C-reactive protein mediates CD11b expression in monocytes through the non-receptor tyrosine kinase, Syk, and calcium mobilization but not through cytosolic peroxides

OBJECTIVE

C-Reactive protein (CRP) can modulate integrin surface expression on monocytes following Fcgamma receptor engagement. We have investigated the signal transduction events causing this phenotypic alteration.

METHODS

CRP-induced signalling events were examined in THP-1 and primary monocytes, measuring Syk phosphorylation by Western blotting, intracellular Ca(2+) ([Ca(2+)](i)) by Indo-1 fluorescence and surface expression of CD11b by flow cytometry. Cytosolic peroxides were determined by DCF fluorescence.

RESULTS

CRP induced phosphorylation of Syk and an increase in [Ca(2+)](i) both of which were inhibitable by the Syk specific antagonist, piceatannol. Piceatannol also inhibited the CRP-induced increase in surface CD11b. In addition, pre-treatment of primary monoytes with the Ca(2+) mobiliser, thapsigargin, increased CD11b expression; this effect was accentuated in the presence of CRP but was abolished in the presence of the [Ca(2+)](i) chelator, BAPTA. CRP also increased cytosolic peroxide levels; this effect was attenuated by antioxidants (ascorbate, alpha-tocopherol), expression of surface CD11b not being inhibited by antioxidants alone.

CONCLUSION

CRP induces CD11b expression in monocytes through a peroxide independent pathway involving both Syk phosphorylation and [Ca(2+)](i) release.

Induction of labour with a viable infant: a randomised clinical trial comparing intravaginal misoprostol and intravaginal dinoprostone

OBJECTIVE

To compare the efficacy and safety of vaginal misoprostol (50 microg) with vaginal dinoprostone.

DESIGN

Double-blind randomised trial.

SETTING

Obstetrics Department, Poissy Hospital, France.

PARTICIPANTS

370 patients with medical indications for induction of labour.

OUTCOME MEASURES

Vaginal deliveries within 24 hours, as well as time to vaginal deliveries, caesarean rates, costs, and fetal, neonatal and maternal condition.

RESULTS

Compared with vaginal dinoprostone, vaginal misoprostol resulted in greater efficacy in several areas: vaginal delivery within 24 hours; time to vaginal delivery; and vaginal delivery within 12 hours. There was a non-significant increase in the caesarean section rate for fetal distress in the misoprostol group, but fewer caesarean sections for failed induction. Fetal tolerance was similar in the two groups, although significantly more neonates had a cord pH <7.20 and (non-significantly) none had meconium stained amniotic fluid in the misoprostol group. The incidence of poor neonatal outcome was similar in both groups. Subgroup analysis by indication for induction showed that the higher rates of arterial cord pH <7.20 and of meconium-stained amniotic fluid with misoprostol persisted only in possible fetal compromise. Poor neonatal outcome was less frequent in the misoprostol group in cases of induction for non-fetal indications.

CONCLUSIONS

Vaginal misoprostol resulted in successful and earlier induction of labour more often than dinoprostone, but the safety of misoprostol raises some concern in potentially compromised infants. Misoprostol should be preferred to dinoprostone in cases of induction for non-fetal indications.

Centennial of the string galvanometer and the electrocardiogram

This article is a review of the history of the string galvanometer and of the electrocardiogram (ECG) on the occasion of the centennial of the instrument. Einthoven most likely developed the string galvanometer prior to 1901, the date of the first publication. The galvanometer made electrocardiography practical creating a new branch of medicine and even a new industry. In 1791 Galvani, in 1842 Mateucci and in 1855 Kolliker and Muller recorded, using the nerve muscle preparation, contraction of injured muscle, contraction of muscle when laid across a beating heart, and occasionally two contractions. In 1872 Lippmann introduced the capillary manometer. Using the capillary manometer Waller recorded for the first time from body surface voltage changes generated by the heart. Einthoven and Lewis dominated the early years of electrocardiography. The former made his contributions by 1913 while Lewis continued the studies of arrhythmias until 1920. The period following 1920 was influenced largely by Wilson. None did as much to advance ECG knowledge as did Wilson. The interest shifted to the theory of the ECG, abnormalities of wave form and of ECG leads. A major contribution of the ECG is in evaluation of ischemic heart disease and cardiac arrhythmias. Issues facing electrocardiography in the year 2000 include a shortage of experienced electrocardiographers, the advent of new noninvasive procedures and, paradoxically, wide acceptance of the ECG by the medical profession. The role of the computer in analysis of the clinical ECG is limited. The technique, while reasonably reliable for analysis of the normal tracing and some ECG waveforms, has serious limitations when applied to arrhythmias. The early hopes for "stand-alone" programs are yet to be realized.

