Automatic capture verification by charge-neutral sensing.

Automatic capture verification can prolong pulse generator longevity and increase patient safety. However, the detection of evoked response following pacing is complicated due to afterpotentials caused by polarization of electrodes. This study describes a new capture verification scheme, which neutralizes the charges between the pacing electrodes.

Properties of single motor units in medial gastrocnemius muscles of adult and old rats.

1. The purpose of this study was to determine the role of motor unit remodelling in the deficit that develops in the maximum isometric tetanic force (Fo) of whole medial gastrocnemius (MGN) muscles in old compared with adult rats. The Fo values and morphological data were determined for MGN muscles and eighty-two single motor units in muscles of adult (10-12 months) and sixty-two units in those of old (24-26 months) F344 rats.

Tubular nerve guide and epineurial repair: comparison of techniques for neurorrhaphy.

Experiments were conducted on 36 male, Sprague-Dawley rats. In 10 animals, neurorrhaphy was performed on the peroneal nerve with epineurial repair and, in 11 animals, with a tubular polyethylene nerve guide. The authors tested the hypothesis that, following transient denervation of a skeletal muscle by transection of a peroneal nerve, the restoration of maximum force and of maximum specific force developed after insertion of a tubular nerve guide, will not be different from that developed after microsurgical epineurial neurorrhaphy.

Review: Whole skeletal muscle transplantation: mechanisms responsible for functional deficits.

One aspect of tissue engineering of skeletal muscle involves the transposition and transplantation of whole muscles to treat muscles damaged by injury or disease. The transposition of whole muscles has been used for many decades, but since 1970, the development of techniques for microneurovascular repair has allowed the transplantation of muscles invariably result in structural and functional deficits. The deficits are of the greatest magnitude during the first month, and then a gradual recovery results in the stabilization of structural and functional variables between 90 and 120 days.

Tenotomy and repair of latissimus dorsi muscles in rats: implications for transposed muscle grafts.

The functional properties of latissimus dorsi (LTD) muscles were evaluated 160 to 180 days after tenotomy and repair, when grafts had stabilized. Our hypothesis was that, compared with control LTD muscles, LTD grafts would develop less absolute force and power but that the specific force and normalized power would not differ. Expressed as a percentage of the value for control LTD muscles, values for grafts were 67% for muscle mass, 74% for mean single fiber cross-sectional area, 56% for maximum absolute isometric tetanic force, 64% for maximum absolute average force during shortening, and 70% for maximum absolute power.

An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarflexors of mouse ankle.

We developed an apparatus to quantify the biomechanical behavior of the dorsi- and plantarflexor muscles of the ankle of an anesthetized mouse. When the dorsi- or plantarflexor muscle group is activated by electrical stimulation of either the peroneal or tibial nerve, the apparatus measures the moment developed about the ankle during isometric, isovelocity shortening, or isovelocity lengthening contractions. Displacements may be performed over the full 105 degrees range of ankle motion with an angular resolution of 0.

A simple Hill element-nonlinear spring model of muscle contraction biomechanics.

The purpose of this study was to develop a model to predict the mechanical response of muscles during isometric tetanic, afterloaded isotonic and isovelocity shortening contractions. Two versions of the model were developed. Both incorporated a contractile element that obeyed a Hill force-velocity relationship and a series elastic element.