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PubMed1994

Retrograde warm blood cardioplegia preserves hypertrophied myocardium: a clinical study.

The ability of retrograde warm blood cardioplegia to preserve hypertrophied myocardium remains controversial. This two-part study was undertaken to address this question in patients subjected to aortic valve replacement for calcified aortic valve stenosis complicated with echocardiographically defined left ventricular hypertrophy. Part 1 was designed to assess the intraoperative patterns of myocardial oxidative metabolism in 20 patients in whom the severity of left ventricular hypertrophy was reflected by a mean (+/- standard error of the mean) myocardial mass index of 213 +/- 15 g/m2. After antegrade arrest, warm blood cardioplegia was continuously given through the coronary sinus at a flow rate of 200 +/- 5 mL/min. The use of a low-dilution cardioplegia delivery technique enabled us to keep hematocrit at 25.6% +/- 0.9% and the core temperature was allowed to drift to 32.7 +/- 0.2 degrees C. At the end of the arrest period, blood samples were simultaneously taken from inflow (coronary sinus catheter) and outflow (left coronary ostium) cardioplegia and assayed for blood gases, oxygen content and saturation and lactate. Part II was designed to compare the clinical outcomes of these 20 warm patients with those of 20 case-matched patients in whom a conventional hypothermic myocardial protection technique was used. The results of part I show that after an average arrest period of 72 +/- 4 minutes, the residual oxygen demand was still high as reflected by a percent oxygen extraction of 34.8% +/- 4.1%. This demand, however, was adequately met by the supply, as demonstrated by (1) the absence of transmyocardial acid production, (2) a negligible release (outflow minus inflow) of lactate (0.28 +/- 0.1 mmol/L), and (3) a high residual oxygen saturation (65.7% +/- 3.8%) in outflow cardioplegia. The results of part II show that the clinical outcomes of warm patients were overall good and not different from those of the cold group. We conclude that retrograde warm blood cardioplegia can adequately preserve hypertrophied myocardium by keeping its metabolism predominantly aerobic during aortic cross-clamping provided that measures are taken to optimize the determinants of the oxygen demand/supply ratio throughout. These measures include avoidance of left ventricular distention, immediate ablation of any recurring activity during arrest, maintenance of high retrograde flow rates, limitation of hemodilution, and uninterrupted mode of cardioplegia delivery.

Acids↗
PubMed1994

Lack of cardioplegia uniformity in clinical myocardial preservation.

Advances in myocardial preservation have led to improved patient survival after open heart operations. However, few studies have detailed the nature of national or regional patterns of cardioplegia use. To determine the regional pattern, all open heart surgery programs in Missouri were surveyed. During 1 year, it was found that cardioplegia was administered to 8,382 patients by 61 cardiothoracic surgeons at ten academic affiliated hospitals and 16 nonteaching hospitals. All cardioplegic solutions were hospital produced. Of 13 crystalloid solutions, 11 differed from one another and eight were intracellular formulations. Of 28 multidose blood-based cardioplegic solutions, there were 23 different mixtures. Most crystalloid (69%) and blood-based (89%) solutions differed substantially from commonly reported formulations. The incidences of the various additives to crystalloid solutions were as follows: bicarbonate, 92%; glucose, 69%; lidocaine, 54%; mannitol, 46%; magnesium, 31%; calcium, 23%; methylprednisolone, 15%; heparin, 8%; and acetate, 8%. Of the common blood-based cardioplegic solution additives, the following incidences were observed: glucose, 79%; bicarbonate, 43%; trishydroxyaminomethane, 36%; acetate, 29%; magnesium, 29%; procaine (or lidocaine), 25%; citrate-phosphate-dextrose, 18%; mannitol/albumin, 14%; nitroglycerin, 11%; glutamate/aspartate, 11%; calcium, 7%; insulin, 3%; and methylprednisolone, 3%. No calcium channel blocker or high-energy phosphate additives were reported. We conclude that many different cardioplegic admixtures that have not been tested experimentally are used routinely in clinical practice, presumably with acceptable results. Because the salutary effects of induced cardiac arrest and hypothermia may mask suboptimal solutions, further study of customized cardioplegia should be considered, particularly with regard to high-risk patients.

Blood↗
PubMed1994

Lung preservation with Euro-Collins, University of Wisconsin, Wallwork, and low-potassium-dextran solution. Université++ Paris-Sud Lung Transplant Group.

