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PubMed2006

Use of experimental design in the optimization of stir bar sorptive extraction for the determination of polybrominated diphenyl ethers in environmental matrices.

Stir bar sorptive extraction and liquid desorption (LD) followed by large volume injection and capillary gas chromatography coupled to mass spectrometry (SBSE-LD-LVI-GC-MS), had been applied for the determination of ultra-traces of eleven polybrominated diphenylethers (PBDEs), from tetra to nona congeners (BDE-47, BDE-100, BDE-99, BDE-85, BDE-154, BDE-153, BDE-183, BDE-197, BDE-196, BDE-207 and BDE-206), in environmental matrices. Instrumental calibration under the selected-ion monitoring (SIM) mode acquisition and parameters that could affect the SBSE-LD efficiency are fully discussed. A complete randomized factorial design was established for the first time to optimize the main experimental parameters that affecting the SBSE-LD efficiency, including decisive interactions, which provides a more realistic picture of the sampling process. The analysis of variance (ANOVA) was the statistical method used to analyze data. From the data obtained, it can be emphasized that experimental parameters such as extraction time (240 min), agitation speed (1250 rpm), methanol content (40%) and desorption conditions (acetonitrile, 15 min), were the best analytical compromise for the simultaneous determination between tetra and nona congeners in aqueous media. A remarkable recovery (65.6-116.9%) and repeatability (<12.1%) were attained, whilst the experimental data allowed very good agreement with predict theoretical equilibrium described by the octanol-water partition coefficients (K(PDMS/W) approximately = K(O/W)), with the exception of nona congeners since slightly lower yields were measured. Furthermore, excellent linear dynamic ranges from 0.01 to 14.0 microg/L (r2>0.9917) and low detection limits (0.3-203.4 ng/L) were also achieved for the eleven congeners studied. The proposed methodology was applied for the determination of ultra-trace levels of PBDEs in waste water, sediments and printed board circuit matrices by the standard addition approach, showing to be reliable, sensitive and having a low sample amount requirement in compliance with the international regulatory bodies.

Adsorption↗
PubMed2002

Reversible adsorption by a pH- and temperature-sensitive acrylic hydrogel.

Thermo- and pH-sensitive hydrogels were synthesized using N-isopropylacrylamide (NIPA) and N-aminopropylmethacrylamide, cross-linked with N,N'-methylenebis(acrylamide). The dependence of the degree of swelling on the cross-linking density was analyzed according to the Flory-Huggins theory and a master curve obtained. To optimize the efficiency of these hydrogels in controlled release, we studied the loading and release of a divalent molecule (naphthalenedisulfonic acid, NS-2) in media of different ionic strengths and pH. The uptake process followed the Langmuir adsorption isotherm model. The highest loading occurred when the amino groups in the gel were protonated (acidic pH) and could come close each other to form a binding site for the two sulfonic groups of NS-2, i.e. low degree of cross-linking and collapsed state. Below the phase transition temperature (33 degrees C), NS-2 loaded hydrogels quickly released a significant amount of adsorbate until a new equilibrium between free NS-2 and adsorbed NS-2 was achieved. Above that temperature, hydrogels not only stopped the release but were even able to take free NS-2 up again from the medium, showing that the loading/release process was reversible and reproducible after several temperature cycles. At 37 degrees C, the release rate was independent of the degree of cross-linking (NIPA caused the hydrogel to collapse), but was strongly affected by the pH and salt concentrations of the medium, which condition the strength of the interaction between the hydrogel amino groups and the NS-2 sulfonic groups. In an acidic medium, the protonated amino groups bind NS-2 strongly and the amount released is small. In contrast, at pH 7.4 or in the presence of a high salt concentration, the hydrogel loses its affinity for NS-2 and the release rate increases, giving pH- or salt-sensitive delivery systems. Additionally, since the hydrogel is collapsed, the release can be prolonged for a long period of time.

Acrylamide↗
PubMed1996

Analysis of the effect of local interactions on protein stability.

