[Adaptation of Biomerieux enzymatic UV ammonia on Konelab analysers]

INTRODUCTION

Circulating ammonia in normal patients is relatively low, despite the fact that ammonia is continually produced from endogenous amino acid metabolism. The physiopathological interest of plasmatic ammonia determination lies primarily in its relationships to hepatic insufficiency (cirrhotic or neoplasic), or the diagnosis and the forecast of the Reye's syndrome.

OBJECTS

This study describes an evaluation of plasmatic ammonia determination by the UV end point enzymatic method using GLDH on KONELAB(TM) analyzers.

METHODS

The glutamate dehydrogenase (GLDH : EC.1.4.1.3) catalyses the reducing amination of alpha-cetoglutarate in the presence of NH(4)(+) and of NADPH, H(+) to form glutamate and NADP(+). The reduction of NADPH,H(+)'s concentration, directly proportional to ammonia rates, is evaluated at 340 nm. All the conditions were met to optimize the method, while covering a satisfying field of measurement.

RESULTS AND COMMENTS

The evaluation of the modified method showed a good precision (repeatability: CV < 4 %; interserial reproducibility: CV from 2.01 to 2.93 %; Intraserial reproducibility: CV equal to 0.67%) and a very good accuracy. The field of measurement extends from 27 to 250 micromol/L, with a limit of detection (L(D)) lowered to 0.325 micromol/L.

CONCLUSION

The adapted technique is simple, fast, inexpensive and especially automatizable. It is in addition reliable and chiefly more sensitive, adapting particularly to the determination of plasmatic ammonia in urgency as in routine within our laboratory.

The isoprenoid pathway and the pathogenesis of Reye's syndrome

The isoprenoid pathway produces three key metabolites: endogenous digoxin (regulator of neurotransmitter uptake), dolichol, and ubiquinone (free radical scavenger). Since a mitochondrial dysfunction has been described in Reye's syndrome, it was considered pertinent to assess the pathway in this disease. Since endogenous digoxin can regulate neurotransmitter transport, the pathway was also assessed in patients with right hemispheric, left hemispheric, and bihemispheric dominance to find out the role of hemispheric dominance in its pathogenesis. The plasma/serum activity of hydroxy methyl glutaryl (HMG) coenzyme A (CoA) reductase, magnesium, digoxin, dolichol, ubiquinone, tryptophan/tyrosine catabolic patterns, and free radical and lipid levels, as well as RBC Na+, K(+)-ATPase activity, were measured in the groups mentioned.

RESULTS

In the patient group as well as in individuals with right hemispheric dominance similar patterns were obtained. There was elevated digoxin and dolichol levels with low levels of ubiquinone in patients with Reye's syndrome as well as in those with right hemispheric dominance. The serum magnesium and RBC Na+, K(+)-ATPase activity were reduced. There was also an increase in tryptophan catabolites and a reduction in tyrosine catabolites as well as increased free radical levels. Reye's syndrome is associated with an upregulated isoprenoid pathway, elevated hypothalamic digoxin secretion, and right hemispheric chemical dominance.

The isoprenoid pathway and the pathogenesis of Reye's syndrome

The isoprenoid pathway produces three key metabolites: endogenous digoxin (regulator of neurotransmitter uptake), dolichol, and ubiquinone (free radical scavenger). Because a mitochondrial dysfunction has been described in Reye's syndrome, we thought it pertinent to assess the pathway in this disease. Since endogenous digoxin can regulate neurotransmitter transport, the pathway also was assessed in patients with right hemispheric, left hemispheric, and bihemispheric dominance to find out the role of hemispheric dominance in its pathogenesis. The plasma/serum activity of HMG CoA reductase, magnesium, digoxin, dolichol, ubiquinone, tryptophan/tyrosine catabolic patterns, free radical, and lipid levels as well as (red blood cell) RBC Na(+)-K(+) ATPase activity were measured in the above mentioned groups.

RESULTS

In the patient group as well as in individuals with right hemispheric dominance similar patterns were obtained. There was elevated digoxin and dolichol levels with low levels of ubiquinone in patients with Reye's syndrome as well as in those with right hemispheric dominance. The serum magnesium and RBC Na(+)-K(+) ATPase activity were reduced. There also was an increase in tryptophan catabolites and a reduction in tyrosine catabolites as well as increased free radical levels. Reye's syndrome is associated with an upregulated isoprenoid pathway, elevated hypothalamic digoxin secretion, and right hemispheric chemical dominance.

[Reye's syndrome--a severe complication of salicylate therapy]

Clinical and experimental data are reviewed on the Reye's syndrome--a heavy complication accompanying the therapy of viral infections in children by salicylates. Disorders in the bioenergetics of fatty acid oxidation and ammonia utilization are considered in the context of clinical manifestations of the Reye's syndrome.

Reye's syndrome in the United States from 1981 through 1997

BACKGROUND

Reye's syndrome is characterized by encephalopathy and fatty degeneration of the liver, usually after influenza or varicella. Beginning in 1980, warnings were issued about the use of salicylates in children with those viral infections because of the risk of Reye's syndrome.

