Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The method of NMR spin echo in a combination with the impulse gradient of the magnetic field was used to study the self-diffusion of water isolated in the cells of lyophylized Criptococcus. A relative fall of the amplitude of spin echo (factor R) in relation to the value of magnetic field impulse gradient (g), their duration (delta) and temporary distance between them (delta). The studies were carried out in the temperature range of 20 degrees divided by 80 degrees C. It has been shown that the fraction of isolated mobile water is located in intracellular permeable compartments with an average size of 0.6.10--4 cm at 20 degrees C. The coefficient of selfdiffusion of isolated water of Criptococcus (0.25.10--5 cm2S--1 at 20 degrees C) and the activation energy of selfdiffusion (4.4 ccal/mole at 20 degrees divided by 60 degrees C) were determined, permeability of walls of water-containing compartments taken into account.
 ...
PMID:[Translation mobility of water isolated in the cells of lyophilized Cryptococcus albidus var. diffluens yeasts by the NMR impulse method]. 66 52

From measurements of the equilibrium spreading pressure pie for dispersions of lecithin--dimyristoyl (DML) or dioleoyl (DOL)--and cholesterol (CHOL) in water, we have deduced the phase relations in both the aqueous dispersions and the equilibrium surface films. At 29.5 degrees C, when the mole fraction of cholesterol in the dispersion chi(CHOL) is 0 chi(CHOL) less than chi(CHOL) less than 0.33, pie is constant and equal to the value for pure lecithin (DOL or DML). The phase rule predicts than two bulk lipid phases coexist; these are pure lecithin and lecithin:cholesterol 2:1 complex. The equilibrium surface film contants only lecithin and therefore lecithin and 2:1 complex are immiscible in surface films. When 0.33 less than chi/CHOL) less than 1.0, pie is also contant with a value intermediate between that for pure lecithin and cholesterol. In this range of lipid composition two bulk lipid phases also coexist: lecithin:cholesterol 2:1 complex and pure cholesterol. However, the equilibrium surface film contains only the 2:1 complex and, therefore, 2:1 complex is also immiscible with cholesterol in surface films. When pi less than pie, as in the case of spread films, we deduce that two surface phases may coexist; the composition of the phases will depend on chi(CHOL). When 0 less than chi(CHOL) less than 0.33, both lecithin and 2:1 complex coexist, and when 0.33 less than chi(CHOL) less than 1.0, 2:1 complex and cholesterol coexist. The "condensing" effect of cholesterol in lecithin surface films is reexamined. The effect is attributed to formation of the lecithin:cholesterol 2:1 complex and nonequilibrium conditions in the two-phase surface film.
 ...
PMID:Equilibrium studies of lecithin-cholesterol interactions. II. Phase relations in surface films: analysis of the "condensing" effect of cholesterol. 66 97

1. Changes in the water and ion contents of rabbit renal cortical slices, which had been bathed, immediately after slicing, in air-equilibrated media at room temperature ('freshly prepared slices'), were followed during subsequent incubation at 25 degrees C in oxygenated media of the same composition as the initial bathing medium. 2. In comparison with conventional 'equilibrated' slices (slices incubated at 25 degrees C in oxygenated ordinary medium immediately after slicing) these 'freshly prepared' slices had increased tissue water, sodium and chloride contents and low tissue potassium contents. 3. Control freshly prepared slices incubated at 25 degrees C in oxygenated ordinary medium recovered within 4 min to the tissue water content that is usual for rabbit renal cortical slices incubated in oxygenated ordinary medium at 25 degrees C. Freshly prepared slices incubated at 25 degrees C in oxygenated media containing 1 mM-oubain took 75 min or more to recover to this usual tissue water content. Thus the presence of 1 mM-oubain in both bathing and incubation media produced a marked inhibition of the volume recovery observed when freshly prepared slices are incubated in oxygenated media at 25 degrees C. 4. Reduction of the ouabain concentration reduced the inhibition of cell volume recovery. 5. Replacement of medium glucose by 3-O-methylglucose did not inhibit cell volume recovery in the absence of ouabain. 6. The oxygen consumptions of slices that were bathed and incubated in 1 mM-ouabain media were similar to those of slices initially bathed and incubated in ouabain-free media and then incubated in ouabain media. Thus the effect of ouabain in inhibiting cell volume recovery was unlikely to be secondary to inhibition of cellular energy production. 7. The tissue potassium content of slices incubated aerobically in 1 or 10 mM ouabin fell to an apparently stable value of approximately 100 m-mole/kg dry wt., which corresponds to a calculated concentration ratio of 10:1 across the cellular membrane, suggesting that some residual potassium uptake may still have been occurring. 8. These results indicate that in freshly prepared rabbit renal cortical slices ouabain-sensitive mechanisms play a major role in cell volume recovery. They are not in accord with the postulate that renal cortical cells possess a separate ouabain-insensitive mechanism regulating cell volume.
 ...
PMID:Ouabain and regulation of cellular volume in freshly prepared slices of rabbit renal cortex. 67 54

