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1Author    Wilhelm Hasselbach, A. Ndrea Migala, Gafni, P. D. BoyerRequires cookie*
 Title    Invariance of Stoichiometry of the Sarcoplasmic Reticulum Calcium Pump at Physiological Calcium Concentrations — a Reevaluation  
 Abstract    The decline of the transport ratio of the sarcoplasmic calcium pump observed in a recent study (A. results from the retardation of calcium oxalate precipitation at low calcium/protein ratios. The prevailing high internal calcium level supports a rapid calcium backflux and a compensatory ATP hydrolysis during net calcium uptake which reduces the transport ratio. Yet, the determined calcium back­ flux does not fully account for the decline of the transport ratio. A supposed modulation of the stoichiometry of the pump by external calcium (0.1 ^m) is at variance with results of previous studies showing a constant transport ratio of two in the same calcium concentration range. 
  Reference    Z. Naturforsch. 40c, 571—575 (1985); received May 20 1985 
  Published    1985 
  Keywords    Sarcoplasmic Reticulum, Calcium Pump, Stoichiometry 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0571.pdf 
 Identifier    ZNC-1985-40c-0571 
 Volume    40 
2Author    Peter Laggner, Josef Suko, Christian Punzengruber, Rudolf PragerRequires cookie*
 Title    Electron Spin Resonance Studies on Conformational Changes of the Sarcoplasmic Reticulum Ca 2+ -ATPase Induced by Synergistic Action of Calcium and ATP  
 Abstract    Changes in motional properties of the -SH group environment in sarcoplasmic reticulum ATPase [1] induced by addition of specific ligands to sarcoplasmic reticulum membrane vesicles were investigated systematically by electron spin resonance (e.p.r.) spectro-scopy. Alternatively, two kinds of iodoacetamide analog spin labels, 4-(2-iodoacetamido)-2,2,5,5-tetramethyl-l-pyrrolidinyl-N-oxyl (label I) and 4-(2-iodoacetamido)-2,2,6,6-tetra-methyl-l-piperidinyl-N-oxyl (label II) were used. The labeling conditions were chosen such that less than three moles of -SH groups per mole of ATPase reacted with the spin labels. A marked increase in isotropic motion of either spin label was observed on addition of calcium in millimolar concentrations plus ATP or /S-y-methylene ATP. Qualitatively similar but smaller changes were also observed with inosine 5'-triphosphate (ITP), acetylphosphate, or ADP in the presence of calcium. These effects were independent of added magnesium. The spectral changes induced by ß-y-methylene ATP, which binds to the ATPase but is not hydrolyzed, and those of calcium plus ADP suggest a conformational change due to simultaneous binding of these ligands in the absence of enzyme phosphoryla-tion. These changes in e.p.r. spectra were different in quality and magnitude from those observed upon separate binding of calcium or adenine nucleotides. The two spin labels, differing only in their numbers of heterocyclic ring atoms, were found to reflect environmental changes in different ways. This demonstrates the usefulness of employing different spin labels to detect and interpret structural transitions in macro-molecular assemblies. The active transport of calcium by sarcoplasmic reticulum membranes isolated from skeletal muscle is generally considered to be a multistep process [1, 2], Several models for the reaction sequence of calcium translocation by the calcium pump of sarcoplasmic reticulum have been proposed on the basis of kinetic experiments [2-11]. In order to detect and characterize structural alterations of the ATPase in the calcium transport cycle, e.p.r. spectroscopic investigations of spin-labeled sarco-plasmic reticulum preparations, first introduced by 
  Reference    Z. Naturforsch. 36b, 1136—1143 (1981); received February 2 1981 
  Published    1981 
  Keywords    Sarcoplasmic Reticulum, Spin Labeling, Calcium-ATPase 
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 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-1136.pdf 
 Identifier    ZNB-1981-36b-1136 
 Volume    36 
3Author    PierreM. Ermier, Wilhelm HasselbachRequires cookie*
 Title    The Effect of Calcium and Phosphate on the Biphasic Calcium Uptake by the Sarcoplasmic Reticulum  
