A mathematical model of transport in the renal medullary microcirculation was used to investigate the role of the UTB urea transporter expressed in descending vasa recta (DVR) endothelia and red blood cell (RBC) membranes. Our simulations suggest that UTB raises RBC and plasma and interstitial urea concentrations by facilitating radial diffusion of the solute and therefore serves to increase th...

RADFORD, EDWARD P., JR. Factors modifying water metabolism in rats fed dry diets. Am. J. Physiol. 196(s) : 1098-I 108. I959*To determine dietary factors which govern water turnover in rats, water intake and output were studied during q-hour intervals. Rats given water ad libitum and Purina laboratory chow or a synthetic diet voluntarily maintained an antidiuretic state, restricting water intake...

One of the most efficient water conservation mechanisms in mammals is the ability of the kidneys to produce concentrated urine for the elimination of waste products while losing a minimum of water. Depending on the food supply of differing animals, components of the glomerular ultrafiltrate are concentrated in the final urine to different extents. For example, carnivorous animals preferentially...

In this issue of Nephrology Dialysis and Transplantation, Sirich et al. provide evidence that 8-h treatments with large dialysers and higher dialysate flows greatly increase the clearances of protein-bound compounds p-cresol sulphate and indoxyl sulphate without altering Kt/V urea [1]. Thus, this paper is a further striking example of the limitations of urea-based dialysis ‘dosing’ and allows u...

Absorption of urea in the renal inner medullary collecting duct (IMCD) contributes to hypertonicity in the medullary interstitium which, in turn, provides the osmotic driving force for water reabsorption. This mechanism is regulated by vasopressin via a cAMP-dependent pathway and activation of a specialized urea transporter located in the apical membrane. We report here the cloning of a novel u...

We use long multiple trajectories generated by molecular dynamics simulations to probe the stability of oligomers of A 16–22 (KLVFFAE) peptides in aqueous urea solution. High concentration of urea promotes the formation of -strand structures in A 16–22 monomers, whereas in water they adopt largely compact random coil structures. The tripeptide system, which forms stable antiparallel -sheet stru...

partial replacement of formaldehyde with furfural in the urea-formaldehyde resin on the formaldehydeemission, physical and mechanical properties of particleboard was investigated. the modulus ofrupture (mor), modulus of elasticity (moe), internal bond (ib), water absorption (wa), thicknessswelling (ts) and formaldehyde emission (fe) of poplar particleboards made with the modifiedresins were mea...

As a first step in simulating solvent denaturation, we compare two possible potentials for urea; one based directly on a parameterization for proteins and another generated from ab initio, quantum calculations. Our results, which are derived from numerous, 1 ns simulations, indicate that both potentials reproduce essentially the same observed water structure ~as evident in radial distribution f...

Free energies of pairwise hydrophobic association are simulated in aqueous solutions of urea at concentrations ranging from 0-8 M. Consistent with the expectation that hydrophobic interactions are weakened by urea, the association of relatively large nonpolar solutes is destabilized by urea. However, the association of two small methane-sized nonpolar solutes in water has the opposite tendency ...