Transplacental Transfer of Polychlorinated Biphenyls, Polybrominated Diphenylethers, and Organochlorine Pesticides in Ringed Seals (Pusa hispida).

The transplacental transfer of persistent organic pollutants in marine mammals takes place at a formative developmental period, thereby exposing the fetus to endocrine-disrupting compounds. We evaluated the transplacental transfer of polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), and organochlorine pesticides (OCPs) in five pregnant ringed seals in Northern Labrador, Canada. PCBs, PBDEs, and OCPs were transferred from the mother to the fetus with average concentrations in the fetuses ranging from 0.3 ng/g lipid weight (lw) of mirex to 94 ng/g lw of PCBs. The average percent transferred to the blubber in the fetus was very low with <0.02 % for each of the compounds studied. Based on relationships observed, transfer for full-term fetuses is estimated to range from 0.03 to 0.27 %. Log K(ow) explained the transfer of PCBs (r (2) = 0.67, p < 0.001) and OCPs (r (2) = 0.62, p < 0.001) with those PCB congeners and OCP compounds having a log K(ow) of <6.0 and 4.6, respectively, because they are preferentially transferred to the fetus. Adult females transferred a contaminant mixture to their fetuses, which correlated with estimated fetal age (p < 0.001; r (2) = 0.697), with younger fetuses showing a greater proportion of compounds with low K(ow) compared with later-term fetuses. The implications for the prenatal exposure to these developmental toxicants remains unknown because current toxicity thresholds in marine mammals have only been derived from juveniles or adults.

Arsenic speciation in blue mussels (Mytilus edulis) along a highly contaminated arsenic gradient.

Arsenic is naturally present in marine ecosystems, and these can become contaminated from mining activities, which may be of toxicological concern to organisms that bioaccumulate the metalloid into their tissues. The toxic properties of arsenic are dependent on the chemical form in which it is found (e.g., toxic inorganic arsenicals vs nontoxic arsenobetaine), and two analytical techniques, high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and X-ray absorption spectroscopy (XAS), were used in the present study to examine the arsenic species distribution in blue mussels (Mytilus edulis) obtained from an area where there is a strong arsenic concentration gradient as a consequence of mining impacted sediments. A strong positive correlation was observed between the concentration of inorganic arsenic species (arsenic compounds with no As-C bonds) and total arsenic concentrations present in M. edulis tissues (R(2) = 0.983), which could result in significant toxicological consequences to the mussels and higher trophic consumers. However, concentrations of organoarsenicals, dominated by arsenobetaine, remained relatively constant regardless of the increasing As concentration in M. edulis tissue (R(2) = 0.307). XANES bulk analysis and XAS two-dimensional mapping of wet M. edulis tissue revealed the presence of predominantly arsenic-sulfur compounds. The XAS mapping revealed that the As(III)-S and/or As(III) compounds were concentrated in the digestive gland. However, arsenobetaine was found in small and similar concentrations in the digestive gland as well as the surrounding tissue suggesting arsenobetaine may being used in all of the mussel's cells in a physiological function such as an intracellular osmolyte.

Arsenobetaine formation in plankton: a review of studies at the base of the aquatic food chain.

Arsenobetaine is one of the major organoarsenic compounds found in aquatic organisms, including seafood and fish meant for human consumption. It has been widely studied over the last 50 years because of its non-toxic properties, and its origin is postulated to be at bottom of the aquatic food chains. The present review focuses on arsenobetaine formation in marine and freshwater plankton, comparing the arsenic compounds found in the different plankton organisms, and the methods used to assess arsenic speciation. The main findings indicate that in the marine environment, phytoplankton and micro-algae contain arsenosugars, with the first traces of arsenobetaine appearing in herbivorous zooplankton, and becoming a major arsenic compound in carnivorous zooplankton. Freshwater plankton contains less arsenobetaine than their marine relatives, with arsenosugars dominating. The possible role and formation pathways of arsenobetaine in plankton organisms are reviewed and the literature suggests that arsenobetaine in zooplankton comes from the degradation of ingested arsenosugars, and is selectively accumulated by the organism to serve as osmolyte. Several arsenic compounds such as arsenocholine, dimethylarsinoylacetate or dimethylarsinoylethanol that are intermediates of this pathway have been detected in plankton. The gaps in research on arsenobetaine in aquatic environments are also addressed: primarily most of the conclusions are drawn on culture-based experiments, and few data are present from the natural environment, especially for freshwater ecosystems. Moreover, more data on arsenic in different zooplankton species would be helpful to confirm the trends observed between herbivorous and carnivorous organisms.

