A Translational Model for Venous Thromboembolism: MicroRNA Expression in Hibernating Black Bears.

BACKGROUND: Hibernating American black bears have significantly different clotting parameters than their summer active counterparts, affording them protection against venous thromboembolism during prolonged periods of immobility. We sought to evaluate if significant differences exist between the expression of microRNAs in the plasma of hibernating black bears compared with their summer active counterparts, potentially contributing to differences in hemostasis during hibernation. MATERIALS AND METHODS: MicroRNA sequencing was assessed in plasma from 21 American black bears in summer active (n = 11) and hibernating states (n = 10), and microRNA signatures during hibernating and active state were established using both bear and human genome. MicroRNA targets were predicted using messenger RNA (mRNA) transcripts from black bear kidney cells. In vitro studies were performed to confirm the relationship between identified microRNAs and mRNA expression, using artificial microRNA and human liver cells. RESULTS: Using the bear genome, we identified 15 microRNAs differentially expressed in the plasma of hibernating black bears. Of these microRNAs, three were significantly downregulated (miR-141-3p, miR-200a-3p, and miR-200c-3p), were predicted to target SERPINC1, the gene for antithrombin, and demonstrated regulatory control of the gene mRNA expression in cell studies. CONCLUSIONS: Our findings suggest that the hibernating black bears' ability to maintain hemostasis and achieve protection from venous thromboembolism during prolonged periods of immobility may be due to changes in microRNA signatures and possible upregulation of antithrombin expression.

Proinflammatory phenotype of perivascular adipocytes: influence of high-fat feeding.

Adipose tissue depots originate from distinct precursor cells, are functionally diverse, and modulate disease processes in a depot-specific manner. However, the functional properties of perivascular adipocytes, and their influence on disease of the blood vessel wall, remain to be determined. We show that human coronary perivascular adipocytes exhibit a reduced state of adipocytic differentiation as compared with adipocytes derived from subcutaneous and visceral (perirenal) adipose depots. Secretion of antiinflammatory adiponectin is markedly reduced, whereas that of proinflammatory cytokines interleukin-6, interleukin-8, and monocyte chemoattractant protein-1, is markedly increased in perivascular adipocytes. These depot-specific differences in adipocyte function are demonstrable in both freshly isolated adipose tissues and in vitro-differentiated adipocytes. Murine aortic arch perivascular adipose tissues likewise express lower levels of adipocyte-associated genes as compared with subcutaneous and visceral adipose tissues. Moreover, 2 weeks of high-fat feeding caused further reductions in adipocyte-associated gene expression, while upregulating proinflammatory gene expression, in perivascular adipose tissues. These changes were observed in the absence of macrophage recruitment to the perivascular adipose depot. We conclude that perivascular adipocytes exhibit reduced differentiation and a heightened proinflammatory state, properties that are intrinsic to the adipocytes residing in this depot. Dysfunction of perivascular adipose tissue induced by fat feeding suggests that this unique adipose depot is capable of linking metabolic signals to inflammation in the blood vessel wall.

A Citywide Approach to SARS-CoV2 Testing.

The COVID-19 pandemic caused more than 30 million infections in the United States between March 2020 and April 2021. In response to systemic disparities in SARS-CoV2 testing and COVID-19 infections, health systems, city leaders and community stakeholders in Worcester, Massachusetts created a citywide Equity Task Force with a specific goal of making low-barrier testing available to individuals throughout our community. Within months, the state of Massachusetts announced the Stop the Spread campaign, a state-funded testing venture. With this funding, and through our community-based approach, our team tested more than 48,363 individuals between August 3, 2020 and February 28, 2021. Through multiple PDSA (Plan-Do-Study-Act) cycles, we optimized our process to test close to 300 individuals per hour. Our positivity rate ranged from 1.5% with our initial testing events to a high of 13.4% on January 6, 2021. During the challenges of providing traditional inpatient and ambulatory care during the pandemic, our health system, city leadership, and community advocacy groups united to broaden the scope of care to include widespread, population-based SARS-CoV2 testing. We anticipate that the lessons learned in conducting this testing campaign can be applied to further surges of SARS-CoV2, international environments, and future respiratory disease pandemics.

Use of lean in the emergency department: a case series of 4 hospitals.

