Wound healing is accelerated by agonists of adenosine A2 (G alpha s-linked) receptors.

The complete healing of wounds is the final step in a highly regulated response to injury. Although many of the molecular mediators and cellular events of healing are known, their manipulation for the enhancement and acceleration of wound closure has not proven practical as yet. We and others have established that adenosine is a potent regulator of the inflammatory response, which is a component of wound healing. We now report that ligation of the G alpha s-linked adenosine receptors on the cells of an artificial wound dramatically alters the kinetics of wound closure. Excisional wound closure in normal, healthy mice was significantly accelerated by topical application of the specific A2A receptor agonist CGS-21680 (50% closure by day 2 in A2 receptor antagonists. In rats rendered diabetic (streptozotocin-induced diabetes mellitus) wound healing was impaired as compared to nondiabetic rats; CGS-21680 significantly increased the rate of wound healing in both nondiabetic and diabetic rats. Indeed, the rate of wound healing in the CGS-21680-treated diabetic rats was greater than or equal to that observed in untreated normal rats. These results appear to constitute the first evidence that a small molecule, such as an adenosine receptor agonist, accelerates wound healing in both normal animals and in animals with impaired wound healing.

Human neutrophil elastase modulates platelet function by limited proteolysis of membrane glycoproteins.

During blood coagulation human polymorphonuclear leukocytes release elastase in amounts that can exceed 100 nmol/liter. We therefore studied the effect of elastase on platelet structure and function. Physiologic concentrations of elastase specifically inhibited thrombin-induced platelet aggregation and ristocetin-induced agglutination of washed platelets in a time- and dose-dependent manner. This was associated with a decrease in the number of high affinity thrombin binding sites on the platelet surface (analysis by "Ligand" program) from 31 per platelet to 12 per platelet (P less than 0.05). As analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, treatment of 3H-labeled platelets with elastase resulted in a decrease in the percent glycoprotein at 130,000-150,000 Mr = and an increase in the percent protein at Mr = 102,000. The supernatant from elastase-treated platelets contained a Mr = 88,000 glycoprotein not found in the supernatant from untreated platelets. Immunoprecipitation studies with monoclonal antiglycoprotein Ib demonstrated that treatment of whole platelets with physiologic concentrations of elastase resulted in proteolytic cleavage of glycoprotein Ib. Elastase treatment of glycoprotein immunoisolated with monoclonal antiglycoprotein Ib antibody resulted in formation of a glycopeptide with the same electrophoretic mobility as the Mr = 102,000 membrane-related glycopeptide. In contrast, analysis by Western blot technique using antiglycoprotein IIb and IIIa antibodies demonstrated that elastase did not degrade glycoproteins IIb or IIIa. We conclude that elastase inhibition of thrombin-induced platelet stimulation is accompanied by (a) a reduction in the number of thrombin binding sites per platelet and (b) proteolysis of glycoprotein Ib.

Nitroglycerin stimulates synthesis of prostacyclin by cultured human endothelial cells.