Validation of diabetes case definitions using administrative claims data.

AIMS: Our aim was to validate three diabetes case definitions for children and adolescents aged <20 years in Canada using administrative and clinical data in the province of British Columbia. METHODS: We identified potential cases of diabetes from physician claims, hospitalizations and prescription drug records between 1992/1993 and 2007/2008 using the three different case definitions, which included a national standard as well as two regionally developed case definitions. Each case definition used a different combination of administrative data; however, only one definition used prescription drug records. The sensitivity of each definition was calculated against the 'gold standard' of diagnosed cases recorded in British Columbia's Children's Hospital Endocrinology and Diabetes Unit clinical database. RESULTS: During this time period, 2611 patients were seen at the British Columbia's Children's Hospital. The sensitivities (95% CIs) of the national and two regional case definitions were 0.95 (0.941-0.958), 0.97 (0.964-0.977) and 0.82 (0.800-0.830), respectively. CONCLUSIONS: Our results highlight the benefit of regional case definitions that exploit the availability of different data sources, but also support that a nationally derived definition is sensitive among children and adolescents.

Long-term efficacy and safety of combined prolonged-release oxycodone and naloxone in the management of non-cancer chronic pain.

OBJECTIVE: The aim of this study was to assess safety and efficacy of fixed combination oxycodone prolonged release (PR)/naloxone PR in terms of both analgesia and improving opioid-induced bowel dysfunction (OIBD) and associated symptoms, such as opioid-induced constipation (OIC), in adults with chronic non-cancer pain. STUDY DESIGN: These were open-label extension studies in which patients who had previously completed a 12-week, double-blind study received oxycodone PR/naloxone PR for up to 52 weeks. The analgesia study assessed pain using the modified Brief Pain Inventory-Short Form (BPI-SF). The bowel function study assessed improvements in constipation using the Bowel Function Index (BFI). RESULTS: At open-label baseline in the analgesia study (n = 379), mean score [+/- standard deviation (SD)] for the BPI-SF item 'average pain over the last 24 h' was 3.9 +/- 1.52, and this remained low at 6 months (3.7 +/- 1.59) and 12 months (3.8 +/- 1.72). Mean scores for BPI-SF item 'sleep interference', and the BPI-SF 'pain' and 'interference with activities' subscales also remained low throughout the 52-week study. In the bowel function study (n = 258), mean BFI score (+/- SD) decreased from 35.6 +/- 27.74 at the start of the extension study to 20.6 +/- 24.01 after 12 months of treatment with oxycodone PR/naloxone PR. Pain scores also remained low and stable during this study. Adverse events in both extension phases were consistent with those associated with opioid therapy; no additional safety concerns were observed. CONCLUSION: Results from these two open-label extension studies demonstrate the long-term efficacy and tolerability of fixed combination oxycodone PR/naloxone PR in the treatment of chronic pain. Patients experienced clinically relevant improvements in OIBD while receiving effective analgesic therapy.

Patient assessment of a novel therapeutic approach for the treatment of severe, chronic pain.

