Neuronal properties of clonal hybrid cell lines derived from central cholinergic neurons.

Clonal cell lines derived from specific types of central neurons can be used to identify and characterize properties specific to those neurons. With somatic cell fusion techniques, nine clonal hybrid cell lines have been developed from the septal region of the mouse basal forebrain. Two lines express characteristics typical of cholinergic neurons--choline acetyltransferase activity and immunoreactivity, neurite formation with neurofilament protein immunoreactivity, and aggregation in rotation-mediated cell culture. These cell lines may be useful for studying the trophic interactions that support the development and maintenance of central cholinergic connections.

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.

Binding of straight-chain saturated dicarboxylic acids to albumin.

Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome. Long-chain dicarboxylic acids have profound effects on the function and structure of isolated mitochondria, suggesting that they could contribute to the mitochondrial dysfunction in Reye's syndrome. Binding of fatty acids to albumin and the intracellular fatty acid-binding proteins is important in regulating the transport and metabolism of fatty acids and protects against the toxic effects of unbound fatty acids. We studied the binding of dicarboxylic acids to defatted albumin using equilibrium dialysis to assess to what extent dicarboxylic acids are likely to be bound in the plasma of patients. Dicarboxylic acids bind weakly to albumin in a molar ratio of 3.8, 4.2, 1.6, 0.8, and 0.7 to 1 for octadecanedioic, hexadecanedioic, tetradecanedioic, dodecanedioic, and decanedioic acid, respectively. The dissociation constants for long-chain dicarboxylic acids are 100-1,000-fold larger than those of comparable monocarboxylic acids. Oleate competes with dicarboxylic acid and reduces the moles of dicarboxylic acid bound per mol of albumin to less than 1. Octanoate inhibits dicarboxylic acid binding. Our observations indicate that in Reye's syndrome, substantial concentrations of dicarboxylic acids of patients may be free and potentially toxic to mitochondria and other cellular processes.

Induction of omega-oxidation of monocarboxylic acids in rats by acetylsalicylic acid.

The accumulation of dicarboxylic acids, particularly long chain, is a prominent feature of Reye's syndrome and diseases of peroxisomal metabolism. We assessed the omega-oxidation of a spectrum of fatty acids in rats and asked whether pretreatment of rats with aspirin, which is known to predispose children to Reye's syndrome, would affect omega-oxidation of long chain fatty acids. We found that aspirin increased liver free fatty acids and increased the capacity for omega-oxidation three- to sevenfold. Omega-oxidation of long chain substrate was stimulated to a greater degree than medium chain substrate and was apparent within one day of treatment, at serum aspirin concentrations below the therapeutic range in humans. The apparent Km for lauric acid was 0.9 microM and 12 microM for palmitate. We also found a difference in the storage stability of activity toward medium and long chain substrate. Saturating concentrations of palmitate had no effect on the formation of dodecanedioic acid, whereas laurate decreased but never eliminated the omega-oxidation of palmitate. 97% of the total laurate omega-oxidative activity recovered was found in the microsomes, but 32% of palmitate omega-oxidative activity was present in the cytosol. These results demonstrate that aspirin is a potent stimulator of omega-oxidation and suggest that there may be multiple enzymes for omega-oxidation with overlapping substrate specificity.

Impaired fatty acid oxidation in children on valproic acid and the effect of L-carnitine.

Fatty acid oxidation was studied in 12 patients (aged 3 to 19 years) receiving valproic acid (VPA), predominantly as monotherapy, before and after 1 month of L-carnitine supplementation (50 mg/kg/day po) in order to determine whether L-carnitine plays a role in preventing the hepatotoxic effects of this drug. Five of these patients were also studied prior to VPA treatment. Only one patient taking VPA had an abnormally low plasma free carnitine. Acyl-/free carnitine ratios were elevated in five patients on VPA and normalized after L-carnitine supplementation. Mean plasma concentrations of free fatty acids, beta-OH-butyrate, and cumulative excretion of 13CO2 after administration of 1-13C-octanoic acid were not changed by VPA or L-carnitine treatment. Urinary dicarboxylic acids, acylglycines, and octanoylcarnitine were elevated during VPA therapy and unaltered by L-carnitine. These results suggest that, in patients at low risk for VPA-induced hepatotoxicity (patients aged > 2 years and taking VPA as monotherapy), VPA causes metabolic abnormalities resembling those found in inborn errors of mitochondrial beta-oxidation which are not corrected by L-carnitine.

CT imaging in adults with neurofibromatosis-1: frequent asymptomatic plexiform lesions.

