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PubMed1987

A simple in vitro method of radiolabelling human erythrocytes in whole blood with 113mIn-tropolonate.

A simple and rapid in vitro procedure has been developed for selectively radiolabelling erythrocytes in whole blood using 113mIn-tropolonate. A maximum labelling efficiency of 97% was achieved, of which 95.5% was on the erythrocytes after only 5 min incubation of whole blood at room temperature. The optimum amount of tropolone for labelling whole blood was 10 micrograms of tropolone per ml of blood using acid-citrate dextrose (ACD) as the anticoagulant and 50 micrograms of tropolone per ml of blood using heparin. Under these optimum conditions, only 2.5% of the cell-bound 113mIn was released from the labelled cells during a 1 h in vitro incubation in cell-free plasma, irrespective of the anticoagulant used. These results suggest that 113mIn-tropolonate may prove to be a useful in vitro agent for labelling erythrocytes for short-term clinical investigations, especially at centres where 99mTc and 111In are unavailable.

Cycloheptanes↗
PubMedDate not supplied

Relationship between electronic structure and cytotoxic activity of tropolones.

A structure-activity relationship of the cytotoxic activity of tropolone derivatives was discussed, using theoretical calculations. In order to clearly divide the tropolones into two structurally analogous groups, four different dipole moments (muG, muESP-G, muW and muESP-W) and heats of formation (deltaHf) of the tropolones [1-21] were calculated in the gas-phase and in water-solution by the conductor-like screening model/parametric method 3 (COSMO/PM3). The cytotoxic activities of the tropolones and 2-methoxytropones seem to be related to the three QSAR parameters deltadeltaHf, HOMO energy (EH) and muw. The cytotoxic activity of the five tropone derivatives [17-21] might depend on the QSAR parameters deltadeltaHf, LUMO energy (EL) and muESP-G. The results of the present study suggest the applicability of theoretical calculations such as frontier molecular orbital, dipole moments and deltadeltaHf in the prediction of the cytotoxic activity of tropolone derivatives.

Algorithms↗
PubMed1985

No difference in sensitivity for occult infection between tropolone- and oxine-labeled indium-111 leukocytes.

There is considerable disagreement as to whether oxine or tropolone is the best labeling agent for indium leukocytes. We have previously looked at the sensitivity of oxine-labeled 111In leukocyte scans for occult infections and now present a similar group of patients imaged with tropolone-labeled 111In leukocytes. Thirty-four patients (38 studies) with possible occult infection were prospectively studied. Patients were imaged 1-4 hr after injection and again at 24 hr postinjection. The early tropolone images had a sensitivity of 53% while the delayed images at 24 hr had a sensitivity of 93%. Based on a previous study, oxine-labeled leukocyte scans have an early sensitivity of 33% and a delayed sensitivity (at 24 hr) of 95%. The differences in sensitivity between oxine and tropolone when imaged early and at 24 hr were not statistically significant. We conclude that there is no significant difference in the ability to detect infection between oxine- and tropolone-labeled leukocytes, both early at 1-4 hr, and on delayed imaging 24 hr after injection.

Abscess↗
PubMed1981

Indium-111 tropolone, a new high-affinity platelet label: preparation and evaluation of labeling parameters.

Platelets were isolated with a new neutral, lipid-soluble metal complex of indium-111 and tropolone. Unlike oxine, which must be dissolved in ethyl alcohol, tropolone is soluble saline. Platelet labeling with In-111 tropolone can be performed in both acid-citrate-dextrose (ACD)-plasma and ACD-saline media within two hours' time. Labeling efficiency has been 80-90% in ACD-saline and 60-70% in the ACD-plasma medium. Optimum concentrations for the labeling of platelets with In-111 tropolone were 5 micrograms/ml in ACD-saline and 10 micrograms/ml in ACD-plasma, using a 15-min incubation at room temperature. A kit formulation for convenient routine preparation of In-111-labeled platelets has been developed. Seven parameters of platelet labeling were studied: concentration of tropolone, citrate, plasma proteins, and calcium ions; also platelet density, temperature, and pH of incubation medium. Their effects on the mechanism of platelet labeling with lipid-soluble tracers are discussed.

Affinity Labels↗
PubMed1982

Tropolone: a lipid solubilizing agent for cationic metals.