STUDY OBJECTIVE: We describe the effects of Lean, a process improvement strategy pioneered by Toyota, on quality of care in 4 emergency departments (EDs). METHODS: Participants in 2 academic and 2 community EDs that instituted Lean as their single process improvement strategy made observations of their behavioral changes over time. They also measured the following metrics related to patient flow, service, and growth from before and after implementation: time from ED arrival to ED departure (length of stay), patient satisfaction, percentage of patients who left without being seen by a physician (2 EDs), the time from ordering to reading radiographs (1 ED), and changes in patient volume. RESULTS: One year post-Lean, length of stay was reduced in 3 of the EDs despite an increase in patient volume in all 4. Each observed an increase of patient satisfaction lagging behind by at least a year. The narratives indicate that the closer Lean implementation was to the original Toyota principles, the better the initial outcomes. The immediate results were also greater in the EDs in which the frontline workers were actively participating in the Lean-driven process changes. A factor that considerably affected the outcomes in the second and third year postimplementation was the level of continuous leadership commitment to Lean. CONCLUSION: Lean principles adapted to the local culture of care delivery can lead to behavioral changes and sustainable improvements in quality of care metrics in the ED. These improvements are not universal and are affected by leadership and frontline workforce engagement.

Application of lean manufacturing techniques in the Emergency Department.

BACKGROUND: "Lean" is a set of principles and techniques that drive organizations to continually add value to the product they deliver by enhancing process steps that are necessary, relevant, and valuable while eliminating those that fail to add value. Lean has been used in manufacturing for decades and has been associated with enhanced product quality and overall corporate success. OBJECTIVES: To evaluate whether the adoption of Lean principles by an Emergency Department (ED) improves the value of emergency care delivered. METHODS: Beginning in December 2005, we implemented a variety of Lean techniques in an effort to enhance patient and staff satisfaction. The implementation followed a six-step process of Lean education, ED observation, patient flow analysis, process redesign, new process testing, and full implementation. Process redesign focused on generating improvement ideas from frontline workers across all departmental units. Value-based and operational outcome measures, including patient satisfaction, expense per patient, ED length of stay (LOS), and patient volume were compared for calendar year 2005 (pre-Lean) and periodically after 2006 (post-Lean). RESULTS: Patient visits increased by 9.23% in 2006. Despite this increase, LOS decreased slightly and patient satisfaction increased significantly without raising the inflation adjusted cost per patient. CONCLUSIONS: Lean improved the value of the care we delivered to our patients. Generating and instituting ideas from our frontline providers have been the key to the success of our Lean program. Although Lean represents a fundamental change in the way we think of delivering care, the specific process changes we employed tended to be simple, small procedure modifications specific to our unique people, process, and place. We, therefore, believe that institutions or departments aspiring to adopt Lean should focus on the core principles of Lean rather than on emulating specific process changes made at other institutions.

Proenkephalin expression and enkephalin release are widely observed in non-neuronal tissues.

Enkephalins are opioid peptides that are found at high levels in the brain and endocrine tissues. Studies have shown that enkephalins play an important role in behavior, pain, cardiac function, cellular growth, immunity, and ischemic tolerance. Our global hypothesis is that enkephalins are released from non-neuronal tissues in response to brief ischemia or exercise, and that this release contributes to cardioprotection. To identify tissues that could serve as potential sources of enkephalins, we used real-time PCR, Western blot analysis, ELISA, immunofluorescence microscopy, and ex vivo models of enkephalin release. We found widespread expression of preproenkephalin (pPENK) mRNA and production of the enkephalin precursor protein proenkephalin (PENK) in rat and mouse tissues, as well as in tissues and cells from humans and pigs. Immunofluorescence microscopy with anti-enkephalin antisera demonstrated immunoreactivity in rat tissues, including heart and skeletal muscle myocytes, intestinal and kidney epithelium, and intestinal smooth muscle cells. Finally, isolated tissue studies showed that heart, skeletal muscle, and intestine released enkephalins ex vivo. Together our studies indicate that multiple non-neuronal tissues produce PENK and release enkephalins. These data support the hypothesis that non-neuronal tissues could play a role in both local and systemic enkephalin-mediated effects.

Inhibition of phosphatase activity enhances preconditioning and limits cell death in the ischemic/reperfused aged rat heart.