 Abstract    The amplitude of the fast uptake and the initial rate of the slow uptake increase with in­ creasing free calcium concentrations, up to 30 [xu. In that range, both processes are correlated to each other. At higher concentrations, the slow uptake is more inhibited than the fast uptake. The fast uptake shows a maximum amplitude which remains unchanged in the presence of phosphate. The slow uptake leads to a nearly complete depletion of the external calcium, and its rate is pro­ portional to the phosphate concentration, even at physiological range. The sarcoplasmic ATPase liberates inorganic phosphate and the slow uptake 
  Reference    (Z. Naturforsch. 30c, 777 [1975]; received July 17 1975) 
  Published    1975 
  Keywords    Sarcoplasmic Reticulum, Calcium, Phosphate, Flow Dialysis 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0777.pdf 
 Identifier    ZNC-1975-30c-0777 
 Volume    30 
4Author    Wilhelm Hasselbach, Vera KoenigRequires cookie*
 Title    Low Affinity Calcium Binding Sites of the Calcium Transport ATPase of Sarcoplasmic Reticulum Membranes  
 Abstract    Calcium binding sites having low affinity constants of < 103 M-1 were titrated in native sarcoplasmic reticulum vesicles as well as in lipid deprived m em branes and in the isolated calcium transport ATPase. Short time calcium binding m easurem ents and the determ ination o f the calcium binding heat allow to distinguish low affinity calcium binding sites located on the external surface of the sarcoplasmic reticulum m em branes from those present in the section o f the transport molecule directed to the vesicular space. The same num ber o f internal binding sites was found for preparations deprived of their lipid content as well as of preparations depleted o f their lipids and of their accessorial proteins. Magnesium interferes with calcium binding to the external as well as to the internal low affinity calcium binding sites. The im plications o f the existence o f the low affinity calcium binding sites in the internal section o f the calcium transport ATPase are discussed. 
  Reference    Z. Naturforsch. 35c, 1012 (1980); received A ugust 27 1980 
  Published    1980 
  Keywords    Sarcoplasmic Reticulum, Calcium Binding, Low Affinity Binding Sites 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-1012.pdf 
 Identifier    ZNC-1980-35c-1012 
 Volume    35 
5Author    Gertrude Swoboda, Wilhelm HasselbachRequires cookie*
 Title    Bile Salt Delipidation, Residual Phospholipids and Reactivation o f the Ca2+-ATPase from Sarcoplasmic Reticulum  
 Abstract    1. Delipidation o f the Ca2+-ATPase o f sarcoplasmic reticulum membranes by gel chro­ matography employing ionic detergents (cholate, deoxycholate and mixtures o f both) in the presence of glycerol has been studied with respect to residual phospholipids and ATPase activi­ ties. 2. The extent o f delipidation depends on the detergent chosen and on the ionic strength o f the elution buffer. Increasing ionic strength favours a more effective removal o f phospholipids, down to about 1 phospholipid molecule per ATPase molecule. 3. The residual ATPase activities o f the delipidated preparations are negligibly low. Extensive restoration of the Ca2+-dependent ATPase activity has been achieved by oleic acid, a lysolecithin (myristoylglycerophosphocholine) and a lecithin (dimyristoylglycerophosphocholine). The per­ centage of reactivation by oleate depends linearly on the amount o f residual phospholipids and on the detergent employed. 4. After gel filtration through an Ultrogel or Sepharose column containing 1% cholate in the elution buffer the delipidated ATPase is eluted as a reactivatable high molecular aggregate, whereas 1% deoxycholate favours the formation o f completely lipid-free monomeric units which cannot be reactivated, however. A high molecular aggregate is also formed in deoxycholate, the ratio of monomer to polymer depending on the solubilizing and elution conditions. 5. The residual lipids are always composed o f a mixture o f all different lipid classes present in the native sarcoplasmic vesicles, even at high degrees o f delipidation. Specific changes with vary­ ing extent of delipidation were not detected. 
