| Objective: More and more people are under stress in face of the increasing pressure from the modern life. On one hand, the adequate stress response is called"eustress"which can be some evolutionary advantage to human beings, on the other hand, excessive response can also lead to a variety of systemic disorders and even cause disease, when it has been changed into a harmful stress to human beings and is called"distress". Consequently, it's increasingly concerned to researchers to distinguish"eustress"from"distress"by the objective evaluation standards. And that's the very reason that we're going to find out the quantitative indicators of stress responses and try to define the standard of these indicators through the studies on the response process which is induced by stress.Methods: Mice were divided into 2 groups randomly, which were named control group and chronic stress group. The latter group was disposed of chronic multiple stress which was composed of restraint stress, tail-suspending stress, and water-immersing stress. Meanwhile, the indicators were determined for studying the influences of chronic multiple stress on the body as follows.1. The chronic multiple stress model was evaluated by the changes of the body weight after the stimulus of chronic stress.2. Body weight and survival time of which correlations were analyzed between control group and stress group, were recorded every day during the whole stress process; What's more, stress group was divided statistically into different subgroups according to the 2 indicators as stated, and the same analysis was given those subgroups.3. The biological parameters in serum of mice such as glucose (GLU), albumin (Alb), total protein (TP), creatinine (Cr) and alkaline phasphatase (ALP) of stress group were compared with control group, for the purpose of studying the influences of chronic multiple stress on them and a variety systemic disorders.4. Both MudoEb5 and MudoEb7 alleles at muridae H2-Eb locus were detected by SSP-PCR in order to analyze the relationship between their positive expressions and stress-induced changes of biological parameters and try to explore the genetic mechanism of chronic multiple stress.5. For the purpose of studying on the metabolic processes of calcium, magnesium and zinc under chronic stress, the concentrations of those ele- ments were determined by flame atomic absorption spectrometry.6. At the end of chronic multiple stress, hypoxia tolerance test was carried out, and then compared the body weight, spleen index, and the hypoxia tolerance time of stress group with those of the controls, and analyzed the relation between H2-Eb genetic polymorphism and the changes of those indicators.7. The effect of chronic multiple stress on immune system was studied by viewing the pathological changes in the thymus tissue slices with transmission electron microscope (TEM).8. After chronic multiple stress, the behavioral responses of mice were evaluated by measuring the learning and memory ability of mice with step- down test composed of 3 steps including memory acquisition, memory consolidation and memory extinction.Results:1. There were insignificant differences of the initial body weight between stress group and the controls, P>0.05. Because 1st death in stress group was happened on the 9th day, weights of 8th day of the 2 groups were compared and the results showed significant differences between them, weights of stress group were remarkable less than those of the controls, P<0.05.2. The result of initial body weight was 19.883±1.575 and 20.330±2.237 (g) respectively in stress group and the controls, and there was insignificant difference between them. The body weights measured from the 1st day to the 21st day (repeated measurement data) of stress group, were significantly less than those of control group, P<0.05. There was positive correlation between weight and survival time in the subgroups of stress group. Meanwhile, the survival median time would be 13.5 days when the body weights of stress group had been decreasing by more than 5.78%of that in control group, and the survival median time would be up to 22 days with the latter data was less than 5.78%.3. The results of biological parameters in serum: the significantly higher leve of Glu and Cr, and lower of Alb, TP and ALP in serum of stress group than those of the controls, P<0.05.4. The results of H2-Eb genetic polymorphism: Expressions of MudoEb5 and MudoEb7 were checked out in 65 and 80 of total 86 mice, and the positive rate were 75.58%and 93.02% respectively. There were significant differences on the level of TP, ALP and Alb of MudoEb7 positive mice and the level of TP, ALP in MudoEb5 positive mice between control group and stress group.5. The concentrations of magnesium and zinc in stress group were significantly lower than those in the controls, P<0.05, moreover, there were insignificant correlations between the 3 elements of stress group.6. Body weight, spleen index and hypoxia tolerance ability of stress group were significantly lower than those of control group, P<0.05. Furthermore, there were significant differences of the 3 targets above in MudoEb5 positive mice and body weight, spleen index in MudoEb7 positive mice between control group and stress group.7. The typical apoptosis cells were found in the thymus tissue slices of stress group with TEM, while nothing in the slices of the controls.8. In all the 3 steps of step-down test, error frequency of stress group were significantly more than that of the controls; the results also revealed that step down latency of stress group were significantly shorter than that of control group in memory consolidation test and memory extinction test.Conclusions:1. The chronic multiple stress animal model was established reasonably in this experiment and available to the next tests.2. The more significant the inhibition on the body weight growth was, the stronger stress response might be, consequently, the shorter survival time was. The results not only indicated the negative correlation between survival time and body weight, but also suggested that it would be dead if the stress-induced loss of body weight was more than 5.78% compared with the normals.3. The result of the changes on the parameters in stress group was revealed that chronic multiple stress might lead to a variety of systemic disorders.4. The level of ALP, TP in MudoEb5 positive mice and the level of TP, ALP, and Alb in MudoEb7 positive mice might be more liable to change in under chronic multiple stress.5. The concentration of zinc and magnesium might be lowered consequently by chronic multiple stress.6. There was probable inhibitions of chronic multiple stress on body weight, spleen index and hypoxia tolerance ability. Furthermore, weight, spleen index and hypoxia tolerance ability of MudoEb7 positive mice and weight, spleen index of the MudoEb5 positive mice, may be liable to change under chronic multiple stress.7. There might be some relation between stress-induced apoptosis in thymus and the inhibition on immunological function under chronic stress.8. The decrease in learning and memory ability of mice might be the result of chronic multiple stress.
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