Lipid soluble agents which chelate radioactive cations have several potential uses in nuclear medicine including: brain imaging, labeling of blood elements, and identifying fatty infiltration of organs. A tropolone-gallium complex has been characterized by the determination of in vitro partition ratios correlated with in vivo organ distribution in the rat. Partition ratios were determined for gallium-67 citrate, indium-114m chloride, and iron-59 chloride cations complexed with tropolone in chloroform + water, octanol + water, olive oil + water, and olive oil + plasma two-phased systems. Tropolone proved to be highly effective in the lipid solubilization of these metal cations. Distribution studies in animals of these cations complexed with tropolone demonstrated an increased concentration of these cation complexes in tissues of high lipid content when compared with appropriate controls.

Animals↗
PubMed1988

Antibacterial activity of selected tropones and tropolones.

The antibacterial activity of 33 substituted and unsubstituted seven-member ring tropones and tropolones was examined on 14 reference strains representing Gram-positive and Gram-negative bacteria. It was shown that the chemical character and position of the substituent plays a distinct role in the biological activity of investigated compounds. Depending on the substituent the antibacterial effect may be either increased or diminished. C-1 thio and C-2 nitro derivatives of tropone are significantly more active than tropone. The dibenzotropone derivatives display no antibacterial activity. Hydroxymethyl derivatives of tropolone are more active than tropolone, while hydroxy-, isopropyl-, methyl- as well as tropolone acetates are equipotent.

Anti-Bacterial Agents↗
PubMed2006

Isoelectronic homologues and isomers: tropolone, 5-azatropolone, 1-H-azepine-4,5-dione, saddle points, and ions.

Computational studies of 12 64-electron homologues and isomers of tropolone in the S(0) electronic ground state are reported. Three minimum-energy structures, tropolone (Tp), 5-azatropolone (5Azt), and 5-H-5-azatropolonium (5AztH(+)), have an internal H-bond and planar C(s)) geometry, and three, tropolonate (TpO(-)), 5-azatropolonate (5AzO(-)), and 1-H-azepine-4,5-dione (45Di), lack the H-bond and have twisted C(2) geometry. All 6 substances have an equal double-minimum potential energy surface and a saddle point with planar C(2)(v) geometry. The energy for the gas-phase isomerization reaction 45Di --> 5Azt is near +4 kJ mol(-1) at the MP4(SDQ)/6-311++G(df,pd)//MP2/6-311++G(df,pd) (energy//geometry) theoretical level and around -20 kJ mol(-1) at lower theoretical levels. The dipole moments computed for 45Di and 5Azt are 9.6 and 2.1 D, respectively, and this large difference contributes to MO-computed free energies of solvation that strongly favor--as experimentally observed--45Di over 5Azt in chloroform solvent. The MO-computed energy for the gas-phase protonation reaction 45Di + H(+) --> 5AztH(+) is -956.4 kJ mol(-1), leading to 926.8 kJ mol(-1) as the estimated proton affinity for 45Di at 298 K and 1 atm. The intramolecular dynamical properties predicted for 5Azt and 5AztH(+) parallel those observed for tropolone. They are therefore expected to exhibit spectral tunneling doublets. Once they are synthesized, they should contribute importantly to the understanding of multidimensional intramolecular H transfer and dynamical coupling processes.

Aza Compounds↗
PubMed1975

Antibacterial activity of tropolone.

Tropolone was shown to be bacteriostatic and bactericidal for a wide range of bacterial species. This antibacterial activity was quantitated using standard methods. Tropolone treatment of whole cells resulted in cell lysis characterized by bleb formation and subsequent loss of cell contents after rupture of the bleb. Although bleb formation and lysis did not occur in the presence of 20% sucrose, cell viability was lost. Spheroplasts and protoplasts also lysed in the presence of tropolone. These results indicate that tropolone acts on the cell wall or envelope and on the plasma membrane.

Bacteria↗
PubMed1995

Comparison of 99m technetium hexamethylpropylene-amine oxime labelled leucocyte with 111-indium tropolonate labelled granulocyte scanning and ultrasound in the diagnosis of intra-abdominal abscess.

Fifty patients with suspected intra-abdominal abscess were investigated prospectively with ultrasound and with 99mTc-hexamethylpropylene-amine oxime (HMPAO) isotope labelled mixed leucocytes, using 111-In tropolonate granulocyte scanning as the reference standard. Twenty five patients had inflammatory bowel disease (three were postoperative): 21 of these had Crohn's disease and four had ulcerative colitis. The remainder comprised nine with postoperative fever and 16 with fever and abdominal pain. An abscess was diagnosed when focal activity on serial 111-In tropolonate and 99m-Tc-HMPOA images at one, three, and 24 hours resulted in activity at least equal to liver activity at 24 hours. Thirteen abscesses were diagnosed using each type of white cell scanning, resulting in 100% sensitivity for 99m-Tc-HMPAO compared with 111-In tropolonate. Bowel inflammation was easily distinguished from abscess on serial images. Eight of these 13 abscesses were detected by ultrasound. Altogether 17 abscesses were found. Ultrasound detected 12, including four liver abscesses which were not purulent and had not been detected by white cell scanning. Ultrasound had a sensitivity of 71% (12 of 17) and a specificity of 87% (33 of 38) using all confirmed abscesses as the reference standard. White cell scanning showed a sensitivity of 76% (13 of 17: as a result of the four non-purulent liver abscesses) and a specificity of 100%. 99m-Tc-HMPAO scanning is as accurate as 111-In tropolonate scanning, and has several advantages including simplicity, availability, superior image quality, and reduced radiation dose. Both methods are more sensitive and specific than ultrasound for intra-abdominal abscess detection but ultrasound is advisable if a neutrophil infiltrate is not suspected.

