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We have investigated the kinetic properties of the human red blood cell Na+/H+ exchanger to provide a tool to study the role of genetic, hormonal and environmental factors in its expression as well as its functional properties in several clinical conditions. The present study reports its stoichiometry and the kinetic effects of internal H+ (Hi) and external Na+ (Nao) in red blood cells of normal subjects. Red blood cells with different cell Na+ (Nai) and pH (pHi) were prepared by nystatin and DIDS treatment of acid-loaded cells. Unidirectional and net Na+ influx were measured by varying pHi (from 5.7 to 7.4), external pH (pHo), Nai and Nao and by incubating the cells in media containing ouabain, bumetanide and methazolamide. Net Na+ influx (Nai less than 2.0 mmol/liter cell, Nao = 150 mM) increased sigmoidally (Hill coefficient 2.5) when pHi fell below 7.0 and the external pHo was 8.0, but increased linearly at pHo 6.0. The net Na+ influx driven by an outward H+ gradient was estimated from the difference of Na+ influx at the two pHo levels (pHo 8 and pHo 6). The H+-driven Na+ influx reached saturation between pHi 5.9 and 6.1. The Vmax had a wide interindividual variation (6 to 63 mmol/liter cell.hr, 31.0 +/- 3, mean +/- SEM, n = 20). The Km for Hi to activate H+-driven Na+ influx was 347 +/- 30 nM (n = 7). Amiloride (1 mM) or DMA (20 microM) partially (59 +/- 10%) inhibited red cell Na+/H+ exchange. The stoichiometric ratio between H+-driven Na+ influx and Na+-driven H+ efflux was 1:1. The dependence of Na+ influx from Nao was studied at pHi 6.0, and Nai lower than 2 mmol/liter cell at pHo 6.0 and 8.0. The mean Km for Nao of the H+-gradient-driven Na+ influx was 55 +/- 7 mM. An increase in Nai from 2 to 20 mmol/liter cell did not change significantly H+-driven net Na+ influx as estimated from the difference between unidirectional 22Na influx and efflux. Na+/Na+ exchange was negligible in acid-loaded, DIDS-treated cells. Na+ and H+ efflux from acid-loaded cells were inhibited by amiloride analogs in the absence of external Na+ indicating that they may represent nonspecific effects of these compounds and/or uncoupled transport modes of the Na+/H+ exchanger. It is concluded that human red cell Na+/H+ exchange performs 1:1 exchange of external Na+ for internal protons, which is partially amiloride sensitive.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Kinetics and stoichiometry of the human red cell Na+/H+ exchanger. 254 Dec 50

Nitrosodimethylamine (NDMA) is a potent carcinogen in a wide variety of animal species. In experimental animals, dimethylamine and nitrite, precursors of NDMA, are found in gastric fluid where the acidic conditions are suitable for formation of nitrosamines. In this study we measured the concentrations of mono-, di- and trimethylamine (MMA, DMA and TMA) in gastric fluid from humans, rats, dogs and ferrets, as well as in saliva, blood and urine from humans. Human gastric fluid contained 3.7 +/- 0.4 (SEM) nmol/ml MMA, 12.6 +/- 1.4 nmol/ml DMA and 2.0 +/- 0.4 nmol/ml TMA. MMA, DMA and TMA concentrations in human gastric fluid were similar to those present in human saliva and blood, but were much lower than those present in human urine. The concentrations of these amines in human gastric fluid were lower than those measured in gastric fluid from experimental animals. When we added sodium nitrite to human gastric fluid, NDMA was formed. We have shown that DMA is normally present in human gastric fluid, and that it can be nitrosated to form NDMA.
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PMID:Mono-, di- and trimethylamine in human gastric fluid: potential substrates for nitrosodimethylamine formation. 333 43

Chitins of various origins in DMA-LiCl solution have been reacted with excess 1,6-diisocyanatohexane (three or twelve equivalents per repeating unit) for 4-20 h. The resulting solutions were exposed to water vapor for 2 days and flexible and opaque materials were produced, which upon drying yielded powders whose main characteristics were insolubility in aqueous and organic solvents, remarkable crystallinity, typical infrared spectrum, high N/C ratio (0.287), and a high degree of substitution (0.29). Under the SEM structural features reminiscent of chitin were absent but no thermoplastic behavior was found by differential scanning calorimetry. Chitosan was similarly treated under heterogeneous conditions in anhydrous pyridine, and yielded reaction products with a lower degree of substitution (0.17). With partially hydrolysed chitosan, highly crystalline products were obtained.
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PMID:Chitin-based poly(urea-urethane)s. 787 7

