PubMed · 113057
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A C Upton. Interview: low-level radiation.. https://doi.org/10.3322/canjclin.29.5.306
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Final extents of fusion of influenza virus (A/PR/8/34 strain) with neutral and partially acidic liposomes were monitored with (i) a fluorescence resonance energy-transfer assay in which the liposomes were labeled and (ii) by the dequenching of octadecylrhodamine, initially incorporated in the viral membrane. The latter assay was also employed in the fusion of influenza virus and Sendai virus with erythrocyte ghosts. In all cases, a phenomenon of partial fusion activity of the virus was observed, which is distinct from low pH inactivation. The unfused influenza or Sendai virions, which were separated by sucrose gradient centrifugation from liposomes or erythrocyte ghosts exhibited again partial fusion activity toward freshly added liposomes or ghosts, respectively. The conclusion is that the fraction of initially bound and unfused virions does not consist of defective particles, but rather of particles bound to the target membranes via inactive sites on the virus (or on cellular membranes), or else, partial fusion activity is a manifestation of a certain probability of production of fusion inactive sites by irreversible association of viral glycoproteins or peptides in the target membrane.
Fluorescence microscopy is an important tool for biological research, in part because of the extremely high detection sensitivity that can be achieved, but also because fluorescent molecules can be used as probes on account of their environmental responsiveness, for example to measure intracellular pH or metal ion concentration. Unfortunately, the environmental sensitivity can sometimes be a source of problems because of enhancement or 'quenching', which can make it very difficult to relate emission intensity to the amount of fluorophore present. The measured intensity is essentially proportional to the product of the amount of fluorophore present in the sample and the local quantum yield of the fluorophore (the quantum yield can be thought of as the probability that an excited molecule decays by fluorescence emission rather than by other non-radiative processes). This is a particular difficulty in an environment such as a cell or tissue slice in which quantum yield and flurophore concentration can both vary within the sample. Ideally we would wish to be able to measure the quantum yield of fluorescence as well as the fluorescence intensity, as this would allow environmental effects to be compensated for. Unfortunately, this is not at all easy, and indirect means to achieve the same goal are more appropriate. A recently introduced technique, fluorescence lifetime imaging (Morgan et al. 1992, Wang et al. 1992), offers one such means to improve quantification of fluorescence microscopy. In addition, as will be explained, the technique offers the prospect of significantly improving detection sensitivity in appropriate circumstances.
Rotary blood pumps often require a constant operating voltage. To meet this requirement and to eliminate the need for percutaneous leads, a voltage-regulated transcutaneous energy transfer (TET) system has been developed. Voltage regulation is achieved by using a transcutaneous infrared feedback control loop operating on a 890 nanometer (nm) wavelength. In vitro testing of the system developed has shown that output voltage can be maintained to within 0.2 V of nominal (14.5 V) for delivered powers up to 50 watts (W) and coil separations of between 3 and 10 mm. Power transfer efficiencies were determined to be from 68% to 72% over the tested range of coil separations and output currents from 1.5 to 3.6 amperes (A). This system has demonstrated acceptable performance in regulating output voltage while transferring power inductively without using percutaneous connections. By integrating this type of TET system with an implanted rotary blood pump, the quality of life for the device recipient could be improved.