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Diacetyl (DA), a food flavorant, is linked with occupational lung disease. Our in vitro experiments described the formation of a covalent adduct by DA with Arg 5 of the Aβ 1-42 peptide, which resulted in only a transient increase in neurotoxicity in SH-SY5Y cells. However, in vivo implications of these effects on Alzheimer's disease (AD) pathogenesis and the underlying mechanisms remain poorly understood. In the APP/PS1 transgenic AD mouse model, DA treatment did not exacerbate learning and memory deficits in the Morris water maze test. Moreover, DA increased the Aβ 1-42 plaque burden and decreased neuronal inflammation in the transgenic AD mice. Additionally, cognitive impairment induced by intracerebroventricular Aβ 1-42 was restored by the DA treatment, as assessed by the T-maze test. A corresponding mitigation of neuronal inflammation was also observed in the hippocampus of these nontransgenic mice due to the acceleration of Aβ 1-42 aggregation by DA into nontoxic plaques. The data from SDS-PAGE, dot-blot, and TEM in vitro experiments corroborated the acceleration of the Aβ 1-42 aggregation observed in vivo in AD animal models and characterized the DA-induced formation of Aβ 1-42 fibrils. Such Aβ 1-42 -DA fibrils were unstable in the presence of detergent and amenable to detection by the thioflavin T reagent, thus underscoring the distinct assembly of these fibrils compared to that of the fibrils of the native Aβ 1-42 . Taken together, the results of this study present for the first time the in vivo implications of the DA-induced acceleration of Aβ 1-42 and may provide a strategy for the rational design of Aβ 1-42 aggregation accelerators as AD therapeutics that promote oligomer-free Aβ 1-42 fibril formation.

Rationale: Diacetyl (DA; 2,3-butanedione) is a chemical found commonly in foods and e-cigarettes. When inhaled, DA causes epithelial injury, though the mechanism of repair remain poorly understood. The objective of this study was to evaluate airway basal cell repair after DA vapor exposure., Methods: Primary human bronchial epithelial cells were exposed to DA or PBS for 1 h. Lactate dehydrogenase, cleaved caspase 3/7 and trans-epithelial electrical resistance were measured prior to and following exposure. Exposed cultures were analyzed for the airway basal cell markers keratin 5 and p63 as well as ubiquitin and proteasome activity. Cultures were also treated with a proteasome inhibitor (MG132)., Results: DA vapor exposure caused a transient decrease in trans-epithelial electrical resistance in all DA-exposed cultures. Supernatant lactate dehydrogenase and cleaved caspase 3/7 increased significantly at the highest DA concentration but not at lower DA concentrations. Increased keratin 5 ubiquitination occurred after DA exposure but resolved by day 3. Damage to airway basal cells persisted at day 3 in the presence of MG132., Conclusions: Diacetyl exposure results in airway basal cell injury with keratin 5 ubiquitination and decreased p63 expression. The ubiquitin-proteasome-pathway partially mediates airway basal cell repair after acute DA exposure., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Inhalation of diacetyl vapors by workers has been associated with obliterative bronchiolitis (OB), a poorly understood fibroproliferative disease of the small airways. Significant insights into the pathogenesis of OB have been obtained through the use of a rat model. Inhalation exposure of rats to diacetyl or 2,3-pentanedione, a related flavoring agent, can cause severe injury to the airway epithelium and underlying basement membrane. Repeated exposure to diacetyl or 2,3-pentanedione leads to aberrant repair, fibroproliferation and partial to complete occlusion of the airway lumen. Fibroproliferative lesions in rat airways were found to include both intraluminal polyps and circumferential intramural lesions. Intraluminal polyps have been observed to form secondary attachments spanning the airway lumen causing increasing obstruction. These airway lesions in rats are accompanied by inflammation in the form of peribronchial and perivascular infiltrates of lymphocytes, eosinophils and neutrophils. Diacetyl-induced OB lesions in the rat are similar to OB lesions in humans and provide a good model for studying the pathogenesis of this disease., (Published by Elsevier B.V.)

