Determination of total body water by multifrequency bio-electric impedance: development of several models

Multifrequency bio-electronic impedance analysis (MF BIA) measurements are taken from a heterogeneous group of patients, varying in size between obese and slim. The measuring system uses four electrodes: two current and two potential electrodes. Three new models are developed to calculate total body water (TBW) from the BIA data, and the resulting TBW values are compared with TBW determined by D₂O dilution. The results demonstrate that the most simple model provides the best TBW values. For individual patients, TBW can be determined by means of bioimpedance measurement with an accuracy of 3 litres. In the most simple model (model 1), the body is electrically represented by a cylinder, and corrections are made for the amount of fat. This is an extension of the model used by Xitron. In the more advanced models (2 and 3), the body is represented by a cylinder for the trunk, and truncated cones represent the arms and legs. In model 2, ΔTBW amounts to 3 litres. It is shown that the resistance of the trunk is proportional to the square root of the length. In model 3, it is assumed that subcutaneous fat is a poor conductor if electric current. An equation is developed that describes the partition of subcutaneous fat, and the fat layer is then removed from the cones representing arms and legs and from the cylinder that models the trunk.     

Respiratory function changes after asbestos pleurisy.

Six patients with radiographic evidence of diffuse pleural thickening after industrial asbestos exposure are described. Five had computed tomography of the thorax. All the scans showed marked circumferential pleural thickening often with calcification, and four showed no significant evidence of intrapulmonary fibrosis (asbestosis). Lung function testing showed reduction of the inspiratory capacity and the single-breath carbon monoxide transfer factor (TLCO). The transfer coefficient, calculated as the TLCO divided by the alveolar volume determined by helium dilution during the measurement of TLCO, was increased. Pseudo-static compliance curves showed markedly more negative intrapleural pressures at all lung volumes than found in normal people. These results suggest that the circumferential pleural thickening was preventing normal lung expansion despite abnormally great distending pressures. The pattern of lung function tests is sufficiently distinctive for it to be recognised in clinical practice, and suggests that the lungs are held rigidly within an abnormal pleura. The pleural thickening in our patients may have been related to the condition described as "benign asbestos pleurisy" rather than the interstitial fibrosis of asbestosis.     

Changes in pancreatic morphology associated with aging

Retrograde pancreatography has been carried out at necropsy in 120 cases and the results have been analysed in statistical detail. With increasing age, changes in pancreatic anatomy occur which must not be taken to indicate pathology. These changes are: (1) low or ptotic position of the pancreas so that the papilla of Vater is below the level of L3; (2) calcification of the splenic and superior mesenteric arteries which produce calcific densities around the pancreas; (3) increasing width of main pancreatic duct along its whole length at about 8% per decade; in the elderly, widths of 1 cm can occur in the main duct in the head of the pancreas without evidence of obstruction; (4) formation of ductular ectasia which affects mainly the interlobular ductules but also intralobular ductules; (5) some ectatic ducts reach the dimensions of cysts, ie, 1-2 cm in diameter.OTHER MORPHOLOGICAL CHANGES WHICH HAVE BEEN DEMONSTRATED AND WHICH MAY PRODUCE DIFFICULTIES IN RADIOLOGICAL INTERPRETATION ARE: (a) narrowed ducts not due to stricture; (b) space-occupying lesions due to superior mesenteric artery, splenic artery, aorta, vertebral osteophytes, sympathetic ganglion, and lymph nodes; (c) metastases in the pancreas-these must be distinguished from primary pancreatic carcinoma.The implications of these findings for endoscopy and isotope pancreatic scanning will be mentioned.     

Radiology of nasopharyngeal carcinoma

Plain film radiography and pluridirectional tomography have been displaced by CT and MRI for imaging NPC. The latter techniques are to some extent complementary, since MRI is particularly useful for defining soft-tissue components and CT accurately delineates bone erosion. CT, however, also provides good soft-tissue definition in conjunction with contrast enhancement. Nuclear isotope scanning is valuable in detecting bone metastases. These imaging techniques are of particular value in detecting submucosal tumors not visible clinically and are also essential to accurate tumor staging.     

Effect ofN-methyl-N'-nitro-N-nitrosoguanidine on the gastric mucosal barrier in rats

The gastric mucosal barrier to hydrogen ion (H⁺) after the administration ofN-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on the rat stomach was studied. Increased H⁺ backdiffusion was observed 3 hr after oral doses of 1 mg of MNNG over a 3-day period. MNNG in concentrations of 250 μg/ml, 167 μg/ml, 86 μg/ml, and 50 μg/ml in the presence of acid caused increased H⁺ back-diffusion across the gastric mucosa within 1 hr. Gastric mucosal barrier disruption by MNNG may play a pathogenic role in gastric carcinogenesis.