Using isolated rat lungs, we compared prevention of ischemia-reperfusion injury provided by flushing the lungs with modified Euro-Collins solution (EC), University of Wisconsin solution (UW), low-potassium-dextran solution (LPD), or Wallwork solution (WA). After 4 hours' and 6 hours' cold ischemia, reperfusion injury was assessed on the basis of changes in filtration coefficients (Kfc) and pressure-flow curves, characterized by the slope of the curves (incremental resistance) and the extrapolation of this slope to zero flow (pulmonary pressure intercept [Ppi]). After 4 hours, Kfc and Ppi were higher with EC than with UW, LPD, and WA, and the incremental resistance was higher with EC and UW. After 6 hours, Kfc and incremental resistance Ppi were higher with LPD than with WA. Because ischemia-reperfusion injury is associated with decreased endothelial synthesis of prostacyclin and nitric oxide, we tested whether the addition of prostacyclin or the nitric oxide precursor L-arginine to WA would improve preservation. The Kfc and Ppi were lower with both treatments. In conclusion, ischemia-reperfusion injury was best prevented by using WA. The favorable effect of prostacyclin or L-arginine emphasizes the role played by endothelial dysfunction in ischemia-reperfusion injury.

Adenosine↗
PubMed1994

Electrophysiologic consequences of hyperkalemic cardioplegia during surgical ischemia.

Myocardial protection strategies use cardioplegic solutions to reduce the injury induced by surgical ischemia and reperfusion. However, there is a high incidence of electrophysiologic abnormalities after cardioplegic arrest. A computerized epicardial mapping system in a porcine cardiopulmonary bypass model was used to measure the electrophysiologic consequences of different myocardial protection techniques. Both warm and cold, crystalloid and blood cardioplegic solutions were compared. The effects of hypothermia and prolonged cardiopulmonary bypass were examined in a control group that underwent a 2-hour period of hypothermia without cardioplegia or aortic cross-clamping, followed by 2 hours of normothermic reperfusion. Isochronous activation maps, unipolar electrograms, ventricular refractory periods, and pacing thresholds were measured before cardioplegic arrest and during reperfusion. Compared with the control group, crystalloid cardioplegia, but not blood cardioplegia, was accompanied by large changes in the pattern of ventricular activation and by persistent (> 2 hours) and significant slowing of the time required for complete ventricular activation. This was not the result of hypoxia. Moreover, the effective refractory period and the pacing threshold were unchanged by any cardioplegia. Our data suggest that crystalloid cardioplegia increases myocardial resistance to current flow leading to a derangement of electrical impulse propagation that may underlie arrhythmogenesis.

Animals↗
PubMed1994

Ischemic preconditioning improves preservation with crystalloid cardioplegia.

Ischemic preconditioning has not been investigated in a clinically relevant model of hypothermic multidose cardioplegia arrest. Using isolated rabbit hearts perfused on a Langendorff apparatus, ischemic preconditioning was investigated as an adjunct to crystalloid cardioplegia during a 2.5-hour ischemic period at 15 degrees C. After baseline functional data were obtained, ischemic preconditioning was induced with either 1 minute or 5 minutes of normothermic ischemia, followed by 5 minutes of reperfusion before the arrest period. Control hearts underwent no ischemic preconditioning. The control hearts exhibited a decrement in both the peak developed pressure and diastolic function, as measured by the slope of the diastolic pressure-volume relationship, of from 107 +/- 2 to 68 +/- 7 mm Hg (p < 0.005) and from 0.99 +/- 0.2 to 2.95 +/- 0.44 mm Hg/0.1 mL (p < 0.005), respectively. Hearts exposed to either 1 or 5 minutes of normothermic ischemia showed no significant change in the slope of the diastolic pressure-volume relationship. Hearts exposed to 1 or 5 minutes of normothermic ischemia also had a significant decrease in the peak developed pressure of from 107 +/- 6 to 92 +/- 2 mm Hg and from 102 +/- 3 to 85 +/- 4 mm Hg, respectively (p < 0.05). However, ischemic preconditioning brought about a significant improvement in the postischemic peak developed pressure, as opposed to that seen for the control hearts (p < 0.05). Creatine kinase washout was significantly higher in the control hearts only. High-energy phosphate levels, lactate levels, the percentage wet weight, and tissue creatine phosphate levels were not significantly different among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Analysis of self-association of bovine neurophysins by gel chromatography.

