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Biomedical subjects

S Kure

Publications and source records attributed to S Kure.

At least 55 records · Page 3Linked to original sources
PubMed1997

Depletion of cerebral D-serine in non-ketotic hyperglycinemia: possible involvement of glycine cleavage system in control of endogenous D-serine.

Tissue concentrations of D-serine and other chiral and non-chiral amino acids were measured post-mortem in the cerebral cortex of the neonatal or infantile individuals with (three cases) or without (seven cases) non-ketotic hyperglycinemia (NKH) using high performance liquid chromatography with fluorometric detection. In the cortical tissues of the NKH patients lacking activity of glycine cleavage system, there was a marked reduction and elevation of the contents of D-serine and glycine, respectively, compared to non-NKH controls. Systemic administration of an inhibitor of glycine cleavage system (GCS), cysteamine, mimicked the changes in the cortical concentrations of these amino acids in the 8-day-old rats. Augmentation of brain glycine levels by means of intraperitoneal injection of glycine itself resulted in an increase in cortical D-serine contents in the neonatal rats with normal activity of GCS. These findings provide the first evidence that GCS might be implicated in the biosynthesis or content regulation of endogenous D-serine in the mammalian brain.

Amino Acid Oxidoreductases↗
PubMed1997

Nonketotic hyperglycinemia: biochemical, molecular, and neurological aspects.

Nonketotic hyperglycinemia (NKH) is a metabolic disorder with autosomal recessive inheritance, causing severe, frequently lethal, neurological symptoms in the neonatal period. The metabolic lesion of NKH is in the glycine cleavage system (GCS), a complex enzyme system with four enzyme components; P-, T-, H-, and L-protein. The enzymatic analysis revealed that 86% of the patients with NKH are deficient of P-protein activity. The cDNA clones encoding all four components were isolated and their primary structures were determined. Several mutations have been identified in P- and T-protein genes: One missense mutation, S564I, in P-protein gene accounts for 70% of the mutant alleles in Finland where the incidence of NKH is unusually high. The immunochemical and in situ hybridization analyses revealed that the strong GCS expression was observed in rat hippocampus, olfactory bulbus, and cerebellum. The distribution resembled that of N-methyl-D-aspartic acid (NMDA) receptor which has binding site for glycine. It is, therefore, suggested that the neurological disturbance in NKH may be caused by excitoneurotoxicity through the NMDA receptor allosterically activated by high concentration of glycine. Based on the hypothesis the NMDA antagonists such as ketamine and dextromethorphan were administered to the patients. We treated three neonatal case with dextromethorphan and it ameliorated their findings on electroencephalogram and behavior in two out of three patients. Thus the GCS is suggested to play a role in regulation of glycine level around the NMDA receptor.

Amino Acid Metabolism, Inborn Errors↗
PubMed1997

Molecular analysis of dihydropteridine reductase deficiency: identification of two novel mutations in Japanese patients.

Mutations in the dihydropteridine reductase (DHPR) gene result in hyperphenylalaninaemia and deficiency of various neurotransmitters in the central nervous system, causing severe neurological symptoms. We studied two Japanese patients with DHPR deficiency and identified a missense and a splicing error mutation, respectively. A homozygous missense mutation (tryptophan36-to-arginine) was detected in patient 1. The mutation abolished DHPR activity according to in vitro expression studies. The DHPR mRNA in patient 2 was markedly decreased. Reverse transcription-polymerase chain reaction of the mRNA generated a cDNA fragment with a 152-bp insertion. The inserted sequence contained a termination codon, which was likely to affect the stability of the mRNA. Analysis of genomic DNA showed that the insertion was derived from putative intron 3 of the DHPR gene, and an intronic A-to-G substitution was present adjacent to the 3'-end of the inserted sequence. The nucleotide change generated a sequence similar to an RNA splice donor site and probably activated an upstream cryptic acceptor site, thus producing an abnormal extra exon.

Amino Acid Metabolism, Inborn Errors↗
PubMed1996

Association of a mutation in thiazide-sensitive Na-Cl cotransporter with familial Gitelman's syndrome.

Gitelman's syndrome is a variant of Bartter's syndrome, characterized by hypokalemia, hypomagnesemia, hypocalciuria, and hypovolemia. We have observed familial cases of Gitelman's syndrome, and a possible mutation in thiazide-sensitive Na-Cl cotransporter was investigated in this kindred. The proband was a 47-yr-old Japanese female, and her mother was also affected. Her parents and maternal grandparents are consanguineous. By using PCR-amplification and direct sequencing, we identified a novel non-conservative missense mutation at 623 amino acid position, which substitutes proline for leucine (L623P), and also creates an Nci I restriction site in the exon 15. The mutation was not detected in normal healthy subjects (n = 102). Nci I digestion of PCR-amplified exon 15 DNA fragments from individuals in the family indicated the autosomal recessive inheritance of the disorder. In conclusion, the L623P mutation in the thiazide-sensitive Na-Cl cotransporter gene is suggested to impair the transporter activity, and to underlie this familial Gitelman's syndrome; Gitelman's syndrome observed in this kindred has been inherited in an autosomal recessive fashion.