  Reference    Z. Naturforsch. 37c, 289—298 (1982); received December 7 1981 
  Published    1982 
  Keywords    Sarcoplasmic Reticulum, Bile Salts, Delipidation, Reactivation, Lipids 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0289.pdf 
 Identifier    ZNC-1982-37c-0289 
 Volume    37 
6Author    Hans Liidi, Bernhard Rauch, Wilhelm HasselbachRequires cookie*
 Title    The Influence of Detergents on the Ca2+-and Mg2+-Dependent Adenosine Triphosphatase of the Sarcoplasmic Reticulum  
 Abstract    During the stepwise solubilization of sarcoplasmic reticulum vesicles with detergents, the following changes in the structural and enzymatic properties of the preparation are observed: 1. The viscosity of the vesicular suspension initially rises. This change is accompanied by the formation of elongated tubules. Subsequently the membranes are completely desintegrated, resulting in a considerable reduction of the viscosity. 2. A decrease in the activity of the Ca2+-dependent ATPase, which is restored after complete solubilization. 3. A decrease in the change of intrinsic tryptophan-fluorescence on removal of calcium ions, which is also restored after complete solubilization. 4. A decrease of the calcium affinity of the ATPase. 5. A decrease in the amount of phosphorylated protein formed by the incorporation of inorganic phosphate. On the other hand, the amount of phosphoprotein formed from ATP is not affected during solubilization. 6. The dependence of the initial rates of phosphoprotein formation from inorganic phosphate on either magnesium or inorganic phosphate at low concentrations of the respective ligand changes from an S-shape profile to a normal hyperbolic profile after solubilization. 
  Reference    Z. Naturforsch. 37c, 299—307 (1982); received January 1982 
  Published    1982 
  Keywords    Sarcoplasmic Reticulum, ATPase, Detergent, Protein-Phosphorylation, Kinetics 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0299.pdf 
 Identifier    ZNC-1982-37c-0299 
 Volume    37 
7Author    LudwigM G Heilmeyer, M. Agdolna VarsanyiRequires cookie*
 Title    Regulation of the Sarcoplasmic Reticular Ca2+ Transport ATPase by Phosphorylation and Dephosphorylation  
 Abstract    At 0.1 m g/m l protein and 0.45 um free Ca2+ 1 m ol trichloroacetic acid precipitable phosphate is incorporated into 100,000 g SR protein as hydroxilam ine sensitive acylphosphate. At nearly physiological protein concentration (ca. 7 m g/m l) a total o f ca. 0.8 m ol phosphate/100,000 g pro­ tein is incorporated, from which a fraction o f 0.3 m o l/1 00,000 g protein is insensitive to the hy-droxylamine treatment, i.e. it is alkylphosphate. Phosphorylase kinase accelerates the al­ 
  Reference    Z. Naturforsch. 37c, 682—684 (1982); received January 4/M arch 19 1982 
  Published    1982 
  Keywords    Sarcoplasmic Reticulum, Ca Transport, R egulation, P hosphorylation 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0682.pdf 
 Identifier    ZNC-1982-37c-0682 
 Volume    37 
8Author    N. Ald, J. Scales, StefanR H IghsmRequires cookie*
 Abstract    lec tr o n M ic r o sc o p ic E vid en ce fo r th e T ran sm em b ran e D isp la ce m e n t o f C alcium A T P a se Incubation o f the Ca2+-ATPase in vanadate solutions leads to the formation o f two-dim ensional arrays in the sarcoplasmic reticulum membrane. Electron micrographic freeze fracture replicas show depressions on the inner leaflet for the first time. This indicates that the ATPase has moved perpendicular to the plane o f the m embrane. Our results also suggest that aggregation o f the Ca2+-ATPase into the two-dim ensional arrays occurs before they move into the membrane. These phenom ena were observed as soon as 15 minutes after vanadate was added. The effects o f vanadate appear to be com pletely reversible. When SR was incubated in the vanadate solutions and was then diluted into a buffer containing Ca2+ and ATP, the ATPase activity was normal for up to several hours o f incubation and only somewhat reduced after 3 days. 