Vapor dosimetry models provide a means of assessing the role of delivered dose in determining the regional airway response to inspired vapors. A validated hybrid computational fluid dynamics physiologically based pharmacokinetic model for inhaled diacetyl has been developed to describe inhaled diacetyl dosimetry in both the rat and human respiratory tracts. Comparison of the distribution of respiratory tract injury with dosimetry estimates provides strong evidence that regional delivered dose rather than regional airway tissue sensitivity to diacetyl-induced injury is the critical determinant of the regional respiratory tract response to this water soluble reactive vapor. In the rat, inhalation exposure to diacetyl causes much lesser injury in the distal bronchiolar airways compared to nose and large tracheobronchial airways. The degree of injury correlates very strongly to model based estimates of local airway diacetyl concentrations. According to the model, regional dosimetry patterns of diacetyl in the human differ greatly from those in the rat with much greater penetration of diacetyl to the bronchiolar airways in the lightly exercising mouth breathing human compared to the rat, providing evidence that rat inhalation toxicity studies underpredict the risk of bronchiolar injury in the human. For example, repeated exposure of the rat to 200ppm diacetyl results in bronchiolar injury; the estimated bronchiolar tissue concentration in rats exposed to 200ppm diacetyl would occur in lightly exercising mouth breathing humans exposed to 12ppm. Consideration of airway dosimetry patterns of inspired diacetyl is critical to the proper evaluation of rodent toxicity data and its relevance for predicting human risk., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The chief chemotherapeutic drug, cisplatin had common bad effects such as nephrotoxicity, ototoxicity and bone marrow depression. This led us to develop a new potential anticancer drug based on nickel metal ion that may be less toxic. Nickel(II) diacetyl monoxime-2-pyridyl hydrazone complex cytoprotective effect, superoxide dismutase (SOD)-like activity and anticancer activities were studied. In vitro, the complex showed SOD-like activity of 86.62%. It was capable to kill 90.2% of Ehrlich ascites carcinoma (EAC) cells and to protect 92.48% of human RBCs. In vivo, the complex lowered the tumor burden markedly in a concentration-dependent manner. Noticeably, solid tumor growth was suppressed; tumor volume and weight were reduced and mice life span was lengthened. The hematological indices were improved, catalase activity was re-elevated and malondialdehyde (MDA) level was reversed towards normal. Nucleic acids, cholesterol, triglycerides, liver enzymes, urea and creatinine contents were reduced to near normal ranges. Glutathione (GSH), SOD, albumin and total protein levels were increased. In conclusion, our results revealed that the complex has the ability to suppress Ehrlich solid tumor growth in mice with minimal side effects. This may possibly via its redox activity. Surprisingly, nickel complex antitumor activities were more potent than those of cisplatin., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Occupational exposure to 2,3-butanedione (BD) vapors has been associated with severe respiratory disease leading to the use of potentially toxic substitutes. We compared the reactivity and respiratory toxicity of BD with that of two structurally related substitutes, 2,3-pentanedione (PD) and 2,3-hexanedione (HD). Chemical reactivity of the diketones with an arginine substrate decreased with increasing chain length (BD > PD > HD). Animals were evaluated the morning after a 2-week exposure to 0, 100, 150, or 200 ppm BD, PD, or HD (postexposure) or 2 weeks later (recovery). Bronchial fibrosis was observed in 5/5 BD and 5/5 PD rats at 200 ppm and in 4/6 BD and 6/6 PD rats at 150 ppm in the postexposure groups. Following recovery, bronchial fibrosis was observed in all surviving rats exposed to 200 ppm BD (5/5) or PD (3/3) and in 2/10 BD and 7/9 PD rats exposed to 150 ppm. Bronchial fibrosis was observed only in 2/12 HD-exposed rats in the 200 ppm postexposure group. Patchy interstitial fibrosis affected lungs of recovery groups exposed to 200 ppm PD (3/3) or BD (1/5) and to 150 ppm PD (4/9) or BD (7/10) and correlated with pulmonary function deficits. BD and PD were more reactive and produced more bronchial fibrosis than HD., (© The Author(s) 2016.)

Background: Treatment of melasma remains a challenge and involves multistep approach. Diacetyl boldine (DAB) stabilizes tyrosinase in its inactive form while TGF-β1 biomimetic oligopeptide-68 inhibits tyrosinase activity., Aims: (1) to study the efficacy and safety of the combination use of two formulae containing two principal ingredients: DAB and TGF-β1 biomimetic oligopeptide-68 on facial melasma, and (2) to compare their efficacy with 2% and 4% hydroquinone cream (HQ) on sun-protected normal skin., Methods: A randomized, double-blind, 12-week comparative study of pre-/post-treatment was conducted in 40 females. Melasma was evaluated by manual MASI score and MASI score with instrumentally graded darkness at baseline, 6th week, and 12th week. The author also compared their effect with HQ on the arms, assessed their safety profile throughout the study., Results: Thirty-eight subjects have completed the study. Their melasma showed improvement at the 6th week and 12th week as compared with baseline (P < 0.05). None developed severe reaction. Most subjects had temporary, mild skin reaction. About 2.6% of subjects graded themselves markedly improved, 76.3% moderately improved, and 21.1% slightly improved. Each formula showed either more efficacy or exerted faster action on pigment reduction than HQ., Conclusion: Combination of DAB serum at night and DAB/TGF-β1 biomimetic oligopeptide-68/sunscreen cream in the morning and at noon was effective and safe for facial melasma. They were superior to HQ in pigment reduction., (© 2016 Wiley Periodicals, Inc.)

