Abstract-TheUse of specific adrenergic receptor knockout (KO) mice has also been useful in defining the role of ␣ 1 AR subtypes in cardiovascular regulation. [3][4][5][6] However, results in KO mice remain controversial, with each subtype contributing to regulation of blood pressure and vascular contractility but without a subtype-selective role being clearly apparent. The ␣ 1 A, B, and D AR subtypes have been shown to contribute to the maintenance of basal blood pressure and vasopressor responses to exogenous agonists. Specifically, ␣ 1A and ␣ 1D AR KO mice have lower basal blood pressure, whereas all 3 KO mice models have attenuated pressor responses to exogenous norepinephrine (NE). However, it is becoming increasingly appreciated that differential ␣ 1 AR-mediated responses may be the result of different receptor subtypes at junctional versus extrajunctional sites. 7-9 Thus, a critical and clinically relevant question in ␣ 1 AR adrenergic biology remains: is there a specific receptor subtype that mediates sympathetic transmission at the neuroeffector junction? 10 Clinical data suggest that orthostatic intolerance (OI) may result when ␣ 1B ARs are specifically inhibited. 11 Thus, we hypothesized that the ␣ 1B AR is the subtype critical in mediating vasoconstriction at the neuroeffector junction. To test the hypothesis, we measured integrated cardiovascular responses to selective carotid arterial baroreceptor unloading induced by transient bilateral carotid occlusion (TBCO) in mice with a homozygous deletion of the ␣ 1B AR gene. We also determined the vascular contractile responses in mesenteric resistance vessels in vitro to endogenous NE (mediated by electrical field stimulation [EFS]) in KO and wild-type (WT) mice.

We have created a bioimpedance probe designed to detect subtle changes in human cervical tissue composition in vivo, and thereby detect the onset of cervical remodeling in a noninvasive manner sooner than existing clinical methods allow. Our cervical bioimpedance measurement device, which can be used during a routine pelvic examination, is composed of a contoured probe with disposable tip and, within the probe's handle, a bioimpedance sensor equipped with an integrated chip capable of generating sinusoidal voltage of varying frequencies. A constant force spring assures consistent measurements through a range of contact forces applied. An activation switch allows the operator to control the application of current. The sensor can be synchronized with a computer data storage and analysis system, which interfaces with the device. With the probe placed in contact with a collagen gels of varying concentration, the relationship between measured bioimpedance and collagen concentration is verified to be positive exponential (R/sup 2/=0.94) and repeatability in saline solution showed that measurements varied by less than +/-10% over 20 trials. Finally, a variety of user-applied forces showed that impedance values plateau when forces exceed 1N.

We report on a wireless, electromyography (EMG)-based, force-measuring system developed to quantify hand-applied loads without interfering with grasping function. A portable surface EMG device detects and converts to voltage output biopotentials generated by muscle contractions in the forearm and upper arm during hand-gripping and traction activities. After amplifying and bandpass filtering, our radio frequency (RF)-based design operating at approximately 916 MHz wirelessly transmits those voltages to a data acquisition (DAQ) system up to 20 meters away. A separate calibration system is used to relate an individual user's EMG signal to known pull and clenching forces during specific applications. Real-time EMG data is processed and displayed in software developed with LabView (National Instruments, Austin, TX). Data is then converted to force data using individual calibration curves. With EMG electrodes placed over any major forearm muscle, calibration curves for seven subjects demonstrated linearity (R(2) > 0.9) and repeatability (<10% of average slope) to 110 newtons (N). Preliminary results in clinical application on newborn delivery suggest that this approach may be effective in providing an unobtrusive and accurate method of measuring hand-applied forces in applications such as rehabilitation and training.

As part of our undergraduate training in Biomedical Engineering, we have developed a series of courses, Longitudinal Design Teams, where groups of students at various levels of their education work together to solve problems at the interface of engineering and biology. The teams function under a pseudo-corporate structure which encourages the solution of practical problems through both theoretical and experimental approaches. We report on one set of IRB