  Reference    Z. Naturforsch. 39c, 177 (1984); received May 30/Septem ber 29 1983 
  Published    1984 
  Keywords    Sarcoplasmic Reticulum, Ca2+-ATPase, Ion Transport, Vanadate 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0177_n.pdf 
 Identifier    ZNC-1984-39c-0177_n 
 Volume    39 
9Author    Requires cookie*
 Title    Thyroxine Induced Transformation in Sarcoplasmic Reticulum of Rabbit Soleus and Psoas Muscles  
 Abstract    The properties of the sarcoplasmic reticulum membranes isolated from slow-twitch type I soleus and fast-twitch type II psoas muscles of control and thyroxine treated rabbits were comparatively studied. Membrane yield, maximal calcium storing capacity, ATP-supported calcium uptake, calcium-dependent ATPase activity and calcium-dependent phosphoprotein formation were found to be 3—10 fold higher in psoas than in soleus preparations. Membrane yield, calcium-dependent ATPase activity, ATP-supported calcium transport and calcium-dependent phospho­ protein are at least twice enhanced in the membranes from soleus muscles of animals treated for 14—21 days with thyroxine. The corresponding capacities of the membranes from psoas muscles are not further augmented by the same thyroxine treatment. The maximal calcium storing capaci­ ty of the psoas membranes is their sole specific property which is significantly increased. The changes in the properties of the soleus muscles' sarcoplasmic reticulum membranes are engen­ dered by an increase from 5 to 30—50% in the number of type II fibres. Since the calcium transporting properties of the sarcoplasmic reticulum membranes from type II fibres qualitatively differ from those of type I fibres, thyroxine does not only affect quantitative but also qualitative parameters of the muscles' sarcoplasmic reticulum membrane system. 
  Reference    Z. Naturforsch. 40c, 726—734 (1985); received July 11 1985 
  Published    1985 
  Keywords    Sarcoplasmic Reticulum, Thyroxine, Fast and Slow Twitch Muscles 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0726.pdf 
 Identifier    ZNC-1985-40c-0726 
 Volume    40 
10Author    P. Ankaj, M. Edda, W. Ilhelm, H. AsselbachRequires cookie*
 Title    Formation and Decay of the Vanadate Complex of the Sarcoplasmic Reticulum Calcium Transport Protein  
 Abstract    The calcium free sarcoplasmic reticulum calcium transport ATPase incorporates in the presence of magnesium ions approx. 8 nmol monovanadate per mg protein, indicating the formation of a complex containing one vanadate residue per enzyme molecule. On ligand-removal or dilution, the saturated enzyme complex displays biphasic decay kinetics, while the unsaturated complex slowly dissociates monophasically. — Ligand competition by raising the concentrations of un­ labeled vanadate results in a progressive decrease of the dissociation rate of the unsaturated enzyme. The complicated dissociation kinetics indicate a sequential mode of interaction between two ligand binding sites. The one to one stoichiometry of the complex suggests that the two sites are located at adjacent ATPase molecules. — It appears unlikely that the decay of the enzyme, vanadate complex is retarded by the formation of a stable quaternary complex between the enzyme, magnesium, mono-and polyvanadate. 
  Reference    Z. Naturforsch. 40c, 876 (1985); received August 23 1985 
  Published    1985 
  Keywords    Sarcoplasmic Reticulum, Calcium Transport ATPase, Vanadate 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0876.pdf 
 Identifier    ZNC-1985-40c-0876 
 Volume    40 
11Author    M. Artina, U. Ngeheuer, A.Ndrea Migala, Wilhelm HasselbachRequires cookie*
 Title    Is the Calcium Pump Involved in Calcium Release?  
 Abstract    The blockage of all thiol residues accessible to the mercurial mersalyl in the sarcoplasmic reticulum m em branes resulting in complete inactivation of the m em branes' calcium transport system does interfere neither with caffeine-nor calcium-induced calcium release from actively loaded mem brane vesicles. In troduction 
  Reference    Z. Naturforsch. 41c, 647—651 (1986); received March 18 1986 
  Published    1986 
  Keywords    Sarcoplasmic Reticulum, Calcium Release, Caffeine, Thiol Blockage 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0647.pdf 
 Identifier    ZNC-1986-41c-0647 
 Volume    41 
12Author    Wilhelm Hasselbach, Andrea MigalaRequires cookie*
 Title    How Many Ryanodine Binding Sites Are Involved in Caffeine Induced Calcium Release from Sarcoplasmic Reticulum Terminal Cysternae Vesicles?  
