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At least 271 records · Page 15Linked to original sources
PubMed1985

Increase of virus yields and releases of Borna disease virus from persistently infected cells.

Borna disease virus grows to low titres in persistently infected cells with an infectious particle to cell ratio of 0.01 to 0.05. Inclusion of n-butyrate in the growth medium enhances infectivity yields up to 1 log. This effect is time and concentration dependent. In hypertonic medium with an excess of NaCl, KCl or Na2SO4 up to 50% of the total infectious virus yield is released from the cells. Released supernatant virus (buoyant density in sucrose rho = 1.22 g/cm3) is more heat stabile than cell-bound virus (rho = 1.18 g/cm3). The access to cell-free (released) virus opens new possibilities for the characterization of this neurotropic agent.

Animals↗
PubMed1990

Modulation of pulmonary eicosanoid metabolism following exposure to sulfuric acid.

Eicosanoids (arachidonic acid metabolites) are potent biological mediators. Modulation of their metabolism by air pollutants may be a possible factor in the pathogenesis of environmentally related lung disease. Sulfuric acid (H2SO4) aerosols are components of ambient air in many areas. Rabbits were exposed to H2SO4 (0.3 microns) at 250, 500, or 1000 micrograms/m3 for 1 hr/day for 5 days. They were then euthanized, the lungs lavaged, and eicosanoid analyses performed by radioimmunoassay of acellular lavage fluid. An exposure-concentration-dependent decrease in levels of prostaglandins E2 and F2 alpha and thromboxane B2 was found; no change in leukotriene B4 was observed. Tracheal explants exposed to acidic environments in vitro also showed reduced production of PGE2, PGF2 alpha, and TxB2. Incubation with sodium sulfate (Na2SO4) showed no effect of the sulfate ion (SO4(2-)). This study, the first to examine eicosanoid production after in vivo exposure to pure H2SO4 droplets, indicates that such exposure can modulate arachidonic acid metabolism, and that this is likely due to the deposition of hydrogen ion (H+) on target tissue.

Aerosols↗
PubMed1986

Synergistic interaction of ozone and respirable aerosols on rat lungs. I. Importance of aerosol acidity.

A synergistic interaction, as defined by biochemical and morphological criteria, between ozone (or NO2) and respirable aerosols of ammonium sulfate or sulfuric acid has been described previously. Experiments in the present paper show that it is the acidity, not the sulfate content, of the aerosol that is responsible for such synergy; neutral aerosols of Na2SO4 or NaCl do not elicit synergistic effects when combined with ozone. Aerosol size (and, therefore, site of deposition in the lung) is also an important determinant of synergy with ozone; 0.5 micron mass median aerodynamic diameter (MMAD) aerosols are effective whereas 0.02 micron MMAD aerosols are not. The synergistic interaction between ozone and acidic aerosols could be demonstrated by biochemical and toxicological criteria in addition to those we have previously reported, for example increases in whole lung protein content and free (acid-soluble) proline content of lungs. A synergistic interaction has been demonstrated at concentrations of 0.64 ppm (1.3 mg/m3) of ozone and 1 mg/m3 of acid aerosol in this study. We conclude that acidity of an aerosol determines whether or not it interacts synergistically with ozone, and that an aerosol size that impacts maximally upon the alveolar duct region of the lung is most active with ozone.

Aerosols↗
PubMed1987

Changes in cell membrane fluidity affect the sodium transport across frog skin and its sensitivity to amiloride.