Continuous presentation of the odorant diacetyl to the nematode Caenorhabditis elegans causes a decrease in the level of chemotactic response to diacetyl. This decline in response is caused by diacetyl adaptation. When wild-type nematodes were maintained at 15°C after pre-exposure to diacetyl, diacetyl adaptation did not continue up to 2 hr. Adaptation continued up to 6 hr in nematodes bred at 20°C, and it continued beyond 12 hr in nematodes bred at 25°C. These results indicate that the retention time of diacetyl adaptation is dependent on the environmental breeding temperature and suggest that moderate oxygen signals are required for maintaining the attenuated response to diacetyl because of the correlation between breeding temperature and production of oxygen intermediates. When isp-1 and clk-1 mutants, which show reduced rates of oxygen intermediate production, were maintained at 20 and 25°C after pre-exposure to diacetyl, the mutants showed a shorter retention time of diacetyl adaptation compared with that of wild-type nematodes. When gas-1 and mev-1 mutants, which have a hypersensitive response to oxidative stress, were maintained at 15 and 20°C, they showed a longer retention time of adaptation, that is, adaptation continued beyond 2 and 12 hr, respectively. When wild-type nematodes were maintained on plates that included 0.05% α-lipoic acid, which suppresses production of oxygen intermediates, the retention time of adaptation did not continue up to 6 hr in nematodes bred at 20°C and up to 12 hr in nematodes bred at 25°C. These results support the possibility that oxygen intermediates contribute to retention time for diacetyl adaptation in the nematode C. elegans., (© 2013 Wiley Periodicals, Inc.)

Rapid decontamination of the skin is the single most important action to prevent dermal absorption of chemical contaminants in persons exposed to chemical warfare agents (CWA) and toxic industrial chemicals (TICs) as a result of accidental or intentional release. Chemicals on the skin may be removed by mechanical means through the use of dry sorbents or water. Recent interest in decontamination systems which both partition contaminants away from the skin and actively neutralize the chemical has led to the development of several reactive decontamination solutions. This article will review the recently FDA-approved Reactive Skin Decontamination Lotion (RSDL) and will summarize the toxicity and efficacy studies conducted to date. Evidence of RSDL's superior performance against vesicant and organophosphorus chemical warfare agents compared to water, bleach, and dry sorbents, suggests that RSDL may have a role in mass human exposure chemical decontamination in both the military and civilian arenas.

Diacetyl vapor is associated with bronchiolar injury in man but primarily large airway injury in the rat. The goal of this study was to develop a physiologically based pharmacokinetic model for inspired vapor dosimetry and to apply the model to diacetyl. The respiratory tract was modeled as a series of airways: nose, trachea, main bronchi, large bronchi, small bronchi, bronchioles, and alveoli with tissue dimensions obtained from the literature. Airborne vapor was allowed to absorb (or desorb) from tissues based on mass transfer coefficients. Transfer of vapor within tissues was based on molecular diffusivity with direct reaction with tissue substrates and/or metabolism being allowed in each tissue compartment. In vitro studies were performed to provide measures of diacetyl metabolism kinetics and direct reaction rates allowing for the development of a model with no unassigned variables. Respiratory tract uptake of halothane, acetone, ethanol and diacetyl was measured in male F344 rat to obtain data for model validation. The human model was validated against published values for inspired vapor uptake. For both the human and rat models, a close concordance of model estimates with experimental measurements was observed, validating the model. The model estimates that limited amounts of inspired diacetyl penetrate to the bronchioles of the rat (<2%), whereas in the lightly exercising human, 24% penetration to the bronchioles is estimated. Bronchiolar tissue concentrations of diacetyl in the human are estimated to exceed those in the rat by 40-fold. These inhalation dosimetric differences may contribute to the human-rat differences in diacetyl-induced airway injury.

Using the hairless mouse screening model presented in the companion paper(1) the aim of this study was to assess two skin decontaminating systems: Fuller's earth (FE) and Reactive Skin Decontamination Lotion (RSDL) against two extremely toxic chemical warfare agents that represent a special percutaneous hazard, sulphur mustard (SM) and O-ethyl-S-(2[di-isopropylamino]ethyl)methyl-phosphonothioate (VX). Five minutes after being exposed on the back to either 2 µL of neat sulphur mustard or 50 µg.kg(-1) of diluted VX, mice were decontaminated. Both systems were able to reduce blisters 3 days after SM exposure. However, RSDL was found to be more efficient than FE in reducing the necrosis of the epidermis and erosion. In the case of VX exposure, RSDL, whatever the ratio of decontaminant to toxicant used (RSDL 10, 20, 50), was not able to sufficiently prevent the inhibition of plasma cholinesterases taken as a surrogate marker of exposure and toxicity. Only FE reduced significantly the ChE inhibition. Some of these observations are different from our previous results obtained in domestic swine and these changes are thus discussed in the perspective of using SKH-1 hairless mice for the initial in vivo screening of decontaminants.