 Abstract    The inhibition by ryanodine of caffeine induced calcium release from actively loaded heavy sarcoplasmic vesicles has been studied in order to analyse the relation between the occupancy of the vesicular calcium release channels by ryanodine and channel function. Ryanodine bind­ ing was monitored with [3H]ryanodine under ionic conditions favouring the establishment of binding equilibrium. Binding follows 1 : 1 stoichiometry yielding dissociations constants be­ tween 7 — 12 nM and 12-15 pmol ryanodine/mg vesicular protein as maximum number of ryanodine binding sites. When ryanodine labeling was monitored by measuring the decline of the amplitude of caffeine induced calcium release 50% inhibition occurred at a free ryanodine concentration of 1 nM. At this concentration less than 10% of the available ryanodine binding sites are occupied. Caffeine induced calcium release is completely abolished when 3 pmol ryanodine/mg have reacted. A corresponding divergence between ryanodine binding and its effect on caffeine induced calcium release was observed when the initial rate of ryanodine binding was measured either by labeling the vesicles with [3H]ryanodine or by following the decline with time of caffeine induced calcium release. Caffein induced calcium release declines four times faster than the fraction of unoccupied ryanodine binding sites, k = 4.3 x 104 m -1 s_1 versus 1.2 x 104 M" 1 s-1. The observed interrelation between the occupation of ryanodine bind­ ing sites and its effect on caffeine induced calcium release indicates that the caffeine sensitive calcium channel functions as an assembly of at least 4 ryanodine binding sites whereby the occupation of one site suffices to abolish calcium release. The stoichiometric composition ap­ pears to be not fixed but might change according to the size of the fraction of ryanodine recep­ tors exhibiting caffeine sensitivity. The reported data were evaluated according to the algo­ rithm derived by H. Asai and M. F. Morales, J. Biol. Chem. 4, 830-838 (1965) for the activity of a macromolecule and the extent of an inhibiting reaction. 
  Reference    Z. Naturforsch. 47c, 136—147 (1992); received August 7 1991 
  Published    1992 
  Keywords    Sarcoplasmic Reticulum, Caffeine, Calcium Release, Ryanodine Binding 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0136.pdf 
 Identifier    ZNC-1992-47c-0136 
 Volume    47 
13Author    Wilhelm Hasselbach, Andrea MigalaRequires cookie*
 Title    Modulation by Ryanodine of Active Calcium Loading and Caffeine Induced Calcium Release of Heavy Sarcoplasmic Reticulum Vesicles  
 Abstract    The effect o f ATP on the calcium release channel in heavy sarcoplasmic reticulum vesicles modulated by ryanodine has been analyzed by monitoring active calcium uptake and caffeine induced calcium release under near physiological conditions. N ative as well as ryanodine reacted vesicles display a complex time course o f calcium uptake resulting in nearly complete exhaustion o f medium calcium when ATP in combination with an ATP-regenerating system, in contrast to ATP alone, or dinitrophenyl phosphate, were used to support calcium uptake. Applying o f dinitrophenyl phosphate as energy yielding substrate, not affecting channel activi­ ty, allowed to estimate the fraction o f light vesicles devoided o f calcium channels contam inat­ ing the heavy preparation as the fraction that stores calcium after the preparation has been treated with channel opening, low concentrations o f ryanodine (1 jim). Calcium uptake by contam inant light vesicles (25%) cannot account for calcium storage, as well as, abolition o f caffeine induced calcium release o f ryanodine treated heavy vesicles. Calcium uptake o f native and ryanodine treated vesicles is accompanied by the uptake o f equivalent amounts o f inor­ ganic phosphate arising from ATP hydrolysis indicating that calcium is mainly stored as cal­ cium phosphate. The momentary capability o f the preparation to accumulate calcium was measured by activating calcium uptake during the calcium storage period with 0.2 m M 45CaCl2 and 4 m M phosphate at short time intervals. A significant increase o f the momentary uptake activity with time was observed being more pronounced for ryanodine treated than for native vesicles indicating that under regenerating conditions, A TP can induce closing o f the native and even more effectively o f the ryanodine modified calcium release channels. 
