Yeast ribonucleic acid (RNA) was first mentioned as having beneficial effects on memory by Cameron and co-workers (1961, 1963) who reported that RNA administered in tablet form or by intravenous injection produced clinical improvement in patients suffering from senile memory impairmenL This effect was later studied by Cook et al (1963) who showed that yeast RNA (160 mg/kg I.P.) increased the rate at which rats learn the response of climbing a pole to escape shock. Recently, however, the suggestion that RNA produces a general improvement in learning or memory processes has been questioned by Wagner et al (1966). These workers repeated the experiment reported by Cooketal and obtained essentially the same results. They then went on to test the effects of yeast RNA injections on learning of a food motivated brightness discrimination, on shock sensitivity and on general activity and found that RNA did not change performance in these situations. Similarly, Luttges et al (1966) have shown that rats injected with rat brain RNA were not superior to a saline injected control group in various learning situations, including a water "Y" maze and a Lashley III maze.Luttges et al also found that IP injections of p32 labeled RNA did not result in significant amounts of radioactivity being found in the brain. This result has also been obtained by Sved (1965), and by Eist & Seal (1965) using a tracer technique, and by Enesco (1966), using radioautography, and suggests that any effects of exogenous RNA are not due to a direct incorporation of RNA into brain tissue.The present study was undertaken in an attempt to determine the basis of the effect of RNA injections on shock motivated pole-climbing behavior and to examine the effects of these injections on behavior in other situations. The Ss were required to learn a spatial discrimination and reversal in an electrified two-choice discrimination box which was divided into five sections: start area, choice area, two threshold areas and a goal area. All but the goal area had grid floors which could be electrified by the experimenter. A detailed description of the apparatus and technique has been given elsewhere (Corson, 1965). On the first training day the Ss learned to go quickly from the start to the goal (the start grid was electrified at 5 sec. and all grids were electrified at 30 sec.), through either door, to avoid shock. Having reached a criterion of three consecutive unshocked runs, they then learned to enter the goal by crossing the threshold area on one side. During this phase the incorrect door was locked and its threshold area was electrified. On the following day, the 0ppcsite door was correct.The results show that neither of the experimental groups was different from the controls in any of the measures taken (start latency, total latency, number of trials to criterion in each phase, and number of errors in each phase). The Mann-Whitney U test (two-tailed) was used in all cases.It is important to note that the first phase of this experiment, when the animals had not yet ...
We used the monogonont rotifer, Brachionus calyciflorus, to study the effect of ambient temperatures of 16 C, 22 C, and 29 C on longevity and life history parameters. We found that temperature had a significant relationship with longevity. At lower temperature, there was prolongation of the pre-reproductive and reproductive periods, but fecundity was reduced significantly due to suppression of the reproductive rate. When lifespan of short-and long-lived rotifers was compared, we found that the significant longevity difference in these rotifers was due to extension of reproductive and post-reproductive periods. The fecundity was significantly higher in longer lived rotifers due to the extension of the reproductive period, but the reproductive rate was significantly lower in these rotifers. A consistent negative relationship between rotifer longevity and the rate of reproduction was observed at all temperatures, and it was particularly pronounced in rotifers reproducing heavily at the end of the reproductive stage of their life cycle. The combined rate of living/oxidative damage theory may help explain the temperature effects that we observed.
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