Abstract. Van Oosterwijck J, Nijs J, Meeus M, Lefever I, Huybrechts L, Lambrecht L, Paul L (Vrije Universiteit Brussel, Brussels; Artesis University College Antwerp, Antwerp; University Hospital Brussels, Brussels; Private Practice For Internal Medicine, Ghent ⁄ Aalst; CVS Contactgroep, Bruges; Belgium; and University of Glasgow, Glasgow, UK). Pain inhibition and postexertional malaise in myalgic encephalomyelitis ⁄ chronic fatigue syndrome. J Intern Med 2010; 268: 265-278.Objectives. To examine the efficacy of the pain inhibitory systems in patients with myalgic encephalomyelitis ⁄ chronic fatigue syndrome (ME ⁄ CFS) during two different types of exercise and to examine whether the (mal)functioning of pain inhibitory systems is associated with symptom increases following exercise.Design. A controlled experimental study.Setting and subjects. Twenty-two women with ME ⁄ CFS and 22 healthy sedentary controls were studied at the Department of Human Physiology, Vrije Universiteit Brussel.Interventions. All subjects performed a submaximal exercise test and a self-paced, physiologically limited exercise test on a cycle ergometer. The exercise tests were undertaken with continuous cardiorespiratory monitoring. Before and after the exercise bouts, subjects filled out questionnaires to assess health status, and underwent pressure pain threshold measurements. Throughout the study, subjects' activity levels were assessed using accelerometry.Results. In patients with ME ⁄ CFS, pain thresholds decreased following both types of exercise, whereas they increased in healthy subjects. This was accompanied by a worsening of the ME ⁄ CFS symptom complex post-exercise. Decreased pressure thresholds during submaximal exercise were associated with postexertional fatigue in the ME ⁄ CFS group (r = 0.454; P = 0.034).Conclusions. These observations indicate the presence of abnormal central pain processing during exercise in patients with ME ⁄ CFS and demonstrate that both submaximal exercise and self-paced, physiologically limited exercise trigger postexertional malaise in these patients. Further study is required to identify specific modes and intensity of exercise that can be performed in people with ME ⁄ CFS without exacerbating symptoms.

The application of a human somatomedin-C radioimmunoassay for the determination of somatomedin-C in chicken plasma has been examined. Parallel inhibition of binding of 125I-labelled somatomedin-C to antisera raised against somatomedin-C was observed with acid-treated human and chicken plasma. The concentration of immunoreactive (IR)-somatomedin-C in the plasma of the domestic fowl appears to be GH dependent. Plasma concentrations of IR-somatomedin-C were reduced after hypophysectomy and partially restored by replacement therapy with chicken GH. The age/development pattern of circulating concentrations of IR-somatomedin-C has been determined in normal and dwarf strains of domestic fowl. Increases in the plasma concentration of IR-somatomedin-C were observed between 1 and 6 weeks of age in control male domestic fowl of either heavy (broiler type) or light (White Leghorn) strains. Thereafter, the plasma concentrations of IR-somatomedin-C remained constant in the heavy strain birds but declined in White Leghorn chicks. Plasma concentrations of IR-somatomedin-C were reduced in sex-linked dwarf chickens, in both light and heavy strains of fowl, but were unaffected in autosomal dwarf chickens.

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Sprague-Dawley (SD) rats kept at room temperature do have a higher growth rate and food conversion compared to Wistar rats. Mean hormone level in blood samples collected every four hours during a 24 hour period do differ between both strain of rats. So, the mean circulating levels of T3, T4 and corticosterone are significantly lower, whereas prolactin concentrations are higher in SD-rats. Following acute cold exposure comparable increases in plasma T3 and T4 are seen in both strains after 3-5 hours. Prolactin plasma concentrations are decreased after 5 and 9 hours but only in SD-rats, whereas they remain unchanged in Wistars. Acclimation to 4 degrees C during 3 and 8 weeks resulted in a decreased growth rate of the SD-rats, which becomes comparable to Wistar animals, but food conversion is lower and food intake higher in SD-rats. A decrease in circulating levels of T4 is present in Wistars resulting in a significantly lower figure at 8 weeks of cold acclimation, whereas at the same time T3 is increased. Prolactin is decreased in SD-rats and increased in Wistars causing at 8 weeks of cold acclimation higher levels in Wistars. Corticosterone levels remain higher in Wistar rats and are comparable to rats kept at room temperature. It is concluded that the differences in growth rate, food conversion and food intake are related to the endocrine differences and responses observed.

Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and somatomedin C were measured in 28-day-old fat and lean lines of broilers produced by selection for high and low concentrations of very low density lipoproteins (VLDL). The effects of daily injections of corticosterone on the concentrations of these hormones and on fattening were compared in the two lines. The selection procedure had no effect on the concentrations of any of the hormones. However, daily rhythms in concentrations of plasma corticosterone, tri-iodothyronine (T3) and prolactin were less often observed in the fat line than in the lean line. No differences were seen between lines in the daily rhythms in plasma thyroxine (T4) and somatomedin C. Daily injections of 2500 micrograms corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight. This dose of corticosterone also increased abdominal fat pad and liver weights expressed as a percentage of body weight. The liver and fat pad responses to 2500 micrograms corticosterone in both lines were greater when the steroid was injected at the end rather than towards the beginning of the 14-h daily photoperiod. There was no difference between the lines in the fattening response to corticosterone. Lower doses of 100 and 500 micrograms corticosterone per day did not induce fattening or affect concentrations of plasma prolactin. They did, however, depress concentrations of plasma T3. Concentrations of plasma T4 were increased in both lines treated with 2500, but not with 100 or 500 micrograms corticosterone, towards the beginning of the daily photoperiod.(ABSTRACT TRUNCATED AT 250 WORDS)