OBJECTIVE: The authors examined the incidence and radiologic characteristics of plexiform neurofibromas in neurofibromatosis-1 (NF-1) to define a cohort at greatest risk for malignant nerve-sheath tumors. BACKGROUND: Plexiform neurofibromas are a frequent complication of NF-1. They can impair function, produce disfigurement, and be the site for the development of malignant nerve-sheath tumors. The incidence and natural history of plexiform neurofibromas is unknown. METHODS: CT imaging of the chest, abdomen, and pelvis was performed in 91 of 125 consecutive adults (age, > or = 16 years) with NF-1. RESULTS: Twenty percent of patients had plexiform neurofibromas of the chest in the paraspinal, mediastinal, or supraclavicular area. Approximately 40% of patients had abnormal abdominal/pelvic scans. The paraspinal, sacral plexus, sciatic notch, and perirectal regions were the most common sites. Most plexiform neurofibromas were asymptomatic. Imaging also revealed a number of tumors, including malignant nerve-sheath tumors, adrenal tumors, carcinoids, and schwannomas. CONCLUSIONS: The frequency of plexiform lesions and other tumors in NF-1 indicates that clinicians should monitor young adults carefully; however, imaging characteristics alone cannot reliably distinguish benign from malignant lesions.

Lactic acidemia in Reye's syndrome.

Plasma lactate level was measured in 21 patients with Reye's syndrome and was compared with neurologic state as rated on a simple coma scale. Significant elevations in plasma lactate, ranging from 2 to 15 mEq/liter, were noted in all patients. There was a close correspondence between stage of coma at the time the sample was drawn and lactate levels. The correlation of plasma lactate level with clinical stage could not be accounted for by differences in glucose. PO2, PCO2, pH, blood pressure, or serum osmolality. In contrast, blood ammonia level correlated with the severity of the encephalopathy early in the course only and often returned to normal in patients with persistent coma. Only measurements of hepatic dysfunction such as SGOT and SGPT levels of failed to correlate with clinical state. All patients had a metabolic acidosis; in five patients it was uncompensated. Lactate accounted for nearly all (mean 81%) of the observed base deficit. The findings suggest that lactic acidemia is an important metabolic component of Reye's syndrome.

Do NF1 gene deletions result in a characteristic phenotype?

Neurofibromatosis-1 (NF1) is an autosomal dominant disorder with marked variability of expression. Analysis of the NF1 gene (NF1) has detected a variety of mutations without any clear correlation with phenotype. However, deletions which remove all of NF1 have been reported in a small number of patients who have minor facial abnormalities, mental retardation, learning disabilities, and early or excessive burden of cutaneous or plexiform neurofibromas. The purpose of this study was to determine whether these phenotypic traits are associated with whole gene deletions. Out of 406 of our NF1 patients, 70 patients had manifestations previously associated with gene deletions. Thirty-five of these patients from 26 families were available for study. By fluorescence in situ hybridization (FISH) analysis, 4 were found to have deletions of the entire gene, including 2 sporadic cases, 1 familial case, and 1 case where family history could not be verified. In addition, the mother of the familial case was found to be mosaic for the deletion. Our results suggest that although large NF1 deletions occur with relatively high frequency in patients with certain findings, the presence of a deletion cannot be predicted solely on the basis of clinical phenotype.

Descriptive analysis of tibial pseudarthrosis in patients with neurofibromatosis 1.

Five percent of individuals with neurofibromatosis type 1 (NF1) present with congenital long bone pseudarthrosis (PA). In large series, 50-80% of patients with congenital long bone PA also have NF1. Very little information exists on the natural history and pathogenesis of PA in NF1. This report is a descriptive analysis of a large series of patients with NF1 and tibial bowing or PA. Study A is a case-control study using the National Neurofibromatosis Foundation International Database (NNFFID). Eighty-five patients with PA were compared to a control group from the same database. There was a statistically significant male predominance of NF1 cases with PA (54 males to 31 females), compared to controls (85 males to 87 females) (chi2 = 4.0, P = 0.046, using a two-tailed test with Yates' correction). There was no significant difference in the clinical presentation of NF1 manifestations in NF1 patients with PA than in NF1 patients without PA. Of the affected individuals with PA, there were 24 de novo cases and 21 familial cases (9 through maternal and 12 through paternal inheritance). Questions that could not be answered by Study A were addressed by a partially overlapping case-series report, Study B, in which data on 75 cases ascertained through questionnaires completed by NF center directors were collected. From Study B we determined that half of the patients who had a fracture sustained it before age 2, and approximately 16% of the pseudarthrosis patients had an amputation. Our data indicate a male predominance and no parent-of-origin effect. Male gender may be a susceptibility factor for pseudarthrosis in NF1.

Development and characterization of clonal cell lines derived from septal cholinergic neurons.

Studies employing primary cells to determine the molecular basis of neuronal development and selective synaptogenesis in the central nervous system are limited by cellular heterogeneity. Clonal hybrid cell lines derived from a particular region of brain, which express differentiated characteristics typical of the cells of origin, offer a potentially powerful alternative approach. We previously demonstrated the feasibility of deriving such cell lines from septal cholinergic cells. We now delineate the methods employed, and describe the development of additional cholinergic cell lines expressing neuronal and cholinergic features from later developmental stages. One cell line has been studied in detail and found to form neurites, express choline acetyltransferase (ChAT) and neurofilament protein (NFP), and display typical neuronal ultrastructural characteristics, including puncta adherens, neuritic varicosities, vesicles, and growth cones.