Chronic hypoxia produces pulmonary hypertension, in part because of hypertrophy and hyperplasia of pulmonary artery smooth muscle cells (PA SMC). Platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) have been shown to stimulate SMC proliferation and may be involved in these vascular changes. Both factors cause a rise in intracellular pH (pHi) in systemic vascular SMC through stimulation of the Na+/H+ exchanger, an event that has been thought to be permissive, allowing cell proliferation in response to the growth factor. The present studies examined the possibility that the activation of Na+/H+ exchange is involved in the PA SMC mitogenic response to these growth factors. Na+/H+ exchange activity was assessed by monitoring pHi in cultured cells using the pH-sensitive dye, 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). PDGF (60 ng/ml) exposure led to a marked activation of Na+/H+ exchange, evidenced by a rise in pHi (mean +/- SEM) of 0.20 +/- 0.03 pH units (n = 5, P < 0.05). EGF (60 ng/ml) exposure produced a rise in pHi of 0.27 +/- 0.03 pH units (n = 5, P < 0.05). Dimethyl amiloride (DMA, 50 microM), a competitive inhibitor of Na+/H+ exchange, blocked the pH response to PDGF and EGF. PA SMC showed a proliferative response when exposed to PDGF and EGF which was attenuated by 50 microM DMA (n = 6). Thus, activation of the Na+/H+ exchanger may be important in pulmonary cell signaling in response to growth factors as it has been found to be in systemic vessels.
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PMID:The role of Na+/H+ exchange and growth factors in pulmonary artery smooth muscle cell proliferation. 863 Feb 63

The formation of monomethylarsonous acid (MMA(III)) by tissue homogenates of brain, bladder, spleen, liver, lung, heart, skin, kidney, or testis of male Golden Syrian hamsters was assessed using [(14)C]monomethylarsonic acid (MMA(V)) as the substrate for MMA(V) reductase. The mean +/- SEM of MMA(V) reductase specific activities (nanomoles of MMA(III) per milligram of protein per hour) were as follows: brain, 91.4 +/- 3.0; bladder, 61.8 +/- 3.7; spleen, 30.2 +/- 5.4; liver, 29.8 +/- 1.4; lung, 21.5 +/- 0.8; heart, 19.4 +/- 1.5; skin, 14.7 +/- 1.6; kidney, 10.6 +/- 0.4; and testis, 9.8 +/- 0.6. The concentrations of MMA(III) in male Golden Syrian hamster livers were determined 15 h after administration of a single intraperitoneal dose of 145 microCi of [(73)As]arsenate (2 mg of As/kg of body weight). Trivalent arsenic species (arsenite, MMA(III), and dimethylarsinous acid, DMA(III)) were extracted from liver homogenates using carbon tetrachloride (CCl(4)) and 20 mM diethylammonium salt of diethyldithiocarbamic acid (DDDC). Pentavalent arsenicals (arsenate, MMA(V), and dimethylarsinic acid, DMA(V)) remained in the aqueous phase. The organic and the aqueous phases then were analyzed by HPLC. Metabolites of inorganic arsenate present in hamster liver after 15 h were observed in the following concentrations (nanograms per gram of liver +/- SEM): MMA(III), 38.5 +/- 2.9; DMA(III), 49.9 +/- 10.2; arsenite, 35.5 +/- 3.0; arsenate, 118.2 +/- 8.7; MMA(V), 31.4 +/- 2.8; and DMA(V), 83.5 +/- 6.7. This first-time identification of MMA(III) and DMA(III) in liver after arsenate exposure indicates that the significance of arsenic species in mammalian tissue needs to be re-examined and re-evaluated with respect to their role in the toxicity and carcinogenicity of inorganic arsenic.
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PMID:Monomethylarsonic acid reductase and monomethylarsonous acid in hamster tissue. 1108 41

