Is plasma serine a marker for psychosis?

There is some disagreement in the literature concerning the use of plasma serine concentrations as a biological marker for psychoses including schizophrenia. The groups studying this phenomenon have used different methodologies, including gas chromatography and classical amino acid analysis. In the present study, using high pressure liquid chromatography to analyze plasma amino acids from schizophrenics and controls, we found no difference in plasma serine concentrations. None of the plasma amino acid concentrations that were measured differed significantly between schizophrenics and controls but the basic amino acids tended toward higher concentrations in schizophrenics.

Effect of methionine-loading on methyl group synthesis and activation in rat brain and liver.

Much greater increases in S-adenosylmethionine concentrations are observed in the liver in response to methionine-loading than in the brain due to differences in the methionine adenosyltransferase activities in these tissues. Liver methione adenosyltransferase exhibits a bimodal saturation curve with a nonlinear Line-weaver-Burk plot, indicating that high methionine concentrations are required for saturation. In the brain the methionine adenosyltransferase is saturated in vitro at a methionine concentration less than the normal physiological concentration. The increased S-adenosylmethionine concentrations in the livers of methionine-treated rats also account for the observed inhibition of N5,N10-methylenetetrahydrofolate reductase activity in this tissue. No inhibition of this enzyme is observed in the brain of methionine treated animals. Nor are S-adenosylmethionine concentrations increased significantly in brain. Serine hydroxymethyltransferase activity responds to methionine-loading by decreasing in brain and increasing in liver.

Fluorescent immunoassay for determining antiepileptic drug concentrations: clinical usefulness.

The need for rapid and accurate antiepileptic drug measurement in blood is well established. A substrate-labeled fluorescent immunoassay (FIA) has been developed that can measure phenobarbital, phenytoin, primidone, and carbamazepine in serum. To our knowledge, the primidone and carbamazepine assays have not previously been tested in a field trial. We compared FIA and the well-established antiepileptic drug immunoassay technique EMIT for the quantitation of both carbamazepine and primidone. In our hands, the FIA method compared favorably with the EMIT method for accuracy and reliability but is somewhat more time consuming. This method has the advantage of being more sensitive, however, and requires only a finger-stick blood sample. Because of this and the simplicity of the equipment required, the FIA system should also be relatively inexpensive to set up and to operate.

Interactions between folates and carbamazepine or valproate in the rat.

Carbamazepine and valproate each afforded protection against seizures induced by electroshock or by inhalation of hexafluorodiethyl ether (HFDE). After injections of either anticonvulsant for 10 days, plasma folate concentration decreased, but brain folate concentration did not change. Folinic acid administration had no effect on the concentration of either anticonvulsant in plasma or brain. These findings are in contrast with the demonstrated effects of other anticonvulsants on folate biochemistry.

Association of low blood manganese concentrations with epilepsy.

A comparison of hospitalized epileptic patients with matched normals showed that the mean whole blood manganese (Mn) concentration of the epileptic population was significantly lower than the mean of the normal population. The whole blood Mn concentration in the epileptics did not correlate either with seizure frequency or with anticonvulsant therapy. It was observed, however, that patients whose epilepsy was a result of trauma had significantly higher blood Mn concentrations than patients whose history was negative for trauma.

Effect of kainate-induced seizures on tissue trace element concentrations in the rat.

It has been shown that epileptics have lower mean blood concentration of manganese than do controls but the cause of this abnormality has not been determined. In order to investigate the effects of seizures on manganese distribution in the body, rats were treated with kainic acid to produce spontaneous seizures which were quantitated for number and severity. Manganese, zinc, copper and iron concentrations were determined in blood, brain, liver, heart and kidney. Kainate-treated animals ate more food but gained less weight than controls. Liver and kidney manganese concentrations were significantly higher in kainate-treated animals than in controls. Blood manganese concentration showed a significant negative correlation with seizure index while heart manganese concentration showed a significant positive correlation with seizure index. None of the other trace elements showed a significant correlation between trace element concentration and seizure index in any of the tissues, although iron concentration was lower in brain and copper concentration was lower in kidney of kainate-treated animals than in their appropriate controls. These data show that manganese concentrations are generally elevated in tissues of kainate-treated animals. This increased manganese concentration may be related to the increased energy demand of these animals.

Effect of chronic phenobarbital treatment on folates and one-carbon enzymes in the rat.

Chronic oral phenobarbital treatment (50 mg/kg every 12 hr for 8 weeks), which was nontoxic and continuously protective against seizures in rats, significantly decreased folate concentration in liver (29%) but not in brain or plasma. The apparent activity of 5,10-methylenetetrahydrofolate reductase (MTR) in liver decreased with initiation of treatment but then increased with a significant correlation to the length of treatment. Phenobarbital also stimulated the activity of this enzyme slightly in vitro. Methionine adenosyltransferase (MAT) activity was inhibited by high concentrations of phenobarbital in vitro but was not affected in vivo. No significant effects of phenobarbital on the activities of serine hydroxymethyltransferase (SHMT) or 5-methyltetrahydrofolate:homocysteine methyltransferase (MHMT) were observed either in vivo or in vitro.

