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991.
992.
The dynamics and mechanical forces generated during burrowing in Polyphysia crassa (Annelida: Polychaeta) and Priapulus caudatus (Priapulida) were investigated. Both animals live in soft marine muds and burrow by utilizing a direct peristaltic wave alternating with a high internal pressure event which thrusts the anterior part of the body into the substratum. Forces generated during the various phases of a typical burrowing cycle were measured in animals moving beneath the natural substratum at 5±3 °C using electronic transducers and recorder. During 'head' advance Polyphysia generated 0.027 N, and during 'tail' advance 0.020 N, with peak internal pressures averaging 0.95 kPa (= 0.095 N/cm2 ). Force by Priapulus during head advance and tail advance was 0.081 N and 0.121 N, respectively, with peak internal pressures averaging 2.47 kPa (= 0.247 N/cm2 ). Polyphysia moves more slowly (0.24 cm/min) than does Priapulus (0.76 cm/min) and expends more energy on mass moved per unit distance. These force measurements during a burrowing cycle were used in place of respirometry as a basis for computation of net cost of transport (NCT) for each animal. NCT for Polyphysia was 635 J kg-1 m-1 and for Priapulus was 314Jkg-1 m-l . Cost of transport for all burrowing animals thus far investigated is high compared to swimming, running and flying. For soft-bodied invertebrates that live an entirely buried existence this high cost must be interpreted in the broader context of the adaptive value of infaunal life, especially protection against predation, and not as simply a means of moving about. 相似文献
993.
This study was designed to assess the changes in fiber-type distribution of the extensor digitorum longus (EDL) muscle of the mouse during the first 21 days of age following neonatal sciatic neurectomy. Denervated and normal muscles were compared at 7, 14, and 21 days of age and the normal EDL was also studied at 1 day of age. Frozen sections of the EDL were treated histochemically to detect NADH-tetrazolium reductase and myosin ATPase reactions. Quantitative assessment included measurements of cross-sectional areas and fiber counting. Denervation resulted in muscle atrophy which was due primarily to a decrease in individual fiber area as opposed to fiber loss. Histochemical maturation of the EDL was severely affected by neonatal denervation during the first three postnatal weeks. By 21 days, two extrafusal fiber types which were both oxidative could be distinguished. One type was highly atrophied and resembled an immature fiber exhibiting myosin ATPase staining at both acid and alkaline preincubation conditions, whereas another type was less atrophied and showed myosin ATPase staining resembling fast-twitch (type IIA) fibers. These findings emphasize the importance of an intact nerve supply in determining the phenotypic expression of skeletal muscle, and point to the early postnatal period as a critical stage in fiber type differentiation. 相似文献
994.
995.
996.
997.
Abstract An investigation has been made of the resistance time and upper lethal temperature of ammocoetes of four species of lampreys provided with a substrate into which they could readily burrow. In general, ammocoetes burrowed after transfer from the acclimation to the experimental temperature baths and later came out of the substrate only in lethal temperatures. A relationship was observed between the resistance time and the time taken to emerge, with the resistance time increasing exponentially with decreasing experimental temperature. In Ichthyomyzon fossor, landlocked Petromyzon marinus, Lampetra (Lethenteron) Lamottenii and in Lampetra (Lampetra) planeri from two different times of the year, the incipient lethal levels over a two week experimental period for larvae acclimated to 15° G were respectively 30.5, 30, 29.5, 28.5 and 28° C. Values for P. marinus acclimated to 5 and 25° C were respectively 29.5 and 31° C, whereas in L. planeri they were 28 and 29° C in April/May and 27 and 29° C in July/August. Extrapolation of the results for the three acclimation temperatures yielded ultimate incipient lethal levels of 31.4° G in P. marinus and 29.2 and 29.4° C for L. planeri examined in the spring and summer respectively. 相似文献
998.
The anatomical basis for the application of neurovascular pedicled muscle transfers of the digastric and stylohyoid muscles in the treatment of velopharynx incompetence is described. The fact that the neurovascular pedicle is located in the cranial third of the muscle bellies provides the safety of the operative procedure. The muscles have to be dissected with respect to that. The direction in which the transferred muscles pull is described. The muscle transposition is combined with the classic Wardill-Kilner operation to lengthen the soft palate. The transferred muscles have to avoid scar contraction and shortening of the soft palate and to gain a muscular function of the soft palate. The clinical use is justified in rare cases as demonstrated in one case. 相似文献
999.
A Schellenberger I Heinroth G Hübner 《Hoppe-Seyler's Zeitschrift für physiologische Chemie》1967,348(5):506-511
1000.
The sensitivity of the fluorescent dye, 3,3′-diethylthiadicarbocyanine (DiS-C2(5)), was too low for the detection of membrane potential changes in rat small intestinal membrane vesicles. Only after adding LaCl3 or after fractionation of the intestinal membranes by free-flow electrophoresis could the dye be used to monitor electrogenic Na+-dependent transport systems. It is concluded that the response of this potential-sensitive dye is influenced by the negative surface charge density of the vesicles. 相似文献