PURPOSE:The scope of endovascular surgical techniques has expanded to include the treatment of diseases considered at one time to be amenable only to surgical treatment. The development of the biodegradable template follows as an extension of current permanent stent technology. The goal of our project is to develop and test chitosan as an absorbable template for the vascular system.Ultrapure chitosan, heparin sodium salt and lysozyme, and contrast agents MD-76R and Oxilan-350 were used to give radioopaque quality. Prototype chitosan vascular templates were obtained by a dip coating method in which alternate layers of chitosan were coagulated with nonsolvents or heparin. The amount of loaded and released heparin was determined using Azure II colorimetric assay. In vitro enzymatic degradation of templates was evaluated using lysozyme solutions in phosphate buffered saline. Mechanical properties were analyzed using the Dynamic Mechanical Analyzer, DMA-7 (Perkin Elmer, Foster City, Calif.). The microstructure of freeze-dried templates was investigated by field emission scanning electron microscopy (FE SEM) using an LEO 982 electron microscope (Zeiss, Thornwood, NY).In vivo deployment of the templates was undertaken in 10 full-sized pigs (Sus scrofa). After open expose and control of the iliac artery, a closed balloon catheter technique was used to advance and place the balloon catheter and template. The balloon was then expanded, deploying a Palmaz stent with a chitosan template anchored distally. Patency and deployment of the stent-template complex was confirmed by an arteriogram. The animals were sacrificed at 1, 2, 3, 4, and 5 weeks poststent placement, and arterial sections were taken for microscopic analysis. The amount of chitosan remaining was estimated to determine an in vivo rate of absorption.On hematoxilyn and eosin staining of the section arterial samples, a marked inflammatory response was noted and progressed with duration of in vivo contact. A giant cell foreign body reaction coupled with intense intimal hyperplasia and organized thrombus was also noted and progressed with duration of time in vivo. Also noted was the degradation of the template material with only small remnants of material noted within the giant cell by week 4. Clinically, none of the pigs developed limb ischemia or evidence of thromboembolic events.In this in vivo study, the chitosan template proved to be biodegradable but elicited an intense thrombotic and foreign body reaction despite heparin bonding. Further investigation is ongoing as to decreasing the thrombogenic and antigenic qualities of the template materials by either alteration of the base material or addition of bioactive side chains.
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PMID:Bioabsorption qualities of chitosan-absorbable vascular templates(1). 1122 42

Composites based on phenolic matrices and unmodified and chemically modified sugar cane bagasse and curaua fibers were prepared. The fibers were oxidized by chlorine dioxide, mainly phenolic syringyl and guaiacyl units of the lignin polymer, followed by grafting furfuryl alcohol (FA), which is a chemical obtained from a renewable source. The fibers were widely characterized by chemical composition analysis, crystallinity, UV-vis diffuse reflectance spectroscopy, SEM, DSC, TG, tensile strength, and 13C CP-MAS NMR. The composites were analyzed by SEM, impact strength, and DMA. The SEM images and DMA results showed that the oxidation of sugar cane bagasse fibers followed by reaction with FA favored the fiber/matrix interaction at the interface. The same chemical modification was less effective for curaua fibers, probably due to its lower lignin content, since the reaction considered touches mainly the lignin moiety. The tensile strength results obtained showed that the fibers were partially degraded by the chemical treatment, decreasing then the impact strength of the composites reinforced with them. In the continuity of the present project, efforts has been addressed to the optimization of fiber surface modification, looking for reagents preferably obtained from renewable resources and for chemical modifications that intensify the fiber/matrix interaction without loss of mechanical properties.
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PMID:Thermoset phenolic matrices reinforced with unmodified and surface-grafted furfuryl alcohol sugar cane bagasse and curaua fibers: properties of fibers and composites. 1615 84