METHODS

To describe the pattern of Reye's syndrome in the United States, characteristics of the patients, and risk factors for poor outcomes, we analyzed national surveillance data collected from December 1980 through November 1997. The surveillance system is based on voluntary reporting with the use of a standard case-report form.

RESULTS

From December 1980 through November 1997 (surveillance years 1981 through 1997), 1207 cases of Reye's syndrome were reported in patients less than 18 years of age. Among those for whom data on race and sex were available, 93 percent were white and 52 percent were girls. The number of reported cases of Reye's syndrome declined sharply after the association of Reye's syndrome with aspirin was reported. After a peak of 555 cases in children reported in 1980, there have been no more than 36 cases per year since 1987. Antecedent illnesses were reported in 93 percent of the children, and detectable blood salicylate levels in 82 percent. The overall case fatality rate was 31 percent. The case fatality rate was highest in children under five years of age (relative risk, 1.8; 95 percent confidence interval, 1.5 to 2.1) and in those with a serum ammonia level above 45 microg per deciliter (26 micromol per liter) (relative risk, 3.4; 95 percent confidence interval, 1.9 to 6.2).

CONCLUSIONS

Since 1980, when the association between Reye's syndrome and the use of aspirin during varicella or influenza-like illness was first reported, there has been a sharp decline in the number of infants and children reported to have Reye's syndrome. Because Reye's syndrome is now very rare, any infant or child suspected of having this disorder should undergo extensive investigation to rule out the treatable inborn metabolic disorders that can mimic Reye's syndrome.

Augmented inflammatory cytokines in primary dengue infection progressing to shock

Dengue fever (DF) which is caused by four serotypes of dengue virus may in some cases progress into a life threatening situation of dengue haemorrhage fever (DHF) and dengue shock syndrome (DSS). It has been suggested that sequential infection with different dengue virus serotypes predisposes the patient towards DHF/DSS. We report here a primary dengue infection in a 10-year-old boy progressing from DF to DSS while under clinical observation. The report provides unequivocal evidence for the development of DSS in primary dengue infection caused by virus serotype 4. The close relationship between sequential changes in the levels of tumour necrosis factor (TNF), Interleukin 1 and 6 (IL-1 and IL-6) in the serum, to the clinical progression of the disease from DF to DHF/DSS and then to full recovery implicates a pathogenetic role for the inflammatory cytokines. The child also manifested clinical features consistent with Reye's syndrome and this suggests a common pathogenetic origin for DSS and the Reye-like syndrome induced by dengue virus.

Rate-dependent distal renal tubular acidosis and carnitine palmitoyltransferase I deficiency

An infant girl presented with recurrent episodes of Reye-like syndrome associated with hypoketosis and plasma carnitine levels in the high-normal range. A liver biopsy revealed massive macrovesicular steatosis. Ketogenesis was absent after a long-chain triglyceride loading test; in contrast, the medium-chain triglyceride loading test resulted in a brisk rise in plasma ketone concentration. Carnitine palmitoyltransferase I deficiency was demonstrated in cultured skin fibroblasts. Hypoglycemia was only found once in the neonatal period. Renal carnitine handling was normal except for a higher renal threshold for free carnitine. Mild, persistent metabolic acidosis was a constant feature, even during periods between metabolic decompensation. Evaluation of the renal acidification capacity showed a failure to acidify the urine during spontaneous acidosis but increased acid excretion and a normal decrease of urinary pH after acid loading. Also, a small difference between urine and blood PCO2 was found after bicarbonate administration. This acidification defect can best be explained as an abnormality in distal tubular H+ secretion: a rate-dependent distal tubular acidosis.off is speculated that long-chain acylcarnitines, substances that cannot be formed by carnitine palmitoyltransferase I-deficient patients, play an essential role in renal acid-base homeostasis.

Reye's syndrome in the British Isles: report for 1990/91 and the first decade of surveillance

The Reye's syndrome (RS) surveillance scheme for the British Isles, jointly organised by the British Paediatric Association and the PHLS Communicable Disease Surveillance Centre, was established in 1981. In the ten years that have followed, there has been a gradual decline in the number, and the age, of cases reported. However, the proportion of cases whose diagnosis was subsequently revised to that of an inherited metabolic disorder, has increased. These trends have been influenced by the change from 'passive' to 'active' case ascertainment in 1986; the aspirin warning issued by the Committee on Safety of Medicines in June 1986; the 1989 influenza epidemic; and the increasing awareness of conditions that mimic RS, particularly inherited metabolic disorders involving defects of fatty acid oxidation. The cases reported in 1990/91 showed the lowest annual incidence recorded so far and a median age of less than ten months (compared with 15 months in the first six years of surveillance). There was a reduction in the case fatality rate in 1990/91 (although still high at 38%) but it is of concern that two children had had pre-admission exposure to aspirin. Parents should be kept aware of the dangers of giving aspirin preparations to children with feverish illnesses.