Bartter Syndrome↗
PubMed1996

[Genetic diagnosis of inborn error of metabolism by microsatellite marker analysis].

We discussed here the usefulness of the microsatellite marker analysis in the prenatal diagnosis of inborn errors of metabolism. Since most inborn errors of metabolism are not common disorders, it is hard to find a common mutation highly useful for the DNA diagnosis. It would be, therefore, more advantageous to diagnose a fetus at risk by analyzing the affected family with multiple highly-polymorphic markers such as the CA repeats. To establish the diagnosis system by the polymorphic markers, it would be a great help to use a human linkage map which contains an increasing number of CA repeat markers.

Female↗
PubMed1995

Apoptotic cell death of a temperature-sensitive central neuronal cell line.

A neuron-like cell line HS-2, derived from a primary fetal rat (E17) hippocampal cell culture using the temperature-sensitive SV 40 large T antigen, exhibits flat shape and grows well in culture medium with 5% fetal calf serum (FCS) at the permissive temperature (PT, 33.5 degrees C). At the non-permissive temperature (NPT, 38.5 degree C), many, but not all cells, have a neuronal shape with processes. The addition of dibutyryl-cAMP promotes the morphological changes in the cells to a neuron-like shape with long neurite-like processes and the cells exhibit neuron-specific enolase- and glutamic acid decarboxylase-immunoreactivity. Apoptotic cell death also occurs in these cultures at the NPT. DNA fragmentation and chromatin condensation that are characteristic of apoptosis occur within 8 h of being placed at the NPT. By 48 h after being placed at the NPT, the number of surviving cells decreases by 40% in the presence of 5% FCS. This cell line should be useful for investigating the mechanisms of 'programmed cell death' of neurons, which appears to occur during brain development and possibly in CNS degenerative diseases.

Animals↗
PubMed1993

Endonuclease activation following focal ischemic injury in the rat brain.

The structural changes which occur in chromatin DNA after ischemic brain injury are poorly understood. This study examined the appearance of double-strand DNA breaks and the temporal profile of DNA degradation following focal ischemic injury in rat brain. Focal cerebral ischemia was produced by tandem occlusion of the common carotid and proximal middle cerebral arteries. The effects of decapitation ischemia were also studied by DNA analysis. DNA was extracted by standard methods from the ischemic brain tissues and electrophoresed on a 1.5% agarose gel. With decapitation ischemia, random DNA cleavage was observed as a dense "smear" on the gel electrophoresis beginning 6 h after the ischemic insult, and increasing in amount thereafter. Focal ischemia provided DNA fragmentation, which is specific DNA cleavage at the internucleosomal linker regions, particularly in the caudoputamen. Coexisting random degradation and specific fragmentation of DNA was observed in the cortex following focal ischemia. To determine whether an endonuclease responsible for DNA fragmentation was present, nuclear proteins were extracted from normal brain nuclei and the endonuclease activity was determined using plasmid DNA and a nuclear incubation system. This demonstrated that brain nuclear proteins have Ca(2+)-dependent endonuclease activity which is related to DNA fragmentation. Ischemic injury causes both random and specific DNA cleavage in the brain, which is probably mediated by Ca(2+)-dependent endonuclease.

Animals↗
PubMed1993

Non-ketotic hyperglycinaemia: molecular lesion, diagnosis and pathophysiology.

Non-ketotic hyperglycinaemia (NKH) is a well-recognized metabolic cause of life-threatening illness in the neonate. The fundamental defect is in the glycine cleavage system, which consists of four protein components. Our study revealed that the majority of NKH patients had a specific defect in P-protein (glycine decarboxylase). The primary lesion of NKH at gene level was investigated, using cDNA encoding human glycine decarboxylase. A three-base deletion resulting in deletion of Phe756 was found in a Japanese patient with NKH. The majority of NKH patients in Finland, where there is a high incidence of NKH, were found to be due to a common mutation, a point mutation resulting in the amino acid substitution of Ile564 for Ser564. Prenatal diagnosis is feasible by determining the activity of the glycine cleavage system and is also possible by DNA analysis. Recent findings suggest that a high concentration of glycine in the brain may contribute to the pathophysiology of NKH by overactivating N-methyl-D-aspartate receptors allosterically, which may result in intracellular calcium accumulation, DNA fragmentation and neuronal death. These provide the possibility that early treatment with N-methyl-D-aspartate receptor antagonist may prevent brain damage in NKH.