1. 1-5 mM n-hexanol added to the outer (mucosal) medium of isolated skin of the frog Rana temporaria increases the short circuit current (Isc) across it. 2. This effect shows a saturable dependency on the outer sodium concentration, also when NaCl is replaced by Na2SO4. 3. n-Hexanol at a concentration of 1 mM, and cold acclimation of the frogs, which increases the fluidity of epidermal cell membranes, do not affect the sensitivity of Isc to the inhibiting effect of amiloride. 4. n-Hexanol at a concentration (5 mM) which causes a fluidization of cell membrane preparations from isolated frog epidermis also increases the sensitivity of Isc to amiloride. 5. The effects of low concentrations of n-hexanol and of cold acclimation probably depend on an increase of the permeability of apical membranes of epidermal cells to sodium caused by membrane fluidization. At higher concentrations of n-hexanol, a further disordering of the membrane structure occurs with a better access of amiloride to its action sites.

Amiloride↗
PubMed1978

Thermal membrane potential across charged membranes in 2-1 and 1-2 electrolyte solutions.

Measurements of thermal membrane potential across cation exchange membranes in MgCl2, CaCl2 and BaCl2 solutions and across anion exchange membranes in K2SO4, Na2SO4 and K2CO3 solutions were carried out. The magnitude of the thermal membrane potential for divalent counterions is lower than that for monovalent counterions. If the transport number of counterions in the membrane phase is unity, the slopes of the temperature coefficient of thermal membrane potential against logarithmic activities of counterion in the external solution are predicted to be--R/2F for 2-1 electrolytes with cation exchange membranes and R/2F for 1-2 electrolytes with anion exchange membranes, respectively.

Electrolytes↗
PubMed1981

Effect of pH and ammonium ions on mutagenic activity in cooked beef.

Controversy surrounding the extraction procedure commonly used for isolating and concentrating mutagens from foods has resulted in a need for the re-examination of the reported mutagenicity in fried hamburgers. Using a procedure in which Na2SO4 and NaOH are substituted for (NH4)2SO4 and NH4OH respectively, mutagenic activity in extracts of hamburgers fried for 5 min appeared to be unchanged. However, when organic extractions are performed at pH conditions more moderate than those generally employed to isolate mutagens from foods, a 30-50% decrease in mutagenicity is observed.

Ammonia↗
PubMed1981

Isolation and characterization of an adenylyl-protein complex formed during the incubation of membranes from Dictyostelium discoideum with ATP.

When tritiated ATP is incubated with a membrane-enriched fraction prepared from the eukaryotic microorganism Dictyostelium discoideum significant levels of radioactivity can be precipitated with cold, 10% trichloroacetic acid. Reaction product was formed from ATP and dATP but not from GTP, CTP and UTP. Other studies showed that the maximum amount of the acid-insoluble product was formed about 1 min after the addition of the membranes and that, with further incubation, this reaction product was degraded. The rate of degradation of the reaction product was greatly reduced when the temperature was reduced to 4 degrees C, and when either NaF, Na2SO4 or dithiothreitol was added to the reaction mixture. These additions or conditions had no effect on the product-formation reaction. The rate of degradation was also reduced following the addition of adenosine to the reaction and this result did not occur following the addition of ADP, AMP or cyclic AMP. The acid-insoluble reaction product could be solubilized with SDS and analysis by gel-filtration chromatography on Sephadex G-75 revealed that the radioactivity was associated with a macromolecule that was not sensitive to RNAase or DNAase but was degraded by pronase. The nucleotide-protein complex was stable at room temperature but radioactivity was released in hot acid, which, after analysis by thin-layer chromatography, was found to co-migrate with authentic AMP, suggesting the formation of an adenylyl-protein complex as the reaction intermediate. The complex bond was stable at neutral and alkaline pH, suggesting a phosphoamide linkage between the protein and the adenylyl moiety.

Adenine Nucleotides↗
PubMed1987

Affinity chromatography and some properties of the angiotensin-converting enzyme from human heart.

