The immediate effects of ingesting melatonin in the daytime include decreased alertness and body temperature. To date, no researcher has examined whether daytime ingestion of melatonin leads to impairments in variables relevant to short-term (<10 min) athletic performance. Twelve physically active participants (mean +/- s age = 25.2 +/- 5.0 years, body mass = 81.4 +/- 12.1 kg and chronotype = 33.8 +/- 6.3 units) ingested 5 mg of melatonin or placebo at 11:45 hours in a double-blind experiment. At 13:00 and 17:00 hours, subjective alertness was measured, together with intra-aural temperature, reaction time (two-, four- and eight-choice), short-term memory recall and grip strength. Performance, ratings of perceived exertion (RPE) and heart rate were also recorded during a 4-km cycling time trial. At 13:00 hours, the mean +/- s intra-aural temperature was 0.49 +/- 0.79 degrees C lower after ingestion of melatonin than after placebo (p = 0.015), but this difference was not apparent at 17:00 hours. At both 13:00 and 17:00 hours, melatonin reduced (p < 0.05) alertness, short-term memory and exercise heart rate by 1.5 +/- 1.8 units, 1 +/- 1 digits and 6 +/- 9 beats.min(-1), respectively (mean +/- s). Eight-choice reaction time was also slower at both times of day after ingesting melatonin. Melatonin did not influence time trial performance or RPE (p > 0.05). The effects of 5 mg of melatonin seem more pronounced for mental rather than physical components of short-term athletic performance, although the cardiovascular responses to exercise are affected. Some effects of melatonin were apparent 5 h after ingestion when the hypothermic effects of melatonin had dissipated.

Adult↗

PubMedDate not supplied

Effects of prostaglandin E1 in twelve-hour lung preservation.

The effects of hypothermic lung preservation were evaluated in 12 mongrel dogs receiving double lung allografts. Animals underwent transplant procedures after 12 hours of static preservation at 4 degrees C following pulmonary artery flush with 60 to 80 ml/kg cold modified Collins solution. Donors were pretreated with allopurinol and recipients with methylprednisolone and perireperfusion deferoxamine. Six donor animals received a PGE1 infusion (20 to 500 ng/kg/min) for 20 minutes before harvest at doses causing a significant reduction in pulmonary vascular resistance. After implantation, recipients were maintained at ventilator settings identical to those used in donors. A fixed FIO2 (0.4) was maintained, except for 15-minute periods of FIO2 1.0 that were used to measure left-to-right intrapulmonary shunt fraction (Qs/Qt) and alveolar-arterial oxygen gradients (PAO2-PaO2). Cardiopulmonary function was studied for 20 hours. Pretreatment with PGE1 resulted in reduced survival (p less than 0.05) and increased PAO2-PaO2 (p less than 0.05) and Qs/Qt (p less than 0.05) 30 minutes after reperfusion. After 60 minutes of reperfusion, mean arterial pO2 (FIO2 0.4) was 148 mm Hg in controls and 80.5 mm Hg in the PGE1 group (p less than 0.02). There was no significant difference in pulmonary vascular resistance, cardiac output, mixed venous oxygen saturation, airway resistance, compliance and physiologic dead space between groups at any time after implantation. After 20 hours of reperfusion, pO2 (FIO2 0.4) in the control group was well maintained at 140 (+/- 52) mm Hg. The method of lung preservation in control animals resulted in good survival and adequate gas exchange after 12 hours of ischemia and 20 hours of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗

PubMedDate not supplied

Acute physiologic changes after extended pulmonary preservation.

The physiologic effects of 12-hour lung preservation were assessed in six mongrel dogs studied for 20 hours after double-lung allograft implantation. Donor animals were pretreated with allopurinol (30 mg/kg) and methylprednisolone (500 mg) intravenously at anesthesia induction. Heart-lung blocks were harvested after cardioplegic arrest, and a simple pulmonary artery flush of 4 degrees C modified Collins' solution was administered at 15 ml/kg/min. The lungs were ventilated with 100% nitrogen during flushing and inflation. Recipient animals received an infusion of deferoxamine (20 mg/kg) during implantation and were pretreated with methylprednisolone (500 mg) intravenously. All six implantations were technically successful. Two animals died of cardiac standstill 12 and 24 hours postoperatively. Gas exchange deteriorated after implantation compared with donor levels but remained in a range compatible with survival, and at 20 hours arterial oxygen tension (FiO2 0.4) was 138 +/- 91 mm Hg. Similar changes were seen in alveolar-arterial oxygen gradients and arterial-alveolar oxygen tension fraction. Elimination of carbon dioxide was satisfactory. Pulmonary venous shunt fraction rose significantly at the end of the study. Hemodynamic changes consisted of a gradual increase in pulmonary vascular resistance and a reduction in cardiac output. Lung mechanics also deteriorated, with a gradual rise in airway resistance and a fall in compliance. The double-lung model allows detailed assessment of the early effects of preservation and may have certain advantages over heart-lung models of preservation. The preservation technique warrants further study.

Allopurinol↗