Analytical gel chromatography has been used to examine self-association of bovine neurophysins I and II under several sets of conditions. The data provide no evidence for associated species larger than the dimer. Association constants and Stokes radii of both monomer and dimer are very similar for both proteins in both 0.1 M KOAc, 0.16 M KCl and 0.1 M KPO4, 0.16 M KCl at pH 5.6 and 25 degrees C. The average values derived for the Stokes radii of the monomer and dimer under these conditions are 14.5 +/- 0.7 and 23.0 +/- 0.4 A, respectively. These results confirm the conclusion of Rholam and Nicolas [(1981) Biochemistry 20, 5837-5843] that the monomer and, to a lesser extent, the dimer are highly assymmetric. The Stokes radius of the monomer calculated by Rholam and Nicolas (op cit.) is approximately 30% larger than the value derived here. This discrepancy is probably the result of end-on penetration of the gel by elongated molecules [Y. Nozaki, N. M. Schechter, J. A. Reynolds, and C. Tanford (1976) Biochemistry 15, 3884-3890]. In contrast to Tellam and Winzor [(1980) Arch. Biochem. Biophys. 201, 20-24], it was found that neurophysin II does not exist solely as the dimer in 0.1 M KPO4, pH 5.6, although substitution of 0.1 M KPO4 for 0.1 M KOAc does increase the association constant by a factor of seven. Addition of 1.4 M LiCl at pH 8.1 also increases the association constant sevenfold, as well as increasing the Stokes radius of the monomer approximately 20%. The effects of ionic strength are consistent with the conclusion of Nicolas et al. [(1978) J. Biol. Chem 253, 2633-2639] that formation of the dimer depends upon hydrophobic bonding.

Animals↗
PubMed1987

An immediate and steep increase in ATP concentration in response to reduced turgor pressure in Escherichia coli B.

Osmotic treatment with sodium chloride of Escherichia coli B growing in the logarithmic phase induced an immediate increase in ATP concentration in response to increased concentrations of added solute in its growth medium in the first 10 min of the addition. After that, ATP concentration decreased gradually. Sodium arsenate and potassium fluoride almost abolished the ATP increase. The time course of the increase was quite different from that of cells treated with inhibitors of protein synthesis. The osmotic treatment did not decrease the viability of cells. In addition, there was no degradation of RNA by 5 min after sodium chloride addition, and, further, the lag time of ATP increase was extended by an inhibitor of nucleotide synthesis. These results indicated that a major fraction of the stress-increased ATP resulted from de novo synthesis, and that it was mainly dependent upon the reaction of substrate-level phosphorylation, which is regulated by turgor pressure.

Adenosine Triphosphate↗
PubMed1989

Inhibition of pyruvate carboxylase by sequestration of coenzyme A with sodium benzoate.

Pyruvate-dependent CO2 fixation by isolated mitochondria was strongly inhibited by sodium benzoate. Pyruvate carboxylase was identified as a site of inhibition by limiting flux measurements to assays of pyruvate carboxylase coupled with malate dehydrogenase. Benzoate reduced pyruvate-dependent incorporation of [14C]KHCO3 into malate and pyruvate-dependent malate accumulation by 74 and 72%, respectively. Aspartate-dependent malate accumulation was insensitive to benzoate, ruling out malate dehydrogenase as a site of action. Inhibition by benzoate was antagonized by glycine, which sharply accelerated conversion of benzoate to hippurate. Assays of coenzyme A and its acyl derivatives revealed inhibition to correlate with depletion of acetyl CoA and accumulation of benzoyl CoA. Depletion of acetyl CoA was sufficient to account for greater than 50% reduction in pyruvate carboxylase activity. Competition between acetyl CoA and benzoyl CoA for the activator site on pyruvate carboxylase was insignificant. Results support the interpretation that the observed inhibition of pyruvate carboxylase occurred primarily by depletion of the activator, acetyl CoA, through sequestration of coenzyme A during benzoate metabolism.

Acetyl Coenzyme A↗
PubMed1990

Characterization of tonoplast-enriched vesicles isolated by gradient density fractionation of suspension-cultured cells.

A tonoplast-enriched microsomal fraction was isolated from Catharanthus roseus cells. It was characterized by structural and functional criteria. This fraction presented a homogeneous size distribution as shown by quasi-elastic light scattering and a homogeneous density on self-generated gradients of Percoll. The mean diameter of the vesicles was estimated to be 0.30 micron and the buoyant density around 1.04 g/ml. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of its polypeptide pattern was in good agreement with the one obtained for tonoplast purified from isolated vacuoles. According to enzymatic assays and inhibition tests, this fraction possessed pyrophosphate and ATP-dependent proton pumps and very low contamination by submitochondrial particles, endoplasmic reticula and Golgi membranes. In light of our previous published results on tonoplast purified from isolated vacuoles, the very low extent of AMP hydrolysis by the microsomal fraction is interpreted as supplementary proof in favor of a tonoplast-enriched fraction.