The current emphasis on occupational exposures to diacetyl has led to new research on its effects. We evaluated whether the data are sufficient to support a transition from a hazard-based risk management approach to a quantitative occupational risk assessment approach, characterized by developing a health-based occupational exposure limit (OEL). Inhalation health effects data were evaluated and issues and uncertainties related to occupational risk assessment needs were identified. A systematic hazard characterization, supported by both the toxicology and epidemiology literature, showed that the respiratory tract effects of diacetyl are the primary end points of relevance for developing an OEL. In an effort to provide a systematic approach for the analysis of the issues that need to be considered in developing an occupational risk assessment for diacetyl, a potential OEL was derived. A concentration-response assessment was completed using tracheobronchial effects in mice as the critical effect. The resulting benchmark concentration (lower bound estimate or BMCL) was adjusted to a human equivalent concentration of 1.8 ppm. A composite uncertainty factor of 10 was recommended to account for extrapolation from an adjusted BMCL from an animal study and for human variability in sensitivity and taking into account other uncertainties in the overall database. The resulting OEL recommendation of 0.2 ppm as a time-weighted average (TWA) was supported by the current occupational epidemiology literature. This evaluation showed that a health-based OEL value can be derived for diacetyl with moderate to high confidence., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Occupational exposures to the butter flavouring agent diacetyl (2,3-butanedione) have caused lung inflammation and severe airflow limitation due to bronchiolitis obliterans. Diacetyl is naturally present in butter, beer, white wine, etc., and its pleasant odour is easily recognized by consumers. However, this pleasant odour may induce a false sense of safety when higher airborne concentrations are encountered in industrial use. In this study, the acute warning properties, in terms of sensory irritation, that could be useful to prevent workers from exposures to a high concentration were first investigated in a mouse bioassay. Then at higher exposure concentrations, the possibility of airflow limitation and pulmonary irritation were studied with the same mouse bioassay. Diacetyl induces concentration-dependent irritation in all parts of the respiratory tract during a 2-h exposure period. The no-observed-effect levels for each effect in the mice were above 100 ppm and initiation of sensory irritation in humans was estimated to occur above 20 ppm. No acute warning signal from the airways is expected at diacetyl levels that have caused bronchiolitis obliterans and other toxic effects. The sensory irritation effect, which occurred rapidly upon initiation of exposure, faded rapidly. Furthermore, high-level diacetyl exposures decreased the sensory irritation warning signal in mice upon repeated exposure, which suggests that the compound is especially insidious.

Occupational exposure to butter flavoring vapors (BFV) is associated with significant pulmonary injury. The goal of the current study was to characterize inhalation dosimetric patterns of diacetyl and butyric acid, two components of BFV, and to develop a hybrid computational fluid dynamic-physiologically based pharmacokinetic model (CFD-PBPK) to describe these patterns. Uptake of diacetyl and butyric acid vapors, alone and in combination, was measured in the upper respiratory tract of anesthetized male Sprague-Dawley rats under constant velocity flow conditions and the uptake data were used to validate the CFD-PBPK model. Diacetyl vapor (100 or 300 ppm) was scrubbed from the airstream with 76-36% efficiency at flows of 100-400 ml/min. Butryic acid (30 ppm) was scrubbed with >90% efficiency. Concurrent exposure to butyric acid resulted in a small but significant reduction of diacetyl uptake (36 vs. 31%, p < 0.05). Diacetyl was metabolized in nasal tissues in vitro, likely by diacetyl reductase, an enzyme known to be inhibited by butyric acid. The CFD-PBPK model closely described diacetyl uptake; the reduction in diacetyl uptake by butyric acid could be explained by inhibition of diacetyl reductase. Extrapolation to the human via the model suggested that inspired diacetyl may penetrate to the intrapulmonary airways to a greater degree in the human than in the rat. Thus, based on dosimetric relationships, extrapulmonary airway injury in the rat may be predictive of intrapulmonary airway injury in humans. Butyric acid may modulate diacetyl toxicity by inhibiting its metabolism and/or altering its inhalation dosimetric patterns.

The results here are the first demonstration of a family of carbohydrate fermentation products opening Ca2+ channels in bacteria. Methylglyoxal, acetoin (acetyl methyl carbinol), diacetyl (2,3 butane dione), and butane 2,3 diol induced Ca2+ transients in Escherichia coli, monitored by aequorin, apparently by opening Ca2+ channels. Methylglyoxal was most potent (K(1/2) = 1 mM, 50 mM for butane 2,3 diol). Ca2+ transients depended on external Ca2+ (0.1-10 mM), and were blocked by La3+ (5 mM). The metabolites affected growth, methylglyoxal being most potent, blocking growth completely up to 5 h without killing the cells. But there was no affect on the number of viable cells after 24 h. These results were consistent with carbohydrate products activating a La3+-sensitive Ca2+ channel, rises in cytosolic Ca2+ possibly protecting against certain toxins. They have important implications in bacterial-host cell signalling, and where numbers of different bacteria compete for the same substrates, e.g., the gut in lactose and food intolerance.

Research in skin decontamination and therapy of chemical warfare agents has been a difficult problem due to the simultaneous requirement of rapid action and non-aggressive behaviour. The aim of this study was to compare the performance of two decontaminating systems: the Canadian Reactive Skin Decontaminant Lotion (RSDL) and the Fuller's Earth (FE). The experiment was conducted with domestic swine, as a good model for extrapolation to human skin. RSDL and FE were tested against sulphur mustard (SM), a powerful vesicant, and VX, a potent and persistent cholinesterase inhibitor. When used 5 min after contamination, the results clearly showed that both systems were active against SM (10.1 mg/cm(2)) and VX (0.06 mg/cm(2)). The potency of the RSDL/sponge was statistically better than FE against skin injury induced by SM, observed 3 days post-exposure. RSDL was rather more efficient than FE in reducing the formation of perinuclear vacuoles and inflammation processes in the epidermis and dermis. Against a severe inhibition (67%) of plasmatic cholinesterases induced by VX poisoning, the potencies of the RSDL/sponge and FE were similar. Both systems completely prevented cholinesterase inhibition, which indirectly indicates a prevention of toxic absorption through the skin.

