Anti-SRF monoclonal antibody, clone 3H3

A 3-D or large-aperture 2-D synthetic transmit aperture (STA) ultrasound imaging system with a fully sampled array usually leads to high hardware complexity and cost since each element in the array is individually controlled. To reducethe hardware complexity, we propose a large-pitch method for STA (LPSTA) imaging integrated with a spatial response function (SRF) in the image reconstruction to improve image quality. To achieve this, we decreased the total number of measurement channels M (the product of the number of transmissions I-T and the number of the receive channels in each transmission I-R). We combined L adjacent elements in transmission and Kadjacent elements in receive into subapertures (SAPs), where L and K were coprime (no common factors) integers to suppress the grating lobes. We denoted it as an (N/L, N/K) system, where N is the number of transducer elements. In this article, first, we derived the beam pattern of the LPSTA using a far-field approximation. We demonstrated that the coprime selection and SRF can significantly reduce the grating lobes level (GLL) by using a beam pattern analysis. We also found that the LPSTA can have a similar beam pattern as that of a full array when the target is located along the steering direction. Second, the imaging performance of LPSTA was evaluated and validated with Field II simulations and experiments. The simulation results demonstrated that the proposed LPSTA with (N/3, N/5) can achieve on average similar to 25% improvement in lateral resolution, similar to 24.6% and similar to 42.3% improvement in contrast-to-noise ratio (CNR) and contrast ratio (CR), respectively, over B-mode with a large-pitch receiver with (N, N/5). LPSTA achieved comparable image contrast to the standard STA with the full array (N, N) at the cost of a reduced field of view. The experiment results were consistent with the simulation results. Finally, in addition to reducing the system (hardware) complexity, the LPSTA was more computationally efficient than the standard STA with a full array. The proposed method may help in realizing clinical applications of real-time 2-D or 3-D ultrasound imaging using large arrays.

The SRF/MRTF and upstream signaling cascade play key roles in actin cytoskeleton organization and myocyte development. To date, how this signaling axis may function in brown adipocyte lineage commitment and maturation has not been delineated. Here we report that MRTF-SRF signaling exerts inhibitory actions on brown adipogenesis, and suppressing this negative regulation promotes brown adipocyte lineage development. During brown adipogenic differentiation, protein expressions of SRF, MRTFA/B and its transcription targets were downregulated, and MRTFA/B shuttled from nucleus to cytoplasm. Silencing of SRF or MRTF-A/MRTF-B enhanced two distinct stages of brown adipocyte development, mesenchymal stem cell determination to brown adipocytes and terminal differentiation of brown adipogenic progenitors. We further demonstrate that the MRTF-SRF axis exerts transcriptional regulations of the TGF-beta and BMP signaling pathway, critical developmental cues for brown adipocyte development. TGF-beta signaling activity was significantly attenuated, whereas that of the BMP pathway augmented by inhibition of SRF or MRTF-A/MRTF-B, leading to enhanced brown adipocyte differentiation. Our study demonstrates the MRTF-SRF transcriptional cascade as a negative regulator of brown adipogenesis, through its transcriptional control of the TGF-beta/BMP signaling pathways.