BACKGROUND AND OBJECTIVES: Opioid-induced constipation can have a major negative impact on patients' quality of life. This randomised clinical trial evaluated patient assessment of the efficacy and tolerability of oral prolonged-release (PR) oxycodone when co-administered with oral naloxone PR. METHODS: Two hundred and two patients with chronic cancer- or non-cancer-related pain undergoing stable oxycodone PR therapy (40, 60 or 80 mg/day) were randomised to one of four intervention groups: 10, 20 or 40 mg/day naloxone PR or placebo. Following a 4-week maintenance phase, patients were followed-up for 2 weeks in which time they received oxycodone PR only. At the end of the maintenance phase, patients and investigators were asked to assess treatment efficacy and tolerability, as well as preference for the titration or maintenance phase. RESULTS: Patient and investigator global assessment of efficacy and tolerability improved with increasing naloxone dose. Efficacy was ranked as 'good' or 'very good' by 50.0%, 67.4% and 72.5% of patients in the 10, 20 and 40 mg naloxone PR dose groups, respectively, compared with 43.5% of patients in the placebo group. Patient assessment of tolerability was similar between treatment groups and placebo, being ranked as 'good' or 'very good' by 83.3%, 79.1% and 82.5% of patients in the 10, 20 and 40 mg/day naloxone PR dose groups, respectively, compared with 71.7% of patients in the placebo group. The maintenance treatment phase was preferred by patients in the naloxone groups. A 2 : 1 dose ratio of oxycodone to naloxone was also assessed. Efficacy was ranked as 'good' or 'very good' by 70.4% of patients treated with the 2 : 1 dose ratio compared with 43.5% of patients receiving placebo. Tolerability of the 2 : 1 dose ratio was ranked as being 'good' or 'very good' by 81.5% of patients compared with 71.1% for the placebo group and patients preferred the maintenance phase. CONCLUSIONS: The co-administration of oral naloxone PR with oxycodone PR improves patient assessment of analgesic opioid therapy for severe chronic pain, in terms of both efficacy and tolerability.

Anti-inflammatory properties of a liposomal hydrogel with povidone-iodine (Repithel) for wound healing in vitro.

A liposomal hydrogel with 3% povidone-iodine (PVP-ILH, Repithel) has shown clinical benefit in settings where inflammation and/or reactive oxygen species are thought to impede wound healing (e.g., burns, chronic wounds and in smokers). This in vitro study investigated whether PVP-ILH is able to reduce inflammatory events responsible for the impairment of the wound healing process in such patients. Therefore, the following assays were conducted with PVP-ILH (and derived control hydrogels to identify the component responsible for the effect): inhibition of reactive oxygen species production by human polymorphonuclear neutrophils (PMNs) and in a cell-free system, oxygen consumption assay of PMNs (prior to oxidative burst), inhibition of human complement (limiting the generation of complement factors), mast cell degranulation, nitric oxide production by murine macrophages and TNF-alpha production by human monocytes/macrophages. Where toxicity could cause cell inhibition, cell viability was assessed. PVP-ILH and its components interacted in our series of bioassays at various stages in the inflammation cascade. Scavenging of superoxide anions was the most pronounced effect. Furthermore, povidone-iodine inhibited PMN production of reactive oxygen species (inhibition of oxygen consumption) and a mast cell inhibitory (stabilising) activity was observed. Based on these results, the clinically observed, beneficial wound healing effects of PVP-ILH may also be attributed to an impediment of inflammatory activity, mainly by iodine's free radical scavenging. Controlling oxidative stress in the wound may be of great importance, especially since further reactions as, e.g., the formation of peroxynitrite from NO and ROS are prevented.

Arsenic bioaccessibility and speciation in clams and seaweed from a contaminated marine environment.