Abdominal Abscess↗
PubMed1983

Neutrophil labeling with indium-111: tropolone vs. oxine.

This study was undertaken to compare tropolone with oxine (8-hydroxy-quinoline) for labeling human neutrophils with In-111. Exposure of neutrophils to tropolone at concentrations required for efficient labeling resulted in a marked impairment of chemotaxis. In contrast, no impairment of neutrophil chemotaxis was observed using In-111 oxine. Labeling efficiencies obtained with In-111 tropolone under optimal conditions were consistently less than those obtained with In-111 oxine. We evaluated cells labeled by the two methods using chemotaxis radioassay to assess the chemotatic potential of labeled cells. The results led to the conclusion that the oxine technique is preferable to tropolone for labeling human neutrophils with In-111.

Chemotaxis, Leukocyte↗
PubMed1982

[Isolation of an antibacterial active tropolone from a Pseudomonas cepacia strain].

In the strain ATCC 17759 of Pseudomonas cepacia a highly antibacterial active substance was found, which could be identified as the tropolone bis-(3-hydroxy-2-oxocyclo-heptatrien-(3,5,7)-yl)-sulfide. This data confirm that tropolones are not only found in plants like western red cedars, but are also occurring as metabolites in bacteria. At least in Pseudomonas cepacia there seems to be an interesting reciprocal correlation between the production of tropolones and of phenacines. The purified tropolone showed a broad antibacterial activity spectrum against gram-positive and gram-negative microorganisms. The MIC-values were situated between 12.5 and greater than 100,0 microgram/ml.

Cycloheptanes↗
PubMed1969

The effect of tropolone on the formation of 3,4-dihydroxyphenylacetic acid and 4-hydroxy-3-methoxyphenylacetic acid in the brain of the mouse.

1. The development of a very sensitive and specific fluorimetric assay for 3,4-dihydroxyphenylacetic acid has made it possible to measure how inhibitors of the enzyme catechol-O-methyl transferase affect the relative concentrations of this acid and its O-methylated derivative 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) in the brains of mice treated with L-3,4-dihydroxyphenylalanine or probenecid.2. It was found that tropolone and tropolone-4-acetamide reduce the concentration of homovanillic acid in the brains of the treated mice to an extent dependent on the dose.3. The concentration of 3,4-dihydroxyphenylacetic acid in the brain was increased by the administration of tropolone or tropolone-4-acetamide but the dose and response were not simply related to one another.4. The results suggest that, in vivo, the formation of 3,4-dihydroxyphenylacetic acid is not always a simple alternative to the formation of homovanillic acid when the enzyme catechol-O-methyl transferase is inhibited.

Animals↗
PubMed1982

The comparison of 8-hydroxyquinoline, tropolone, and acetylacetone as mediators in the labelling of polymorphonuclear leucocytes with indium-111: a functional study.

Tropolone forms a lipophilic complex with indium-111 which is capable of mediating the labelling of polymorphonuclear leucocytes (PMNs) by this isotope; labelling efficiencies are comparable with the best achieved using 8-hydroxyquinoline and acetylacetone. However, in terms of PMN chemotaxis and phagocytosis, tropolone is significantly less toxic than either of te other ligands. 8-Hydroxyquinoline was found to reduce PMN chemotaxis and phagocytosis to approximately 70% of the control values at a concentration of 20 micro M. Tropolone may prove a superior labelling reagent.

Chemotaxis, Leukocyte↗
PubMed1987

111Indium-tropolone labeled human PMNs: a rapid method of preparation and evaluation of labeling parameters.

