Impaired associative learning in chronic fatigue syndrome.

Patients with chronic fatigue syndrome (CFS) report cognitive difficulties (impaired attention, memory and reasoning). Neuropsychological tests have failed to consistently find cognitive impairments to the degree reported by CFS patients. We tested patients with CFS and sedentary controls in protocols designed to measure sensory reactivity and acquisition of the classically conditioned eyeblink response. Patients with CFS exhibited normal sensitivity and responsivity to acoustic stimuli. However, CFS patients displayed impaired acquisition of the eyeblink response using a delayed-type conditioning paradigm. Sensitivity and responsivity to the airpuff stimulus were normal. In the absence of sensory/motor abnormalities, impaired acquisition of the classically conditioned eyeblink response indicates an associative deficit. These data suggest organic brain dysfunction within a defined neural substrate in CFS patients.

Metabolic and cardiovascular effects of a progressive exercise test in patients with chronic fatigue syndrome.

PURPOSE: To evaluate the aerobic power (as maximum volume of oxygen consumed [VO2 max]) of women with chronic fatigue syndrome (CFS). PATIENTS AND METHODS: Twenty-one women with CFS and 22 sedentary healthy controls (CON) were studied at the CFS Cooperative Research Center Exercise Laboratory at the VA Medical Center, East Orange, New Jersey. Performance was measured on an incremental treadmill protocol walking to exhaustion. Expired gases were analyzed by a metabolic system, heart rate was recorded continuously, and ratings of perceived exertion (RPE) were taken at each workload. The groups were divided into those who achieved VO2 max (CFS-MAX and CON-MAX) and those who stopped at a submaximal level (CFS-NOMAX and CON-NOMAX) by using standard criteria. RESULTS: Seventeen CON and 10 CFS subjects achieved VO2 max. The VO2 max (mL/kg/min) of the CFS-MAX (28.1 +/- 5.1) was lower than that of the CON-MAX (32.1 +/- 4.3, P = 0.05). The CFS-MAX achieved 98 +/- 11% of predicted VO2 max. The CFS group had a higher RPE at the same absolute workloads as controls (P < 0.01) but not the same relative workloads. CONCLUSION: Compared with normal controls, women with CFS have an aerobic power indicating a low normal fitness level with no indication of cardiopulmonary abnormality. Our CFS group could withstand a maximal treadmill exercise test without a major exacerbation in either fatigue or other symptoms of their illness.

Effect of acute exhausting exercise on cytokine gene expression in men.

Because of recent interest in the effects of physical exercise on immunologic function, we decided to use state-of-the-art methods to evaluate cytokines in the peripheral blood leukocytes (PBLs) of 7 men before and after a maximal treadmill stress test. Change in cytokine gene expression was quantified from PBLs using a reverse transcriptase polymerase chain reaction assay (RT-PCR). In contrast to reports on serum levels or using in vitro testing, direct gene expression of TNF-alpha decreased after the stress test (p < 0.008). However, the 47% decrease was relatively small and of questionable biological significance. Levels of IL-1a, IL-1b, IL-2, IL-4, IL-6, IL-10, and INF-gamma did not change.

Computer use, computer training, and employment. Outcomes among people with spinal cord injuries.

Computer use and training may be of special benefit to people with spinal cord injuries (SCIs) because computer technology may help lessen the impact of mobility limitations that are inherent with this disability. This article summarizes several findings from a 1994 survey conducted of New Jersey residents who suffered SCIs within the previous 10 years. The results indicate that, among people with SCIs, 46% currently use a computer in some capacity and 22% received computer training since the date of their injury. Perhaps surprisingly, both corresponding percentages are higher in the general population. People with SCIs appear to have less access to computers because most people learn how to use computers at work, and only a minority of people with SCIs work. The lower rate of use of computers among people with SCIs is unfortunate because the steep employment and earnings declines often experienced after an SCI are partially mitigated for those who have computer skills. The results suggest the importance of policies and programs aimed at increasing access to computers and computer training for people with severe disabilities.

Vagal tone is reduced during paced breathing in patients with the chronic fatigue syndrome.

Patients with chronic fatigue syndrome (CFS) often complain of an inability to maintain activity levels and a variety of autonomic-like symptoms that make everyday activity intolerable at times. The purpose of the study was to determine if there were differences in vagal activity at fixed breathing rates in women with CFS. Twelve women with the diagnosis of CFS between the ages of 32 and 59 years volunteered for the study. Healthy women, who were between the ages of 30 and 49, served as controls. Full signal electrocardiograph and respiratory signals were collected during a paced breathing protocol of three fixed breathing rates (8, 12 and 18 breaths/min) performed in the sitting and standing postures. Vagal activity was analyzed by means of heart rate spectral analysis to determine the subject's response to specific breathing rates and postures. Heart rate variability was used as a non-invasive method of measuring the parasympathetic component of the autonomic nervous system. Using this method, although there was significantly less vagal power in the sitting versus the standing postures for both groups, the overall vagal power was significantly lower (p < 0.034) in the CFS group versus healthy controls. Vagal power was also significantly lower (p < 0.01 to p < 0.05) at all breathing rates in both postures except while standing and breathing at 18 breaths/min. Knowledge of the differences in vagal activity for CFS patients may allow stratification for the analysis of other research variables.