Human heart angiotensin-converting enzyme has been purified by affinity chromatography on immobilized N-[1(S)-carboxy-5-aminopentyl]-Gly-Gly. The isolation procedure permitted a 1650-fold-purified enzyme to be obtained. The specific activity of angiotensin-converting enzyme was 38 units per mg protein. The molecular weight of enzyme determined by polyacrylamide gel electrophoresis in denaturing conditions was 150,000. The isoelectric point (5.3) of the enzyme was determined by chromatofocusing. The Km values of the enzyme for Bz-Gly-His-Leu and angiotensin I are 1.2 mM and 10 microM, respectively. Substrate inhibition of heart angiotensin-converting enzyme with a K's of 14 mM has been shown. The human heart enzyme is inhibited by SQ 20881 (IC50 = 40 nM). It was shown that NaCl, CaCl2 as well as Na2SO4 in the absence of Cl- are activators of the heart angiotensin-converting enzyme, whereas CH3COONa and NaNO3 have no effect on a catalytic activity of the enzyme.

Angiotensin I↗
PubMed1982

Purification and some regulatory properties of glycogen synthase I from rabbit renal medulla.

1. Glycogen synthase I (activity ratio approximately equal to 1) was purified over 10,000-fold from rabbit renal medulla. 2. The purified synthase was stimulated about 1.5-fold by glucose-6-P and other divalent anions when assayed at pH 7.7 and near saturating UDPGlc. When assayed at physiological UDPGlc (75-100 microM), the enzyme was stimulated about 5-fold by glucose-6-P. 3. At pH 7.7 the activation by either Na2SO4 or glucose-6-P was due to an increase in V and a decrease in S0.5 for UDPGlc. At pH. 6.9, activation was due to a decrease in S0.5. 4. At low UDPGlc, synthase activity was inhibited by adenine nucleotides and the inhibition was partially relieved by glucose-6-P, UDP inhibited in a competitive manner with respect to UDPGlc. 5. These results suggest that the activity of renal medullary synthase I may be regulated by cellular metabolites.

Animals↗
PubMed1990

Yolk-sac transmission and post-hatching ontogeny of serum immunoglobulins in the duck (Anas platyrhynchos).

1. To investigate the immunoglobulin (Ig) class which is active in yolk-sac transmission of maternal antibodies in ducks, sera from laying ducks, yolks from their eggs, and sera from ducklings 0-87 days of age were examined by immunoelectrophoresis (IE), and Na2SO4-precipitated Igs from these sera and yolks were run in polyacrylamide gel electrophoresis (PAGE) under reducing conditions. 2. In yolk, 7.8S IgG was greatly enriched compared to 5.7S IgG and IgM, and was the only Ig to reach the sera of newly hatched ducklings. 3. The levels of maternally derived 7.8S IgG in duckling sera decreased after 5 days of age, reaching minimum levels at about 14 days of age. 4. Increases in the serum levels of 7.8S IgG, 5.7S IgG and IgM occurred after 20 days of age, reflecting de novo synthesis by the duckling, and the adult serum profile was achieved by 71 days of age. 5. The involvement of 7.8S rather than 5.7S IgG in yolk-sac transmission was probably determined by the additional heavy chain components of this molecule.

Animals↗
PubMed1991

Proteoglycan synthesis in human skin and burn scar explant cultures.

The synthesis of proteoglycans (PG) by normal human skin, and normal and hypertrophic scars were compared using tissue explants in culture. Newly synthesized PG were labelled with [35S]Na2SO4. Significant differences were found in the proportion of [35S]-radio-labelled incorporation of PG in the tissue and accumulation of [35S]PG in culture medium in the different tissues. The rate of PG biosynthesis in all three tissue types occurred in two phases. There was an initial phase of PG synthesis occurring at 0-3 h and a later phase that occurred at 3-18 h [35S]-labelled PG were isolated and characterized by Sepharose CL-6B chromatography and cellulose acetate electrophoresis. The results showed that the hypertrophic scar tissue and its culture medium contained higher proportions of dermatan sulphate (DS), chondroitin sulphate (CS) and DS' PG than the normal skin fractions. These results suggest that abnormal scarring is related to a change in the level of PG synthesis during the burn injury repair process.