Retropharyngeal abscesses: a clinical and radiologic correlation

OBJECTIVE

This study evaluates the efficacy at our centre of the lateral neck x-ray and the computed tomography (CT) scan in differentiating retropharyngeal cellulitis from abscess in retropharyngeal space inflammatory process.

METHOD

We reviewed the medical records of 37 patients with the diagnosis of retropharyngeal abscess or cellulitis hospitalized at the Centre Universitaire de Santé de l'Estrie in Sherbrooke between 1986 and 1997. Patients with a positive drainage at surgery were considered as retropharyngeal abscess and the rest as cellulitis. We measured the sensitivity, specificity, and positive and negative predictive values for the lateral neck x-ray and CT scan. Demographic and clinical data were also extracted for each patient.

RESULTS

Twenty-five patients were classified as retropharyngeal cellulitis and only six patients as retropharyngeal abscess, although 13 patients went to the operating room for drainage. Results for the sensitivity and specificity were 80% and 100% for the lateral neck x-ray and 100% and 45% for the CT scan. Positive and negative predictive values for lateral neck x-ray were 100% and 94%, respectively. Forty percent and 100% were the values calculated for the CT scan. Clinical data were consistent with what has been reported in the literature.

CONCLUSION

CT scan is helpful in the management of retropharyngeal abscess but has limits in differentiating cellulitis and abscess. Lateral neck x-ray was found to be very specific when the air sign was present.

Accelerated coronary reperfusion through the use of rapid bedside cardiac markers--case reports

Each year, acute myocardial infarctions (AMI) account for more than half a million deaths in the United States. Complicating treatment of AMI is the difficulty in accurately diagnosing the event, for patients have nondiagnostic electrocardiograms (ECG) more than 50% of the time. In this population, cardiac markers are essential to confirm the diagnosis. The new bedside cardiac markers, which use eight drops of whole blood and require 15 minutes to be read negative, make it possible to shorten time needed to diagnose AMI. One hundred twenty-seven consecutive patients presented to the emergency department complaining of atypical chest pain. All had ECGs that were nondiagnostic for myocardial infarction. Serial cardiac markers were performed: myoglobin, troponin I, rapid myoglobin, and rapid troponin I. One hundred eighteen patients with negative serial cardiac markers had exercise treadmill tests in the emergency department. Nine patients with positive serial cardiac markers received emergent primary angioplasty. Six of the nine patients were treated based on the positive results of the rapid bedside cardiac markers. A 100% correlation existed between the quantitative serum results and the rapid bedside markers. With the availability of rapid bedside assays, dependency on the laboratory can be minimized, since quantitative cardiac markers require at least 1 hour of turnaround time. Rapidly and correctly diagnosing AMIs in patients with ECGs nondiagnostic for AMI has always been a dilemma. Rapid bedside assays enable the physician to accurately diagnose myocardial infarction and safely decrease the time in evaluating chest pain, thus maximizing the benefits of early reperfusion.

Electrocardiographic manifestations of dual atrioventricular node conduction during sinus rhythm

OBJECTIVES

The objective of this study was to correlate electrocardiographic (ECG) PR interval changes during normal sinus rhythm with recent observations regarding the anatomy and physiology of the dual, slow and fast atrioventricular (AV) pathways.

