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Porcine reproductive and respiratory syndrome (PRRS) is one of the most serious diseases affecting the swine industry worldwide; however, there is no efficient control strategies against PRRSV at present. Therefore, development of new antiviral treatment strategies is urgently needed. As reported, germacrone can efficiently impair influenza virus replication. In this study, we exploited whether germacrone has the potential to inhibit PRRSV infection. Our results showed that the germacrone significantly inhibited replication of PRRSV in vitro and repressed the synthesis of viral RNA and protein. However, it did not block PRRSV binding and entry. Further studies confirmed that germacrone impaired PRRSV replication at an early stage, and inhibited infection of both classic and highly pathogenic type II PRRSV strains. Collectively, our findings imply that the germacrone has the potential to be used as an anti-PRRSV drug. [ABSTRACT FROM AUTHOR]

This paper presents a novel leapfrog signal flow graph (SFG) implementation by fully differential Op amp integrators, which combines low sensitivity, high dynamic range with simple circuit configuration. The direct SFG simulation and leapfrog SFG simulation can yield integrator-based structures likewise, but both of them will lead to higher circuit complexity, noise density and sensitivity. Three Butterworth 5-order high-pass filters with a pass band edge frequency of 1.778 kHz are designed based on different SFGs. From the example, the noise density of the simplest leapfrog configuration is approximately 0.4 nV/Hz1/2 lower than those of the other two in the stop band, and shows the best noise density in the pass band. The sensitivity densities of two types of leapfrog filters are approximately equivalent, while that of the direct SFG simulation filter is much higher. However, the pass band response of the simplest configuration is not as good as those of the other two because of two parasitic zeros (at 708 kHz, −31.6 dB and 1.59 MHz, −20.55 dB) and a parasitic pole (at 4.57 MHz, 45.5 dB). [ABSTRACT FROM AUTHOR]