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Biomedical subjects

K Metoki

Publications and source records attributed to K Metoki.

12 recordsLinked to original sources
PubMed1987

Partial ornithine transcarbamylase deficiency in females: diagnosis by an immunohistochemical method.

Females heterozygous for the X-linked urea cycle disorder, ornithine transcarbamylase (OTC) deficiency have a significant risk of developing hyperammonaemia. Diagnosis of this genetic defect in a proband is the essential starting point for family studies. By an immunohistochemical analysis of the liver specimens fixed in 10% formalin, we confirmed heterozygous status for OTC deficiency in two female patients, a 15-year-old girl and a 2-year-old girl, who died of hyperammonaemia. Since most affected males lack cross reactive materials (CRM), an immunochemical analysis should be useful for the diagnosis of most heterozygous females.

Adolescent↗
PubMed1986

Studies on a case of HHH-syndrome (hyperammonemia, hyperornithinemia, homocitrullinuria).

A patient with the hyperornithinemia, hyperammonemia, homocitrullinuria syndrome is described. This patient represents the 12th documented case of this rare, presumably autosomal recessive condition. Increased levels of ammonia, ornithine and homocitrulline were demonstrated in blood and cerebrospinal fluid. The blood ammonia concentration could be lowered by supplementation of the diet with low doses of arginine. High doses of arginine precipitated seizures, although plasma levels of arginine and ornithine were not altered. The uptake of ornithine by the particulate fraction of the patient's fibroblasts was lower than that of controls, but still measurable. It is suggested that HHH patients have a partial impairment of the uptake of ornithine by mitochondria.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

Ultrastructural changes in fibroblast mitochondria of a patient with HHH-syndrome.

Electron micrographs of fibroblasts of an HHH-syndrome patient showed abnormal structures, similar, but not identical, to those observed in the liver of such patients. It is suggested that incorporation of a mutated protein into the inner mitochondrial membrane gives rise to a rearrangement of that membrane, resulting in unusual structures.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

The pH of mitochondria of fibroblasts from a hyperornithinaemia, hyperammonaemia, homocitrullinuria-syndrome patient.

The intracellular pH of control fibroblasts and of fibroblasts of a HHH -syndrome patient have been determined. Values of 6.94 +/- 0.15 and 7.05 +/- 0.14 for control and patient fibroblasts, respectively, were found. By means of analyses of malate in the cytosolic and particulate fractions of the fibroblasts the differences in pH between these two cellular compartments were estimated to be 1.34 +/- 0.12 and 1.38 +/- 0.18 for control and patient, respectively. Neither difference was statistically significant. The decrease in the rate of ornithine uptake by mitochondria of the patient's fibroblast is therefore not due to an increased intramitochondrial pH.

Acid-Base Equilibrium↗
PubMed1984

A possible rate limiting factor in urea synthesis by isolated hepatocytes: the transport of ornithine into hepatocytes and mitochondria.

The uptake of ornithine by isolated hepatocytes and by the particulate fraction of these cells was measured under various conditions of urea synthesis. Under conditions of maximum urea synthesis, i.e. in the presence of glucose, ornithine, ammonium chloride and oleate, the cytosolic concentration and the mitochondrial concentration of ornithine was extremely low, while citrulline accumulated in the cytosol. The data indicate that the rate of citrulline synthesis is limited by the availability of mitochondrial ornithine.

Animals↗
PubMed1984

The uptake of ornithine and lysine by isolated hepatocytes and fibroblasts.

The uptake of ornithine and lysine by isolated hepatocytes and cultured human skin fibroblasts were studied. Both types of cells can accumulate these amino acids via a saturable and a non-saturable process, the latter being active at high substrate concentration. The apparent Km for ornithine and lysine for the saturable process in hepatocytes were 0.26 and 0.94 mM respectively, those values for fibroblasts were found to be 0.43 and 0.57 mM respectively. Fractionation of the cells by the digitonin technique into a cytosolic compartment and a particulate compartment, showed that a rapid equilibration occurs between the external medium and the cytosolic compartment of hepatocytes and fibroblasts.

Animals↗
PubMed1984

Further evidence for a separate enzymic entity for the synthesis of homocitrulline, distinct from the regular ornithine transcarbamylase.

