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Biomedical subjects

C F Louis

Publications and source records attributed to C F Louis.

At least 109 records · Page 6Linked to original sources
PubMed1985

Comparison of crystalloid and sanguineous cardioplegic solutions in the dog.

Myocardial protection provided by 2 types of cold cardioplegic solution and by cold saline solution was compared experimentally in dogs on cardiopulmonary bypass. Techniques and solutions used simulated clinical conditions. Serial biopsies of myocardium were assayed for adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate. Maintenance and recovery of each phosphate was calculated as a percentage of the prebypass value for each type of solution; these values were used to compare the myocardial protection afforded by the 3 solutions. A difference in these values was not observed between the 2 types of cardioplegic solution; both values were greater than for the control solution, which may indicate improved myocardial protection with cardioplegic arrest.

Adenosine Diphosphate↗
PubMed1985

Porcine malignant hyperthermia susceptibility: erythrocytic osmotic fragility.

Erythrocyte osmotic fragility was determined in 27 Pietrain swine which were susceptible to malignant hyperthermia (MH), 29 Yorkshire swine which were resistant to MH (controls), and 50 crossbred swine (Pietrain x Yorkshire), half of which were MH susceptible. Halothane challenge tests and blood creatine kinase activity were used as criteria for determining MH susceptibility. Mean values for osmotic fragility of erythrocytes in concentrations of NaCl between 60 and 120 mM were significantly different for the 3 groups (P less than 0.001). Hemolysis (50%) of erythrocytes occurred at NaCl concentrations of 90 mM for Pietrains, 85 mM for crossbreds, and 78 mM for controls. Increased fragility values occurred in 96% of the Pietrains, 3% of the controls, and 42% of crossbred swine that were halothane test-positive, and 58% of halothane test-negative crossbreds (P less than 0.05). The mean time of onset of signs of MH in response to halothane challenge testing was twice as long in the crossbreds as in Pietrains (P less than 0.01). Reticulocyte counts were moderately high in blood samples from both the Pietrains (P less than 0.001) and the crossbreds (P less than 0.05). Of the swine which were tested for erythrocyte selenium-dependent glutathione peroxidase activity, values were within acceptable laboratory limits in 18 of 20 Pietrains, 14 of 14 halothane test-negative crossbreds, and 8 of 8 halothane test-positive crossbreds. In 2 of 20 Pietrains, a 35% deficiency of this enzyme was found. Heinz bodies were not detected in erythrocytes examined from 21 Pietrains, 20 crossbred swine (8 halothane test positives), and 12 controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

NAD: guanidino group specific mono ADP-ribosyltransferase activity in skeletal muscle.

The sarcoplasmic reticulum and glycogen pellet derived from rabbit skeletal muscle and the sarcolemma and sarcoplasmic reticulum from pig skeletal muscle contains NAD:dependent mono ADP-ribosyltransferase activity toward the guanidine analog, P- nitrobenzylidine aminoguanidine. No or little activity could be found in the sarcolemma or sarcoplasmic reticulum derived from canine cardiac muscle. Seventy percent of activity extracted from rabbit skeletal muscle is localized in the sarcoplasmic reticulum. The enzyme has a pH optimum of 7.4, and KM of 0.5 mM and 0.35 mM for NAD and p-nitro benzylidine aminoguanidine, respectively. Inorganic phosphate, KCl, and guanidine derivatives inhibit the reaction. Incubation of the sarcoplasmic reticulum or glycogen pellet with (adenylate-32P) NAD or [adenosine-14C(U)]-labeled NAD results in the incorporation of radioactivity into proteins. A large number of proteins are labeled in the sarcoplasmic reticulum fraction. The major labeled band in the glycogen pellet corresponds to a protein of molecular weight of 83 K.

ADP Ribose Transferases↗
PubMed1984

Cellulose digestion by domestic turkeys fed low or high fiber diets.

To determine whether dietary preconditioning might improve fibrolysis in turkeys, Wrolstad Medium white hens were fed either a high (16.13%, HF) or low (2.80%, LF) fiber diet for 6-60 weeks. The substrate to test for cellulolysis, [14C]cellulose, was introduced into the gizzard per os or into one cecum via a cannulated fistula. Immediately after [14C]cellulose introduction, turkeys were placed in an airtight chamber (0.3 m3) from which exhaled CO2 was collected and analyzed for 14CO2. An average of 10.4% of the 14C was recovered in CO2 from turkeys fed the HF diet, and only 2.9% was recovered from the LF-fed birds that were orally dosed. In turkeys dosed via cecal cannula, recoveries averaged 15.4 and 2.9% for HF- and LF- fed birds, respectively. Recoveries were 7.0 and 1.4% in HF- and LF-fed turkeys that were cecectomized. Preconditioning to an HF diet does appear to improve cellulolysis.

