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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of chloride in fluid transport of the rabbit corneal endothelium was examined by measuring changes in corneal thickness following ion substitutions or addition of ion transport inhibitors in media superfusing the isolated tissue. Normal fluid transport is indicated by maintenance of constant thickness in a fresh cornea or thinning (deturgescence) of a preswollen deepithelialized cornea to its initial thickness at approximately 40 microns/h. These patterns are seen when tissues are superfused with HCO(3-)-Ringer containing 114 mM Cl-. When Cl- was substituted with gluconate, glucuronate, or SO4(2-) fresh and preswollen corneas immediately thinned at greater than 150 microns/h to a value less than 300 microns and then began to swell at 30 microns/h to above their original thickness. Substitution of Cl- with NO3- or Br- had a negligible immediate thinning effect, but fresh corneas subsequently swelled and preswollen corneas failed to deturgesce fully. The rapid thinning (called a "downtransient") observed with gluconate, glucuronate, and SO4(2-) also occurred in these media when ion and fluid transport were completely inhibited with ouabain or stilbenes or by absence of HCO3-, indicating that the thinning results from osmotic gradients induced by ionic reflection coefficients different from that of Cl-. When the downstransient was avoided in deepithelialized corneas by preswelling with the same Cl(-)-free media on both sides of the cornea, corneas maintained a constant but swollen thickness in gluconate and in NO3- or Br- deturgesced slowly and incompletely; ouabain or stilbenes caused further swelling in all media. We conclude that absence of Cl- partially impairs fluid transport, most probably via its role in a Cl(-)-HCO3- exchanger which has been proposed in a recent model of endothelial fluid transport.
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PMID:Chloride is required for fluid transport by the rabbit corneal endothelium. 159 Mar 58

The fusion of large unilamellar phosphatidylserine liposomes (PS LUV) induced by La3+ has been monitored using the 1-aminoapthalene-3,6,8-trisulfonic acid/p-xylenebis(pyridinium bromide) (ANTS/DPX) fluorescence assay for the mixing of aqueous contents. The fusion event is extensive and nonleaky, with up to 95% mixing of contents in the fused liposomes. However, addition of excess EDTA leads to disruption of the fusion products in a way that implies the existence of metastable intermembrane contact sites. The maximal fusion activity occurs between 10 and 100 microM La3+ and fusion can be terminated rapidly, without loss of contents, by the addition of excess La3+, e.g., 1 mM La3+ at pH 7.4. This observation is explained by the very large intrinsic binding constant (approximately 10(5) M-1) of La3+ to the PS headgroup, as measured by microelectrophoresis. Addition of 1 mM La3+ causes charge reversal of the membrane and a large positive surface potential. La3+ binding to PS causes the release of a proton. These data can be explained if La3+ can chelate to PS at two sites, with one of the sites being the primary amino group. This binding model successfully predicts that at pH 4.5 fusion occurs up to 2 mM La3+, due to reduced La3+ binding at low pH. We conclude that the general mechanism of membrane fusion includes three kinetic steps. In addition to (a) aggregation, there is (b) the close approach of the surfaces, or thinning of the hydration layer, and (c) the formation of intermembrane intermediates which determine the extent to which membrane destabilization leads to fusion (mixing of aqueous contents), as opposed to lysis. The lifetime of these intermembrane intermediates appears to depend upon La3+ binding to both PS sites.
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PMID:La3+-induced fusion of phosphatidylserine liposomes. Close approach, intermembrane intermediates, and the electrostatic surface potential. 338 13