Effect of chronic primidone treatment on folate-dependent one-carbon metabolism in the rat.

Rats were treated chronically with primidone (100 mg/kg/12 hr, p.o.) for up to 8 weeks. The effects of this treatment on one-carbon metabolism were determined in brain and liver. Serine hydroxymethyltransferase activity increased in both brain (44%) and liver (50%). Methylenetetrahydrofolate reductase activity increased in liver (26%) with a significant correlation to the length of treatment, but in brain it was unchanged. Methyltetrahydrofolate:homocysteine methyltransferase activity increased in brain (43%) with a significant correlation to length of treatment, but in liver no effect was observed. Methionine adenosyltransferase activity in brain was significantly lower than control at only one point after 8 weeks of chronic treatment. S-Adenosylmethionine concentration in liver increased gradually (23%) during treatment. S-Adenosylhomocysteine concentrations decreased in brain (33%) and increased in liver (23%) with chronic primidone treatment. These data support the hypothesis that chronic primidone treatment leads to folate depletion through interference with folate metabolism.

Chronic sodium valproate treatment in the rat: toxicity versus protection against seizures induced by indoklon.

A model for chronic treatment of rats with sodium valproate has been developed balancing efficacy, toxicity and dose control. The dose (300 mg/kg) and frequency (every 8 h) selected were somewhat toxic as measured by weight gain and failed to provide continuous protection against Indoklon induced seizures but yielded plasma valproate levels near the range of therapeutic human levels. Chronic treatment of rats at this dose and frequency yielded a significant negative correlation between weight gain and length of treatment as well as a significant negative correlation between plasma valproate concentration and length of treatment. It was concluded that due to the short half-life of valproate in rats it is impossible to maintain continuously protective, nontoxic levels of valproate with a reasonable frequency (every 8 h) of controlled dose administration.

Comparison of fluorescent immunoassay (FIA) and enzyme-multiplied immunoassay technique (EMIT) for measurement of serum carbamazepine concentration.

The recently developed fluorescent immunoassay (FIA) for measuring serum carbamazepine concentration is compared to the established enzyme-multiplied-immunoassay-technique (EMIT). The Accuracy, precision and simplicity of these methods are comparable. The sensitivity of FIA is approximately eight times greater than the EMIT but the assay time required for FIA is longer. Potential improvements of the FIA technique are discussed.

Effect of neural transplants on seizure frequency and kindling in immature rats following kainic acid.

To study the hypothesis that neural transplantations can alter seizure susceptibility in a chronic animal model of epilepsy 260 immature rats (30- to 32-days-old) were administered a convulsant dosage of kainic acid (KA). Ten days later rats that had severe seizures following KA received either bilateral intracerebroventricular transplants of hippocampal (n = 27), neocortical (n = 29), cerebellar (n = 30), or locus ceruleus (n = 32) tissue, or underwent sham transplantation (n = 66). Spontaneous seizure frequency was assessed for 230 days following which the rats underwent entorhinal kindling. The percentage of rats developing spontaneous recurrent seizures was similar in the 4 transplant groups and the sham-operated controls. Rats receiving hippocampal and locus ceruleus transplants had fewer spontaneous seizures than the sham-operated controls or other transplant groups. However, there were no differences in afterdischarge thresholds or kindling rates in the 5 groups. This study demonstrates that the anticonvulsant effects of neural transplants, using this animal model are mild. Tissue type of the graft appears to be an important variable in the alteration of seizure frequency.

The influence of manganese supplementation on seizure onset and severity, and brain monoamines in the genetically epilepsy prone rat.

Human and experimental animal studies suggest a relationship between low Mn status and seizures. The genetically epilepsy prone rat (GEPR), which has low tissue Mn levels, was studied in the context of Mn supplementation. Manganese was provided at 45 micrograms/g diet (control) or 1000 micrograms/g diet (supplemented) to dams during pregnancy and lactation, then to the offspring after weaning. Offspring were tested for seizure susceptibility as young adults; tissue trace elements, brain monoamines and brain glutamine synthetase activity were measured as endpoint biochemical indices. Supplementation, although developmentally encompassing and highly effective in elevating tissue Mn levels, had no effect on seizure latency or severity. Similarly, brain monoamine concentrations and glutamine synthetase activities were resistant to Mn supplementation. Notably, the GEPR was confirmed to have low whole brain glutamine synthetase activity. These findings suggest that seizure activity in the GEPR does not stem from an increased nutritional/metabolic need for Mn.

Effect of 2-amino-7-phosphonoheptanoic acid (APH) on seizure susceptibility in the prepubescent and mature rat.

