多核19F磁共振成像研究进展

~(19)氟(~(19)F)的磁共振成像(MRI)研究可追溯到35年以上。在这段时间里,~1H磁共振成像的蓬勃发展使磁共振成为影像医学的支柱,但~(19)F磁共振成像研究的进展却较为缓慢。然而最近几年,~(19)F磁共振成像的研究受到了广泛的关注。在某种程度上,这是由于MR成像中软件与硬件的发展,更因为分子影像学的概念的提出与发展。本文将对~(19)F多核磁共振成像的应用,特别是使用全氟化碳纳米成像探针的19F多核磁共振成像进行综述。     

Effects of perfluorinated oxygen carrier application in yeast, fungi and plant cell suspension cultures

The growth of the yeast Saccharomyces cerevisiae, the fungus Rhizopus nigricans and Nicotiana tabacum cells with perfluorodecalin as an oxygen carrier has been studied. The volumetric mass transfer coefficient (k_La) measured by the dynamic method was higher for the perfluorodecalin oxygenation system than for the conventional aeration system. The results show that perfluorocarbon can be successfully used as an efficient gas carrier, especially for the culture of delicate plant cells. The increase in yeast biomass in the suspension culture aerated by perfluorodecalin was as much as 110% higher than in the culture aerated by air. The fungus R. nigricans grew better when the conventional aeration system was used due to the fact that growth of the mycelium is limited by the transport of oxygen by diffusion in the pellets rather than by interfacial oxygen transport. In the case of isolated tobacco cells, an increase of over 350% in biomass growth was observed for the PFC aeration system.     

Beneficial effects of enhanced aeration using perfluorodecalin in <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> cultures for lipase production

The inadequate supply of oxygen to biomass is a critical factor to the productivity of most aerobic submerged fermentations. This happens because oxygen is sparingly soluble in the aqueous media. The use of a second liquid phase of perfluorocarbon (PFC), an oxygen-carrying compound, in the culture medium can increase the availability of oxygen to the microorganisms. The effect of perfluorodecalin on Yarrowia lipolytica cultures was investigated in shake-flask cultures. It was found that the specific growth rate of Y. lipolytica, a strictly aerobic yeast, increases with increasing PFC concentration. Extracellular lipase production was increased with 20% (v/v) of PFC and agitation of 250 rev/min. It was shown that the PFC presence benefitted lipase production and not just its secretion to the extracellular medium.