Allan L. Sherwin

Congenital malformations due to antiepileptic drugs

To identify the major risk factors for the increased incidence of congenital malformations in offspring of mothers being treated for epilepsy with antiepileptic drugs (AEDs) during pregnancy and, to determine the relative teratogenic risk of AEDs, we prospectively analyzed 983 offspring born in Japan, Italy, and Canada. The incidence of congenital malformations in offspring without drug exposure was 3.1%, versus an incidence with drug exposure of 9.0%. The highest incidence in offspring exposed to a single AED occurred with primidone (PRM; 14.3%), which was followed by valproate (VPA; 11.1%), phenytoin (PHT; 9.1%), carbamazepine (CBZ; 5.7%), and phenobarbital (PB; 5.1%). The VPA dose and level positively correlated with the incidence of malformations. This study first determined a cut-off value of VPA dose and level at 1000 mg/day and 70 microg/ml, respectively, to avoid the occurrence of malformations. The incidence of malformations increases as the number of drugs increases, and as the total daily dose increases. Specific combinations of AEDs such as VPA + CBZ and PHT + PRM + PB produced a higher incidence of congenital malformations. The incidence of malformations was not associated with any background factors studied except for the presence of malformations in siblings. These results indicate that the increased incidence of congenital malformations was caused primarily by AEDs, suggesting that malformations can be prevented by improvements in drug regimen, and by avoiding polypharmacy and high levels of VPA (more than 70 microg/ml) in the treatment of epileptic women of childbearimg age.

Amino acid content of epileptogenic human brain: Focal versus surrounding regions

Abstract Amino acid analysis of tissue samples obtained from epileptogenic foci and surrounding cortical tissues in human brain indicated that the metabolism of certain amino acids is impaired throughout the cortex whereas for others the abnormality is more restricted to the site of maximal epileptogenic activity. The levels of GABA and aspartic acid were below normal in all regions sampled. In contrast, concentrations of glutamic acid and taurine lower than normal together with very high glycine levels were predominantly associated with the most hyperexcitable areas. The concentrations of alanine and serine were for the most part normal in both the focus and areas more distant to that site. A comparison of the amino acid levels in focal and surrounding tissue of the same patient demonstrated that the focal area most often contained the lowest concentrations of glutamic acid, aspartic acid and taurine in combination with the highest glycine content. The results are believed to indicate that in epileptogenic human cortex an uncoupling has occured between glucose oxidation and amino acid metabolism. In addition, or as a consequence of this abnormality, an impairment of protein metabolism may also be present.

Excitatory amino acids are elevated in human epileptic cerebral cortex

We used intraoperative electrocorticography to identify and compare specimens from two groups of patients undergoing temporal lobectomy: (1) spiking cortex (12 patients)—epileptic activity recorded over much of the temporal convexity; and (2) nonspiking cortex (9 patients)—temporal convexity free of interictal spiking, epileptic activity confined to the hippocampus and/or amygdala. Comparative amino acid levels were (μmol/g protein, mean ±: SEM): glutamate—spiking 109.8 ±: 1.8, nonspiking 87.4 ±: 2.0 (p < 0.001); aspartate—spiking 15.2 ±: 0.9, nonspiking 12.2 ±: 0.5 (p < 0.05); GABA—spiking 15.0 ±: 1.0, nonspiking 13.9 ±: 1.4 (NS); taurine—spiking 14.5 ±: 0.8, nonspiking 12.2 ±: 0.8 (NS); and glycine—spiking 11.5 ±: 0.8, nonspiking 7.4 ±: 0.6 (p < 0.01). Cortical epileptic activity appears to be associated with elevated concentrations of glutamate, aspartate, and glycine, but not GABA and taurine, perhaps indicating a relative imbalance between putative excitatory and inhibitory amino acid neurotransmitters.

