Ammonia and methionine sulfoximine intoxication

Intoxication with ammonium acetate abolished the suppression of action potential generation by cortical postsynaptic inhibition, i.e. produced ‘disinhibition’, due to the inactivation of neuronal Cl⁻ extrusion. With the occurence of disinhibition cerebral ammonia increased to 445% of normal; glutamine increased to 170%.Methionine sulfoximine (MSO), an inhibitor of glutamine synthetase, produced disinhibition about 3 h after administration; at this time cerebral ammonia was increased to 290% of normal, glutamine was unchanged. Intoxication with MSO for less than 3 h significantly decreased the amount of ammonium acetate needed to produce disinhibition at cerebral ammonia concentrations of 340–430% of normal.MSO produces an endogenous ammonia intoxication which: (i) decreases the amount of exogenous ammonia required to affect cortical postsynaptic inhibitions; and (ii) eventually becomes sufficiently severe to disturb cortical inhibitory neuronal interactions by itself.     

Defects in citric acid cycle and the electron transport chain in progressive poliodystrophy

Abstract– We will present 8 children with progressive infantile or juvenile poliodystrophy (Alpers' disease), associated with a defect in pyruvate metabolism. Laboratory studies showed elevated levels of lactate in CSF and, in 4 children, elevated levels in serum. Histopathologic studies revealed lipid storage in liver and/or muscle tissue, sometimes myopathy with abnormal mitochondria and slight axonal degeneration in the peripheral nerve. Autopsy showed the characteristics of progressive poliodystrophy with degeneration and loss of neurons. Electron microscopy of cerebral cortex showed no mitochondrial abnormalities in neurons or astroglia. Biochemical studies in muscle and/or liver and/or cerebral tissue showed different deficiencies in pyruvate metabolism: in the pyruvate dehydrogenase complex, in the second part of the citric acid cycle (after the oxoglutarate dehydrogenase complex), in the NADH oxidation, in cytochrome aa ₃ and in pyruvate carboxylase.     

Possible role of increased brain methylation in methionine sulfoximine epileptogenesis: effects of administration of adenosine and homocysteine thiolactone

An intraventricular pulse of [14COOH]L-methionine to mice pretreated with the convulsant L-methionine-dl-sulfoximine (MSO) resulted in significantly higher than control specific radioactivity values of cerebral [14COOH]L-methionine (Met), [14COOH]S-adenosyl-L-methionine (AdoMet) and [14COOH]S-adenosyl-L-homocysteine (AdoHcy). MSO administration (3 hr) also decreased brain steady-state levels of Met, AdoMet, and AdoHcy. Following an intraventricular pulse of [3H-methyl]L-methionine, the levels of [3H-methyl]phosphatidylmonomethylethanolamine and of membrane associated and soluble [3H-methyl]carboxylmethylated proteins were increased over corresponding saline-treated controls. The activity of cerebral histamine N-methyltransferase was also increased after MSO treatment. The administration of a combination of adenosine and homocysteine thiolactone to MSO-pretreated animals counteracted the MSO-induced decreases in brain Met, AdoMet, and AdoHcy as well as the increase in histamine N-methyltransferase activity. In addition, administration of adenosine together with homocysteine thiolactone decreased the incidence of, and increased the latency to MSO seizures, with the most effective anticonvulsant action occurring when cerebral AdoHcy levels were at their highest.     

Intranigral methionine sulfoximine induces turning behaviour in the rat

Unilateral infusion of methionine sulfoximine (MSO) into the substantia nigra of the rat induced contralateral rotations appearing progressively after a delay of about 100 min. The rotations were maximally antagonized by picrotoxin and bicuculline intraperitoneally injected at approximately 50-80 min after the intranigral infusion of MSO. Contraversive turning behaviour was absent after intranigral infusion of MSO in unilaterally 6-hydroxydopamine-lesioned rats.     

