RESUMO
Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.
RESUMO
To explain the increased transport of nutrients and metabolites and to control the movement of drug molecules through the transporters to the cancer cells, it is important to understand the exact mechanism of their structure and activity, as well as their biological and physical characteristics. We propose a computational model that reproduces the functionality of membrane transporters by quantifying the flow of substrates through the cell membrane. The model identifies the force induced by conformational changes of the transporter due to hydrolysis of ATP, in ABC transporters, or by an electrochemical gradient of ions, in secondary transporters. The transport rate is computed by averaging the velocity generated by the force along the paths followed by the substrates. The results obtained are in accordance with the experiments. The model provides an overall framework for analyzing the membrane transport proteins that regulate the flows of ions, nutrients and other molecules across the cell membranes, and their activities.
RESUMO
El condrocito es la única célula presente en el cartílago articular, por lo que es de gran importancia el conocimiento de los mecanismos que regulan sus funciones, en particular los mecanismos de transporte de membrana que le permiten a esta célula enfrentar los continuos cambios de la osmolaridad externa a que están sometidos como consecuencia de las variaciones en la carga mecánica. Los mecanismos implicados en la regulaciín del volumen intracelular, el pH intracelular, la concentraciín citoplásmica de calcio y el potencial de membrana son claves para la comprensiín de los procesos que se afectan con el desarrollo de la enfermedad, puesto que cualquier alteraciín de la homeostasis del condrocito articular afecta el metabolismo de los componentes de la matriz extracelular y por ende, las características funcionales del tejido. El presente artículo revisa los principales elementos funcionales del condrocito articular y su entorno en el contexto del transporte de membrana y su regulaciín.
The chondrocyte is the only cell in the articular cartilage; for this reason it is very important the knowledge about mechanisms that regulate its functions, particularly the membrane transport mechanisms which allow this cell to cope the continuous changes of external osmolarity as a consequence of variations in mechanic load. The mechanisms implied in regulation of cell volume, intracellular pH, cytoplasmic calcium concentration and membrane potential are key factors for understanding the process that are affected during illness, because any alteration of articular chondrocyte homeostasis affects the metabolism of the components of extracellular matrix and tissue functional characteristics. The present paper reviews the main functional elements of articular chondrocytes and its environment in the context of membrane transport regulation.