Characteristics of lengthening contractions associated with injury to skeletal muscle fibers

Lengthening (eccentric) contractions result in injury to skeletal muscle fibers. Two hypotheses were tested through lengthening contractions of an in situ muscle preparation: the extent of injury increases with increases in the duration; and the extent of injury increases with increases in the peak force. Mice were anesthetized, and distal tendons of the extensor digitorum longus muscles were attached to a servomotor. Muscles were stimulated at 150 Hz and lengthened 20% of fiber length (Lf). Lengthening contractions were performed at 0.2, 0.5, or 1.0 Lf/s with durations of 0.5-15 min. Peak force during lengthening contractions at 1.0 Lf/s was decreased by inducing fatigue with isometric contractions, stimulating at 70-100 Hz, or 3) lengthening 10% of Lf. Injury was assessed 3 days after lengthening contractions by histological appearance and maximum force (Po) development. Injury increased with duration up to 5 min. After 5 min, fatigue appeared to prevent further injury. Results for 0.2 and 0.5 Lf/s were similar to those for 1.0 Lf/s but with less injury. A high correlation was observed between histological appearance of injury and the decrease in Po. The extent of injury was related to the peak force developed during the lengthening contractions.     

Sexual, seasonal and tissue variation in the encystment of Cotylurus variegatus metacercariae in perch, Perca fluviatilis

All of the 267 perch sampled from Lough Neagh between 1981 and 1983 were infected with the metacercarial cysts of Cotylurus variegatus. Sites of infection were the swim-bladder, pericardium, septum transversum and, to a lesser extent, the visceral cavity. The swim-bladder, particularly the anterior portion, was the site of heaviest infection. Visceral cysts were found chiefly in female fish and this may be related to reduced immunological defence and/or thinner body wall during the breeding season. The number of cysts recorded was not related to host length, suggesting that further parasite invasion is offset by cyst mortality possibly as a result of the host immunological response to the parasite. Highest mean worm burden was recorded between May and June. This corresponded to increased water temperature necessary for development of eggs and the breeding season (April-June) of the perch.     

Prehistoric parasitism in Tennessee: evidence from the analysis of desiccated fecal material collected from Big Bone Cave, Van Buren County, Tennessee

Eight samples of desiccated human feces collected from Big Bone Cave (40VB103), Van Buren County, Tennessee, were analyzed to determine the presence of ecto- and endoparasitic infection among the prehistoric population using the cave. Radiocarbon-dated torch material from the cave indicated that it was a locus of human activity 2,177 +/- 145 yr ago. Parasitic species identified were: Ascaris lumbricoides, Enterobius vermicularis, fleas of the tribe Phalacropsyllini, and protozoan cysts. The cysts were identified as Giardia using an indirect immunofluorescent antibody test. The only report of Giardia in a prehistoric context is the identification of cysts in 2 1,800-yr-old paleofecal specimens from a cave in Israel. This is the first report of Giardia from paleofeces in the New World.