Nitroglycerin (NTG), the agent most commonly used to treat acute angina pectoris, is a vasodilator whose mechanism of action remains unknown. We hypothesized that NTG might induce endothelial cells to synthesize prostacyclin (PGI(2)), a known vasodilator and inhibitor of platelet aggregation. Therefore, cultured human endothelial cells were incubated with NTG at various concentrations for 1-3 min. PGI(2) biologic activity in the endothelial cell supernates was assayed by inhibition of platelet aggregation in vitro. The concentration of 6-keto-PGF(1alpha), the stable hydrolysis product of PGI(2), was measured by specific radioimmunoassay.NTG alone significantly inhibited platelet aggregation and thromboxane A(2) synthesis only at suprapharmacologic concentrations (>/=1 mug/ml). However, when NTG at clinically attainable concentrations (0.1-10 ng/ml) was incubated with endothelial cells, the endothelial cell supernates inhibited platelet aggregation in a dose-dependent manner. The inhibitor was heat labile. Radioimmunoassay of the endothelial cell supernates for 6-keto-PGF(1alpha) demonstrated that NTG elicited dose-dependent increments in the synthesis of PGI(2) by endothelial cells, ranging from 13% at NTG 10 pg/ml to 63% at NTG 10 ng/ml (P < 0.01, n = 10). Pretreatment of endothelial cells with either aspirin (50 muM for 120 min) or the prostacyclin synthetase inhibitor 15-hydroperoxyarachidonic acid (20 mug/ml for 15 min) abolished production of the platelet inhibitory substance. Synergy between NTG and PGI(2) in the inhibition of platelet aggregation was not present at clinically attainable concentrations of NTG.Thus, NTG at clinically attainable concentrations causes a dose-dependent increase in PGI(2) synthesis by endothelial cells. If this phenomenon occurs in vivo, the PGI(2) produced could ameliorate myocardial ischemia by causing peripheral vasodilation and decreasing cardiac work, inhibiting platelet aggregation and thromboxane A(2) synthesis, and possibly reversing coronary artery vasospasm.

Adenosine: an endogenous inhibitor of neutrophil-mediated injury to endothelial cells.

Since adenosine and its analogue 2-chloroadenosine prevent neutrophils from generating superoxide anion in response to chemoattractants, we sought to determine whether these agents could inhibit neutrophil-mediated injury of endothelial cells. The chemoattractant N-formyl-methionyl-leucyl-phenylalanine (FMLP, 0.1 microM) enhanced the adherence of neutrophils to endothelial cells twofold (18 +/- 2% vs. 39 +/- 3% adherence, P less than 0.001) and caused substantial neutrophil-mediated injury to endothelial cells (2 +/- 2% vs. 39 +/- 4% cytotoxicity, P less than 0.001). 2-Chloroadenosine (10 microM) not only inhibited the adherence of stimulated neutrophils by 60% (24 +/- 2% adherence, P less than 0.001) but also diminished the cytotoxicity by 51% (20 +/- 4% cytotoxicity, P less than 0.002). Furthermore, depletion of endogenously released adenosine from the medium by adenosine deaminase-enhanced injury to endothelial cells by stimulated neutrophils (from 39 +/- 4% to 69 +/- 3% cytotoxicity, P less than 0.001). Indeed, in the presence of adenosine deaminase, even unstimulated neutrophils injured endothelial cells (19 +/- 4% vs. 2 +/- 2% cytotoxicity, P less than 0.001). These data indicate that engagement of adenosine receptors prevents both the adhesion of neutrophils and the injury they cause to endothelial cells. Adenosine inhibits injury provoked not only by cells that have been stimulated by chemoattractants but also by unstimulated cells. Based on this model of acute vascular damage we suggest that adenosine is not only a potent vasodilator, but plays the additional role of protecting vascular endothelium from damage by neutrophils.

Aspirin inhibits vascular plasminogen activator activity in vivo. Studies utilizing a new assay to quantify plasminogen activator activity.

Vascular or tissue-type plasminogen activator (TPA) is a key enzyme in physiologic fibrinolysis. To study the role of prostaglandins in modulating the synthesis and release of TPA in vivo, we prospectively studied the effect of aspirin (650 mg/d X 2) on TPA activity in 13 human subjects before and after 10 min of forearm venous occlusion. TPA activity was quantified by a newly developed enzyme-linked immunosorbent assay that both measures and differentiates between TPA and urokinase (UK)-like plasminogen activator activity. This assay is based on the observation that the concentration of alpha 2-plasmin inhibitor-plasmin complexes in Reptilase-clotted plasma increases linearly in proportion to the amount of activator added. Resting TPA activity was higher in women than in men (0.56 +/- 0.59 vs. 0.15 +/- 0.11 U/ml, P = 0.049). Venous occlusion induced an eightfold rise in TPA activity in women (to 4.5 U/ml, P = 0.006) and a 15-fold rise in men (to 2.28 U/ml, P = 0.004), whereas UK activity was not detected. Aspirin inhibited the rise in TPA activity after venous occlusion by 69% in men (P = 0.004) and 70% in women (P = 0.014). In contrast, aspirin had no effect on pre- or post-occlusion hematocrits or Factor VIII-related antigen levels. There was no correlation between plasma salicylate level and percentage inhibition of TPA. Neither exogenous aspirin (0-1 microgram/ml) nor salicylate (0-70 micrograms/ml) inhibited the generation of alpha 2-plasmin inhibitor-plasmin complexes by exogenous TPA or interfered with the assay system. We conclude that aspirin may have an antifibrinolytic effect in man that has not been previously described.

