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Biomedical subjects

N Sakura

Publications and source records attributed to N Sakura.

At least 91 records · Page 5Linked to original sources
PubMed1990

Steroid sulfatase activity in nails: screening for X-linked ichthyosis.

X-linked ichthyosis is generally diagnosed by a deficiency of steroid sulfatase activity in fibroblasts or leukocytes. We established a method of assaying nail steroid sulfatase activity for diagnostic use. Nail samples were easy to collect and handle, and satisfied the screening criteria of accuracy, sensitivity, and stability. The detergents Tween 20 and Triton-X 100, which enhance nail STS activity, enabled us to assay the activity with small amounts of nails. The detergent-facilitated assay was also suitable for use with pediatric patients, from whom small amounts of nails were collected.

Adult↗
PubMed1989

Hyperhistaminemia in patients with histidinemia due to increased decarboxylation of histidine.

Histidinemia results from a defect in the major catabolic pathway of histidine. Among the various alternative metabolic pathways, transamination, methylation and acetylation of histidine have been found to be increased, but increased decarboxylation to histamine has not been reported in histidinemia. In an attempt to confirm the possibility of increased decarboxylation of histidine, plasma histamine levels were determined by reversed-phase high speed liquid chromatography in histidinemic, atopic, and control groups. In the histidinemic group, plasma histamine levels were higher than those in the other two groups, and correlated positively with plasma histidine level. Serum IgE levels, the numbers of eosinophils and basophils, and the histaminopexic power in the histidinemic group were within the normal range. These results suggest that hyperhistaminemia is not due to allergic reactions but results from increased decarboxylation of histidine.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

Leukotriene B4 metabolism in neutrophils of patients with chronic granulomatous disease: phorbol myristate acetate decreases endogenous leukotriene B4 via NADPH oxidase-dependent mechanism.

We studied the effect of phorbol myristate acetate (PMA) on endogenous leukotriene B4 (LTB4) metabolism of calcium ionophore A23187-stimulated human neutrophils. Preincubation of normal neutrophils with PMA significantly suppressed the recovery of endogenous LTB4 induced by A23187. PMA did not suppress the recovery of LTB4 produced by neutrophils from patients with chronic granulomatous disease (CGD), which is known to be defective in NADPH oxidase activation to produce reactive oxygen species (ROS). PMA inhibited the formation of omega-oxidation products of LTB4, but enhanced arachidonic acid release in normal and CGD neutrophils. Furthermore, 5-lipoxygenase activity of 10,000 x g supernatants from normal neutrophils pretreated with PMA was equivalent to that of the controls. Decrease in LTB4 recovery was not attributed to the suppression of the intracellular Ca2+ increase. Thus, it is suggested that reactive oxygen species (ROS) produced by PMA may directly affect endogenous LTB4 and convert it into metabolite(s) distinct from omega-oxidation products.

Arachidonate 5-Lipoxygenase↗
PubMed1989

Synthesis of thyrotropin-releasing hormone-related peptides using N alpha-tert-butyloxycarbonyl-omega-(N-tert-butyloxycarbonylcarbamoyl)- alpha-amino acids.

Application of N alpha,Nca-di-tert-butyloxycarbonylhomoglutamine to synthesis of thyrotropin-releasing hormone (TRH) analogs was examined. The delta-lactam formation from homoglutaminylpeptides took place more easily than gamma-lactam formation from glutaminylpeptides in water or dioxane containing acetic acid. [pHgu1,Nva2]-TRH had dose-dependent antagonistic activity against pentobarbital anesthesia in mice, but almost no binding activity to TRH receptor in rat brain.

Amino Acids↗
PubMed1988

Defect in biosynthesis of mitochondrial acetoacetyl-coenzyme A thiolase in cultured fibroblasts from a boy with 3-ketothiolase deficiency.

The etiology of 3-ketothiolase deficiency has been attributed to a defect of mitochondrial acetoacetyl-CoA thiolase because the acetoacetyl-CoA thiolase activity in related materials is not activated by K+, a property characteristic for this enzyme. We studied the enzyme protein and the biosynthesis of mitochondrial acetoacetyl-CoA thiolase, using cultured skin fibroblasts from a 5-yr-old boy with 3-ketothiolase deficiency. The following results were obtained. (a) Activation of acetoacetyl-CoA thiolase activity by K+ was nil; (b) The enzyme activity was not affected by treatment with the antibody against mitochondrial acetoacetyl-CoA thiolase; (c) A signal for mitochondrial acetoacetyl-CoA thiolase protein was not detected in the immunoblot analysis; and (d) Pulse-chase experiments of skin fibroblasts, using [35S]methionine, revealed no incorporation of radioactivity into this enzyme. Therefore, fibroblasts from this patient lacked mitochondrial acetoacetyl-CoA thiolase protein due to a defect in its biosynthesis.

Acetyl-CoA C-Acetyltransferase↗
PubMed1988

Long-term effects of thyrotropin-releasing hormone and histidyl-proline diketopiperazine on the maturation of homeothermia and mitochondrial enzyme activities in neonatal rats.

