The psychological and physiological measurements indicate that the experimental stress
had been administered correctly, as both patients and controls showed a significant
increase in subjective perception o f stress as shown by Spielberger score as well as the heart rate during the stress session. The lower pre-session Spielberger scores during the resting session as compared to the stress session is probably due to the subjects being
more familiar with the environment during the resting session which was carried out a week after the stress session.
Control subjects were members of the research laboratories who were more familiar with the environment, hence they were able to relax more easily and this may explain the significantly lower postrelaxation value in this group.
The increase in heart rate was variable. Patients generally showed a higher rise in pulse rate than controls, but the difference did not reach the level o f stotistical significance. There was a wide range of difference in the amount o f increase in pulse rate between
subjects (5-37BPM in patients, 3-13 in controls). Tullen et a l.(1989) reported a uniform pattern o f increase in heart rate(6-7BPM) in their subjects. This is probably due to the
fact that their subjects were from a homogenous group o f trained sportsmen, whereas our subjects were from a heterogenous group.
Paradoxically, there was a negative correlation between the increase in Spielberger score and rise in the heart rate during the stress session (r= 0 .48 ) which was close to the level
of statistical significance (p < 0 .0 7 ). In other words cognitive perception o f stress is inversely related to physiological changes. This finding is in agreement with those of
Salmon and Kaufman(1990) who showed a statistically significant negative correlation between the endocrine response and preoperative anxiety in a group o f patients
undergoing major surgery.
Our subjects were given 600mg of aspirin orally at the beginning of each session and a blood sample was collected after 2 hours. As it was found that aspirin does not affect
TBA reactivity o f plasma(see IV.4.3.2.7.), it was considered safe to use the plasma samples for both lipid peroxidation and 2 ,3 ,DHB assays.
We found that the measurement of 2,3,DHB was flawed by a number o f methodological problems, the main one being the presence of pyrogallol (1,2,3 ,trihydrobenzene) as a stabilizer in diethyl ether which was recommended for extraction o f plasma samples in the original method(Grootveld & Halliwell,1986). Since then, we have been using ethyl
acetate for the extraction procedure and the method is s ta n d a rd i^ . However, as all plasma aliquots were used before the methodological problems were discovered, it has not been possible to obtain an accurate value of 2 ,3 ,DHB content of any of the samples.
A second Stroop test was not considered appropriate as it has been shown that there is a reduction in the response magnitude if the test is repeated (Tulen et al., 1989).
In this study, there was no demonstrable difference in the levels of TBA-RS or MDA-
TBA adduct between patients and controls. This is in contrast to the results of our pilot study. Furthermore, the experimental stress as induced by CWT did not alter the TBA
reactivity o f plasma in either group, although control subjects had a reduced level of MDA-TBA adduct during the stress session. The measurement o f lipid peroxidation is
faced with a number o f problems(see IV. 1.8.). Although the thiobarbituric acid test is
probably the most widely used single assay for measuring lipid peroxidation, it has been criticised for its lack of specificity when applied to human body fluids(Gutteridge &
Halliwell, 1990). HPLC separation of MDA-TBA adduct before measurement solves only part of the problem because some compounds (especially amino acids and sugars) react
in the assay to form an authentic MDA-TBA adduct.
We acknowledge that the numbers are small, and the possibility o f a type II error exists.
However, as we were not satisfied with the available methodology for measurement of free radical activity, the study was not pursued on a larger number o f subjects. With increased understanding in free radical chemistry and introduction o f more specific assays, some of the problems presented above will be avoided. Further research to clarify the relationship between stress, pain and changes in the body chemistry in a larger
number of subjects is warranted.
Halliwell (1991) points out that almost any disease is likely to be accompanied by
increased formation o f reactive oxygen species, and expanding free radical theories to an ever increasing list o f diseases is not the only way forward. In rheumatoid arthritis, autoimmune disease, iron overload and reoxygenation injury there is reasonable evidence
that some tissue damage is radical mediated, but for many of the other conditions, it has merely been shown that radicals are produced, without an assessment o f their role in the
for measuring oxidant generation in humans, is needed to evaluate the exact contribution
o f oxidant generation to disease pathology. Measurement o f antioxidants in local tissues