Animals↗
PubMed1983

Calcium accumulation in human and sheep erythrocytes that is induced by Escherichia coli hemolysin.

The membrane permeability of both human and sheep erythrocytes is modified by an Escherichia coli-produced extracellular hemolysin. Alterations in membrane permeability were determined by measuring changes in the extracellular concentration of radiolabeled compounds that had been added to a 30-35% erythrocyte suspension. During the pre-lytic period, the E. coli hemolysin promotes calcium accumulation by both human and sheep erythrocytes. The concentration of calcium associated with the cells rises to a level that is approximately 1.5 (sheep) to 3 (human) times higher than that in a comparable volume of extracellular solution. Hemolysin also causes a rapid depletion of the high intracellular potassium levels normally present in human erythrocytes. That neither inulin, sucrose nor phosphate is accumulated by hemolysin-treated erythrocytes indicates that hemolysin makes the membrane selectively permeable to cations.

Animals↗
PubMed1983

Inhibition of calmodulin-dependent and independent cardiac sarcoplasmic reticulum activities by R24571.

R24571 a derivative of the antimycotic miconazole, appears to be 5 to 8 times more potent than trifluoperazine in its ability to inhibit the calmodulin-dependent phosphorylation of cardiac sarcoplasmic reticulum vesicles. The cAMP-dependent protein kinase mediated phosphorylation of cardiac sarcoplasmic reticulum was not affected by R24571. Sarcoplasmic reticulum Ca-dependent ATPase phosphoprotein intermediate formation was inhibited by R24571 concentrations that were 20 to 30 times greater than those required to inhibit calmodulin-dependent phosphorylation. However, both Ca-dependent and independent ATPase activities, as well as calcium uptake, were inhibited by R24571 concentrations that were similar to, or less than, those concentrations required to inhibit calmodulin-dependent sarcoplasmic reticulum phosphorylation. These results indicate the caution that should be exercised in using this new compound in assessing the possible involvement of calmodulin in other membrane processes.

Adenosine Triphosphatases↗
PubMed1982

Factors that modify the molecular size of phospholamban, the 23,000-dalton cardiac sarcoplasmic reticulum phosphoprotein.

Phospholamban, a 23,000-dalton phosphoprotein present in cardiac muscle sarcoplasmic reticulum vesicles is quantitatively dissociated into three smaller sized phosphorylated components of 11,000, 15,000, and 20,000 daltons when sarcoplasmic reticulum, solubilized in 1% (w/v) sodium dodecyl sulfate and 1 mM MgCl2, is heated at 71 degrees C or greater for 2 min. This dissociation is inhibited by Mg2+ (50% at approximately 5 mM). The 23,000-dalton phosphoprotein reformed from the 11,000-, 15,000-, and 20,000-dalton phosphorylated components when phosphorylated sarcoplasmic reticulum that had been boiled in 1% sodium dodecyl sulfate and 1 MM MgCl2 was stored for 1 week at -70 degrees C. We propose that the 23,000-dalton phosphorylated protein is a trimer, composed of three subunits with molecular mass of 11,000, 8,000, and 4,000 daltons. In this model, only the 11,000-dalton subunit would be phosphorylated. The partial dissociation of the 23,000-dalton phosphorylated protein would result in the formation of the 19,000 (11,000 + 8,000)-dalton or the 15,000 (11,000 + 4,000)- dalton phosphorylated components. Full dissociation of the 23,000-dalton phosphorylated protein would result in the formation of the 11,000-dalton phosphorylated component.

Adenosine Triphosphatases↗
PubMed1982

Affinity labeling of calmodulin-binding components in canine cardiac sarcoplasmic reticulum.

Canine cardiac sarcoplasmic reticulum vesicles have been labeled by covalent cross-linking to membrane-bound 125I-calmodulin with dithiobis(succinimidyl propionate). Electrophoretic analysis in sodium dodecyl sulfate demonstrated a 125I-containing major product of Mr = 40,000, and a minor component of Mr = 120,000. This latter component probably represents a 1:1 complex between the 100,000-dalton Ca2+-ATPase protein and 125I-calmodulin. When cross-linked samples, solubilized in sodium dodecyl sulfate, were boiled for 2 min, the radioactivity associated with the 40,000-dalton component decreased while that associated with components of 26,000 and 28,000 daltons increased. When these boiled samples were stored at -70 degrees C for 1 week, the radioactivity associated with the 26,000- and 28,000-dalton components decreased whereas that associated with the 40,000-dalton component was increased. This suggests that the 40,000-dalton component represents a 1:1 cross-link between the 23,000-dalton form of phospholamban and 125I-calmodulin. The 26,000- and 28,000-dalton cross-linked components probably represent 1:1 cross-links between 125I-calmodulin and the 8,000- and 11,000-dalton subunits, respectively, of phospholamban. A 32P-containing, 40,000-dalton component was formed when dithiobis(succinimidyl propionate) was added to sarcoplasmic reticulum vesicles, phosphorylated in the presence of [gamma-32P]ATP and 3 microM calmodulin. This confirms that the 40,000-dalton affinity-labeled component is a 1:1 cross-link between phospholamban and calmodulin. We propose that phospholamban is the endogenous receptor for calmodulin in cardiac sarcoplasmic reticulum membranes. However, it is unlikely that phospholamban is the endogenous calmodulin-dependent protein kinase in this membrane.