Effect of glutamine synthetase inhibition on brain and interorgan ammonia metabolism in bile duct ligated rats

Ammonia has a key role in the development of hepatic encephalopathy (HE). In the brain, glutamine synthetase (GS) rapidly converts blood-borne ammonia into glutamine which in high concentrations may cause mitochondrial dysfunction and osmolytic brain edema. In astrocyte-neuron cocultures and brains of healthy rats, inhibition of GS by methionine sulfoximine (MSO) reduced glutamine synthesis and increased alanine synthesis. Here, we investigate effects of MSO on brain and interorgan ammonia metabolism in sham and bile duct ligated (BDL) rats. Concentrations of glutamine, glutamate, alanine, and aspartate and incorporation of ¹⁵NH₄⁺ into these amino acids in brain, liver, muscle, kidney, and plasma were similar in sham and BDL rats treated with saline. Methionine sulfoximine reduced glutamine concentrations in liver, kidney, and plasma but not in brain and muscle; MSO reduced incorporation of ¹⁵NH₄⁺ into glutamine in all tissues. It did not affect alanine concentrations in any of the tissues but plasma alanine concentration increased; incorporation of ¹⁵NH₄⁺ into alanine was increased in brain in sham and BDL rats and in kidney in sham rats. It inhibited GS in all tissues examined but only in brain was an increased incorporation of ¹⁵N-ammonia into alanine observed. Liver and kidney were important for metabolizing blood-borne ammonia.     

Integrated analysis of the association between methionine cycle and risk of moyamoya disease

Objective

The role of methionine (Met) cycle in the pathogenesis and progression of cardiovascular and cerebrovascular diseases has been established, but its association with moyamoya disease (MMD) has rarely been studied. This study aimed to analyze the levels of Met cycle-related metabolites and constructed a risk model to explore its association with the risk of MMD.

Methods

In this prospective study, a total of 302 adult MMD patients and 88 age-matched healthy individuals were consecutively recruited. The serum levels of Met cycle-related metabolites were quantified by liquid chromatography-mass spectrometry (LC–MS). Participants were randomly divided into training set and testing set at a ratio of 1:1. The training set was used to construct the risk score model by LASSO regression. The association between Met cycle-related risk score and the risk of MMD was analyzed using logistic regression and assessed by ROC curves. The testing set was used for validation.

Results

The levels of methionine sulfoxide and homocysteine were significantly increased, while the levels of betaine and choline were significantly decreased in MMD and its subtypes compared to healthy controls (p < 0.05 for all). The training set was used to construct the risk model and the risk score of each participant has been calculated. After adjusting for potential confounders, the risk score was independently associated with the risk of MMD and its subtypes (p < 0.05 for all). We then divided the participants into low-risk and high-risk groups, the high-risk score was significantly associated with the risk of MMD and its subtypes (p < 0.05 for all). The risk scores were further assessed as tertiles, the highest tertile was significantly associated with a higher risk of MMD and its subtypes compared to the lowest (p < 0.05 for all). The results were validated in the testing set.

Conclusion

This study has constructed and validated a risk model based on Met cycle-related metabolites, which was independently associated with the risk of MMD and its subtypes. The findings provided a new perspective on the risk evaluation and prevention of MMD.     

The development of recurrent seizures after continuous intrahippocampal infusion of methionine sulfoximine in rats: A video-intracranial electroencephalographic study

