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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sintering kinetics of insoluble anhydrite were studied by measuring the isothermal shrinkage of compacts of insoluble anhydrite powders in air. The sintering process of insoluble anhydrite powders consisted of two stages for the temperature range from 630 degrees C to 720 degrees C. The first shrinkage could be described as a bulk diffusion model and followed the equation delta L/Lo infinity t 0.5l +/- 0.08, where delta L/Lo is fractional shrinkage and t is the sintering time. The apparent activation energy of the shringage was 130 kcal/mole. The second shrinkage followed the equation delta L/Lo infinity t 1.83 +/- 0.30, but could not be explained with reasonable model. However, the SEM observations of the fractured surface of compacts suggested that the second shrinkage corresponded to the grain growth of insoluble anhydrite.
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PMID:[Thermal behavior of gypsum bonded investments. (Part 3) Sintering kinetics of insoluble anhydrite (author's transl)]. 29 Jul 10

The effects of Fab fragments of high-affinity specific antibodies have been studied in a canine experimental model of lethal digitoxin toxicity. Selected antiserum from sheep immunized and boosted with a digoxin-serum albumin conjugate contained antibodies that cross-reacted with digitoxin with an average intrinsic association constant of 1.4 x 10(10) M(-1) as determined by equilibrium dialysis. Rapid second-order association kinetics (k(f) = 3.7 x 10(6) M(-1) per s) and slow dissociation kinetics (k(r) = 1.9 x 10(-4) per s) were documented for the antibody-digitoxin complex. Eight dogs given 0.5 mg/kg digitoxin intravenously developed ventricular tachycardia after 23+/-4 (SEM) min. Control nonspecific Fab fragments were then given. All animals died an average of 101+/-36 min after digitoxin administration. Another eight dogs given the same digitoxin dose similarly developed ventricular tachycardia after 28+/-3 min. This group then received a molar equivalent dose of specific Fab fragments intravenously over 3 min, followed by a 30-min infusion of one-third of the initial dose. All dogs survived. Conducted sinus beats reappeared 18+/-4 min after initial Fab infusion, and stable normal sinus rhythm was present at 54+/-16 min. Plasma total digitoxin concentrations increased threefold during the hour after initial Fab infusion, while plasma free digitoxin concentration decreased to less than 0.1 ng/ml. Effects on digitoxin pharmacokinetics of these Fab fragments and the antibody population from which they were derived were further investigated in a primate species. Unlike common laboratory animals previously studied, the rhesus monkey was found to have a prolonged elimination half-life, estimated at 135 and 118 h by radioimmunoassay and [(3)H]digitoxin measurements, respectively, similar to man and thus providing a clinically relevant experimental model. Intravenous administration of 2 mol of specific Fab fragments per mole of digitoxin 6 h after 0.2 mg of digitoxin produced a rapid 4.3-fold increase in plasma total digitoxin concentration followed by a rapid fall (t((1/2)) 4 h) accompanied by a 14-fold enhancement of urinary digitoxin excretion over control values during the 6-h period after Fab was given. Analytical studies were consistent with increased excretion of native digitoxin rather than metabolites, and the glycoside was found in equilibrium dialysis studies to be excreted in the urine in Fab-bound form. Administration of 2 mol of specific antibody binding sites per mole of digitoxin as intact IgG caused a greater and more prolonged increase in plasma total digitoxin concentration, peaking 13-fold above control levels. In contrast to the effects of Fab, however, specific IgG reduced the rate of urinary digitoxin excretion substantially below control values. We conclude that Fab fragments of antibodies with high affinity for digitoxin are capable of rapid reversal of advanced, otherwise lethal digitoxin toxicity, and are capable of reducing the plasma half-life and accelerating urinary excretion of digitoxin.
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PMID:Reversal of advanced digitoxin toxicity and modification of pharmacokinetics by specific antibodies and Fab fragments. 91 99

