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Biomedical subjects

H Shintaku

Publications and source records attributed to H Shintaku.

41 records · Page 3Linked to original sources
PubMed1987

"Peripheral" tetrahydrobiopterin deficiency with hyperphenylalaninaemia due to incomplete 6-pyruvoyl tetrahydropterin synthase deficiency or heterozygosity.

Four patients in three families with "peripheral" tetrahydrobiopterin deficiency were investigated. They were characterized biochemically by a tetrahydrobiopterin-responsive hyperphenylalaninaemia, a high neopterin/biopterin ratio in urine and plasma, and normal or elevated concentrations of biopterin, homovanillic acid, and 5-hydroxyindole acetic acid in cerebrospinal fluid. From measurements of the activity of erythrocyte 6-pyruvoyl tetrahydropterin synthase (PTS, formerly called phosphate-eliminating enzyme) and phenylalanine loading tests in the patients and their parents, one patient was demonstrated to be heterozygous for PTS deficiency. The others were obviously genetic compounds (allelism) with incomplete PTS deficiency. Three of the children developed normally, two of them under treatment with tetrahydrobiopterin. In the latter two patients, significantly lower concentrations of biopterin, homovanillic acid, and 5-hydroxyindole acetic acid in cerebrospinal fluid were noted at age 7 months (when treatment was interrupted) than those observed at 3 and 5 weeks, respectively. The infant who is heterozygous for PTS deficiency was born small for gestational age and showed a moderately delayed psychomotor development. It is concluded that "peripheral" tetrahydrobiopterin deficiency is caused by a partial PTS deficiency with sufficient activity to cover the tetrahydrobiopterin requirement of tyrosine 3-hydroxylase and trytophan 5-hydroxylase in brain but not enough for phenylalanine 4-hydroxylase in liver. For therapy, tetrahydrobiopterin, 2-5 mg/kg in a single oral dose per day, is recommended to keep plasma phenylalanine normal. A careful observation of the mental development is indicated.

Alcohol Oxidoreductases↗
PubMed1986

Prenatal diagnosis of "dihydrobiopterin synthetase" deficiency, a variant form of phenylketonuria.

Amniocentesis was performed at 19 weeks gestation in a mother who had previously delivered a boy with "dihydrobiopterin synthetase" (DHBS) deficiency. The amniotic fluid contained neopterin in high (136 nmol/l) and biopterin in very low concentrations (1.8 nmol/l). The activity of the phosphate-eliminating enzyme (PEE, also called 6-pyruvoyl tetrahydropterin synthase, substrate: 7,8-dihydroneopterin triphosphate) which is present in liver and erythrocytes and defective in DHBS deficiency, was measured in the erythrocytes of the family members. The fetal sample showed only 2% of the activity of healthy adult controls and was comparable with that of the affected sibling. Obligate heterozygotes had activities around 20% of the controls. Two fetal control samples showed even higher activities than adult erythrocytes, Sepiapterin reductase activities wer normal in all cases. At autopsy, PEE deficiency was confirmed in the liver of the fetus. We concluded that DHBS deficiency (and most probably also GTP cyclohydrolase I deficiency) can be diagnosed by metabolite measurements in amniotic fluid. PEE activity is measurable in erythrocytes, although the assay needs to be improved. Since maternal tetrahydrobiopterin does not cross the placenta, treatment of a tetrahydrobiopterin-deficient fetus with tetrahydrobiopterin in utero is not possible.

Alcohol Oxidoreductases↗
PubMed1985

1-Azacycloalkyl-1,4-benzodiazepin-2-ones with antianxiety-antidepressant actions.

A series of 1-azacycloalkyl-1,4-benzodiazepin-2-ones were synthesized from 1-azacycloalkyl-2-benzoylanilines and corresponding imines and then evaluated for their central nervous system activities. Pharmacological data showed that some of these compounds have potent antidepressant properties, as assessed by their antagonism of tetrabenzine (TBZ) induced ptosis and their inhibition of [3H]norepinephrine uptake into rat brain synaptosomes, as well as their moderate antianxiety properties of preventing of pentylenetetrazol (PTZ) convulsion, suppressing conflict behavior, and displacing potential for [3H]diazepam binding. Introduction of a halogen substituent at position 7 of the 1,4-benzodiazepine ring lengthened the anti-PTZ effects, although the peak effect was slightly reduced and clearly enhanced the anti-PTZ and anticonflict properties. Introduction of Cl to the ortho position of the phenyl ring at position 5 greatly reduced the antidepressant properties. The secondary amine function of the azacyclic ring at position 1 was essential for the production of the antidepressant properties. Of these new series, 7-fluoro-5-(2-fluorophenyl)-1,3-dihydro-1-(4-piperidinyl)-2H-1,4-benzodi azepin-2 -one has the potential to become a useful antidepressant drug with a moderate antianxiety property.

Animals↗
PubMed1982

Normal pterin values in urine and serum in neonates and its age-related change throughout life.

Tetrahydrobiopterin (BH4) deficiency has been described as a form of hyperphenylalaninaemia in which severe neurological symptoms develop despite early treatment with low phenylalanine diet. In recent years it has become apparent that biopterin deficiency may be caused by a defect either of dihydropteridine reductase (DHPR, EC 1.6.99.10) or dihydrobiopterin synthetase (DHBS) (Niederwieser et al., 1979). Since it was proposed that treatment with precursors of the neurotransmitters involved could prevent neurological deterioration if started within the first months after birth (Curtius et al., 1979), screening of all neonates with hyperphenylalaninaemia for biopterin disorders, and a non-invasive reliable method for the diagnosis of two types of BH4 deficiency are needed urgently. Assessment of pterin derivatives in biological fluids, mostly in urine, by high performance liquid chromatography (HPLC) is proposed as a reliable diagnostic method and Crithidia fasciculata bioassay is also a very sensitive method of measuring biopterin activity. Thus normal values of pterin derivatives during the neonatal period are needed. Nevertheless, few reports on a small number of neonates have so far been found (Niederwieser et al., 1980). In this study we describe normal values of pterin derivatives in urine and biopterin activity in serum, and their age-related change in early neonates, young infants, children and adults.

Adolescent↗