Glutamine synthetase is deficient in astrocytes in the epileptogenic hippocampus in human mesial temporal lobe epilepsy (MTLE). To explore the role of this deficiency in the pathophysiology of MTLE, rats were continuously infused with the glutamine synthetase inhibitor methionine sulfoximine (MSO, 0.625 μg/h) or 0.9% NaCl (saline control) unilaterally into the hippocampus. The seizures caused by MSO were assessed by video-intracranial electroencephalogram (EEG) monitoring. All (28 of 28) of the MSO-treated animals and none (0 of 12) of the saline-treated animals developed recurrent seizures. Most recurrent seizures appeared in clusters of 2 days' duration (median; range, 1 to 12 days). The first cluster was characterized by frequent, predominantly stage I seizures, which presented after the first 9.5 h of infusion (median; range, 5.5 to 31.7 h). Subsequent clusters of less-frequent, mainly partial seizures occurred after a clinically silent interval of 7.1 days (median; range, 1.8 to 16.2 days). The ictal intracranial EEGs shared several characteristics with recordings of partial seizures in humans, such as a distinct evolution of the amplitude and frequency of the EEG signal. The neuropathology caused by MSO had similarities to hippocampal sclerosis in 23.1% of cases, whereas 26.9% of the animals had minimal neuronal loss in the hippocampus. Moderate to severe diffuse neuronal loss was observed in 50% of the animals. In conclusion, the model of intrahippocampal MSO infusion replicates key features of human MTLE and may represent a useful tool for further studies of the cellular, molecular and electrophysiological mechanisms of this disorder.     

Effect of orotic acid on the metabolism of cerebral cortical astrocytes during hypoxia and reoxygenation: An NMR spectroscopy study

Astrocytes were incubated under normoxic or hypoxic conditions in Dulbecco's minimum essential medium containing [12-¹³C]acetate, unlabeled glucose and in some cases orotic acid, an intermediate in pyrimidine biosynthesis. After 12 hr the medium was replaced by fresh medium without drug and incubation was continued for 17 hr in a normal oxygen atmosphere (reoxygenation). Thereafter, medium was removed, cell extracts were prepared, and metabolism in the treatment group was compared to the untreated hypoxia group and to control. ¹³C and H NMR spectra revealed that ¹³C enrichment in citrate and glutamine C-4 in the initial medium were increased in the presence of orotic acid, compared to the untreated hypoxia group but lower than control. The drug increased acetate utilization during hypoxia to normoxic levels. Thus it appears that the treatment group had a more active mitochondrial metabolism, which was also reflected in higher intracellular uridine diphosphoryl sugars and ADP concentrations. Glutamine labeling was increased in the cell extracts in the presence of orotic acid. Thus it appears that, in the presence of the pyrimidine nucleotide precursor, astrocytes are capable of normal metabolism during hypoxia which might have implications for neuronal survival during low oxygen insults, since neurons are dependent on astrocyte produced precursors for their neurotransmitter synthesis.     

Effects of thioctic acid on the glutathione redox cycle after cerebral ischemia-reperfusion in rats

We investigated the effects of thioctic acid on the functioning of the glutathione redox cycle and the activities of several NADPH-generating enzymes in the rat brain after acute ischemia-reperfusion. Administration of thioctic acid to the animals with postischemic reperfusion resulted in a decrease in the activity of glutathione peroxidase and glutathione reductase, which was increased after the pathology. The content of reduced glutathione was also close to the control value. Moreover, under ischemia-reperfusion conditions, the injection of thioctic acid decreased the activities of NADP-dependent isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase; this decrease was possibly due to a lowering of the NADPH consumption by glutathione-dependent mechanisms of antiradical defense. Thus, our data show that thioctic acid can regulate the progress of oxidative stress and state of glutathione antioxidant system.     

Oxygen toxicity protecting enzymes in the human brain

Summary Regional distribution of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities were studied in 22 anatomic sites of 5 human brains. No significant regional differences were observed in cytosolic activities of any enzyme studied, nor in particulate activities of superoxide dismutase, catalase and glutathione reductase, whereas particulate glutathione peroxidase activities were distributed unevenly, the highest activities observed in the basal nucleus and amygdala. There were significant interindividual differences in the activities of each enzyme. This was shown to result partly from the decrease of cytosolic superoxide dismutase and catalase activities with age, concurrently with age-related decrease of particulate glutathione peroxidase and glutathione reductase activities.     