BACKGROUND: Protein stability appears to be governed by non-covalent interactions. These can be local (between residues close in sequence) or non-local (medium-range and long-range interactions). The specific role of local interactions is controversial. Statistical mechanics arguments point out that local interactions must be weak in stable folded proteins. However, site-directed mutagenesis has revealed that local interactions make a significant contribution to protein stability. Finally, computer simulations suggest that correctly folded proteins require a delicate balance between local and non-local contributions to protein stability. RESULT: To analyze experimentally the effect of local interactions on protein stability, each of the five Che Y alpha-helices was enhanced in its helical propensity. alpha-Helix-promoting mutations have been designed, using a helix/coil transition algorithm tuned for heteropolypeptides, that do not alter the overall hydrophobicity or protein packing. The increase in helical propensity has been evaluated by far-UV CD analysis of the corresponding peptides. Thermodynamic analysis of the five Che Y mutants reveals, in all cases, an increase in half urea ([urea]1/2) and in Tm, and a decrease in the sensitivity to chemical denaturants (m). ANS binding assays indicate that the changes in m are not due to the stabilization of an intermediate, and the kinetic analysis of the mutants shows that their equilibrium unfolding transition can be considered as following a two-state model, while the change in m is found in the refolding reaction (m(k)f). CONCLUSIONS: These results are explained by a variable two-state model in which the changes in half urea and Tm arise from the stabilization of the native state and the decrease in m from the compaction of the denatured state. Therefore, the net change in protein stability in aqueous solution produced by increasing the contribution of native-like local interactions in Che Y is the balance between these two conflicting effects. Our results support the idea that optimization of protein stability and cooperativity involve a specific ratio of local versus non-local interactions.

Amino Acid Sequence↗
PubMed2003

Coherent collective precession of molecular rotors with chiral propellers.

Successful attempts to manufacture synthetic molecular motors have recently been reported. However, compared with natural systems such as motor proteins, synthetic motors are smaller molecules and are therefore subject to thermal fluctuations that prevent them from performing any useful function. A mechanism is needed to amplify the single molecular motion to such a level that it becomes distinguishable from the thermal background. Condensation of molecular motors into soft ordered phases (such as liquid crystals) will be a feasible approach, because there is evidence that they support molecularly driven non-equilibrium motions. Here we show that a chiral liquid-crystalline monolayer spread on a glycerol surface acts as a condensed layer of molecular rotors, which undergo a coherent molecular precession driven by the transmembrane transfer of water molecules. Composed of simple rod-like molecules with chiral propellers, the monolayer exhibits a spatiotemporal pattern in molecular orientations that closely resembles 'target patterns' in Belousov-Zhabotinsky reactions. Inversion of either the molecular chirality or the transfer direction of water molecules reverses the rotation direction associated with switching from expanding to converging target patterns. Endowed only with the soft directional order, the liquid crystal is an optimal medium that helps molecular motors to manifest their individual motions collectively.

Crystallization↗
PubMed1985

Characterization of [3H]zetidoline binding to rat striatal membranes.

The binding of [3H]zetidoline, a novel neuroleptic agent, to rat brain striatal membranes was investigated in-vitro. The optimal binding conditions for [3H]zetidoline differed from those for [3H]spiperone in pH, temperature and time. [3H]Zetidoline has high affinity for striatal dopamine receptors. Its binding is saturable, stereo-specific, has a low non-specific component and is reversible and tissue specific. The Scatchard analysis gave a biphasic curve, indicating that [3H]zetidoline interacts with more than one population of receptor sites (B'max = 67 fmol mg-1 protein, K'd = 0.11 nM; B"max = 500 fmol mg-1 protein, K'd = 2.49 nM). Kinetic analysis of rates of association and dissociation yielded a Kd value in agreement with that measured at equilibrium. Inhibition studies indicated that only dopamine and dopaminergic agents are able to displace [3H]zetidoline from its binding sites, and in a different rank order from that for displacement of [3H]spiperone. (-)-Sulpiride was especially effective in inhibiting [3H]zetidoline specific binding. Furthermore, like that of [3H]benzamides, [3H]zetidoline binding appears to be highly Na+-dependent and Li+ only partially substitutes Na+.

Animals↗
PubMed2006

Maximal yields from multispecies fisheries systems: rules for systems with multiple trophic levels.

