UNIPROT:P50583 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
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The physicochemical properties of nuclear and cytosolic glucocorticoid-binding components from corticoid-sensitive (CS) and corticoid-resistant (CR) mouse lymphoma P1798 cells have been compared. Nuclei or cytosol fractions were prepared from lymphocytes that had been labeled at 37 or 4 degrees, respectively, with 30 nM [3H]triamcinolone acetonide ([3H]TA). [3H]TA was extracted with 0.6 M KCl, 10 mM spermidine, or 4.5 mM MgCl2 from CS nuclei and with 0.6 M KCl or 10 mM spermidine from CR nuclei. As reported previously, nuclear-associated [3H]TA in CR cells was resistant to extraction with mM concentrations of MgCl2. Loss of bound steroid during extraction with 0.6 M KCl was minimized by including the chymotrypsin inhibitor, carbobenzoxy-L-phenylalanine, in the extraction buffer. The inhibitor was not required during extraction with spermidine or MgCl2. Nuclear and cytosolic extracts were examined by analytical agarose gel filtration and glycerol density gradient centrifugation under high salt (0.6 M KCl) conditions. The glucocorticoid-binding component in KCl, spermidine, and MgCl2 extracts from CS nuclei was considerably larger and more asymmetrical [Stokes radius, 57 to 59 A; sedimentation coefficient, 3.64 to 3.70S; molecular weight, 90,000 daltons; frictional ratio, 1.8; axial ratio (prolate ellipsoid), 15] than the [3H]TA-macromolecular complex in KCl and spermidine extracts from CR nuclei[Stokes radius, 29 A; sedimentation coefficient, 3.23 to 3.30S; molecular weight, 40,000 daltons; frictional ratio, 1.25; axial ratio (prolate ellipsoid), 5]. Control experiments showed that the smaller size of the glucocorticoid-binding component in CR nuclei was probably not due to cleavage of a larger, CS-like complex during the extraction procedure. The larger size of the CS [3H]TA complex did not appear to result from aggregation of s a smaller species. No difference in physicochemical parameters of the binding component was observed if cells were labeled with [3H]dexamethasone instead of [3H]TA. However, [3H]dexamethasone complexes were less stable than those formed with [3H]TA as indicated by considerable dissociation of [3H]dexamethasone during gel filtration and gradient centrifugation. This may be due to the 3- to 5-fold lower relative binding affinity of [3H]dexamethasone. Analysis of [3H]TA-labeled cytosol by gel filtration and gradient centrifugation revealed the presence of a single binding component with physicochemical properties similar to those of nuclear [3H]TA complexes from the same strain of tumor. These results suggest that previously described differences in extractability of nuclear-associated [3H]TA between the CS and CR strains of mouse lymphoma P1798 and the lack of response of CR P1798 to glucocorticoid administration may be due, at least in part, to the presence of an altered glucocorticoid-binding component in the resistant tumor cells.
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PMID:Physicochemical differences between glucocorticoid-binding components from the corticoid-sensitive and -resistant strains of mouse lymphoma P1798. 47 39

Variations in flow rate through the loop of Henle in the range of 0--50 nl/min were induced using pressure controlled microperfusion. Simultaneously, with the aid of a second pressure-microperfusionsystem, the glomerular function of the same nephron was studied by continuous measurement of two parameters, early proximal flow rate (EPFR) and/or stop flow pressure (SFP). Elevation of loop perfusion above physiological values (40 nl/min) resulted in a drop of EPFR and SFP, whereas lowering perfusion rates had no effect. This feedback behaviour was studied in kidneys with different renin contents to test the role of the renin-angiotensin system in the mediation of the macula densa signal to the adjacent glomerular vessels. Renal renin content, measured after micropuncture experiments by incubation with substrate followed by radioimmunoassay of angiotensin I, was unaltered in control (Ia) and heminephrectomized rats (Ib), lowered in contralateral kidneys of 2 kidneys Goldblatt hypertensive rats (IIa), in DOCA- and salt-loaded rats (IIb), and in DOCA-, salt-loaded and heminephrectomized rats (IIc), and it was evaluated in clipped kidneys of Goldblatt hypertension rats (IIIa). Micropuncture evaluation of the tubuloglomerular feedback behaviour in these experimental groups revealed the following results: 1. a feedback response under all conditions independent of the widely varying renin contents (1000-fold), 2. an asymmetrical behaviour of the feedback response in all kidneys as demonstrated by suppression of EPFR and SFP at elevated loop flow rates, but no change of these parameters when loop flow was interrupted. 3. compared to controls the decrease of each GFR parameter between 0 and 40 nl/min loop perfusion was lower in DOCA- and salt-loaded rats (IIb, IIc). Additional heminephrectomy (IIc) had no further influence on the reduced feedback response in DOCA- and salt-loaded rats, whereas this maneuver reduced the renal renin content drastically. A somewhat higher response than in controls was found in heminephrectomized rats (IIb) and in clipped kidneys of Goldblatt hypertensive rats (IIIa). These different magnitudes of feedback responses do not correlate with the renal renin content. It has been concluded, therefore, that renal renin activity is not the sole determinant of the effectiveness of the tubuloglomerular feedback response.
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PMID:Tubuloglomerular feedback in rat kidneys of different renin contents. 123 32

