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91.
92.
Aim To investigate biogeographical patterns of cleptoparasitic Exaerete bee species and their orchid bee hosts.
Location Neotropical region, from Central America to southern Brazil.
Methods Correlations between relative frequencies of cleptoparasitic Exaerete species and their host Eulaema species were employed to investigate the geographical association between such species pairs.
Results Our data support the current proposition that the Eulaema meriana / Eulaema flavescens complex is the main host for Exaerete frontalis . Contrary to current belief, however, Eulaema nigrita apparently is not the only and, in some regions, not the most important host for Exaerete smaragdina .
Main conclusions Current knowledge on cleptoparasite host associations among orchid bees is based on fortuitous observations, and in some instances generalizations from such observations are not corroborated by the frequencies and distributions of the bees involved. Our data suggest that cleptoparasitic pressure, rather than other features of the forest environment, may be responsible for the low abundance of E. nigrita in the Amazonian forests. 相似文献
Location Neotropical region, from Central America to southern Brazil.
Methods Correlations between relative frequencies of cleptoparasitic Exaerete species and their host Eulaema species were employed to investigate the geographical association between such species pairs.
Results Our data support the current proposition that the Eulaema meriana / Eulaema flavescens complex is the main host for Exaerete frontalis . Contrary to current belief, however, Eulaema nigrita apparently is not the only and, in some regions, not the most important host for Exaerete smaragdina .
Main conclusions Current knowledge on cleptoparasite host associations among orchid bees is based on fortuitous observations, and in some instances generalizations from such observations are not corroborated by the frequencies and distributions of the bees involved. Our data suggest that cleptoparasitic pressure, rather than other features of the forest environment, may be responsible for the low abundance of E. nigrita in the Amazonian forests. 相似文献
93.
da Silveira Costa MI 《Mathematical biosciences》2007,205(1):77-82
In this work, it is shown that in a deterministic context, a threshold policy can induce cyclic behavior in an otherwise exploited stable population. These dynamics ensue as a result of the combination of the degree of harvesting pressure and more protective threshold densities. Virtual equilibrium in variable structure systems plays a determinant role in this dynamical outcome. 相似文献
94.
Villela IV de Oliveira IM Silveira JC Dias JF Henriques JA da Silva J 《Mutation research》2007,628(2):76-86
The Guaíba Basin is a source of drinking water for Porto Alegre (RS, Brazil). The water from this basin receives industrial, urban, and rural waste from many sources. The mussel species Limnoperna fortunei was chosen based on population data, distribution, and sensitivity. Previous tests with comet assay and micronuclei frequency in this freshwater mussel have shown to be successful in biomonitoring studies. The aim of this study was to evaluate the genotoxic contamination of the Guaíba Lake Hydrographic Region, through the determination of damage by the micronuclei and comet assays in L. fortunei (golden mussel). Nine sampling sites were evaluated in three different seasons: five sites in the mouths of the main rivers that flow into Guaíba lake; one site at the mouth of a stream; one major site of sewage discharge; two sites at Guaíba lake, near a sewage discharge; and the control site in a preservation area. DNA damage was detected by the single cell gel assay, as well as the frequency of micronuclei in hemocytes of mussels exposed under laboratory conditions for 7 days to water and sediment samples. Significant results were found in different seasons in almost all sampling sites (P<0.05, ANOVA Dunnet's test). Most of the positive results were found in samples affected mainly by urban effluents. It was possible to observe that there was a weak relation between mutagenic and genotoxic responses and mussels inorganic elements contents. Seasonal variation was observed at different sampling sites, but always indicating a huge contamination near urban sewage discharge. These results are consistent with previous studies, allowing us to infer that urban contamination is the biggest problem in this region. It is also possible to infer that L. fortunei is a good sentinel organism for the Guaíba Basin. 相似文献
95.
96.
Silveira EM Rodrigues MF Krause MS Vianna DR Almeida BS Rossato JS Oliveira LP Curi R de Bittencourt PI 《Cell biochemistry and function》2007,25(1):63-73
Moderate physical activity when performed on a regular basis presents a number of benefits to the whole organism, especially regarding immune system function, such as augmenting resistance to infections and to cancer growth. Although glutamine production by active muscle cells as well as neuroendocrine alterations mediated by the chronic adaptation to exercise may play a role, the entire mechanism by which exercise makes the immune system aware of challenges remains mostly uncovered. This is particularly true for the effects of an acute exercise session on immune function. In this work, circulating monocytes/macrophages from sedentary rats submitted to an acute (1 h) swimming session were tested for the ability of phagocytosing zymosan particles, phorbol myristate acetate (PMA)-induced hydrogen peroxide production, nitric oxide (NO) release (assessed by nitrate and nitrite production) and the expression of NO synthases (NOS-1, NOS-2 and NOS-3). The results showed that an exercise bout induced a 2.4-fold rise in macrophage phagocytic capacity (p = 0.0041), a 9.6-fold elevation in PMA-induced hydrogen peroxide release into the incubation media (1-h, p = 0.0022) and a 95.5%-augmentation in nitrite basal production (1-h incubation; p = 0.0220), which was associated with a marked expression of NOS-2 (the inducible NOS isoform; p = 0.0319), but not in other NOS gene products. Although NOS-2 expression is nuclear factor-kappaB (NF-kappaB)-dependent, no systemic oxidative stress was found, as inferred from the data of plasma TBARS and glutathione disulphide (GSSG) to glutathione (GSH) ratio in circulating blood erythrocytes which remained constant after the acute exercise. Also, no stressful situation seemed to be faced by monocytes/macrophages, since the expression of the 70-kDa heat shock protein (HSP70) remained unchanged. We conclude that NF-kappaB-dependent induction of NOS-2 and macrophage activation must be related to local factor(s) produced in the surroundings of monocytes/macrophages. 相似文献
97.
