Studies on the lithium transport across the red cell membrane. I. Li+ uphill transport by the Na+-dependent Li+ counter-transport system of human erythrocytes

Li+ net-transfer across cell membranes was studied on human erythrocytes and ghosts preloaded with 1-2 mM Li+ and incubated in saline media of varying composition at initial thermodynamic equilibrium for Li+. The following results were obtained: 1. Li+ is extruded from glycolyzing erythrocytes against an electrochemical gradient until a steady-state Li+ distribution is established after 24-28 h. 2. The initial rate of Li+ extrusion is not altered by ouabain or by reduction of ATP levels to less than 25% of the normal value. 3. Replacement of external Na+ by K+ or choline+ abolishes the establishment of an electrochemical Li+ gradient. 4. The Li+ distribution ratio Lie+/Lii+ increases proportional to the ratio Nae+/Nai+ at constant extravellular K+ concentrations. 5. In ghost suspension an uphill Li+ transport is driven by an oppositely directed Na+ gradient. The direction of the Li+ uphill transport can be reversed by reversing the Na+ gradient. From the results it is concluded that the Li+ uphill transport across human red cell membranes is mediated by a Na+-dependent Li+ counter-transport system. This system is not inhibited by ouabain and does not appear to be identical to the Na+-Na+ exchange system described by Garrahan and Glynn.     

Use of magnetic resonance imaging to study the binding of manganese ions in brine-cured pork

Saturation recovery Magnetic Resonance Imaging (MRI) has been used to study the dependence of the water proton NMR longitudinal relaxation rate (T₁⁻¹) on Mn²⁺ concentration in pork which had been cured with 53, 102, and 193 mg g⁻¹ NaCl solutions. Those data are discussed in the context of meat swelling, determined independently by gravimetric water uptake. The utility of manganese ions as a paramagnetic tracer to probe the ability of brined pork to bind Mn²⁺ ions was further demonstrated in a two-dimensional inter-diffusion experiment which visualized perfusion of a given manganese ion concentration through a cylindrical sample of 102 mg g⁻¹ NaCl cured pork.     

Metabolism of acyclic and cyclic N-nitrosamines in cultured human bronchi

The metabolism of carcinogenic N-nitrosamines was studied in normal-appearing bronchial specimens obtained from 4 patients. Explants of bronchi were cultured in a chemically defined medium for 7 days. N-Nitrosamines [N-nitrosodimethylamine (DMN), N-nitrosodiethylamine (DEN), N,N'-dinitrosopiperazine (DNP), N-nitrosopyrrolidine (NPy), and N-nitrosopiperidine (NPd)] labeled with 14C were each then added at 100 mumoles for 24 hours. Measurable CO2 was formed by bronchial explants from: 1) DMN, DEN, and NPy in all 4 patients; 2) DNP in 3 of 4 patients; and 3) NPd in only 1 of 4 patients. In all bronchial specimens, these N-nitrosamines and/or their metabolites bound to bronchial mucosal DNA and protein. Binding levels were higher to protein than to DNA. Binding levels of DNP were as high as those with the two acyclic N-nitrosamines DMN and DEN, but binding levels of NPy and NPd were lower. Human bronchus was shown to metabolize and bind acyclic and cyclic N-nitrosamines found in the environment and in tobacco smoke.     

Recognition of shiny dielectric objects by analysing the polarization of reflected light

The degree of polarization of light reflected from a transparent or translucent object depends only upon the angle of incidence, refractive index and absorption coefficient of the material. It is therefore possible to determine the orientation of the surface normal from the direction of the plane of polarization. The feasibility of this is demonstrated both theoretically and practically by calculating and measuring the reflectance map of a sphere when viewed through a plane polarizing filter. Ambiguities in the mapping from radiance to orientation are removed by orienting the filter at three angles. The orientation of our objects is determined to within an uncertainty of less than seven degrees.