Increasing centralization of the control of fisheries combined with increased knowledge of food-web relationships is likely to lead to attempts to maximize economic yield from entire food webs. With the exception of predator-prey systems, we lack any analysis of the nature of such yield-maximizing strategies. We use simple food-web models to investigate the nature of yield- or profit-maximizing exploitation of communities including two types of three-species food webs and a variety of six-species systems with as many as five trophic levels. These models show that, for most webs, relatively few species are harvested at equilibrium and that a significant fraction of the species is lost from the web. These extinctions occur for two reasons: (1) indirect effects due to harvesting of species that had positive effects on the extinct species, and (2) intentional eradication of species that are not themselves valuable, but have negative effects on more valuable species. In most cases, the yield-maximizing harvest involves taking only species from one trophic level. In no case was an unharvested top predator part of the yield-maximizing strategy. Analyses reveal that the existence of direct density dependence in consumers has a large effect on the nature of the optimal harvest policy, typically resulting in harvest of a larger number of species. A constraint that all species must be retained in the system (a "constraint of biodiversity conservation") usually increases the number of species and trophic levels harvested at the yield-maximizing policy. The reduction in total yield caused by such a constraint is modest for most food webs but can be over 90% in some cases. Independent harvesting of species within the web can also cause extinctions but is less likely to do so.

Animals↗
PubMed2000

Optimization of solid-phase microextraction for the gas chromatographic-mass spectrometric determination of synthetic musk fragrances in water samples.

Described is a solid-phase microextraction-gas chromatography-mass spectrometric procedure for the determination of three polycyclic musk fragrances (galaxolide, tonalide, celestolide) and a nitro musk fragrance (musk ketone) in natural river water. Both classes of the musk fragrances could be extracted reproducibly from water samples with a recovery in the range of 45-50% and relative standard deviation of 11-18% for fragrances at 25-260 ng/l levels. Detection limits were between 14 and 22 ng/l. To achieve this reproducibility it was necessary to use an internal standard, pentachloronitrobenzene, for all substances. Best recoveries were achieved with polydimethylsiloxane (PDMS)-divinylbenzene fibers (compared to recoveries obtained with PDMS, polyacrylate or carboxen fibers) and extraction times of 45 min at 30 degrees C, with no need for attainment of equilibrium conditions. The latter was achieved at about 2 h. For Elbe River water, in the vicinity of Magdeburg, no matrix effects were observed. While the average levels of celestolide and musk ketone for samples investigated were below the detection limits, 14 and 22 ng/l, respectively, and for tonalide below the limit of quantification, 22 ng/l, the ambient levels of galaxolide in the Elbe River were 117 ng/l.

Fatty Acids, Monounsaturated↗
PubMed1995

How potassium affects the activity of the molecular chaperone Hsc70. I. Potassium is required for optimal ATPase activity.

Several functions of the 70-kilodalton heat shock cognate protein (Hsc70), such as peptide binding/release and clathrin uncoating, have been shown to require potassium ions. We have examined the effect of monovalent ions on the ATPase activity of Hsc70. The steady-state ATPase activities of Hsc70 and its amino-terminal 44-kDa ATPase fragment are minimal in the absence of K+ and reach a maximum at approximately 0.1 M [K+]. Activation of the ATPase turnover correlates with the ionic radii of monovalent ions; those that are at least 0.3 A smaller (Na+ and Li+) or larger (Cs+) than K+ show negligible activation, whereas ions with radii differing only approximately 0.1 A from that of K+ (NH4+ and Rb+) activate to approximately half the turnover rate observed with K+. Single turnover experiments with Hsc70 demonstrate that ATP hydrolysis is 5-fold slower with Na+ than with K+. The equilibrium binding of ADP or ATP to Hsc70 is unperturbed when K+ is replaced with Na+. These results are consistent with a role for monovalent ions as specific cofactors in the enzymatic hydrolysis of ATP.

Adenosine Diphosphate↗
PubMed2006

Linker histone H1 binds to disease associated amyloid-like fibrils.

Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most prevalent neurodegenerative diseases of the central nervous system. These two diseases share a common feature in that a normally soluble peptide (amyloid-beta) or protein (alpha-synuclein) aggregates into an ordered fibrillar structure. As well as structural similarities observed between fibrillar aggregates related to these diseases, common pathological processes of increased oxidative injury, excitotoxicity and altered cell cycle are also evident. It was the aim of this study to identify novel interacting proteins to the amyloid-like motif and therefore identify common potential pathways between neurodegenerative diseases that share biophysical properties common to classical amyloid fibrils. Optimal ageing of recombinant proteins to form amyloid-like fibrils was determined by electron microscopy, Congo red birefringement and photo-induced cross-linking. Using pull-down assays the strongest detected interacting protein to the amyloid-like motifs of amyloid-beta, alpha-synuclein and lysozyme was identified as histone H1. The interaction with the amyloid-like motif was confirmed by techniques including surface plasmon resonance and immunohistochemistry. Histone H1 is known to be an integral part of chromatin within the nucleus, with a primary role of binding DNA that enters and exits from the nucleosome, and facilitating the shift in equilibrium of chromatin towards a more condensed form. However, phosphorylated histone H1 is predominantly present in the cytoplasm and as yet the functional significance of this translocation is unknown. This study also found that histone H1 is localised within the cytoplasm of neurons and astrocytes from areas affected by disease as well as amyloid plaques, supporting the hypothesis that histone H1 favoured binding to an ordered fibrillar motif. We conclude that the binding of histone H1 to a general amyloid-like motif indicates that histone H1 may play an important common role in diseases associated with amyloid-like fibrils.