We have examined the collagens synthesized by cultures of normal human corneal stromal cells. Radioactively labeled products, accumulated in the culture medium during a 24-h labeling period, were treated with pepsin and analyzed by SDS-polyacrylamide gel electrophoresis. The cell layer collagen was characterized by 2.6 M and 4.4 M salt fractionation at neutral pH. CM-cellulose column chromatography, SDS-gel electrophoresis, and cyanogen bromide peptide mapping. Type I alpha 1 and alpha 2 chains were the predominant components in both the cell layer and the medium fractions of normal human stromal cultures; type III collagen was found mostly in the culture medium; and type V collagen was associated with the cell layer. Immunofluorescent techniques used to visualize collagen deposition in the cell layer confirmed the presence of these collagen types. Keratoconus is a disease characterized by thinning and scarring of the central cornea. Stromal cells grown from keratoconus corneas produced similar types of collagen (types I, III, and V) as normal human controls. Cells from keratoconus patients, however, contained more type V collagen in the cell layer than did normal cells. The difference was seen only in the 4.4 M salt precipitates. Since type V collagen is one component of cell surfaces, the primary defect in cultures from keratoconus corneas could involve cell membrane and cell surface components.
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PMID:Identification of collagens synthesized by cultures of normal human corneal and keratoconus stromal cells. 633 47

In recent years microvillar cells (MVC) have been identified in the olfactory epithelium of numerous species, including rodents, canines, and primates. However, there is no consensus on the morphologic or histochemical features of this cell, nor is the function of these cells currently known. Previous studies have examined MVC during development and in the mature olfactory epithelium, but not after toxic insult. A microvillar cell, defined by specific morphologic criteria, was studied in adult male Long-Evans rats exposed via inhalation to either 200 ppm methyl bromide for 4 h/day, 4 days/week for 2 weeks, or to 635 micrograms/m3 nickel for 6 h/day for 16 consecutive days, and sacrificed serially over several months. The pattern of recovery for MVC differed according to the severity and specificity of the insult to the olfactory epithelium. With methyl bromide, all cell types were completely depleted from olfactory epithelium immediately after injury, including MVC. MVC were slow to repopulate the epithelium, and appeared only when olfactory epithelium was complete in other respects. With nickel exposure, where the major effect was a gradual decrease in sustentacular cells with a thinning of the apical cytoplasm thickness, MVC showed a decline during exposure, but reappeared during recovery. In both cases, there was no difference in olfactory function, even when MVC were absent from the olfactory epithelium. A mature olfactory epithelium appears to be necessary to support the presence of this MVC, suggesting that it is not crucial to the regeneration processes or recovery of olfactory function, but perhaps plays some role, as yet undefined, in the unperturbed olfactory epithelium.
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PMID:Microvillar cells of the olfactory epithelium: morphology and regeneration following exposure to toxic compounds. 771 50

The effects of various additives on the microstructure evolution in hexadecyltrimethylammonium bromide micellar solution and its rheological properties are investigated. The additives considered in the present study are primary, secondary, and tertiary heptanols and sodium salicylate (NaSal). The microstructure is developed via the two-step shape transitions in the micellar solution; first, the initial spherical micelles undergo shape transition to rod-like or disc-like micelles as the micelles tend to be packed compactly with increase in the surfactant concentration; then further increment in the surfactant concentration makes the anisotropic rod-like micelles overlap each other. Solutions in these states exhibit typical non-Newtonian behaviors such as shear thinning at high shear rates. In the present study, the additive effects on the microstructure evolution are investigated by employing various techniques including a phase modulated flow birefringence, a dynamic light scattering and a dynamic oscillatory rheometry. The results show that addition of the solubilized additives enhances the microstructure transitions, which are affected by the additive concentration and its chemical structure. Presence of the cosurfactants such as heptanols with hydrophobic alkyl chains reduces the repulsion by forming surfactant-alcohol mixed micelles. The primary heptanol can penetrate easily into the micelles and aligned parallel to the surfactant molecules compared with the secondary and tertiary heptanols. Thus, the primary heptanol enhances the two-step shape evolutions more effectively than the other types. In the presence of NaSal, on the other hand, the micellar solution exhibits the viscoelastic properties and the yield stress owing to the formation of networked or worm-like micelles. Copyright 1997 Academic Press. Copyright 1997Academic Press
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PMID:Additive Effects on the Microstructure Evolution in Hexadecyltrimethylammonium Bromide Solution and Its Rheological Properties 936 90