BACKGROUND

The least common manifestation of dual AV conduction is an abrupt PR interval change in the setting of sinus rhythm. Whereas isolated cases of this phenomenon have been reported, the relatively large series we have collected makes it possible to correlate the ECG findings with the anatomy, composition and electrophysiology of the dual AV pathways.

METHODS

The ECGs of 21 patients with sinus rhythm and PR interval changes consistent with dual AV node physiology were studied. Observations include duration of the short and long PR intervals, the difference between the two and the events responsible for the PR interval change.

RESULTS

Eighteen of the 21 ECGs exhibited an abrupt and persistent PR interval change. Two of the other three ECGs manifested PR interval alternans, with slow and fast pathway, and a Wenckebach type I AV block; in the third ECG, findings compatible with simultaneous conduction along both pathways in response to a single stimulus were noted. Events responsible for the PR change included atrial premature complexes, atrial tachycardia, interpolated ventricular premature complexes and interpolated junctional premature complexes. In two the PR interval change appeared during a regular sinus rhythm.

CONCLUSIONS

The behavior of the PR interval is consistent with dual AV conduction. The PR interval duration hypothesized to represent slow pathway conduction is in keeping with the calculated anatomic length of the slow pathway. The Wenckebach type I block in the slow and fast pathways, as well as the altered conduction time in the slow pathway parallel with changing sinus rate, is evidence that the pathway is influenced by autonomic (?parasympathetic) innervation, supporting the premise that the pathways contain AV node-like tissue.

Cell-generated nitric oxide inactivates rat hepatocyte mitochondria in vitro but reacts with hemoglobin in vivo

BACKGROUND & AIMS

Nitric oxide forms inactive iron-nitrosyl complexes within hepatic mitochondria in vitro. However, when formed in vivo, NO might react instead with hemoglobin. The aim of this study was to compare the effects of cell-derived NO on rat hepatocyte mitochondria in vitro and in vivo.

METHODS

First, hepatocytes were cultured in vitro for 24 hours under a porous membrane supporting macrophages that were stimulated by endotoxin. Second, hepatic macrophage hyperplasia was induced in vivo by preadministration of killed Corynebacterium parvum; 7 days later, rats received endotoxin and were killed after 6 hours. Third, mitochondria were exposed to sodium nitroprusside in vitro, washed, mixed with blood, and recovered.

RESULTS

Iron-nitrosyl complexes and hepatocyte mitochondrial dysfunction were observed in the in vitro model and prevented by an NO synthase inhibitor. In the in vivo model, however, despite a 130-fold increase in plasma nitrate levels and formation of hemoglobin-NO complexes in blood, no iron-nitrosyl complex was detected in hepatic mitochondria, and hepatic mitochondrial function was not impaired. In the third model, mitochondria lost preformed iron-nitrosyl complexes when exposed to blood.

CONCLUSIONS

Although NO reacts with hepatocyte mitochondria in vitro, in vivo it reacts with sinusoidal hemoglobin without detectable impairment of hepatic mitochondrial function.

Effects of female sex hormones on mitochondria: possible role in acute fatty liver of pregnancy

Acute fatty liver of pregnancy occurs in some women. As other cases of microvesicular steatosis are due to impaired mitochondrial oxidation of fatty acids, we investigated the effects of female sex hormones on liver mitochondria in female mice. Three hours after administration of both estradiol (36 mumol/kg) and progesterone (150 mumol/kg), the in vitro beta-oxidation of [U-14C]palmitic acid and the activity of the tricarboxylic acid cycle decreased 49 and 54%, whereas the in vivo oxidation of [U-14C]palmitic acid decreased 38%. One week of treatment with both sex hormones produced ultrastructural lesions of mitochondria, decreased the recovery of mitochondrial proteins by 34%, increased state 4 respiration by 54-77%, and decreased the activities per gram of liver of several enzymes involved in the activation, mitochondrial uptake, and oxidation of fatty acids by 34-54%. We conclude that female sex hormones have deleterious effects on liver mitochondria and suggest that these effects, together with other factors, may contribute to the development of acute fatty liver of pregnancy in some women.