The bioaccessible concentration and speciation of arsenic (soluble in a gastrointestinal medium and available for absorption into the bloodstream) were determined in softshell clams (Mya arenaria), harvested by local residents until 2005, and in seaweed (Fucus sp.) from an arsenic-contaminated marine site in Seal Harbour, Nova Scotia, Canada. Bioaccessibility extractions to simulate the human gastrointestinal environment (pH 1.5 and glycine for 1h followed by pancreatin, bile extract and pH adjustment to 7 for an additional 4h) and speciation of arsenic in extracts (HPLC-HG-AAS to target inorganic arsenic species) and whole samples (XANES) were carried out. Total arsenic for the clams from the contaminated area ranged from 218 to 228 ppm wet weight, with a bioaccessible fraction of 34-46%, and the major bioaccessible species of arsenic were inorganic. The seaweed from the contaminated area contained 27-43 ppm wet weight total arsenic, with the bioaccessible fraction ranging from 63% to 81%, and inorganic arsenic was also predominant. The predominantly inorganic nature of arsenic in the whole samples was confirmed by XANES. In concurrence with the closure of the area for clam harvesting, the clams and seaweed from Seal Harbour should probably not be used for human consumption.

Glutathione protects cardiac and skeletal muscle from cyclophosphamide-induced toxicity.

Administration of cyclophosphamide at a dose which is lethal to 10% of control athymic nude mice resulted in sudden death within 3 h in all mice that had been pretreated with the glutathione synthesis inhibitor L-buthionine-SR-sulfoximine. In Fischer 344 rats pretreated with L-buthionine-SR-sulfoximine, the cyclophosphamide dose producing 100% acute toxicity was lowered from 500-150 mg/kg; cardiac monitoring revealed ventricular fibrillation to be the cause of death. These and additional studies reported demonstrate that cytoplasmic glutathione is an important protectant against the cardiac and skeletal muscle toxicity of cyclophosphamide and indicate that such toxicity may be substantially increased by glutathione depletion. Since diet and many drugs (including cyclophosphamide itself) are known to affect glutathione levels, the present studies suggest that cardiac and skeletal muscle glutathione content is likely to be a clinically significant determinant of the frequency and severity of the adverse drug interactions and systemic toxicity sometimes observed during cyclophosphamide therapy.

Effect of repetitive brief episodes of ischemia on cell volume, electrolytes and ultrastructure.

The effects of repeated brief episodes of ischemia on myocardial cell volume, electrolytes and ultrastructure were studied in dogs. Seventeen animals were divided into five groups. Group 1 underwent a single 10 minute occlusion of the circumflex coronary artery, with no subsequent reperfusion. Group 2 was similarly subjected to a 10 minute coronary occlusion, but was allowed a 20 minute reperfusion period. Group 3 underwent two 10 minute occlusions separated by 20 minutes of reperfusion and Group 4 underwent four 10 minute occlusions, each separated from the next by 20 minutes of reperfusion. Group 5 was subjected to a single, uninterrupted 40 minute occlusion. The anterior and posterior papillary muscles in each heart were sampled to compare nonischemic versus ischemic myocardium. No changes in myocardial water or electrolytes occurred during ischemia. However, reperfusion was associated with slight increases in tissue water and potassium, loss of magnesium and minimal changes in sodium or calcium ions. Electron microscopic analysis revealed signs of mild ischemic injury (absence of normal intramitochondrial granules, partial loss of glycogen and slight clumping of the nuclear chromatin) in posterior papillary muscle from Groups 1, 3 and 4. Group 2 showed complete recovery with 20 minutes of reperfusion, whereas Group 5 showed evidence of irreversible injury. There was no difference in the appearance of myocardium that had been subjected to one, two or four 10 minute occlusions. It is concluded that intermittent periods of reperfusion between brief episodes of coronary ischemia have a protective effect and prevent a cumulative deterioration of myocardial ultrastructure.

The xanthine oxidase inhibitor oxypurinol does not limit infarct size in a canine model of 40 minutes of ischemia with reperfusion.