Brief, nonlethal episodes of ischemia in the mammalian heart provide cardioprotection against the detrimental effects of a longer duration ischemia. The manifestation of this preconditioning (PC) phenomenon is initiated by the enhanced phosphorylation state of signal transduction proteins. We reported previously that PC is decreased in the aged rat myocardium. Although the mechanism responsible for this loss is not understood, a reduction in the phosphorylation of critical proteins associated with PC may be postulated. Experiments were conducted to investigate whether PC in the aged heart can be restored with the inhibition of endogenous protein phosphatases thereby enhancing phosphorylation of signaling proteins. Levels of phosphatase activities were also assessed with adult heart aging. Hearts from young adult (3-4 mo.) and aged (21-22 mo.) Fischer-344 rats were perfused in the presence or absence of okadaic acid (OKA; 0.1 microM). Aged adult hearts were either not preconditioned or were preconditioned with two PC cycles (5 min ischemia/5 min reperfusion). Myocardial cellular death that developed with a subsequent ischemia was determined with triphenyltetrazolium. With PC, 55% of the aged heart after ischemia was no longer viable. OKA administered before or after ischemia reduced this ischemia-induced cellular death by 29%. Without PC, OKA reduced viability 18% only when present before and after the ischemic episode. OKA in the ischemic young heart during reperfusion reduced the loss of viability 31%. The Protein Phosphatase 2A (PP2A) activity was found to be up to 82% greater in ventricular myocardium of aged rats. In conclusion, aging-induced changes in protein dephosphorylation may be one mechanism reducing the manifestation of preconditioning in the aged heart.

Brief apnea induces myocardial ischemic tolerance by an opioid-insensitive mechanism.

BACKGROUND: Intermittent brief "preconditioning" (PC) ischemia has been shown to render the heart resistant to a subsequent sustained ischemic insult, in part through an opioid-dependent mechanism. Using the rabbit model, we tested the hypothesis that intermittent in vivo apnea elicits a cardioprotective response similar to that achieved with conventional PC ischemia. In addition, we sought to determine if infarct size reduction seen in this model was stimulated via opioid receptor activation. METHODS: Anesthetized, intubated rabbits (n=35) were randomized to receive three 4.5-min bouts of apnea interspersed with 5 min normal ventilation or time-matched standard ventilation (controls). Upon completion of the in vivo PC/control period, the hearts were excised and assessed for ischemic tolerance on a modified Langendorff apparatus (40 min global ischemia+2h reperfusion). To assess the contribution of opioid receptor stimulation, two additional control and PC groups received the nonspecific opioid antagonist naloxone (10 mg/kg) prior to the in vivo intervention phase. Infarct size (delineated by tetrazoliam staining and expressed as a percentage of the left ventricle [LV]) was compared among the four groups by ANOVA. RESULTS: Infarct size was significantly reduced in hearts that received antecedent apneic PC when compared with controls (63+/-5% vs. 34+/-8%) of the LV, respectively; P<.05). Pretreatment with naloxone had no significant effect on infarct size in nonpreconditioned hearts (80+/-6%) and did not inhibit the protective effects of apnea-induced PC (52+/-10% in naloxone+PC group). CONCLUSIONS: Intermittent apnea evokes significant myocardial ischemic tolerance through an opioid-insensitive mechanism.

Early death due to severe organophosphate poisoning is a centrally mediated process.

OBJECTIVE: To distinguish whether early death from severe organophosphate (OP) poisoning with dichlorvos is mediated through peripheral or central nervous system (CNS) actions. METHODS: Wistar rats (n = 72) were randomized to pretreatment with either: normal saline (controls), peripheral anticholinergics (glycopyrrolate [low, medium, or high dose] or nebulized ipratropium bromide), or CNS + peripherally acting anticholinergics (diphenhydramine, nebulized atropine, or injected atropine). All treatments were given prior to a subcutaneous injection of 25 mg/kg dichlorvos (n = 8 per group). Survival was assessed at 10 minutes (early death) and 24 hours (delayed death). Kaplan-Meier (95% confidence intervals [95% CIs]) and chi-squared analysis was then performed to determine differences between treatments. RESULTS: Regardless of treatment, all animals exhibited profound nicotinic effects (fasciculations) without obvious seizures within 2 minutes of poisoning. In rats pretreated with peripherally acting agents, the fasciculations were rapidly followed by reduced motor activity, sedation, and death. Mortality at 10 minutes for saline controls, glycopyrrolate, and ipratropium was 88%, 96%, and 100%, respectively. The single control animal surviving beyond 10 minutes went on to develop peripheral cholinergic manifestations, including hypersalivation, urination, and defecation. Only one of 24 animals treated with injected atropine, nebulized atropine, or diphenhydramine died during the early phase of poisoning; all others survived to 24 hours (p < 0.01). CONCLUSIONS: Death in acute, severe OP poisoning is prevented by pretreatment with anticholinergic agents that cross the blood-brain barrier, but not by agents with only peripheral actions. Early death due to OP poisoning appears to be a centrally mediated process.

