Oxygen as an inductor of divalent cation permeability through biological and model lipid membranes.

The action of lipid hydroperoxides (LH), which are primary products of lipid oxidation, on cation permeability through bilayer lipid membranes (BLM) and sarcoplasmic reticulum (SR) membranes was investigated. Bilayer lipid membranes prepared from unoxidized phosphatidyl choline (PC) plus cholesterol or from total phospholipids extracted from SR vesicles possessed low cation permeability. Lipid oxidation induced by Fe2+-ascorbate led to a sharp increase in the calcium current through the BLM and to a considerable increase in the concentration of LH products.

The cardiac relaxing system. Its nature, calcium ion capacity, and influence of hydrogen and magnesium ions on initial velocity of calcium binding.

The functional and structural properties of Ca2+ ATPases isolated from heart and skeletal muscles were compared. The pH and Ca2+ dependences of the activities as well as amino acid and phospholipid composition of the enzymes are similar. On the other hand, specific activities of Ca2+ ATPases and their abilities to pump calcium in the reconstituted proteoliposomes differ.

Percutaneous osteoclasp fixation of akin osteotomy: an alternative fixation technique.

An alternative method of fixating the Akin osteotomy which accomplishes compression osteosynthesis, maintenance of alignment, early ambulation in a rigid sole postoperative shoe, and the added advantage of early, complete removal of the fixation device without anesthesia is presented.

The role of a noxious taste in determining food intake in the rat.

Adult female rats were given access to cornstarch, fat, and 2 cups of casein ad lib. Sucrose octaacetate was added to one or both casein cups in concentrations of 0, 0.1, or 2.

Energy metabolism and ion fluxes across cardiac membranes.

The possible role of the intracellular creatine kinase system in energy transport and in the metabolic control of ion fluxes across the cardiac cell membranes has been studied. The experimental data reported indicate that creatine kinases bound to the sarcolemmal membrane and to the membrane of sarcoplasmic reticulum are coupled to Na+, K+-ATPase and Ca2+-ATPase, respectively, and ensure rapid rephosphorylation of ADP produced in the ATPase reactions, maintaining a high and constant ATP:ADP ratio near the active centers of ATPases. The ability of creatine phosphate to increase the rate of activator calcium entry across the surface membrane into cardiac cells has been experimentally demonstrated.

Partial characterization of protein kinase-catalyzed phosphorylation of low molecular weight proteins in purified preparations of pigeon heart sarcolemma and sarcoplasmic reticulum.

Pigeon heart microsomes contain three minor size protein kinase substrates of minimal molecular weights of 22 000, 15 000, and 11500, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When the microsomes were partially loaded with calcium oxalate and subjected to rate zonal and isopycnic centrifugations in sucrose density gradient columns, the 22 000 and the 15 000 dalton proteins settled in the heaviest fraction, which was composed mainly of vesicles of sarcoplasmic reticular membranes; the 11 500 dalton protein was concentrated in the lightest fractions, which consisted chiefly of vesicles of sarcolemmal origin. During incubation of the membrane fractions with Mg [gamma-32P]ATP significant amounts of 32P were incorporated into all these proteins.

The effect of mechanical stretching of the myosin rod component (fragment LMMMM S-2) on the ATPase activity of myosin.

The binding of myosin to nylon fiber gives immobilized myosin with a considerable ATPase activity. Treatment of immobilized enzyme with papain results in the entire ATPase activity (known to be concentrated in myosin heads, (fragment HMM S-1)) being replaced from the fiber into the solution; this means that myosin is chemically bound to the fiber via its rod part (fragment LMM+HMM S-2). When nylon fiber is mechanically stretched, the ATPase activity of myosin attached to it sharply decreases; after relaxation of the fiber the enzymatic activity returns to the initial level.

The role of creatine phosphokinase in supplying energy for the calcium pump system of heart sarcoplasmic reticulum.

An investigation of isolated and purified heart sarcoplasmic reticulum performed in the current study indicates the presence of significant creatine phosphokinase (CPK) activity in this preparation. The localization of CPK on the membrane of sarcoplasmic reticulum has been revealed also by an electron microscopic histochemical method. Under the conditions of the Ca(2+)-ATPase reaction in the presence of creatine phosphate, the release of creatine into the reaction medium is observed, the rate of the latter process being dependent on the MgATP concentration in accordance with the kinetic parameters of the Ca2+-ATPase reaction.

Protein malnutrition induced during gestation: its effect on pup development and maternal behavior.

Repeated time-lapse photographic observations were used to examine the ontogeny of behavioral development in prenatally malnourished rat pups following birth. Pups born to dams receiving a low protein diet (7% casein by weight) were fostered at birth to well-nourished dams and behavioral observations were made at 4-day intervals. Dams nursing gestationally malnourished pups were observed to spend more time in the nesting area with their pups towards the end of lactation.

Early protein malnutrition in the rat: behavioral changes during rehabilitation.

Behavioral development was studied in 2 groups of rats during the postweaning period. Pups were selected from litters nursed by dams fed either a standard protein (25% casein by weight) or a low protein diet (12% casein) during lactation. Two pups from each litter were housed together and fed the control diet throughout rehabilitation.

Determination and functional significance of low affinity nucleotide sites of Ca2+ + Mg2+ -dependent ATPase of sarcoplasmic reticulum.

The protective effect of ATP, ADP and GTP against the inactivation of Ca2+ + Mg2+ -dependent ATPase by the thiol reagent NBD-chloride is used to calculate the apparent dissociation constants (K'D) of nucleotide enzyme complexes on the basis of a simple kinetic model. The K'D-values of the complexes with Mg-ATP (80 micrometer) and Mg-GTP (500 micrometer) are found to be rather close to their Km-values in the high concentration range supporting maximum activity. The requirement of the occupancy of the low affinity site by Mg ATP for a high rate of the Ca2+ transport system is explained in terms of the flip-flop mechanism established earlier for the analogous Na+ + K+-transporting ATPase system.

Isolation of calcium pump system and purification of calcium ion-dependent ATPase from heart muscle.

The procedure for the isolation of the highly active fraction of sarcoplasmic reticulum from pigeon and dog hearts is described. The method is based on the partial loading of heart microsomes with calcium and oxalate ions and the precipitation of loaded vesicles in sucrose and potassium chloride concentration gradients. Preparations obtained possess high activity of Ca2+-dependent ATPase and are also able to accumulate up to 10 mumol Ca2+ per mg protein.