Alzheimer Disease↗
PubMed2002

Substituent effects on structural stability of formyl ketene and analysis of vibrational spectra of formyl haloketenes and formyl methylketene.

The conformational behavior and the structural stability of formyl fluoroketene, formyl chloroketene and formyl methylketene were investigated by utilizing quantum mechanical DFT calculations at B3LYP/6-31I + + G** and ab initio calculations at MP2/6-311 + + G** levels. The three molecules were predicted to have a planar s-cis<-->s-trans conformational equilibrium. From the calculations, the direction of the conformational equilibrium was found to be dependent on the nature of the substituting group. In formyl haloketenes, the cis conformation, where the C=O group eclipses the ketenic group, was expected to be of lower energy than the trans conformer. In the case of formyl methylketene the conformational stability was reversed and the trans form (the aldehydic hydrogen eclipsing the ketenic group) was calculated to be about 2 kcal mol(-1) lower in energy than the cis form. The calculated cis-trans energy barrier was found to be in the order: fluoride (15.3 kcal mol(-1)) > chloride (13.1 kcal mol(-1)) > methyl (11.7 kcal mol(-1). Full optimization was performed at the ground and the transition states of the molecules. The vibrational frequencies for the stable conformers of the three ketenic systems were computed at the DFT-B3LYP level, and the zero-point corrections were included into the calculated rotational barriers. Complete vibrational assignments were made on the basis of both normal coordinate calculations and comparison with experimental results of similar molecules.

Carbon↗
PubMed2003

Experimental approaches: dietary and hormone therapy.

Patients who suffer from intestinal failure depend on parenteral support to maintain nutritional equilibrium. In this chapter, recommendations for evaluation the absorptive capacity of patients with intestinal failure are defined, and the evidence and magnitude of the effect of dietary and hormone therapy is given. Regarding dietary advice, the effects of employment of diets with various carbohydrate:fat ratios in short-bowel syndrome (SBS) patients with and without a preserved colon is presented. Focus has been placed on the use of growth hormone but also on the use of a novel intestinotrophic hormone, glucagon-like peptide 2, in the promotion of intestinal adaptation in SBS patients. Overall, the ultimate aim in the treatment of SBS patients is to optimize remnant intestinal function, thereby eliminating the need for parenteral support and improving quality of life in these patients.

Gastrointestinal Agents↗
PubMed2006

The ABC transporter BmrA from Bacillus subtilis is a functional dimer when in a detergent-solubilized state.

BmrA from Bacillus subtilis is a half-size ABC (ATP-binding cassette) transporter involved in multidrug resistance. Although its supramolecular organization has been investigated after reconstitution in a lipid bilayer environment, and shows a dimeric and possibly a tetrameric form, the precise quaternary structure in a detergent-solubilized state has never been addressed. In the present study, BmrA was purified from Escherichia coli membranes using an optimized purification protocol and different detergents. Furthermore, the ATPase activity of BmrA and the quantity of bound lipids and detergent were determined, and the oligomeric state was analysed using SEC (size-exclusion chromatography) and analytical ultracentrifugation. The activity and the quaternary structure of BmrA appeared to be strongly influenced by the type and concentration of the detergent used. SEC data showed that BmrA could be purified in a functional form in 0.05 and 0.01% DDM (n-dodecyl-beta-D-maltoside) and was homogeneous and monodisperse with an R(s) (Stokes radius) of 5.6 nm that is compatible with a dimer structure. Sedimentation-velocity and equilibrium experiments unequivocally supported that BmrA purified in DDM is a dimer and excluded the presence of other oligomeric states. These observations, which are discussed in relation to results obtained in proteoliposomes, also constitute an important first step towards crystallographic studies of BmrA structure.

ATP-Binding Cassette Transporters↗
PubMed1997

Conditions for a heat shock response during oogenesis and embryogenesis of the amphibian Pleurodeles waltl.