Free radicals such as superoxide (.O2-) produced by xanthine oxidase might cause cell death during reperfusion after myocardial ischemia. The effect of the xanthine oxidase inhibitor allopurinol on infarct size in ischemia-reperfusion models has been variable, possibly because of differences in treatment duration. Adequate inhibition of xanthine oxidase may require a sufficient pretreatment period to permit conversion of allopurinol to oxypurinol, the actual inhibitor of superoxide production. To test more definitively whether xanthine oxidase-derived free radicals cause cell death during reperfusion, the effect of oxypurinol on infarct size was evaluated in an ischemia-reperfusion model. Open chest dogs underwent 40 min of circumflex coronary artery occlusion followed by reperfusion for 4 days. Twelve dogs were treated with oxypurinol (10 mg/kg body weight intravenously 10 min before occlusion and 10 mg/kg intravenously 10 min before reperfusion) and 11 control dogs received drug vehicle alone (pH 10 normal saline solution). Nine control dogs from a concurrent study also were included. Infarct size was measured histologically and analyzed with respect to its major baseline predictors, including anatomic area at risk and collateral blood flow (measured with radioactive microspheres). Infarct size as a percent of the area at risk averaged 23.8 +/- 2.7% (mean +/- SEM) in the oxypurinol group (n = 10) and 23.1 +/- 4.2% in the control group (n = 17) (p = NS). Collateral blood flow to the inner two thirds of the ischemic wall averaged 0.08 +/- 0.01 ml/min per g in the oxypurinol group and 0.09 +/- 0.02 ml/min per g in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

The spectrum of pathology associated with percutaneous transluminal coronary angioplasty during acute myocardial infarction.

The purpose of this study was to determine at necropsy the morphologic consequences of percutaneous transluminal coronary angioplasty performed during acute myocardial infarction. The heart was examined in four patients who died between 6 hours and 4 days after coronary angioplasty. The patients had angioplasty of the left main coronary artery (one patient), left anterior descending coronary artery (two patients) and left circumflex coronary artery (one patient). Necropsy revealed residual stenosis, intimal hemorrhage and plaque disruption in all four patients. Also noted were distal embolization of plaque elements (two patients) and thrombotic occlusion of the coronary artery (one patient). In conclusion, the morphologic changes after angioplasty are varied. These changes illustrate the mechanisms of angioplasty and some of the complications that can be expected in a small number of cases. The morphologic changes associated with coronary angioplasty are similar in patients undergoing elective or emergency angioplasty although medial dissection was not observed in these patients with an evolving myocardial infarction.

Cardiac rupture, mortality and the timing of thrombolytic therapy: a meta-analysis.

This study examined the relation between the risk of cardiac rupture and the timing of thrombolytic therapy for acute myocardial infarction. To test the hypothesis that cardiac rupture is prevented by early thrombolytic therapy but is promoted by late treatment, randomized controlled trials of thrombolytic agents for myocardial infarction were pooled. A logistic regression model including 58 cases of cardiac rupture among 1,638 patients from four trials showed that the odds ratio (treated/control) of cardiac rupture was directly correlated with time to treatment (p = 0.01); at 7 h, the odds ratio was 0.4 (95% confidence limits 0.17 to 0.93); at 11 h, it was 0.93 (0.53 to 1.60) and at 17 h, it was 3.21 (1.10 to 10.1). Analysis of data from the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) trial independently confirmed the relation between time to thrombolytic therapy and risk of cardiac rupture (p = 0.03). Analysis of 4,692 deaths in 44,346 patients demonstrated that the odds ratio of death was also directly correlated with time to treatment (p = 0.006); at 3 h, the odds ratio for death was 0.72 (0.67 to 0.77); at 14 h, it was 0.88 (0.77 to 1.00) and at 21 h, it was 1 (0.82 to 1.37). Thrombolytic therapy early after acute myocardial infarction improves survival and decreases the risk of cardiac rupture. Late administration of thrombolytic therapy also appears to improve survival but may increase the risk of cardiac rupture.