  Reference    Z. Naturforsch. 47c, 429 (1992); received December 4 1991/March 16 1992 
  Published    1992 
  Keywords    Sarcoplasmic Reticulum, Caffeine Induced Calcium Release, Ryanodine 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0429.pdf 
 Identifier    ZNC-1992-47c-0429 
 Volume    47 
14Author    Wilhelm Hasselbach, Andrea MigalaRequires cookie*
 Title    Modulation by Monovalent Anions of Calcium and Caffeine Induced Calcium Release from Heavy Sarcoplasmic Reticulum Vesicles  
 Abstract    Both calcium and caffeine induced calcium release from actively loaded heavy sarcoplasmic reticulum vesicles were studied to analyze the dependence o f both activities on the com position o f the release medium with respect to monovalent anions. Calcium is unable to induce net cal­ cium release while caffeine remains effective as releasing agent when the experimental media contain neither chloride nor nitrate ions. Caffeine induced calcium release is not suppressed by chelating residual medium calcium (approximately 0 .5 -1 (j m) with 2 m M EGTA added 15 s prior to 10 m M caffeine. Calcium release from vesicles loaded in media containing 0.2 m glu­ conate as monovalent anion is induced when the medium is supplemented with chloride or nitrate. The release amplitude increases linearly when K-gluconate is replaced by KC1. At con­ stant ionic strength the release amplitude becomes maximal at a chloride concentration o f 0.2 m . The chloride effect com pletely disappears when 2 m M EGTA are added simultaneously. When chloride is replaced by nitrate, as releasing agent, maximal release is achieved already by addition o f 0.1 m K-nitrate. The releasing effect o f nitrate can only partially be suppressed by EGTA. The different effectiveness o f gluconate, chloride and nitrate as calcium release sup­ porting ions corresponds to their activating effect on the binding o f ryanodine to the calcium release channel in the vesicular membranes. 
  Reference    Z. Naturforsch. 47c, 440 (1992); received December 4 1991/March 16 1992 
  Published    1992 
  Keywords    Sarcoplasmic Reticulum, Calcium Release, Chloride, Nitrate, Ryanodine 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0440.pdf 
 Identifier    ZNC-1992-47c-0440 
 Volume    47 
15Author    Kristine Kranzhöfer, Bruno Agostini, Luisa De, M. Artino, Wilhelm HasselbachRequires cookie*
 Title    Micromorphometric Evaluation of Changes in Symmetry of Sarcoplasmic Reticulum Membranes Induced by Vanadate  
 Abstract    Electron micrographs of light sarcoplasmic vesicles fixed with glutaraldehyde and osmium tetroxide followed by contrasting with uranyl acetate and lead citrate have been evaluated by registering their membrane profiles with a microdensitometer. The asymmetric arrangement o f the two layers of the vesicular membrane could be ascertained by demonstrating a ratio of 1.5 for the thickness o f the outer versus the inner membrane layer which is in general agreement with the proposed protein structure o f the calcium transport enzyme. Treatment of the vesicles with low concentrations of vanadate (0.1 mM) results in a significant lowering of the symmetry ratio by 20% by reducing mainly the thickness of the outer membrane leaflet. Removal of the membrane lipids by treating the vesicles with phospholipase A2 and bovine serum albumin di­ minishes the membrane surface by 50% resulting in a significant increase o f both the mem­ brane thickness and the asymmetry ratio by 30 and 12% respectively. The vanadate induced reduction of membrane asymmetry is accentuated after delipidation indicating that the mem­ brane lipids are not essential for the asymmetric appearance of the native membrane. The sta­ bility of the spherical form o f the vesicles to delipidation implies that the transport molecules are conically shaped allowing strong mutual interactions. At a measured height of the mole­ cule of 80 A in the membrane, the vanadate induced change in symmetry would be brought about by compensatory changes o f less than 3 A of the outer (35 Ä) and the inner (25 Ä) diameter of the cone. 
