Extent Of Retention Research Articles

Characteristics of sex behaviour in male rats following castration

Summary The decline of sex behaviour following castration, and the qualitative changes in behaviour resulting therefrom, were studied in adult male Long-Evans rats. Percentages of animals showing the ejaculatory pattern decreased rapidly but the rate of decline was quite variable. In two different experimental series the percentages of rats showing the complete pattern of mating behaviour in the fourth postoperative week were 42·0 and 8 per cent (n=46 and 63, respectively). Some animals were tested for 7 months and in one animal an ejaculatory pattern was noted 147 days after castration. Ejaculation latency (period from first intromission to ejaculation) and the number of intromissions to ejaculation were both decreased in the first 2 or 3 weeks postoperatively. Ejaculation latency increased thereafter over preoperative levels, but intromission frequency remained below them until the ninth week. The latency to first intromission, the frequency of mounting and the post-ejaculatory refractory period were generally increaed on all postoprative tests. It is concluded that (1) male rats may retain all components of sex behavour for relatively long periods after castration although the extent of retention is vairable, and (2) in the early postoperative period the ejaculatory mechanism is facilitated, although sexual ‘arousal’ is inhibited.

The contamination of grassland with radioactive strontium—I initial retention and loss

Field experiments using Sr 89 applied as a spray have been carried out under widely varying conditions in the U.K. to investigate the initial retention of airborne radioactive strontium on the edible herbage of permanent pastures and its subsequent loss. On average about one quarter of the deposit was initially retained on herbage edible by cattle and a similar fraction was held in the basal tissues. After contamination the levels of radioactivity in edible herbage decreased not only because of the physical decay of Sr 89 but also because of its removal by rain and other processes. This “field loss” was approximately exponential over periods of up to 9 weeks; it caused the activity in edible herbage per unit area of pasture to decrease by a factor of about 2 each 14 days. On account of the growth of new tissues the activity per unit weight of herbage decreased more rapidly; the half period for field loss on this basis was about 9 days. Factors which cause variation in the extent of retention and loss are discussed and the present results are compared with other findings. The effect of defoliating recently contaminated pastures was also examined; the content of Sr 89 on herbage which regenerated later in the season were affected to only a very small extent.

A Comparison of the Extent of Retention Accompanying the Use of Three Teaching-Testing Procedures

A Comparison of the Extent of Retention Accompanying the Use of Three Teaching-Testing Procedures