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L Dux

Publications and source records attributed to L Dux.

At least 73 records · Page 4Linked to original sources
PubMed1985

Crystallization of the Ca2+-ATPase of sarcoplasmic reticulum by calcium and lanthanide ions.

Two-dimensional crystalline arrays of Ca2+-ATPase molecules develop in sarcoplasmic reticulum vesicles exposed to Ca2+ or lanthanide ions. The Ca2+- or lanthanide-induced crystals are presumed to represent the E1 conformation of the Ca2+-ATPase, and their crystal form is clearly different from the earlier described E2 crystals induced by Na3VO4 in the presence of ethylene glycol bis(beta aminoethyl ether)-N,N,N',N'-tetraacetic acid (Taylor, K. A., Dux, L., and Martonosi, A. (1984) J. Mol. Biol. 174, 193-204). Analysis of the crystalline arrays by negative staining or freeze-fracture electron microscopy reveals obliquely oriented rows of particles corresponding to individual Ca2+-ATPase molecules. Computer analysis of the negatively stained lanthanide-induced crystalline Ca2+-ATPase arrays shows that the molecules are arranged in a P1 lattice. The pear-shaped profiles of Ca2+-ATPase molecules seen in projection in the density maps are similar to those seen in vanadate-induced crystals. The space group and unit cell dimensions of the E1 crystals are consistent with Ca2+-ATPase monomers as structural units, while the vanadate-induced E2 crystals form by lateral aggregation of chains of Ca2+-ATPase dimers. The transition between the E1 and E2 conformations may involve a shift in the monomer-oligomer equilibrium of the Ca2+-ATPase. The formation of E1 crystals by PrCl3 is promoted by inside negative membrane potential, presumably through stabilization of the E1 conformation of the enzyme. Cleavage of the Ca2+-ATPase by trypsin into two major fragments (A and B) did not interfere with the Ca2+- or the Pr3+-induced crystallization.

Adenosine Triphosphate↗
PubMed1985

Membrane crystals of Ca2+-ATPase in sarcoplasmic reticulum of developing muscle.

The vanadate-induced crystallization of Ca2+-ATPase was analyzed on sarcoplasmic reticulum vesicles isolated between 10 and 28 days of development from pectoralis muscles of chicken. After exposure to Na3VO4 in a Ca2+-free medium, Ca2+-ATPase crystals begin to appear on portions of the surface of a few vesicles, isolated at 18 days of development. Thereafter, the number of vesicles containing Ca2+-ATPase crystals rapidly increases and after 1 week of postnatal development (28 days), it reaches the adult level of about 30% of the vesicle population. These observations are discussed with reference to the mechanism of Ca2+-ATPase crystallization and the regulation of sarcoplasmic reticulum biosynthesis.

Animals↗
PubMed1984

Membrane crystals of Ca2+-ATPase in sarcoplasmic reticulum of fast and slow skeletal and cardiac muscles.

Crystalline arrays of Ca2+ transport ATPase develop in sarcoplasmic reticulum membranes after treatment with Na3VO4 in a calcium-free medium [ Dux , L. and Martonosi , A. (1983) J. Biol. Chem. 258, 2599-2603]. The proportion of vesicles containing Ca2+-ATPase crystals in microsome preparations isolated from rat muscle of different fiber types (semimembranosus, levator ani, extensor digitorum longus, diaphragm, soleus, and heart) correlates well with the Ca2+-ATPase content and Ca2+-modulated ATPase activity. This implies that the concentration of Ca2+-ATPase in sarcoplasmic reticulum membranes of fast and slow skeletal or cardiac muscles differs only slightly, and the low Ca2+ transport activity of 'sarcoplasmic reticulum' preparations isolated from slow-twitch skeletal and cardiac muscles is due to the presence of large amount of non-sarcoplasmic-reticulum membrane elements. This is in accord with the relatively small differences in the density of 8.5-nm intramembranous particles seen by freeze-etch electron microscopy in sarcoplasmic reticulum of red and white muscles. The dimensions of the Ca2+-ATPase crystal lattice are similar in sarcoplasmic reticulum membranes of different fiber types; therefore if structural differences exist between 'isoenzymes' of Ca2+-ATPase, these are not reflected in the crystal-lattice.

Animals↗
PubMed1984

Structure of the vanadate-induced crystals of sarcoplasmic reticulum Ca2+-ATPase.

The projected structure of the vanadate-induced crystalline aggregates of Ca2+-ATPase molecules in isolated sarcoplasmic reticulum membranes has been determined. The molecules form tubular crystals with an oblique surface lattice having cell dimensions a = 65.9 A, b = 114.4 A and gamma = 77.9 degrees. The space group is P2. The crystalline tubules are formed through lateral aggregation of chains made up of dimers of Ca2+-ATPase molecules.

