Intracellular water structure and mechanisms of cellular transport

The state of water in polarized and depolarized frog nerves a proton magnetic resonance study

The high resolution proton magnetic resonance spectrum of the sciatic nerve of the frog was studied in both the polarized and depolarized states. Paramagnetic salts were introduced into the system in order to separate the signals from the intra- and extracellular environments. It was determined that about 65% of the proton signal from the nerve trunk was accounted for by the intracellular environment in the polarized nerve trunk and that this percentage decreased to about 34% in the depolarized case. The temperature dependence of the line widths of the intracellular proton signal was studied. The enthalpy and entropy of activation for proton exchange between the intra- and extracellular environments were found to be 11.1 kcal/mole and -17.1 cal/deg-mole respectively. The pseudo-first-order rate constant for proton exchange between the intra- and extracellular environments was determined at 20 degrees C and shown to agree with the measured permeability coefficients of similar cells. Data are presented which indicate that the pseudo-first order rate constant for proton exchange between the two environments decreases upon depolarization of the nerve trunk and that the proton spin-spin relaxation time of the protons of intracellular water decreases significantly with depolarization. These results indicate a possibly quite important role of water in neural phenomena.

Osmotic properties of human lymphocyte

The osmotic properties of human lymphocytes isolated from 15 ml of venous blood were examined. Measurements of the permeability of the membrane to water under an osmotic gradient were also made. The Boyle-Van't Hoff relation held very well for the human lymphocyte when the cells were shrunken in hyperosmotic media to concentrations twice isosmotic. The volume of osmotically inactive material or "b" value averaged 32% of the mean corpuscular volume. These values were independent of temperature. Ponder's R ranged between 0.8 and 0.9. The average value for Lp, the hydralic coefficient was 0.46 mu/min atm +/- 0.02 (S.E.M.) at 25 degrees C. No significant effect of age, sex, or race was noted. The effect of temperature between 10 degrees C and 37 degrees C was measured and heats of activation between 11.1 and 17.4 kcal/mole were calculated with a mean of 14.1 kcal/mole +/- 1.6 (S.E.M.). Concanavalin A at 10 microgram/1.5 X 10(6) lymphocytes produced blastogenesis of 25% or more of the lymphocytes without clumping, agglutination, or toxicity. The mean corpuscular volume increased by 21% after 72 hours due to an increase in the "b" value which increased by 80%. The volume of free water remained constant. Histograms of the distribution of cell volumes showed that volume changes were uniform throughout the population with no evidence of agglutination of clumping. The significance of these results is discussed in the context of membrane fluidity and the state of intracellular water.

High-resolution radioautography of galactose-3H accumulation in rings of hamster intestine

Radioautography of water-soluble substances has posed a major technical problem for the past decade. Utilizing silicone-impregnated plastic sections of frozen-dried tissue, a quantitative method was developed for studying distribution of (3)H-labeled galactose, mannitol, and phlorizin. The content of a 2-micro band may be measured with an accuracy of +/-20% by light microscopy; radioautographs may also be prepared for the electron microscope. Results with intestinal tissue incubated 1-10 min in vitro and, then, frozen rapidly indicate that the first step in galactose absorption is uphill transport into the brush border of the columnar epithelium. Correction of galactose content for the mannitol space in the brush border suggests that the sugar pump is located at the surface of the microvilli. Further evidence for the surface locus of the glucose-galactose pump was obtained with phlorizin (next paper, reference 40). The galactose content of columnar cell cytoplasm always equalled that of microvilli and no transcellular diffusion gradient could be detected; during the first minutes of incubation, however, a gradient did exist between nucleoplasm and cytoplasm. Downhill exit of galactose from columnar cells may have proceeded either directly across basal membranes to adjacent lamina propria or indirectly via open intercellular spaces. Lastly, even in the absence of muscularis, the connective tissue of the lamina propria constituted enough of a diffusion barrier so that it served as a secondary accumulating compartment for galactose under present in vitro conditions.