Diffusion of Water in Biological Tissues

A method is presented for obtaining simple approximate solutions for the problem of self-diffusion in an ordered array of obstacles. Our results are compared with some previous exact and approximate solutions, and we find that our method agrees well with the exact results over a large range of the volume fraction of the obstructions. It is shown that there is an important distinction between measurements of the diffusion coefficient by the capillary flow method and the spin-echo method. The modifications for the spin-echo case are given and applied to recent measurements on the anisotropy of the self-diffusion of water in striated muscle and to measurements on cysts of the brine shrimp. The analysis shows that very large volume fractions of obstructive barriers are required in order to account for the reduction in the diffusion coefficient in biological systems. Thus this model analysis leads to the supposition that a substantial fraction (20- 40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. In either case, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. In the case of NMR methodology, the measuring times are such that the values for diffusion are often influenced by the presence of macromolecular structures (obstructions) within the cells. This suggests that obstructions make a significant contribution to the value of the NMR diffusion coefficient and that NMR may have practical value for the evaluation of obstruction effects

Release of Hemoglobin and Potassium from Human Red Blood Cells Treated with Triton X-100 Under the Critical Micellar Concentration

The action of detergents is thought to be connected primarily with micelle formation. However, detergent monomers can also effect biological systems. It was found in this study that human red blood cells can be disintegrated with Triton X-100 non-ionic detergent at a concentration of 0.007 %, lower than the critical micellar concentration (CMC). The time dependent release of hemoglobin and potassium was detected at 37°C and both were sigmoid in character. Although potassium was released faster than hemoglobin, a cooperative relationship between potassium and hemoglobin within the intact red blood cell is suggested by this observation

High-Resolution, Real-Space Imaging of Conformational Structures of Poly-L-Proline Helixes

In 1954, Edsall postulated that the imino-acid proline, which is a frequently found constituent of protein molecules, is a key determinant to the three-dimensional architecture of proteins. It not only should play a fundamental role in stabilizing helical structures of polypeptides, it should allow for sharp bends and even for a complete reversal of the direction of a helix looping back on itself. No direct evidence has yet been published to prove this prediction. Using scanning tunneling microscopy, we have presented high-resolution, real-space images of two conformations of poly-L-proline, where one structure clearly exhibits the predicted 180° back-folding behavior. The measured length, 1.89 nm, of the repeating unit cells agrees with available X-ray data for poly-L-proline I with cis-peptide bonds. We further observe aggregated poly-L-proline II, consisting of highly-ordered, periodically and parallel-linked trans-peptide chains which are 2.4 nm apart from each other. Stacking of these aggregates with their orientation rotated by 90° is also observed

Quasi-Elastic Scattering Studies of Water Diffusion

Quasi-elastic neutron scattering is a powerful method to study the dynamics of protons in biological systems. The technique has been used both for the study of water diffusion and protein motion. The neutron scattering measurements on water show that the translational and rotational diffusion coefficients in biological systems are reduced from bulk values. We review the measurements on water in frog muscle, cysts of artemia, and phycocyanin. Measurements on dry trypsin and trypsin-D2O solutions over the temperature range 75-300K show that there is proton motion at the one angstrom level even in the dry or frozen state

Effect of Ruminally-Protected Lysine Supplementation to Growing Cattle on Growth and Subsequent Finishing Performance

Objective: The objective of this study was to evaluate the effects of ruminally-protected lysine supplementation fed during the growing phase to cattle limit-fed a corn-based diet, and to evaluate the subsequent finishing performance. Study Description: For 77 days, a group of 338 steers limit-fed at 2.4% of body weight daily on a dry matter basis were allocated to treatments providing 0, 3, or 6 g/day of lysine from Smartamine ML (Adisseo, Alpharetta, GA), or containing blood meal plus ruminally-protected methionine from Smartamine M. Growth performance was measured over the growing period. Cattle were then shipped to a commercial feedlot and fed without treatment until slaughter. Finishing performance was gathered from carcass data. Results: Steers supplemented with 3 g/day of lysine appeared to have the greatest response during the growing phase, having the heaviest body weights on day 77, and greatest average daily gains and gain:feed ratios. In the finishing phase, cattle that received 3 g/day of lysine during the growing phase maintained the weight advantage, relative to the control, established during the growing phase. Cattle receiving 6 g/day of lysine during the growing phase performed best during the finishing phase. Cattle receiving 3 and 6 g/day of lysine during the growing phase had carcasses that were 8 and 16 lb greater, respectively, than the control. The Bottom Line: When fed corn-based diets, supplementation of ruminally-protected lysine during the growing phase may improve growth performance of cattle during the growing and/or finishing phase, leading to improvement in greater carcass weights

Effects of Betaine on Protein Deposition in Growing Cattle with Modulated Methyl Group Status

Objective: This study was conducted to evaluate effects of guanidinoacetic acid and creatine supplementation in the presence or absence of supplemental betaine on lean tissue growth in growing cattle. Study Description: Seven ruminally cannulated Holstein steers (417 lb) were used in an experiment where each steer received each of six treatments. The first treatment set was conducted via abomasal infusion of a saline solution (control), 15 g/day guanidinoacetic acid (GAA), or 16.8 g/day creatine, and the second set was conducted via abomasal infusion of 0 or 5.6 g/day betaine; all treatment combinations were represented. Complete collection of urine and feces was used to determine nitrogen retention as a measure of protein deposition. Steers were limit-fed a corn-based diet similar to that of a production-type setting. Bottom line: Supplementing 5.6 g/day betaine increased lean tissue growth in growing steers fed corn-based diets

A uniform asteroseismic analysis of 22 solar-type stars observed by Kepler

Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure and evolution for the large sample of solar-type stars in the field. We perform a uniform analysis of 22 of the brightest asteroseismic targets with the highest signal-to-noise ratio observed for 1 month each during the first year of the mission, and we quantify the precision and relative accuracy of asteroseismic determinations of the stellar radius, mass, and age that are possible using various methods. We present the properties of each star in the sample derived from an automated analysis of the individual oscillation frequencies and other observational constraints using the Asteroseismic Modeling Portal (AMP), and we compare them to the results of model-grid-based methods that fit the global oscillation properties. We find that fitting the individual frequencies typically yields asteroseismic radii and masses to \sim1% precision, and ages to \sim2.5% precision (respectively 2, 5, and 8 times better than fitting the global oscillation properties). The absolute level of agreement between the results from different approaches is also encouraging, with model-grid-based methods yielding slightly smaller estimates of the radius and mass and slightly older values for the stellar age relative to AMP, which computes a large number of dedicated models for each star. The sample of targets for which this type of analysis is possible will grow as longer data sets are obtained during the remainder of the mission.Comment: 13 pages, 5 figures in the main text, 22 figures in Appendix. Accepted for publication in Ap