Hepatic ornithine decarboxylase activity in the rat as influenced by retinyl acetate and ethanol or tryptophan

Sleep deprivation by the "flower pot" technique and spatial reference memory

This study investigated whether paradoxical, or rapid eye movement (REM), sleep deprivation (SD) affected spatial memory. SD was induced in male Wistar rats by housing them on small platforms over water. They fell into the water if they lost muscle tone. Controls were either housed in tanks with large platforms (TC) or in normal cages (CC). All rats had free access to food and water. Each day they were tested in a place-learning set task using a Morris water maze. The rats were released from 6 different starting points (sets) and allowed 2 min to find a submerged platform. Two trials were conducted from each starting point. SD caused a significant decrement in performance in Trial 1 from Day 2. By Day 4, when distance swum to find the platform was plotted against set, area under the curve was doubled in SD compared to that in TC and CC rats, indicating a significant impairment in reference spatial memory. There was no consistent effect on working memory, indicated by Trial 2. SD caused weight loss and increased serum corticosterone compared to that in CC rats. There were no differences in concentrations of hypothalamic, hippocampal, or cortical catecholamines or their metabolites. Serotonin metabolism was elevated in the hypothalamus and hippocampus in SD rats. These results indicate that SD induced in rats housed on small platforms causes a substantial impairment of reference memory. The memory deficit may not be specific to SD because the rats are physically stressed and lose some nonREM sleep when housed in these conditions.

The effect of chronic ethanol feeding on ornithine decarboxylase activity and liver regeneration

The effects of ethanol on liver regeneration are poorly understood. Acute and chronic exposure to ethanol have been found to exert opposite effects on the induction of ornithine decarboxylase, the rate-limiting enzyme for polyamine biosynthesis. Polyamines are necessary for DNA synthesis and liver regeneration after chemical or surgical liver injury. Short-term exposure to ethanol, which inhibits ornithine decarboxylase has been shown to inhibit DNA synthesis and liver regeneration, whereas more chronic exposure to ethanol increases ornithine decarboxylase activity and therefore could conceivably stimulate DNA synthesis and regeneration. To explore this later possibility, the effects of chronic ethanol consumption on ornithine decarboxylase activity, DNA synthesis and liver regeneration were studied in rats after sham laparotomy and partial hepatectomy. Chronic ethanol feeding failed to inhibit the induction of ornithine decarboxylase that occurred after partial hepatectomy and yet significantly inhibited posthepatectomy DNA synthesis and restitution of liver mass. These data suggest that the induction of hepatic polyamine biosynthesis is dissociated from DNA synthesis and liver regeneration after chronic consumption of ethanol.