Colonization and maintenance of murine embryonic stem cells on poly(alpha-hydroxy esters).

The aim of this study was to determine the ability of various poly(alpha-hydroxy esters) to support the in vitro propagation of murine embryonic stem (ES) cells in an undifferentiated state. To this end, ES cell colonization, growth and Oct-4 immunoreactivity following a 48 h culture period upon poly((D,L)-lactide), poly((L)-lactide), poly(glycolide) and poly((D,L)-lactide-co-glycolide) (PLGA) were assessed. By the analysis of live and dead cell number indices and Oct-4 immunoreactivity, ES cell colonization rate during a 48 h culture period was found to be significantly greater on PLGA compared to all the other unmodified poly(alpha-hydroxy esters) tested. Surface treatment of all polymers with 0.1m potassium hydroxide revealed a significant increase in ES cell live numbers when compared to all unmodified polymers, thus revealing a correlation between polymer content, hydrophilicity and colonization rate. These data suggest that surface treated poly(alpha-hydroxy esters) may be employed for ES cell scale up procedures and in tissue engineering applications requiring the colonization of scaffolds by ES cells in an undifferentiated state. According to such applications, once the designated scaffold has been colonized, ES cell directed differentiation into the desired and fully differentiated, functional adult tissue may then be effected.

Physiological responses in high-P subjects during active and passive coping.

There have been relatively few studies of the psychophysiological correlates of Eysenck's dimension of psychoticism (P) and those which do not exist report findings which cannot be readily integrated to isolate a distinctive physiological basis of P. The present study investigated differences between subjects scoring high and low on the P scale of the Eysenck Personality Questionnaire (EPQ) in relation to sympathetic and parasympathetic arousal following aversive stimulation. An active-passive coping paradigm using an aversive tone was selected to elicit responses and cardiovascular measures (heart period, heart period variance, T-wave amplitude) and a skin conductance measure (event-related skin conductance) were obtained. The findings show that differences between high- and low-P subjects are specific to the coping condition. Under active coping, high-P subjects exhibited greater sympathetic arousal following the aversive tone than low-P subjects. There was no significant difference between the high-P and low-P subjects on any physiological variable under the passive coping condition. It is suggested that if there is differential functioning of the divisions of the autonomic nervous system in subjects differing in P, that these differences may only manifest themselves under specific situations.

Effect of long flights on the cognitive performance of air crew.

The cognitive performance of groups of subjects was tested after flights lasting between 7.5-9.5 hours to the north, east and west of Sydney (ns = 10, 12, and 12) and compared with the performance of a ground-based control group (n = 12). Analysis showed an impairment in performance of the flight groups following the flights. The analysis suggests that part of the performance change following transzonal flights may result from stress induced during the flight rather than adjustment to new time zones.

EEG correlates of exercise dependency.

Jacobs' (1986) proposition that dependency is the result of two sets of predisposing factors (one of which is either an excessively depressed or excited resting physiological state) was examined in relation to exercise dependency by investigating EEG characteristics of subjects committed to fitness regimes. EEG records of three groups of subjects who differed in terms of degree of dependency were studied under resting conditions both pre- and post-exercise. The results indicated that although there were no differences between groups in terms of relative power in each of five EEG bandwidths covering the range 0 to 30 Hz, the power distribution within the alpha (7.5-13 Hz) bandwidth was significantly different for high dependent and non-dependent groups under both the pre- and post-exercise conditions. While the distribution was skewed toward the lower alpha frequencies for the low dependent group, it was skewed toward the higher frequencies for the high dependent group with the distribution for a group with high involvement but low dependency falling between these extremes. This finding is taken as partial support for Jacobs' notion that dependency is associated with greater physiological excitation in the resting state.

Gender rivalry and attitudes toward sex roles: changes over a fifteen-year period.

Two samples (ns = 80) of men and women tested 15 years apart were observed to respond differently under rivalry conditions. Comparison of scores on a scale designed to measure attitudes to sex roles indicated a significant change during the 15-year period which may account for the change in behaviour observed during rivalry.

Mental performance of air crew following layovers on transzonal flights.

Studies of transzonal travel indicate that desynchronization of performance and physiological rhythms occurs following long-haul flights. In an attempt to overcome the problems associated with such desynchronization, air crew are given layover periods en route. The extent to which such layovers are effective in removing performance deficit, however, has not been studied. The present study was designed to remedy this situation by investigating performance levels following layover periods on both eastward and westward long-haul flights. The results suggest that layovers may largely eliminate performance deficits but only if flight times are such that air crew may maintain a reasonably normal sleep-rest cycle.

Achievement motivation, performance and cardiovascular activity.