Pinellia ternata lectin (PTL), a protein exhibiting hemagglutination activity and carbohydrate binding specificity to mannan was purified from rhizome of Pinellia ternata. In this work the actions of PTL on artificial lipid bilayer were investigated by means of the two-compartment system of Mueller and Rudin. The lipid bilayer with resistance more than 10G omega was formed by a solution of lecithin and cholesterol (20 mg/ml and 5 mg/ml respectively) in N-decane. The electrical properties of the lipid bilayer were investigated in voltage clamp mode. Several minutes after the addition of PTL (2 micrograms/ml) in one compartment the channel-like noise as well as a decrease of the resistance of the bilayer were observed. These actions were inhibited by mannan significantly. The resistance increase of the bilayer with PTL-channels could be observed from 2G omega to control level (greater than or equal to 10 G omega) immediately after addition of 40 micrograms/ml mannan. The discrete conduction steps were recorded at low concentration of PTL and at low holding potential. The predominant unit conductance was 35pS in symmetric KCl solution of 100 mmol/L. The selectivity of PTL-channel was estimated from Goldman-Hodgkin-Katz equation by measurement of the reversal potential in an asymmetrical salt solution. The results showed that PTL-channels were cation selective.
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PMID:[Cation channels formed in lipid bilayer by Pinellia ternata lectin]. 137 36

The human amniotic membrane may be considered a model for the prescreening evaluation of the membrane effects of several Mg salts because it is an asymmetrical membrane (polarity of the 2 sides: the ratio between the total ionic conductance Gt both ways and the ratio between the ionic flux from the mother to the fetus (F1) and the ionic flux from the fetus to the mother (F2) are different from 1), samples of which can be obtained without ethical problems, and which is easily usable. Whatever the tested salt, the ratio F1/F2 must be constant or increased without alterations of the ionic fluxes (+/-20%), because a toxic metal (As) has no effect on F1/F2, but strongly decreases the ionic fluxes. To apply this model to the study of the effects of Mg salts, two conditions should be considered: 1) Mg oral therapy: Mg deficit increases the membrane fluidity and the increase of Mg concentration rigidifies the membrane, i.e. decreases Gt; the plasma level of Mg being equal to 1 mM, Mg salts would be tested at 1 mM and Gt should be decreased; and 2) Mg parenteral therapy: the Mg effects should be opposite to those of pollutants and alcohol, which reduce Gt; a dose of 3 mM is chosen and Gt should be increased. The general scheme to study Mg salts is the following: observation of the variation of F1/F2 at 1 mM and of the evolution of Gt, and identical observations at 3 mM. This in vitro prescreening method, indirectly applicable to in vivo effects, gives a classification of Mg salts which may be completed by a study of the 10 components of Gt in the case of identical results for Mg salts.
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PMID:A new method of in vitro prescreening evaluation of several Mg salts. 150 33

A chamber filled with salt solution and separated into two compartments by a Teflon partition with a pore of 700 microns diameter was used to investigate the action of aureofuscin, a polyene antibiotics, on a planar lipid bilayer. The pore was covered with a bilayer formed by a N-decane solution of lecithin and cholesterol (20 mg/ml and 5 mg/ml). The electrical property and ionic permeability of the bilayer were studied by using voltage clamp method. Decrease of the bilayer resistance and the channel-like activity could be observed 20 min after the addition of aureofuscin (10-20 micrograms/ml) to one compartment. The existence of a transmembrane voltage and ionic gradient were not necessary for the channel-forming activity of aureofuscin. Discrete current steps were recorded at a concentration of 1.4 micrograms/ml aureofuscin, with a predominant unit conductance of 4-6 pS in a symmetric KCl, solution of 100 mmol/L. By using Goldmann-Hodgkin-Katz voltage equation the ionic selectivity of the channel formed by aureofuscin was estimated by the reversal potential measured in the asymmetrical solution system. The results showed that aureofuscin channels were more permeable to potassium ion than to chloride ion (PK/PCl approximately 5.2). These data may be used to explain the action of aureofuscin on neurotransmitter release and muscle membrane potential in addition to providing some explanation on its curing effect in clinical use.
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PMID:[Ionic channels formed in the lipid bilayer membranes by aureofuscin, a polyene antibiotics]. 171 13

