Battery powered BION FES network

The Alfred Mann Foundation is completing development of a coordinated network of BION microstimulator/sensor (hereinafter implant) that has broad stimulating, sensing and communication capabilities. The network consists of a master control unit (MCU) in communication with a group of BION implants. Each implant is powered by a custom lithium-ion rechargeable 10 mW-hr battery. The charging, discharging, safety, stimulating, sensing, and communication circuits are designed to be highly efficient to minimize energy use and maximize battery life and time between charges. The stimulator can be programmed to deliver pulses in any value in the following range: 5 microA to 20 mA in 3.3% constant current steps, 7 micros to 2000 micros in 7 micros pulse width steps, and 1 to 4000 Hz in frequency. The preamp voltage sensor covers the range 10 microV to 1.0 V with bandpass filtering and several forms of data analysis. The implant also contains sensors that can read out pressure, temperature, DC magnetic field, and distance (via a low frequency magnetic field) up to 20 cm between any two BION implants. The MCU contains a microprocessor, user interface, two-way communication system, and a rechargeable battery. The MCU can command and interrogate in excess of 800 BlON implants every 10 ms, i.e., 100 times a second.

The development and application of wireless capsule endoscopy

The introduction of the Video Capsule Endoscope (VCE) by Given Imaging Ltd. (Yoqneam, Israel) in 2001, and its subsequent approval by the FDA as a first line tool in the detection of abnormalities of the small bowel, is indicative of the rapid acceptance of capsule endoscopy by the practicing gastroenterological community. An extensive clinical trials program consistently revealed a high diagnostic yield of the VCE when compared to other diagnostic modalities of the small intestine. The capsule endoscope contains a miniature color video camera, illumination sources, lens, transmitter/controller, antenna, and a power source. It is small enough to easily swallow (11 x 26 mm), and it is propelled through the gastrointestinal (GI) tract by peristalsis. Its development was enabled by a series of technological breakthroughs that occurred at the close of the 20th century. The VCE is one of the most exciting examples of the recent trend for minimally invasive autonomous medical tools in diagnostic, monitoring, and therapeutic applications. Expanding applications of the VCE to additional parts of the GI tract, adding physiological sensors, and--in the more remote future--addition of therapeutic capabilities will likely occur as this new branch of endoscopy develops.

A randomized trial comparing wireless capsule endoscopy with push enteroscopy for the detection of small-bowel lesions

BACKGROUND & AIMS

Wireless capsule endoscopy is a new, painless method of imaging the entire small bowel. It has not been compared with push enteroscopy. We compared the sensitivity, specificity, and safety of capsule and push enteroscopy in detecting small-bowel lesions.

METHODS

Nine to 13 radiopaque, colored beads (3-6 mm diameter) were sewn in random order inside 9 canine small bowels, half within the first meter, and confirmed on x-ray. After recovery, the number, order, and color of beads were assessed in 23 capsule enteroscopies and 9 push enteroscopies in a random order. The surgeons, push enteroscopists, capsule video interpreters, and pathologist were blinded to the others' findings.

RESULTS

The capsules identified more beads than push enteroscopy (median, 6 [range, 2-9] vs. 3 [range, 2-6 beads]; P < 0.001). The sensitivity of the capsule was 64% compared with 37% for push enteroscopy. The specificity was 92% for capsule enteroscopy and 97% for push enteroscopy. The capsules identified significantly more beads beyond the reach of the push enteroscope (median, 4 [range, 2-7] vs. 0; P < 0.0001). Hair, ingested plastic, ulceration, submucosal swelling, and worms were clearly identified by the capsule. The capsules passed safely through the animals with no significant histologic findings.

CONCLUSIONS

Wireless capsule endoscopy detected more abnormalities in the small bowel than push enteroscopy.

Mechanism of Ca++ release from the sarcoplasmic reticulum: a computer model

The proposed model describes myocyte calcium (Ca++) cycling, emphasizing the kinetics of sarcoplasmic reticulum (SR) Ca++ release channels. The suggested SR channel regulating mechanism includes two types of Ca++ binding sites: (1) low affinity sites with high binding rates, regulating the opening of Ca++ channels and (2) high affinity sites with low binding rates, which regulate their closing. The amount of Ca++ released from the SR and the peak value of Ca++ ion concentration [Ca++] in the cytoplasm were found to depend on the rate of the increase of [Ca++], similar to Ca++ induced Ca++ release experiments. The model describes spontaneous release of Ca++ from overloaded SR. The dependence of the control mechanism on the activating and inactivating sites is substantiated by simulations of ryanodine intervention, providing results similar to experimental results. Simulations under conditions of isolated SR vesicles produced Ca++ release results similar to measured data. Consequently, it is suggested that the recovery of Ca++ release channels represents the rate limiting factor in the process of mechanical restitution.

A model of Ca2+ release from the sarcoplasmic reticulum

Various functions in the myocyte depend on Ca2+ transport, yet the control of these processes is still obscure. In order to better understand the intracellular Ca2+ processes, a model of Ca2+ release from the cardiac sarcoplasmic reticulum (SR) is suggested, in which the release of Ca2+ from the SR is mainly regulated by the kinetics of Ca2+ channels within the SR membrane. These kinetics are controlled by changes in the concentration of free Ca2+ near the openings of Ca2+ channels, and are affected by Ca2+ competitors, e.g., ryanodine. The control mechanism is based on a combination of positive and negative control loops, associated with two respective types of Ca2+ binding sites located on the SR membrane: 1) activating sites with low affinity to Ca2+ and high binding rate, and 2) inactivating sites with high affinity but low binding rate. The model also assumes that the activation of the Ca2+ channels depends on the preceding stimulation pattern (short term memory), an additional activation mechanism which is Ca2+ independent. This report describes the cytoplasmatic Ca2+ concentration in response to Ca2+ release from the SR, including the dependence on the beat intervals, either in the steady state or during response to premature and delayed beats. The analysis of ryanodine intervention supports a control mechanism based on two feedback loops, and available interval-dependent data favors inclusion of the short-term memory mechanism in the proposed model.