Reproductive Toxicity of Butylated Triphenyl Phosphate and Tricresyl Phosphate Fluids in F344 Rats

The effects of tricresyl phosphate (TCP) and butylated triphenylphosphate (BTP)-based hydraulic fluid on reproduction were studiedin F344 rats using a modification of the National ToxicologyProgram's Continuous Breeding Protocol. Groups of breeding pairsreceived single daily oral doses of an equal volume of either0, 0.6, 1.0 g BTP/kg or 0.4 g TCP/kg in sesame oil or 1.7 gneat BTP/kg for up to 135 days. A naive control group allowedto breed, but not dosed or handled daily, demonstrated thatdaily dosing and handling of the rats had no effect on reproduction.The fertility index and number of litters born were significantlydecreased in rats exposed to 1.0 and 1.7 g BTP/kg and 0.4 gTCP/kg. The number of pups per litter was significantly decreasedin the TCP group. A crossover mating experiment using 0.4 gTCP/kg/day and 1.0 g BTP/kg/day groups, each mated with vehiclecontrols, demonstrated that TCP caused 100% infertility in malerats but did not affect reproduction in females. BTP causeda significant decline in reproduction in female rats characterizedby low mating and fertility indices, decreased number of litters,and abnormal estrous cycles. Fertility was decreased in theBTP-dosed male rats. Both sexes of rats in the crossover experimentwith TCP and BTP had significant decreases in terminal bodyweights and increases in adrenal gland and liver weights. OnlyTCP-dosed male rats had significantly decreased testicular andepididymal weights. TCP-dosed female rats had increased ovarianweights, while BTP-dosed females had significantly lower uterineweights. The results of this study indicate that BTP and TCPare reproductive toxicants in F344 rats.     

Differential responses in intramuscular pressure and EMG fatigue indicators during low- vs. high-level isometric contractions to fatigue

This study investigated changes in intramuscular pressure (IMP) and surface electromyographic (EMG) parameters (mean frequency of the power spectrum, f_mean; and signal amplitude denoted as root mean square, RMS) during contractions to fatigue at 25 and 70% of maximal voluntary contraction (MVC). Parameters were recorded simultaneously from the vastus lateralis muscle during knee extension. A significant decrease in f_mean occurred with time at both contraction levels; however, the rate of decline (slope) was greater at 70% MVC. RMS increased throughout the contractions at both levels, with the relative increase being significantly greater for 25% MVC. IMP increased during 25% MVC but did not change during the 70% MVC contraction. IMP at rest was significantly higher post-contractions than it was pre-contractions at 25% MVC (21.1 vs. 8.0 mmHg, P < 0.01) and 70% MVC (13.7 vs. 8.6 mmHg, P < 0.01). Consequently, post-contraction IMP was higher at 25% MVC than at 70% MVC (P < 0.01). IMP changes throughout the fatiguing contractions correlated negatively with f_mean and positively with RMS at both MVC levels; however, these correlations were better at 25% MVC. The extent of intramuscular water accumulation is discussed as a major cause of the difference in IMP changes between 25% and 70% MVC. Significant differences in the rate of change for all parameters between high vs. low contraction levels may suggest a common mechanism governing changes in IMP and EMG fatigue indicators.     

Increased technetium uptake is not equivalent to muscle necrosis: scintigraphic,morphological and intramuscular pressure analyses of sore muscles after exercise

A scintigraphic technique employing technetium pyrophosphate uptake was used to identify the area of skeletal muscle damage in the lower leg of four runners 24 h after an ultramarathon footrace (160 km). Most of the race had been run downhill which incorporated an extensive amount of eccentric work. Soreness was diffuse throughout the posterior region of the lower leg. In order to interpret what increased technetium uptake reflects and to express extreme endurance related damages, a biopsy was taken from the 3-D position of abnormal uptake. In addition, intramuscular pressures were determined in the deep posterior compartment. Scintigraphs revealed increased technetium pyrophosphate uptake in the medial portion of the gastrocnemius muscle. For 3698 fibres analysed, 33 fibres (I%) were necrotic, while a few other fibres were either atrophic or irregular shaped. A cluster of necrotic fibres occurred at the fascicular periphery for one subject and fibre type grouping occurred for another. Ultrastructural analysis revealed Z-line streaming near many capillaries and variously altered subsarcolemmal mitochondria including some with paracrystalline inclusions. The majority of the capillaries included thickened and irregular shaped endothelial cells. Intramuscular pressures of the deep posterior compartment were slightly elevated (12–15 mmHg) for three of the four subjects. Increased technetium uptake following extreme endurance running does not just reflect muscle necrosis but also subtle fibre abnormalities. Collectively, these pathological findings are attributed to relative ischaemia occurring during the race and during pre-race training, whereas, intramuscular pressure elevations associated with muscle soreness are attributed to mechanical stress caused by extensive eccentric work during the race.