Fatty acid composition of hepatic triglycerides in Reye's syndrome: implications for hepatic desaturase abnormalities

Serum NEFA profiles in Reye's syndrome are reportedly unique with a disproportionate percent made up of polyunsaturated fatty acids some of which are not ordinarily found in the serum. This pattern is also reflected in the serum triglyceride composition as well. As the liver is probably the sole source of the serum triglyceride in Rye's syndrome because patients are vomiting or in coma, the fatty acid acid composition of the liver triglyceride was examined for insight regarding the lipid abnormalities in this disease. Palmitic acid (16:0) and the sum of all the saturated fatty acids in the liver triglycerides were significantly decreased whereas the sum of the monoenoic fatty acids and the products of delta 9 desaturase activity were increased in Reye's samples. When these data were compared to the fatty acid composition of the serum triglyceride from a separate cohort of Reye's and control subjects, certain inferences regarding hepatic delta 9, delta 6, delta 5, and delta 4 desaturase activities and the elongases can be drawn from the liver and serum triglyceride fatty acid profiles which are unique. Collectively, these data reflect considerable intrahepatic fatty acid desaturation and elongation activity and/or acyl transfer from lipid to lipid of various polyunsaturated fatty acids in Reye's syndrome.

Reye's syndrome in Bangalore

One hundred and twenty four cases of Reye's syndrome admitted to Vanivilas Children's Hospital, Bangalore were investigated. Clinical, biochemical and epidemiological details were obtained. The median age was five years, with no difference in sex ratio. This disease was frequent in winter months. Cases clustered in certain congested localities of the city among lower socio economic strata. Aspirin and varicella could not be associated as preceding factors. The clinical and biochemical features of the patients were suggestive of Reye's syndrome. Histopathological evaluation was done in 104 liver biopsy specimens. Virological studies for influenza and arbovirus were negative. Mortality was high (78%).

Non-icteric fulminant hepatitis and Reye's syndrome: comparison of laboratory data

Twenty-eight patients with suspected Reye's syndrome (RS) were seen in our Department from 1974 through 1987. Liver biopsy confirmed the diagnoses of RS and non-icteric fulminant hepatitis (NIFH) in 7 and 5 cases, respectively. NIFH was the most common RS mimicker. Total bilirubin, LDH and serum ammonia levels showed no significant differences between RS and NIFH. However, the levels of serum GOT and GPT were significantly higher in the NIFH group. Serum and urinary carnitine levels were measured in both groups, but the results were inconclusive. Amino acid analysis in one RS and two NIFH patients showed no significant differences in the ratio of branched chain to aromatic amino acids. However, one RS patient showed a high level of lysine. Histological findings in the liver of two NIFH patients showed minor mitochondrial swelling and microvesicular fat, but the major finding was hepatic necrosis. Our experience indicates that NIFH and RS cannot be differentiated by routine laboratory tests. Liver biopsy is essential for the accurate diagnosis of RS.

Continuous monitoring of intracranial pressure in Reye's syndrome--5 years experience

Monitoring of intracranial pressure (ICP) and efforts to keep the ICP below the critical level are vital in the treatment of Reye's syndrome. Continuous monitoring of ICP was carried out in 21 cases of Reye's syndrome who were at or beyond stage III at the time of admission to the Veterans General Hospital, between January 1981 and August 1986. Seventeen had ICP ranging from 15 mmHg to 67 mmHg. Three patients died, 1 in stage V with an ICP of 67 mmHg received a craniectomy, and 2 others were in stage IV with ICP's of 66 mmHg and 25 mmHg, respectively. The fatality rate was 14% (3/21). Among 18 patients, 5 had moderate psychomotor retardation (PMR), 4 had severe PMR and 2 had mild PMR. The remaining 7 patients survived without sequelae. Blood exchange transfusion could further reduce ICP and seemed to improve neurologic outcome. Blood ammonia higher than 400 micrograms% is indicative of a bad prognosis. Hyperventilation was the most rapid and effective means of reducing moderate degrees of increased ICP. During intensive supportive care, we also found that coughing, endotracheal intubation, seizures, asynchronous respiration to an artificial respirator, suction of the airway and any painful stimulation caused further increases in ICP and worsened the situation. Care should be given to avoid these factors.

Recurrent, familial Reye-like syndrome with a new complex amino and organic aciduria

Five of 13 siblings from a Jewish-Ashkenazi family suffered from recurrent Reye-like episodes. During attacks, these patients excreted alpha-keto-adipic, alpha-hydroxy-adipic, and alpha-aminoadipic acids, branched-chain keto acids and saccharopine in addition to lactic, pyruvic, and dicarboxylic acids characteristic of Reye syndrome. The serum concentrations of citrulline and alpha-amino-adipic acid were elevated and carnitine was at the upper limit of the normal range. Serum acetoacetate level was 4-5 times the beta-hydroxybutyrate level, but the pyruvate/lactate ratio was normal. Notably, plasma ketone bodies were lower than expected from the degree of catabolism. When the patients were symptom-free, no abnormal amino or organic acids in serum or urine were detected. These findings might be interpreted as a functional impairment at three different biochemical sites: fatty acid beta-oxidation, dehydrogenase complexes of the pyruvic, alpha-ketoglutaric, alpha-ketoadipic, and branched-chain keto acids, and pyruvate carboxylase. We suggest that in this hereditary disorder a toxic substance, exogenously or endogenously derived, interfered at multiple sites in different metabolic pathways.