Calcium-Transporting ATPases↗
PubMed1984

Crystallization of intramembrane particles in rabbit sarcoplasmic reticulum vesicles by vanadate.

Sarcoplasmic reticulum (SR) membranes isolated from rabbit skeletal muscle appear in freeze-fracture as 0.15-0.2 micron vesicles. The concave fracture surface (P-face) contains a dense population of 8.5 nm particles that were previously identified as the Ca2+-transport ATPase. The convex surface (E-face) is mostly smooth, displaying an occasional particle but no complementary arrays of pits. Incubation of the vesicles at 4 degrees C in calcium-free solutions containing 5 mM Na3VO4 induces the formation of two-dimensional crystalline arrays of the Ca2+, Mg2+-ATPase, accompanied by structural changes visible by freeze-etch electron microscopy. Most vesicles elongate into tubules 60-80 nm in diameter and the 8.5 nm intramembrane particles of the P-face become regularly organized into parallel ridges. The ridges are coiled around the tubules in right-handed helices, oriented at 50-60 degrees angle to the long axis of the tubules. The particles repeat along the rows at about 5.5 nm and the rows repeat at 10.5-11.0. Occasionally the ridges seem to break up into 8.5 nm particles. Parallel furrows are visible on the (convex) E-face of the tubules. In high resolution replicas, the furrows are resolved into rows of pits that are complementary images of the ridges. Deep etching and rotary shadowing reveal oblique crests on the protoplasmic surface, consisting of dimeric particles close to 8.5 X 5.5 nm in size, in which each monomer can frequently be resolved into two structural domains. These data suggest that vanadate induces a conformational change in the Ca2+-transport ATPase, with crystallization of the intramembrane particles.

Animals↗
PubMed1984

Effect of Na3VO4 and membrane potential on the structure of sarcoplasmic reticulum membrane.

Two-dimensional crystalline arrays of Ca2+-ATPase molecules develop after treatment of sarcoplasmic reticulum vesicles with Na3VO4 in a Ca2+-free medium. The influence of membrane potential upon the rate of crystallization was studied by ion substitution using oxonol VI and 3,3'-diethyl-2,2'-thiadicarbocyanine (Di-S-C2(5] to monitor inside positive or inside negative membrane potentials, respectively. Positive transmembrane potential accelerates the rate of crystallization of Ca2+-ATPase, while negative potential disrupts preformed Ca2+-ATPase crystals, suggesting an influence of transmembrane potential upon the conformation of Ca2+-ATPase.

Animals↗
PubMed1984

The blood-brain barrier in hypoxia: ultrastructural aspects and adenylate cyclase activity of brain capillaries.

The ultrastructure of brain microvessels, their permeability to serum albumin, the activities of some endothelial enzymes and the effect of histamine were investigated in rats after a prolonged hypobaric-hypoxic treatment. After prolonged hypoxia, the permeation of serum albumin into endothelial cells increased together with the number of pinocytotic vesicles of the endothelium. Intracarotid histamine stimulated this process even further, and its effect was mediated by H2-histamine receptors. After hypoxia the specific activity of capillary alkaline phosphatase and gamma-glutamyl transpeptidase remained unchanged, while that of adenylate cyclase was greatly increased. Histamine did not modify the structure of tight junctions of isolated capillaries of normoxic animals. Both hypoxia- and histamine-induced modification of the brain microvessels were accompanied by an increase of pinocytosis, which may be stimulated by the activation of capillary adenylate cyclase.

Animals↗
PubMed1983

The regulation of ATPase-ATPase interactions in sarcoplasmic reticulum membrane. I. The effects of Ca2+, ATP, and inorganic phosphate.

Two-dimensional crystalline arrays of Ca2+-ATPase molecules develop after treatment of sarcoplasmic reticulum vesicles with Na3VO4 in calcium-free medium (Dux, L., and Martonosi, A. (1983) J. Biol. Chem. 258, 2599-2603). The formation of Ca2+-ATPase crystals is inhibited by Ca2+ (2 microM), or ATP (5 mM), but not by ADP, 5'-adenylylimidodiphosphate, or adenylylmethylenediphosphonate. ATPase crystals did not form at 37 degrees C and exposure of preformed crystals to 37 degrees C for 1 h caused the disappearance of crystal lattice. Inorganic orthophosphate (1 mM at pH 6.0) promoted the formation of a distinct crystal form of Ca2+-ATPase, which was different from that produced by Na3VO4. These observations indicate that Ca2+, ATP, inorganic phosphate, pH, and temperature influence the interactions between ATPase molecules in the sarcoplasmic reticulum membrane.