Cardiovascular measures were obtained from 40 subjects differing in level of achievement motivation during the performance of a vigilance task. Analysis of interbeat interval and heart rate variability indicated that cardiovascular measures obtained from low achievers did not differ significantly from pre-test measures during the performance of the task, while the measures from high achievers did. In addition, the performance of high achievers was significantly better than the performance of low achievers. It is suggested that these findings indicate that high achievers are marked by the effort they expend in performance and that such effort is reflected in the cardiovascular activity of such subjects.

The effect of passive smoking on vigilance performance.

The present experiment was designed to test for effects of passive smoking on vigilance performance as well as to determine whether smokers and non-smokers are differentially affected by exposure to passive smoking. Four groups of subjects were used--smokers and non-smokers working in either clean or smoky air--and measures of decision time, movement time, correct detections, d' and beta, were obtained together with ratings of mood. The results show that sensitivity and accuracy of both smokers and non-smokers was detrimentally affected by passive smoking, and that the onset of the effect was earlier for the non-smoking subjects than for the smoking subjects. In addition, passive smoking significantly reduced decision time for the non-smoking subjects although movement time and beta were not significantly affected by exposure to the smoky environment. The findings indicate that both smokers and non-smokers may be adversely affected by passive smoking although effects may not appear until some time has elapsed. Data obtained from the mood scale show that feelings of anger and annoyance are increased by exposure to smoke and it is suggested that these feelings may contribute to the observed performance deficits.

The effect of intermittent noise on cardiovascular functioning during vigilance task performance.

This study was designed to investigate the effect of presentations of intermittent noise differing in predictability on cardiovascular functioning during task performance. Under a quiet condition and three conditions of intermittent noise, measures of blood pressure, heart rate (interbeat interval), and heart rate variability (variance, successive difference mean square, and the 0.1 Hz component of sinus arrhythmia) were obtained while subjects were occupied with a 55-min vigilance task. The results indicated that intermittent noise significantly increased diastolic and mean blood pressure. In addition, 0.1 Hz measures differed between the group working under quiet conditions and the groups working under noise. Although heart rate increased in all groups during the task, it increased significantly more in groups receiving unpredictable noise bursts. For the variables that were significantly affected by the noise presentations there was no evidence of response habituation over the task period. The results are discussed in relation to the effort required to maintain performance levels during noise, and attention is drawn to the implications of the present findings for cardiovascular health under conditions of chronic intermittent noise.

Reaction time and movement time after active and passive smoking.

Reaction time and movement time were studied following active and passive smoking in two groups of 20 women. All subjects were tested under a clean air and smoky air condition and the results showed that, while there was no difference between groups for either measure in the clear air condition, the active smokers had faster reaction time and movement time in the smoky air condition. Smoky air had no significant effect on the responses of the passive smoking group.

The effect of intermittent noise on vigilance performance.

An experiment was conducted to determine the effect of the level of predictability of intermittent noise on performance on a visual vigilance task. Under a quiet condition and three intermittent noise conditions, subjects (Ss) carried out a 55-min task where they were required to detect a change in the brightness of one element of a visual display. The results indicated that Ss were less sensitive, less accurate, and more prone to response failures during intermittent noise, although responses were faster under noise conditions. Measures of response bias and response certainty were not significantly affected by the presentation of noise. Variation in the level of predictability of the noise affected only the accuracy of response measure during the final quarter of the vigilance task, with the group receiving the least predictable noise performing significantly worse than the other three groups. The results are discussed in relation to theories of noise and performance.

Component analysis of orientation illusions.

Orientation illusions occur when the inducing figure is a line or grating (the tilt illusion) or a square outline frame (the rod-and-frame illusion). In the range of inducing figure tilts between vertical and horizontal, the tilt illusion describes one cycle of positive (direct) and negative (indirect) effects but the rod-and-frame illusion describes two such cycles. In two experiments, angular functions of illusions were measured with the six possible inducing figures which result when two of the four sides of a square inducing frame are deleted. As expected, the parallel-side frame amputations induced angular functions similar to the tilt illusion and these functions differed from those induced by the orthogonal-sided amputations. In agreement with previous findings on the nonadditivity of tilt illusions, the sum of angular functions induced by frame amputations, which together form a complete frame, were not always equivalent to the angular function induced by a complete frame, and there were asymmetries in the data fro which neither of two simple hypotheses could adequately account. The discussion focuses upon properties of inducing figures which psychophysical hypotheses might need to consider in order to account for the shapes of angular functions of orientation illusions and, in particular,a distinction is drawn between the global orientation of the inducing figure and the orientations of it (local) component features. It is suggested that it might be fruitful if the tilt illusion and the rod-and-frame illusion were conceived of as illusions resulting from inducing figures composed of all or part of n gratings of spatial frequency fn intersecting at angles of 180 degrees/n.