Micromolar zinc potentiates neuronal nicotinic acetylcholine receptors (nAChRs) in a subtype-dependent manner. Zinc potentiates receptor function even at saturating agonist concentrations, without altering the receptor desensitization rate. Potentiation could occur through an increase in the number of available receptors, an increase in single-channel current amplitude, or an increase in single-channel open probability. To distinguish among these possibilities, we examined rat neuronal nAChRs expressed in Xenopus oocytes. Blockade of a large fraction of ACh activated α4β4 or α4β2 receptors by the open channel blocker hexamethonium failed to change the extent of potentiation by zinc, suggesting that zinc does not change the number of available receptors. The single-channel amplitudes of ACh (1 μM) activated α4β4 receptors in outside-out patches were similar in the absence and the presence of 100 μM zinc (3.0 ± 0.1 and 2.9 ± 0.1 pA, respectively). To determine the effect of zinc on single-channel open probability, we examined α4β4 receptors in cell-attached patches. The open probability at 100 nM ACh (0.011 ± 0.002) was increased 4.5-fold by 100 μM zinc (0.050 ± 0.008), accounting for most of the potentiation observed at the whole cell level. The increase in open probability was due to an increase in burst duration, which increased from 207 ± 38 ms in the absence of zinc to 830 ± 189 ms in the presence of zinc. Our results suggest that potentiation of neuronal nAChRs by zinc is due to a stabilization of the bursting states of the receptor.

Several adaptive filter structures are proposed for noise cancellation and arrhythmia detection. The adaptive filter essentially minimizes the mean-squared error between a primary input, which is the noisy ECG, and a reference input, which is either noise that is correlated in some way with the noise in the primary input or a signal that is correlated only with ECG in the primary input. Different filter structures are presented to eliminate the diverse forms of noise: baseline wander, 60 Hz power line interference, muscle noise, and motion artifact. An adaptive recurrent filter structure is proposed for acquiring the impulse response of the normal QRS complex. The primary input of the filter is the ECG signal to be analyzed, while the reference input is an impulse train coincident with the QRS complexes. This method is applied to several arrhythmia detection problems: detection of P-waves, premature ventricular complexes, and recognition of conduction block, atrial fibrillation, and paced rhythm.

Photoplethysmography (PPG) is a noninvasive optical technique for detecting microvascular blood volume changes in tissues. Its ease of use, low cost and convenience make it an attractive area of research in the biomedical and clinical communities. Nevertheless, its single spot monitoring and the need to apply a PPG sensor directly to the skin limit its practicality in situations such as perfusion mapping and healing assessments or when free movement is required. The introduction of fast digital cameras into clinical imaging monitoring and diagnosis systems, the desire to reduce the physical restrictions, and the possible new insights that might come from perfusion imaging and mapping inspired the evolution of the conventional PPG technology to imaging PPG (IPPG). IPPG is a noncontact method that can detect heart-generated pulse waves by means of peripheral blood perfusion measurements. Since its inception, IPPG has attracted significant public interest and provided opportunities to improve personal healthcare. This study presents an overview of the wide range of IPPG systems currently being introduced along with examples of their application in various physiological assessments. We believe that the widespread acceptance of IPPG is happening, and it will dramatically accelerate the promotion of this healthcare model in the near future.

A multilayered e-dermis allows a prosthesis and an amputee to perceive a range of innocuous and noxious tactile stimuli.

We present power spectral analysis of ECG waveforms as well as isolated QRS complexes and episodes of noise and artifact. The power spectral analysis shows that the QRS complex could be separated from other interfering signals. A bandpass filter that maximizes the signal (QRS complex)-to-noise (T-waves, 60 Hz, EMG, etc.) ratio would be of use in many ECG monitoring instruments. We calculate the coherence function and, from that, the signal-to-noise ratio. Upon carrying out this analysis on experimentaly obtained ECG data, we observe that a bandpass filter with a center frequency of 17 Hz and a Q of 5 yields the best signal-to-noise ratio.