Inhibition by nilutamide of the mitochondrial respiratory chain and ATP formation. Possible contribution to the adverse effects of this antiandrogen

The effects of nilutamide on the mitochondrial respiratory chain were investigated in rats. In isolated mitochondria, nilutamide (100 microM) inhibited respiration that was supported by substrates feeding electrons into complex I of the respiratory chain but did not inhibit respiration that was supported by substrates donating electrons to complexes II, III or IV. Inhibition of complex I occurred without any lag time. In submitochondrial particles, nilutamide (100 microM) decreased both oxygen consumption mediated by NADH and the oxidation of NADH; addition of superoxide dismutase and catalase did not alleviate inhibition. There was no electron spin resonance evidence for detectable mitochondrial formation of the nilutamide nitro anion free radical by submitochondrial particles or for the formation of iron-nitrosyl complexes with mitochondrial Fe-S clusters in isolated hepatocytes. Severe inhibition of complex I by nilutamide (500 microM) led to upstream inhibition of fatty acid beta-oxidation. Nilutamide (100 microM) decreased the mitochondrial membrane potential and ATP formation in mitochondria energized by malate plus glutamate. In hepatocytes incubated without glucose, nilutamide (500 microM) led to an early (2 hr) drop in cellular ATP and early (4 hr) toxicity. With 5 mM glucose, however, ATP was not decreased and toxicity was mild at these early times. It was concluded that nilutamide itself inhibited the mitochondrial respiratory chain at the level of complex I and decreased ATP in hepatocytes incubated without glucose, which resulted in early toxicity. In the presence of glucose, ATP was not depleted at early times and delayed toxicity was probably the result of an oxidative stress (as previously reported).

Toxicity of the antiandrogen flutamide in isolated rat hepatocytes

The hepatotoxicity of flutamide, an antiandrogen that produces hepatitis in some human recipients, was studied in isolated rat hepatocytes. Flutamide (1 mM) led to the covalent binding of reactive electrophilic metabolites to male rat hepatocyte proteins. It decreased the reduced glutathione (GSH)/glutathione disulfide ratio and total protein thiols. This was associated with an early increase in phosphorylase a activity (a Ca(++)-dependent enzyme) and a decrease in cytoskeleton-associated protein thiols, the formation of plasma membrane blebs, the release of lactate dehydrogenase (LDH) and a loss of cell viability. Both covalent binding and LDH release were decreased by piperonyl butoxide (an inhibitor of cytochrome P450) and increased by dexamethasone pretreatment (which induces cytochrome P450 3A). The toxicity was increased by beta-naphthoflavone (which induces cytochrome P450 1A). Hepatocytes from female rats (which lack cytochrome P450 3A2) exhibited lower covalent binding and lower LDH release. The addition of cystine (a GSH precursor) increased hepatocellular GSH and decreased LDH release in male hepatocytes. The administration of a diet deficient in sulfur-containing amino acids had the opposite effects; it produced toxicity with 100 microM flutamide. Flutamide (50 microM) markedly inhibited respiration (mainly at the level of complex I) in isolated male rat liver mitochondria and flutamide (1 mM) decreased ATP levels in isolated male rat hepatocytes. It was concluded that flutamide is toxic to rat hepatocytes as a result of the cytochrome P450 (3A and also 1A)-mediated formation of electrophilic metabolites, whose damaging effects are further aggravated by the inhibitory effect of flutamide on mitochondrial respiration and ATP formation.