The optimal conditions capable of inducing an increase in HSP70 neosynthesis during development of the urodele amphibian Pleurodeles waltl were determined in this study. These conditions depend on temperature, heat shock duration and recovery duration. In oocytes, a heat shock response was repeatedly obtained at 37 degrees C for 15 min followed by 1 h recovery. These results provided evidence for heat shock response at every stage considered. An increase in HSP70 synthesis was noted throughout oogenesis, but it did not lead to an increase in the amount of soluble HSP70, except for stage VI oocytes. Such results suggest that from stage II to stage IV oocytes, an equilibrium occurs between the HSP70 used and the HSP70 neosynthesized. In contrast, in stage VI oocytes, heat shock led to overproduction of HSP70. During early development, the heat shock response was repeatedly obtained only from the gastrula stage with a 37 degrees C shock and a 15 min duration of treatment. Surprisingly, during cleavage stage, the soluble HSP70 total amount increased after heat shock at a time when no HSP70 neosynthesis occurred.

Amino Acid Sequence↗
PubMed1972

Binding of thyrotropin-releasing hormone to plasma membranes of bovine anterior pituitary gland (hormone receptor-adenylate cyclase-equilibrium constant-( 3 H)thyrotropin).

An assay for the binding of [(3)H]thyrotropin-releasing hormone ([(3)H]TRH) is described. Plasma membranes isolated from bovine anterior pituitary gland bind about 600 femtomoles of this hormone per mg of protein, as compared to 15 femtomoles per mg of protein in the total adenohypophyseal homogenate (40-fold purification). The equilibrium constant of membrane receptor-[(3)H]TRH binding at 0 degrees C is 4.3 x 10(7) L.M(-1), or a half-maximal binding of this hormone at 23 nM. The binding is time-dependent; addition of unlabeled hormone induces dissociation of the receptor-[(3)H]TRH complex with a half-life of 14 min. The binding of TRH is not altered by 10 muM melanocyte-stimulating hormone-release inhibiting hormone, lysine-vasopressin, adrenocorticotropin, growth hormone, prolactin, luteinizing hormone, insulin, glucagon, L-thyroxine, or L-triiodothyronine. K(+) and Mg(++) increase formation of the receptor-TRH complex at optimal concentrations of 5-25 mM and 0.5-2.5 mM, respectively, with inhibition at higher concentrations. Ca(++) inhibits binding of TRH at all concentrations tested.

Animals↗
PubMed1989

Health status measurement in the evaluation of health promotion.

A step beyond treatment and even the prevention of disease is coming onto the health agenda. It is health promotion--"the advancement of well-being and the avoidance of health risks by achieving the optimal levels of the behavioral, societal, environmental and biomedical determinants of health." It differs from medical service in that the latter is directed largely toward overcoming poor health, disequilibrium with one's environment. Health promotion is aimed at maintaining the level of health and, insofar as possible, strengthening the potential (resources) for health. The emergence of health promotion raises an issue for those concerned with health status measurement: whether we consider health as having only biologic elements as traditionally understood in biomedical science, and role (performance) elements as traditionally understood in sociomedical science; or whether we add to these considerations a view of health as the dynamic equilibrium of individuals or groups of people with their environment, their capacity to live physically, mentally, and socially. The latter view entails measuring the health of people on a continuum extending from "perfect" harmony with one's environment and maximum potential for responding to adversities, on the one hand, to extreme invalidism and no reserves, i.e., the premorbid state, at the other extreme. That view also entails expanding attention to the whole population, not just the sick. It also means considering the relative emphasis to be given conceptual and methodologic work, individual versus community responsibilities for health, and the alleged medicalization of life.

Health Promotion↗
PubMed1991

Sugar-binding and crystallographic studies of an arabinose-binding protein mutant (Met108Leu) that exhibits enhanced affinity and altered specificity.