Bicarbonate appearance in the lumen and its relationship to solute absorption were studied in a Pavlov pouch in the cardiac region of the first compartment of the llama forestomach. HCO3- appearance showed no diurnal variation. HCO3- accumulation was highly dependent on the pH of the solution used. The HCO3- ion probably is formed from CO2 diffusing into the lumen from the serosal side, as a result of cell metabolism and of OH- ions. HCO3- accumulation was closely related to volatile fatty acid (VFA) absorption. The ratio of HCO3- appearance to VFA absorption depended on the pH of the solution. At a pH of 6.6, about 0.1 mol HCO3- and, at a pH of 7.8, 0.9 mol HCO3- appeared per mole absorbed VFA, indicating that at slightly alkaline pH nearly all H+ ions required for the nonionic absorption of VFA appeared to be delivered from the dissociation of H2CO3. Bicarbonate gain and VFA absorption were increased when animals were not fed for 48 h. Sodium absorption was related to VFA as well as water absorption.
 ...
PMID:Bicarbonate secretion and solute absorption in forestomach of the llama. 67 5

Deuterium nuclear magnetic resonance spectra of dimyristoylphosphatidylcholines specifically labeled in positions 2', 3', 4', 6', 8', 10', 12', and 14', of the 2 chain, of an N-deuteriomethylphosphatidylcholine, and of cholesterol-3alpha-d1, have been obtained by the Fourier transform method at 5.46 and 3.52 T on two "home-built" widebore superconducting magnet spectrometers, as a function of temperature and composition. Data on the specifically deuterium-labeled cholesterol molecule (in nonsonicated membrane systems) permits an estimate of the most probable angle of tilt of the sterol in the membrane, and evaluation of the order parameter (Salpha) describing rigid body motions in the bilayer. Segmental order parameters derived from the data presented allow calculation of individual chain segment projections onto the director axis and, consequently, estimation of effective chain length. It is shown that mathematical models which include chain tilt as well as those which neglect this type of rigid body motion give essentially identical results when applied to the dimyristoylphosphatidylcholine and dimyristoylphosphatidylcholine-cholesterol bilayer systems (in excess water, between 23 and 60 degrees C). Results of calculations of chain length and membrane thickness of a dimyristoylphosphatidylcholine-30 mol % cholesterol membrane system at 23 degrees C give excellent agreement when compared with recent high-resolution neutron diffraction data obtained on specifically deuterium labeled lecithin-cholesterol systems. No evidence for formation of lecithin-cholesterol complexes having lifetimes of approximately 30 ms has been found. Below the pure-lipid gel-liquid crystal phase transition temperature Tc but in the presence of cholesterol, we have obtained further evidence for 1-chain/2-chain nonequivalence. At 10 degrees C, the 2' segment of the 2 chain, but not the 2' segment of the 1 chain or the 3', 6', or 12' segments of the 2 chain, is broadened almost beyond detection. These results are in agreement with similar effects reported recently for the dipalmitoylphosphatidylcholine-cholesterol system and may indicate a bent configuration for the 2 chain, in the lecithin-cholesterol system. Further cooling below Tc results in loss of the 1-chain 2'-position signal intensity plus 2-chain 3', 6', and 12' signals simultaneously. The increase in length of the 2 chain of dimyristoylphosphatidylcholine upon addition of 30 mol % cholesterol of 23 degrees C is about 2.3 A. Addition of cholesterol to a choline-labeled lecithin results in complex behavior of the head group deuterium quadrupole splitting as a function of temperature, and cholesterol mole fraction. Above approximately 20 mol % cholesterol, the main effect is a decrease in quadrupole splitting as cholesterol content increases, the opposite effect to that observed with hydrocarbon chains.
 ...
PMID:Spectroscopic studies of specifically deuterium labeled membrane systems. Nuclear magnetic resonance investigation of the effects of cholesterol in model systems. 68 60

