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Biomedical subjects

D T Barry

Publications and source records attributed to D T Barry.

At least 37 records · Page 2Linked to original sources
PubMed1988

Acute somatic pain can refer to sites of chronic abdominal pain.

We report a case of a latissimus dorsi muscle strain that presented as a recurrence of chronic abdominal pain. One explanation of the referral of acute pain to a site of chronic pain is the convergence-projection theory, which hypothesizes that pain signals of visceral and somatic origin converge at some point in the sensory pathway. Upon reaching the cortex, these signals are interpreted as coming from the afferents which have previously excited this pathway. In this case an extensive gastrointestinal diagnostic evaluation was pursued unsuccessfully before the latissimus dorsi muscle strain was diagnosed. Outpatient therapy of spray and stretch combined with a home stretching program produced a prompt and persistent resolution of the symptoms.

Abdomen↗
PubMed1987

Acoustic signals from frog skeletal muscle.

Acoustic, force, and compound muscle action-potential signals were recorded simultaneously during maximal isometric twitches of frog gastrocnemius muscles. The onset of sound production occurred after the onset of muscle depolarization but before the onset of external force production. Acoustic waveforms consisted of oscillations that initially increased in amplitude, followed by decaying oscillations. The peak-to-peak acoustic amplitude increased with increasing temperature with a Q10 of 2.6 +/- 0.2 over a range of 7.0-25.0 degrees C. The acoustic amplitude increased with increasing muscle length up to approximately 90% of the optimal length for force generation. As length was increased further, the acoustic amplitude decreased. Microphones positioned on opposite sides of the muscle recorded acoustic signals that were 180 degrees out of phase. These results provided evidence that sound production is produced by lateral oscillations of muscle. The oscillation frequency may provide a measure of mechanical properties of muscle.

Action Potentials↗
PubMed1987

Objective evaluation of grip strength.

The objective and subjective components of industry-related injuries can lead to difficulties in diagnosis and treatment efforts. Grip strength determinations provide an objective measure that facilitates the evaluation of many occupation-related injuries. In this current study, healthy volunteers were evaluated with standard grip strength measurement and electromyographic recordings in order to characterize normal patterns. These recordings were found to be relatively uniform and reproducible.

Disability Evaluation↗
PubMed1986

Acoustic myography as a control signal for an externally powered prosthesis.

Contracting skeletal muscle produces sounds that are easily recorded with a standard microphone. The recording of these sounds is known as acoustic myography, or AMG. As a control signal for an externally powered prosthesis, some advantages of AMG over surface EMG are: there is no need for direct skin contact; the AMG signal is unaffected by changes in skin impedence; AMG intensity is high enough to produce a 50 mV output from a standard microphone, requiring less amplification and electrical shielding; the AMG signal is qualitatively less sensitive to placement on the muscle than EMG. Disadvantages, such as the susceptibility of AMG to interference by extraneous environmental noise, are relatively easy to overcome. To demonstrate this, we have constructed a myoacoustically controlled prosthetic hand, whose tristate control via a single microphone (vs differential control) proves its feasibility in the more difficult case. The control circuitry for this device costs less than $50. The existing device utilizes a free-standing hand; a prosthetic shell which will allow comparison of AMG vs EMG control is currently being designed. The two patients who have tried it have learned to open and close the hand reliably after only three minutes of practice. Protocols are being established for functional assessment of AMG control.

Acoustics↗
PubMed1982

X-ray diffraction analysis of wet isolated bovine rod outer segment disks. A dehydration study.

Sequences of X-ray diffraction patterns were obtained from dehydrating, artificially oriented multilayers of isolated, bovine rod outer segment disks. A direct-phase analysis was applied to highly hydrated specimens to determine sequences of low resolution (approx. 30 A) electron density profiles of the disks as dehydration proceeded. The profiles were found to evolve smoothly as the multilayer lattice simultaneously shrank and became increasingly ordered. The bilayer profiles were largely invariant under dehydration and the evolution of the diffraction consistent with simple decreases in fluid spacings. The specimens were observed to phase separate into characteristic primary and a secondary lattices when the multi-layer became too dehydrated. The small unit cell size of the secondary lattice was suggestive of a lipid phase. Large changes in the diffraction patterns from phase separated specimens were observed upon bleaching of the specimen. The changes were consistent with a reversible disordering of the primary lattice.

Animals↗
PubMed1980

Locating spike-initiating or spike-entry zones in a branched molluscan neuron.

A theoretical method for locating spike-initiating or spike-entry zones within a single neuron was experimentally verified using the cell RPI in the marine opisthobranch Navanax inermis. Multiple sites of spike-initiation were found to exist in RPI. Furthermore, it was demonstrated that extracellular recording alone was sufficient to map sections of cells' branching patterns and possibly locate multiple spike-initiating zones.

Animals↗