A child with neurofibromatosis-1 and a lumbar epidural arteriovenous malformation.

A 10-year-old child with neurofibromatosis-1 was evaluated for progressive lumbar scoliosis, back pain, and foot numbness. Magnetic resonance imaging showed several lumbar intraspinal and extraspinal masses consistent with neurofibromas. The mass at L3-L5 compressed the thecal sac and was thought to be the source of the symptoms. On operative exploration, a lumbar epidural arteriovenous malformation was found, which was removed in its entirety. The child's back pain and foot numbness resolved. Epidural arteriovenous malformations in patients with neurofibromatosis-1 are rare and have been reported only in the cervical spine. Our finding of a lumbar epidural arteriovenous malformation in a child with neurofibromatosis-1 demonstrates that vascular anomalies can be present throughout the spine of patients with neurofibromatosis-1 and should be considered in the differential diagnosis of any neurofibromatosis-1-related epidural mass.

Cerebral malformations in Carpenter syndrome.

The inherited forms of craniosynostosis can be divided into 4 groups: isolated craniosynostosis, craniosynostosis with syndactyly, craniosynostosis with polydactyly and syndactyly, and craniosynostosis with other somatic abnormalities. Acrocephalopolysyndactyly or Carpenter syndrome consists of craniosynostosis, short fingers, soft tissue syndactyly, preaxial polydactyly, congenital heart disease, hypogenitalism, obesity, and umbilical hernia. As many as three-fourths of the patients have some degree of intellectual impairment. The etiology of mental retardation in this syndrome has not been explored. A patient is reported with the features of Carpenter syndrome who has profound developmental delay and cerebral malformations demonstrated by magnetic resonance imaging and computed tomography. Because mental retardation is not an invariable feature of this syndrome or other craniosynostosis syndromes, neuroradiologic examination may help in predicting the intellectual outcome in these patients.

Kluver-Bucy syndrome in children.

Kluver-Bucy syndrome is an uncommon syndrome of behavioral abnormalities following bilateral temporal lobe injury. Only four children have been reported previously with this syndrome. We report three additional pediatric patients who developed Kluver-Bucy syndrome following hypoxic insults. In two patients, features of the syndrome were transient. Problems in intermediate memory were present in each patient. Behavioral abnormalities did not respond to the medications administered. Our experience suggests that Kluver-Bucy syndrome may occur more commonly in children than was suspected previously, especially following hypoxia.

Defect in fatty acid oxidation: laboratory and pathologic findings in a patient.

The clinical, laboratory, and pathologic findings in a patient with a previously undescribed deficiency in fatty acid oxidation are summarized. The patient had a fatal defect in fatty acid metabolism profoundly affecting heart, skeletal muscle, liver, and kidney. Oxidation of palmitate was 38-51% of controls. Complementation assays demonstrated that the patient's fibroblasts complemented fibroblast lines from all known defects in fatty acid oxidation except long-chain acyl-CoA dehydrogenase deficiency. Urine and serum carnitine profiles also were indicative of a defect in the oxidation of long-chain substrate; however, the palmitoyl-CoA dehydrogenase activity was actually increased. This finding indicates that the patient had a defect that was distinct from, but possibly related to, long-chain acyl-CoA dehydrogenase deficiency. This patient demonstrates the laboratory and pathologic findings in defects in fatty acid oxidation and how they differ from those in Reye syndrome.

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.

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.

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.

Characterization of the binding sites for dicarboxylic acids on bovine serum albumin.

Dicarboxylic acids are prominent features of several diseases, including Reye's syndrome and inborn errors of mitochondrial and peroxisomal fatty acid oxidation. Moreover, dicarboxylic acids are potentially toxic to cellular processes. Previous studies [Tonsgard, Mendelson & Meredith (1988) J. Clin. Invest. 82, 1567-1573] demonstrated that long-chain dicarboxylic acids have a single high-affinity binding site and between one and three lower-affinity sites on albumin. Medium-chain-length dicarboxylic acids have a single low-affinity site. We further characterized dicarboxylic acid binding to albumin in order to understand the potential effects of drugs and other ligands on dicarboxylic acid binding and toxicity. Progesterone and oleate competitively inhibit octadecanedioic acid binding to the single high-affinity site. Octanoate inhibits binding to the low-affinity sites. Dansylated probes for subdomain 2AB inhibit dodecanedioic acid binding whereas probes for subdomain 3AB do not. In contrast, low concentrations of octadecanedioic acid inhibit the binding of dansylated probes to subdomain 3AB and 2AB. L-Tryptophan, which binds in subdomain 3AB, inhibits hexadecanedioic acid binding but has no effect on dodecanedioic acid. Bilirubin and acetylsalicylic acid, which bind in subdomain 2AB, inhibit the binding of medium-chain and long-chain dicarboxylic acids. Our results suggest that long-chain dicarboxylic acids bind in subdomains 2C, 3AB and 2AB. The single low-affinity binding site for medium-chain dicarboxylic acids is in subdomain 2AB. These studies suggest that dicarboxylic acids are likely to be unbound in disease states and may be potentially toxic.