da Silveira RB Pigozzo RB Chaim OM Appel MH Silva DT Dreyfuss JL Toma L Dietrich CP Nader HB Veiga SS Gremski W 《Biochimie》2007,89(3):289-300
Loxoscelism (the condition produced by the bite of brown spiders) has been reported worldwide, but especially in warmer regions. Clinical manifestations include skin necrosis with gravitational spreading while systemic loxoscelism may include renal failure, hemolysis and thrombocytopenia. The venom contains several toxins, of which the best biochemically and biologically studied is the dermonecrotic toxin, a phospholipase-D. Purified toxin induces cutaneous and systemic loxoscelism, especially necrotic lesions, hematological disturbances and renal failure. Herein, we describe cloning, heterologous expression and purification of two novel dermonecrotic toxins: LiRecDT4 and LiRecDT5. The recombinant proteins stably expressed in Escherichia coli cells were purified from culture supernatants in a single step using Ni(2+)-chelating chromatography producing soluble proteins of 34 kDa (LiRecDT4) and 37 kDa (LiRecDT5). Circular dichroism analysis evidenced correctly folding for toxins but differences in secondary structures. Both proteins were recognized by whole venom serum antibodies and by a specific antibody to dermonecrotic toxin. Also, recombinant toxins with phospholipase activity induced experimental skin lesions and caused a massive inflammatory response in rabbit skin dermis. Nevertheless, toxins displayed different effects upon platelet aggregation, increase in vascular permeability and not caused death in mice. These characteristics in combination with functional studies illustrates that a family of dermonecrotic toxins exists, and includes two novel members that are useful for future structural and functional studies. They will also be useful in biotechnological ends, for example, as inflammatory and platelet aggregating studies, as antigens for serum therapy source and for lipids biochemical research. 相似文献
98.
99.
Duarte FS Codeço Martins PR Romeiro GA Monteiro De Lima TC 《Bioorganic & medicinal chemistry》2007,15(4):1645-1650
This study investigated the antidepressant-like effect of 4-amine derivatives of 10,11-dihydro-5H-dibenzo-alkylamine-cycloheptane, 4-amine (3-N,N-dimethylpropylamine)-10,11-dihydro-5H-dibenzo[a,d]cycloheptane-5-one (ADDCH1) and 1,2,3,4,8,9-hexahydro-dibenzocyclohepta[4,4a,5-ef]1,4-diazepin (ADDCH2), in a validated experimental model of depression, the forced swimming test (FST) in mice. Female adult mice were sub-chronically (three doses in 24 h) or repeatedly (once a day for 10 days) treated with either of the compounds and evaluated in the FST. The sub-chronic treatment promoted a dose-dependent reduction in the immobility time in the FST with the doses of 50 mg/kg (ADDCH1) and 30 mg/kg (ADDCH2) ip being the most effective (33% and 37% of reduction, respectively). A similar profile of action was observed in the animals repeatedly treated with ADDCH1 50 mg/kg or ADDCH2 30 mg/kg ip (for 10 days) and there was no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. These findings suggest that these amine derivatives of the system dibenzocycloheptane have an antidepressant-like action which could be of clinical interest and, therefore, deserves further investigation. In addition, putative underlying mechanisms of action are discussed. 相似文献
100.
Leonel da Silveira Lobo Sternberg Su Yean Teh Sharon M. L. Ewe Fernando Miralles-Wilhelm Donald L. DeAngelis 《Ecosystems》2007,10(4):648-660
A
bstract
The boundaries between mangroves and freshwater hammocks in coastal ecotones of South Florida are sharp. Further, previous
studies indicate that there is a discontinuity in plant predawn water potentials, with woody plants either showing predawn
water potentials reflecting exposure to saline water or exposure to freshwater. This abrupt concurrent change in community
type and plant water status suggests that there might be feedback dynamics between vegetation and salinity. A model examining
the salinity of the aerated zone of soil overlying a saline body of water, known as the vadose layer, as a function of precipitation,
evaporation and plant water uptake is presented here. The model predicts that mixtures of saline and freshwater vegetative
species represent unstable states. Depending on the initial vegetation composition, subsequent vegetative change will lead
either to patches of mangrove coverage having a high salinity vadose zone or to freshwater hammock coverage having a low salinity
vadose zone. Complete or nearly complete coverage by either freshwater or saltwater vegetation represents two stable steady-state
points. This model can explain many of the previous observations of vegetation patterns in coastal South Florida as well as
observations on the dynamics of vegetation shifts caused by sea level rise and climate change. 相似文献