Changes in intracellular [Ca2+] ([Ca2+]i) after cytokinin-treatment in protonema cells of the moss Funaria hygrometrica have been measured using the pentapotassium salt of Indo-1. The extent of dye loading strongly depended on lowering the pH of the incubation medium to 5.0. Exposing dye-loaded cells briefly with Mn2+ did not quench fluorescence suggesting that the source of fluorescence is from the cytoplasm and not from the cell wall. Indo-1 remains responsive to changes in [Ca2+]i in Funaria cells. The [Ca2+]i in quiescent cells (with and without extracellular Ca2+) is 250 nM, which is within the range of reported [Ca2+]i of other plant cells. Treatment of cells with extracellular cytokinin in 4 mM Ca2+ induced a three-fold increase in [Ca2+]i to 750 nM in target caulonema cells. This increase was not observed in Ca(2+)-free medium. These target cells respond to cytokinin treatment by an asymmetrical division, while non-target chloronema cells do not divide. Cytokinin appears to increase [Ca2+]i by extracellular Ca2+ uptake. However, non-target chloronema cells and tip cells also respond to cytokinin treatment by increasing [Ca2+]i. The differential physiological response of these cell types to hormonal stimulation must lie further down the signal transduction chain.
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PMID:Cytokinin increases intracellular Ca2+ in Funaria: detection with Indo-1. 172 37

The solution structure of human U1 snRNA was investigated by using base-specific chemical probes (dimethylsulfate, carbodiimide, diethylpyrocarbonate) and RNase V1. Chemical reagents were employed under various conditions of salt and temperature and allowed information at the Watson-Crick base-pairing positions to be obtained for 66% of the U1 snRNA bases. Double-stranded or stacked regions were examined with RNase V1. The dat gained from these experiments extend and support the previous 2D model for U1snRNA. However, to elucidate some aspects of the solution data that could not be accounted for by the secondary structure model, the information gathered from structure probing was used to provide the experimental basis required to construct and to test a tertiary structure model by computer graphics modeling. As a result, U1 snRNA is shown to adopt an asymmetrical X-shape that is formed by two helical domains, each one being generated by coaxial stacking of helices at the U1 snRNA cruciform. Chemical reactivities and model building show that a few nucleotides, previously proposed to be unpaired, can form A.G and U.U non Watson-Crick base-pairs, notably in stem-loop B. The structural model we propose for regions G12 to A124 integrates stereochemical constraints and is based both on solution structure data and sequence comparisons between U1 snRNAs.
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PMID:Solution structure of human U1 snRNA. Derivation of a possible three-dimensional model. 237 9

The cuticle of the gill lamina of the crayfish Astacus leptodactylus (E), mechanically isolated, was mounted in an Ussing chamber and examined for its electrical properties. The cuticle of the gill lamina obtained from exuviae had similar properties. When perfused with artificial fresh water (AFW) outside and Van Harreveld solution (VH) inside, the transcuticular potential Voi was negative with respect to the inside, and close to the equilibrium potential for Cl- (ECl-). CH3COO-, HCO3-, SO4(2-) and cations (Na+, K+, Ca2+, Mg2+ and NH4+) behaved as impermeant ions with respect to Cl-. A decrease of pH (brought about with CO2) from 8.5 to 6.0 in AFW, VH or both had no effect on the potential. The cuticle area specific conductance was 20-30 mS/cm2 when superfused with AFW outside and VH inside. The conductance decreased linearly with log [Cl-] when Cl- was replaced by CH3COO-. Rectification was obvious when internal Cl- was reduced to 5 mmol/l. The Cl- selectivity of the cuticle could also be demonstrated in perfusing the cuticle with a single salt (NaCl, KCl, CaCl2, MgCl2 or LaCl3) and in diluting that salt on one side of the preparation or in replacing Cl- by CH3COO-, SO4(2-) and HCO3-. The potential changed almost linearly with log [Cl-] and was close to ECl-. The inner face of the cuticle was found to be slightly less selective than the outer face. The relative permeabilities were calculated to be: PCl- = 1, PNa+ = 0.001, PHCO3- = 0.0006, PCH3COO- = 0.0002. The dilution of a Cl- -free salt resulted in a cationic potential. The relative permeabilities of cations (NH4+, K+, Na+, Ca2+ and Mg2+) were found to range within a factor 2. The permeability of the cuticle to HCO3-, CH3COO- and SO4(2-) was 2-5 times lower. The cuticle conductance was linearly related to the activity of the salt perfusing the two sides of the preparation at equal concentrations. The molar area specific conductance to chloride salts was 14 (mS/cm2)/(mmol/l). That of Cl- -free salts ranged from 1 to 20 (microS/cm2)/(mmol/l) depending on the salt used. It was deduced that PCl- is 2 X 10(-3) cm/s and that all the other ions tested have permeabilities of 10(-7)-10(-6) cm/s. With large intensity current pulses the cuticle exhibited rectifying properties and an asymmetrical behaviour. Increasing the pH of the perfusing solution reduced the transcuticular potential established with a Cl- gradient.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Ionic permeabilities of the gill lamina cuticle of the crayfish, Astacus leptodactylus (E). 241 Jun 7

