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Muscle strains, frequently the result of a lengthening contraction, sometimes are treated with corticosteroids. We tested whether an injection of dexamethasone administered soon after muscle injury would minimize inflammation and facilitate the recovery of contractile tension. We applied one eccentric contraction on the tibialis anterior of 76 rats, which were randomly assigned to one of three groups: sham-injured plus dexamethasone, injured plus vehicle, and injured plus dexamethasone. Electrophysiology, histology, and reverse transcription-polymerase chain reaction were used to study the relation between contractile tension, inflammation, and the expression of inflammatory molecules. The single eccentric contraction led to a reversible muscle injury characterized initially by reduced contractile tension and inflammation. The dexamethasone injection reduced the expression of interleukin-1beta and transforming growth factor-beta1 compared with injured vehicle-injected controls and led to a transient improvement of contractile tension 3 days after the injury. No adverse effects were seen for as much as 3 weeks after the dexamethasone injection. The data indicate that one dose of dexamethasone administered soon after muscle strain may facilitate recovery of contractile tension without causing major adverse consequences in this experimental model.

This laboratory previously demonstrated that hyperbaric oxygen and hyperbaric carbogen improved oxygenation in the R3230Ac tumor, but normobaric 100% O2 and carbogen did not. The current study assessed tumor growth after exposure to radiation plus either hyperbaric oxygen, carbogen or carbogen/nicotinamide and the relationship between pretreatment tumor oxygenation and growth time. R3230Ac carcinomas were grown in the flanks of F344 rats. Animals were randomized to one of seven radiation treatment groups: sham irradiation or irradiation plus room air, hyperbaric oxygen (100% O2/3 atmospheres), nicotinamide (0.3 mg/g intraperitoneally 20 min before irradiation), carbogen, carbogen/nicotinamide or hyperbaric oxygen/nicotinamide. Tumors received 20 Gy in a single dose. Median growth times were 6, 18, 18, 20, 22, 28 and 27 days for controls and irradiation plus room air, carbogen, nicotinamide, carbogen/nicotinamide, hyperbaric oxygen and hyperbaric oxygen/nicotinamide, respectively. Irradiation with hyperbaric oxygen, hyperbaric oxygen/ nicotinamide and carbogen/nicotinamide increased growth time (P < 0.001, P < 0.001 and P = 0.003, respectively) relative to room air. Hyperbaric oxygen was significantly more effective than carbogen/nicotinamide (P = 0.001). Growth times for all tumors exposed to hyperbaric oxygen were longer than those of the most fully oxygenated tumors (no baseline pO2 values < 10 mm Hg) not exposed to hyperbaric oxygen (P < 0.001). These results suggest that hyperbaric oxygen may improve radiation response by additional mechanisms separate from overcoming the oxygen effect.

Our results suggest that the ankle joint does not have to be positioned in plantarflexion after operative repair using the described technique.

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