Pentobarbital quantitation using immunoassays in Reye's syndrome patient serum

Analysis of serum pentobarbital concentrations in 28 specimens from Reye's syndrome patients was conducted with modifications of three nonspecific immunoassay procedures originally designed to detect barbiturates in serum or urine. An adaptation of the urine enzyme-multiplied immunoassay technique (EMIT) Dupont aca barbiturate screen to the quantitation of serum pentobarbital is described. Replicate analysis of control specimens containing pentobarbital across a wide spectrum of concentrations revealed a between-day precision of less than 6%. Regression analysis revealed excellent agreement with a high-performance liquid chromatography (HPLC) method: (HPLC) = 0.98 (aca) - 0.07 (r = 0.97). Multiple linear regression analysis with a serum EMIT barbiturate screen and a urine fluorescence polarization immunoassay screen modified to quantitate pentobarbital in serum revealed excellent agreement among all methods, demonstrating that immunoassays offer a reliable approach to pentobarbital quantitation.

Effect of Reye's syndrome serum on the ultrastructure of isolated liver mitochondria

Reye's syndrome (RS) is characterized by alterations in the ultrastructure of liver mitochondria and a generalized impairment of mitochondrial enzyme activity. Serum from RS patients impairs ATP formation and oxidative phosphorylation of isolated liver mitochondria. We examined the effect of serum from four RS patients (including mild and severe illnesses) to determine whether RS serum induces quantifiable morphometric changes in isolated liver mitochondria. RS serum expands the mitochondrial matrix (matrix = 85 to 91% of cross-sectional area, compared with 65 +/- 12% with control serum, p less than .01) and in many cases the matrix is less dense, cristae are less apparent, and mitochondrial shape is irregular. After incubation with RS serum, mitochondria are also slightly larger (range = 0.563 to 0.492 micron 2) than mitochondria incubated with serum from normal controls (0.421 +/- 0.303 micron 2). These changes are similar to those observed in vivo in RS. The effect of RS serum is largely irreversible, resembling the effect of an uncoupler of oxidative phosphorylation, and corresponds to the free fatty acid concentration in the serum, especially the concentration of serum dicarboxylic acids. Addition of comparable amounts of long chain dicarboxylic acids induces an irreversible expansion and some distortion of mitochondria comparable to that after the addition of RS serum. There is no correlation between alteration in ultrastructure and the presence of salicylates in the serum samples. The results indicate that dicarboxylic acids may play a role in the changes in mitochondrial ultrastructure that characterize RS.

Pharmacology of Reye syndrome

Reye syndrome, a reversible metabolic encephalopathy and hepatopathy, offers a unique opportunity to investigate the pharmacologic mechanisms by which a toxic-metabolic insult to mitochondria is translated into neurochemical and neurologic dysfunction. Similarity of some clinical and metabolic abnormalities between certain inborn errors of organic acid, ammonia, and carbohydrate metabolism and Reye syndrome suggests a common pathophysiologic mechanism at some level. The primary metabolic aberration in Reye syndrome is unknown. Viral, drug, and toxic precipitants in a conductive host alter glial and neuronal function, possibly by direct toxic effects or by altered transmitter metabolism and signal transduction. These events translate into a rather stereotyped progression of the clinical syndrome. Increased ICP, which is a life-threatening epiphenomenon, is the focus of conventional therapy. Investigational treatments, still in preliminary stages, are aimed at early correction of instigating metabolic abnormalities or correction of their consequences on central neurotransmission. Our fragmentary knowledge of neurotransmitter abnormalities in this disorder, which have suggested disparate interpretations, does not allow a cohesive pharmacologic theory of Reye syndrome. The greatest difficulties in interpretation of possible central mechanisms from existing data, which derive largely from peripheral tissues, is in the differentiation of primary from compensatory changes. The unitarian notion that a single pharmacologic disturbance is the source of the encephalopathy is perhaps too simplistic. It is hoped that future studies of disorders such as Reye syndrome will elucidate the intricate relationships between biochemical pathways and neurotransmitter metabolism.

Advances in the application of biochemical tests to diseases of the liver and biliary tract: their role in diagnosis, prognosis, and the elucidation of pathogenetic mechanisms

Despite the biochemical complexity of the liver, few laboratory tests provide discriminatory diagnostic information in patients with hepatobiliary disease. Recent efforts have concentrated upon tests which assess the function of the liver, the severity of the disease state, and underlying pathological processes. Bile Acids: The emergence of facile technology and widespread application has brought the realization that these assays are not as sensitive in detecting liver disease as previously believed, although the cholate/chenate ratio may be useful in distinguishing cholestasis from chronic liver disease. The presence of unusual bile acids in serum or urine may be helpful in some cases. Drug Metabolism: A number of tests provide good evidence about liver function, hepatic blood flow and portal shunting, but the aminopyrine breath tests is the most useful, giving prognostic information in acetaminophen overdose and alcoholic liver disease. The antipyrine half-life identifies surgical cases at risk from poor hepatic function. Proteins and Immunochemical Tests: Interest has developed in plasma proteins such as prealbumin and retinol-binding protein to monitor hepatic protein synthetic function. Secretory IgA is more elevated in biliary tract disease, unlike the native protein which is increased principally in cirrhosis. Type III procollagen can be measured in serum, and correlates with the activity of collagen synthesis and the degree of fibrosis in biopsy samples. Reye's Syndrome: Biochemical tests play an essential role in diagnosis of this recently discovered disease. These will be presented and discussed.

