Proton relaxation studies of water compartmentalization in a model neurological system.

Proton relaxation measurements from 18 crayfish abdominal nerve cords (a model of human CNS) are used to demonstrate that the transverse (though not the longitudinal) relaxation can be decomposed into four reproducible components that, in conjunction with optical and electron microscopy of the morphology, can be assigned to three water compartments within the cord and possibly to the mobile lipid protons. The assignments are extraaxonal water protons (32 +/- 9% and mean T2 = 600 +/- 200 ms), axonal water protons (59 +/- 12% and mean T2 = 200 +/- 30 ms), intramyelinic water protons (7 +/- 4% and mean T2 = 50 +/- 20 ms), and finally an unsubstantiated assignment of lipid protons (2.0 +/- 2.0% and mean T2 = 7 +/- 4 ms).

Multiexponential proton relaxation in model cellular systems.

Water proton relaxation measurements obtained from model cellular systems composed of red blood cell (RBC) ghosts are presented. The purpose of the investigation was to evaluate hypotheses concerning the possible sources of multiple exponential components in similar relaxation measurements made on tissue. Both laboratory frame transverse and longitudinal relaxation rates, as well as rotating frame relaxation rates, were measured in preparations of RBC ghosts and "extracellular fluid" that were, (a) uniformly mixed or (b) compartmentalized by layering, as the concentration of serum albumin was varied in the "extracellular fluid." The data show that although transmembrane exchange is too fast to give rise to multiexponential relaxation, multiple components can result from compartmentalization at the level of the cellular organization and do not necessarily require different tissue types. In addition, the data clearly demonstrate the importance of protein adsorption to cellular membranes as a determinant of the concentration of freely mobile solute protein molecules in tissue fluids.

The density of microflora in the oral and pharyngeal cavities.

A method for quantitative assessment of the microbial density on the mucous membranes in the oral and pharyngeal cavities is described. The results of the assessment are in agreement with the theoretical assumption based on the existence of a natural electrostatic filter. The highest density of microbes is on the tonsils where the positive pole of the filter is situated, so that a synergism between the defensive immunological role of the tonsils and the bioelectric potential pattern is obvious. The microbial densities in the oral cavity are more or less interdependent whereas the findings on the pharynx rear wall are isolated being probably perturbed by repeated swallowing.