Inhibition by perhexiline of oxidative phosphorylation and the beta-oxidation of fatty acids: possible role in pseudoalcoholic liver lesions

In an attempt to better understand the mechanisms for pseudoalcoholic liver lesions in human beings, we determined the effects of perhexiline on mitochondrial functions in mice and rats. A first series of studies suggested that protonated perhexiline entered mouse mitochondria along the mitochondrial membrane potential. Release of a proton in the mitochondrial matrix led to uncoupling of oxidative phosphorylation, and accumulation of perhexiline inhibited complexes I and II of the respiratory chain, decreased ATP formation in vitro and decreased the mitochondrial beta-oxidation of long-, medium- and short-chain fatty acids in vitro and in vivo in mice. In cultured rat hepatocytes, exposure for 24 hr to 25 mumol/L perhexiline markedly decreased hepatocellular ATP and cell viability. Exposure to 5 mumol/L perhexiline did not modify ATP and viability but decreased the beta-oxidation of palmitic acid uniformly labeled with carbon 14 by 38%, increased hepatocyte triglyceride levels by 98% and produced microvesicular steatosis after 72 hr of culture. We conclude that perhexiline is concentrated inside mitochondria, where it inhibits both oxidative phosphorylation and the mitochondrial beta-oxidation of fatty acids. These effects may contribute to the development of necrosis, steatosis and possibly certain other pseudoalcoholic liver lesions in human beings.

Evaluation of human blood lymphocytes as a model to study the effects of drugs on human mitochondria. Effects of low concentrations of amiodarone on fatty acid oxidation, ATP levels and cell survival

Human lymphocytes were assessed as a cellular model for determining the effects of drugs on human mitochondria. Formation of total oxidized 14C-products was maximal with 1 mM [U-14C]palmitic acid, was linear for 90 min, linear with the number of lymphocytes, and decreased by 95% and 77% in the presence of 30 microM rotenone and 2 mM KCN. Seven drugs were tested which had previously been shown to inhibit beta-oxidation in animals; all decreased formation of total oxidized 14C-products by human lymphocytes, but with different IC50 values: 35 microM with amiodarone, 2.75 mM with tetracycline and amineptine, 3.75 mM with tianeptine, and more than 10 mM for valproic acid and the ibuprofen enantiomers. Formation of [14C]CO2 either increased or decreased, in relation to the various effects of these drugs on coupling, beta-oxidation, and the tricarboxylic acid cycle. There was a general trend for some relationship between inhibition of fatty acid oxidation and loss of cellular ATP. Those compounds, however, which uncoupled oxidative phosphorylation (2,4-dinitrophenol, amiodarone, ibuprofen) and/or inhibited the mitochondrial respiratory chain (amiodarone, rotenone, KCN) resulted in comparatively higher ATP depletion. Amiodarone, a drug which produces several effects (uncoupling, inhibition of beta-oxidation, of the tricarboxylic acid cycle and of the respiratory chain), caused a dramatic decrease in cellular ATP and cell viability at low concentrations (20-100 microM). Both these effects were prevented by the addition of 5 mM glucose, a substrate for anaerobic glycolysis. We conclude that human lymphocytes may be a useful model for assessing the effects of drugs on human mitochondrial function. IC50 values determined with this model may not necessarily apply, however, to other cells.

Data monitoring in the cardiac arrhythmia suppression trial

OBJECTIVE

This report discusses practical aspects of data monitoring in a clinical trial which stopped ahead of schedule due to adverse findings.

DESIGN

A review of the considerations and decisions made by the data-monitoring committee of the Cardiac Arrhythmia Suppression Trial (CAST), a randomized, double-blind clinical trial.

PATIENTS

CAST consisted of men and women with a recent myocardial infarction, asymptomatic or minimally symptomatic ventricular arrhythmias, and reduced left ventricular ejection fraction.

INTERVENTIONS

In CAST, 3 antiarrhythmic agents, encainide, flecainide, and moricizine, were compared against placebo.

MAIN OUTCOME MEASURES

The main outcome measures in CAST were arrhythmic death and total mortality.

RESULTS

CAST found the 3 agents to be harmful. Encainide and flecainide were stopped first. Subsequently, moricizine was discontinued ahead of schedule.

CONCLUSIONS

The complexity of the study design and a midcourse protocol modification raise several data-monitoring issues not previously discussed. These include how to handle apparently dramatic yet unexpected results, the need for flexibility in modifying study design and goals, and the conflict between existing study data and both conventional wisdom and medical practice.