Animals↗
PubMed1982

Fatty acid effects on calcium influx and efflux in sarcoplasmic reticulum vesicles from rabbit skeletal muscle.

Low concentrations of fatty acids inhibited initial Ca uptake by sarcoplasmic reticulum vesicles, the extent of inhibition varying with chain length and unsaturation in a series of C14-C20 fatty acids. Oleic acid was a more potent inhibitor of initial Ca uptake than stearic acid at 25 degrees C, whereas at 5 degrees C there was less difference between the inhibitory effects of low concentrations of these fatty acids. When the fatty acids were added later, during the phase of spontaneous Ca release that follow Ca uptake in reactions carried out at 25 degrees C 1-4 microM oleic and stearic acids caused Ca content to increase. This effect was due to marked inhibition of Ca efflux and slight stimulation of Ca influx. At concentrations of greater than 4 microM, both fatty acids inhibited the Ca influx that occurs during spontaneous Ca release; in the case of oleic acid, this inhibition resembled that of initial Ca uptake at 5 degrees C. The different effects of fatty acids at various times during Ca uptake reactions may be explained in part if alterations in the physical state of the membranes occur during the transition from the phase of initial Ca uptake to that of spontaneous Ca release.

Animals↗
PubMed1981

The structure and organization of dopamine-beta-hydroxylase in the chromaffin granule membrane.

Chromaffin granules have been purified from bovine adrenal medullae. The granule membranes have been cross-linked with the disulphide-bridged bifunctional imido ester, dimethyl-3,3'-dithiobissuccinimidylpropionate hydrochloride. Analysis of the cross-linked proteins by electrophoresis on agarose/acrylamide gels revealed components of M(r) 300 000 and 150 000. Further analysis of samples by electrophoresis in a second dimension containing a reducing agent revealed the monomeric species from which the cross-linked polypeptides were formed. The major component in the second dimension exhibited a molecular weight of approx. 80 000 and could be identified with dopamine-beta-hydroxylase (3,4-dihydroxyphenylethylamine ascorbate:oxygen oxidoreductase (beta-hydroxylating), EC 1.14.17.1). It is proposed that dopamine-beta-hydroxylase in the intact granule membrane is arranged as a tetramer consisting of two disulphide-bridged dimers of the 80 000 subunit in close apposition. This structural arrangement of the membrane-bound form of dopamine-beta-hydroxylase is identical with that previously proposed for the soluble, intra-granular form of the enzyme.

Adrenal Medulla↗
PubMed1980

Time-dependent changes of calcium influx and efflux rates in rabbit skeletal muscle sarcoplasmic reticulum.

Unfractionated and low buoyant density sarcoplasmic reticulum vesicles released calcium spontaneously after ATP- or acetyl phosphate-supported calcium uptake when internal Ca2+ was stabilized by the use of 50 mM phosphate as calcium-precipitating anion. This spontaneous calcium release could not be attributed to falling Ca2+ concentration outside the vesicles (Ca02+), substrate depletion, ADP accumulation, nonspecific membrane deterioration of the attainment of a high vesicular calcium content. Instead, spontaneous calcium release was directly proportional to Ca02+ at the time that calcium content was maximal. A causal relationship between high Ca02+ and spontaneous calcium release was suggested by the finding that elevation of Ca02+ from less than 1 microM to 3--5 microM increased the rate and extent of calcium release. The spontaneous calcium release was due both to acceleration of calcium efflux and slowing of calcium influx that was not accompanied by a significant change in the rate of ATP hydrolysis. Neither reversal of the transmembrane KCl gradient nor incubation with cation and proton ionophores abolished the spontaneous calcium release. The persistence of calcium release under conditions where the membrane was permeable to both anions and cations makes it unlikely that this phenomenon is due to a changing transmembrane potential. The similarity between the Ca2+ dependence of spontaneous calcium release and of calcium uptake, along with other similarities between these processes, suggest that calcium release is mediated by the calcium pump in these membranes.