The present study had investigated the roles of apoptosis and necrosis in the regression of the human fetal hyaloid vasculature. Normal human fetal hyaloid specimens (n = 67) ranging from 10 to 20 weeks' gestation were studied. Specimens were either immunolabeled with anti-von Willebrand factor and major histocompatibility complex class I antibodies or investigated using the terminal-deoxyribonucleotidyl transferase-mediated dUTP-biotin DNA nick-end labeling technique. A fluorescent DNA-binding dye acridine orange/ethidium bromide mixture was also applied to unfixed flat mounts of hyaloid vasculature and some specimens were processed for transmission electron microscopy. Vascular regression including cell loss in the connecting vessels, stretching and thinning of the vasa hyaloidea propria, tunica vasculosa lentis and the pupillary membrane was clearly evident after 13 weeks' gestation. Cresyl violet staining revealed condensed cells and pyknotic bodies throughout the hyaloid system; cell death occurred either in single cells or along small capillary segments associated with vascular regression. Acridine orange/ethidium bromide staining showed DNA condensation at early and late stages of cell death. Similarly, DNA nick-end labeling was positive in endothelial cells, pericytes and vessel and non-vessel associated hyalocytes. The observation of hyalocytes juxtaposed to cytolysed endothelial cells may indicate a role for these cells in vascular regression. Features of apoptosis were more evident during early vascular regression whilst necrosis was increasingly evident at later stages.
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PMID:The human hyaloid system: cell death and vascular regression. 1084 81

The incidence of drug-induced adverse effects is likely to increase as a result of advanced age and exposure of elderly patients to polypharmacy. Therefore, pharmacological therapy of asthma and chronic obstructive pulmonary disease (COPD) in the elderly patient can be potentially hazardous. beta(2)-agonists, administered as therapy for asthma and COPD, have recognised systemic sequelae, such as hypokalaemia and chronotropic effects, which may be life-threatening in susceptible patients. Adverse effects such as hypokalaemia can be aggravated by concomitant treatment with other drugs promoting potassium loss including diuretics, corticosteroids and theophyllines. In addition, relatively minor adverse events associated with the administration of beta(2)-agonists, such as tremor and blood pressure changes, may be of significance to the elderly patient leading to impairment in the quality of life. However, long-term treatment with beta(2)-agonists may reduce the incidence of drug-induced adverse effects as a result of beta-receptor subsensitivity. Oral and inhaled corticosteroids have been used for the treatment of acute asthma and COPD in the elderly patient. Long-term treatment with oral corticosteroids can result in serious systemic adverse effects such as suppressed adrenal function, bone loss, skin thinning and cataract formation. In contrast to beta(2)-agonists, oral corticosteroids can upregulate beta(2)-adrenoceptors and thereby potentiate the systemic sequelae of beta(2)-agonists. Hence, oral corticosteroids should be administered with caution for as short a duration as possible. Inhaled corticosteroids appear to be relatively well tolerated when administered at doses below approximately 1000 microg. However, larger doses of inhaled corticosteroids may affect hypothalamic-pituitary-adrenal function and bone turnover. In the case of inhaled corticosteroids, spacer devices, often used in older patients who cannot operate metered dose inhalers, can potentiate the systemic sequelae of both corticosteroids and beta(2)-agonists. The use of theophyllines in the treatment of COPD or chronic asthma is controversial. Theophyllines have a wide adverse effect profile and are prone to drug-drug interactions. The adverse effects may be mild or life threatening and include nausea and vomiting or sinus and supraventricular tachycardias. Therefore, theophyllines should be prescribed with extreme caution to elderly patients with asthma or COPD. In contrast, inhaled anticholinergic drugs such as ipratropium bromide and oxitropium bromide are generally safe in elderly patients and have useful bronchodilator function. Commonly reported adverse effects are an unpleasant taste and dryness of the mouth. When used as first-line therapy, anticholinergic drugs may optimise the bronchodilator effects of low-dose inhaled beta(2)-agonists in patients with chronic airflow obstruction, and hence obviate the need for higher doses.
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PMID:Asthma medications and their potential adverse effects in the elderly: recommendations for prescribing. 1173 62