Erythrocyte lipid abnormalities in Reye's syndrome

Previous studies have demonstrated alterations in plasma free fatty acid content in Reye's syndrome (RS). We have therefore studied erythrocyte membrane lipids to determine if there are concomitant structural and functional modifications attributable to RS. Erythrocyte lipids were measured in children with RS and in critically ill children also requiring intensive care (ICU). In comatose RS patients erythrocyte phospholipid arachidonate was increased 2-fold relative to control ICU patients: 20.46 +/- 2.14 versus 10.41 +/- 2.32% of total erythrocyte phospholipid, p less than 0.05. RS coma patients also demonstrated an increased ratio of erythrocyte phospholipid polyunsaturated/saturated fatty acids (0.76 +/- 0.10) compared to ICU controls (0.48 +/- 0.08, p less than 0.05). Erythrocyte cholesterol was higher in RS patients (79.00 +/- 6.61 micrograms/mg protein) than in ICU controls (59.74 +/- 6.09, p less than 0.05). Erythrocyte malondialdehyde generation was decreased in comatose RS patients (404 +/- 28 nmol malondialdehyde/g hemoglobin) versus ICU (517 +/- 29, p less than 0.05). Although plasma vitamin E was depressed in RS patients, the erythrocyte vitamin E concentrations were no different in RS patients than in ICU patients. All RS patients had a typical viral prodrome and either a history of aspirin intake and/or measurable serum salicylate on admission. All of the biochemical abnormalities in RS patients listed above returned to values comparable to those of healthy RS siblings on recovery. The transient nature of these phenomena suggests that they were related to viral infection and/or aspirin rather than to intrinsic differences in lipid metabolism between RS patients and controls.

Reye's syndrome. An epidemiologic analysis of mild disease

Patients with Reye's syndrome (RS) whose degree of severity was classified as stage 0 (alert and awake) were compared with patients with a severity classification of stage 1 or greater. The Centers for Disease Control case definition and staging criteria were used. Two hundred twenty-seven patients with RS were investigated by the Ohio Department of Health from Dec 1, 1978, through March 31, 1980. There were 67 identified patients who never exceeded stage 0 and 160 patients classified as stage 1 or greater. Both groups of patients were compared according to demographic features, symptomatology, medication use during the antecedent illness, and laboratory findings during the RS illness. Stage 0 patients were similar to patients at stage 1 or greater in their demographic features, illnesses, medications preceding RS, and results of liver function tests; however, values of serum ammonia, creatine phosphokinase, prothrombin time, and bilirubin increased with RS severity.

Serum dicarboxylic acids in patients with Reye syndrome

Reye syndrome resembles disorders of fatty acid metabolism. Analysis of serum free fatty acids from 18 patients with Reye syndrome revealed that dicarboxylic acids comprise as much as 55% (range 4% to 55%) of the patients' total free fatty acids; both medium- (6 to 12 carbon lengths) and long-chain (14 to 18 carbon lengths) dicarboxylic acids were identified. Long-chain dicarboxylic acids were not found in any control samples, whereas 86% +/- 4% of the serum dicarboxylic acids were long chain in 10 patients with Reye syndrome in state 3 to 4 coma and 31% +/- 8% in eight patients with a milder illness. The serum concentration of dicarboxylic acids correlated with the clinical state (P less than 0.001) and with the elevation in blood ammonia concentration (r2 = 0.8767). No long-chain dicarboxylic acids were found in the urine. The dicarboxylic acidemia in Reye syndrome may be secondary to the general mitochondrial dysfunction or could indicate that an insult to fatty acid metabolism or the stimulation of omega-oxidation is important in the pathogenesis of the illness. Measurement of serum dicarboxylic acids, especially long chain, may be important in assessing Reye syndrome and may prove useful in distinguishing this from other diseases.

Serum lipid abnormalities in a chemical/viral mouse model for Reye's syndrome

Neonatal mice given nontoxic dermal applications of an industrial surfactant, Toximul MP8 (Tox), and subsequently infected with sublethal doses of mouse-adapted human Influenza B (Lee) virus (FluB) develop many of the biochemical features of Reye's Syndrome (RS). To determine whether these also include abnormal circulating lipid, we examined serum lipid profiles in the mouse model throughout the treatment course using Iatroscan-TH10. Following 10 days of exposure to surfactant, serum phospholipid and cholesterol levels were significantly reduced relative to control animals. These reductions were transient; however, four days following virus administration, significant differences in serum lipid were again evident. These abnormalities coincided and correlated with increased animal mortality. Animals that received combined Tox + virus treatment had significant decreases in serum total lipids relative to control animals, a reflection of a reduction in all lipid classes, including phospholipid, cholesterol, neutral glycerides (triglycerides plus diglycerides) and free fatty acids. Phospholipid (specifically phosphatidylcholine and lysophosphatidylcholine) and free fatty acid levels in the Tox + virus group were also significantly lower than those in animals that received virus alone. This study has demonstrated that suckling mice given chemical/viral treatment have the serum hypopanlipidemia but not the freefattyacidemia that are characteristic of RS.