Neuroactive amino acids in focally epileptic human brain : A review

Studies of neuroactive amino acids and their regulatory enzymes in surgically excised focally epileptic human brain are reviewed. Concentrations of glutamate, aspartate and glycine are significantly increased in epileptogenic cerebral cortex. The activities of the enzymes, glutamate dehydrogenase and aspartate aminotransferase, involved in glutamate and aspartate metabolism are also increased. Polyamine synthesis is enhanced in epileptogenic cortex and may contribute to the activation of N-methyl-D-aspartate (NMDA) receptors. Nuclear magnetic resonance spectroscopy (NMRS) reveals that patients with poorly controlled complex partial seizures have a significant diminution in occipital lobe gamma aminobutyric acid (GABA) concentration. The activity of the enzyme GABA-aminotransaminase (GABA-T) which catalyzes GABA degredation is not altered in epileptogenic cortex. NMRS studies show that vigabatrin, a GABA-T inhibitor and effective antiepileptic, significantly increases brain GABA. Glutamate decarboxylase (GAD), responsible for GABA synthesis, is diminished in interneurons in discrete regions of epileptogenic cortex and hippocampus. In vivo microdialysis performed in epilepsy surgery patients provides measurements of extracellular amino acid levels during spontaneous seizures. Glutamate concentrations are higher in epileptic hippocampi and increase before seizure onset reaching potentially excitotoxic levels. Frontal or temporal cortical epileptogenic foci also release aspartate, glutamate and serine particularly during intense seizures or status epilepticus. GABA in contrast, exhibits a delayed and feeble rise in the epileptic hippocampus possibly due to a reduction in the number and/or efficiency of GABA transporters.

Prolonged focal cerebral edema associated with partial status epilepticus.

Summary: Following several days of partial status epilepticus, three patients developed striking focal cerebral edema as demonstrated by computed axial tomography (CT) scan. An angiogram done in one patient showed a capillary blush and early cortical draining veins in the corresponding area. All patients developed severe focal neurological deficit which resolved as the edema improved, and this was demonstrated on serial CT scans (at 6 months, 1 month, and 2 months, respectively). In the first patient, an underlying tumor, and in the second and third, vascular occlusions, were suspected because we were not aware that edema due to status epilepticus could produce changes of such intensity and duration. The neurological disability after the partial status was long‐lasting but reversed completely in our patients. Maximal radiological changes occurred in the area of maximal epileptic discharge. Minimal atrophic changes persisted in two of the three patients. The clinical, CT scan, and angiographic findings suggest that partial status epilepticus can be associated with abnormal vascular permeability leading to prolonged focal cerebral edema. Similar pathophysiology of lesser intensity may be responsible for shorter postictal neurological deficits. Awareness of this clinical and radiological entity should avoid misdiagnosis of cerebral tumor or infarction.

Phospholipid biosynthetic enzymes in human brain

Growing evidence suggests an involvement of brain membrane phospholipid metabolism in a variety of neurodegenerative and psychiatric conditions. This has prompted the use of drugs (e.g., CDPcholine) aimed at elevating the rate of neural membrane synthesis. However, no information is available regarding the human brain enzymes of phospholipid synthesis which these drugs affect. Thus, the objective of our study was to characterize the enzymes involved, in particular, whether differences existed in the relative affinity of substrates for the enzymes of phosphatidylethanolamine (PE) compared to those of phosphatidylcholine (PC) synthesis. The concentration of choline in rapidly frozen human brain biopsies ranged from 32–186 nmol/g tissue, a concentration similar to that determined previously for ethanolamine. Since human brain ethanolamine kinase possessed a much lower affinity for ethanolamine (Km=460 μM) than choline kinase did for choline (Km=17 μM), the activity of ethanolamine kinase in vivo may be more dependent on substrate availability than that of choline kinase. In addition, whereas ethanolamine kinase was inhibited by choline, and to a lesser extent by phosphocholine, choline kinase activity was unaffected by the presence of ethanolamine, or phosphoethanolamine, and only weakly inhibited by phosphocholine. Phosphoethanolamine cytidylyl-transferase (PECT) and phosphocholine cytidylyltransferase (PCCT) also displayed dissimilar characteristics, with PECT and PCCT being located predominantly in the cytosolic and particulate fractions, respectively. Both PECT and PCCT exhibited a low affinity for CTP (Km approximately 1.2 mM), suggesting that the activities of these enzymes, and by implication, the rate of phospholipid synthesis, are highly dependent upon the cellular concentration of CTP. In conclusion, our data indicate different regulatory properties of PE and PC synthesis in human brain, and suggest that the rate of PE synthesis may be more dependent upon substrate (ethanolamine) availability than that of PC synthesis.