The relative influence of distant and local (DEW-line) PCB sources in the Canadian Arctic.

Soil PCB contamination has been delineated at 18 of 21 Distant Early Warning Line (DEW-line) stations being cleaned up by the Canadian Department of National Defence (DND). As a result, detailed surface soil delineation data has been reported for contamination exceeding 1 microg/g (dw total Aroclor), which is the remedial criteria for PCB contaminated soil under the DEW-line cleanup project. The results of this delineation work has allowed us to estimate the mass of PCB contained in surface soil at these sites and to quantify the DEW-line as a source of PCBs to both local and Arctic wide contamination. Our analysis of DEW-line cleanup delineation reports suggests that pre-cleanup surface soils (top 10 cm) with over 1 microg/g PCB constituted a source of PCBs that ranged from 0.8 to 43 kg with a mean of 18 kg. The total mass of PCB at all 18 sites was 119 kg. Previous studies have described a "halo-effect" that surrounds DEW-line sites, whereby PCB signatures in soil and plants up to 10 km from source areas were attributed to the local source. At Cambridge Bay (CAM-M), Nunavut, our inventory of PCB sources and redistribution suggests that up to 3.4 kg of PCB were exported from the site to the surrounding tundra prior to cleanup. The primary mechanism of transportation appears to be wind borne particulate. Potential vapour phase emissions of PCB from contaminated soil at DEW-line sites appears to have been negligible.

Biological responses to PCB exposure in shorthorn sculpin from Saglek Bay, Labrador.

A local source of polychlorinated biphenyls (PCBs) in Saglek Bay, Labrador, has contaminated marine sediments and the coastal food web. As part of a larger assessment of ecological risks in the Bay, we evaluated biological responses to PCB concentrations in a northern fish species, the shorthorn sculpin (Myoxocephalus scorpius). Biological endpoints, including ethoxyresorufin-O-deethylase (EROD) activity in liver tissue, fish body condition, lipid content, and relative liver mass were examined in 35 sculpin collected during August-September 1999. Across a wide range of PCB concentrations (5.1-6920 ng/g wet weight (ww) in whole fish excluding liver), sculpin showed significant EROD induction (as much as 25-fold in the most exposed group). Responses varied directly with PCB concentrations but there was also an apparent threshold for induction at about 50 ng/g ww (whole fish excluding liver). A strong relationship between sculpin PCB concentrations and the concentrations of PCBs in the marine sediments of Saglek Bay suggests that concentrations above this threshold can arise from very low concentrations in sediments (2.3 ng/g dry weight). Other biological endpoints did not show significant responses to PCB concentrations, nor were they related to the observed EROD activity. Although PCDF compounds were present in trace amounts (primarily 2,3,4,7,8-PnCDF), mono-ortho and non-ortho substituted (coplanar) PCBs appeared to contribute the majority of the total dioxin toxic equivalent (TEQ) concentrations. Overall, the results indicate that biological responses occur in shorthorn sculpin with relatively low PCB concentrations (approximately 50 ng/g), which are not unrealistic for even mildly contaminated areas in northern Canada.

PCBs in sediments and the coastal food web near a local contaminant source in Saglek Bay, Labrador.