Retinol binding protein and prealbumin in Reye's syndrome

Retinol binding protein (RBP) and prealbumin (PA) were analyzed in 29 serum samples from 8 patients with stages II and III Reye's Syndrome (RS), and from 10 healthy fasting children. All RS patients had at least one abnormally low RBP and PA value. A return toward normal was evident within 2-3 days in serial samples. The nadir RBP and PA values in RS (means of 9 and 107 mg/L) were significantly different (p less than 0.001) from those of the controls (RBP mean of 40 and PA of 157 mg/L). A significant correlation was found between RBP and PA serum values in RS (r = 0.7, p less than 0.001); the high admission NH4+ values tended to associate with low RBP levels; however, the correlation was not very high (r = -0.4, p less than 0.01). The presence of an abnormal vitamin A transport system at an early stage of RS raises the possibility of additional abnormalities in vitamin A metabolism in these patients. The findings of reduced serum levels of complement, clotting factors, fibronectin, and now RBP and PA, suggest a marked short-term impairment of hepatic synthesis of proteins and/or their release in RS.

Carnitine status in Reye and Reye-like syndromes

Fourteen children with the following Reye and Reye-like syndromes were studied to determine each patient's carnitine status: valproate-induced Reye-like attack, ornithine transcarbamylase deficiency, systemic carnitine deficiency, methylmalonic acidemia, and propionic acidemia. Reduced free carnitine and increased serum and urine acylcarnitine levels were found in all patients except for 2 with Reye syndrome, in whom serum creatinine levels were mildly elevated and serum free carnitine levels were not reduced. The renal free carnitine reabsorption rate was reduced in all cases. The free carnitine content of autopsied liver samples were reduced in 2 Reye syndrome patients, 2 OTC deficiency patients, and in a single systemic carnitine deficiency patient. The observed secondary free carnitine deficiency may be a factor in the pathogenesis of Reye and Reye-like syndromes.

Reye's syndrome: mitochondrial swelling and Ca2+ release induced by Reye's plasma, allantoin, and salicylate

The effects of Reye's plasma, allantoin, and salicylates on mitochondrial structure and Ca2+ transport have been investigated. Measurements of Ca2+ transport showed that when 20-30 microM Ca2+ was added to isolated rat liver mitochondria preincubated with one of these agents, Ca2+ uptake was followed by its spontaneous release into the medium. This was accompanied by large-amplitude swelling; the onset preceded the Ca2+ release. No further Ca2+ release was induced by uncoupler or the Ca2+ ionophore, A23187. The mitochondria continued to swell even after all of the Ca2+ had been released. The time between the addition of Ca2+ and the onset of swelling (or Ca2+ release) depended on the concentration of the agent added and the preincubation time; the extent of swelling did not. These effects were prevented, but not reversed, by ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, ruthenium red, rotenone, or adenine nucleotides. The massive swelling and membrane disruption were confirmed by electron microscopy of the treated vs untreated mitochondria. Similar results concerning swelling and Ca2+ release were also seen with Ca2+ alone, but the time scale was much longer (i.e., greater than 3-4 min), indicating that these agents act by potentiating Ca2+-induced alterations in mitochondrial structure, as suggested by our earlier work (T.Y. Segalman and C.P. Lee (1982) Arch. Biochem. Biophys. 214, 522-530; M.E. Martens and C.P. Lee (1984) Biochem. Pharmacol. 33, 2869-2876). Our data show, therefore, that allantoin, salicylates, and the "toxic" agent in Reye's plasma severely limit the ability of isolated rat liver mitochondria to maintain their structural integrity under conditions of limited Ca2+ loading.

Serum and urinary carnitine and organic acids in Reye syndrome and Reye-like syndrome

Free and acyl-carnitine in serum and urine, and urinary organic acids were measured in 6 patients with Reye syndrome and Reye-like syndrome. The free and total carnitine concentrations were significantly reduced in serum during the acute phases of the diseases. Thus, the ratio of acylcarnitine to free carnitine was significantly increased. Urinary excretion of acylcarnitine was greatly increased, and the acylcarnitine to total carnitine ratio was therefore greater than in controls. The urinary organic acids comprised large amounts of lactic acid, dicarboxylic acids and ketone bodies. It is suggested that carnitine deficiency is induced as more carnitine is consumed to buffer the increased amount of toxic acyl-CoA compounds metabolized from free fatty acids and the many organic acids. These results indicate that administration of L-carnitine should generally be considered in patients with Reye syndrome and Reye-like syndrome.