Enzyme changes in actively spiking areas of human epileptic cerebral cortex

Five enzymes involved in glutamic acid, GABA, and catecholamine metabolism were measured in epileptic human brain. Electrocorticographically defined areas of focal spiking were compared with samples from surrounding nonspiking cortex. Comparative enzyme activities were as follows (μmol/h/g wet wt): glutamic acid dehydrogenase (GDH)-spiking 135.77 ± 10.22 (mean ± SEM), nonspikingll8.58 ± 9.42 (p < 0.001, N = 17); gluotamicacid decarboxylase—spiking 10.63 ± 0.95, nonspiking 9.96 ± 1.10 (NS, N = 13); GABA-aminotransferase—spiking 36.49 ± 1.05, nonspiking 36.46 ± 1.48 (NS, N = 12); glutamine synthetase-spiking 96.94 ± 3.81, nonspiking 96.52 ± 4.10 (NS, N = 20); and tyrosine hydroxylase (TH; nmol/h/g)-spiking 16.23 ± 2.39, nonspiking 10.67 ± 1.95 (p < 0.001, N = 14). Increased activity of GDH and TH may prove useful to characterize further areas of active spiking in human focal epilepsy.

Brain antioxidant systems in human methamphetamine users

Animal data suggest that the widely abused psychostimulant methamphetamine can damage brain dopamine neurones by causing dopamine‐dependent oxidative stress; however, the relevance to human methamphetamine users is unclear. We measured levels of key antioxidant defences [reduced (GSH) and oxidized (GSSG) glutathione, six major GSH system enzymes, copper–zinc superoxide dismutase (CuZnSOD), uric acid] that are often altered after exposure to oxidative stress, in autopsied brain of human methamphetamine users and matched controls. Changes in the total (n = 20) methamphetamine group were limited to the dopamine‐rich caudate (the striatal subdivision with the most severe dopamine loss) in which only activity of CuZnSOD (+ 14%) and GSSG levels (+ 58%) were changed. In the six methamphetamine users with severe (− 72 to − 97%) caudate dopamine loss, caudate CuZnSOD activity (+ 20%) and uric acid levels (+ 63%) were increased with a trend for decreased (− 35%) GSH concentration. Our data suggest that brain levels of many antioxidant systems are preserved in methamphetamine users and that GSH depletion, commonly observed during severe oxidative stress, might occur only with severe dopamine loss. Increased CuZnSOD and uric acid might reflect compensatory responses to oxidative stress. Future studies are necessary to establish whether these changes are associated with oxidative brain damage in human methamphetamine users.

Fluorescence technique to demonstrate creatine phosphokinase isozymes

Abstract A rapid fluorescence technique is described for the visualization of the isozymes of creatine phosphokinase following electrophoresis on thin-layer agarose gel. The isozyme pattern of a variety of organs and several human pathological sera have been determined. In diseases associated with elevated serum creatine phosphokinase the isozyme pattern observed in the serum resembled that of the tissues affected by the pathological process.

Response of generalized penicillin epilepsy in the cat to ethosuximide and diphenylhydantoin

The effects of ethosuximide and diphenylhydantoin sodium on feline generalized penicillin epilepsy, a model of human generalized corticoreticular (centrencephalic) epilepsy, were compared. Epileptic bursts in the electroencephalogram (EEG) were significantly reduced following administration of ethosuximide with plasma levels of 60 μg per milliliter, and there was a linear correlation between the plasma level and antiepileptic effect (p <0.01). Diphenylhydantoin produced a lesser reduction in epileptic activity, and there was no correlation between the plasma level and effect. Four cats that received both drugs successively responded well to ethosuximide, while only two responded to diphenylhydantoin. The good response to ethosuximide is in accord with clinical experience in human generalized corticoreticular epilepsy.