Regulation of urea transport by vasopressin in inner medullary collecting duct (IMCD) cells is thought to be important for the urinary concentrating mechanism. Isolated tubule perfusion studies suggest the existence of a saturable urea carrier. We have measured 14C-urea efflux in IMCD cells which were freshly isolated and grown in primary culture. Cells were isolated from rat papilla by collagenase digestion and hypotonic shock. In suspended cells, 14C-urea efflux (Jurea) from loaded cells was exponential with time constant 59 +/- 3 sec (SEM, n = 6, 23 degrees C). Jurea had an activation energy of 4.1 kcal/mole and was inhibited 42 +/- 7% by 0.25 mM phloretin and 30-40% by the high affinity urea analogues dimethylurea and phenylurea. Jurea was increased 40-60% by addition of vasopressin (10(-8) M) or 8-bromo-cAMP (1 mM); stimulated Jurea was inhibited 55 +/- 8% by the kinase A inhibitor H-8. Phorbol esters and epidermal growth factor did not alter Jurea. IMCD cells grown in primary culture were homogeneous in appearance with greater than fivefold stimulation of cAMP by vasopressin. The exponential time constant for urea efflux was 610 +/- 20 sec (n = 3). Jurea was not altered by vasopressin, cAMP or phloretin. Another function of in vivo IMCD cells, vasopressin-dependent formation of endosomes containing water channels, was absent in the cultured cells. These results demonstrate presence of a urea transporter on suspended IMCD cells which is activated by cAMP and inhibited by phloretin and urea analogues. The urea transporter and its regulation by cAMP, and cAMP-dependent apical membrane endocytosis, are lost after growth in primary culture.
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PMID:Urea transport in freshly isolated and cultured cells from rat inner medullary collecting duct. 217 46

Titanium was polished using several chemical polishing baths containing different ratios of hydrofluoric acid and nitric acid. The meltage, surface roughness, and surface texture of titanium samples after chemical polishing were affected by the ratio of hydrofluoric acid and nitric acid. Generally the meltage increased and surface roughness decreased when the mole concentration of hydrofluoric acid was high and that of nitric acid was low. For example the chemical polishing bath containing 5 mole hydrofluoric acid and 5 mole nitric acid improved the surface texture in one minute, but SEM observation revealed a partially rough surface caused by the excessive solution. The chemical polishing bath containing 1 mole hydrofluoric acid and 5 mole nitric acid did not improve the surface texture in a short time because of low solubility, but improved the surface texture gradually with the extension of the immersion time and a good surface texture was observed by SEM. The chemical polishing using the chemical polishing bath with low solubility and immersion of the prosthetics for a rather long time were considered useful procedures to obtain a smooth surface of titanium prosthetics while maintaining their accuracy.
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PMID:[Polishing of titanium prosthetics (Part 6). The chemical polishing baths containing hydrofluoric acid and nitric acid]. 255 80

A sensitive RIA for LTB4 (which cross-reacts 60% with 6-trans LTB4) has been developed with a minimal detectable mass of 7.4 X 10(-15) mole. The properties of a second RIA more specific for 6-trans LTB4 are also described. The latter has utility in the measurement of the enzymatic and non-enzymatic transformations of LTA4 and in the characterisation of inhibitors of LTA4 epoxide hydrolase. Conditions for the direct RIA of immunoreactive LTB4 in human plasma are described. Addition of calcium ionophore, A23187, to human blood increased basal immunoreactive LTB4 levels from less than 100pg ml-1 to 259 +/- 23ng ml-1 (mean +/- SEM, n = 16). Extraction and RPHPLC confirmed that greater than 90% of immunoreactive LTB4 co-eluted with synthetic and [3H]LTB4. Pharmacological characterisation of immunoreactive eicosanoids revealed that in vitro the NSAIDs: aspirin, indomethacin, flurbiprofen and benoxaprofen did not inhibit LTB4 but inhibited TXB2, consistent with cyclo-oxygenase inhibition whereas the prototype mixed inhibitor BW755c inhibited both LTB4 and TXB2. This experimental paradigm may be used in the clinical measurement of the bio-availability of novel agents that inhibit eicosanoid biosynthesis.
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PMID:Radioimmunoassay of LTB4 and 6-trans LTB4: analytical and pharmacological characterisation of immunoreactive LTB4 in ionophore stimulated human blood. 301 87

