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Biomedical subjects

R D Ball

Publications and source records attributed to R D Ball.

11 recordsLinked to original sources
PubMed2001

Bayesian methods for quantitative trait loci mapping based on model selection: approximate analysis using the Bayesian information criterion.

We describe an approximate method for the analysis of quantitative trait loci (QTL) based on model selection from multiple regression models with trait values regressed on marker genotypes, using a modification of the easily calculated Bayesian information criterion to estimate the posterior probability of models with various subsets of markers as variables. The BIC-delta criterion, with the parameter delta increasing the penalty for additional variables in a model, is further modified to incorporate prior information, and missing values are handled by multiple imputation. Marginal probabilities for model sizes are calculated, and the posterior probability of nonzero model size is interpreted as the posterior probability of existence of a QTL linked to one or more markers. The method is demonstrated on analysis of associations between wood density and markers on two linkage groups in Pinus radiata. Selection bias, which is the bias that results from using the same data to both select the variables in a model and estimate the coefficients, is shown to be a problem for commonly used non-Bayesian methods for QTL mapping, which do not average over alternative possible models that are consistent with the data.

Alleles↗
PubMed1987

Myosin degradation fragments in skeletal muscle.

Myosin heavy chain degradation fragments produced in vivo have been identified in chicken pectoralis muscle. The fragments were identified by electrophoresis of unfractionated extracts of chicken pectoralis muscle on sodium dodecyl sulfate/polyacrylamide gels followed by immunoblotting on nitrocellulose sheets. Monoclonal antibodies directed against the S2 and light meromyosin subfragments as well as type II myosin-specific polyclonal antibodies directed against the entire myosin heavy chain were used to characterize the fragments, which range in molecular weight from approximately 80,000 to 180,000. All fragments contain the extreme carboxy-terminal portion of the molecule and are distinct from the classical proteolytic fragments such as heavy and light meromyosin, S1, S2 or rod. These fragments appear to be produced in vivo by proteolytic cleavage of peptides from the amino-terminal (S1) end of the heavy chain while the myosin molecule is still embedded in the thick filament. Fragment concentrations are estimated to be approximately 5 to 10% of that of the intact myosin heavy chain. These fragments are not the result of artifactual damage to myosin, e.g. proteolysis or hydrodynamic shear. The techniques described in this paper provide a probe into the early stages of myosin and thick filament degradation in vivo.

Animals↗
PubMed1986

Increased muscle tone during etretinate therapy.

A 40-year-old man with severe psoriasis developed painless muscle stiffness coinciding with four successive courses of etretinate therapy. Peripheral nerve block extinguished the increased muscle tone. Our patient's symptoms resembled those of the stiff-man syndrome. Increased muscle tone is a potential side effect of etretinate treatment and must be distinguished from the common musculoskeletal symptoms observed in patients taking retinoid therapy.

Adult↗
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↗
PubMed1985

Lumbosacral radiculopathy, reflex sympathetic dystrophy and tarsal tunnel syndrome: an unusual presentation.

This case documents a patient with lumbosacral radiculopathy, reflex sympathetic dystrophy, and tarsal tunnel syndrome affecting one extremity. After lumbar laminectomy for L5-S1 radiculopathy, the patient developed foot pain diagnosed as secondary to reflex sympathetic dystrophy. Because of increasing foot pain despite long-term conservative therapy, the patient underwent further evaluation, including electrodiagnostic studies leading to the diagnosis of a superimposed tarsal tunnel syndrome. Following surgical decompression, pain decreased. Because of the unusual presentation, diagnosis and treatment of the tarsal tunnel syndrome was significantly delayed. To help understand the coexistence of these conditions, interrelating pathophysiologic mechanisms have been postulated, including the possibility that a "double-crush" phenomenon may have contributed to the development of tarsal tunnel syndrome. Earlier diagnosis and definitive treatment of the foot pain may have been possible had these mechanisms been better understood.