"Supernormal" conduction and excitability

Electrocardiographic manifestation of "supernormal" conduction is defined as conduction that is more rapid than expected or presence of conduction when block is anticipated. It is not supernormal in the sense or being more rapid than normal. Therefore, the term relative supernormality or "supernormality" is more appropriate. The mechanism of "supernormal" conduction is conduction during a period of supernormal excitability and conduction associated with altered membrane potential. Some of the more common phenomena that are not dependent on conduction during the supernormal period but manifest better than expected conduction, thus simulating "supernormal" conduction, include dual AV nodal conduction, the "gap" phenomenon, "peeling back" of the refractory period, summation of subthreshold responses, diastolic phase 4 depolarization, and phasic autonomic influences.

Decreased mitochondrial oxidation of fatty acids in pregnant mice: possible relevance to development of acute fatty liver of pregnancy

Severe impairment of the beta-oxidation of fatty acids, as a consequence of a single factor or a combination of different causes, leads to microvesicular steatosis of the liver. In an effort to understand the mechanism(s) leading to the development of acute fatty liver of pregnancy in some women, we determined the effects of pregnancy on the mitochondrial oxidation of fatty acids in mice. In vivo, the rate of oxidation of the whole fatty-acid chain length was determined by measuring the rate of exhalation of [14C]CO2 after intragastric administration of a tracer dose of [U-14C]palmitic acid. [14C]CO2 exhalation was not significantly decreased at 14 days of gestation, but it had declined by 40% at 18 days of gestation (i.e., 24 to 48 hr before delivery). The rate of first beta-oxidation cycle was assessed by measuring the rate of [14C]CO2 exhalation after administration of [1-14C]octanoic acid, [1-14C]butyric acid or [1-14C]palmitic acid. [14C]CO2 exhalation had declined by 60%, 46%, and 24% after administration of [1-14C]octanoic acid, [1-14C]butyric acid and [1-14C]palmitic acid, respectively, in 18-day-pregnant mice. Total hepatic lipids and triglycerides, expressed per gram of liver, remained unchanged in 18-day-pregnant mice. In vitro, the rate of mitochondrial beta-oxidation (expressed per milligram of protein) had decreased by 47% at 18 days' gestation with [U-14C]palmitic acid as substrate and by 33% with [1-14C]octanoic acid but remained unchanged with [1-14C]palmitic acid. The activity of the tricarboxylic acid cycle, assessed by the formation of [14C]CO2 from [1-14C]acetic acid, had decreased by 24%. We conclude that the mitochondrial oxidation of fatty acids decreased during late-term pregnancy in mice as a consequence of both decreased mitochondrial beta-oxidation of medium-chain fatty acids, and decreased activity of the tricarboxylic acid cycle. We suggest that this effect, in combination with other factors, may contribute to the development of fatty liver of pregnancy in some pregnant women.

Metabolic activation of the nitroaromatic antiandrogen flutamide by rat and human cytochromes P-450, including forms belonging to the 3A and 1A subfamilies

The in vitro metabolic activation of flutamide, a nitroaromatic antiandrogen which produces hepatitis in a few recipients, was first studied with male rat liver microsomes. There was no electron spin resonance evidence for the reduction of flutamide by reduced nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P-450 reductase into a nitro anion free radical. In contrast, flutamide was oxidatively transformed by cytochrome P-450 into reactive metabolite(s) that covalently bound to microsomal proteins. Covalent binding required oxygen and NADPH, and was decreased by the nucleophile glutathione and by the cytochrome P-450 inhibitors SKF 525-A, piperonyl butoxide and troleandomycin (an inhibitor of the cytochrome P-450 3A subfamily). Covalent binding was increased markedly by pretreatment with dexamethasone (an inducer of the cytochrome P-450 3A subfamily) and moderately by pretreatment with beta-naphthoflavone (an inducer of the 1A family). Covalent binding was immunoinhibited markedly by anticytochrome P-450 3A immunoglobulin G and moderately by anticytochrome P-450 1A immunoglobulin G. Covalent binding was much lower with liver microsomes from female rats (not expressing P-450 3A2). Covalent binding of flutamide also occurred with human liver microsomes (where it was inhibited by troleandomycin), and with yeast microsomes expressing human liver cytochromes P-450 1A1, 1A2 or 3A4. We concluded that flutamide was oxidatively transformed into chemically reactive metabolite(s) by rat and human cytochromes P-450, including forms belonging to the 3A and 1A subfamilies.

