Biomedical subjects
A H Harken
Publications and source records attributed to A H Harken.
Neutrophils contribute to TNF induced myocardial tolerance to ischaemia.
Sublethal endotoxin (ETX) pretreatment of rats induces protection from cardiac ischaemia-reperfusion injury. This protective state is associated with increased endogenous myocardial catalase activity. Since tumour necrosis factor (TNF) is one mediator of ETX effects, we hypothesized that (TNF) pretreatment of the rat (30 micrograms/kg ip) 36 h prior to cardiac ischaemia-reperfusion could induce myocardial protection. We found that TNF administration increased both myocardial tolerance to ischaemia reperfusion injury (modified Langendorff, buffer perfusion, global, normothermic ischaemia) and myocardial catalase activity at 36 h. Moreover, we found that 6 h after TNF administration, myocardial hydrogen peroxide (H2O2, assessed by aminotriazole-H2O2 inactivation of catalase) and myocardial neutrophil accumulation (assessed by histology) were both increased. When neutrophil function was inhibited either by neutrophil depletion (vinblastine) or by ibuprofen treatments of the rat before TNF, the protection previously apparent at 36 h was blocked. We conclude that TNF can induce myocardial resistance to ischaemia reperfusion injury. This protection is related to prior tissue neutrophil accumulation and concomitant increases in H2O2 levels.
Platelet activating factor alters receptor-coupled function in the isolated perfused rat heart.
Sepsis induces primary myocardial dysfunction. Yet, both hyper- and hypodynamic cardiac states characterize the sepsis syndrome, suggesting a modulatory role of septic mediators. Platelet activating factor (PAF), implicated in the pathogenesis of sepsis, is an endogenous phospholipid with diverse intracellular and extracellular effects. The purpose of this study was to investigate the influence of PAF (1) upon basal mechanical function of the heart, (2) upon receptor-coupled function of the heart, and (3) on basal and stimulated myocardial function at differing concentrations. In order to focus on the relationship between PAF and cardiac mechanical function, rat hearts were isolated and crystalloid perfused using a modified Langendorf preparation. Separate hearts received intracoronary vehicle (5% ethanol, 2.5% BSA) or PAF (20 or 40 microM) as a bolus, followed 10 min later by 0.25 microM isoproterenol (beta-receptor agonist) infusion over 3 min. Both 20 and 40 microM PAF produced a rapid decrease in rate pressure product (RPP = HR X LVDPmax) relative to control (P < 0.05). The depressive effect of PAF upon basal myocardial function did not persist and by 10 min RPP was not different (P > 0.05) among the groups. Isoproterenol infusion increased (P < 0.05) RPP in all groups. However, hearts pretreated with 20 microM PAF demonstrated a greater (P < 0.05) response to beta-adrenergic stimulation relative to vehicle-pretreated controls. This amplified response to isoproterenol was not observed with pretreatment at a higher concentration of PAF (40 microM, P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Carl John Wiggers' visionary views on vivisection.
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Prophylaxis against perioperative cardiac ischemia-reperfusion injury.
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Cardiac 5'-nucleotidase activity increases with age and inversely relates to recovery from ischemia.
The metabolic basis for the enhanced tolerance of immature hearts to ischemia remains to be elucidated. Loss of high-energy phosphate nucleotides occurs during ischemia/reperfusion in mature (adult) hearts through the breakdown of adenosine triphosphate, diphosphate, and monophosphate (nondiffusible) to adenosine (freely diffusible). However, previous work has shown that after ischemia nondiffusible nucleotides are better retained by immature (neonatal) hearts than by mature hearts. The enzyme responsible for the conversion of adenosine monophosphate to adenosine is 5'-nucleotidase. We therefore hypothesized lower activity of this enzyme in neonatal than in adult myocardium. The purposes of this study were (1) to document 5'-nucleotidase activities in neonatal and adult rabbit myocardium and (2) to correlate differences of 5'-nucleotidase activity with functional recovery from ischemia. Neonatal (5- to 10-day-old) and adult (4- to 6-month-old) rabbit hearts were isolated and perfused (retrograde Langendorff). A left ventricular balloon measured functional parameters. Hearts were subjected to 20 minutes of global 37 degrees C ischemia and 10 minutes of reperfusion followed by freeze clamping. Tissue homogenates were assayed for 5'-nucleotidase by the linked formation of nicotinamide-adenine dinucleotide at 340 nm (Arkesteijn method). Postischemic recovery of developed pressure was 86% +/- 3% in neonates (n = 5) versus 38% +/- 3% in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). 5'-Nucleotidase activity was 4400 +/- 1208 nmol/min/gm in neonates (n = 5) versus 13,938 +/- 830 nmol/min/gm in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). We conclude that (1) 5'-nucleotidase activity is 68% lower in neonatal than in adult myocardium and (2) functional recovery after ischemia inversely relates to 5'-nucleotidase activity.