Constant light extends life in hamsters with heart disease.

Our previous work has shown that constant light can prolong the life of hamsters with heart disease. Although we have seen this result several times, constant light was not protective in our most recent experiment. We undertook this study because we had changed some conditions. As in previous experiments, we found that life in constant light extended life for cardiomyopathic hamsters as compared with others living in a 12:12-hr light:dark environment. A second factor affecting survival was the number of hamsters in a group. Hamsters housed in groups of five lived longer than those housed in groups of two under the same lighting conditions. Data from one experiment suggested that a short photoperiod (6:18 light:dark) was also protective. Although these experiments indicate that the protective effects of different light:dark schedules are not simple ones, they are important because their use may prove to be a helpful adjunct in the treatment of congestive heart failure.

Effect of stress and food restriction on blood pressure and lifespan of Dahl salt-sensitive rats.

OBJECTIVE: To evaluate the long-term consequences of stress in rats with genetic hypertension. DESIGN: Rapp-Dahl salt-sensitive rats, maintained on a low-salt diet, were stressed periodically over 8 weeks during which time their blood pressures were measured. In experiment 1 both stressed and unstressed control rats were given ad libitum access to food. Because of significant differences in body weights, in experiment 2 the unstressed controls were pair-fed to maintain their food intake at a level similar to that of the stressed rats. METHODS: Rats were subjected to 2-h sessions of supine immobilization stress 5 days a week every other week for 8 weeks. Blood pressures were measured during non-stress weeks, at least 4 days after the last exposure to the stressor and at monthly intervals thereafter. Survival curves were also established. RESULTS: In experiment 1 stressed rats developed hypertension at a slower rate than controls and lived significantly longer, but also weighted significantly less than controls, presumably because of diminished food intake. In experiment 2, in which food intake was controlled, body weights were similar in the two groups of rats, and hypertension developed at the same rate in both groups. Survival curves were not significantly different. Food restriction extended life compared with free feeding. CONCLUSIONS: Stress need not have long-term, deleterious health consequences in rats with genetically inherited hypertension, whereas caloric restriction is protective.

A chronic stress state in rats: effects of repeated stress on basal corticosterone and behavior.

The chronic stress state has previously been defined as persistent visceral arousal coupled with behavioral abnormalities. To determine the number of stressor exposures necessary to induce a chronic stress state, male rats were given 2 hours of inescapable shock on 10, 7, 4, or 3 consecutive days. The 3-day stress group had the most pervasive changes in the variables measured: persistently elevated basal plasma corticosterone (CORT), continued weight loss in the post-stressor period, and abnormal behavior. More exposures to the stress regimen did not produce higher CORT levels or greater behavioral changes. Acutely stressed rats, exposed to 1 day of inescapable shock, had persistent CORT elevations without the other changes seen in the 3-day stress group. The data suggest that 3 days of our stress regimen are sufficient to produce a state of chronic stress and that some signs of this state begin to appear as early as the first exposure to our inescapable stress regimen.

Hamsters with coronary vasospasm are at increased risk from stress.

Results of earlier experiments suggested that hamsters with inherited heart disease were at a higher risk of succumbing to stress during the vasospastic, lesion-forming period of their lives rather than later when the process of congestive heart failure had begun. To test this hypothesis, we stressed cardiomyopathic hamsters (CMH) whose ages differed by about 3 months; the younger of the two groups of stressed hamsters was in the vasospastic phase of the disease. The stressor was cold immobilization in which stressor intensity was manipulated using two durations of cold exposure. Log rank survival curves revealed no difference in mortality with the more intense stressor. However, significantly fewer of the older hamsters succumbed to the less intense stressor (46% as compared with 85% of the younger CMHs). Examination of the hearts in the experiment where mortality rate was the same for both groups revealed evidence of cardiac dilatation, indicative of heart failure, only in the older hamsters following stress. Since the younger hamsters did not show these changes and since they, but not the older animals, have coronary microvascular spasm and an increased susceptibility to stress, it would appear that the process of coronary vasospasm should be viewed as an independent and additional risk factor in determining the consequences of stress. Because of the effects of stress in the younger cardiomyopathic hamster, we believe that a neural link--which can be activated by stress--may be involved in the pathogenetic process of coronary vasospasm.

Adrenocortical and behavioral responses to repeated stressors: toward an animal model of chronic stress and stress-related mental illness.

Research in chronic stress has been hampered by the absence of an operational definition for that condition. To explore possible criteria for chronic stress, we repeatedly exposed rats to 2 hr of tail shock per day. After several days, we found elevated prestress corticosterone levels and abnormal behavior, including decreased food consumption, fear-like suppression of activity immediately before stress, greater hesitancy to drop from a suspended wire, and decreased exploratory behavior in a novel environment. A less intensely stressed group of rats also had elevated prestress corticosterone levels, but not the abnormal behaviors that persisted in shocked rats after the stress sessions were discontinued. We propose that abnormalities in both adrenocortical function and behavior are a better marker for chronic stress than abnormalities in either of these systems alone. The animal model we have described may be useful for studying factors that contribute to development of chronic stress or PTSD.