Increased ethane exhalation, an in vivo index of lipid peroxidation, in alcohol-abusers

Ethane exhalation was measured in 42 control subjects, 52 patients with various non-alcoholic liver diseases, and 89 alcohol abusers who had been admitted to hospital for alcohol withdrawal and assessment of liver disease (six with normal liver tests, 10 with steatosis with or without fibrosis, six with alcoholic hepatitis, 29 with cirrhosis, 34 with both cirrhosis and alcoholic hepatitis, and four with both cirrhosis and a hepatocellular carcinoma). Ethane exhalation was similar in control subjects and in patients with non-alcoholic liver diseases, but was five times higher in alcohol abusers. Ethane exhalation in alcohol abusers was significantly, but very weakly, correlated with the daily ethanol intake before hospital admission, and the histological score for steatosis, but not with the inflammation or alcoholic hepatitis scores. Ethane exhalation was inversely correlated with the duration of abstinence before the test. In nine alcoholic patients, the exhalation of ethane was measured repeatedly, and showed slow improvement during abstinence. Ethane exhalation was significantly but weakly correlated with the Pugh's score in patients with alcoholic cirrhosis. It is concluded that the mean ethane exhalation is increased in alcohol abusers. One of the possible mechanisms may be the presence of oxidizable fat in the liver. The weak correlation with the Pugh's score is consistent with the contribution of many other factors in the progression to severe liver disease.

Mechanism for the hepatotoxicity of the antiandrogen, nilutamide. Evidence suggesting that redox cycling of this nitroaromatic drug leads to oxidative stress in isolated hepatocytes

The nitroaromatic drug nilutamide has been shown previously to undergo redox cycling in aerobic rat liver microsomes, being reduced by NADPH-cytochrome P-450 reductase to a nitro anion-free radical which reacts with oxygen, to regenerate the parent drug, and form a superoxide anion dismuted to hydrogen peroxide. In the present study, the effects of nilutamide on isolated rat hepatocytes have been determined. After 6 and 8 hr of incubation with 0.5 mM nilutamide, lactate dehydrogenase was released in the incubation medium, and cell viability was decreased markedly. Consistent with a redox cycle producing reactive oxygen species, nilutamide increased nonmitochondrial (cyanide-resistant) oxygen consumption; the toxicity of nilutamide occurred sooner and was more extensive in the presence of sodium azide (an inhibitor of catalase). Consistent with an oxidative stress, the toxicity of nilutamide was associated with depletion of reduced glutathione, increased levels of glutathione disulfide, increased Ca(++)-dependent phosphorylase a activity, oxidation and accumulation of cytoskeleton-associated proteins and formation of blebs; toxicity was prevented by glutathione precursors, thiol reductants and/or antioxidants, such as L-cystine, L-cysteine, N-acetyl-L-cysteine, dithiothreitol, N,N'-diphenyl-p-phenylene-diamine and alpha-tocopherol. Feeding the animals with a diet supplemented with 2% L-cystine increased the initial glutathione stores of hepatocytes and prevented nilutamide toxicity. It is concluded that nilutamide is toxic to isolated rat hepatocytes, as a probable consequence of an oxidative stress due to the redox cycling of this nitroaromatic compound.

Cardiac alternans: diverse mechanisms and clinical manifestations

OBJECTIVES

The purpose of this review is to assemble the widely dispersed information about cardiac alternans and to categorize the types and mechanisms of alternans, their clinical manifestations and possible therapeutic implications.