Elevated serum gamma-aminobutyric acid levels in children with Reye's syndrome

Elevated serum levels of gamma-aminobutyric acid (GABA), a potent inhibitory neurotransmitter, have recently been implicated in the pathogenesis of hepatic encephalopathy. In this study, serum GABA levels were measured in five children with severe Reye's syndrome, 10 children with acute viral hepatitis, and seven healthy volunteers. Serum GABA levels were highest in the five Reye's syndrome patients. The mean serum GABA level for the Reye's syndrome group (3.0 +/- 1.3 microM, mean +/- SEM) was significantly elevated as compared to the mean of the viral hepatitis group (0.72 +/- 0.07 microM, p less than 0.05) and the healthy volunteers (0.38 +/- 0.04 microM, p less than 0.05). These results provide preliminary evidence to suggest that elevated serum GABA levels may in part be responsible for the encephalopathic state observed in children with Reye's syndrome.

Effect of Reye's syndrome serum on isolated chinchilla liver mitochondria

A general impairment of liver mitochondrial enzymes is central to Reye's syndrome (RS). The respiration of isolated liver mitochondria was measured after the addition of concentrated normal serum or RS serum derived from 12 patients. RS serum stimulates oxygen consumption in isolated rat liver mitochondria. This effect is due to the oxidation of uric acid by peroxisomes contaminating the preparation and a stimulation of mitochondrial respiration (1.05 +/- 0.14 nmol of O2/min X mg of protein; control 0.30 +/- 0.08 nmol O2/min X mg). The stimulation of respiration occurs in the presence of all respiratory substrates, is dependent on the amount of serum added, and represents an uncoupling of oxidative phosphorylation. RS serum reduces ATP formation by 15-76%. The uncoupling effect correlates with the amount of free fatty acid in the serum sample and resembles the effect induced by the addition of a dicarboxylic fatty acid. Dicarboxylic fatty acids, especially long-chain dicarboxylic acids, impair ATP formation. Dicarboxylic acids were found in the serum of all RS patients and comprised as much as 54% of the total serum free fatty acids. 90% of the serum dicarboxylic acids were of 16-18 carbon lengths. The amount of dicarboxylic acids in the RS serum corresponded directly with the reduction in ATP formation by the RS serum. This demonstrates that dicarboxylic acids occur in RS and may be important in the general impairment of mitochondrial function in RS and other disorders where they are present.

Platelet-monoamine oxidase activity in Reye's syndrome

Platelet and liver monoamine oxidase (MAO) activity (mean +/- SD) was evaluated in patients with liver-biopsy-proven Reye's syndrome. MAO was measured by a radioenzymatic technique with [3H]tyramine as a substrate. A marked decrease in MAO activity [3.3 +/- 2.4 nmol of [3H]4-hydroxyphenylacetic acid formed X (mg protein)-1 X h-1] was observed in platelets on admission in all patients (n = 13) with Reye's syndrome when compared with hospitalized patients without liver disease (n = 8) [9.8 +/- 2.5 nmol of [3H]4-hydroxyphenylacetic acid formed X (mg protein)-1 X h-1] and with liver disease (n = 10) [9.1 +/- 2.0 nmol of [3H]4-hydroxyphenylacetic acid formed X (mg protein)-1 X h-1]. Following recovery from the disease, platelet MAO approached levels that were not significantly different from those of controls. Contrastingly, reduction of hepatic MAO in Reye's syndrome was similar to that seen in patients with liver disease of different etiologies. These studies suggest that reduced platelet MAO activity is a specific abnormality in Reye's syndrome, and it may be representative of generalized impairment of mitochondrial function in these patients. Furthermore, the pattern of liver and platelet MAO activity in Reye's syndrome may allow for the differentiation of this disease from other hepatopathologic conditions.

Hepatic and encephalopathic components of Reye's syndrome: factor analysis of admission data from 209 patients

Factor analysis of admission data from 209 Reye's syndrome patients yielded three factors. Factor 1 was associated with encephalopathy, blood ammonia, creatinine kinase (CK), uric acid and, to a lesser extent, bilirubin. This factor was linked to the encephalopathy and hypermetabolic changes in muscle, possibly prostaglandin-mediated proteolysis. Factor 2 was associated with serum alanine aminotransferase (AlaAT) and aspartate aminotransferase (AspAT), and was identified as a hepatic lesion component. These factors correspond to two etiologic components of Reye's syndrome. Salicylate was only weakly associated with neuropathic and hypercatabolic indicators and not at all associated with the hepatic damage indicators.

Urinary dicarboxylic acids in Reye syndrome

Urine from 12 patients with Reye syndrome was examined by gas-liquid chromatography for identification of organic acids. Large amounts of lactic acid, dicarboxylic acids (adipic, suberic, and sebacic), and 3-OH butyric acid were noted. The mean (+/- SD) total dicarboxylic acid concentration was 0.98 +/- 0.24 mg/mg creatinine, compared with 0.006 +/- 0.010 mg/mg creatinine in controls, n = 140; the mean in patients with Reye syndrome was higher (1.40 +/- 0.26 mg/mg creatinine, n = 8) when the samples were obtained prior to initiation of therapy, but declined rapidly after administration of hypertonic glucose, exchange transfusion, and osmotic diuretics. The total urine excretion of dicarboxylic acids plus urine ketones at the time of presentation correlated well with the plasma lactate (r2 = 0.9676) and peak blood ammonia (r2 = 0.9216) levels. Our results document the occurrence of significant dicarboxylic aciduria in Reye syndrome and indicate that fatty acid metabolism is more impaired in this disorder than previously appreciated.

