Does mesodermal patterning by an inducer gradient depend on secondary cell-cell communication?
We conclude that communication among responding cells underlies much of the remarkable patterning influence of activin. Moreover, we suggest that these findings can inform thinking about how inducer gradients might act in other systems, shifting emphasis from the initial response of cells to inducer concentration toward the elaboration of complex pattern by secondary interactions.
A significant proportion of TDR, primarily in older, white MSM, was undetected by conventional testing. The greatest underestimation was for rapid-decaying mutations typically associated with the source virus having recent exposure to antiretroviral therapy. However, total TDR prevalence was highest in the less than 20-year age group who were predominantly black, underscoring the importance of prevention efforts for at-risk youth.