BACKGROUND

The phenomena of mechanical and electrical alternans have been of continuing interest to both physiologists and clinicians. Recent studies have enhanced this interest because of the reported association of alternans with experimental myocardial ischemia and cardiac arrhythmias.

METHODS

The review formulates concepts based on extensive review of published studies and personal observations.

RESULTS

Cardiac alternans has been subdivided into the following four categories: 1) mechanical, 2) electrical, 3) in association with myocardial ischemia, and 4) in association with cardiac motion. Mechanical alternans can be explained by hemodynamic or inotropic alterations, or both. Mechanical alternans in the ventricular muscle is accompanied by alternans of action potential shape. In the Purkinje fibers, action potential duration alternates without change in shape and is determined by the duration of the preceding diastolic interval. However, in ventricular muscle fiber, alternans can occur in the presence of constant diastolic intervals. T wave alternans reflects changes in action potential duration and is frequently associated with a long QT interval. Electrocardiographic manifestations of conduction alternans occur at many different sites within the conducting system and myocardium. During myocardial ischemia, additional mechanisms of repolarization alternans have been proposed. Alternans occurring in the presence of a large pericardial effusion is attributed to swinging motion of the heart maintaining two-beat periodicity.

CONCLUSIONS

Since its origin as "pulsus alternans" described by Traube in 1872, the definition of alternans has evolved into a term encompassing multiple physiologic and pathologic phenomena that, although united by the term cardiac alternans, diverge widely with respect to etiology, mechanism and clinical significance.

Inhibition by salicylic acid of the activation and thus oxidation of long chain fatty acids. Possible role in the development of Reye's syndrome

Administration of either aspirin or salicylic acid (3 mmol.kg-1 b.wt. i.p.) decreased by 50 and 65%, respectively, the in vivo oxidation of [U-14C]palmitic acid to [14C]CO2 in mice; after salicylic acid administration, exhalation of [14C]CO2 from [1-14C]palmitic acid, [1-14C]octanoic acid or [1-14C]butyric acid was decreased by 87, 33 and 38%, respectively. Inhibition lasted 9 hr. It was associated with markedly decreased blood glucose concentrations and increased plasma ketone bodies. Repeated administration of salicylic acid (2 mmol.kg-1 i.p. every 8 hr) tripled hepatic triglycerides and produced mild microvesicular steatosis of the liver at 22 hr in fasted mice. In vitro, salicylic acid (1.5 mM) had no or little effect on the formation of beta-oxidation products from [1-14C]octanoic or [1-14C]palmitoyl-L-carnitine, in the presence of ATP, carnitine (40 microM) and coenzyme A (40 microM), but decreased by 51% that from [1-14C]palmitic acid. In the latter system, increasing the concentrations of coenzyme A and carnitine to 200 microM suppressed the inhibitory effect of salicylic acid. Salicylic acid (1.5 mM) decreased by 80% the in vitro mitochondrial formation of palmitoyl-coenzyme A from [1-14C]palmitic acid and 10 microM coenzyme A; again, increasing the concentration of coenzyme A prevented inhibition. We conclude that salicylic acid decreases the mitochondrial activation and thus beta-oxidation of long chain fatty acids, presumably by sequestering extramitochondrial coenzyme A and possibly carnitine.

Wide QRS tachycardia

Wide QRS tachycardia is a diagnostic challenge when confronted on a 12-lead electrocardiogram. The differential diagnosis includes: ventricular tachycardia; supraventricular tachycardia with aberration; and Wolff-Parkinson-White syndrome. Confronted with a wide QRS tachycardia, one must determine whether the origin is ventricular or supraventricular because the therapy will differ. The electrocardiographic findings of capture beats, fusion beats and atrioventricular dissociation are highly specific for ventricular tachycardia but not very sensitive. After careful assessment of the 12-lead electrocardiogram following selected diagnostic features, the correct diagnosis of the cause of wide QRS tachycardia can be made in about 90 percent of patients. This article contains a brief discussion of the diagnostic features of wide QRS tachycardia.