Repair of the torn, friable right atrium after decannulation.
We describe a technique to repair the torn, friable right atriotomy cannulation site. It results in a tension-free, hemostatic repair.
Primed neutrophils injure rat lung through a platelet-activating factor-dependent mechanism.
Bacterial lipopolysaccharide (LPS) promotes transient lung neutrophil sequestration. These LPS-primed neutrophils, when stimulated by an N-formyl peptide (FNLP), promote lung injury. We hypothesized that LPS-primed, FNLP-stimulated neutrophils promote lung injury through a platelet-activating factor (PAF)-dependent mechanism. Rats were pretreated with either saline or WEB2170, a PAF receptor antagonist (10 mg/kg po). One hour after pretreatment, rats were administered intraperitoneal LPS (salmonella typhimurium lipopolysaccharide, 500 micrograms/kg) followed 6 hr later by intravenous FNLP (250 micrograms/kg infused over 30 min). Two hours after the initiation of FNLP infusion, rats were sacrificed and assays were performed to measure: (1) lung neutrophil sequestration with myeloperoxidase (MPO) activity; (2) circulating neutrophil activation with nitroblue tetrazolium (NBT) staining, and (3) lung microvascular leak with 125I-albumin flux. We found that lung myeloperoxidase, circulating neutrophil NBT staining, and lung 125I-albumin flux were increased (P less than 0.05) in saline-pretreated LPS/FNLP rats, relative to control. While lung MPO remained increased (P less than 0.05) in WEB2170-pretreated LPS/FNLP rats, circulating neutrophil NBT and lung 125I-albumin flux were decreased (P less than 0.05) relative to those in saline-pretreated rats. We conclude that PAF mediates LPS/FNLP-induced neutrophil activation and lung injury, but is independent from lung neutrophil sequestration. Thus, lung neutrophil sequestration does not inevitably produce lung injury. Rather, neutrophils can accumulate in the lung without causing lung injury if neutrophil activation can be blocked.
Mechanisms of neutrophil-mediated tissue injury.
Neutrophil-mediated tissue injury (NMTI) is a prominent mechanism of host autodestruction. It is defined by a sequence of events including neutrophil adherence and sequestration, diapedesis, activation, and secretion of toxic compounds. Knowledge of this sequence is valuable because it outlines points at which intervention may be sought. A limitation of these studies comes in the misunderstanding and misapplication of the tests used to analyze these events. We now realize that neutrophil adherence, sequestration, diapedesis, and secretion of toxic compounds can each occur alone without promoting generalized tissue injury. NMTI is a normally localized process that has gone systemically awry. Influencing this system must be selective and controlled because the inflammatory system is a critical component of host defense. As we gain insight into the pathophysiology of NMTI, we hope to find new avenues for therapeutic intervention in critical care.
Reversible pulmonary hypertension secondary to mitral valvular disease as an indication for extracorporeal membrane oxygenation.
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FNLP injures endotoxin-primed rat lung by neutrophil-dependent and -independent mechanisms.