Colchicine alters the quantitative and qualitative display of selectins on endothelial cells and neutrophils.

Since colchicine-sensitive microtubules regulate the expression and topography of surface glycoproteins on a variety of cells, we sought evidence that colchicine interferes with neutrophil-endothelial interactions by altering the number and/or distribution of selectins on endothelial cells and neutrophils. Extremely low, prophylactic, concentrations of colchicine (IC50 = 3 nM) eliminated the E-selectin-mediated increment in endothelial adhesiveness for neutrophils in response to IL-1 (P < 0.001) or TNF alpha (P < 0.001) by changing the distribution, but not the number, of E-selectin molecules on the surface of the endothelial cells. Colchicine inhibited stimulated endothelial adhesiveness via its effects on microtubules since vinblastine, an agent which perturbs microtubule function by other mechanisms, diminished adhesiveness whereas the photoinactivated colchicine derivative gamma-lumicolchicine was inactive. Colchicine had no effect on cell viability. At higher, therapeutic, concentrations colchicine (IC50 = 300 nM, P < 0.001) also diminished the expression of L-selectin on the surface of neutrophils (but not lymphocytes) without affecting expression of the beta 2-integrin CD11b/CD18. In confirmation, L-selectin expression was strikingly reduced (relative to CD11b/CD18 expression) on neutrophils from two individuals who had ingested therapeutic doses of colchicine. These results suggest that colchicine may exert its prophylactic effects on cytokine-provoked inflammation by diminishing the qualitative expression of E-selectin on endothelium, and its therapeutic effects by diminishing the quantitative expression of L-selectin on neutrophils.

Effects of amlodipine on glomerular filtration, growth, and injury in experimental hypertension.

The objective of this study was to determine whether the calcium antagonist amlodipine could slow the progression of chronic renal disease. We examined the effects of amlodipine on kidney structure and function in two experimental models of hypertension. In the first study, adult, male Munich Wistar rats underwent uninephrectomy and were given weekly injections of desoxycorticosterone and 1% saline for drinking. Rats ingested normal chow or chow containing amlodipine for 8 weeks. The drug reduced systemic blood pressure, but glomerular filtration rate, kidney weight, proteinuria, and morphological evidence of glomerular injury were not affected. In the second study, male spontaneously hypertensive rats underwent uninephrectomy at 5 weeks of age and were followed for 6 months, during which they received no therapy or amlodipine. The drug dose was determined in preliminary studies to be the highest dose not associated with marked growth retardation. Again, although systemic blood pressure was significantly reduced by amlodipine, proteinuria and the prevalence of glomerulosclerosis were similar in amlodipine-treated and control spontaneously hypertensive rats. Micropuncture studies revealed that glomerular pressure remained elevated in amlodipine-treated spontaneously hypertensive rats. Kidney weight and glomerular volume were also similar in amlodipine-treated and control rats. Amlodipine also failed to inhibit platelet aggregation. Therefore, antihypertensive therapy with amlodipine fails to reduce glomerular pressure in spontaneously hypertensive rats as well as glomerular size and injury in spontaneously hypertension rats and desoxycorticosterone-salt hypertension. Although other dihydropyridine calcium antagonists have been found to reduce experimental glomerular injury, these data suggest that amlodipine may not prevent hypertensive nephrosclerosis.