Burns↗
PubMed1993

Effect of ebrotidine on the synthesis and secretion of gastric sulfomucin.

1. The effect of a new antiulcer agent, ebrotidine, on the synthesis and secretion of sulfomucin in gastric mucosa was investigated. Rat gastric mucosal segments were incubated in DMEM containing [3H]proline, [3H]glucosamine and [35S]Na2SO4 as markers for mucin synthesis, glycosylation and sulfation, in the presence of 0-150 microM ebrotidine. 2. The drug, while showing no discernible effect on the apomucin synthesis, evoked a dose-dependent increase in mucin glycosylation and sulfation, which at 100 microM ebrotidine, attained its maximum of 2.4 and 2.7-fold stimulation, respectively. 3. The analysis of mucin secretory responses revealed that ebrotidine caused a concentration-dependent enhancement in sulfomucin secretion which attained its maximum increase of 3.3-fold at 100-120 microM ebrotidine. Furthermore, the sulfomucin elaborated in the presence of ebrotidine exhibited a higher content of a large molecular-weight mucus glycoprotein form, the assembly of which is intimately associated with the sulfation event. 4. The results suggest that the ability of ebrotidine to enhance gastric sulfomucin synthesis and secretion may play an important role in the gastroprotective mechanism of action of this agent.

Animals↗
PubMed1982

Electrical impedance of isolated retina and its changes during spreading depression.

The electrical impedance of isolated chick and toad retinas were measured in the absence of, and during, spreading depression, using sinusoidal measuring currents ranging from 10 to 50,000 Hz. Data obtained in the absence of the reaction indicate an electric heterogeneity of the tissue and suggest that at least two groups of cells are responsible for the observed frequency distribution. Spreading depression is accompanied by impedance changes that depend on the frequency of the measuring current and composition of the Ringer's solution. In chick retinas immersed in standard solution, impedance magnitude (Z) as well as phase angle (0) change in phase, displaying an initial increase followed by a longer decrease; in the toad, these changes depend on the measuring frequency: at 10 Hz they are similar to the ones observed in chick retinas, whereas at intermediate and high frequencies they are out of phase. In low Cl- + sucrose Ringer's solution a decrease of impedance is observed in both chick and toad retinas. In low Cl- + Na2SO4 + sucrose Ringer's solution a decrease of impedance also predominates but the Z and 0 curves are biphasic and complex, having time courses which are frequency-dependent. In addition, these changes are different in chick and toad preparations. The experiments show that the impedance changes during the retinal reaction might be related both to extracellular as well as cellular currents. The extracellular current changes could be due to decrease of ionic content and volume of extracellular space, the latter variations being drastically reduced when retinas are immersed in low Cl- solutions. The results also suggest changes of current flow through cellular components which are frequency-dependent: at low frequencies the preferential path being probably through neuronal, and at high frequencies, through glial cells.

Animals↗
PubMed1996

Ucon-benzoyl dextran aqueous two-phase systems: protein purification with phase component recycling.

Benzoyl dextran with a degree of substitution of 0.18 was synthesized by reacting dextran T500 with benzoyl chloride. A new type of aqueous two-phase system composed of benzoyl dextran as bottom phase polymer and the random copolymer of ethylene oxide and propylene oxide (Ucon 50-HB-5100) as top phase polymer has been formed. The phase diagram for the system Ucon 50-HB-5100-benzoyl dextran with a degree of substitution of 0.18 was determined at room temperature. This two-phase system has been used to purify 3-phosphoglycerate kinase from baker's yeast. The top-phase polymer (Ucon) can be separated from target enzyme by increasing the temperature. The bottom-phase polymer (benzoyl dextran) could be recovered by addition of salt. Yeast homogenate was partitioned in a primary Ucon 50-HB-5100-benzoyl dextran aqueous two-phase system. After phase separation the top phase was removed and temperature-induced phase separation was used for formation of a water phase and a Ucon-rich phase. The benzoyl dextran-enriched bottom phase from the primary system was diluted, and the polymer was separated from water by addition of Na2SO4.