Activity of Krebs cycle enzymes in mdx mice

Introduction: Duchenne muscular dystrophy (DMD) is a degenerative disease of skeletal, respiratory, and cardiac muscles caused by defects in the dystrophin gene. More recently, brain involvement has been verified. Mitochondrial dysfunction and oxidative stress may underlie the pathophysiology of DMD. In this study we evaluate Krebs cycle enzymes activity in the cerebral cortex, diaphragm, and quadriceps muscles of mdx mice. Methods: Cortex, diaphragm, and quadriceps tissues from male dystrophic mdx and control mice were used. Results: We observed increased malate dehydrogenase activity in the cortex; increased malate dehydrogenase and succinate dehydrogenase activities in the diaphragm; and increased citrate synthase, isocitrate dehydrogenase, and malate dehydrogenase activities in the quadriceps of mdx mice. Conclusion: This study showed increased activity of Krebs cycle enzymes in cortex, quadriceps, and diaphragm in mdx mice. Muscle Nerve 53 : 91–95, 2016     

Valproic acid suppresses G1 phase-dependent sialylation of a 65 kDa glycoprotein in the C6glioma cell cycle

The influence of valproate on invitro glycosylation events in C6 glioma has been investigated, as this major human teratogen restricts proliferation in the mid-G1 phase of the cycle and alters the prevalence and/or glycosylation state of cell surface glycoproteins with the potential to mediate cell–cell and cell–matrix interactions critical to development. C6 glioma cultured continuously in the presence of 1 mM valproate exhibited a significant depression of exponential growth but attained confluency one day later, when the majority of cells entered the G1 phase of the cycle. Glycoprotein sialyltransferase, which exhibited a four-fold increase during exponential growth and a small decrease at confluency, was markedly attenuated in valproate-exposed cells in a manner which was indirect. This was associated with an inhibition of transient α2,3 sialylation of a 65 kDa glycoprotein expressed maximally at 4 hr into the G1 phase of the cell cycle. This effect was cell-cycle phase-specific, as exposure of synchronized cells to valproate inhibited transient sialylation at 4 and 5 hr into the G1 phase. Inhibition of the 65 kDa glycoprotein sialylation by valproate is suggested to arise from impaired signal transduction preceding the eventual arrest by the drug at a 5–6 hr G1 phase restriction point.     

In vitro effect of n-Hexane and its metabolites on selected enzymes in glycolysis, pentose phosphate pathway and citric acid cycle

The effect ofn-hexane, 2-hexanol, 5-hydroxy-2-hexanone, 2,5-hexanediol, methyln-butyl ketone (MnBK) and 2,5-hexanedione (2,5-HD) has been studied in vitro on crystalline glyceraldehyde-3-phosphate dehydrogenase (GAPDH),dl-glyceraldehyde-3-phosphate: NAD oxidoreductase (phosphorylating) EC. 1.2.1.12 and phosphofrucktokinase (PFK) ATP:d-fructose-6-phosphate-1-phosphotransferase; EC. 2.7.1.11 and lactic dehydrogenase (LDH)l-lactate: NAD⁺ oxidoreductase, EC. 1.1.1.27.MnBK and 2,5-HD both inhibited GAPDH and PFK activities selectively.n-Hexane and 2-hexanol had no effect on GAPDH and PFK activities; 5-hydroxy-2-hexanone and 2,5-hexanediol exhibited a slight inhibitory effect on these enzymes. Neither metabolites ofn-hexane have any effect on LDH activity. 2,5-Hexanedione did not inhibit transketolase (d-sedoheptulose-7-phosphate:d-glyceraldehyde-3-phosphate glycolaldehyde transferase, EC. 2.2.1.1.) and succinate dehydrogenase (succinate: 2,6-dichlorophenol-indophenol oxidoreductase, EC. 1.3.99.1) activities. The levels of ATP were reduced in 2,5-HD-treated cat sciatic nerves and returned to normal levels by exposing the nerve to sodium pyruvate.     