Osmotic water permeability of the apical membrane of toad urinary epithelium is increased greatly by vasopressin (VP) and is associated with exocytic addition of granules and aggrephores at the apical surface. To determine the physiological role of granule exocytosis, we measured the osmotic water permeability and membrane fluidity of isolated granules, surface membranes and microsomes prepared from toad bladder in the presence and absence of VP. Pf was measured by stopped-flow light scattering and membrane fluidity was examined by diphenylhexatriene (DPH) fluorescence anisotropy. In response to a 75 mM inward sucrose gradient, granule size decreased with a single exponential time constant of 2.3 +/- 0.1 sec (SEM, seven preparations, 23 degrees C), corresponding to a Pf of 5 x 10(-4) cm/sec; the activation energy (Ea) for Pf was 17.6 +/- 0.8 kcal/mole. Under the same conditions, the volume of surface membrane vesicles decreased biexponentially with time constants of 0.13 and 1.9 sec; the fast component comprised approximately 70% of the signal. Granule, surface membrane and microsome time constants were unaffected by VP. However, in surface membranes, there was a small decrease (6 +/- 2%) in the fraction of surface membranes with fast time constant. DPH anisotropies were 0.253 (granules), 0.224 (surface membranes) and 0.190 (microsomes), and were unaffected by VP. We conclude: (1) granules have among the lowest water permeabilities of biological membranes, (2) granule water permeability is not altered by bladder pretreatment with VP, (3) granule membrane fluidity is remarkably lower than that of surface and microsomal membranes, and (4) rapid water transport occurs in surface membrane vesicles. The unique physical properties of the granule suggests that apical exocytic addition of granule membrane may be responsible for the low water permeability of the unstimulated apical membrane.
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PMID:Very low osmotic water permeability and membrane fluidity in isolated toad bladder granules. 314 39

The Eimer's organ and adjacent structures and their changes after infraorbital axotomy was examined with LM, TEM and SEM in the Japanese shrew mole, Urotrichus talpoides. Approximately 3,000 of Eimer's organ covers the hairless snout tip of this animal. It protrudes to the corium from epidermis, and consists of column-shaped core and the cylindrical peripheral structures. About a dozen of naked fibers ascend vertically in the core; one or a few of them runs amidst the core and the others along its circumferential part. Each fiber has shelf-like endings one in each of 5 to 7 succeeding cells in the upper part of the core. At the uppermost part of the core structure is an opaque degenerating cell. Neurites were considered to grow up with the epidermal cells to which their endings are attached. This pattern of nerve ending was clearly observed for the first time in this study. Usually 3 Merkel cells lie at the base of an Eimer's organ contacting with a soup-plate-shape nerve terminal. In the dermis, an encapsulated corpuscle enveloping a nerve endings is found underneath each Eimer's organ. After axotomy, ipsilateral nerve fibers and their endings totally disappeared from Eimer's organ in a week. Perforation in the domes, flattening of the dome surface, and degeneration of the encapsulated corpuscles appeared on the transected side. In addition to this, several features of degeneration also appeared on the contralateral side. It might be considered as an effect of disuse from the disorders of the other side.
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PMID:Ultrastructure of the Eimer's organs of the Japanese shrew mole, Urotrichus talpoides (Insectivora, Mammalia) and their changes following infraorbital axotomy. 340 Aug 78

The effect of temperature changes (36-40 degrees C) on the liver function was studied in the isolated perfused pig liver. When compared with control studies no effect was observed on lactate, glucose, bile flow, ATP and energy charge, and the recovery after the changes in temperature was complete. The only significant changes observed regarded the hepatic oxygen uptake and galactose elimination capacity. The increase of 1 degree C resulted in an increase in galactose elimination of 6%, corresponding to a Q10 of 1.98 (SEM 0.12) with an energy of activation of 48 kJ/mol (SEM 4.7). Oxygen uptake was linearly related to galactose elimination (1.75 mol for 1 mole change in galactose elimination). These results indicate that circulatory changes are unimportant within physiological temperature changes. It is concluded that temperature effects on galactose elimination are too small to warrant a correction when used as a clinical test of quantitative liver function.
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PMID:The effect of physiological temperature changes on the galactose elimination capacity of the isolated perfused pig liver. 374 57