In addition to hydrogen bonds, van der Waals forces contribute to the affinity of protein-carbohydrate interactions. Nonpolar van der Waals contacts in the complexes of the L-arabinose-binding protein (ABP) with monosaccharides have been studied by means of site-directed mutagenesis, equilibrium and rapid kinetic binding techniques, and X-ray crystallography. ABP, a periplasmic transport receptor of Escherichia coli, binds L-arabinose, D-galactose, and D-fucose with preferential affinity in the order of Ara greater than Gal much greater than Fuc. Well-refined, high-resolution structures of ABP complexed with the three sugars revealed that the structural differences in the ABP-sugar complexes are localized around C5 of the sugars, where the equatorial H of Ara has been substituted for CH3 (Fuc) or CH2OH (Gal). The side chain of Met108 undergoes a sterically dictated, ligand-specific, conformational change to optimize nonpolar interactions between its methyl group and the sugar. We found that the Met108Leu ABP binds Gal tighter than wild-type ABP binds Ara and exhibits a preference for ligand in the order of Gal much greater than Fuc greater than Ara. The differences in affinity can be attributed to differences in the dissociation rates of the ABP-sugar complexes. We have refined at better than 1.7-A resolution the crystal structures of the Met108Leu ABP complexed with each of the sugars and offer a molecular explanation for the altered binding properties.

Amino Acid Sequence↗
PubMed1982

Characterization of adenylate cyclase-coupled alpha 2-adrenergic receptors in rat renal cortex using [3H]yohimbine.

Alpha 2 adrenergic receptors in rat renal cortex were measured with the antagonist ligand [3H]yohimbine. Renal cortical membranes contained 120 +/- 11.7 (SE) fmoles of binding sites per milligram of protein (n = 9). Their affinity for [3H]yohimbine was 10.4 +/- 0.5 (SE) nM (n = 9) from equilibrium studies and 7.2 +/- 3.3 (n = 4) from kinetic measurements. Alpha-adrenergic agonists and antagonists bound [3H]yohimbine sites with affinities consistent with alpha 2-receptor binding. The slope factors for the binding of all antagonists tested were close to 1, whereas agonists bound with slope factors of less than 1, consistent with the presence of receptors of more than one affinity. The alpha 2-receptors measured with [3H]yohimbine appeared to be coupled to the inhibition of adenylate cyclase. The affinities of alpha-adrenergic catecholamines measured in cyclase inhibition studies were similar to their affinities in binding studies when these were performed under conditions optimal for adenylate cyclase inhibition. Both sodium ion and GTP are required for maximal inhibition of renal cortical adenylate cyclase [Woodcock, E.A., C. I. Johnston, and C.A. Olsson. J. Cyclic Nucleotide Res. 6:261-271, 1980)]. Each of these factors produced a 10- to 20-fold decrease in the binding affinity of epinephrine. Together, a 100- to 200-fold decrease was produced. The concentrations of both sodium ion and GTP required to decrease the affinity of epinephrine were similar to the concentrations required for adenylate cyclase inhibition. This suggested that similar mechanisms were involved in decreasing the affinity of agonists for the alpha 2-receptor and promoting agonist-induced inhibition of adenylate cyclase.

Adenylyl Cyclases↗
PubMed1984

Detection of occult pericardial hemorrhage early after open-heart surgery using technetium-99m red blood cell radionuclide ventriculography.

Pericardial or mediastinal hemorrhage requiring reoperation occurs in 2% to 5% of patients, usually early (0 to 48 hours), after open-heart surgery. This hemorrhage may be occult, and resulting cardiac tamponade may easily be misinterpreted as ventricular dysfunction, common early postoperatively. In such cases, appropriate and timely intervention may not occur. Of 50 patients evaluated by technetium-99m red blood cell gated equilibrium radionuclide ventriculography (RNV) because of early postoperative cardiogenic shock of uncertain etiology, 17 had unique scintigraphic images suggestive of intrathoracic hemorrhage. Of these 17, 5 had a generalized "halo" of abnormal radioactivity surrounding small hyperdynamic right and left ventricles, 11 had localized regions of intense blood pool activity outside the cardiac chambers (two with compression of single chambers), and one demonstrated marked radionuclide activity in the right hemithorax (2000 ml of blood at reoperation). Twelve patients had exploratory reoperation for control of hemorrhage as a direct result of the scintigraphic findings, three were successfully treated with fresh frozen plasma and platelet infusions along with medical interventions to optimize cardiac performance, and two patients died in cardiogenic shock (presumed tamponade) without reoperation. In the 12 reoperated patients, all were confirmed to have active pericardial bleeding. Scintigraphic localization of abnormal blood pools within the pericardium corresponded to the sites at which active bleeding was witnessed at reoperation. The abnormal bleeding was etiologically related to the tamponade state, with marked improvement in hemodynamics after reoperation. Nine additional patients were reoperated for presumed tamponade after RNV revealed an exaggerated halo of photon deficiency surrounding the cardiac chambers.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Surgical Procedures↗