The role of TNF-α in the phagocytosis of largemouth bass (Micropterus salmoides) leukocytes.

Phagocytosis is an important innate immune process in which immune cells recognize, ingest and eliminate pathogens. Largemouth bass (Micropterus salmoides) has become an important economic farmed fish in many regions, while few studies has focused on phagocytosis of its leucocytes. In present study, largemouth bass peripheral blood leucocytes were separated using Percoll gradient to establish the phagocytic function. Flow cytometric analysis showed that largemouth bass leukocytes exhibited the phagocytic capacity to fluoresbrite microspheres and Aeromonas hydrophila, where higher phagocytic capacity to A. hydrophila were observed in granulocytes/monocytes than that of lymphocytes. The leukocytes engulfing fluoresbrite microspheres and A. hydrophila were also observed by fluorescence microscopy. Besides, manygenes associated with phagocytosis and TNF-α in leukocytes were up-regulated following A. hydrophila stimulation. Subsequently, the largemouth bass TNF-α was recombinantly expressed to investigate its role in regulating phagocytosis. The results showed that TNF-α in largemouth bass could significantly enhance the phagocytic ability of granulocytes/monocytes to A. hydrophila, but not lymphocytes. Moreover, we also found that TNF-α could not only significantly increase the ROS activity of granulocytes/monocytes, but also had the function of inducing its apoptosis. These results demonstrated that granulocytes/monocytes play more important role in phagocytosis, meanwhile, TNF-α has the function of enhancing the phagocytic ability of granulocytes/monocytes in largemouth bass.

Manipulation of a neutral and nonpolar nanoparticle in water using a nonuniform electric field.

The manipulation of nanoparticles in water is of essential importance in chemical physics, nanotechnology, medical technology, and biotechnology applications. Generally, a particle with net charges or charge polarity can be driven by an electric field. However, many practical particles only have weak and even negligible charge and polarity, which hinders the electric field to exert a force large enough to drive these nanoparticles directly. Here, we use molecular dynamics simulations to show that a neutral and nonpolar nanoparticle in liquid water can be driven directionally by an external electric field. The directed motion benefits from a nonuniform water environment produced by a nonuniform external electric field, since lower water energies exist under a higher intensity electric field. The nanoparticle spontaneously moves toward locations with a weaker electric field intensity to minimize the energy of the whole system. Considering that the distance between adjacent regions of nonuniform field intensity can reach the micrometer scale, this finding provides a new mechanism of manipulating nanoparticles from the nanoscale to the microscale.