Adenosine Triphosphatases↗
PubMed1992

Hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol by rat prostate microsomes: effects of antibodies and chemical inhibitors of cytochrome P450 enzymes.

The purpose of the present study was to test the hypothesis that rat prostate microsomes contain a single cytochrome P450 enzyme responsible for the conversion of 5 alpha-androstane-3 beta,17 beta-diol to a series of trihydroxylated products. The three major metabolites formed by in vitro incubation of 5 alpha-[3H]androstane-3 beta,17 beta-diol with rat prostate microsomes were apparently 5 alpha-androstane-3 beta,6 alpha,17 beta-triol, 5 alpha-androstane-3 beta,7 alpha,17 beta-triol, and 5 alpha-androstane-3 beta,7 beta,17 beta-triol, which were resolved and quantified by reverse-phase HPLC with a flow through radioactivity detector. The ratio of the three metabolites remained constant as a function of incubation time, microsomal protein concentration, ionic strength, and substrate concentration. The ratio of the three metabolites was dependent on pH, apparently because the hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol shifted from the 6 alpha- to the 7 alpha-position with increasing pH (6.8-8.0). The V(max) values were 380, 160, and 60 pmol/mg microsomal protein/min for the rate of 6 alpha-, 7 alpha-, and 7 beta-hydroxylation, respectively. Similar Km values (0.5-0.7 microM) were measured for enzymatic formation of all three metabolites, which suggests that formation of all three metabolites was catalyzed by a single, high-affinity enzyme. Testosterone, 5 alpha-dihydrotestosterone, and 5 alpha-androstane-3 alpha,17 beta-diol did not appreciably inhibit the hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol, suggesting that this enzyme exhibits a high degree of substrate specificity. Formation of all three metabolites was inhibited by antibody against rat liver NADPH-cytochrome P450 reductase (85%) and by a 9:1 mixture of carbon monoxide and oxygen (60%). Several chemical inhibitors of cytochrome P450 enzymes, especially the antimycotic drug clotrimazole, also inhibited the formation of all three metabolites. Polyclonal antibodies that recognize liver cytochrome P450 1A, 2A, 2B, 2C, and 3A enzymes did not inhibit 5 alpha-androstane-3 beta,17 beta-diol hydroxylase activity. Overall, these results are consistent with the hypothesis that the 6 alpha-, 7 alpha-, and 7 beta-hydroxylation of 5 alpha-androstane-3 beta,17 beta-diol by rat prostate microsomes is catalyzed by a single, high-affinity P450 enzyme. This cytochrome P450 enzyme appears to be structurally distinct from those in the 1A, 2A, 2B, 2C, and 3A gene families.

Androstane-3,17-diol↗
PubMed1992

The effects of magnesium and fluoride on the hydrolysis of octacalcium phosphate.

The adsorption of Mg ions on octacalcium phosphate (OCP) and its effect on OCP hydrolysis, with and without F, were studied. The Mg adsorption isotherm was fitted by the Langmuir model with an affinity constant of 0.74 ml/mumol and maximum number of sites, 31.19 mumol/g. The hydrolysis rates were measured in a pH stat by titration of base and were strongly temperature dependent. The products were examined by X-ray diffraction and chemical analysis. OCP hydrolysis takes place in two stages: the fast initial process, which is attributed to the surface topotactical conversion, followed by the main, slower process, which involves the nucleation and crystal growth. Mg ions, as 1 mmol/l MgCl2, prevented the initial surface reaction and decreased the nucleation rate dramatically and the growth rate slightly; F increased the rates of surface reaction and both the nucleation and crystal growth processes. The Ca/P ratio (1.53) and the line broadening in the X-ray diffraction patterns of the apatitic products were not significantly affected by the F. Mg also did not affect the Ca/P ratio and the line broadening at (002) diffraction, but decreased the line broadening at (310) diffraction.

Adsorption↗
PubMed1994

Adsorption of [3H]-lipoteichoic acid to hydroxyapatite and its effect on crystal growth.

