Volume changes of the myosin lattice resulting from repetitive stimulation of single muscle fibers
Authors: Rapp, G; Ashley, CC; Bagni, MA; Griffiths, PJ; Cecchi, G
Single muscle fibers at 1 degrees C were subjected to brief tetani (20 Hz) at intervals of between 20 s and 300 s over a period of up to 2 h. A band lattice spacing increased during this period at a rate inversely dependent on the rest interval between tetani. Spacing increased rapidly during the first 10 tetani at a rate equivalent to the production of 0.04 mOsmol.liter(-1) of osmolyte per contraction, then continued to expand at a much slower rate. For short rest intervals, where lattice expansion was largest, spacing increased to a; limiting value between 46 and 47 nm (sarcomere length 2.2 mu m), corresponding to accumulation of 30 mOsmol.liter(-1) of osmolytes, where it remained constant until repetitive stimulation was terminated. At this limiting spacing, force was reduced by up to 30%. The effect of lattice swelling on the lattice compression that accompanies isometric force recovery from unloaded shortening was to increase the compression, similar to that observed in hypotonic media at a similar spacing. During recovery from repetitive stimulation, spacing recompressed to its original value with a half-time of 15-30 min. These findings suggest that mechanical activity produces an increase in osmotic pressure within the cell as a result of product accumulation from cross-bridge and sarcoplasmic reticulum ATPases and glycolysis.
Generalized Tetanus in a Gyrfalcon (Falco rusticolus) with Pododermatitis
Authors: Beaufrere, Hugues; Laniesse, Delphine; Stickings, Paul; Tierney, Robert; Sesardic, Thea; Slavic, Durda; Compo, Nicole; Smith, Dale A.
A 2-yr-old male gyrfalcon (Falco rusticolus) was presented for severe and generalized muscle spasticity and pododermatitis. The falcon had been treated for pododermatitis over the previous 4 mo. Muscle rigidity and spasms involved the entire bird but were more severe on the right leg. The bird was also tachypneic and hyperthermic at 45 C. While the plantar pododermatitis lesions had healed, there was still a small abscess on the lateral aspect of the right foot. Clinical signs were consistent with tetanus. Several bacteria were isolated from the abscess including Clostridium tetani. The isolate was confirmed to be toxigenic by PCR. Attempts to detect tetanus toxin in the bird's plasma were unsuccessful. The abscess was debrided. The gyrfalcon received equine tetanus antitoxin, intravenous metronidazole, methocarbamol, midazolam, a constant-rate infusion of Fentanyl, active cooling, and supportive care. Inhalant anesthesia with isoflurane was the only treatment that would lower the body temperature and reduce the clinical signs. The gyrfalcon died a few hours after admission. The characteristic clinical signs and isolation of toxigenic C. tetani from a wound were strong supportive evidence for a diagnosis of tetanus. This case constitutes the first reported natural occurrence of tetanus in an avian species. Further information is needed to determine whether gyrfalcons are more susceptible to tetanus than are other avian species and whether pododermatitis lesions may be risk factors.