There is now considerable evidence that the N-methyl-D-aspartic acid receptor is important in the genesis of seizures. One of the selective antagonist of the NMDA receptor is 2-amino-7-phosphonoheptanoic acid (APH). In this study we evaluated the effects of intracerebroventricular (i.c.v.) administration of APH on seizure susceptibility in both prepubescent and mature rats using the rapid kindling and flurothyl ether seizure models. Both the immature and mature animals receiving APH kindled at a significantly slower rate than control animals receiving phosphate-buffered saline. APH also demonstrated a significant anticonvulsant effect against flurothyl-induced seizures in both the immature and mature animals. This study supports prior work that selective NMDA receptor antagonists such as APH may have promise as potential antiepileptic agents.

Valproate metabolite concentrations in brain increase with chronic administration of sodium valproate.

Rats were treated chronically with sodium valproate for varying periods of time up to eight weeks. A statistically significant negative correlation between plasma concentrations of valproate-derived substances (VDS) and length of treatment was observed while a statistically significant positive correlation was found between brain VDS concentration and length of treatment. Liver VDS concentrations showed a tendency to decrease with time but this trend was not statistically significant. A new procedure was developed to measure the tissue levels of VDS.

Brain levels of amines and amino acids in taste aversion-prone and -resistant rats.

Possible biological contributions to taste aversion (TA) conditionability were explored by comparing whole-brain levels of five neurotransmitter amines and 14 common amino acids within TA-prone (TAP) and TA-resistant (TAR) rats. The selectively bred strains had been developed via 22 generations of bidirectional nonsibling matings based on susceptibility to cyclophosphamide-induced conditioned TAs. The target substances were separated by HPLC and were measured by electrochemical or fluorometric procedures. The TAP brains had higher levels of serotonin (5-HT) and lower levels of norepinephrine (NE) than TAR brains. No strain differences were found with respect to dihydroxyphenylalanine (DOPAC), dopamine (DA), or 5-hydroxyindoleacetic acid (5-HIAA). Among amino acids, TAP rats had lower levels of lysine than TARs: no other differences were detected. Therefore, higher levels of 5-HT and lower levels of NE and lysine were associated with enhanced TA conditionability. The 5-HT and NE results extend prior indications of their central neurotransmitter TA involvements. The functional role of lysine in TA or other brain functions remains obscure.

Lipid peroxidation and antioxidant vitamins prior to, during, and after correction of diabetic ketoacidosis.

Oxidative stress plays an important role in the chronic complications of insulin-dependent diabetes mellitus (IDDM). Hyperketonemia, as well as hyperglycemia, is involved in the generation of oxygen-free radicals. We have studied the degree of oxidative stress in six patients before, during, and after correction of diabetic ketoacidosis (DKA) by determining the plasma ratios of C20 and C18 fatty acids to C16 fatty acids in the cholesteryl esters of the lipoproteins as well as in the plasma concentrations of the antioxidant vitamins A, C, and E. Lipid peroxidation was slightly increased prior to treatment. However, the C20/C16 ratio at 120 h was significantly decreased in comparison to the ratio at pretreatment (P<.025), at 6-8 h (P<.005), and at 24 h (P<.025). The C18/16 ratio at 120 h was also decreased in comparison to the ratio at 6-8 h (P<.025), indicating an increase in lipid peroxidation after correction of DKA. Vitamin A was below normal at pretreatment and was increased at 120 h (P<.05). Vitamin C was normal at pretreatment and decreased to low normal at 24 h (P<.005). Vitamin E was normal at pretreatment and decreased to below normal at 24 and 120 h, although the changes were not statistically significant. These data demonstrate that there is an increase in lipid peroxidation after the correction of DKA and therefore support the position that administering antioxidant vitamins during the treatment of DKA could be beneficial in minimizing oxidative stress and possibly both the acute and chronic complications of IDDM.

Serotonin reuptake is less efficient in taste aversion resistant than in taste aversion-prone rats.

We have previously reported the development of rat lines bred selectively for differences in taste aversion conditionability. Earlier studies demonstrated that the taste aversion resistant (TAR) animals exhibited lower concentrations of brain serotonin and consumed greater amounts of ethanol than their taste aversion prone (TAP) counterparts. In the present study, TAR rats demonstrated significantly less efficient brain serotonin transport compared to TAP rats, but the rat lines demonstrated similar levels of serotonin transporter or V(max) and similar whole brain paroxetine (a specific serotonin reuptake inhibitor) binding (B(max)). These results suggest that the rat lines differ in the mechanisms that transport serotonin into nerve endings, but do not differ in the binding of serotonin to the transporter or in the number of serotonin transport sites. The data support the hypothesis that genetically determined differences in the serotonin system contribute to individual differences in taste aversion conditionability. The findings further suggest that differences in serotonin transport may influence the propensity to self-administer ethanol.

Hyperformaldehydism: a unifying hypothesis for the major biochemical theories of schizophrenia.

A biochemical hypothesis concerning the etiology of schizophrenia is presented. This hypothesis postulates the presence of a genetically determined lesion in the disposition of one-carbon units leading to elevated levels of formaldehyde, i.e hyperformaldehydism. The relationships between this hypothesis and the existing major biochemical hypotheses of schizophrenia regarding dopamine and transmethylation are discussed.