RESUMO
The rat has been used extensively as a health sentinel, indicator, or monitor of environmental health hazards, but this model has not been directly validated against human exposures. Humans in Mexico City show upper respiratory tract lesions and evidence of pulmonary damage related to their environmental inhalation exposure. In this study, male and female F344 rats were exposed (23 hr/day) in Mexico City to local Mexico City air (MCA)* for up to seven weeks. Controls were maintained at the same location under filtered air. Prior to these exposures, several steps were taken. First, the nasal passages of normal male rats shipped from the United States and housed in Mexico City were examined for mycoplasma infection; no evidence of infection was found. In addition, a mobile exposure and monitoring system was assembled and, with an ozone (O3) exposure atmosphere, was tested along with supporting histopathology techniques and analysis of rat nasal and lung tissues. Last, the entire exposure model (equipment and animals) was transported to Mexico City and validated for a three-week period. During the seven-week study there were 18 one-hour intervals during which the average O3 concentration of MCA in the exposure chamber exceeded the US National Ambient Air Quality Standard (NAAQS) of 0.120 ppm 03 (hourly average, not to be exceeded more than once per year). This prolonged exposure of healthy F344 rats to MCA containing episodically low to moderate concentrations of 03 (as well as other urban air pollutants) did not induce inflammatory or epithelial lesions in the nasal airways or lung as measured by qualitative histologic techniques or quantitative morphometric techniques. These findings agree with those of previous controlled O3 inhalation studies, but they are in contrast to reports indicating that O3-polluted MCA causes significant nasal mucosal injury in adults and children living in southwestern Mexico City. Taken together, these findings may suggest that human airways are markedly more susceptible to the toxic effects of MCA than are the airways of the F344 rat.
Assuntos
Poluentes Atmosféricos/toxicidade , Mucosa Nasal/efeitos dos fármacos , Ozônio/toxicidade , Sistema Respiratório/efeitos dos fármacos , Animais , Modelos Animais de Doenças , Monitoramento Ambiental , Feminino , Humanos , Masculino , México , Mucosa Nasal/patologia , Ratos , Ratos Endogâmicos F344 , Sistema Respiratório/patologia , Medição de Risco , Emissões de Veículos/toxicidadeRESUMO
Petroleum asphaltenes are hydrocarbons that present an extremely complex molecular structure. They are conformed by different proportions of nitrogen, sulfur and oxygen. These compounds cause diverse problems like the blockage of crude oil extraction and transport pipes, the reduction of their economic use and the pollution of ecosystems. Biodegradation of asphaltenes is an important process that can eliminate these compounds and reduce the problems they cause. However, it is a process that occurs naturally in very reduced proportions. The purpose of this revision is to show the chemical structure of these compounds, the problems they cause and to represent their possible biodegradation mechanisms, based on the processes known for other hydrocarbons of complex structure. Elimination of the micelar structure, through the application of non-polar solvents, and fragmentation of the asphaltenes through photooxidation are the initial processes necessary to be able to degrade these compounds. The produced structures, such as the heteropolyaromatic and aromatic, lineal and ramified hydrocarbons, could be degraded in this order through biochemical reactions, such as omega oxidations, beta oxidations and aromatic oxidations respectively. These processes are distributed in an important variety of microorganisms. The elimination period's length can vary from one week, for the simplest structures, to 990 days for those with several condensed aromatic rings.
Assuntos
Biodegradação Ambiental , Hidrocarbonetos Policíclicos Aromáticos , Bactérias/metabolismo , Benzo(a)pireno/metabolismo , Indústria Química , Heptanos/farmacologia , Estrutura Molecular , Oxirredução , Petróleo , Fotoquímica , Hidrocarbonetos Policíclicos Aromáticos/química , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/efeitos da radiação , Pirenos/metabolismo , Microbiologia do Solo , Poluentes do Solo/metabolismo , Solventes/farmacologiaRESUMO
Microbial flow tracers are presently limited to a strain of Bacillus globigii and a few highly specific bacteriophages. Bacillus subtilis 65-8 produces a black pigment as part of the primary metabolism under minimal nutritional conditions, with glucose as the sole carbon and energy source. This work shows that Bacillus subtilis 65-8 spores are thermostable (55 degrees C during 150 días), halotolerant (they germinate and grow in an enriched medium with up to 12% NaCl), persistent in a system of sand-soil and sewage, even in the presence of added commercial oil derivatives (kerosene, leaded gasoline and unleaded diesel), they are capable to move through porous systems even as the liquids, viscous as they may be, move through. Moreover, spores were resistant to the presence of autochtonous microorganisms in sewage, where we did not detect any other organism with differential characteristics like our strain (black pigment production in minimal medium) which could interfere with the identification of our biological flow tracer. The characteristics of Bacillus subtilis 65-8 make it a suitable biological flow tracer.
Assuntos
Bacillus subtilis/crescimento & desenvolvimento , Microbiologia Industrial/métodos , Movimento Celular , Meios de Cultura , Concentração de Íons de Hidrogênio , Esporos Bacterianos/crescimento & desenvolvimento , Temperatura , Fatores de TempoRESUMO
Fourteen different plant seeds were used to obtain lectins which in turn were used to agglutinate 72 different serological strains of Klebsiella. The results were used to design a scheme which distinguishes 62 serotypes (91.6%) with a unique agglutination pattern with lectins. Two pairs of strains as well as two sets of three strains gave the same patterns. This procedure is useful as an alternative in the identification of strains for epidemiological purposes.