Mitochondrial enzymes in schizophrenia

The responses of brain metabolism and blood flow to stimulation are diminished in the dorsolateral prefrontal cortexes (DLPFCs) of schizophrenic patients. Reductions in mitochondrial enzymes underlie diminished metabolism in several neurodegenerative diseases. Thus, we tested whether reductions in selected mitochondrial enzymes could underlie the changes in schizophrenia. The activities of the pyruvate dehydrogenase complex (PDHC), aconitase, isocitrate dehydrogenase (ICDH), and the α-ketoglutarate dehydrogenase complex (KGDHC) were determined on DLPFCs from patients with schizophrenia (n=26) and normal nonpsychiatric disease controls (n=13). The enzyme activities (mU/mg protein; mean ± SEM) were similar (values for controls and schizophrenic patients, respectively) for PDHC (11.36 ± 1.5, 10.33 ± 0.8), aconitase (1.06 ± 0.1, 1.35 ± 0.2), ICDH (31.70 ± 2.7, 32.00 ± 2.6), and KGDHC (2.62 ± 0.4, 3.09 ± 0.3). Separate analyses of the patients matched for age or postmortem interval gave similar conclusions. Cognitive dementia rating scores correlated poorly with activities of PDHC, aconitase, ICDH, and KGDHC. In one schizophrenic patient, activity of aconitase was undetectable, and in two others KGDHC activity was very low. Both had low activities of ICDH. A reduced activity of these enzymes in a subgroup is consistent with other data, suggesting that some patients with schizophrenia have abnormalities in brain mitochondria. However, in schizophrenia, unlike a number of neurodegenerative diseases, reductions in the activities of the key mitochondrial enzymes KGDHC and PDHC are not frequent. These authors contributed equally in completing the current study.     

缺血缺氧对体外培养星形胶质细胞细胞周期和周期相关蛋白的影响

目的 观察缺血缺氧损伤对星形胶质细胞细胞周期及细胞周期相关蛋白的影响。方法 用流式细胞仪及Brdu掺入法检测缺血缺氧后不同时间点星形胶质细胞细胞周期变化和细胞的增殖活力；用荧光免疫细胞化学技术测定增殖细胞核抗原(PCNA)及细胞周期蛋白cyclin D1的表达水平。结果 体外缺血缺氧损伤后S期星形胶质细胞较正常组明显增加，6h达高峰，Brdu掺入法显示损伤后6h星形胶质细胞的增殖活力最高，而随后S期细胞数目及细胞增殖活力都呈下降趋势。PCNA阳性反应损伤后表达增加，6h表达最高，而cyclin D1的表达在损伤后逐渐增加，在24h时达高峰。结论 缺血缺氧损伤激活星形胶质细胞，使其进入新的细胞周期，出现细胞的增殖反应；PCNA及cyclin D1参与了损伤后星形胶质细胞的修复和增殖；细胞周期事件与星形胶质细胞的增殖活化密切相关。     

Catecholamine synthesizing enzymes in the hypothalamus during the estrous cycle

The activities of tyrosine hydroxylase and dopamine-beta-hydroxylase were measured in the medial basal hypothalamus and remaining hyothalamic tissue of female rats at various times during diestrus 2, proestrus and estrus. Tyrosine hydroxylase activity in the medial basal hypothalamus was significantly lower at 12.00 h compared with other times on proestrus. This decrease preceded the elevation of serum prolactin and LH during the afternoon of proestrus. Tyrosine hydroxylase activity did not change significantly during diestrus 2 or estrus nor was it altered at any time in the remainder of the hypothalamus. Dopamine-beta-hydroxylase activity in the basal medial hypothalamus was significantly elevated at 12.00 h on proestrus and at 14.00 h on diestrus. The results provide further evidence for a decrease in dopaminergic neuron activity in the medial basal hypothalamus which may precipitate the series of events leading to the LH surge during proestrus. The increase in dopamine-beta-hydroxylase activity suggests that an increase in noradrenergic neuron activity may also be involved in triggering the release of LH.     

