in conoid extrusion was investigated in isolated Toxoplasma gondii tachyzoites by treatment with Ca2+-ionophores, Ca2+-chelating agents and an inhibitor of the Ca2+-ATPase at the endoplasmic reticulum. The results were evaluated by light phase-contrast microscopy and electron microscopy. lonomycin (0.5-1 μM) caused an immediate and sustained extrusion of the conoid in up to 80% of the tachyzoites, depending on the concentrations of ionophore and Ca2+ in the medium. However, over 50% of the tachyzoites extruded the conoid when treated with ionomycin in Ca2+-free saline complemented with EGTA. The effect of ionomycin was reversible and could be induced a second time in about half of the responsive population. Similar results were obtained with A23187. Conoid extrusion induced by ionomycin in Ca2+-free medium was almost completely abolished when the tachyzoites were previously loaded with a permeable compound known to chelate intracellular Ca2+ (BAPTA/AM; 25μM). On the other hand, exposure of tachyzoites to the Ca2+-ATPase inhibitor thapsigargin (0.5-1μM) produced significant extrusion of the conoid. Tachyzoites loaded with BAPTA/AM as well as those treated with ionomycin, i.e. with conoids paralyzed in opposite positions, had a diminished capacity to invade cultured epithelial cells. A substantial reduction in the response to stimulation by ionomycin was found also in parasites treated with cytochalasin-D, a drug that depolymerizes actin-filaments. The results suggest that Ca2+-release from internal stores may act as a key signal to activate a mechanism of conoid extrusion probably mediated, at least in part, by actin-filaments. 相似文献
108.
HELENA C. BARROS SOLANGE DA SILVA NEWTON V. VERBISCK MARCIA F. ARAGUTH ROBERTO C. TEDESCO DANIELA O. PROCOPIO RENATO A. MORTARA 《The Journal of eukaryotic microbiology》1996,43(4):275-285
ABSTRACT. Upon incubation at 37° C onto glass coverslips coated with Concanavalin A, poly-L-lysine, or a monoclonal antibody (1D9) directed to the parasite major surface glycoprotein Ssp-4, extracellular Trypanosoma cruzi amastigotes release trails of material barely visible by light microscopy. This release is not associated with parasite movements. Immunolabeling studies confirmed that the material is derived from the parasite's membrane since thin section through samples labeled with 1D9 revealed that the trails are membrane-bound structures. Scanning electron microscopy showed that the ∼0.1-μm thick trails of material emerging from the amastigotes can be uniform or beaded, indicating a tendency to vesiculation. The trails are preferentially released from the flagellar pocket region and/or at the opposite posterior end of the parasite body, and seem to be devoid of microtubules. The release is time and temperature-dependent and fixed parasites do not form trails. All attempts to inhibit trail release using drugs (antimycin A, sodium azide, cytochalasin D, nocodazole, genistein, staurosporine, EGTA) failed. The observation of trails associated with intracellular parasites and amastigotes invading Vero cells suggests that this is probably a physiological process. 相似文献
109.
MÁRCIA REGINA DA SILVA PEDRINT JOSÉ LUIZ CALDAS WOLFF STEVE REID 《The Annals of applied biology》2004,145(1):107-112
Baculoviruses are a group of viruses that infect invertebrates and that have been used worldwide as a biopesticide against several insect pests of the Order Lepidoptera. In Brazil, the baculovirus Spodoptera frugiperda multicapsid nucleopolyhedrovirus (SfMNPV; Baculoviridae) has been used experimentally to control S. frugiperda (Lepidoptera: Noctuidae), an important insect pest of corn (maize) fields and other crops. Baculoviruses can be produced either in insect larvae or in cell culture bioreactors. A major limitation to the in vitro production of baculoviruses is the rapid generation of mutants when the virus undergoes passages in cell culture. In order to evaluate the potential of in vitro methods of producing SfMNPV on a large-scale, we have multiplied a Brazilian isolate of this virus in cell culture. Extensive formation of few polyhedra mutants was observed after only two passages in Sf9 cells. 相似文献
110.