Synchronization of chaotic oscillations in doped fiber ring lasers.

The synchronization of chaotic rare-earth-doped fiber ring lasers is analyzed. The lasers are first coupled by transmitting a fraction c of the circulating electric field in the transmitter and injecting it into the optical cavity of the receiver. A coupling strategy which relies on modulation of the intensity of the light alone is also examined. Synchronization is studied as a function of the coupling strength, and we see excellent synchronization, even with very small c. We prove that in an open loop configuration (c=1) synchronization is guaranteed due to the particular structure of our equations and of the injection method we use. The generalized synchronization of these model lasers is examined when there is parameter mismatch between the transmitter and receiver lasers. The synchronization is found to be insensitive to a wide range of mismatch in laser parameters, but it is sensitive to other parameters, in particular those associated with the phase and the polarization of the circulating electric field. Communicating information between the transmitter and receiver lasers is also addressed. We investigate a scheme for modulating information onto the chaotic electric field and then demodulating and detecting the information embedded in the chaotic signal passed down the communications channel. We show full recovery with very low error for a wide range of coupling strengths.

Effect of immunosuppressive therapy on cytolytic activity of immunodeficient mice: implications for xenogeneic transplantation.

Despite major deficits in their immune system, SCID, Nude, and NIH III mice reject allo- and xenografts, particularly leukemic cell lines, albeit less readily than immunologically intact mice. Since variation among these immunodeficient mouse strains in rejection of a human lymphoid cell line (CCRF-CEM) parallels splenic non-MHC-mediated cytolytic activity, non-MHC-restricted cytolytic activity may be responsible for retained resistance to leukemic cell transplantation. SCID mice that had the least cytolytic activity accepted 100% of their grafts. The converse was true for NIH III mice that showed the greatest cytolytic activity and were relatively resistant to CEM cell engraftment. Different approaches to ablate NK activity and thus enhance engraftment led to variable results for each strain. A single dose (500 micrograms) of anti-asialoGM1 (AsGM1) markedly reduced NK activity in SCID and NIH III mice by 60 and 40%, respectively. A moderate 20% decrease was seen in Nude mice at this dose. In contrast, gamma irradiation suppressed NK activity by greater than 80% of baseline levels in all three strains. Of importance, total cytolytic activity in immunosuppressed Nude and NIH III mice, although significantly depressed compared to untreated mice of the same strain, still remained higher than that seen in nonimmunosuppressed SCID mice. Enhanced engraftment and systemic dissemination of CEM cells in immunosuppressed mice correlated directly with decreased total splenic cytolytic activity in all three strains. These results have implications for the use of immunodeficient models for transplantation, tumor immunobiology, and engraftment of a human immune system.

Human immunoglobulin production in immunodeficient mice: enhancement by immunosuppression of host and in vitro activation of human mononuclear cells.

The affect of host and donor related factors on successful engraftment of human cells into mice was examined to minimize the variability that has been observed in successful development of human-mouse chimera for the study of human disease and immune physiology and regulation. Human immunoglobulin production in severe combined immunodeficiency (SCID) mice engrafted with human peripheral blood mononuclear cells (PBMC) was augmented by immunosuppressing recipient mice and activating donor PBMC. Immunosuppression of recipient mice with 3 Gy of gamma-irradiation induced a 10-fold increase in human IgG in the sera of engrafted SCID mice. Variation in production of human IgG in recipient mice correlated with preinjection phenotype and activation status of injected PBMC. Mice injected with PBMC with a low CD4/CD8 ratio (less than 0.5) produced no detectable circulating human immunoglobulin. When the CD4/CD8 ratio was greater than 1.5, human IgG was detected in sera of PBMC-recipient SCID mice. Serum IgG increased 10-fold following in vitro activation of donor PBMC with anti-CD3, IL-2 and Staphylococcus aureus. Successful engraftment and serum IgG production was evidenced by an increase in the recovery of activated human IgG+ cells in the spleens of mice with maximal IgG production. Optimization of functional engraftment required modification of both the host (SCID mice) and the donor cells.