Batrachotoxin-modified, voltage-dependent sodium channels from canine forebrain were incorporated into planar lipid bilayers. Single-channel conductances were studied for [Na+] ranging between 0.02 and 3.5 M. Typically, the single-channel currents exhibited a simple two-state behavior, with transitions between closed and fully open states. Two other conductance states were observed: a subconductance state, usually seen at [NaCl] greater than or equal to 0.5 M, and a flickery state, usually seen at [NaCl] less than or equal to 0.5 M. The flickery state became more frequent as [NaCl] was decreased below 0.5 M. The K+/Na+ permeability ratio was approximately 0.16 in 0.5 and 2.5 M salt, independent of the Na+ mole fraction, which indicates that there are no interactions among permeant ions in the channels. Impermeant and permeant blocking ions (tetraethylammonium, Ca++, Zn++, and K+) have different effects when added to the extracellular and intracellular solutions, which indicates that the channel is asymmetrical and has at least two cation-binding sites. The conductance vs. [Na+] relation saturated at high concentrations, but could not be described by a Langmuir isotherm, as the conductance at low [NaCl] is higher than predicted from the data at [NaCl] greater than or equal to 1.0 M. At low [NaCl] (less than or equal to 0.1 M), increasing the ionic strength by additions of impermeant monovalent and divalent cations reduced the conductance, as if the magnitude of negative electrostatic potentials at the channel entrances were reduced. The conductances were comparable for channels in bilayers that carry a net negative charge and bilayers that carry no net charge. Together, these results lead to the conclusion that negative charges on the channel protein near the channel entrances increase the conductance, while lipid surface charges are less important.
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PMID:Batrachotoxin-modified sodium channels in planar lipid bilayers. Ion permeation and block. 244 Sep 77

The surface tension of glycerylmonooleate-hexadecane lipid bilayer membranes and the lifetime of gramicidin A channels were measured at various concentrations of the surrounding solutions. For HCl the surface tension is essentially constant at approximately 5 mN/m up to approximately 1 M, whereas the average lifetime increases approximately 40-fold. At higher concentrations the surface tension decreases markedly. For CsCl the surface tension is constant up to about 1 M then increases with salt level. The average lifetime in this case increases about sixfold. In both cases the lifetime levels off and even decreases at higher salt levels. The increase in lifetime observed with ion activity is therefore qualitatively different from, and not explained by, the established dependence of lifetime on membrane properties (Elliot, J.R., D. Needham, J.P. Dilger, and D.A. Haydon. 1983. Biochim. Biophys. Acta. 735:95-103). We have previously proposed that ion occupancy is a determinant of channel stability, and to test this hypothesis the voltage dependence of channel lifetime was measured in asymmetrical solutions. For the case of a potassium chloride solution on one side of the membrane and a hydrogen chloride solution, on the other, the voltage dependence of the lifetime is asymmetrical. The asymmetry is such that when the electrical field is applied in the direction of the chemical gradient for each of the ions, the channel lifetime approaches, at increasing field strengths, that of a symmetrical solution of the respective ion. The voltage dependence of the surface tension, on the other hand, is negligible for the range of voltages used. These results, and the earlier findings that the order of the lifetimes for the alkali cations generally agree with the order of the permeability selectivity of the gramicidin A channel, support the hypothesis that ion occupancy is a major factor determining the lifetime of gramicidin A channels. The effects of multivalent blockers and osmotic agents were also tested. Ba2", La3+,and Mg2" decrease the lifetime and conductance markedly. Sucrose and urea increase the lifetime and decrease the conductance. The voltage dependence of the lifetime in symmetrical solutions was examined. Contrary to previous reports it was found that the lifetimes for K+, Cs', and H+ are voltage dependent. For 0.5 M HCI the lifetime decreases monotonically by .60% at 150 mV, and for 0.5 M KCI the lifetime increases by -60% at 200 mV. Below 10 mM there is no effect of voltage for H+, K+, and Cs+. These effects of blockers, osmotic agents, and voltage on the lifetime, as well as the lack of effect of voltage at low salt levels, are consistent with the occupancy hypothesis.
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PMID:Evaluation of surface tension and ion occupancy effects on gramicidin A channel lifetime. 245 76

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