排序方式: 共有30条查询结果,搜索用时 0 毫秒
11.
Micheli Dassi Naiéli S. Souto Ana C. M. Braga Mayara L. Freitas Clarissa Vasconcelos Mauro S. Oliveira 《Journal of environmental science and health. Part. B》2013,48(12):840-845
AbstractFu monisin B1 (FB1) is a mycotoxin commonly found in maize and maize-based products. Ingestion of FB1-contaminated causes a myriad of dose- and species-dependent toxic effects to human and animal health. In the present study we evaluated the effects of FB1 (8?mg/kg, i.p. for 4?days) on body weight and oxidative stress parameters in the liver, kidney and lung of C57BL/6 male mice. No changes in the organ-to-body weight ratio, organ-to-adrenal gland weight ratio or organ-to-brain weight ratio were found. On the other hand, FB1 exposure increased NPSH levels in liver and lungs whereas decreased FRAP content in liver and kidneys. Levels of TBARS, ascorbic acid and NOx content were not altered by FB1. In summary, four days of FB1 exposure are sufficient to disrupt antioxidant defenses in liver, kidneys and lungs of C57BL/6 male mice without concomitant changes in organs weight. 相似文献
12.
13.
J. A. Baeza A. A. Braga L. S. López-Greco E. Perez M. L. Negreiros-Fransozo A. Fransozo 《Marine Biology》2010,157(12):2643-2653
One of the main goals of sex allocation theory is understanding sex ratio evolution. However, theoretical studies predicting
sex ratios in species with unusual sexual systems, such as protandric simultaneous (PS) hermaphroditism, are rare. In PS hermaphrodites,
juveniles first develop into functional males that mature into simultaneous hermaphrodites later in life. Here, we report
on the sex ratio (males/males + hermaphrodites) in the PS hermaphroditic shrimp Exhippolysmata oplophoroides. A 2-year study demonstrated that hermaphrodites dominated the population in two different bays. This skewed sex ratio may
be explained by limited encounter rates among conspecifics. In agreement with this idea, the density of shrimps was extremely
low (≤1 shrimp km−2) at the two study sites. Size at sex phase change and sex ratios remained relatively stable through time at the two bays.
The stability of these parameters might be explained by the rather steady population structure of this species during the
study period. A review of sex ratios in PS hermaphroditic shrimps (Lysmata and Exhippolysmata) revealed considerable variation; some species have male- and others hermaphrodite-skewed sex ratios. The conditions explaining
inter- and intra-specific sex ratio variation in protandric simultaneous hermaphroditic species remain to be addressed. 相似文献
14.
In the 1950s, a production plant of hexachlorocyclohexane (HCH) was established in Brazil with the main purpose of producing chemicals for vectors control. This factory was closed down in 1955 and around 300 tons of production residues were left behind in the open air. In 1995, the area was treated with lime to eliminate the HCH contamination. Soil sample gave a PCDD/F concentration of 13 900 ng I-TEQ/kg whereas samples from the neighborhood ranged from 0.19 to 2.08 ng I-TEQ/kg. PCDD/F levels in cow's milk samples varied from 4.1 to 6.5 pg I-TEQ/g of milk fat. High concentration in soil collected from the site suggests that treatment and recovery shall be made. Further dioxin monitoring is needed to better estimate the risk posed to local population through food consumption and soil usage. 相似文献
15.
Benedito Braga Paulo S. F. Barbosa 《Journal of the American Water Resources Association》2001,37(4):837-852
ABSTRACT: A network flow algorithm has been developed for the optimization of real‐time operation of a multiple reservoir system. Two purposes have been considered in the operation: flood control and hydropower generation. A special network structure was developed which allows the consideration of river routing. A multiobjective formulation is utilized thus allowing generation of a non‐dominated curve. The effect of imperfect forecast on the performance of the real‐time operation model is also evaluated. An application is made to a subsystem of the Brazilian hydroelectric system, located in the Paranapanema river basin. In this case study, the model showed good performance under the largest flood of the historical records. 相似文献
16.
Maria Cristina G. Antunes Sandra Pinto Fernando G. Braga Joaquim C.G. Esteves Silva 《Chemistry and Ecology》2013,29(2):141-152
The ability of pine bark and almond shells to remove bisphenol A (BPA) from aqueous solutions was evaluated. Samples of these traditional agro-forestry by-products were milled, sieved into different particle size fractions (0.10–0.15 and 1.5–2.0 mm) and submitted to two different types of treatment. Sorption experiments were conducted in a batch system at room temperature and natural pH. Sorption equilibrium was attained after 48 h for all systems under study. Bisphenol A was adsorbed more effectively on the smaller particles of the sorbents. Pine bark and almond shell pretreated with formaldehyde presented higher sorption efficiency (95%), followed by almond shell (87%) and pine bark (82%) washed with hot water. All the sorption isotherms were found to fit a Freundlich equation, with correlation coefficients (R 2) between 0.823 and 0.989. The sorption coefficient (K F) ranged from 0.06 to 0.74 (mg1?1/n ·L 1/n ·g ?1). These results indicate that utilisation of both materials as an alternative sorbent for the removal of bisphenol A from contaminated waters is promising because they are available in large amounts and have an acceptable cost–efficiency ratio when compared with traditional adsorbents. 相似文献
17.