Bacterial lipopolysaccharide (LPS) and an N-formyl peptide, N-formyl-neoleucyl-leucyl-phenylalanine (FNLP), synergistically promote lung injury in rats as measured by 125I-labeled albumin flux. Concomitantly, neutrophils are sequestered in the lung. We hypothesized that LPS-FNLP-induced lung injury is mediated both by neutrophil-dependent and -independent mechanisms. Rats were depleted of circulating and marginating neutrophils with vinblastine. LPS-FNLP-induced lung protein leak was partially decreased in these neutrophil-depleted animals, although a component of lung injury remained. We hypothesized that LPS-FNLP-induced lung injury was also mediated by xanthine oxidase (XO). Rats were fed a tungsten-enriched diet that inactivates molybdenum-dependent oxidase systems. LPS-FNLP-induced lung leak was partially decreased in these animals as well. When tungsten-fed rats were also neutrophil depleted with vinblastine, no increase in 125I-albumin flux was observed in response to LPS-FNLP. In parallel experiments, lungs from vinblastine-pretreated rats were isolated and perfused. FNLP infusion into the LPS-primed, crystalloid-perfused lungs caused increased 125I-albumin flux, which was prevented by oxidase inhibition. We conclude that LPS-FNLP-induced lung injury is both neutrophil mediated and neutrophil independent. The nonneutrophil component of the LPS-FNLP-induced lung injury appears to be pulmonary XO derived and dependent.
Hypovolemic shock promotes neutrophil sequestration in lungs by a xanthine oxidase-related mechanism.
Our results suggest that xanthine oxidase (XO) contributes to lung neutrophil sequestration in hypovolemic shock. Catheterized rats subjected to shock by phlebotomy (approximately 30% blood loss) had decreased mean arterial blood pressures (P less than 0.05) and increased (P less than 0.05) lung myeloperoxidase (MPO) activities (indicative of lung neutrophil accumulation) compared with sham-treated normotensive rats. In contrast, rats depleted of lung and plasma XO activity by tungsten diet before phlebotomy had decreased (P less than 0.05) lung MPO activities compared with phlebotomized rats fed regular diets.
Marginating neutrophils are reversibly adherent to normal lung endothelium.
Neutrophils have been implicated in the pathogenesis of several inflammatory lung disorders including asthma, emphysema, and adult respiratory distress syndrome. The precursors of these destructive cells are thought to be marginating neutrophils that, although intravascular, remain intimately associated with endothelium, resisting the shearing forces of flowing blood. The purposes of this study were (1) to examine a method for quantitating marginating lung neutrophils, (2) to assess the adherence of marginating neutrophils to normal lung endothelium, and (3) to determine the reversibility of neutrophil-endothelial cell adherence. Rats were anesthetized and ventilated, and their lungs were exposed through a median sternotomy. The left lung was tied off with blood in situ and the right lung was perfused intraarterially with colloid for 2 minutes. In separate experiments, both left and right lungs were perfused intraarterially with colloid for 25 minutes. Myeloperoxidase, a neutrophil granule enzyme, was related to lung neutrophils. Dithionite-sensitive optical density (DSOD) was related to lung hemoglobin. Marginating lung neutrophils were quantitated by measuring the peroxidase activity of normal blood-perfused lung (myeloperoxidase assay) and subtracting from it the fraction of activity corresponding to the lung blood content (DSOD). The marginating neutrophil pool was identified by 2.1 units myeloperoxidase (5 x 10(6) neutrophils) per gm wet lung. Although the marginating pool was depleted by 54% during 2 minutes of lung colloid perfusion, lung erythrocytes (DSOD) were decreased by a significantly greater 93% (p less than 0.05). Lungs perfused with colloid for 25 minutes had negligible remaining myeloperoxidase activity. We conclude that (1) marginating lung neutrophils can be quantitated with the myeloperoxidase and DSOD assays, (2) marginating neutrophils are relatively adherent to normal lung endothelium compared with intravascular erythrocytes, and (3) the adherence of marginating neutrophils is fully reversible.
The role of platelet activating factor and its antagonists in shock, sepsis and multiple organ failure.
PAF has been implicated as a mediator of shock, sepsis and MOF. The results of experimental data demonstrate that PAF induces changes characteristic of endotoxemia and sepsis, including systemic hypotension and diffuse microvascular leakage. These effects are prevented by PAF antagonists. PAF induces many of the characteristic changes of MOF, including functional impairment in the lung, kidney, gastrointestinal tract and heart. PAF antagonists will inhibit these adverse effects. PAF antagonists are now being manufactured by a number of pharmaceutical companies studying the beneficial effects of PAF antagonists in human disease. Data from these studies promise valuable information with significant clinical relevance to the practicing surgeon.
Pretreatment with a nontoxic derivative of endotoxin induces functional protection against cardiac ischemia/reperfusion injury.