Pure polymorphonuclear leukocytes (PMNs) have been isolated from a small amount of human blood by a single-step density gradient centrifugation method using a commercially available Ficoll-Hypaque mixture of density 1.114. The cells were labelled with [111In]tropolone in both buffer and plasma. Cell viability, ability to generate superoxide anion, and chemotaxis were found to be unaltered both before and after labeling. The optimum tropolone concentration for labeling was found to be 1 X 10(-4) M. Labeling efficiency was higher at 37 degrees C than at room temperature. Compared to [111In]oxine, tropolone preparation both in buffer and plasma resulted in consistently higher yields. Preliminary experiments of in vivo cell viability of the labeled PMNs were carried out in rabbits. The ability of the cells to localize in experimentally produced inflammatory lesions was found to be intact. The method of cell separation and labeling described has been found to be simple and rapid and could easily be incorporated in routine nuclear medicine laboratory practice.

Animals↗
PubMed1984

PAC studies of 111In binding to transferrin, tropolone and acetylacetone in aqueous solutions.

Time integral and time-differential PAC measurements have been made over a wide temperature range in aqueous solutions of [111In]tropolonate and [111In]acetylacetonate. The quadrupole frequency in the latter is approximately 30% higher than that in the former and the molecular volumes derived from rotational correlation times show the expected differences. Apo-transferrin was separately added to the two 111In-chelates and the transfer of activity from chelate to transferrin followed as a function of relative molar concentrations. Very much larger molar ratios of transferrin to tropolone than of transferrin to acetylacetone were required before substantial transfer of 111In from chelate to transferrin took place. This difference in affinity for transferrin could be one significant factor in explaining the enhanced ability of [111In]tropolonate to label blood cells in the presence of plasma. The determination of PAC parameters in [111In]transferrin over a range of temperatures showed that the values of quadrupole frequency obtained depended on the number of binding sites assumed. For only one 111In site per molecule, the quadrupole frequency increases by over 50% as the temperature is reduced below the freezing point of the solution. If two 111In sites are assumed there appears to be a change in the percentage occupancy of the two sites on either side of the transition.

Cycloheptanes↗
PubMed1982

Conformational states of tubulin liganded to colchicine, tropolone methyl ether, and podophyllotoxin.

The conformational effects of colchicine, podophyllotoxin, and tropolone methyl ether binding to tubulin have been studied. Conditions for the stability of the purified calf brain protein were established, and the effects of binding were examined by means of difference absorption spectroscopy, circular dichroism, fluorescence, activation of tubulin GTPase, and tubulin self-association reactions. The tubulin-colchicine complex was isolated and characterized. It displays quenched intrinsic protein fluorescence, ligand fluorescence, and GTPase activity, probably accompanied by minor perturbations in the secondary structure. The conformation of the tubulin-colchicine complex appears to be nonidentical with that of the unliganded protein. Podophyllotoxin was not found to induce any of the mentioned changes. This ligand seems to bind through a hydrophobic interaction of its trimethoxybenzene ring with tubulin, as does colchicine. Binding of tropolone methyl ether, which is the analogue of the other part of the colchicine molecule that binds to tubulin, produced effects consistent with a ligand-linked conformational change. The small perturbation by tropolone methyl ether of the circular dichroism spectrum of tubulin resembles changes induced by colchicine.

Animals↗
PubMed1985

Synthesis and antitumor activity of tropolone derivatives. 2.

Structural requirement for antitumor activity of tropolone derivatives 2-4 was explored. Isochroman derivatives (6-17, 20, and 23) and alpha, alpha-disubstituted compounds 26-30 were synthesized and their antitumor activities were tested. These nontroponoid derivatives were all inactive, implying that a tropolone ring is essential for the activity. Several compounds related to the monotropolone analogue 3 were synthesized. Among them, 31-33 showed significant activity, but their potencies were considerably weaker than those of binary tropolone analogues 4.

Animals↗
PubMed2005

18O effects on the infrared spectrum and skeletal tunneling of tropolone.

Infrared-absorption profiles observed for vibrational transitions of gaseous tropolone often show sharp Q branch peaks, some of them ultranarrow spikes, indicative of the band origins for vibrational state-specific spectral tunneling doublets. In this work oxygen isotope effects for two CH wagging fundamentals, the COH torsion fundamental, and the skeletal contortion fundamental are reported. They allow considerations to be given: (1) oxygen isotope effects on the vibrational frequencies and state-specific tunneling splittings; (2) the asymmetry offset of the potential-energy minima for 16O and 18O tropolone; and (3) additional details concerning previously proposed high J rotation-contortion resonances in the contortional fundamental. The new results help to characterize the skeletal contortion fundamental and support the joint participation of skeletal tunneling with H tunneling in the vibrational state-specific tautomerization processes of tropolone in its ground electronic state.

Oxygen Isotopes↗