Prevention of descending pneumonia in rts with perflubron-delivered tobramycin.

OBJECTIVES: Patients undergoing emergent endotracheal intubation are at increased risk for developing pneumonia. Although numerous strategies have been investigated to reduce ventilator-associated pneumonia (VAP), the incidence of VAP and its associated mortality remains high. This investigation tested the hypothesis that LiquiVent (Alliance Pharmaceutical, San Diego, CA-LV) delivered antibiotics (via spray-dried microspheres-SDM) would improve survival in a rat model of descending gram-negative pneumonia. METHODS: Wistar rats (n = 49) were randomized to receive prophylaxis with 1). nothing (controls); 2). intramuscular (IM) tobramycin, 3). intratracheal LV plus SDM shells (vehicle), 4). intratracheal LV plus SDM shells plus IM tobramycin, or 5). intratracheal LV plus SDM containing 1 mg/kg of tobramycin. All interventions were given 24 hours before a bacterial challenge with 10(8) colony-forming units of intratracheal Klebsiella pneumoniae. Mortality at ten days was the sole outcome measure. Survival in individual groups was compared with controls by Fisher's exact test with Bonferroni correction for multiple comparisons. RESULTS: All animals in the control group died of pneumonia within ten days of bacterial inoculation (0% survival). Prophylaxis with either IM tobramycin or SDM vehicle plus IM tobramycin provided no protection (0% survival). This is in sharp contrast to the cohort receiving pretreatment with tobramycin-containing SDM delivered via LV, in which 60% of the animals survived to study completion (p < 0.05). CONCLUSIONS: Prophylaxis with SDM containing antibiotics delivered in low-dose LV provided significant protection in a rat model of descending gram-negative pneumonia. These data support the hypothesis that perfluorocarbon-delivered intratracheal antimicrobials may be useful in the prevention of VAP.

Diphenhydramine as a protective agent in a rat model of acute, lethal organophosphate poisoning.

OBJECTIVE: To evaluate the effects of diphenhydramine chloride (DPH) on mortality in a rat model of acute, severe organophosphate poisoning (OP). METHODS: Wistar rats (n = 40) were randomized to pretreatment with either normal saline (controls), 5 mg/kg atropine, 3 mg/kg DPH, 15 mg/kg DPH, or 30 mg/kg DPH given as a single intramuscular injection 5 minutes prior to a subcutaneous injection of 25 mg/kg dichlorvos (n = 8 per group). The primary endpoint was 10-minute survival. Survival at 24 hours was a secondary endpoint. Comparison of survival rates between groups was carried out by ANOVA and the Student-Newman-Keuls test. RESULTS: Dichlorvos exposure resulted in profound fasciculations within 2 minutes of injection in all cohorts. In controls, fasciculations were followed by respiratory arrest within 10 minutes (0% survival). The rats receiving atropine pre-treatment exhibited similar fasciculations (nicotinic effects) without subsequent respiratory arrest, resulting in a significant improvement in survival (88%, p < 0.001). The DPH-treated rats exhibited a significant dose-dependent reduction in mortality, with the 3 mg/kg, 15 mg/kg, and 30 mg/kg groups demonstrating 0%, 25%, and 100% survival, respectively. There was no additional mortality between 10 minutes and 24 hours in any group. There was no significant difference in survival between the high-dose DPH and the atropine groups. CONCLUSIONS: Diphenhydramine chloride significantly reduced mortality in rats with acute, severe dichlorvos exposure.

Diazepam inhibits organophosphate-induced central respiratory depression.