Dextrans↗
PubMed1996

Determination of mivacurium in plasma by high-performance liquid chromatography.

An assay has been developed and validated for the routine monitoring of mivacurium in plasma. It consists of liquid-liquid extraction with dichloromethane and high-performance liquid chromatography with fluorometric detection (excitation and emission wavelengths 220 nm and 320 nm, respectively). A Spherisorb C, 5 microns column and a mobile phase containing acetonitrile, KH2PO4 and methanol are used. At a flow-rate of 1 ml/min, a concentration gradient is applied. The detection limit is approximately 1 ng/ml in plasma. For the separation of steroisomeres, the Spherisorb SCX 10 microns column and acetonitrile-Na2SO4 as a mobile phase can be used. The assay shows good linearity over the range 1-1000 ng/ml. The accuracy and precision allows the utilisation in clinical pharmacokinetic studies.

Chromatography, High Pressure Liquid↗
PubMed1985

Analysis of neomycins A, B and C by high-performance liquid chromatography with post-column reaction detection.

The analysis of the antibiotics neomycins A, B and C was investigated. The separation of the components was studied using reversed-phase and reversed-phase ion-pair chromatography. The optimum separation was obtained utilizing a Lichrosorb RP-2 column with a mobile phase consisting of 75 mg/l sodium dodecyl sulphate, 0.5M Na2SO4 and 0.015 M sodium acetate buffer at pH 7.0. Using this mobile phase, baseline separation was obtained for all three compounds in approximately 20 min. Detection was via post-column derivatization of the analytes with ortho-phthalaldehyde in the presence of mercaptoethanol to form fluorescent iso-indole products. This system is applied to the analysis of a number of formulated products containing neomycin.

Journal Article↗
PubMed1987

Quality control and the preparative purification of low antibody concentrations for radiolabelling using bifunctional chelates.

The conjugation of antibodies (Ab) with DTPA in the presence of contaminating low molecular weight proteins is inefficient. The selective precipitation of Ab with 18% Na2SO4 as a preparative purification method for small aliquots of low Ab concentrations is successful in eliminating all contaminants as monitored by high performance liquid chromatography at 214 nm and in allowing IgG recoveries greater than 94%. Subsequently, this allows efficient conjugation and radiolabelling of Ab.

Antibodies↗
PubMed1989

Characteristics of leukocyte and plasma methylumbelliferyl-alpha-L-iduronide iduronidase.

Some characteristics of the human leukocyte and plasma alpha-L-iduronidase are described. The enzyme from both sources is sufficiently stable and linear in time to allow accurate determinations. The leukocyte and plasma enzyme have a low acid pH optimum at 3.5 and 4, respectively, which is in agreement with the lysosomal origin of the enzyme in the cell. Both enzymes are inhibited by phenyl-alpha-L-iduronide, heparin, and heparitin sulfate although other mucopolysaccharides also inhibit the leukocyte enzyme. When kept frozen at -20 degrees C, the leukocyte as well as the enzyme in acidified plasma are very stable. We studied the plasma enzyme in more detail. If the plasma is acidified, iduronidase is very stable between 0 and 37 degrees C. CuCl2 and Na2SO4 were very potent inhibitors at concentrations of 10 and 100 mM, respectively. The determination of iduronidase in leukocyte homogenates of patients suspected of Hurler disease together with plasma activities is useful for confirming or corroborating the diagnosis of genetic iduronidase deficiency. Further investigation is needed to determine if the plasma enzyme test would be useful in the biochemical diagnosis of Scheie disease and the Hurler-Scheie compound, two diseases which are also caused by a deficiency of alpha-L-iduronidase.

Fluorescent Dyes↗