Physician choices in the treatment of angina pectoris.

Uncertainty about optimal treatment for many diseases results in heterogeneous management by definition. It was hypothesized that identifiable characteristics in a physician's background would influence the management of any such condition and thereby explain some of this heterogeneity. A vignette describing a patient with new-onset angina and a questionnaire ascertaining individual physician characteristics and management preferences were sent to attending physicians and house staff in the Department of Medicine at New York University School of Medicine. Although physicians believed very strongly that the patient had angina on the basis of the history, there was no consensus about managing the hypothetic patient. The age of the physician was the single most important predictor of management, with the younger half of the sample more likely to hospitalize (p less than 0.001), less likely to prescribe nitroglycerin as a sole therapy (p less than 0.005), and more likely to prescribe beta blockers (p less than 0.005). The era in which a physician trains may determine practices that persist for a lifetime. These findings may have important implications for medical education and the quality and cost of medical care.

Quantitation of transient myocardial ischemia by digital, ambulatory electrocardiography.

Transient myocardial ischemia is more frequently silent than accompanied by angina. The frequency of ischemia varies markedly from day to day, so that in order to accurately define the total ischemic burden, it may be necessary to quantitate ischemic episodes for periods longer than 24 hours. Therefore, a programmable, digital device was developed for long-term, interactive, ambulatory monitoring of the electrocardiogram, which uses variations in a time-averaged ST level as an indicator of myocardial ischemia. The electrocardiographic signal is digitized at 256 Hz and analyzed by an algorithm. If ST depression is planar or downsloping and persists for more than 40 seconds, and if the ST depression is equal to or more than a user-programmed threshold, the device marks the onset of an ischemic event and times it. The algorithm has been validated by comparison of its analysis of the ST segment to human and computerized analyses of frequency-modulated Holter recordings and stress tests. To assess the feasibility and utility of long-term monitoring, patients with documented coronary artery disease were monitored continuously for 14-day periods. Of 26 patients enrolled, 8 completed a protocol for individualization of anti-ischemic therapy using transdermal nitroglycerin. Over 90% of ischemic episodes in this group of patients, all of whom had had a previous myocardial infarction, were silent. Treatment with 10 mg of transdermal nitroglycerin reduced the number of ischemic episodes by 59% and the duration of ischemia by 60% (p less than 0.001); there was no diminution in the effectiveness of treatment from week 1 to week 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential for real-time processing of the continuously monitored electrocardiogram in the detection, quantitation, and intervention of silent myocardial ischemia.

Current technology for monitoring and analyzing the ST segment allows for accurate description of ST-segment deviation, which in most cases is a valid measure of myocardial ischemia. In this article, the authors describe a new method that utilizes microprocessor analysis of the electrocardiogram to detect ST-segment deviation in ambulatory subjects. This technique results in the ability to characterize the total ischemic burden over long periods of time and to intervene acutely in order to treat myocardial ischemia and possibly to prevent complications of coronary artery disease.

Nonsteroidal antiinflammatory agents inhibit stimulated neutrophil adhesion to endothelium: adenosine dependent and independent mechanisms.