Acetates↗
PubMed1980

The modification of the unidirectional calcium fluxes of sarcoplasmic reticulum vesicles by monovlent cation ionophroes.

Calcium uptake by rabbit skeletal muscle sarcoplasmic reticulum vesicles in phosphate-containing media exhibits time-dependent changes that arise from changing rates of calcium influx and efflux. The monovalent cation ionophore gramicidin, added before the start of the calcium uptake reaction, delayed the spontaneous calcium release that normally occurred after approx. 6 min in such reactions; the rate of calcium efflux was inhibited while calcium influx was little affected. Under these conditions, Ca2+-activated ATPase activity could remain unaltered. Gramicidin stimulated calcium uptake irrespective of the presence of a K+ gradient across the vesicle membrane. Valinomycin stimulated calcium uptake in a manner similar to that for gramicidin even in an NaCl-containing medium lacking potassium. Thus, dissipation of a transmembrane K+ gradient is unlikely to account for the effects of these ionophores on the spontaneous changes in calcium flux rates. Addition of gramicidin to partially calcium-filled vesicles inhibited the phase of spontaneous calcium reuptake because both calcium influx and efflux wre inhibited. Addition of gramicidin to partially calcium-filled vesicles in the presence of a water-soluble protein, such as bovine serum albumin, creatine kinase or pyruvate kinase, markedly stimulated calcium uptake. This stimulatory effect was due primarily to inhibition of calcium efflux, calcium influx being minimally influenced by the ionophore. After cleavage of the 100,000 dalton ATPase to 50,000 dalton fragments, which was not associated with changes in Ca2+-activated ATPase activity or initial calcium uptake rate, gramicidin increased rather than decreased calcium content when added to vesicles after the initial maximum in calcium content. Thus, the ability of monovalent cation ionophores to block calcium efflux from calcium-filled vesicles may reflect their interaction with a portion of the Ca2+-activated ATPase protein.

Animals↗
PubMed1980

A comparison of vesicles derived from terminal cisternae and longitudinal tubules of sarcoplasmic reticulum isolated from rabbit skeletal muscle.

Sarcoplasmic reticulum vesicles were separated into heavy (derived from terminal cisternae) and light (derived from longitudinal tubules) fractions, according to Meissner [Biochim. Biophys. Acta, 389, 51-68 (1975)]. The similar Ca2+ sensitivities of phosphoprotein formation, ATPase activity and calcium uptake, and the similar phosphoprotein turnover rates (ATPase/phosphoprotein formation) of both fractions indicate that the same ATPase enzyme is present in the terminal cisternae and longitudinal sarcoplaxmic reticulum. The higher V for Ca2+-activated ATPase activity and calcium uptake in the light fraction correlated with the higher concentration of ATPase enzyme per mg of membrane protein in this fraction. In both the presence and absence of calcium-precipitating anions, the light fraction stored more calcium than the heavy. The Ca2+ dependence of calcium release after addition of EGTA appeared similar in both fractions, but the rate of calcium release was more rapid in the light fraction. These findings suggest that calcium release may occur more rapidly from longitudinal than terminal cisternae portions of the sarcoplasmic reticulum and that calcium release, like calcium uptake, may be mediated by the ATPase enzyme in the sarcoplasmic reticulum membrane. Although the activation energies for Ca2+-activated ATPase activity above and below the transition temperature were significantly different for the heavy and light fractions, their transition temperatures were similar. Partial purification of the ATpase enzyme by deoxycholate treatment modified the activation energies of the light but not the heavy fraction and caused the activation energies to become similar. The phosphoprotein levels of heavy and light vesicles did not become similar after deoxycholate treatment, although gel electrophoretograms indicated both samples contained > 90% ATPase protein. These results indicate the protein-lipid associations in these two fractions may be different.

Adenosine Triphosphatases↗
PubMed1980

Ca2+-dependent oscillations in the calcium content of cardiac sarcoplasmic reticulum vesicles.

Sarcoplasmic reticulum (SR) vesicles contain an ATP-dependent calcium pump that transports Ca2+ from the external medium into the vesicles against a large Ca2+ gradient. In addition, these vesicles can release Ca2+ by a process that shares many of the characteristics of the calcium pump, suggesting that the calcium pump ATPase protein also participates in calcium efflux. The appearance of a calcium release phase in cardiac SR vesicles is seen in the presence of high external Ca2+. Although this dependence on high Ca2+ resembles that of "aftercontractions" in intact heart muscle, the periodicity of the oscillations in calcium content of cardiac SR vesicles is much slower than that of aftercontractions in the intact myocardium.

Animals↗