OBJECTIVES: Current evidence suggests that mortality from acute organophosphate (OP) poisoning is partially mediated through central nervous system (CNS) respiratory center depression (CRD). However, the exact mechanism of OP-induced CRD is unknown. In these studies, the authors investigated the hypothesis that OP-induced CRD is the result of overstimulation of CNS respiratory centers. METHODS: Wistar rats received prophylaxis with either normal saline (controls), atropine, the peripherally acting anticholinergics glycopyrrolate (GLYC), ipratropium bromide (IB), or the CNS respiratory center attenuator diazepam. To determine if a dual CNS/peripheral cholinergic mechanism is responsible for animal death, two additional groups received combination treatment with diazepam plus either IB or GLYC. All treatments were completed 5 minutes before OP with subcutaneous dichlorvos. Differences in 10-minute and 24-hour mortality were assessed by the Fisher exact test. RESULTS: Dichlorvos poisoning resulted in profound fasciculations without obvious seizure in all cohorts. In controls and animals treated with peripherally acting anticholinergics, fasciculations were followed by sedation and respiratory arrest (0% 10-minute survival in all cohorts). In contrast, pretreatment with either atropine or diazepam significantly improved 10-minute survival (100% and 44%, respectively). Although GLYC or IB afforded no protection when given alone, when delivered in conjunction with diazepam, the combination significantly improved survival (both groups 88% at 24 hours), suggesting a dual CNS/pulmonary muscarinic mechanism of lethality. CONCLUSIONS: The central respiratory depressant diazepam paradoxically attenuates organophosphate-induced respiratory depression, and when combined with peripherally acting anticholinergic agents, reduces mortality in a rat model of severe acute OP poisoning.

Delta opiates increase ischemic tolerance in isolated rabbit jejunum.

UNLABELLED: Mammalian hibernation is mediated by humoral agonists of the delta opioid receptor (DOR). Moreover, transfer of either humoral or synthetic DOR agonists to non-hibernators reportedly induces a state of improved myocardial ischemic tolerance. OBJECTIVE: To determine whether the DOR agonist D-Ala 2, D-Leu 5, enkephalin (DADLE) similarly elicits protection in noncardiac-i.e., mesenteric-tissue. METHODS: In Protocols 1 and 2, the authors developed and characterized an in vitro model of mesenteric ischemia/reperfusion in isolated rabbit jejunum by documenting the effect of increasing ischemic duration (0 to 120 minutes) and the relative importance of glucose and/or oxygen deprivation on the evolution of jejunal injury. In Protocol 3, jejunal segments were randomized to receive either no treatment (controls) or 15 minutes of pretreatment with 1 microM DADLE, followed by 60 minutes of simulated ischemia and 30 minutes of reperfusion. Jejunal injury was quantified by repeated, time-matched assessment of peak contractile force evoked by 1 microM acetylcholine (all protocols) and delineation of tissue necrosis (Protocol 1). RESULTS: Development of significant jejunal injury required combined oxygen/glucose deprivation. Moreover, there was a direct relationship between ischemic duration and tissue injury, and a significant inverse correlation between reperfusion contractile force (% of baseline) and the extent of smooth muscle necrosis (r(2) = 0.87; p < 0.01). Most notably, mesenteric ischemia/reperfusion injury was attenuated by DADLE: reperfusion contractile force was 47 +/- 5% versus 36 +/- 5% in DADLE-treated versus control segments (p < 0.01). CONCLUSIONS: Treatment with the delta opioid agonist DADLE increases ischemic tolerance of isolated rabbit jejunum.

Generalizability of a simple approach for predicting hospital admission from an emergency department.

OBJECTIVES: The objective was to test the generalizability, across a range of hospital sizes and demographics, of a previously developed method for predicting and aggregating, in real time, the probabilities that emergency department (ED) patients will be admitted to a hospital inpatient unit. METHODS: Logistic regression models were developed that estimate inpatient admission probabilities of each patient upon entering an ED. The models were based on retrospective development (n = 4,000 to 5,000 ED visits) and validation (n = 1,000 to 2,000 ED visits) data sets from four heterogeneous hospitals. Model performance was evaluated using retrospective test data sets (n = 1,000 to 2,000 ED visits). For one hospital the developed model also was applied prospectively to a test data set (n = 910 ED visits) coded by triage nurses in real time, to compare results to those from the retrospective single investigator-coded test data set. RESULTS: The prediction models for each hospital performed reasonably well and typically involved just a few simple-to-collect variables, which differed for each hospital. Areas under receiver operating characteristic curves (AUC) ranged from 0.80 to 0.89, R(2) correlation coefficients between predicted and actual daily admissions ranged from 0.58 to 0.90, and Hosmer-Lemeshow goodness-of-fit statistics of model accuracy had p > 0.01 with one exception. Data coded prospectively by triage nurses produced comparable results. CONCLUSIONS: The accuracy of regression models to predict ED patient admission likelihood was shown to be generalizable across hospitals of different sizes, populations, and administrative structures. Each hospital used a unique combination of predictive factors that may reflect these differences. This approach performed equally well when hospital staff coded patient data in real time versus the research team retrospectively.

