Temperature coefficients of SAW delay and velocity for Y-cut and rotated LiNbO(3).

Measurements that indicate that the surface-acoustic-wave (SAW) temperature coefficients of delay and velocity over approximately room temperature to +100 degrees C for the popular cuts of lithium niobate are presented. These values of delay coefficient are close to the value previously given for Y-cut LiNbO(3) but are significantly different from values given for the rotated cuts.

Continuous-wave surface-acoustic-wave delay-difference device.

A novel surface-acoustic-wave (SAW) device for continuous-wave (CW) delay-difference measurement or wideband interference-rejection at VHF frequencies is described and test results are given. The delay-difference device (DDD) operates at a center frequency of 160 MHz with a 31-MHz bandwidth over which root-mean-square amplitude ripple is 0.13 dB and need not be operated in a gated mode. A pair of input signals to the CW DDD may be at any frequency within the bandwidth of the DDD, modulated in any form, and even amplitude unbalanced to some degree by system amplifiers and still the CW DDD and its associated electronics will accurately measure the relative delay of the signals and interpret that as direction of arrival or phase as desired. Used in an interference cancelling mode the device tested shows an average 25-dB signal rejection over its 31-MHz bandwidth.

LPS-induced differentiation of a murine B cell leukemia (BCL1): changes in surface and secreted IgM.

We examined the effect of LPS-induced differentiation on surface and secreted IgM in a cloned BCL1 in vitro cell line. Incubation of this cell line with LPS resulted in a decrease in the amount of membrane IgM, measured by both immunofluorescence and immunoprecipitation, and an increase in IgM secretion, measured by plaque-forming cells (PFC). Activation to high rate secretion was independent of cell cycle in synchronized cells and was independent of DNA synthesis because PFC formation was not inhibited by hydroxyurea. Almost all cells in the in vitro line were shown to contain large quantities of intracytoplasmic IgM before LPS activation. Thus, it would appear that the in vitro cell line represents a partially activated stage of differentiation compared to normal resting B cells or to the in vivo line of BCL1. Analysis of the two forms of mRNA coding for membrane and secreted IgM showed that, at least for cells at the level of differentiation examined here, the control of membrane IgM expression is post-transcriptional. The differentiation of resting B cells to the plasma cell level appears to consist of multiple stages of differentiation. The present data suggest that LPS provides at least two signals of activation. One induces the resting cell to synthesize cytoplasmic IgM, increase surface IgM, and to begin cell division. The second induces the secretion of intracytoplasmic IgM associated with a decrease in surface IgM.

Simultaneous expression of immunoglobulin mu and delta heavy chains by a cloned B-cell lymphoma: a single copy of the VH gene is shared by two adjacent CH genes.

The cloned murine B-cell lymphoma line (BCL1) that expresses surface IgM and IgD is considered to be a model for the immunoglobulin gene expression of the mature virgin B cell. Of particular interest is the mechanism by which a single VH gene is shared by two CH genes. We examined the organization of the immunoglobulin heavy chain genes in BCL1 DNA. A single arrangement of CH genes was found with the expressed VHDJH gene complex just 5' to the Cmu gene. The complete DNA sequence of the VH gene was determined. No rearrangement occurred in the intervening DNA between the JH and C mu genes or between the C mu and C delta genes. We conclude that dual expression of mu and delta heavy chains using a single VH gene is accomplished by alternate processing of a primary transcript that encompasses the the VHDJH complex and both CH genes.