Humans↗
PubMed1984

Abnormal neuromuscular transmission in an infantile myasthenic syndrome.

A term infant required intubation for respiratory depression. Examination revealed hypotonia and areflexia with intact extraocular movements. Electrodiagnostic studies demonstrated defective neuromuscular transmission characterized by borderline low motor evoked amplitudes, profound decremental responses at all stimulation rates, and moderate facilitation (50 to 740%) 15 seconds after 5 seconds of 50 Hz stimulation. Repetitive muscle action potential responses were not recorded following stimulation of nerves by single shocks. Sensory evoked responses and needle electromyographic findings were normal, as were acetylcholine receptor antibody levels. Results of muscle histochemical analyses, including acetylcholinesterase stains, were normal. End-plate histometric analyses demonstrated only a slight reduction in mean synaptic vesicle diameter compared with that in an adult control subject. In vitro muscle contractile properties, stimulating the muscle directly, were normal. Anticholinesterase medications were ineffective. Guanidine produced clinical deterioration. The amplitude of motor evoked responses progressively declined, whereas the percentage of decrement and amount of post-tetanic facilitation increased. Although the nature of the transmission defect was not identified, the data are consistent with abnormal acetylcholine resynthesis, mobilization, or storage without abnormality of release or receptors.

Acetylcholinesterase↗
PubMed1984

A murine model of polymyositis induced by coxsackievirus B1 (Tucson strain).

A murine model of polymyositis induced by coxsackievirus B1, Tucson strain (CVBT) is described. Intraperitoneal CVBT inoculation of CD 1 Swiss mice less than 48 hours old resulted in proximal hindquarter weakness that was first apparent 7 days after viral challenge and persisted for more than 10 weeks. Electromyographic and histologic evidence of a continuing myositis was present during this entire period of time. However, virus was not detectable later than 2 weeks post infection, despite clinical progression of disease. The finding of electromyographic and histologic abnormalities in CVBT-infected mice, long after virus had cleared and neutralizing antibody production evoked, suggests that persistent myositis may be immunologically mediated, triggered by the initial acute viral infection.

Animals↗
PubMed1977

Separation of epidermal layers of the newborn rat.

A method is presented for the separation of epidermal strata by the successive elimination of either the basal or basal and spinous cells with 0.24 M NH4Cl at pH 9.5. Histologic evidence suggests that the residual epidermal strata obtained after incubation of the skin with NH4Cl are reproducible; hence, this technique circumvents loss of granular layer histidine-rich protein inherent with trypsin separation and provides an effective procedure for biochemical analysis of arginine-rich and lysine-rich proteins in the various differentiating epidermal cells.

Ammonium Chloride↗
PubMedDate not supplied

Acoustic myography: a noninvasive monitor of motor unit fatigue.

Acoustic myography is the recording of sounds produced by contracting muscle. These sounds become louder with increasing force of contraction. We have compared muscle sounds with surface EMG to monitor the dissociation of electrical from mechanical events (presumably, the loss of excitation-contraction coupling) which occur with motor unit fatigue. Acoustic signals were amplified using a standard phonocardiograph, recorded on FM magnetic tape, and digitally analyzed. Muscles were examined at rest, with intermittent contractions, and with sustained contractions. We found that with fatigue, the acoustic amplitude decayed, but the surface EMG amplitude did not. With decreased effort, however, the acoustic and the surface EMG amplitudes declined simultaneously. By simultaneously recording acoustic signals and needle EMG, individual motor units were resolved acoustically in two muscles with decreased numbers of motor units and increased motor unit size. Fasciculations also produced acoustic signals, although no acoustic signal has yet been found that correlates with fibrillations. Analysis of acoustic signals from muscle provides a noninvasive method for monitoring motor unit fatigue in vivo. It may also be useful in distinguishing muscle fatigue from decreased volition.

Acoustics↗