Transmembrane voltage-sensitive fluorescent dyes are used to study electrical activity in hearts. Green and red fluorescence emissions from di-4-ANEPPS excited with 488 nm light indicate both transmembrane voltage changes and heart movement. We have previously shown that the ratio, green fluorescence divided by red fluorescence, indicates the transmembrane voltage without effects of movement. Here we examine the feasibility of measuring the movement, which is useful for the study of cardiac function, by subtracting this ratiometric signal from the red or green fluorescence signal. The results of this subtraction show tissue movement and its relative changes during cardiac ischemia and perfusion with an electromechanical uncoupling agent. By incorporating the spatial variations in fluorescence intensity from the heart, tissue movement can be qualitatively mapped to examine relative changes, however, with limited ability to quantify absolute displacement. Since these maps are obtained simultaneously with corresponding transmembrane potentials, the method allows study of spatiotemporal cardiac movement patterns and their relationship to the action potential.

Dystrophin is an integral membrane protein involved in the stabilization of the sarcolemmal membrane in cardiac muscle. We hypothesized that the loss of membrane dystrophin during ischemia and reperfusion is responsible for contractile force-induced myocardial injury and that cardioprotection afforded by ischemic preconditioning (IPC) is related to the preservation of membrane dystrophin. Isolated and perfused rat hearts were subjected to 30 min of global ischemia, followed by reperfusion with or without the contractile blocker 2,3-butanedione monoxime (BDM). IPC was introduced by three cycles of 5-min ischemia and 5-min reperfusion before the global ischemia. Dystrophin was distributed exclusively in the membrane of myocytes in the normally perfused heart but was redistributed to the myofibril fraction after 30 min of ischemia and was lost from both of these compartments during reperfusion in the presence or absence of BDM. The loss of dystrophin preceded uptake of the membrane-impermeable Evans blue dye by myocytes that occurred after the withdrawal of BDM and was associated with creatine kinase release and the development of contracture. Although IPC did not alter the redistribution of membrane dystrophin induced by 30 min of ischemia, it facilitated the restoration of membrane dystrophin during reperfusion. Also, myocyte necrosis was not observed when BDM was withdrawn after complete restoration of membrane dystrophin. These results demonstrate that IPC-mediated restoration of membrane dystrophin during reperfusion correlates with protection against contractile force-induced myocardial injury and suggest that the cardioprotection conferred by IPC can be enhanced by the temporary blockade of contractile activity until restoration of membrane dystrophin during reperfusion.

Left ventricular (LV) myocardial slices were isolated from murine hearts (300 microm thick) and were stimulated at 1 Hz without external load. Mean myocardial slice O(2) consumption (MVo(2)) per minute (mMVo(2)) without stimulation was 0.97 +/- 0.14 ml O(2).min(-1).100 g LV(-1) and mean mMVo(2) with stimulation increased to 1.80 +/- 0.17 ml O(2).min(-1).100 g LV(-1) in normal Tyrode solution. Mean DeltamVo(2) (the mMVo(2) with stimulation - the mMVo(2) without stimulation) was 0.83 +/- 0.12 ml O(2).min(-1).100 g LV(-1). There were no differences between mean mMVo(2) with and without stimulation in Ca(2+)-free solution. The increases in extracellular Ca(2+) concentrations up to 14.4 mM did not affect the mMVo(2) without stimulation but significantly increased the mMVo(2) with stimulation up to 140% of control. The DeltamMVo(2) significantly increased up to 190% of the control in a dose-dependent manner. In contrast, the shortening did not increase in a dose-dependent manner. Cyclopiazonic acid (CPA; 30 microM) significantly reduced the DeltamMVo(2) to 0.27 +/- 0.06 ml O(2).min(-1).100 g LV(-1) (35% of control). The combination of 5 mM 2,3-butanedione monoxime (BDM) and 30 microM CPA did not further decrease DeltamMVo(2). Although BDM (3-5 mM) decreased the DeltamMVo(2) by 28-30% of control in a dose-independent manner, 3-5 mM BDM decreased shortening in a dose-dependent manner. Our results indicate that the DeltamMVo(2) of mouse LV slices during shortening under mechanically unloaded conditions consists of energy expenditure for total Ca(2+) handling during excitation-contraction coupling, basal metabolism, but no residual cross-bridge cycling.