All nonsteroidal antiinflammatory drugs (NSAIDs) inhibit neutrophil aggregation (homotypic cell-cell adhesion) and do so without affecting expression of CD11b/CD18. Since the first step in acute inflammation is a critical interaction between neutrophils and the vascular endothelium (heterotypic cell-cell adhesion), we determined whether NSAIDs diminish the adherence of neutrophils to the endothelium. At antiinflammatory concentrations (0.5-5 mM) sodium salicylate, an NSAID that does not inhibit prostaglandin synthesis, inhibited stimulated but not unstimulated neutrophil adherence to endothelial cells (IC50 < 1 mM, P < 0.00001). Salicylates have previously been shown to inhibit oxidative phosphorylation and, predictably, sodium salicylate inhibited oxidative phosphorylation, as evidenced by depletion of ATP stores (875 +/- 75 pmol/10(6) PMN, [2.92 +/- 0.25 mM]) in stimulated (FMLP, 0.1 microM) but not resting neutrophils treated with antiinflammatory doses of sodium salicylate (EC50 = 1 mM, P < 0.00001). Indomethacin and piroxicam (10 and 30 microM) only minimally decreased ATP concentrations in stimulated and resting neutrophils. ATP is metabolized to adenosine, and we have previously demonstrated that both endogenously released (180-200 nM) and exogenous adenosine (IC50 = 250 nM) inhibit stimulated neutrophil adherence to endothelial cells. To determine whether the increased metabolism of ATP and the resultant increase in adenosine release were responsible for inhibition of neutrophil adhesion to endothelium, we determined whether addition of adenosine deaminase (ADA, 0.125 IU/ml), an enzyme that converts extracellular adenosine to its inactive metabolite, inosine, affected inhibition of neutrophil adhesion to endothelium by stimulated neutrophils. ADA significantly reversed inhibition of neutrophil adherence to endothelium by sodium salicylate (0.5-5 mM, P < 0.00001). This suggests that sodium salicylate inhibits neutrophil adherence by increasing adenosine release. Whereas indomethacin and piroxicam (10-50 microM) also inhibited stimulated neutrophil adherence to endothelial cells, ADA did not affect their inhibition of adherence. These studies demonstrate a heretofore unexpected antiinflammatory mechanism for salicylates: salicylates increase ATP hydrolysis and thereby enhance release of adenosine. Moreover, these data are consistent with the hypothesis that NSAIDs differ from one another with respect to their mechanisms of action.

The cardiomyopathy of Duchenne's muscular dystrophy and the function of dystrophin.

Duchenne's muscular dystrophy (DMD) is a common X-linked neuromuscular disease which predominantly affects skeletal and cardiac muscle. The absence of dystrophin, the metabolic defect that causes DMD, leads to a peculiar cardiomyopathy which initially affects the posterior wall of the left ventricle. We review evidence that dystrophin deficient myocytes become dystrophic in order of increasing axial stress upon the myocyte. Thus, dystrophin's function may be that of physically reinforcing the sarcolemma against the axial forces exerted upon the myocyte.

The introduction of ambulatory electrocardiographic monitoring for the diagnosis and management of myocardial ischemia.

We report on the introduction of a new technology and a new method for the management of chronic coronary artery disease into a managed care environment. The introduction incurred substantial resistance from subspecialty consultants, primary care physicians, and top management. Strategies were developed to overcome these resistances. Modification of the program as well as the development of incentives occurred. These measures continue to evolve. The program, to date, has achieved approximately 50% penetration. The demonstration of better health outcomes and financial savings will almost certainly temper the resistance encountered from all three groups identified.

Activator headgear therapy.

A method of treatment is described using an activator and cervical headgear simultaneously to correct malocclusions of the Class II, Division 1 type. The case reports of ten treated patients are used to demonstrate the effects of the application of this technique. Changes in the dentition and facial skeleton were analyzed and the significance of the different responses to the application of the same appliances assessed. The hypothesis proposing that a simultaneous application of both appliances may result in a number of desirable effects greater than that induced by each individual appliance is examined. The hypothetical basis for the application of this technique is partially substantiated by the clinical observations. Within a period of about 1 year, correction of the Class II molar occlusion to a Class I molar occlusion is obtained, with a simultaneous reduction of overbite and overjet. Skeletal changes were found to be variable and related to facial type and the rate of facial growth. Brachyfacial and mesofacial types responded most favorably to treatment. The most favorable effects were observed when there was a large quantitative mandibular growth and brachyfacial or mesofacial growth pattern. In dolichofacial types with a slow mandibular growth rate, mandibular rotation was found to be clockwise; cervical traction appears contraindicated, and a combination of activator with occipital medium to high pull is considered more appropriate.