The mechanism of inclusion compound formation by dinoprostone (prostaglandin E2) with beta-cyclodextrin was studied by phase solubility analysis and PMR spectroscopy. As indicated by the linear increase of aqueous solubility of dinoprostone with beta-cyclodextrin concentration, some types of molecular interactions definitely exist between dinoprostone and the complexing ligands. The temperature dependence of a 1:1 complex formation constant yielded the following thermodynamic data at 20 degrees : deltaG degrees = -4.11 kcal/mole, deltaH degrees = 7.20 kcal/mole, and deltaS degrees = 10.5 e.u. Since water was the solvent system, these parameters appear to be largely determined by solvent reorganization through hydrogen bonding rather than solely by the binding of desolvated free dinoprostone and beta-cyclodextrin entities. PMR data indicate that dinoprostone is included within the cavity and also interacts with protons on the exterior of the beta-cyclodextrin molecule. A model consisting of a 1:1 complex, in which a dinoprostone molecule is partially included within the cavity and the remainder of the molecule extends around the edge of the opening of the cavity to the exterior of the beta-cyclodextrin molecule, is proposed as the most probable structure of this inclusion compound.
 ...
PMID:Phase solubility analysis and PMR study of complexing behavior of dinoprostone with beta-cyclodextrin in water. 72 76

1. Five subjects took 210 test meals of 750 ml. water containing 30--300 m-molal glucose or glycine, or 15--150 m-molal diglycine, or plain water. 2. The greater the concentration of solute, the greater was the volume of original meal recovered from the stomach after a fixed time. 3. On a molal basis glucose was half as effective as diglycine in slowing gastric emptying. This was consistent with the osmoreceptor being exposed to the diglycine after it had been split by the hydrolase of the cytosol of enterocytes (the absorbing cells of the small intestine). 4. The slowing of gastric emptying (ml./mole.1.) was about 10% greater for glycine than it was for glucose. There was apparently a threshold concentration below which glycine did not slow gastric emptying. 5. It was proposed that the response of the doudenal osmoreceptor might depend upon shrinking and swelling of the lateral intercellular space around the enterocytes.
 ...
PMID:Glucose, glycine and diglycine in test meals at stimuli to a duodenal osmoreceptor slowing gastric emptying. 72 78