Differential digitonin extraction of rat liver mitochondria and of mitochondria of livers of affected and unaffected male sparse fur mice released a lysine transcarbamylase activity from the mitochondria at a digitonin to protein ratio in between that for myokinase and glutamate dehydrogenase, but at a slightly lower ratio than the ornithine transcarbamylase activity. Homocitrulline formation by isolated rat liver mitochondria is independent of the uptake of lysine by mitochondria as evidenced by the insensitivity of homocitrulline formation to changes in the matrix pH, in contrast to citrulline formation from ornithine. High-performance liquid chromatography separates the lysine transcarbamylase activity from the ornithine transcarbamylase activity. It is concluded that the lysine transcarbamylase activity is localized outside the inner mitochondrial membrane.

Animals↗
PubMed1982

D-lactic acidosis in two patients with short bowel syndrome: bacteriological analyses of the fecal flora.

Two cases of D-lactic acidosis associated with short bowel syndrome are described. The administration of kanamycin to the patients showed a decrease in D-lactate in blood and urine in parallel with disappearance of metabolic acidosis. Bacteriological analyses of the fecal flora showed an increase in Lactobacillus buchneri in the first patient and Lactobacillus fermenti IVa in the second; both bacteria were sensitive to kanamycin. Quantification of in vitro production of D-lactate by each species of bacteria isolated from the feces revealed that Lactobacillus produced more D-lactate than other species of bacteria. These observations indicate that Lactobacillus may play an important role in the induction of D-lactic acidosis in patients with short bowel syndrome.

Acidosis↗
PubMed1982

Glycine cleavage system in ketotic hyperglycinemia: a reduction of H-protein activity.

Glycine cleavage activity was compared in the livers from three cases of ketotic hyperglycinemia (two cases of propionic acidemia and one case of methylmalonic acidemia) and three controls. In one case of propionic acidemia, glycine cleavage activity (5.2 nmole/mg protein/hr) was normal in the liver obtained at biopsy when the patient was well controlled by the treatment with low protein diet (0.8 g/kg/day) and the level of serum glycine was lowered to normal. In the two other cases of ketotic hyperglycinemia, glycine cleavage activity was significantly reduced in the liver obtained at autopsy when the patients died in the state of metabolic acidosis. Its activity in the liver of one case of propionic acidemia (0.7 nmole/mg protein/hr) was 6-26% of that in controls (2.7-10.8 nmole/mg protein/hr), and 2-7% in the case of methylmalonic acidemia (0.2 nmole/mg protein/hr). Analysing of the individual components of the glycine cleavage system, a marked decrease in the activity of H-protein was revealed in the livers of the both patients; it (0.2 nmole/mg protein/hr) was only 3-4% of that in controls (4.9-6.3 nmole/mg Protein/hr). These findings suggest that the reduction of the glycine cleavage system in the liver of ketotic hyperglycinemia occurs secondarily as speculated previously and is caused mainly by a decrease of H-protein activity.

Acidosis↗
PubMed1982

Comparison of cytosolic and mitochondrial enzyme alterations in the livers of propionic or methylmalonic acidemia: a reduction of cytochrome oxidase activity.

The activities of mitochondrial, cytosolic and microsomal enzymes in liver specimens obtained from three patients with propionic or methylmalonic acidemia were compared with those of control patients who had died from unrelated causes. Only the activity of cytochrome oxidase (mitochondrial enzyme) was significantly reduced in the patients of propionic acidemia and methylmalonic acidemia who were in the state of metabolic acidosis; in two patients the activity was less than 30% of that in controls, but in the other patient of propionic acidemia, who was under the treatment with a low protein diet (0.8 g/kg/day), the activity was 50% of that in controls. The metabolites of branched chain amino acids (tiglic acid, propionic acid, methylmalonic acid, succinic acid, tiglyl-CoA and propionyl CoA) exhibited no inhibitory effect on the cytochrome oxidase activity of the sonicated rat liver mitochondria. The reduction of cytochrome oxidase activity found in these organic acidemias may be caused secondarily by some unknown mechanism.

Amino Acid Metabolism, Inborn Errors↗