Search PubMed⌕ Search

Biomedical subjects

D Ottoson

Publications and source records attributed to D Ottoson.

At least 37 records · Page 2Linked to original sources
PubMed1971

The contribution of mechanical factors to the early adaptation of the spindle response.

1. Adaptation in terms of the early fall of the receptor potential was studied in isolated frog spindles. The contribution of gross mechanical changes to the decline of the response was determined by comparing the responses obtained under constant length and under constant tension.2. It was found that the early adaptation under constant stretch increased with increasing lengthening of the spindle for stretches up to 25-30% of the resting length and decreased with still stronger stretches. When the spindle was stretched by 100% or more the static phase of the receptor potential reached nearly the same height as the dynamic peak and the early adaptation approached zero.3. The early adaptation decreased with decreasing velocity of linearly rising stretch and approached zero for stretches below about 0.5 mm/sec.4. For different strengths of a steplike stretch the amount of early adaptation was linearly related to the fall in tension over the same period. The relative amount of tension fall, however, was always less than the corresponding fall of the response.5. The early adaptation was 15-20% smaller under constant tension than under constant length for stretches below the level giving the maximum dynamic peak.6. The results suggest that a comparatively small amount of the early adaptation of the spindle response to constant stretch is related to gross alterations in length in different regions of the spindle. The main part of the adaptive fall of the response is probably related to functional properties of the sensory membrane and to the ionic mechanism underlying the production of the receptor potential.

Adaptation, Physiological↗
PubMed1971

Ionic effects on spindle adaptation.

1. Effects of changes in ionic environment on the receptor potential were studied in isolated frog spindle. Particular attention was focused on the action of potassium removal on the early adaptive decline of the response.2. Removal of potassium caused a reduction and final disappearance of the dynamic overshoot of the receptor potential. The static phase of the response was also reduced although to less extent. The repolarization phase of the response following release of phasic or maintained stretch was greatly prolonged.3. Increased potassium concentration caused a reduction of the response, but did not change its general time course. The amount of reduction was related to the potassium concentration.4. Removal of sodium caused a marked diminution of the response, the static phase being in general more affected than the dynamic phase.5. It is suggested that the effects of potassium removal are caused by a delay in sodium inactivation and a partial depolarization of the endings. It is concluded that the greater part of the early adaptation of the spindle proper may be attributed to ionic mechanisms in the transducer membrane.

Animals↗
PubMed1970

Length changes within isolated frog muscle spindle during and after stretching.

1. The length changes within the frog muscle spindle during stretch have been studied by stroboscopic photomicroscopy. Attention was focused on the length changes within the central reticular zone and these changes were related to the features of the receptor potential.2. It was found that the length changes of the central reticular zone closely followed the applied stretch in time course and magnitude. The results suggest that the length changes of the polar zones are generally similar to those in the central zone.3. There was no evidence of a relative shortening of the central zone in the early phase of maintained stretch, corresponding to the decline of the receptor potential from its dynamic peak to the static level.4. Following release of stretch the central zone returned to its original resting length within a few msec. The rapid return of the spindle was in sharp contrast to the relatively slow exponential decay of the receptor potential. With strong or prolonged stretches the return became slower and resting length was not completely restored until 100-150 msec after release of stretch. No corresponding change in the decay of the receptor potential was seen.5. The results suggest that the early adaptive fall of the receptor potential is not related to differential length changes between the central zone and the polar zones. It seems more likely that the contribution of mechanical factors to the early adaptation of the frog spindle have to be sought at the ultrastructural level.6. The finding that the length changes closely follow the applied stretch suggests that the stimulus in terms of lengthening is transmitted to the endings with little distortion.7. The results suggest that the elastic elements play a dominant role for the transmission of the stimulus to the endings and for the return of the spindle to resting length after release of stretch.

Action Potentials↗