Cholesterol and phospholipid are the two major lipids of the red cell membrane. Cholesterol is insoluble in water but is solubilized by phospholipids both in membranes and in plasma lipoproteins. Morever, cholesterol exchanges between membranes and lipoproteins. An equilibrium partition is established based on the amount of cholesterol relative to phospholipid (C/PL) in these two compartments. Increases in the C/PL of red cell membranes have been studied under three conditions: First, spontaneous increases in vivo have been observed in the spur red cells of patients with severe liver disease; second, similar red cell changes in vivo have been induced by the administration of cholesterol-enriched diets to rodents and dogs; third, increases in membrane cholesterol have been induced in vitro by enriching the C/PL of the lipoprotein environment with cholesterol-phospholipid dispersions (liposomes) having a C/PL of greater than 1.0. In each case, there is a close relationship between the C/PL of the plasma environment and the C/PL of the red cell membrane. In vivo, the C/PL mole ratio of red cell membranes ranges from a normal value of 0.09--1.0 to values which approach but do not reach 2.0. In vitro, this ratio approaches 3.0. Cholesterol enrichment of red cell membranes directly influences membrane lipid fluidity, as assessed by the rotational diffusion of hydrophobic fluorescent probes such as diphenyl hexatriene (DPH). A close correlation exists between increases in red cell membrane C/PL and decreases in membrane fluidity over the range of membrane C/PL from 1.0 to 2.0; however, little further change in fluidity occurs when membrane C/PL is increased to 2.0--3.0. Cholesterol enrichment of red cell membranes is associated with the transformation of cell contour to one which is redundant and folded, and this is associated with a decrease in red cell filterability in vitro. Circulation in vivo in the presence of the spleen further modifies cell shape to a spiny, irregular (spur) form, and the survival of cholesterol-rich red cells is decreased in the presence of the spleen. Although active Na-K transport is not influenced by cholesterol enrichment of human red cells, several carrier-mediated transport pathways are inhibited. We have demonstrated this effect for the cotransport of Na + K and similar results have been obtained by others in studies of organic acid transport and the transport of small neutral molecules such as erythritol and glycerol. Thus, red cell membrane C/PL is sensitive to the C/PL of the plasma environment. Increasing membrane C/PL causes a decrease in membrane fluidity, and these changes are associated with a reduction in membrane permeability, a distortion of cell contour and filterability and a shortening of the survival of red cells in vivo.
 ...
PMID:Influence of increased membrane cholesterol on membrane fluidity and cell function in human red blood cells. 72 75

In order to understand the thermodynamic state of simple salts in living cells, the mean activity coefficients of LiCl, NaCl, KCl, RbCl, CsCl were determined in concentrated isoionic bovine serum albumin (BSA) solutions by use of the EMF method with ion exchange membrane electrodes. The protein concentration range extended up to 22 wt%, whereas the salt concentration was kept constant at 0.1 mole per kilogram water. These solutions may be regarded as crude but appropriate model systems for the cytoplasm of cells as far as type and magnitude of the macromolecular component influence on the chemical potential of the salts is concerned. The mean stoichiometric activity coefficients of the alkali chlorides in the isoionic BSA solutions decreased linearly with the protein molality; this decrease, however, did not exceed ca. 10% compared with the pure 0.1 molal salt solutions. Only very small differences in the behavior of the different alkali chlorides were observed. The results may be interpreted by the superposition of the effects of specific Cl- ion binding to BSA and BSA bound "non-solvent" water with probably electrostatic long range interactions of the BSA(Cl-)nu polyions with the salt ions in solution. The resulting mean activity coefficients, corrected for ion binding and non-solvent water, showed a very slight linear dependence on the protein concentration. The departure from the value in the pure 0.1 molal salt solutions did not exceed +/- 2%.
 ...
PMID:Activity coefficients of salts in highly concentrated protein solutions. I. Alkali chlorides in isoionic bovine serum albumin solutions. 75 2

Human lymphocytes were equilibrated for 48 hours over a wide range of external potassium levels, and their contents of potassium, sodium, and water determined. As external potassium rose from zero, cell potassium rose steeply in a sigmoidal fashion, reached half-saturation at 0.4 mM esternal potassium, and then saturated at 129 mmoles/kg cells. The saturable cell potassium exchanged mole-for-mole with sodium. Analysis of the saturable components by a statistical-mechanical adsorption model demonstrated a cooperative intraction between sites determining equilibrium potassium-sodium distribution. Superimposed upon the saturable fraction of cell potassium was a smaller one that was non-saturable with increasing external potassium to at least 64 mM, and that, when expressed as mmoles/liter cell water, existed in a ratio to external potassium of 0.6. The results strongly support the association-induction hypothesis, which predicts a small non-saturable component of ions determined by exclusion from oriented cell water and a cooperative interaction between sites throughout the cell that associate with potassium or sodium.
 ...
PMID:Potassium-sodium distribution in human lymphocytes: description by the association-induction hypothesis. 76 4


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>