Background: Actomyosin ATPase is one of the major ATP consuming enzymes in the myocardium. We tested whether 2,3-butanedione monoxime (BDM), a reversible inhibitor of actomyosin ATPase, given before coronary occlusion, limits infarct size in anesthetized open-chest dogs., Methods and Results: After circumflex artery catheterization using fluoroscopic guidance, BDM (125 mM) or buffer vehicle was infused (12.0 ml/min) for 20 min (BDM-20, n = 5 and Buffer-20, n = 6) or for 5 min (BDM-5, n = 6 and Buffer-5, n = 6) prior to 60 min of ischemia and 3 h of reperfusion. BDM administration increased subendocardial blood flow 271% above baseline flow (radioactive microspheres), and systolic wall thickening was converted to wall bulging (wall thickening by sonomicrometry was -27 +/- 29% and -22 +/- 13% of baseline in BDM-20 and BDM-5, respectively). Adjusted mean infarct size (% area-at-risk) was 11.0 +/- 2.8% and 11.9 +/- 2.6% in BDM-20 and BDM-5 vs. 20.2 +/- 2.5% and 20.5 +/- 2.5% in Buffer-20 and Buffer-5 (ancova, P < 0.05 for each BDM vs. Buffer group). Measurement of glycolytic metabolites and the adenine nucleotide pool of myocardium paced electronically at 150 beats per minute during total ischemia at 37 degrees C following BDM showed a metabolic response similar to that seen in ischemic preconditioning. ATP depletion, nucleoside production, and lactate accumulation were slowed in ischemic tissue treated with BDM., Conclusion: BDM given before the onset of ischemia markedly limited infarct size and reduced energy demand after the onset of ischemia. The explanation for the reduced infarct size induced by BDM treatment is hypothesized to be the persistent reduction in energy demand found in ischemic BDM treated myocardium.

Background: The dissociation of mechanical from non-mechanical energy utilisation can be studied using BDM (2,3-butanedione monoxime), which inhibits the actin-myosin interaction without inhibiting Ca2+ transport. The objective of the present study was to establish if increasing the non-mechanical energy demand of perfused isolated pig hearts by dobutamine stimulation requires glycolysis with increased exogenous glucose uptake., Methods: Five isolated pig hearts (CTRL) were perfused for 90 min at constant flow (1 ml g(-1) min(-1)) with non-recirculating blood containing 30 mM BDM and 26 MBq/l of fluorine-18 2-fluoro-2-deoxyglucose (IFDG). This was compared with five hearts (DOBU) subjected to the same protocol for the first 30 min and then to dobutamine (1.5 microM) for the following 30 min and dobutamine (4 microM) for the last 30 min. Five other isolated hearts were perfused as for the DOBU group but without BDM (CTRLDOBU). Using a clinical PET scanner, glucose uptake was assessed by estimating 18FDG uptake using linear regression. The slope variations were compared using a global test of coincidence., Results: Heart rate was at 100 +/- 2 b.p.m. in the CTRL group and at 180 +/- 7 b.p.m. in the DOBU group. 18FDG uptake was homogeneous within the whole myocardium and we observed a linear and regular increase in both the CTRL and DOBU groups (p, NS). In the CTRLDOBU group, 18FDG uptake was also homogeneous within the whole myocardium, but slopes of 18FDG uptake during dobutamine perfusion were higher than without dobutamine., Conclusion: In blood-perfused isolated pig hearts, exogenous glucose is not necessarily required when non-mechanical energy is increased by dobutamine stimulation. These findings suggest that ATP derived from glycolysis is not necessary to preserve myocardial Ca2+ transport during beta-adrenergic stimulation.

Background: Right heart dysfunction is a major cause for early morbidity and mortality after heart transplantation. Experiments were designed to evaluate the influence of the calcium-desensitizing drug 2,3-butanedione 2-monoxime (BDM) on right heart function in a porcine model of heart transplantation., Methods: Donor hearts of domestic pigs were arrested with BDM in Krebs solution (n = 7) and with BDM in Bretschneider's histidine-tryptophan-ketoglutarate (HTK) solution (n = 6). There were 2 control groups: University of Wisconsin (UW, n = 6) and HTK (n = 6). An isovolumic model was used in which the right ventricular volume was precisely controlled in vivo with an intracavitary high-compliance balloon. After 4 hours of ischemia, hearts were transplanted into recipients. After 1 and 2 hours of reperfusion, the right ventricular balloon volume was increased in 10-mL increments until right ventricular failure occurred and the developed pressures were recorded., Results: Maximal right ventricular developed pressures were significantly different after 2 hours of reperfusion (UW: 35 +/- 13 mm Hg; HTK: 47 +/- 8 mm Hg; Krebs+BDM: 49 +/- 9 mm Hg; HTK+BDM: 50 +/- 6 mm Hg; P =.04). Hearts subjected to BDM could be loaded with a significantly increased volume after 1 hour and after 2 hours (UW: 57 +/- 10 mL vs HTK: 43 +/- 8 mL vs Krebs+BDM: 70 +/- 10 mL vs HTK+BDM: 67 +/- 15 mL; P =.002). Postischemic right ventricular enddiastolic compliance was significantly increased in groups treated with BDM after 1 hour (P =.02) and after 2 hours (P =.039)., Conclusions: The drug BDM significantly improves right ventricular function in a heart transplantation model. The increase in volume load and developed right ventricular pressure achieved by BDM application would translate into a decreased risk of right ventricular failure after clinical transplantation.