Organotin compounds (OTs) were used in antifouling paints for more than four decades. However, due to their widespread intensive
use and high toxicity, undesirable effects in non-target marine organisms have been detected since the early 1980s. Consequently,
the International Maritime Organization banned new maritime applications of these products on January 1, 2003 and their presence
on ship hulls from January 1, 2008. Although extensively studied in Europe, North America, Oceania, and Asia, environmental
levels and effects of organotin contamination are still poorly known for South America. Thus, the current review aimed to
present the actual status of this problem in South America by summarizing and comparing the available data in the literature.
An overview of the OTs concentrations in sediment and biota and their effects, mainly imposex in marine gastropods, are presented.
This work showed that in Atlantic coastal areas of South America there are “hot spots” of OTs contamination, similar to that
observed in industrialized countries of Northern Hemisphere. On the other hand, the number of accomplished studies in the
Pacific coast is extremely low. Despite the limitation on studies about OTs environmental levels and their related effects,
the available data pointed out for a widespread TBT contamination along the South American coastal areas. Therefore, the establishment
of baselines of organotin contamination in the Pacific coast and the implementation of temporal trend studies in the South
American coastal areas is crucial to verify the effectiveness of local regulations and OTs global ban, and to map the most
sensitive areas related to present and future antifouling impacts. 相似文献
18.
José Cavalcante Souza Vieira Camila Pereira Braga Grasieli de Oliveira Aline de Lima Leite João Vitor de Queiroz Bruna Cavecci Alis Correia Bittarello Marília Afonso Rabelo Buzalaf Luiz Fabricio Zara Pedro de Magalhães Padilha 《Environmental Chemistry Letters》2017,15(4):717-724
Bioaccumulative metals such as mercury are found in increasing amounts in fish and their consumers. In the region of the Madeira River, in the Brazilian Amazon, mercury (Hg) is a predominant contaminant in the aquatic ecosystem. There is therefore a need to find specific biomarkers of mercury toxicity in fish to monitor contaminations. Here, mercury-bound proteins were identified in the liver tissues of fishes Mylossoma duriventre and Brachyplatystoma rousseauxii. Mercury was quantified in liver tissue, pellets and protein spots by graphite furnace atomic absorption. Proteins were fractionated by two-dimensional polyacrylamide gel electrophoresis and identified by mass spectrometry with electrospray ionization. We identified nine proteins linked to mercury and that presented biomarker characteristics of mercury. Among the proteins identified, isoforms of parvalbumin, ubiquitin-40S ribosomal protein S27a, brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 2 and betaine–homocysteine S-methyltransferase 1 are notable for having the molecular function of binding to metallic ions. 相似文献
19.
Gonçalves FL Carvalho LM Conde FC Latorre MR Saldiva PH Braga AL 《Environment international》2005,31(3):343-349
Effects of meteorological variables and air pollutants on child respiratory morbidity are investigated during two consecutive summers (December-March 1992/1993 and 1993/1994) at the Metropolitan Area of S?o Paulo (MASP), Brazil. The MASP, with almost 17 million inhabitants, is considered the most populous region in South America. Due to warmer temperatures, increased rainfall and consequent low levels of air pollutants during the summer compared to winter, less attention has been paid to epidemiological studies during this season, especially in tropical urban areas such as S?o Paulo. In the present work, principal component analysis (PCA) is applied to medical end environmental data to identify patterns relating child morbidity, meteorological variables and air pollutants during the summer. The following pollutant concentrations are examined: SO2, inhalable particulate matter (PM10), and O3. The meteorological variables investigated are air temperature, water vapor (water vapor density) and solar radiation. Although low correlation between respiratory morbidity and environmental variables are, in general, observed for the entire dataset, the PCA method indicates that child morbidity is positively associated with O3 for the 1992/1993 summer. This pattern is identified in the third principal component (PC3), which explains about 19% of the total variance of all data in this summer. However, the 1993/1994 summer shows a more complex association between both groups, suggesting stronger ties with meteorological variables. Marked changes in synoptic conditions from the end of January to end of March of the 1993/1994 summer seem to have played an important role in modulating respiratory morbidity. A detailed examination of meteorological conditions in that period indicates that prefrontal (postfrontal), hot (cold) and dry (wet) days favored the observed decrease (increase) of respiratory morbidity. 相似文献
20.
Leopoldo Rodrigues Braga Jr. John Henry Percival Brooman Jos Jaílson Niccio Alves Luís Gonzaga Sales Vasconcelos Romildo Pereira Brito 《Journal of Loss Prevention in the Process Industries》2006,19(6):736-742
The most critical aspect of polymerization reactors is the agitator's stop and becomes more serious when this occurs exactly at the removal of the heat load, which is generated by the reaction (exothermic). This phenomenon is typical in power-failure situations of the energy supply or because of other related problems at the plant. The objective of this work is to compare the performance of two configurations for the inhibition-injection system for vinyl chloride monomer (VCM) polymerization reactors. To determine the injection time a rigorous mathematical model was developed. From the results of this work one of the configurations was implemented in an industrial plant. 相似文献