Hypophosphatemia and Reye's syndrome

Hypophosphatemia may occur in Reye's syndrome. We retrospectively studied 42 patients with Reye's syndrome to determine the frequency and degree of hypophosphatemia, to identify possible causes, and to determine whether hypophosphatemia was related to the severity of disease or mortality. Nineteen (46%) patients were hypophosphatemic at the time of hospital admission. Five of these had a serum phosphorus level less than 2.5 mg/dl and three were 1.5 mg/dl or less. During the subsequent hospital course, 32 (78%) patients developed hypophosphatemia. It was of moderate degree (2.5 mg/dl or less) in 20 patients, and was severe (1.5 mg/dl or less) in eight patients. Hypophosphatemia correlated with concurrent hyperglycemia but not with other potential causes studied. The degree of hypophosphatemia during treatment roughly paralleled the severity of illness but was not a predictor of outcome. The need for treatment of hypophosphatemia in Reye's syndrome has not been established, and hypocalcemia as a complication of excess phosphate infusion should be avoided.

Leukocyte tubuloreticular inclusions in Reye's syndrome

Tubuloreticular inclusions (TRI) have been observed in the rough endoplasmic reticulum of blood lymphocytes and monocytes in two cases of Reye's syndrome initiated by influenza infections. Tubuloreticular inclusions are seen in these mononuclear leukocytes during the acute phase of illness, but not during convalescence. Since TRI have been demonstrated in peripheral mononuclear leukocytes in patients with acquired immunodeficiency syndrome, systemic lupus erythematosus, and certain viral infections including T-cell leukemia, it may be that the finding of TRI in Reye's syndrome reflects a viral infection and/or immune dysfunction, if such association is not proved to be fortuitous.

Confirmation of serum salicylate levels in Reye's syndrome: a comparison between the Natelson colorimetric method and high performance liquid chromatography

Serum was obtained from 11 patients with Reye's syndrome at admission and analyzed for the presence of salicylates by the Natelson colorimetric technique and high performance liquid chromatography. Salicylate levels obtained by the Natelson method had a mean of 6.00 mg/dl +/- 4.58; the mean HPLC salicylic acid level was 5.09 mg/dl +/- 5.14. The correlation coefficient was 0.985 with a linear regression line y = 0.8788x + 1.527. No other salicylate metabolites nor interfering substances were identified. Once the accuracy of the Natelson method was confirmed, the charts of 82 patients were reviewed for admission salicylate levels. The overall mean was 8.63 mg/dl (survivors, 8.45 mg/dl +/- 8.56; fatalities, 9.28 mg/dl +/- 5.34). There was no correlation found between admission salicylate level and peak ammonia level, another important index of disease severity.

Metabolic and mitochondrial morphological changes that mimic Reye syndrome after endotoxin administration to rats

The administration of sublethal doses of Escherichia coli O111:B4 endotoxin to starved rats results in significant increases in plasma ammonia, free fatty acids, and serum lactate compared with starved controls. These metabolic alterations are associated with Reye syndrome-like histological findings of hepatic microvesicular fatty accumulation and hepatic ultrastructural evidence of mitochondrial pleomorphism with matrix disruption. This sublethal endotoxin model may help elucidate the relationship between the hepatic mitochondrial injury, characteristic metabolic impairment, and encephalopathy seen in patients with Reye syndrome.

Short-chain fatty acids and encephalopathy of Reye's syndrome

Plasma levels of six short-chain fatty acids (SCFA) were measured in 23 Reye's syndrome patients. In sequential measurements, only propionic acid correlated closely with neurologic severity. Although admission SCFA levels were slightly elevated, there were no significant differences between patients grouped by severity of encephalopathy. Admission SCFA did not predict neurologic outcome; also, they correlated poorly with admission blood ammonia, amino acid nitrogen, and lactate.

Hypercatecholaminemia in Reye's syndrome

To evaluate the role of catecholamines in Reye's syndrome, a specific and sensitive radioenzymatic assay was used to study plasma and CSF concentration of dopamine, norepinephrine, and epinephrine in 14 patients with liver-biopsy-proven Reye's syndrome. The results (median and range) revealed significant (P less than .04, P less than .0024, and P less than .030, respectively) elevation in plasma dopamine (131, 0 to 1,193 pg/mL), norepinephrine (1,455, 20 to 5,271 pg/mL), and epinephrine (345, 7.6 to 2,504 pg/mL) at the onset of the disease when compared with the level of these neurotransmitters in a group of hospitalized patients without hepatic disorders. There was a positive correlation between plasma catecholamines and stage of coma on admission (r = .54 to .86; P less than .001 to .024). Furthermore, the concentration of dopamine, norepinephrine, and epinephrine in the CSF increased significantly during the development of cerebral edema in all patients with Reye's syndrome as compared with concentrations in a control population. Hypercatecholaminemia may contribute to the encephalopathy of Reye's syndrome.