Introduction: 2,3-Butanedione monoxime (BDM) has been found to reversibly block cardiac contraction, without blocking electrical conduction. This study characterizes the dose-dependent effects of BDM on the conduction through the atrioventricular node (AVN) of rabbit heart., Methods and Results: Thirteen isolated atrial-AVN preparations were used in control, during and after exposure to 5, 10, and 20 mM BDM. Anterograde and retrograde pacing protocols were used to obtain the Wenckebach cycle length, effective and functional refractory periods of the AVN, index of AVN conduction delay (the area under the AVN conduction curve), as well as index of intra-atrial conduction delay between the AVN inputs. Compared to control, 5 and 10 mM BDM produced either shortening or no effect on all of the above parameters except a slight (6% and 14%, respectively) increase in the intra-atrial delay. At 20 mM, BDM produced a further increase in the intra-atrial delay (up to 50%) as well as in the retrograde AVN conduction delay (up to 16%), while the characteristics of the anterograde conduction were still improved. The effects of perfusion with BDM on these parameters were reversible after washout., Conclusions: Aside from its known effect as an electromechanical uncoupler, BDM reversibly altered some of the electrical responses of the AVN. Most of these alterations, however, did not impede but rather improved AVN conduction. Since a dose of 10 mM is sufficient to fully eliminate undesirable motion, BDM should be considered a safe and valuable tool in AVN studies in vitro requiring a mechanically quiescent preparation.

Bimakalim (Bim), an opener of ATP-sensitive K+ (KATP) channels, was given alone or with 2,3-butanedione monoxime (BDM), a reversible uncoupler of contractility, to protect myocardial function during 1 day of hypothermia. Left ventricular pressure (LVP), coronary flow (CF), percent O2 extraction (%O2E), and cardiac efficiency were measured in 96 isolated, perfused guinea pig hearts divided into seven groups: 1) cold control (no drugs); 2) BDM; 3) Bim; 4) BDM + Bim; 5) BDM + glibenclamide (Glib, a blocker of KATP channels); 6) BDM + Bim + Glib; and 7) time control (6 h warm perfusion only). Drugs were given before, during, and initially after 22 h of low CF at 3.8 degrees C. At 26 h (cold groups) or 4 h (warm group) LVP (mmHg; means +/- SE) was similar for time control (94 +/- 4) and BDM + Bim (92 +/- 4) groups, lower and equivalent in the BDM (65 +/- 7) and BDM + Bim + Glib (64 +/- 7) groups, but LVP was higher than in the Bim group (46 +/- 3), and lowest in the cold control (30 +/- 8) group. In addition, only in the BDM + Bim group were basal CF, %O2E, and cardiac efficiency returned to values obtained in the time control group. Epinephrine increased LVP to that of the time control (106 +/- 3) group only in the BDM + Bim group (106 +/- 3) after hypothermia, and CF increases with adenosine, 5-hydroxytryptamine, and nitroprusside were similar to that of the time control group only in the BDM + Bim group after hypothermia. All of the effects of Bim were reversed by Glib. These results indicate that Bim, given with BDM, effectively preserves myocardial function and metabolism as well as inotropic and vasodilatory reserve during long-term hypothermic preservation as if the 1-day hypothermic state had not been instituted. Because the beneficial effects of Bim are blocked by Glib, the protective effect of Bim likely results from maintained KATP channel opening. Treatment with exogenous KATP openers may prove useful in preserving cardiac function in the transplanted heart.

Background: Vascular dysfunction and myocardial contracture can both contribute to posttransplantation diastolic abnormalities commonly exhibited by heart transplants, but their respective importance remains incompletely elucidated. To address this issue, we assessed the effects of supplementing a new heart preservation solution, Celsior, with a nitric oxide precursor (L-arginine) and a compound known to uncouple excitation from contraction (2, 3-butanedione monoxime)., Methods: Fifty isolated buffer-perfused rat hearts were divided into four groups. In group 1, hearts were arrested with St. Thomas' Hospital solution No. 2 (Plegisol) and stored in normal saline solution. In group 2, Celsior solution was used for cardiac arrest and storage. Group 3 hearts were arrested with and stored in Celsior solution supplemented with 2 mmol/L of L-arginine. In group 4, Celsior solution used for arrest and storage was supplemented with both 2 mmol/L of L-arginine and 30 mmol/L of 2, 3-butanedione monoxime. All hearts were stored for 10 hours, subsequently reperfused for 1 hour on a Langendorff column, and left ventricular pressure-volume curves were constructed. 5-Hydroxytryptamine (10(-7) mol/L) and papaverine (5 x 10(-6) mol/L) were used to test changes in endothelium-dependent and endothelium-independent coronary vascular responses, respectively, and compared with those obtained during the preischemic period., Results: After 10 hours of cold storage, a major postischemic contracture was found in group 1. Left ventricular diastolic function was best preserved in group 4 at the end of storage and over the entire period of reperfusion. Coronary vasodilatory response to 5-hydroxytryptamine was completely lost in all groups after cold storage and reperfusion. Endothelium-independent vasodilatory response to papaverine was preserved in 2, 3-butanedione monoxime-treated hearts, whereas it was reduced in other groups., Conclusions: Our results suggest that myocardial contracture plays a major role in posttransplantation diastolic abnormalities shown by cardiac allografts. Alleviation of contracture significantly improves the responsiveness of coronary smooth muscles but does not affect that of the vascular endothelium which needs to be handled by separate interventions.

