Survival in transgenic ALS mice does not vary with CNS glutathione peroxidase activity.

OBJECTIVE: Transgenic mice that overexpress a human gene encoding mutant cytosolic superoxide dismutase (SOD1) develop a progressive motor neuron loss that resembles human ALS. Why mutant SOD1 initiates motor neuron death is unknown. One hypothesis proposes that the mutant molecule has enhanced peroxidase activity, reducing hydrogen peroxide (H2O2) to form toxic hydroxyl adducts on critical targets. To test this hypothesis, the authors generated transgenic ALS mice with altered levels of glutathione peroxidase (GSHPx), the major soluble enzyme that detoxifies H2O2. METHODS: SOD1(G93A) ALS mice were bred with mice bearing a murine GSHPx transgene that have a four-fold elevation in brain GSHPx levels and with mice having targeted inactivation of the GSHPx gene and reduced brain GSHPx activity. RESULTS: Survival was not prolonged in ALS mice with elevated brain GSHPx activity (p = 0.09). ALS mice with decreased GSHPx brain activity (20% of normal) showed no acceleration of the disease course (p = 0.89). The age at disease onset in the ALS mice was unaffected by brain GSHPx activity. CONCLUSION: The level of GSHPx activity in the CNS of transgenic ALS mice does not play a critical role in the development of motor neuron disease.

In-vitro evaluation of the hemolytic effects of augmented venous drainage.

Augmentation of venous drainage with either kinetic-assisted drainage (KAVD) or vacuum-assisted (VAVD) has been used clinically in order to overcome added venous resistance due to smaller venous cannulae or tubing. This in-vitro study evaluates the extent of hemolysis and sub-lethal red blood cell membrane damage than occurs with augmented (kinetic or vacuum) when compared to conventional gravity drainage. Four trials were conducted using each test circuit. The circuits were primed with 6 liters of fresh heparinized bovine blood, which was diluted to a hematocrit of 32% and was recirculated at 5 L/min for 8 hours. Hemolysis was determined by the change in plasma free-hemoglobin (Hb), hematocrit, and potassium at two hour intervals. The red cell osmotic fragility index was used to quantify the sub-lethal red blood cell membrane damage and was also measured every two hours. After 8 hours, the mean +/- SD of the plasma free-Hb were: 96.27 +/- 69.45 mg/dl for gravity, 83.87 +/- 48.14 mg/dl for vacuum-assist, and 134.45 +/-83.78 mg/dl for kinetic-assist. Two-hour increases in the plasma free-Hb revealed the following median values (mg/dL/2 h): 16.90 for gravity, 13.75 for vacuum-assist, and 19.40 for kinetic-assist. Analysis of the two-hour increases in plasma free-Hb with Kruskal-Wallis One-Way ANOVA did not reveal a significant difference among the groups. After 8 hours, the red cell osmotic fragility test results at the 0.55% sodium chloride concentration were compared. The medians of the percent hemolysis were 52.67% for gravity, 49.8% for vacuum-assist, and 57.2% for kinetic-assist. Analysis with the Kruskal-Wallis Wallis One-Way ANOVA did not reveal a significant difference among the groups. Therefore, there is no significant increase in hemolysis or sub-lethal red blood cell membrane damage associated with the use of augmented venous drainage.