Transmission of Porcine Reproductive and Respiratory Syndrome Virus by Semen is Dose Dependent

Procine reproductive and respiratory syndrome virus (PRRSV) is transmitted through semen via natural mating or atrificial insemination. However, the minimal infective dose of PRRSV required to effect transmission through semen is not known. In this study, we induced estrus in PRRSV seronegative gilts and then artificially inseminated these animals with extended, commercial boar semen “seeded” with difference concentrations (2, 20, 200, 2,000, 20,000, 200,000, or 2,000,000 TCID50/50 ml of semen) of the PRRSV isolate SD 92-23983. Infection of gilts by PRRSV was confirmed by weekly bleedings of these animals to detect serconversion using the commercial IDEXX ELISA. All pigs (n=7) given ≥ 200,000 doses of PRRSV seroconverted 1 to 3 weeks after insemination. In contrast, only 1/5 and 1/5 pigs serconverted at dosages of 20,000 and 2,000, respectively. There was no seroconversion (0/14 pigs) at dosages ≤ 200. Pigs, wich did not seroconvert 4 to 5 weeks after artificial insemination with semen containing 200, 2,000, and 20,000 infectious doses of PRRSV, were intranasally inoculated with the same amount of virus. After intransal challenge 4/4 (20,000 doses), 4/4 (2,000 doses) and 0/4 (200 doses) pigs seroconverted within 1 to 3 weeks after inculation. The results indicated that higher infectious does of PRRSV/ml are required for transmission via semen compared to intransal inoculation, and the nested PCR assay can detect viral RNA in semen at concentrations that do not result in transmission of PRRSV by artificial insemenation

Recent Evolutionary Theorizing About Economic Change

The paper provides a broad overview of evolutionary thinking, and in particular, of evolutionary interpretations of socioeconomic change. The work assesses the state of the art in fields such as technological change, innovation-driven growth, and cultural and institutional evolution. It is also an important reference for all students of evolutionary change

Evaluation of a Macrophage Attenuated Isolate of PRRSV as a Vaccine for Porcine Reproductive and Respiratory Syndrome Virus

PRRS continues to be the most economically important disease of swine. While the acute reproductive disease is still prevalent, chronic, or endemic PRRS in nursery and grow/finish pigs is a major problem confronting most swine producers. Post-weaning problems in these herds include a 50-85% reduction in growth rates; a 10-30% increase in unmarketable pigs; and a 10-25% increase in psot-weaning morality. Popular protocols to manage PRRSV infections include bredding herd stabilization; elmination of seronegative sub-populations of susceptible gilts; nursery depopulation; and more recently mass vaccination/unidirectional pig flow in the grow/finsih unit. The goal of this project is to determine if an isolate of PRRSV, that has been moditifed by serial passage in monkey kidney cells (MARC-145) and replicates at very low levels in procine alveolar macrophages, is avirulent for pigs an pregnant gilts

Vortex Lattice in Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} Well Above the First-Order Phase-Transition Boundary

Measurements of non-local in-plane resistance originating from transverse vortex-vortex correlations have been performed on a Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} high-T_c superconductor in a magnetic field up to 9 T applied along the crystal c-axis. Our results demonstrate that a rigid vortex lattice does exist over a broad portion of the magnetic field -- temperature (H-T) phase diagram, well above the first-order transition boundary H_{FOT}(T). The results also provide evidence for the vortex lattice melting and vortex liquid decoupling phase transitions, occurring above the H_{FOT}(T).Comment: 14 pages, 10 figure

Reliance on trial and error signal derivation by Portia africana, an araneophagic jumping spider from East Africa

All species from the jumping spider (Salticidae) genus Portia appear to be predators that specialize at preying on other spiders by invading webs and, through aggressive mimicry, gaining dynamic fine control over the resident spider’s behaviour. From previous research, there is evidence that P. fimbriata, P. labiata and P. schultzi derive signals by trial and error. Here we demonstrate that P. africana is another species that uses a trial and error, or generate-and-test, algorithm when deriving the aggressive-mimicry signals that will be appropriate in different predator-prey encounters. We discuss the implications of these new findings and the findings from previous work for understanding the selection factors that drive the evolution of flexibility in aggressive-mimicry strategies

Factors Behind Cross-Industry Differences in Technical Progress

research and development ; productivity

The Formation of Fragments at Corotation in Isothermal Protoplanetary Disks

Numerical hydrodynamics simulations have established that disks which are evolved under the condition of local isothermality will fragment into small dense clumps due to gravitational instabilities when the Toomre stability parameter $Q$ is sufficiently low. Because fragmentation through disk instability has been suggested as a gas giant planet formation mechanism, it is important to understand the physics underlying this process as thoroughly as possible. In this paper, we offer analytic arguments for why, at low $Q$, fragments are most likely to form first at the corotation radii of growing spiral modes, and we support these arguments with results from 3D hydrodynamics simulations.Comment: 21 pages, 1 figur