  Reference    Z. Naturforsch. 47c, 762—772 (1992); received May 19 1992 
  Published    1992 
  Keywords    Sarcoplasmic Reticulum, Membrane Symmetry, Vanadate, Micromorphometry 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0762.pdf 
 Identifier    ZNC-1992-47c-0762 
 Volume    47 
16Author    Pierre Mermier, Wilhelm HasselbachRequires cookie*
 Title    The Biphasic Ca2+-Uptake by the Fragmented Sarcoplasmic Reticulum  
 Abstract    The non-equilibrium dialysis has been used for kinetic studies of ATP dependent calcium up­ take by the sarcoplasmic reticulum. The uptake displays two phases, which are defined as fast and slow uptake. The former is an exponential function of time, with a half-life time of approxi­ mately 15 —20 sec, the latter presents the characteristics of an autocatalytic reaction. The fast uptake is characterized by its amplitude, the slow uptake by its rate. Compared with the fast up­ take, the slow uptake requires higher amounts of Mg2+ or ATP, and is more sensitive to pH variations and aging. The reasons which formerly prevented the resolution of the second phase from the first are discussed. It is concluded that the fast uptake is not a simple binding reaction, and that the slow uptake is more sensitive to changes by the vesicular membrane. 
  Reference    (Z. Naturforsch. 30c, 593 [1975]; received June 6 1975) 
  Published    1975 
  Keywords    Flow Dialysis, Active Calcium Transport, Calcium Storage, Sarcoplasmic Reticulum 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0593.pdf 
 Identifier    ZNC-1975-30c-0593 
 Volume    30 
17Author    Marvin Stromer, Wilhelm HasselbadhRequires cookie*
 Title    Fusion of Isolated Sarcoplasmic Reticulum Membranes  
 Abstract    Fragmented sarcoplasmic reticulum (FSR) vesicles from rabbit muscle were suspended in 1.5 — 5% glycerol solutions and were pelleted onto aluminum foil disks in a modified centrifuge tube. Examination of these pellets in the electron microscope after drying for 2 — 2.5, 4 — 5.5, and 21 hours revealed a progression of changes. First, distances between individual, round vesicles decreases. Next, somewhat flattened vesicles establish limited areas of contact with adjacent vesicles. Finally, vesicle fusion occurs and extended areas of double bilayers are formed. A water loss-time interaction appears to be needed for the fusion process. A Hg-phenyl azoferritin com­ pound was used as a marker to identify intra-and extra-vesicular space in the fused samples. Quantitative measurements of birefringence during imbibition of pellet slices in a graded series of glycerol solutions indicates a steadily increasing amount of birefringence until 60 — 80% glycerol (»/ = 1.41 —1.43) is readied. The plateau seen in this part of the curve is again followed by steadily increasing birefringence at higher glycerol concentrations. This interruption in the birefringence curve is presumably due to a matching of the refractive indices of the glycerol solution and a lipid component in the membranes. 
