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Biomedical subjects

T E Milner

Publications and source records attributed to T E Milner.

62 records · Page 4Linked to original sources
PubMed1987

Long-term peripheral nerve and muscle recordings from normal and dystrophic mice.

A method for long-term recording of electrical activity from small mammalian nerves and muscles is described. Electrodes for stimulating and recording activity were implanted on nerves and muscles subserving ankle flexion and extension in normal and dystrophic mice. Activity was monitored on a regular basis for up to 200 days following implantation. Neural compound action potentials, compound EMG potentials and twitch tension were recorded. Shortly after implantation, evoked EMG and twitch tension declined, but recovered progressively to values measured at the time of implantation and subsequently remained steady in normal mice. However, while dystrophic mice did recover, with EMG levels reaching 50-60% of the values recorded at implantation, tension eventually dropped to 10% in flexor muscles and 25% in extensors.

Action Potentials↗
PubMed1986

Judgment and control of velocity in rapid voluntary movements.

Control of velocity in rapid flexion movements of the interphalangeal joint of the thumb was investigated by examining movement trajectories and patterns of activity in the extensor pollicis longus (EPL) and flexor pollicis longus (FPL) muscles. Although velocity was controlled with considerable accuracy, it was not sensed with the same precision. Consistent errors were made when subjects attempted to match the peak velocities under conditions in which the relationship between muscle activity and joint acceleration had been altered, i.e. changing the angle from which movement was initiated or varying the load. Rather than relying on afferent feedback from peripheral sensory receptors for information about velocity during rapid movements, it is suggested that subjects were more likely to base their judgment of velocity on sensations evoked by the voluntary motor command.

Adult↗
PubMed1986

Controlling velocity in rapid movements.

It has often been reported that subjects prefer to use a strategy in which they vary movement velocity and peak amplitude in a linear fashion. In this study, control of velocity and amplitude in rapid reciprocating movements of the interphalangeal joint of the thumb was investigated by examining movement trajectories and patterns of activity in the extensor pollicis longus (EPL) and flexor pollicis longus (FPL) muscles. In controlling either amplitude or peak flexion velocity without constraint, subjects always used a strategy in which peak extension velocity and peak flexion velocity had strong linear correlations with movement amplitude. When they were required to keep either amplitude or peak flexion velocity fixed their movements were still biased toward a strategy in which peak velocity and movement amplitude covaried. It is suggested that the preferred strategy is related to a basic principle of scaling the magnitude and duration of a velocity profile in order to achieve different movement amplitudes.

Journal Article↗
PubMed1981

Improved estimates of conduction velocity distributions using single unit action potentials.

Single unit potentials were recorded from sural and medial gastrocnemius nerves. Action potential amplitude, integrated area and half-width (duration) were approximately proportional to conduction velocity, raised to the powers 1.5, 1 and -0.5 respectively with the sural nerve, and 2, 1.5 and -0.5 for the medial gastrocnemius nerve. These empirical relationships were applied to the computation of whole nerve conduction velocity distributions based on the relative number of single unit potentials of various conduction latencies required to reconstruct a recorded compound action potential. Conduction velocity distributions, which were converted to fibre diameter distributions, were in close agreement with the corresponding distributions determined histologically.

Action Potentials↗
PubMed1981

The effects of axotomy on the conduction of action potentials in peripheral sensory and motor nerve fibres.

Medial gastrocnemius and sural nerves in one hindlimb of the cat were transected and prevented from regenerating. After periods ranging from 29-273 days, compound action potentials were recorded from axotomised and contralateral control nerves. The amplitude and integrated area of action potentials decreased and conduction velocity slowed following axotomy. The area under compound action potentials generated by stimulating sensory fibres declined significantly faster than that generated by stimulating motor fibres. Analysis of changes in whole nerve conduction velocity distributions showed that the velocities of fast conducting sensory fibres decreased at the most rapid rate. The conduction velocities of motor fibres and slow sensory fibres declined at significantly slower rates. The loss of electrical activity in the largest sensory nerve fibres following axotomy, may play a role in determining the faster rate at which their action potentials deteriorate.

Action Potentials↗
PubMedDate not supplied

Feedback-controlled laser-mediated cartilage reshaping.

OBJECTIVE: To demonstrate feedback-controlled laser-mediated cartilage reshaping using dynamic measurements of tissue optical properties and radiometric surface temperatures. DESIGN: Flat cartilage specimens were reshaped into curved configurations using a feedback-controlled laser device. MATERIALS: Fresh porcine nasal septum, stripped of perichondrium and cut into uniform strips (25 x 10 x 1.5-2.1 mm) with a custom guillotine microtome. INTERVENTIONS: Cartilage specimens secured in a cylindrical reshaping jig (2.5 cm in diameter) and irradiated with an Nd:YAG laser (lambda = 1.32 microns, 25 W/cm2, 50-Hz pulse repetition rate). During laser irradiation, radiometric surface temperature was measured along with changes in forward-scattered light from a diode probe laser (lambda = 650 nm, 5 mW), using a lock-in detection technique. Sequential irradiation of the specimen outer surface was made (3 laser passes). Characteristic changes in tissue temperature and light-scattering signals were used to terminate laser irradiation. RESULTS: Effective reshaping was accomplished for both thin (1.5-mm) and thick (2.1-mm) specimens. Following reshaping, specimens were stored in saline solution at 4 degrees C for 21 days. No return to the original flat configuration was noted during this period. CONCLUSIONS: The prototype device effectively reshapes flat native porcine cartilage into curve configurations. The use of optical and thermal signals provides effective feedback control for optimizing the reshaping process.

Animals↗
PubMedDate not supplied

Angioresistance of thermally modified cartilage grafts in the chick chorioallantoic membrane model.

BACKGROUND: The chick chorioallantoic membrane (CAM) model allows direct observation of vascularization acutely in explanted or cultured tissues in an immunologically isolated environment. In vivo, angioinvasion of the tissue matrix does not occur in viable cartilage tissue, whereas denatured or nonviable grafts are readily vascularized and/or resorbed. OBJECTIVE: To determine, using the CAM model, whether angioinvasion of thermally altered cartilage explants occurs acutely. MATERIALS AND METHODS: Porcine septal cartilage specimens were removed from freshly killed animals and divided into 3 groups (n = 10): an untreated control group, a group in which cartilage was boiled in isotonic sodium chloride solution (normal saline) for 1 hour, and a laser-irradiated group (Nd:YAG, lambda = 1.32 microm, 30.8 W/cm2, irradiation time = 10 seconds). Tissue specimens were then washed in antibiotic solutions, cut into small cubes (approximately 1.5 mm3), placed on the surface of 30 CAMs (7 days after fertilization), and allowed to incubate for an additional 7 days. After incubation, the membranes and specimens were fixed in situ with formaldehyde and then photographed using a dissection microscope. RESULTS: Examination with a dissecting microscope showed no obvious vascular invasion of the cartilage or loss of gross tissue integrity in any of the 3 experimental groups, although all specimens were completely enveloped by the CAM vascular network. No vascular invasion of the tissue matrix was observed histologically. CONCLUSION: These experiments demonstrate that cartilage specimens remain acutely resistant to angioinvasion or metabolism by the immunologically immature CAM whether native unmodified tissue, completely denatured (boiled), or thermally modified following laser irradiation.

Allantois↗