Polychlorinated biphenyls (PCBs) were measured in marine sediments and the coastal food web in Saglek Bay, Labrador, to investigate the influence of a local PCB source. Saglek Bay has been the site of a military radar station since the late 1950s and there was PCB-contaminated soil at a beach prior to cleanup in 1997-1999. PCB concentrations in marine sediments during 1997-1999 ranged from 0.24 to 62000 ng/g (dry weight) and decreased exponentially with distance from the contaminated beach. Given this gradient, spatial trends of PCBs in the food web were examined over four zones, according to distance from the contaminated beach: within 1.5 km--zone one, 1.5-4.5 km--zone two, 4.5-7.5 km--zone three, and greater than 7.5 km--zone four. PCB concentrations in a bottom-feeding fish (shorthorn sculpin, Myoxocephalus scorpius), decreased significantly from zone one to zone two, three, four, and distant Labrador reference sites. PCB concentrations in the eggs of a diving seabird (black guillemot, Cepphus grylle) were as high as 48000 ng/g during 1997-1999 and average concentrations in zones one and two were 84 and 13 times higher than in zone four. Marine invertebrates closely reflected the concentrations of PCBs in the associated sediment. In contrast to the benthic-based food web, anadromous arctic char (Salvelinus alpinus) showed no evidence of PCB accumulation from the contaminated sediments. Relatively high PCB concentrations were discovered in some great black-backed gulls (Larus marinus) and ringed seals (Phoca hispida) but appear to relate more to their high trophic level than sampling location. Those species that fed on or near the seabed and had limited foraging ranges were strongly influenced by the local contamination. Total PCB concentrations in the benthic-based food web were significantly higher than background levels for a distance of at least 7.5 km from the contaminated beach. This area is small in the context of widely distributed contamination from long-range transport but the area's high concentrations are comparable to levels associated with adverse effects elsewhere. Our findings should be useful to better assess the environmental impacts of PCB contamination at other coastal sites in the Arctic.

Effect of adenosine therapy at reperfusion on myocardial infarct size in dogs.

OBJECTIVES: The concept of lethal reperfusion injury in ischemic myocardium has been the subject of controversy. Adenosine administered during reperfusion has been reported to limit lethal reperfusion injury in several studies. On the contrary, it has been reported that cardioprotection may not be achieved with adenosine alone but may occur if adenosine is co-administered with lidocaine. Still other investigators have reported no beneficial effect of adenosine, given with or without lidocaine. If the positive reports are reproducible, they are important both because they provide evidence for the existence of reperfusion injury and establish a rationale for preventing it. Thus, the present study was done to determine if adenosine could limit lethal reperfusion injury in a canine model of regional myocardial ischemia and reperfusion, carefully controlled for baseline predictors of infarct size. METHODS: Dogs (n = 37) of either sex were subjected to 90 min of coronary occlusion followed by 3 h of reperfusion. Two groups of dogs received adenosine (150 micrograms/kg/min) intravenously for 155 min starting 5 min prior to the reperfusion. One treated group received adenosine only and a second group received adenosine plus lidocaine (2 mg/kg). Control dogs received a saline infusion. After 3 h of reflow, hearts were excised and infarct size was measured and expressed as a percentage of the ischemic area at risk (AAR). To control for variation in infarct size due to variation in collateral blood flow (CBF), infarct size among groups was compared using ANCOVA, using CBF as the independent variable and infarct size as the dependent variable. RESULTS: Transmural collateral blood flow and AAR were not significantly different between any of the groups. Mean infarct size (adjusted by ANCOVA) in control dogs (n = 9) was 38.1 +/- 5.3% of the AAR. Neither adenosine (n = 9) nor adenosine plus lidocaine (n = 7) significantly limited infarct size (35.6 +/- 5.6% AAR and 38.1 +/- 7.7% AAR, respectively; both P = NS). CONCLUSIONS: Intravenous adenosine therapy (150 micrograms/kg/min) during reperfusion, whether administered alone or in dogs previously treated with lidocaine, did not limit infarct size after 90 min of regional ischemia in canine myocardium.

The novel calcium antagonist Ro 40-5967 limits myocardial infarct size in the dog.