  Reference    (Z. Naturforsch. 31c, 703 [1976]; received August 23 1976) 
  Published    1976 
  Keywords    Membrane Fusion, Sarcoplasmic Reticulum, Glycerol, Electron Microscopy, Polarizing Microscopy 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0703.pdf 
 Identifier    ZNC-1976-31c-0703 
 Volume    31 
18Author    L. RaeymaekersRequires cookie*
 Title    The Sarcoplasmic Reticulum of Smooth M uscle Fibers  
 Abstract    The ability of the sarcoplasm ic (endoplasmic) reticulum (SR, ER) of smooth muscle cells to accumulate Ca was dem onstrated by measuring the uptake of 45Ca in fibers which were chemically skinned with saponin, and by electron cytochemistry of the accum ulated Ca. The Ca uptake was dependent on ATP and it was stim ulated by oxalate, as it is the case in SR of striated muscle. Electron microscopy of the skinned smooth muscle preparations revealed the presence o f calcium oxalate deposits in the reticulum . The SR vesicles were isolated from several sm ooth muscles. The purification was carried out by taking advantage o f the density increase o f the SR vesicles after loading with calcium in the presence of oxalate. Among the muscles investigated the smooth muscle of the pig stomach was found to be the most suitable and it was selected for further biochem ical and m orphological characterization of the SR vesicles. These vesicles, which contain calcium oxalate crystals, were able to accumulate an additional am ount of Ca. The Ca uptake was supported by several energy yielding substrates. T h eir order o f potency was ATP > dATP ~ U TP > ITP > G TP ~ CTP. The rate of Ca uptake was two orders o f m agnitude slower than that in SR of skeletal muscle. The measurement of the level o f phosphorylated Ca transport interm ediate showed that this difference is due to smaller num ber of calcium transport sites per vesicle. The distribution o f intram em ­ brane particles in freeze-fractured specimens is in agreem ent with this conclusion. 
  Reference    Z. Naturforsch. 37c, 481—488 (1982); received January 25 1982 
  Published    1982 
  Keywords    Smooth Muscle, Microsomes, Sarcoplasmic Reticulum, Calcium Metabolism, Electron Microscopy 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0481.pdf 
 Identifier    ZNC-1982-37c-0481 
 Volume    37 
19Author    Rolf ThieleczekRequires cookie*
 Title    Electromechanical Coupling III. Estimation of the Ca Storage Capacity of the SR by Analysing the Time Course of Caffeine- Induced Tension Transients of Skinned Muscle Fibres  
 Abstract    The Ca uptake o f the SR o f a skinned fibre, w hich was studied with an indirect m ethod, shows a biphasic time course. A total Ca concentration betw een 8 and 23 mM was accumulated in the SR by an initial fast process (tä4.7 s) . This C a-uptake activity o f the SR is high enough to bring about 
  Reference    Z. Naturforsch. 37c, 709 (1982); received January 18/M arch 16 1982 
  Published    1982 
  Keywords    Skinned Fibre, Sarcoplasmic Reticulum, Calcium, C affeine, Tension Transients 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0709.pdf 
 Identifier    ZNC-1982-37c-0709 
 Volume    37 
20Author    Hans Liidi, Wilhelm HasselbachRequires cookie*
 Title    Fluorescence Studies on N-(3-Pyrene)Maleinimide-Labeled Sarcoplasmic Reticulum ATPase in Native and Solubilized Membranes  
 Abstract    Fluorescence polarization and formation of excimers were studied in N-(3-pyrene)malein-imide-labeled sarcoplasmic reticulum vesicles. 1. The polarization of pyrenemaleinimide labeled vesicles does not change with temperature and shows a pronounced decrease at labeling concentrations larger than 1 mol pyrenemaleinimide per 10 mol ATPase. 2. Solubilization of the membrane with myristoylglycerophosphocholine renders the polariza­ tion temperature dependent, but does not affect the concentration dependent depolarization observed in native vesicles. 3. The polarization of labeled vesicles is much smaller than to be expected from the tempera­ ture independent polarization indicating that the pyrenemaleinimide polarization did not monitor the rotation of the entire ATPase. Thus segmental motion occurs. 4. Pyrene excimers are observed at label concentrations larger than 1 mol label per 2.5 mol ATPase. 5. The amount of excimers was critically dependent on added detergents. From the fact that non-solubilizing amounts of myristoylglycerophosphocholine strongly reduced the amount of pyrene excimers it is concluded that in the native sarcoplasmic reticulum vesicles at least two ATPase molecules must be in close contact. 
  Reference    Z. Naturforsch. 37c, 1170 (1982); received August 16 1982 
  Published    1982 
  Keywords    Sarcoplasmic Reticulum, ATPase, Protein-Protein-Interactions, Fluorescence Polarization, Excimer Formation 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-1170.pdf 
 Identifier    ZNC-1982-37c-1170 
 Volume    37