Adenosine Triphosphate↗
PubMed1983

The regulation of ATPase-ATPase interactions in sarcoplasmic reticulum membrane. II. The influence of membrane potential.

Na3VO4 promotes the crystallization of Ca2+-ATPase in sarcoplasmic reticulum vesicles. The rate of vanadate-induced crystallization is dramatically increased by inside positive membrane potential generated through ion substitution. Negative potential caused the transient disruption of preformed Ca2+-ATPase crystals, followed by slower reappearance of the lattice after the potential was dissipated. We propose that positive transmembrane potential alters the conformation of the Ca2+-ATPase molecules in a manner that favors ATPase-ATPase interactions, while negative potential would have the opposite effect. Changes in enzyme conformation caused by potential changes during the contraction-relaxation cycle could regulate ATPase interactions in a similar manner in vivo, with effects upon the Ca2+ transport activity and permeability of the sarcoplasmic reticulum.

Animals↗
PubMed1983

Ca2+-ATPase membrane crystals in sarcoplasmic reticulum. The effect of trypsin digestion.

Vanadate induces the formation of two-dimensional crystalline arrays of Ca2+-ATPase molecules in sarcoplasmic reticulum. The Ca2+-ATPase membrane crystals are evenly distributed among the terminal cisternae and longitudinal tubules of sarcoplasmic reticulum, but very few crystals were observed in the T tubules. Tryptic cleavage of the Ca2+ transport ATPase into two major fragments (A and B) did not interfere with the vanadate-induced formation of membrane crystals. The ability of Ca2+-ATPase to crystallize was lost after further cleavage of the A fragment into the A1 and A2 subfragments that is known to be accompanied by loss of Ca2+ uptake. Vanadate (0.1-5 mM) inhibited the secondary cleavage of Ca2+-ATPase by trypsin suggesting that the susceptibility of the tryptic cleavage sites is influenced either by the conformation of the enzyme or by the formation of ATPase crystals.

Animals↗
PubMed1983

Membrane crystals of Ca2+-ATPase in sarcoplasmic reticulum of normal and dystrophic muscle.

Two-dimensional crystalline arrays of the Ca2+ transport ATPase develop after treatment of sarcoplasmic reticulum vesicles with Na3VO4. The dimensions of the crystal lattice are similar in sarcoplasmic reticulum membranes isolated from normal and genetically dystrophic human, mouse, and chicken muscles. These observations indicate similar requirements for ATPase-ATPase interactions in sarcoplasmic reticulum of normal and dystrophic muscles and lessen the likelihood of a molecular defect of the Ca2+ pump in the various forms of genetic muscular dystrophies.

Animals↗
PubMed1982

Histamine-stimulated prostaglandin synthesis in rat brain microvessels.

The histamine-sensitivity of prostacyclin and prostaglandin synthesis was investigated in isolated brain microvessels prepared from normal and hypoxic exercised rats. 10(-4) M histamine stimulated the in vitro synthesis of all components of arachidonate cascade. The chronic hypoxic exercise also resulted in an enhanced production of each fraction. Hypoxia and histamine showed an additive effect in the synthesis of PGE2 only. The possible molecular mechanism induced by hypoxia and histamine is discussed.

Animals↗
PubMed1982

Further data on the androgenic dependency of the skeletal musculature: the effect of prepubertal castration on the structural development of the skeletal muscles.

The effect of prepubertal castration was investigated in the soleus, semimembranosus and levator ani muscles of rat, using light and electronmicroscopic morphometric methods. After castration the semimembranosus and the levator ani muscles showed significant morphometrical alterations. The weight of the muscles diminished, the diameter of the white fibers decreased. The ultrastructure of these muscles showed a well expressed myofibrillar atrophy. The changes in the semimembranosus muscle were less severe. The slow oxidative soleus muscle did not show any similar alterations. The changes in the levator ani and semimembranosus muscles could be prevented or moderated by testosterone substitution.

Animals↗
PubMed1981

The value of simple lipid stains for typing skeletal muscle fibres.

Skeletal muscle fibre types can be distinguished rapidly with simple lipid stains. Comparative studies showed that Sudan Black B is superior to Oil Red O for this purpose and that optimum staining is obtained using unfixed section or sections fixed in calcium-glutaraldehyde. Factors that possibly influence the staining reaction, such as freeze-thawing, are considered. The stained lipids were identified by thin layer chromatography.

Animals↗