The negative inotropic effect of 2,3-butanedione monoxime (BDM) on the isometric twitch of guinea-pig papillary muscle was analysed by parameters characterizing the time course of the mechanogram. BDM at concentrations of up to 4 mmol/l produced a clear negative inotropic effect, whereas the Ca transient measured in isolated cardiomyocytes was only slightly affected. Peak force was more reduced than dF/dtmax and dF/dtmin. This led to an earlier, more narrow peak and a shortening of twitch duration. Based on a reaction scheme for the cross-bridge cycle, a mathematical model using a Ca transient and mechanograms as input data has been developed. The kinetic parameters were estimated by fitting the model to various time courses of force obtained at rising concentrations of BDM. BDM decreased the ratio of rate constants for cross-bridge attachment and detachment in a concentration-dependent manner: the formation of cross-bridges became inhibited, whereas dissociation was promoted. Above 4 mmol/l BDM the more marked alterations of the parameters of the mechanogram indicated an additional suppressing effect on intracellular Ca supply. The computer analysis suggests how the cellular mechanism(s) of the BDM-induced negative inotropic effect are reflected in the time course of the mechanogram.

The agent 2,3-butanedione monoxime (BDM) has been reported to reduce the sensitivity of myofilament force development to calcium ions, without affecting the calcium transient in myocardium. One would predict, therefore, that BDM should reduce the contractile state of the heart without reducing the amount of oxygen that is consumed to fuel the process of excitation-contraction coupling. The purpose of the present experiment was to test this hypothesis using isovolumically contracting, isolated, blood perfused canine hearts during beta-blockade induced by continuous intra-coronary infusion of propranolol (1 mg/h). Contractile state was increased in seven hearts by CaCl2 infusion. Subsequently, while the CaCl2 infusion was continued at the highest rate, contractile state was reduced by BDM infusion. At each contractile state, we measured the left-ventricular end-systolic pressure-volume relation (ESPVR), the relation between myocardial oxygen consumption and its mechanical correlate, pressure-volume area (MVO2 vs PVA), and the duration of the LV pressure waveform. Contractile state was quantified by interpolated developed pressure at a reference ventricular volume of 25 ml (P25). BDM infusion (0.5-7 mM) caused a dose-dependent reduction in contractile state (50% reduction in P25 at 2.4 +/- 0.3 mM), and a dose-independent increase in coronary blood flow. Furthermore, BDM significantly reduced the duration of the pressure waveform up to 40% at the highest rate of BDM infusion compared to the pressure waveform duration measured at maximum CaCl2 infusion. We observed a direct relationship between MVO2 of the mechanically unloaded heart and contractility; this relation was unaffected by BDM infusion (P > 0.3). The slope of the MVO2-PVA relation decreased with increases in contractile state, but this decrease was unaffected by BDM (P > or = 0.4). We conclude that in the isolated canine heart, BDM does not act energetically as expected for a myofibrillar calcium desensitizing agent.

The effects of administration of 2,3-butanedione monoxime (2,3-BM) or atropine alone and in combination were determined on the blood enzymatic activities of dichlorvos-exposed buffalo calves. Dichlorvos given po at 160 mg/kg body weight produced pronounced inhibition of erythrocyte acetylcholinesterase (AChE) and elevation in serum aminotransferases and phosphatases within 30 min. 2,3-BM administered alone or in conjunction with atropine to dichlorvos-exposed calves significantly reactivated erythrocyte AChE activity whereas atropine was ineffective. The effect of 2,3-BM plus atropine on other enzymatic activities was comparatively greater than that of either drug alone. The results indicated that combined treatment with 2,3-BM and atropine was most effective in reversing dichlorvos-induced enzymatic alterations.

Fibrinolytic therapy is aimed at dissolving the fibrin clot. Its use now represents the optimal therapy for an acute evolving myocardial infarction. Although improved fibrinolytic agents are now being developed, the next frontier appears to be thrombolytic therapy which will combine fibrinolysis to platelet active drugs and specific inhibitors of blood coagulation, targetting the blood clot formation process itself. The most promising agents in this regard are inhibitors of the platelet glycoprotein IIb-IIIa receptors and specific thrombin inhibitors active on clot bound thrombin. This should result in more complete control of the thrombogenicity of the culprit coronary artery lesion. The comprehensive approach for the management of acute myocardial infarction should however ultimately be reperfusion therapy combining to thrombolytic therapy measures that will preserve the acutely ischemic myocardium and prevent the long-term deleterious effect of infarct expansion and left ventricular remodelling.

The blood levels of cholinesterase reactivator 2,3-butanedione monoxime were determined in buffalo calves following single intramuscular doses of 20 and 50 mg/kg body weight. Blood cholinesterases and other enzymatic activities were monitored at various times. The drug was rapidly absorbed with half-life of 0.09-0.12 h. The peak 2,3-butanedione monoxime blood concentrations of 24.7 +/- 0.3 and 38.9 +/- 1.7 micrograms/ml occurred at 10 min after 20 and 50 mg/kg doses, respectively. The elimination half-life varied between 3.05 +/- 0.12 and 3.80 +/- 0.19 h. Lack of adverse effect of 2,3-butanedione monoxime on blood cholinesterases and other enzymes indicated that intramuscular doses as high as 50 mg/kg may be safely employed in buffaloes.