细胞周期蛋白在局灶性脑缺血中作用机制研究的新进展

局灶性脑缺血对脑神经元损伤的机制是多种因素参与的过程，其中细胞周期相关蛋白有重要作用。研究发现在局灶性脑缺血模型中，许多细胞周期相关蛋白表达增加，且多分布在半暗带。多数学者倾向认为细胞周期相关蛋白参与细胞凋亡过程，并在此过程中起到重要的作用。例如Timsit等认为脑缺血后半暗带神经元内Cyclin D1和CDK4的表达是评估缺血神经元是否再次进入细胞周期的关键标志。本文就目前细胞周期相关蛋白在局灶性脑缺血损伤机制中的研究进展进行综述。     

Influence of vitamin B12 on brain methionine adenosyltransferase activity in senile dementia of the Alzheimer's type

Summary The influence of vitamin B₁₂ on the activity of methionine adenosyltransferase (MAT) in postmortem brains of patients with senile dementia of the Alzheimer's type (SDAT) was investigated. In samples of cortex gyrus frontalis from SDAT patients with normal and low levels of serum B₁₂, MAT V_max was significantly increased by 25% and 19%, respectively. MAT V_max from a SDAT group chronically treated with B₁₂ was similar to controls. In contrast to cortex gyrus frontalis, no significant alterations were seen in MAT activity in nucleus caudatus. This study provides evidence that SDAT is associated with significant alterations in transmethylation mechanisms in specific regions of the brain. The relationship between blood levels of B₁₂ and the actual status of this vitamin in the brain influencing the rates of synthesis of both methionine and SAM may, however, be far more complex and cannot be directly clarified on the basis of the present human brain results.     

Necrotizing effects of kainic acid on neurons in the pigeon brain: Histological observations

The neurotoxin kainic acid (KA) has been shown to destroy neurons in the pigeon paleostriatal complex (PC), the avian analogue of the caudato-putamen and globus pallidus. In this earlier study the movement disorders in pigeons were strikingly similar to those reported by others in rats following intracerebral injection of KA into the corpus striatum. The toxic influences of KA on other parts of the pigeon brain have not been described. Therefore, KA was injected into areas of the telencephalon, diencephalon, mesencephalon and cerebellum. Areas sensitive to KA showed a marked cell loss and the neuropil exhibited spaces that contained fragments of necrotic neurons. The injection sites were invaded by glia and granulocytes. Kainic acid had a local necrotizing effect; for example, it destroyed neurons in the PC, nucleus rotundus, nucleus spiriformis lateralis, nucleus ruber and neurons of the cerebellar cortex. An apparent long-distance effect of KA was also observed, since intracerebral injections of KA into the PC was followed by cell loss in the ipsilateral nucleus of the ansa lenticularis. Kainic acid has proved to be a potent neurotoxin with a pronounced necrotizing effect upon neurons of the pigeon brain.     

Variations in the 5-hydroxyindoleacetic acid concentration in the cerebrospinal fluid during the sleep-wake cycle in man

A variation in the ventricular fluid 5-HIA A concentration has been observed during the phases of the sleep-wake cycle in man. This variation affects the NREM phase, during which 5-HIAA increases markedly, rather than the waking state and the REM phase. The results are discussed in relation to the possible relevance of serotonin to the sleep mechanism.

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Sommario Durante le fasi del ciclo sonnoveglia nell'uomo è stata osservata una modificazione della concentrazione dell'acido 5-HIAA nel liquido ventricolare. Tale modificazione interessa prevalentemente la fase NREM del sonno, durante la quale il 5-HIAA aumenta in misura rilevante, rispetto alla condizione di sveglia e di sonno REM. I risultati vengono discussi in relazione alla possibile implicazione della serotonina nel determinismo del sonno.