Measurement of myocardial free radical production during exercise using EPR spectroscopy.

Exercise is associated with an increase in oxygen flux through the mitochondrial electron transport chain that has recently been demonstrated to increase the production of reactive oxygen species (ROS) in skeletal muscle. This study examined whether exercise also causes free radical production in the heart. We measured ROS production in seven chronically instrumented dogs during rest and treadmill exercise (6.4 km/h at 10 degrees grade; and heart rate, 204 +/- 3 beats/min) using electron paramagnetic resonance spectroscopy in conjunction with the spin trap alpha-phenyl-tert-butylnitrone (PBN) (0.14 mol/l) in blood collected from the aorta and coronary sinus (CS). To improve signal detection, the free radical adducts were deoxygenated over a nitrogen stream for 15 min and extracted with toluene. The hyperfine splitting constants of the radicals were alpha(N) = 13.7 G and alpha(H) = 1.0 G, consistent with an alkoxyl or carbon-centered radical. Resting aortic and CS PBN adduct concentrations were 6.7 and 6.3 x 10(8) arbitrary units (P = not significant). Both aortic and CS adduct concentrations increased during exercise, but there was no significant difference between the aortic and CS concentrations. Thus, in contrast to skeletal muscle, submaximal treadmill exercise did not result in detectable free radical production by the heart.

Homing endonucleases encoded by germ line-limited genes in Tetrahymena thermophila have APETELA2 DNA binding domains.

Three insertion elements were previously found in a family of germ line-limited mobile elements, the Tlr elements, in the ciliate Tetrahymena. Each of the insertions contains an open reading frame (ORF). Sequence analysis of the deduced proteins encoded by the elements suggests that they are homing endonucleases. The genes are designated TIE1-1, TIE2-1, and TIE3-1 for Tetrahymena insertion-homing endonuclease. The endonuclease motif occupies the amino terminal half of each TIE protein. The C-terminal regions of the proteins are similar to the APETELA2 DNA binding domain of plant transcription factors. The TIE1 and TIE3 elements belong to families of repeated sequences in the germ line micronuclear genome. Comparison of the genes and the deduced proteins they encode suggests that there are at least two distinct families of homing endonuclease genes, each of which appears to be preferentially associated with a specific region of the Tlr elements. The TIE1 and TIE3 elements and their cognates undergo programmed elimination from the developing somatic macronucleus of Tetrahymena. The possible role of homing endonuclease-like genes in the DNA breakage step in developmentally programmed DNA elimination in Tetrahymena is discussed.

Effects of epinephrine and vasopressin in a piglet model of prolonged ventricular fibrillation and cardiopulmonary resuscitation.

OBJECTIVE: We recently demonstrated that vasopressin alone resulted in a poorer outcome in a pediatric porcine model of asphyxial cardiac arrest when compared with epinephrine alone or with epinephrine plus vasopressin in combination. Accordingly, this study was designed to differentiate whether the inferior effects of vasopressin in pediatrics were caused by the type of cardiac arrest. DESIGN: Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow. SETTING: University hospital laboratory. SUBJECTS: Eighteen piglets weighing 8-11 kg. INTERVENTIONS: After 8 mins of ventricular fibrillation and 8 mins of cardiopulmonary resuscitation, either 0.4 units/kg vasopressin (n = 6), 45 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered. Six minutes after drug administration, a second respective bolus dose of 0.8 units/kg vasopressin, 200 microg/kg epinephrine, or a combination of 200 microg/kg epinephrine with 0.8 units/kg vasopressin was given. Defibrillation was attempted 20 mins after initiating cardiopulmonary resuscitation. MEASUREMENTS AND MAIN RESULTS: Mean +/- sem left ventricular myocardial blood flow 2 mins after each respective drug administration was 65 +/- 4 and 70 +/- 13 mL x min(-1) x 100 g(-1) in the vasopressin group; 83 +/- 42 and 85 +/- 41 mL x min(-1) x 100 g(-1) in the epinephrine group; and 176 +/- 32 and 187 +/- 29 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p <.006 after both doses of epinephrine-vasopressin vs. vasopressin and after the first dose of epinephrine-vasopressin vs. epinephrine, respectively). At the same times, mean +/- sem total cerebral blood flow was 73 +/- 3 and 47 +/- 5 mL x min(-1) x 100 g(-1) after vasopressin; 18 +/- 2 and 12 +/- 2 mL x min(-1) x 100 g(-1) after epinephrine; and 79 +/- 21 and 41 +/- 8 mL x min(-1) x 100 g(-1) after epinephrine-vasopressin (p <.025 after both doses of vasopressin and epinephrine-vasopressin vs. epinephrine). Five of six vasopressin-treated, two of six epinephrine-treated, and six of six epinephrine-vasopressin treated animals had return of spontaneous circulation (nonsignificant). CONCLUSIONS: In this pediatric porcine model of ventricular fibrillation, the combination of epinephrine with vasopressin during cardiopulmonary resuscitation resulted in significantly higher levels of left ventricular myocardial blood flow than either vasopressin alone or epinephrine alone. Both vasopressin alone and the combination of epinephrine with vasopressin, but not epinephrine alone, improved total cerebral blood flow during cardiopulmonary resuscitation. In stark contrast to asphyxial cardiac arrest, vasopressin alone or in combination with epinephrine appears to be of benefit after ventricular fibrillation in the pediatric porcine model.

Effects of active compression-decompression cardiopulmonary resuscitation with the inspiratory threshold valve in a young porcine model of cardiac arrest.

Active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) with the inspiratory threshold valve (ITV) has been recently recommended by the American Heart Association for treatment of adults in cardiac arrest (class IIb: alternative, useful intervention), but this new technique has never been used in a pediatric population. Thus, this study was designed to evaluate ACD + ITV CPR in a young porcine model of cardiac arrest. After 10 min of ventricular fibrillation, and 8 min of standard CPR, ACD + ITV CPR was performed in seven 4- to 6-wk-old pigs (8-12 kg); defibrillation was attempted 8 min later. Within 2 min after initiation of ACD + ITV CPR, mean (+/- SEM) coronary perfusion pressure increased from 18 +/- 2 to 24 +/- 3 mm Hg (p = 0.018). During standard versus ACD + ITV CPR, mean left ventricular myocardial and total cerebral blood flow was 59 +/- 21 versus 126 +/- 32 mL.min(-1).100 g(-1), and 36 +/- 7 versus 60 +/- 15 mL.min(-1).100 g(-1), respectively (p = 0.028). Six of seven animals were successfully defibrillated, and survived >15 min. In conclusion, the combination of ACD + ITV CPR significantly increased both coronary perfusion pressure and vital organ blood flow after prolonged standard CPR in this young porcine model of ventricular fibrillation.