Low level bacterial endotoxin activates two distinct signaling pathways in human peripheral blood mononuclear cells.

BACKGROUND: Bacterial endotoxin, long recognized as a potent pro-inflammatory mediator in acute infectious processes, has more recently been identified as a risk factor for atherosclerosis and other cardiovascular diseases. When endotoxin enters the bloodstream, one of the first cells activated is the circulating monocyte, which exhibits a wide range of pro-inflammatory responses. METHODS: We studied the effect of low doses of E. coli LPS on IL-8 release and superoxide formation by freshly isolated human peripheral blood mononuclear cells (PBMC). RESULTS: IL-8 release was consistently detectable at 10 pg/ml of endotoxin, reaching a maximum at 1 ng/ml, and was exclusively produced by monocytes; the lymphocytes neither produced IL-8, nor affected monocyte IL-8 release. Superoxide production was detectable at 30 pg/ml of endotoxin, reaching a maximum at 3 ng/ml. Peak respiratory burst activity was seen at 15-20 min, and superoxide levels returned to baseline by 1 h. IL-8 release was dependent on both membrane-associated CD14 (mCD14) and Toll-like receptor 4 (TLR4. Superoxide production was dependent on the presence of LBP, but was not significantly affected by a blocking antibody to TLR4. Moreover, treatment with lovastatin inhibited LPS-dependent IL-8 release and superoxide production. CONCLUSIONS: These findings suggest that IL-8 release and the respiratory burst are regulated by distinct endotoxin-dependent signaling pathways in PBMC in low level of endotoxin exposure. Selectively modulating these pathways could lead to new approaches to treat chronic inflammatory diseases, such as atherosclerosis, while preserving the capacity of monocytes to respond to acute bacterial infections.

Exercise enhances myocardial ischemic tolerance via an opioid receptor-dependent mechanism.

Exercise increases serum opioid levels and improves cardiovascular health. Here we tested the hypothesis that opioids contribute to the acute cardioprotective effects of exercise using a rat model of exercise-induced cardioprotection. For the standard protocol, rats were randomized to 4 days of treadmill training and 1 day of vigorous exercise (day 5), or to a sham exercise control group. On day 6, animals were killed, and global myocardial ischemic tolerance was assessed on a modified Langendorff apparatus. Twenty minutes of ischemia followed by 3 h of reperfusion resulted in a mean infarct size of 42 +/- 4% in hearts from sham exercise controls and 21 +/- 3% (P < 0.001) in the exercised group. The cardioprotective effects of exercise were gone by 5 days after the final exercise period. To determine the role of opioid receptors in exercise-induced cardioprotection, rats were exercised according to the standard protocol; however, just before exercise on days 4 and 5, rats were injected subcutaneously with 10 mg/kg of the opioid receptor antagonist naltrexone. Similar injections were performed in the sham exercise control group. Naltrexone had no significant effect on baseline myocardial ischemic tolerance in controls (infarct size 43 +/- 4%). In contrast, naltrexone treatment completely blocked the cardioprotective effect of exercise (infarct size 40 +/- 5%). Exercise was also associated with an early increase in myocardial mRNA levels for several opioid system genes and with sustained changes in a number of genes that regulate inflammation and apoptosis. These findings demonstrate that the acute cardioprotective effects of exercise are mediated, at least in part, through opioid receptor-dependent mechanisms that may include changes in gene expression.

Met5-enkephalin-Arg6-Phe7 (MEAP): a cardioprotective hormonal opioid.

