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Apparent metabolizable energy (AME) of meat and bone meal (MBM) for poultry is highly vari-able, but impractical to measure routinely. Previous efforts at developing an in vitro method for predict-ing AME have had limited success. The present study uses data from a previous publication on the AME of 12 MBM samples, determined using 288 White Pekin ducks, as well as composition data on these samples. Here, we investigate the hypothesis that 2 noncompo-sitional attributes of MBM, particle size and protease resistance, will have utility in improving predictions of AME based on in vitro measurements. Using the same MBM samples as the previous study, 2 measurements of particle size were recorded and protease resistance was determined using a modified pepsin digestibility assay. Analysis of the results using a stepwise construc-tion of multiple linear regression models revealed that the measurements of particle size were useful in build-ing models for AME, but the measure of protease resis-tance was not. Relatively simple (4-term) and complex (7-term) models for both AME and nitrogen-corrected AME were constructed, with R-squared values rang-ing from 0.959 to 0.996. The rather minor analytical effort required to conduct the measurements involved is discussed. Although the generality of the results are limited by the number of samples involved and the spe-cies used, they suggest that AME for poultry can be accurately predicted through simple and inexpensive in vitro methods. [ABSTRACT FROM AUTHOR]

Implicit directional cues in arrowhead cursors could influence positioning of a cursor on the screen of the computer. Performance during cursor placement may benefit from compatibilities between cursor orientation and direction of movement. Arrowheads could also elicit illusory processes that may affect judgments of (a) the distances on the screen or (b) the location of the point of the arrowhead. To address the impact of the cursor's orientation on its positioning, we had 12 participants move cursors (crosshairs, leftward, or rightward arrow) leftward or rightward to targets (near, far) on a computer screen. Movement amplitude was more important than cursor orientation for initiation of rightward movements, whereas cursor orientation affected the duration of leftward movements and movements to farther targets. Arrowhead orientation contributed to the greater overshooting of far targets. There was little evidence that compatibility of orientation and direction of movement assisted response initiation or execution, and there was little indication that arrowhead cursors led to illusory effects that influenced cursor placement. Arrowhead cursors can provide irrelevant stimulus dimensions that distract users. This work can be applied to the design of cursors in graphical user interfaces. The use of orientation-neutral cursors or cursors whose stimulus dimensions are more relevant is recommended. [ABSTRACT FROM AUTHOR]

Thymic development and somatic growth were investigated in three strains of rat. The well established influence of sex and age on somatic growth was confirmed. It was also found that the rate of thymic growth was not influenced by the sex of the animal until four weeks of age, but thereafter, the thymus grew faster in males compared with females of the same strain. Gonadectomy had a marked effect on the thymus, resulting in a higher rate of growth than in normal animals; but a slower initial rate of involution. The maximum thymus weights attained in gonadectomized animals were found to be independent of the age at which the animals were gonadectomized or of the sex of the animal Gonadectomy did not influence the point at which involution began. Thymic mitotic indices of gonadectomized animals were found to be higher than those of normal animals. The influence of sex hormones on somatic growth and the development of the thymus is discussed, and it is concluded that cell loss is the regulator of thymus growth and involution. [ABSTRACT FROM PUBLISHER]

Organ weights and blood parameters were measured in male and female Brattleboro rats with hereditary diabetes insipidus (DI) and in normal rats of the same strain, between 37 and 138 weeks old. Although differences in body weight between the homozygous DI and heterozygous normal rats accounted for differences in the weights of the heart and gonads, the weights of the spleen, liver and kidney were not solely body-weight dependent; there were significant sex and genotype differences in the mean weights of these organs. The liver, heart and gonads were the only organs showing age-dependent changes. No genotype-dependent differences were observed in the haematocrit and haemoglobin concentration, although there was a sex difference; the mean values of these parameters were higher in males. Plasma glucose concentrations were significantly lower in homozygous than in heterozygous rats; in the latter, plasma glucose concentration decreased with age. No significant changes occurred in the mean plasma concentrations of sodium or potassium with age or genotype. Total plasma lipids of heterozygous female rats showed both age- and genotype-dependent changes; this parameter reached a plateau at 90-100 weeks old, and was significantly higher in heterozygous females than in all other groups. Plasma proteins showed no age-dependent changes, but were of higher mean value in heterozygous than in homozygous rats and were greater in females than in males. Differences in blood parameters of homozygous and heterozygous Brattleboro rats are discussed in terms of differences in hormone concentrations. [ABSTRACT FROM AUTHOR]

Levels of corticosterone were measured in the plasma of male and female Brattleboro rats with hereditary diabetes insipidus (DI) and normal rats of the same strain, both at rest and after 15 min ether stress, on animals between 37 and 138 weeks old. Levels of plasma corticosterone were significantly lower in DI rats at rest compared with the level in heterozygous control rats. In stressed rats there were no significant differences in mean levels of plasma corticosterone between rat genotypes, within sexes. However, in both genotypes the corticosterone levels were significantly higher in females, irrespective of treatment. Although the resting plasma corticosterone levels were drastically depressed in homozygous DI rats, there was no impairment of the response to stress; the adrenal glands of homozygous rats were significantly more responsive to stress than the corresponding heterozygous rats. Adrenal responsiveness was not a satisfactory parameter of ageing in this strain of rat. [ABSTRACT FROM PUBLISHER]