Differentiation of memory T cells to virus plaque-forming cells and cytotoxic T lymphocytes

The aims of this study were to define the T-cell subpopulation(s) detected by the virus plaque assay, and particularly to determine whether the virus plaque assay could be used to enumerate cytotoxic T lymphocytes. In addition, studies were undertaken to ascertain whether cell proliferation was required for development of cytotoxic effector function and virus plaque formation by these subpopulations. The results of experiments with a secondary mouse mixed lymphocyte culture (MLC) model indicated that 70 percent of virus plaque-forming cells bore the Ly 1 phenotype and 30 percent the Ly 2,3 phenotype. Three lines of evidence suggested that cytotoxic T lymphocytes (CTL) can be detected by this assay: the fact that some virus plaque-forming cells (V-PFC) bear the same Ly phenotype as CTL; the use of an inhibitor of DNA synthesis indicated that proliferating cells could be eliminated with no effect on V-PFC production and cytotoxic activity of the Ly 2,3 cell population; and that infection of primed lymphocyteswith vesicular stomatitis virus before (MLC) stimulation eliminated cytotoxic activity. In primary MLC, development of V-PFC and CTL was completely abolished by cytosine arabinoside. In contrast, in secondary MLC, some CTL and V- PFC were generated by antigenic stimulation in the absence of proliferation. However, the development of both functions became progressively more susceptible to cytosine arabinoside as the time between primary immunization and in vitro boosting is increased. It is suggested that there may be a considerable disparity between the number of existing effector cells at any given time and the cytotoxic potential, i.e. the number of cells capable of being generated by antigenic stimulation.     

Boundary feedback control of a vibrating beam subject to a displacement constraint

The problem of controlling the dynamic response of a beam by means of boundary feedback is solved. The control is applied at one of the supports of the beam by means of a torque actuator in order to keep the maximum deflection within specified bounds. Since the location and time of the maximum deflection depend on the control itself, the feedback is determined by the solution of a min-max problem. The theory is illustrated by a numerical example involving an impulsively loaded beam, and the effectiveness of the proposed control is studied numerically.     

Prenatal ultrasound diagnosis of clubfoot

Five cases of congenital clubfoot diagnosed prenatally by ultrasound are reported. The incidence of clubfoot may be higher within an affected family and may be associated with other structural anomalies or chromosomal abnormalities. Identifying a clubfoot in utero should therefore alert the sonographer that other anomalies may be present and should lead to a detailed structural survey.