We hypothesized that low-dose pretreatment of an intact animal with a nontoxic derivative of endotoxin, monophosphoryl lipid A (MPL), would induce protection against cardiac ischemia/reperfusion (I/R) injury. The purposes of this study were to investigate whether MPL pretreatment would induce functional protection against cardiac I/R injury, to delineate the temporal induction of protection, and to examine antioxidant enzyme induction as a mechanism of protection. Rats were administered a 5 mg/kg dose of MPL at 2 hours and 24 hours before a 25-minute, global, 37 degrees C ischemic insult followed by reperfusion (modified Langendorff). At 40 minutes of reperfusion, ventricular function was assessed (ventricular balloon; developed pressure, rate of contraction, rate of relaxation). Hearts from rats pretreated with MPL 24 hours before isolation exhibited preservation of ventricular function (p less than 0.05). After I/R, hearts from rats pretreated with MPL 24 hours before isolation had increased (p less than 0.05) catalase activity compared to saline pretreated controls and rats pretreated with MPL 2 hours before isolation. We conclude that (1) pretreatment with MPL induces functional protection against cardiac I/R injury, (2) protection (not evident at 2 hours) is maximal at 24 hours, suggesting enzyme induction, and (3) increased catalase activity correlates with the functional protection.
Reversal of protamine-induced catastrophic pulmonary vasoconstriction by prostaglandin E1.
A case of catastrophic pulmonary vasoconstriction occurring after cardiopulmonary bypass after protamine reversal of heparin treated successfully with intravenous prostaglandin E1 is reported. Systemic hypotension was counteracted by epinephrine given through the left atrium. Protamine-heparin reactions are reviewed and a pathophysiological mechanism for the beneficial effect seen with prostaglandin E1 is proposed.
Iron depletion or chelation reduces ischemia/reperfusion-induced edema in gerbil brains.
Since hydrogen peroxide (H2O2) can react with ferrous iron (FE++) to form the more toxic hydroxyl radical (OH) in vitro, and since H2O2 is generated brain xanthine oxidase (XO) during ischemia/reperfusion (I/R), we hypothesized that gerbils depleted of iron by dietary restriction or treated with iron chelators would be less susceptible to I/R injury. We found that gerbils fed a low iron diet for 8 weeks had decreased brain and serum iron levels, less neurologic deficits, and decreased brain edema after temporary unilateral carotid ligation (ischemia) and then reperfusion than gerbils fed a control standard iron diet. In addition, brains from gerbils treated with iron-free deferoxamine (an iron chelator), but not iron-loaded deferoxamine, had decreased (P less than .05) brain edema following ischemia and reperfusion. The results indicate that iron may contribute to cerebral ischemia/reperfusion damage.
Induction of endogenous tissue antioxidant enzyme activity attenuates myocardial reperfusion injury.
Efforts to reduce reperfusion injury have focused on exogenous therapies; however, endogenous attenuation of reperfusion injury can be induced by a single sublethal dose of endotoxin (ETX) prior to ischemia. The purposes of this study were to investigate (i) the early neutrophil-endothelial (PMN-EC) adherence, (ii) the associated myocardial oxidant stress, (iii) the relationship of oxidant stress to antioxidant enzyme activity, and (iv) the correlation of increased antioxidant enzyme activity to myocardial recovery following ischemia/reperfusion (I-R) injury at 36 hr. Rats were administered a sublethal dose (2% of LD50) of endotoxin (500 micrograms/kg, ip, Salmonella typhimurium). At 6 hr, myocardial neutrophil accumulation (histology), hydrogen peroxide (H2O2) levels, and myocardial tissue glutathione (glutathione and oxidized glutathione) levels were determined. At 24 hr myocardial tissue glutathione levels and catalase (CAT) activity were assayed. At 36 hr, myocardial tissue superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, and glucose-6-phosphate dehydrogenase (G-6-PD) were assayed. At 36 hr, hearts were subjected to a standard (20 min, global, 37 degrees C) ischemic insult followed by reperfusion. At 40 min of reperfusion, ventricular function was assessed (ventricular balloon; ventricular developed pressure +dP/dt, and -dP/dt).(ABSTRACT TRUNCATED AT 250 WORDS)