To elucidate the mechanism by which TRH and its metabolite, histidyl-proline diketopiperazine (cyclo(His-Pro], act on the maturation of homoiothermy, the chronic effects of intrathecal administration of the peptides on body temperature, serum thyroid hormone levels, and mitochondrial energy-producing enzyme activities were examined in neonatal rats. The two peptides or an equimolar mixture of both were injected intrathecally at a dose of 3, 6 and 9 nmol for 7 consecutive days during the 1st, 2nd or 3rd week of life, respectively. Control rats were treated with saline and they were sacrificed at 6 weeks of age. Although food and water intake were not decreased, body weight gain was slightly reduced in the rats treated with TRH or cyclo(His-Pro) during the 1st and 2nd week of life, whereas the mixture-treated rats showed normal weight gain. Body temperature at 25 degrees C was not different in the TRH- and cyclo(His-Pro)-treated groups, whereas after cold exposure (5 degrees C for 3 h), the groups treated with TRH during the 1st and 2nd week of life had an impaired thermoregulation at 5 weeks of age. Serum T4 and T3 concentrations were similar in all groups, except in the rats treated with TRH during the 2nd week of life; their thyroid hormone levels were slightly reduced. The TRH treatment suppressed mitochondrial cytochrome c reductase and glucose-6-phosphatase activities, whereas cyclo(His-Pro) reduced cytochrome c reductase and malic enzyme activities. In contrast, alpha-glycerophosphate dehydrogenase was enhanced by both treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Tyrosine in position 4 is the key amino acid for the binding of angiotensin II to human arteriolar receptor.

In order to detect the portion of the angiotensin II molecule binding to the human arteriolar receptor, angiotensin II-(1-5)-pentapeptide, angiotensin II-(1-4)-tetrapeptide and angiotensin II-(1-3)-tripeptide were infused intravenously as saline solutions into the same 5 normal men from 0900 h at a rate of 30 nmol (20 micrograms)/kg.min (1.2 ml/min) for 15 minutes, at a rate of 90 nmol (54.5 micrograms)/kg.min (3.0 ml/min) for 6 minutes and at a rate of 140 nmol (54.5 micrograms)/kg.min (3.0 ml/min) for 6 minutes, respectively, on different occasions. At the end of the infusions average increases in blood pressure were 20/22 mmHg (p less than 0.001) and 6/7 mmHg (p less than 0.001), respectively, with the former 2 peptides, while the last peptide showed no pressor action at all. It had previously been found by our research group that angiotensin III, angiotensin II-(3-8)-hexapeptide, angiotensin II-(4-8)-pentapeptide, angiotensin II-(2-7)-hexapeptide, angiotensin II-(1-7)-heptapeptide and angiotensin II-(1-6)-hexapeptide have some pressor action but that angiotensin II-(5-8)-tetrapeptide has no pressor action in normal men. When these previous results are combined with the present result, it is evident that only tyrosine-containing molecules show pressor activity and that tyrosine-deleted molecules do not show pressor activity at all. It is concluded that tyrosine in position 4 is the key amino acid for the binding of angiotensin II to human arteriolar receptor.

Adult↗
PubMed1986

Effects of thyrotropin-releasing hormone and cyclo-histidine-proline on the homeothermic development of neonatal rats.

The effects of thyrotropin-releasing hormone (TRH) and its putative metabolite, cyclo-histidine-proline (cHP), on the homeothermic development of neonatal rats were studied. The daily intrathecal administration of 10(-11)-10(-9) moles of TRH during the second week of age produced a significant rise in body temperature by 3 weeks of age and was followed by a transient period of hypothermia. This effect, which could not be produced by an intraperitoneal injection of 10(-7) moles of TRH, was abolished by the simultaneous administration of 6-hydroxydopamine (6OHD). In contrast, intrathecally administered cHP decreased thermogenesis. During TRH treatment, brain norepinephrine (NE) and dopamine (DA) release was accelerated 2- to 4-fold. Two weeks after either TRH or cHP treatment, brain NE and DA were significantly reduced; adrenal NE in cHP-treated rats increased. The weight of the interscapular brown adipose tissue (BAT) was decreased by both cHP and 6OHD. At 3 weeks of age, [3H]guanosine diphosphate binding capacity in BAT mitochondria was reduced by 60% in TRH-treated rats and was associated with reduced mitochondrial levels of alpha-glycerophosphate dehydrogenase and liver cytochrome C reductase. These results indicate that TRH stimulates central NE release thereby enhancing thermogenesis, cHP decreases heat production, and TRH-induced hyperthermia is associated with changes in mitochondrial exothermic processes. The central TRH-cHP system may modulate the maturation of homeothermic mechanism in neonatal rats.

Adipose Tissue, Brown↗
PubMed1985

Altered metabolic profiles of valproic acid in a patient with Reye's syndrome.

Urinary valproate metabolite and endogenous organic acid profiles in a 6-yr-old girl with Reye's syndrome were investigated by means of gas chromatography-mass spectrometry. 2-n-Propyl-3-oxovaleric acid, normally the major metabolite of valproate in man, was undetectable, while 2-n-propylglutaric acid, the end product via omega-oxidation was markedly increased. Polyunsaturated valproate was not found. Valproate-glucuronide was still found as the major metabolite. The clinical findings coupled with a greatly increased excretion of lactate and adipate was compatible with Reye's syndrome. Ketone bodies were not detectable. This case study shows that Reye's syndrome causes altered valproate metabolism, consistent with the defective mitochondrial beta-oxidation of medium chain fatty acids, and suggests that valproic acid should not be used in the treatment of seizures in patients with this syndrome.

Biotransformation↗
PubMed1985

Cushing's disease: pituitary microadenoma demonstrated by high resolution computed tomography with thin slices.

A girl 16 7/12 years of age with Cushing's disease secondary to pituitary microadenoma is described. The tumor was very clearly demonstrated by high-resolution contrast-enhanced computed tomography (CT) with thin slices and was removed by transsphenoidal microadenomectomy. In some patients with Cushing's disease levels of ACTH and cortisol are not always high. Therefore, high-resolution contrast-enhanced CT with thin slices should be performed when the diagnosis of Cushing's disease is suspected even when the definite diagnosis cannot be established by endocrinological examinations.

Adenoma↗