Mounting and calibration of stairs on piezoelectric force platforms

To calculate the centre of pressure using piezoelectric force plates mounted on pads, no net tensile stresses may be imposed on the surface of the plate. This condition is violated when stairs are attached to the plates, unless the plates are preloaded. Typical shear forces encountered when climbing stairs were used to determine required preloads of approximately 16.4 N/cm step height. Vertical and horizontal loads were applied at known locations on the steps, and points of application were calculated. Deviations were within ± 3 mm. The effect of point of application inaccuracy on calculated joint moments is considerable. A 2 cm medial shift in the point of application resulted in calculated peak knee abduction/adduction moment errors of 35%.     

Nightly variation of periodic leg movements in sleep in middle aged and elderly individuals

This study investigated night-to-night variation in periodic leg movements in sleep (PLMS). PLMS are common in the elderly, but their mechanism and significance are not understood. Forty-five aged individuals (means = 69.7 years) were studied polysomnographically for 2 or 3 nights with surface electrodes placed above the anterior tibialis. Results indicated that PLMS varied considerably from night to night within individuals, though there was not a significant difference between nights for the entire group. Some evidence indicated that individuals with less severe sleep complaints showed greater nightly variation. The nightly variation in PLMS was over four times as large as the nightly variation in breathing disturbance in sleep, another condition common in the sleep of the aged. These data suggest that studies relating PLMS to other key variables (e.g. symptoms of disturbed sleep) should rely on multiple nights of data or, if single night data are used, be particularly careful to replicate findings across samples.     

The effect of different calcium antagonists and a calcium agonist on the metabolism of propranolol by isolated rat hepatocytes

Summary— The influence of the dihydropyridine calcium entry blockers nicardipine, amlodipine, nifedipine, isradipine and of the dihydropyridine calcium entry promotor BAY K 8644 on the disappearance rate of propranolol by isolated rat hepatocytes was compared to the effect of diltiazem and verapamil, two non-dihydropyridine calcium channel blockers and known inhibitors of hepatic cytochrome P450 mixed function oxidases. All compounds dose-dependently inhibited the disappearance rate of propranolol. Nicardipine and isradipine were more potent in inhibiting the disappearance rate of propranolol than the other dihydropyridines and than diltiazem and verapamil. The inhibitory effect of nicardipine on the disappearance rate of propranolol was not stereoselective and was not influenced by age.     

Interleukin-4 inhibits indoleamine 2,3-dioxygenase expression in human monocytes

Indoleamine 2,3-dioxygenase (IDO), a flavin-dependent enzyme that catalyzes the conversion of tryptophan to kynurenine, is induced in peripheral blood mononuclear cells by interferon-gamma (IFN gamma). Interleukin-4 (IL-4) is a cytokine that modulates the functional properties of monocytes/macrophages, and we investigated the effects of IL-4 on IDO. We showed that IL-4 inhibited the induction of IDO mRNA and IDO activity by IFN gamma in human monocytes. The inhibitory effect was evident with as little as 2 U/mL of IL-4. These results provide the first evidence that a cytokine can provide a negative signal for IDO expression and that IL-4 can influence the catabolism of tryptophan.     

Bone scintigraphy in chondroblastoma

Scintigraphy in 3 patients with chondroblastoma showed that the tumors were hyperemic and avidly accumulated the radionuclide. These changes were also present in adjacent normal bone, but to a lesser degree. This suggest that radionuclide uptake in chondroblastoma is a function of the blood supply to the tumor rather than primary matrix extraction.     

Congenital hepatic artery aneurysm simulating pancreatic carcinoma

The authors report a case of a hepatic artery aneurysm that simulated a mass in the head of the pancreas. The correct diagnosis was made preoperatively based on several findings: curvilinear calcification within the mass on CT, a well-defined cystic collection on ultrasound, absence of biliary duct dilatation or jaundice, and presence of other aneurysms.