OBJECTIVE: The aim was to compare the infarct limiting effect of Ro 40-5967 (Ro40), a new calcium antagonist with little negative inotropic activity, with that of verapamil and with ischaemic preconditioning, a potent endogenous cardioprotective mechanism. METHODS: Dogs (n = 53) of either sex were subjected to 60 min of coronary occlusion followed by 3 h of reperfusion. Drug treated dogs received either verapamil (1.0 mg.kg-1) or Ro40 (3.0 mg.kg-1) intravenously for 100 min starting 15 min prior to the occlusion. Control dogs received a saline infusion. Ischaemic preconditioning consisted of four 5 min cycles of ischaemia alternating with four 5 min cycles of reperfusion. After 3 h of reflow, hearts were excised and infarct size was measured using tripheyltetrazolium chloride macrochemistry and expressed as percent of the ischaemic area at risk (AAR). To control for variation in infarct size due to variation in collateral blood flow, infarct size among groups was compared using ANCOVA, in which infarct size and collateral blood flow, measured at 30 min of occlusion, were dependent and independent variables, respectively. RESULTS: Transmural collateral blood flow and AAR were not significantly different between any of the groups. Mean infarct size (adjusted by ANCOVA for slight differences in collateral blood flow among groups) in control dogs (n = 13) was 25.9(SEM 3.2)% of the AAR. Both verapamil (n = 11) and Ro40 (n = 9) limited infarct size [14.2(3.2)% AAR and 16.7(2.9)% AAR, respectively; both p < 0.05]. Preconditioning (n = 17) also significantly limited infarct size [8.1(1.8)%; p < 0.01]. CONCLUSIONS: The new calcium antagonist, Ro 40-5967, was as effective as verapamil in limiting infarct size after 60 min of regional ischaemia followed by 3 h of reperfusion, although neither calcium antagonist was as effective as ischaemic preconditioning.

Adenosine slows ischaemic metabolism in canine myocardium in vitro: relationship to ischaemic preconditioning.

OBJECTIVE: Studies in rabbits suggest that the cardioprotective effects of adenosine against lethal cell injury may be related to production of adenosine and subsequent activation of adenosine A1 receptors. However, it is not known whether intracoronary adenosine therapy can mimic the metabolic sparing effects of preconditioning in rabbits or dogs. The purpose of this study was to determine the effect of intracoronary adenosine on ischaemic metabolism in totally ischaemic canine myocardium. METHODS: Dog hearts (n = 13) were excised and the coronary arteries were perfused with an oxygenated Krebs' buffer containing glucose. Adenosine was added to the buffer perfusing the circumflex (treated) region. Following perfusion, control and treated beds from each heart were subjected to 90 min total ischaemia at 37 degrees C. Tissue levels of ATP and glycolytic intermediates were determined at several time points during the ischaemic incubation. RESULTS: Adenosine significantly slowed the rate of ATP depletion, glycogen utilisation, and lactate accumulation during the first 20 minutes of total ischaemia. CONCLUSIONS: The results suggest that adenosine is capable of slowing ischaemic metabolism and they are consistent with the hypothesis that adenosine may mediate ischaemic preconditioning.

Effect of coronary occlusion site on ischaemic bed size and collateral blood flow in dogs.

The ischaemic bed size (myocardium at risk) and collateral flow are major determinants of experimental myocardial infarct size. These parameters were compared in dogs with coronary occlusions at four commonly used sites. Regional blood flow was measured 5 min after proximal coronary occlusion of the circumflex (LCC) or anterior descending (LAD) arteries, or after distal occlusion of the LAD, or its apical branch. Occlusions were done sequentially in random order separated by 30 min intervals. The anatomic regions normally supplied by each occluded artery (ischaemic beds) were identified by simultaneous postmortem coronary perfusion with different coloured dyes. Proximal occlusions of the LCC and LAD produced equivalent areas of ischaemia (37 and 36% of the left ventricle) and these ischaemic beds had similar amounts of collateral flow (0.12 and 0.16 cm3.min-1.g-1). In comparison, distal LAD and apical branch occlusions involved 23 and 11% of the LV and collateral flow averaged 0.23 and 0.36 cm3.min-1.g-1. Thus, proximal LAD or LCC occlusion produce comparable areas of severe ischaemia. Experimental models using distal occlusions are characterised by more variable but often less severe ischaemia.