Deep bite treatment in relation to mandibular growth rotation.

This paper illustrates some of the changes which occur during the treatment of Class II division 1 malocclusions complicated by a deep bite, and reviews the significance of these changes in relation to concepts of deep bite treatment. Particular reference is made to mandibular growth rotation and consequent differential tooth eruption in assessing factors involved in initial bite opening and consolidation of the opened bite. The cases shown illustrate that although an initial bite opening may occur by incisor intrusion and molar eruption, when viewed over a longer period of time rotational mandibular growth and associated differential eruption of teeth in which molars erupt more than incisors may be a more significant factor. Differential eruption which takes place in response to vertical condylar growth under guidance of the appliance would appear to be a significant factor in treatment of deep bite.

The effect of aspirin on the hemodynamic response to nitroglycerin.

The role of prostaglandins in mediating the hemodynamic response to nitroglycerin in vivo is controversial. To determine the effect of inhibiting prostaglandin production on the response to nitroglycerin, either placebo or aspirin (650 mg) was administered 1 hour prior to the administration of nitroglycerin (432 micrograms) sublingually to 40 healthy volunteers in a double-blind, randomized, cross-over study. Prior to nitroglycerin administration, blood pressure and pulse rate were determined noninvasively every 2 minutes until stable conditions were reached, and then after nitroglycerin administration determinations were made every 1 minute for the first 10 minutes, every 2 minutes for the next 10 minutes, and every 5 minutes until 30 minutes had elapsed. At peak response in the placebo study, nitroglycerin lowered systolic pressure from 117 +/- 10 to 111 +/- 10 mm Hg (p less than 0.0001). Unexpectedly, nitroglycerin increased diastolic pressure from 75 +/- 8 to 80 +/- 7 mm Hg (p less than 0.005), thus reducing pulse pressure significantly. Pulse rate after nitroglycerin increased from 72 +/- 11 to 85 +/- 14 (p less than 0.001). Aspirin slightly modified the pattern of response at 1 minute but altered neither the peak hemodynamic responses nor the areas under the time-pressure and time-pulse curves. Thus nitroglycerin-induced prostaglandin production does not play a major role in the systemic hemodynamic response to nitroglycerin in vivo.

Natriuretic peptides: physiology, therapeutic potential, and risk stratification in ischemic heart disease.

BACKGROUND: The natriuretic peptide family consists of four molecules that share significant amino acid sequence homologic characteristics and a looped motif. Atrial natriuretic peptide and brain natriuretic peptide are similar in their ability to promote natriuresis and diuresis, inhibit the renin-angiotensin-aldosterone axis, and act as vasodilators. Understanding of the actions of C-type natriuretic peptide and dendroaspis natriuretic peptide is incomplete, but these two new family members also act as vasodilators. Because of the rapid evolution of information about this peptide family, we reviewed the state of the art with respect to risk stratification and therapeutic ability. METHODS: English-language papers were identified by a MEDLINE database search covering 1966 through 1997 and supplemented with bibliographic references and texts. CONCLUSIONS: The natriuretic peptides are counterregulatory hormones with prognostically important levels. They are similarly upregulated in heart failure and counteract neurohormones that induce vasoconstriction and fluid retention. BNP may be the superior prognosticator for risk stratification after myocardial infarction and is independent of left ventricular ejection fraction. Lastly, experimental trials suggest that administration of exogenous natriuretic peptides or inhibitors of their catabolism to patients with ischemic heart disease may be clinically beneficial.

The urban emergency department: the issue of professional responsibility.

The urban emergency department is routinely asked to manage not only medical emergencies, but also a great variety of social emergencies. This situation is caused in part by budgetary constraints which prevent other agencies from providing 24-hour coverage. In an age of instant access to computerized information, these conditions often result in ethical and legal problems of extreme complexity. A case is presented which raises the issues of confidentiality and liberty in the fiduciary relationship between doctor and patient. The concept of personal care is found to be paramount.