Amino Acid Metabolism, Inborn Errors↗
PubMed1993

Atypical nonketotic hyperglycinemia confirmed by assay of the glycine cleavage system in lymphoblasts.

A 13-year-old girl with early-onset, mild, slowly progressive mental retardation caused by nonketotic hyperglycinemia is described. The plasma and cerebrospinal fluid glycine concentrations were elevated, but the cerebrospinal fluid/plasma glycine ratio was only mildly elevated. The diagnosis was confirmed by demonstration of a defect in the activity of the glycine cleavage system in cultured lymphoblasts.

Adolescent↗
PubMed1992

DNA fragmentation in focal cortical freeze injury of rats.

This study examined the appearance of double-strand DNA breaks in rat brain after a focal cortical freeze injury in vivo. DNA fragments of oligonucleosome size appeared 3 h after the injury, and increased in a time-dependent manner. At 24 h, the amount of DNA fragmentation reached a maximum and then declined. When nuclei from freeze-injured brain tissue were incubated with Ca2+ in vitro, increased endonuclease activity, which can cause DNA fragmentation, was found. These findings indicate that the activation of a Ca(2+)-dependent endonuclease may be involved in the evolution of freeze-traumatized brain tissue.

Animals↗
PubMed1992

Enzymatic diagnosis of nonketotic hyperglycinemia with lymphoblasts.

We developed a new enzymatic assay for the glycine cleavage system that used Epstein-Barr virus-transformed lymphoblasts instead of liver biopsy specimens. Patients with nonketotic hyperglycinemia from a deficiency of P-protein could be clearly distinguished from control subjects by activities in their lymphoblasts, suggesting the clinical usefulness of this method.

Adolescent↗
PubMed1992

Identification of a common mutation in Finnish patients with nonketotic hyperglycinemia.

Nonketotic hyperglycinemia (NKH) is an autosomal recessive metabolic disorder caused by the defects in the glycine cleavage system (GCS; EC 2.1.2.10), a multienzyme system that consists of four individual components. NKH is a rare disorder in many countries, but with a very high incidence in northern Finland. To understand the genetic background of this high incidence, we examined the GCS in a typical case of NKH at the molecular level. The activity of P protein, a component of the GCS, was not detected in the lymphoblasts of the patient, while P protein mRNA of a normal size and level was present in the cells. Structural analysis of P protein mRNA from the patient revealed a single nucleotide substitution from G to T in the protein coding region, which resulted in an amino acid alteration from Ser564 to Ile564. No P protein activity was detected when the mutant P protein with this amino acid substitution was expressed in COS 7 cells. The patient was homozygous for this mutation. Furthermore, this mutation was present in 70% (14 of 20) of P protein gene alleles in Finnish patients with NKH, whereas it was not found in 20 alleles of non-Finnish patients. The results suggest that this mutation is responsible for the high incidence of NKH in Finland.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

[Prenatal diagnosis of inborn error of amino acid metabolism].

Prenatal diagnosis of inborn errors of amino acid metabolism was discussed from the viewpoints of its purpose, ethical problems, analysis methods, and sampling methods of the fetal tissues. In addition to the general discussion, our results of the prenatal diagnosis of 20 cases with nonketotic hyperglycinemia (NKH) were also reported. Nineteen cases were diagnosed by the enzymatic method, while one Finnish case was successfully diagnosed by DNA analysis, which is based on our observation that a missense mutation we identified accounts for 70% of the mutant alleles in Finland. The DNA analysis would be a great help for the prenatal diagnosis in Finland where the incidence of NKH is unusually high (1: 12,000 births).

Amino Acid Metabolism, Inborn Errors↗
PubMed1991

Glutamate triggers internucleosomal DNA cleavage in neuronal cells.

Glutamate neurotoxicity is responsible for neuronal loss associated with numerous obstinate disorders. In this report, the mechanism of glutamate neurotoxicity was investigated on a viewpoint of DNA degradation. We found that chromosomal DNA of cultured neurons was degraded into nucleosomal-sized DNA fragments by the addition of glutamate, prior to the glutamate-induced neuronal death. Both the neuronal death and DNA fragmentation were prevented by the inhibitors of endonucleases and mRNA synthesis. Furthermore, an injection of glutamate into the rat hippocampi resulted in DNA fragmentation with the similar time course observed in neuronal death in vitro. These results suggest that the glutamate neurotoxicity involves an active suicide process which leads to neuronal death through internucleosomal DNA cleavage.

Animals↗