Biliary lipid secretion rates were measured in non-obese and obese individuals with and without cholesterol gallstones, using a steady-state, amino acid duodenal perfusion method. In addition, biliary lipid secretion rates were measured in five obese gallstone patients receiving high-dose chenodeoxycholic acid therapy (16-22 mg day-1 kg-1). Bile acid secretion rates in the non-obese patients with cholesterol gallstones (563 +/- SEM 70 mumol/h, n = 6) were significantly lower than in the non-obese controls (1078 +/- 210 mumol/h, n = 10, P less than 0.05), whereas cholesterol secretion rates were similar in the non-obese individuals with and without gallstones (51 +/- 7 and 42 +/- 4 mumol/h respectively). In the obese, both with and without gallstones, the major abnormality was hypersecretion of cholesterol (107 +/- 7 mumol/h, n = 7, and 81 +/- 15 mumol/h, n = 7, respectively). Both these values were significantly greater than those in the non-obese controls (P less than 0.01-0.02). Biliary cholesterol secretion rates correlated significantly with bile acid secretion rates but, for every mole of bile acid secreted, the obese secreted more cholesterol than the non-obese. Chenodeoxycholic acid treatment lowered biliary cholesterol saturation in obese gallstone patients by reducing biliary cholesterol secretion. These results suggest that there are two major types of defect in biliary lipid secretion in gallstone patients: reduced biliary bile acid secretion in non-obese gallstone patients and excessive biliary cholesterol secretion in the obese.
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PMID:Bile lipid secretion in obese and non-obese individuals with and without gallstones. 406 57

Bilirubin diglucuronide (BDG) may be formed in vitro by microsomal UDP glucuronosyl transferase (EC 2.4.1.17)-mediated transfer of a second mole of glucuronic acid from UDP-glucuronic acid, or by dismutation of bilirubin monoglucuronide (BMG) to BDG and unconjugated bilirubin, catalyzed by an enzyme (EC 2.4.1.95) that is concentrated in plasma membrane-enriched fractions of rat liver. To evaluate the role of these two enzymatic mechanisms in vivo, [(3)H]bilirubin mono-[(14)C]glucuronide was biosynthesized, purified by thin-layer chromatography, and tracer doses were infused intravenously in homozygous Gunn (UDP glucuronyl transferase-deficient) rats or Wistar rats. Bilirubin conjugates in bile were separated by high-pressure liquid chromatography and (3)H and (14)C were quantitated. In Gunn rats, the (14)C:(3)H ratio in BDG excreted in bile was twice the ratio in injected BMG. In Wistar rats the (14)C:(3)H ratio in biliary BDG was 1.25 +/- 0.06 (mean +/- SEM) times the ratio in injected BMG. When double labeled BMG was injected in Wistar rats after injection of excess unlabeled unconjugated bilirubin (1.7 mumol), the (14)C:(3)H ratio in BDG excreted in bile was identical to the ratio in injected BMG. Analysis of isomeric composition of bilirubin conjugates after alkaline hydrolysis or alkaline methanolysis indicated that the bile pigments retained the IX(alpha) configuration during these experiments. The results indicate that both enzymatic dismutation and UDP glucuronyl transferase function in vivo in BDG formation, and that dismutation is inhibited by a high intrahepatic concentration of unconjugated bilirubin. This hypothesis was supported by infusion of [(3)H]bilirubin-monoglucuronide in isolated perfused homozygous Gunn rat liver after depletion of intrahepatic bilirubin by perfusion with bovine serum albumin (2.5%), and after bilirubin repletion following perfusion with 0.34 mM bilirubin. From 20 to 25% of injected radioactivity was recovered in BDG in bile in the bilirubin-depleted state; only 8-10% of radioactivity was in BDG in bile after bilirubin repletion. After infusion of [(3)H]bilirubin di-[(14)C]glucuronide in homozygous Gunn rats, 5-7% of the injected pigment was excreted in bile as BMG. The (14)C:(3)H ratio in the injected BDG was 10% greater than the (14)C:(3)H ratio in BMG excreted in bile. These results indicate that in vivo, dismutation rather than partial hydrolysis, is responsible for BMG formation. Incubation of [(3)H]bilirubin, BDG and a rat liver plasma membrane preparation resulted in formation of BMG (3.3 nmol/min per mg protein) indicating that dismutation is also reversible in vitro.
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PMID:Bilirubin diglucuronide formation in intact rats and in isolated Gunn rat liver. 680 Oct 91


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