BACKGROUND: Acute myocardial ischemia is an important cause of morbidity and mortality worldwide. The heart and other organs can be rendered more resistant to the deleterious effects of ischemia through a variety of preconditioning strategies, including treadmill exercise and brief ischemia of skeletal muscle. Some of the beneficial effects of these preconditioning strategies appear to be mediated by as-of-yet unidentified hormonal opioids. OBJECTIVES: To test the hypothesis that endogenous opioids of the enkephalin class are capable of improving ischemic tolerance and acting in a hormonal manner. METHODS: In phase one of the investigation, the authors assessed the cardioprotective potential of all four known enkephalins. This was achieved by subjecting isolated buffer-perfused rabbit hearts to a 25-minute period of test ischemia and two hours of reperfusion (protocol 1) after receiving treatment with either saline vehicle (controls) or increasing concentrations of purified enkephalins. On the basis of results from these initial studies, the authors performed additional experiments (protocol 2) to determine whether Met5-enkephalin-Arg6-Phe7 (MEAP) could be absorbed from skeletal muscle and exert a cardioprotective effect. Specifically, MEAP or vehicle (controls) was given intramuscularly 24 hours before the hearts were harvested. A similar assessment of ischemic tolerance as described in protocol 1 was then performed. Postischemic myocardial viability (infarct size) was assessed in all cases by triphenyltetrazolium chloride (TTC) staining. Hemodynamic parameters and infarct sizes for concentration-dependence studies were compared by two-way analysis of variance, and infarct sizes from protocol 2 studies were compared by using Student's t-test (significance set at p < or = 0.05). RESULTS: Mean infarct size in control hearts (+/- SEM) was 33% (+/- 4%) and 36% (+/- 6%) for protocol 1 and 2, respectively. Of the four enkephalins tested in protocol 1, only MEAP treatment showed a tendency toward cardioprotection. Interestingly, an alternative enkephalin, methionine5-enkephalin-Arg6-Gly7-Leu8, tended to exert an injurious effect. In protocol 2, MEAP treatment 24 hours before ischemia significantly reduced infarct size (14% +/- 4%) compared with controls, suggesting that it can be released from muscle and exert a distant cardioprotective effect. CONCLUSIONS: When given either directly to the heart or absorbed from a distant tissue, MEAP induces cardioprotection, supporting the hypothesis that it can act as a hormonal modulator of ischemic tolerance.

Multiple centrally acting antidotes protect against severe organophosphate toxicity.

BACKGROUND: Accumulation of acetylcholine in the central nervous system is believed to account for the rapid lethality of organophosphate pesticides and chemical nerve agents. Diazepam is known to supplement atropine therapy, but its specific mechanism of action is uncertain. OBJECTIVES: To test four centrally acting agents for early antidotal efficacy in severe dichlorvos poisoning in the murine model. METHODS: The up-and-down method was used to dose four candidate antidotes: diazepam, xylazine, morphine, and ketamine. Antidotes were administered subcutaneously to unsedated adult Sprague-Dawley rats who were pretreated with 3 mg/kg intraperitoneal glycopyrrolate. All animals received 20 mg/kg of dichlorvos subcutaneously 5 minutes later. A blinded observer adjudicated the outcomes of 10-minute mortality and survival time. RESULTS: All animals pretreated with either no antidote (8/8 deaths) or glycopyrrolate alone (8/8) died within 10 minutes of dichlorvos injection. Pretreatment with diazepam (3/9 deaths), or xylazine (3/9), decreased lethality substantially (Fisher p = 0.007; median effective doses, 0.12 mg/kg and 3.0 mg/kg, respectively). Intermediate doses of morphine (3.1 to 5.5 mg/kg) resulted in survival, but higher doses did not, presumably because of excessive respiratory depression (7/11 deaths; p = 0.09). Ketamine (7/8 deaths) was ineffective as an antidote. Survival times also were prolonged in the diazepam and xylazine groups (log-rank p < 0.001) and, to a lesser degree, the morphine group (p = 0.07). CONCLUSIONS: Doses of diazepam, xylazine, and morphine below those used for deep sedation protect against severe dichlorvos poisoning, implying that several distinct central mechanisms are each sufficient to avert lethality. These findings suggest new possibilities for prophylaxis or therapy.

Cardioprotection 'outside the box'--the evolving paradigm of remote preconditioning.

Conventional ischemic preconditioning is the phenomenon whereby brief episodes of myocardial ischemia render the ischemic territory resistant to a subsequent, sustained ischemic insult. A growing body of evidence further indicates that brief ischemia applied in distant organs and tissues can also protect naïve, virgin myocardium from ischemic injury. In this review, we describe the initial observations that provided the impetus for the study of 'remote preconditioning', and summarize our current knowledge of the three facets of 'preconditioning at a distance' --intra-cardiac, inter-organ and transferred inter-cardiac preconditioning.