For short-term cardiovascular application, segmented polyurethanes (SPUs) based on 4,4-methylenebis(cyclohexyl isocyanate) (HMDI), polytetramethylenglycol (PTMG) and 1,4-butanediol (BD) were synthesized and characterized by spectroscopy (FT-IR, (1)H-NMR) and thermal (TGA, DMA, DSC) and mechanical techniques. The segmented nature of the SPUs was not easily established by spectroscopic means; however, TGA allowed the quantification of the rigid segments content by the significant mass loss between 348 and 356 degrees C. The alpha transition was detected by DMA and related to the T(g) of the soft segments at -50 degrees C, while DSC showed the presence of an endothermic transition above 80 degrees C attributed to the melting of rigid segments. Two types of composites were prepared using the synthesized SPUs and Lycra (either T162B or T162C). The first one consisted of a two layers casting laminated while the second one was a classic unidirectional fibre-reinforced material. Laminate composites prepared with SPU containing 23.9% and 33.9% of rigid segments and Lycra T162C exhibited a higher tensile modulus but lower tensile strength than composites prepared with Tecoflex SG-80A (39.7% of rigid segments). The energy of adhesion between layers on these composites ranged from 475 to 2150 J. Fibre-reinforced SPUs exhibited higher moduli than the two layer laminated composites with increasing amounts of rigid segments in the matrix and by increasing Lycra T162C content (up to 10%). This behaviour was explained by SEM, which showed a good fibre-matrix bonding.
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PMID:Synthesis of HMDI-based segmented polyurethanes and their use in the manufacture of elastomeric composites for cardiovascular applications. 1755 Jun 59

Polyacrylonitrile (PAN) fiber was modified with hydroxylamine hydrochloride to introduce amidoxime groups onto the fiber surface. These amidoxime groups were used to react with Fe (III) ions to prepare Fe (III)-amidoximated PAN fiber complex, which was characterized using SEM, XRD, FTIR, XPS, DMA, and DRS respectively. Then the photocatalytic activity of Fe-AO-PAN was evaluated in the degradation of a typical azo dye, C. I. Reactive Red 195 in the presence of H(2)O(2) under visible light irradiation. Moreover, the effect of the Fe content of Fe-AO-PAN on dye degradation was also investigated. The results indicated that Fe (III) ions can crosslink between the modified PAN fiber chains by the coordination of Fe (III) ions with the amino nitrogen atoms and hydroxyl oxygen atoms of the amidoximation groups to form Fe (III)-amidoximated PAN fiber complex, and the Fe content of which is mainly determined by Fe (III) ions and amidoximation groups. Fe (III)-amidoximated PAN fiber complex is found to be activated in the visible light region. Moreover, Fe (III)-amidoximated PAN fiber complex shows the catalytic activity for dye degradation by H(2)O(2) at pH=6.0 in the dark, and can be significantly enhanced by increasing light irradiation and Fe content, therefore, it can be used as a new heterogeneous Fenton photocatalyst for the effective decomposition of the dye in water. In addition, ESR spectra confirm that Fe (III)-amidoximated PAN fiber complex can generate more OH radicals from H(2)O(2) under visible light irradiation, leading to dye degradation. A possible mechanism of photocatalysis is proposed.
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PMID:Preparation and photocatalytic performance of Fe (III)-amidoximated PAN fiber complex for oxidative degradation of azo dye under visible light irradiation. 2017 Sep 39

Thermally activated shape memory polyurethane foams are promising materials for minimally invasive surgical procedures. Understanding their physical and chemical properties, in vitro response and effects of sterilization is mandatory when evaluating their potential as biomaterials. In this work, we report on the characterization of two Cold Hibernated Elastic Memory (CHEM) foams before and after two novel low-temperature sterilization techniques (plasma and ozone). Foams have different transition temperatures (T(trans)), as determined by Tandelta peaks in DMA tests, that depend on their chemical composition: both foams possess excellent shape recovery ability (Recovery Rate up to 99%) in conventional shape recovery tests. Plasma sterilization (Sterrad sterilization system) resulted in a slight increase of open porosity, but no effects on bulk chemical and thermo-mechanical properties were observed. Ozone sterilization had a stronger effect on foams morphology, both in terms of an evident rupture of pore walls and surface oxidation. These modifications affected both thermomechanical and shape recovery behavior. Furthermore, plasma sterilized foams cytocompatibility was investigated with L929 fibroblast cell line in vitro, showing a good adhesion and proliferation, as confirmed by SEM observation and Alamar blue assay. The obtained results contribute to define the role of shape memory foams as biomaterials and open novel questions on the role of sterilization technique effects on cellular solids.
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PMID:Chemico-physical modifications induced by plasma and ozone sterilizations on shape memory polyurethane foams. 2040 8


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