We have used small angle neutron scattering, SANS, to investigate the elongational flow induced ordering in surfactant micelles and mesophases. Spatially resolved SANS measurements have been used to determine the distribution of orientational ordering over the flow velocity pattern in an elongational flow cell, and comparison with the effects of shear flow are made. Two different surfactant systems have been studied, the charged wormlike mixed micelles of hexaethylene monododecyl ether, C16E6/hexadecyl trimethylammonium bromide, C16TAB (3% C16E(6)/5 mol% C16TAB), and the Lalpha lamellar phase of C16E6 (50.6 wt% C16E6 at 55 degrees C), and a substantially different response is observed. The orientational distribution of the Lalpha lamellar phase of C16E6 reflects the flow velocity pattern distribution within the cell, whereas for the wormlike mixed micelles of C16E6/C16TAB this is not the case, and this is associated with the shear thinning behavior of that system.
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PMID:Elongational flow induced ordering in surfactant micelles and mesophases. 1647 44

We used molecular dynamics (MD) simulations to investigate the structures and properties of Newton black films (NBF) for several surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (C16TAB), and surfactin using film thicknesses up to 10 nm. By calculating the interface formation energy for various packing conditions on the surface pressure-area isotherm, we found that the most probable surface concentration is approximately 42 A(2)/molecule for SDS and C16TAB and approximately 170 A(2)/molecule for surfactin. We then used this most probable concentration of each surfactant to simulate NBF with various film thicknesses. From analyzing the disjoining pressure-film thickness isotherms with the density profiles and the solvation coordination number, we found that the increase of the disjoining pressure during the film thinning was coupled with the change in inner structure of the NBF (i.e., density profile and the solvation of ionic entities). In the range of film thicknesses less than approximately 30 A, the disjoining pressures for the SDS and C16TAB were found to be larger than that of the surfactin. We predicted the Gibbs elasticity (175 dyn/cm for surfactin; 109 dyn/cm for C16TAB; 38 dyn/cm for SDS) required to assess the stability of NBF against surface concentration fluctuations, and the shear modulus (6.5 GPa for the surfactin; 6.1 GPa for the C16TAB; 3.5 GPa for the SDS) and the yield stress (approximately 0.8 GPa for surfactin; approximately 0.8 GPa for C16TAB; approximately 0.4 GPa for the SDS) to assess the mechanical stability against the externally imposed mechanical perturbation.
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PMID:Structures and properties of Newton black films characterized using molecular dynamics simulations. 1661 Aug 99

Unilamellar vesicles are observed to form in aqueous solutions of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), when 5-methyl salicylic acid (5mS) is added at slightly larger than equimolar concentrations. When these vesicles are heated above a critical temperature, they transform into long, flexible wormlike micelles. In this process, the solutions switch from low-viscosity, Newtonian fluids to viscoelastic, shear-thinning fluids having much larger zero-shear viscosities (e.g., 1000-fold higher). The onset temperature for this transition increases with the concentration of 5mS at a fixed CTAB content. Small-angle neutron scattering (SANS) measurements show that the phase transition from vesicles to micelles is a continuous one, with the vesicles and micelles coexisting over a narrow range of temperatures. The tunable vesicle-to-micelle transition and the concomitant viscosity increase upon heating may have utility in a range of areas, including microfluidics, controlled release, and tertiary oil recovery.
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PMID:Self-assembly of surfactant vesicles that transform into viscoelastic wormlike micelles upon heating. 1670 68


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