[Show abstract][Hide abstract] ABSTRACT: Vascular smooth muscle cells (SMCs) play an important role in vascular remodeling. Heterogeneity and phenotypic changes in SMCs are usually accompanied by a morphological difference, i.e., elongated/spindle-like versus spread-out or epithelioid/rhomboid cell shapes. However, it is not known whether the cell shape directly regulates SMC proliferation, and what the underlying mechanisms are. In this study, microgrooves and micropatterned matrix islands were used to engineer the cell shape and investigate the associated biophysical and biological mechanisms. Compared to spread-out SMCs on nonpatterned surfaces, SMCs on micropatterned surfaces demonstrated elongated morphology, significantly lower cell and nucleus shape indexes, less spreading, a lower proliferation rate, and a similar response (but to a lesser extent) to platelet-derived growth factor, transforming growth factor-beta, and mechanical stretching. DNA microarray profiling revealed a lower expression of neuron-derived orphan receptor-1 (NOR-1) in elongated SMCs. Knocking down NOR-1 suppressed DNA synthesis in SMCs, suggesting that NOR-1 is a mediator of cell elongation effects. Regulation of DNA synthesis in SMCs by the cell shape alone and a decrease in DNA synthesis in the case of small cell spreading area were achieved by micropatterning SMCs on matrix islands of different shapes and spreading areas. Changes in the cell shape also affected the nucleus shape, whereas variations in the cell spreading area modulated the nucleus volume, indicating a possible link between nucleus morphology (both shape and volume) and DNA synthesis. The findings of this investigation provide insight into cell shape effects on cell structure and proliferation, and have direct implications for vascular pathophysiology.
[Show abstract][Hide abstract] ABSTRACT: This paper discusses the development of a multidirectional force sensor for the investigation of the flight dynamic of a tethered fly. The proposed sensor combines the well-understood concepts of piezoresistive force sensing with a unique design that allows for the measurement of forces with more than one degree of freedom (DOF). In addition, the system has been fabricated to support the fly inside a virtual reality arena. The sensor is fabricated on a wafer-level using standard MEMS technology, By directly measuring the thrust, lift, yaw and side slip generated by the fly, complex aerodynamics mechanisms due to rapidly rotating and flapping wings can be better understood.
Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005