Simulated feedforward neural network coordination of hand grasp and wrist angle in a neuroprosthesis.

This study presents a possible solution of the general problem of coordinating muscle stimulation in a neuroprosthesis when multiarticular muscles introduce mechanical coupling between joints. In a hand-grasp neuroprosthesis, extrinsic hand muscles cross the wrist joint and introduce large wrist flexion moments during grasp. In order to control hand grasp and wrist angle independently, a controller must take the mechanical coupling into account. In simulation, we investigated the use of artificial neural networks to coordinate hand and wrist muscle stimulation. The networks were trained with data that is easily obtained experimentally. Feedforward control showed excellent hand and wrist coordination when the properties of the system were fixed and there were known external loads. Predictable disturbances (e.g., gravity acting on the hand) can be compensated by sensing arm orientation. However, since wrist angle is sensitive to unpredictable disturbances (e.g., fatigue or object weight), voluntary intervention or feedback control may be required to reduce residual errors.

Collagen cross-links. Synthesis of immunoreagents for development of assays for deoxypyridinoline, a marker for diagnosis of osteoporosis.

(+)-Deoxypyridinoline (Dpd, 2) is a cross-link of bone collagen, which is released and excreted in urine during process of bone resorption. It has been shown that this bone collagen degradation product, Dpd (2) is a useful marker for diagnosis of osteoporosis and other metabolic bone diseases. In this paper, the design and synthesis of two immunogens (3, 4) via of conjugation of succinimidyl ester (14) to carrier protein, bovine serum albumin, or keyhole limphet hemocyanin, was presented. Additionally, fluorescent (5) and chemiluminescent (6) tracers were prepared from (-)-acid (13) via in situ activation and subsequent reaction with 6-Fln-CH(2)NH(2) (17) or Acr-NH(2) (18) and hydrolysis. The key hapten (-)-acid (13) was prepared by quaternization of 3-hydroxypyridine derivative (S,S)-(-)-11 with iodide (S)-(-)-10 followed by selective hydrolysis. These immunreagents (immunogens 3 and 4 and tracers 5 and 6) are useful for the development of sensitive and high throughput immunoassays, such as FPIA and CLIA for Dpd (2).

Inner ear barotrauma after stapedectomy in the guinea pig.

OBJECTIVE: The safety of scuba diving after stapedectomy is controversial. Stapedectomy is thought to predispose to inner ear barotrauma (e.g., perilymph fistula); however, many individuals continue to scuba dive following stapedectomy without ill effects. The purpose of this study was to evaluate the cochlear effects of barotrauma, similar to that experienced with scuba diving, on inner ears previously treated with stapedectomy. STUDY DESIGN: Prospective, controlled. METHODS: Sixteen Hartley albino guinea pigs underwent unilateral total stapedectomy followed by hyperbaric dives on 5 consecutive days, beginning 3 weeks after stapedectomy. Cochlear effects were determined using click and tone-pip evoked electrocochleographic thresholds and cochlear hair cell counts. RESULTS: Mean auditory thresholds increased by 29 dB after stapedectomy (P < .001), then remained stable thereafter. Mean thresholds in both the operated and control ears did not change with hyperbaric dives. Evidence of middle ear barotrauma (e.g., hemorrhage or tympanic membrane perforation) was observed in eight poststapedectomy ears and five control ears, but none demonstrated significant threshold elevation greater than or equal to 10 dB. Hair cell counts were not different between operated and control ears. CONCLUSIONS: Stapedectomy does not appear to predispose to cochlear sequelae in the guinea pig model of diving-related barotrauma.

Efficient synthesis of 3-aminodigoxigenin and 3-aminodigitoxigenin probes.

Oxidation of digoxigenin and digitoxigenin to the 3-ketones followed by reductive amination produced a mixture of amine epimers. The inability to separate the epimeric mixtures of chemiluminescent digoxigenin probes derived by conjugation to the acridinium label prompted us to develop an HPLC method to separate the amines. Labeling of the pure amines resulted in good yields of the isomerically pure probes.

A barbiturate screening assay for the Abbott AxSYM analyzer.

A fluorescence polarization immunoassay for barbiturates on the Abbott AxSYM analyzer is described. The assay displayed dilution linearity up to 1200 ng/mL; coefficients of variation varied from 5.96 to 8.61%; recovery varied from 94.9 to 105.3%; and sensitivity was less than 40 ng/mL. Good correlation between the standard six- and factory two-point calibration methods was observed. The Immunoassay demonstrated good cross-reactivity to several commonly prescribed barbiturates; low cross-reactivity with structurally similar compounds; low interference from endogenous substances, dyes, preservatives, and several commonly available adulterants; and good correlation with the TDx Barbiturate Urine assay.

Restoration of lateral hand grasp using natural sensors.

A closed-loop control system for controlling the key grip of a C6 tetraplegic patient was developed. Natural sensors served as the source of the feedback signal. The neural signals from cutaneous receptors were picked up by an implanted cuff electrode placed around the radial branch of the median nerve innervating the lateral part of the index finger. Mechanical stress applied to the skin, like pressure and slips, resulted in an increase in amplitude of the recorded neural signal. The goal of the study was to determine whether the recorded neural signals were able to indicate the slip of an object during lateral grasp and whether the slip could be stopped by increasing the grasp force through functional electrical stimulation of the thumb adductor and flexor.

Input-output nonlinearities and time delays increase tracking errors in hand grasp neuroprostheses.

Tracking tasks were designed to study how different input-output relationships (nonlinearities and time delays) would affect the performance of functional neuromuscular stimulation (FNS) hand grasp neuroprostheses. Simulated hand grasp neuroprostheses and real hand grasp neuroprostheses with and without closed-loop control were evaluated, with the subjects adjusting the input to the system so that the output would match a visual target track at three different bandwidths (able bodied subjects with the simulated systems and neuroprosthesis users with the real systems). For both systems, the tracking error increased as the input-output nonlinearity increased. Other factors that affected tracking performance were the target bandwidth and delays in the neuroprosthesis. The results support the hypothesis that hand grasp neuroprostheses with linear input-output properties and no delays will be controlled more accurately.