Contractile properties of fast muscle preparations regenerating in slow muscle beds.

Mechanical evidence is presented to show that fast muscle tissue regenerating in the bed of a slow muscle, and innervated by the slow muscle nerve, has contractile properties identical to those of a slow muscle regenerating in its own bed. The results do not support the idea that regenerating fast muscles are partially resistant to the transforming effects of a slow nerve.

Repositioning of fast and slow skeletal muscle.

The origins of the rat fast plantaris and slow soleus muscles were surgically reversed and their fibre types and contractile properties examined in vitro up to 12 weeks post surgery. Muscles in which the origins had been severed and then immediately sutured back in place served as one control group. Unoperated animals served as a second control group.

Mechanical properties of tenotomized and denervated-tenotomized muscles.

Mechanical properties of rat soleus and plantaris muscles were studied in vitro following tenotomy, denervation, or tenotomy plus denervation, all of 3 wk duration. Controls included muscles from sham-operated animals and from animals with muscle tendons severed but immediately resutured. Results of twitch times, times to peak tension, and times to half-relaxation for 145 muscles clearly showed that the slight increase in muscle speed that occurs in the soleus muscles only is due to severance of the muscle tendon per se and not related to muscle shortening and possible related alterations in muscle spindle activity that occurs in simple tenotomy.

Persisting structural abnormalities in liver, kidney, and muscle tissues following hemorrhagic shock.

Hemorrhagic shock-induced abnormalities of liver, kidney, and muscle morphology were studied sequentially for eight days following shock and resuscitation in rabbits. The findings revealed marked structural changes, some of which became more pronounced between one and three days after shock and all of which persisted for at least three days. All of the tissue changes reverted to near normal by eight days.

The effects of chronic alcohol ingestion in mice on contractile properties of cardiac and skeletal muscle: a comparison with normal and dehydrated-malnourished controls.

In vitro isometric contractile tension was measured in heart and skeletal muscle in 3 groups of mice: 1. a control group, 2. a group maintained for 27 weeks on 20% alcohol, and 3.

Z disc ultrastructure in scutal depressor fibers of the barnacle.

The ultrastrlucture of Z discs in nonglycerinated, striated muscle fibers of the barnacle Balanus nubilus Darwin was examined in contracted, resting, and stretched preparations. At all sarcomnere lengths, the Z discs are perforated sheets comprised of "Z rimns" and "Z perforations," extending continuously across the myofibril; the dimensions of the rims and perforations change with changes in sarcomere length. Accordingly, with shortening of the sarcomere, there was an accompanying decrease in the transverse width of the Z rims and an increase in the diameter of the Z perforations.