3H-labelled lipoteichoic acid was isolated from Lactobacillus casei cells cultured in the presence of [2-3H]-glycerol. The adsorption characteristics of both native and deacylated [3H]-lipoteichoic acid on to hydroxyapatite crystals were determined in 2.0 mM CaCl2, 50 mM Hepes, pH 7.2. The maximum numbers of adsorption sites per unit surface area were 80 +/- 3 and 49 +/- 2 nmol/m2 for native and deacylated lipoteichoic acid, respectively. At low concentrations, which were previously found to stimulate hydroxyapatite growth in a supersaturated solution (1.0 mM CaCl2, 7.5 mM KH2PO4, 50 mM Hepes, pH 7.2), lipoteichoic acid appeared for a large part adsorbed to the crystals, while crystal growth was delayed when there was an excess of unbound lipoteichoic acid in solution. These results suggest that lipoteichoic acid released from plaque bacteria may have dual effects both on the precipitation of calcium phosphate in dental plaque and on the remineralization of lesions in the underlying hard tissues.

Adsorption↗
PubMed1994

Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score.

The amounts of fluoroapatite and 'CaF2-like' fluoride (F) were determined in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8-2.6 parts/10(6) F in the drinking water and to brushing with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F area. Unerupted enamel did not etch significantly (p > 0.05) deeper than erupted enamel. No significant differences (p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 microns). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 microns and greater than 100 microns. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 microns. In contrast to a similar low-F area (water F < 0.10 parts/10(6)), no significant 'CaF2-like' F could be detected in erupted or unerupted enamel for the high-F area.

Dental Enamel↗
PubMed1994

Current strategies for dentist-applied treatment in the management of hypersensitive dentine.

Few of the many dentist-applied treatments for dentine hypersensitivity meet the requirements of an ideal desensitizing agent'. This paper, although not exhaustive, covers methods that may be classified from simplest to most complex. Topical methods are simple, but they are often uncomfortable and the effects usually quite short-lasting, and many fall short of the 'ideal'. Fluorides and oxalates appear to be the best topical methods. Iontophoresis of fluoride represents an intermediate stage of complexity and it meets most of the criteria of an ideal desensitizing agent. Newer restorative materials, such as glass-ionomer cements and dentine bonding agents, are the most complex. These are still under investigation, but when the tooth needs recontouring, or in difficult cases that do not respond to other treatments, the dentist may choose to use a restorative material. Resin primers alone could be promising but the effects are not permanent and investigation into their use is still under way. Finally, laser treatment has been espoused for dentine desensitization. This requires extremely expensive equipment, must be dentist applied, and might produce pulpal irritation. Much more study is needed on restorative treatments and lasers before they can be considered as effective desensitizing agents. Until that research is completed, the dentist must choose one or more of the available methods in order to have a clinical therapy that is likely to relieve the symptoms of hypersensitive dentine.

Caustics↗
PubMed1995

Fluoride retention of incipient enamel lesions after treatment with a calcium fluoride varnish in vivo.

The aim was to determine the fluoride retention in plaque-covered and clean incipient enamel lesions after topical application of a CaF2/NaF varnish (Bifluorid 12). In 50 specimens of bovine enamel an incipient lesion was produced with acidic hydroxyethylcellulose (pH 4.8; 72 h). 40 specimens were fluoride varnished; the 10 remaining specimens were used for measuring baseline fluoride content. Each six of the fluoridated specimens were recessed in the buccal aspects of an intraoral appliance worn for 5 days. During the experimental period one side of the appliance was kept clean, and plaque growth was allowed on the other. KOH-soluble and structurally bound fluoride were determined immediately, 1 day, 3 days and 5 days after fluoridation, and compared with the baseline fluoride content of the enamel. Immediately after fluoridation, a considerable amount of KOH-soluble fluoride was bound, but after 5 days 80% had been lost. Simultaneously a significant increase of non-KOH-soluble or structurally bound fluoride was detected in both plaque-covered and clean enamel. It is evident that this CaF2/NaF varnish deposits more KOH-soluble fluoride on the surface of demineralized enamel than other varnishes, but after 5 days fluoride retention is similar to that from other varnishes.

Analysis of Variance↗
PubMed1985

Reduction of oxidized cytochrome c by ascorbate ion.

The kinetics and mechanism of the reduction of oxidized cytochrome c by ascorbate has been investigated in potassium nitrate, potassium 4-morpholineethanesulfonate (KMes), potassium sulfate and potassium ascorbate media. The results are consistent with simple second order electron transfer from ascorbate dianion to cytochrome c and do not support electron transfer from an ascorbate dianion bound to the protein of the cytochrome as recently proposed by Myer and Kumar. A rate constant of 8 X 10(5) M-1 X s-1 (25 degrees C, ionic strength, 0.1) was found for the electron-transfer step. This rate constant is essentially independent of the specific ions used in controlling ionic strength.

Alkanesulfonates↗