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Biomedical subjects

F A Hommes

Publications and source records attributed to F A Hommes.

At least 37 records · Page 2Linked to original sources
PubMed1988

The development of the muscarinic acetylcholine receptor in normal and hyperphenylalaninemic rat cerebrum.

The effect of hyperphenylalaninemia on the development of the muscarinic acetylcholine receptor in rat cerebrum has been studied. Rats were subjected to the hyperphenylalaninemic regimen as of 5 days of age. A gradual and steady decrease in the number of binding sites for L-[3H]quinuclidinylbenzilate was observed, with the white matter more affected than the gray matter. A return to normal blood phenylalanine levels after the age of 21 days does not lead to an increase in this number of binding sites.

Aging↗
PubMed1988

Activity of arylsulfatase A, B-glucosidase and hexosaminidases in chorionic villi at six, eight and ten weeks' gestational age.

Chorionic villus sampling is becoming an accepted method of prenatally diagnosing metabolic diseases. There are few published data on sampling at various gestational ages. Different investigators, using different methods of chorionic biopsy, perform the sampling at various gestational ages. Accurate interpretation of results is dependent on reliable normal values, which could differ on the basis of gestational age. The enzymatic activities of arylsulfatase A, B-glucosidase and hexosaminidases were compared in trophoblast from six-, eight- and ten-week gestations. No significant differences in activity levels were detected. This finding confirms the accuracy of metabolic diagnosis for these enzyme-deficiency syndromes in trophoblastic tissue at gestational ages of six to ten weeks without a requirement for gestational-age-specific normal values.

Cerebroside-Sulfatase↗
PubMed1987

Purification and some properties of liver adenylylsulfate kinase.

Adenylylsulfate kinase (ATP:adenylylsulfate 3'-phosphotransferase, EC 2.7.1.25) has been purified over 1300-fold from rat liver in 10% yield. The enzyme has a molecular weight of 58,000 and is composed of four subunits of equal molecular weight. ATP is an allosteric activator of adenylylsulfate kinase, with a Hill coefficient of 2.2 and a K0.5 of 2.5 mM. Adenosine phosphosulfate is a potent inhibitor of adenylylsulfate kinase, but the adenosine phosphosulfate concentration for maximal reaction is dependent on the ATP concentration. At the physiological levels of ATP the inhibition by adenosine phosphosulfate is not likely to play a role, while the allosteric regulation of adenylylsulfate kinase by ATP may be operative.

Adenosine Phosphosulfate↗
PubMed1987

Properties of the 3'-phosphoadenosine-5'-phosphosulfate (PAPS) synthesizing systems of brain and liver.

Chromatography of brain and liver 100,000 g supernatants over HPLC molecular sieve columns revealed striking differences in the molecular weight distribution of ATP-sulfurylase and APS-kinase of the two tissues, pointing to different enzymic species for both enzymes in brain and liver. This was further substantiated by kinetic characterization of the two enzymes of both tissues. APS-kinase of liver is allosterically activated by ATP, while the brain enzyme is not. ATP-sulfurylase of brain is activated at high, but still physiological concentrations of ATP. Brain ATP-sulfurylase is inhibited by phenylalanine.

Adenine Nucleotides↗
PubMed1986

HPLC assay of phenylalanine and tyrosine in blood spots on filter paper.

Blood spots on filter paper are used to screen for phenylketonuria. We have developed a high pressure liquid chromatographic assay of phenylalanine and tyrosine after elution of these amino acids from filter paper. The analysis time is 20 min. The amino acids are separated using an ion-exchange resin with post-column ortho-phthalaldehyde derivatization and subsequent fluorescence detection. Other common amino acids do not interfere. The assay is linear from 20 pmol to at least 2,000 pmol with a coefficient of variation of 3%. The assay is as accurate as the determination of phenylalanine by ion-exchange ninhydrin-reactive methods currently in use, but is 100 times more sensitive. The method has the advantages of avoiding venipuncture, is cost effective, has a high sensitivity, and a rapid turnaround.

Adult↗
PubMed1986

Combined xanthine and sulphite oxidase defect due to a deficiency of molybdenum cofactor.

Increased urinary excretion of xanthine, hypoxanthine, sulphite, thiosulphate and decreased serum uric acid were observed in an infant with profound failure to thrive. Other clinical findings included refractory seizures, spastic quadriplegia and profound psychomotor retardation. The patient died at 20 months of age. There were no detectable activities for xanthine oxidase and sulphite oxidase in the postmortem liver. Urothione, which is the metabolic excretory product of the molybdenum cofactor for molybdoenzymes was not present in the urine. A deficiency of the molybdenum cofactor which is common to both xanthine and sulphite oxidase is presumed to be the metabolic defect responsible for the absent activities of both enzymes.

Coenzymes↗
PubMed1986

The assay of ATP-sulfurylase.

An assay method for ATP-sulfurylase is described, based on the incorporation of 35SO4(2-) into adenosine-5'-phosphosulfate (and 3-phosphoadenosine-5'-phosphosulfate) and the separation of these compounds by HPLC. Since the enzyme is easily inactivated at temperatures above 20 degrees C during the assay, the reaction time should not exceed 10 min.

Adenosine Phosphosulfate↗
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↗
PubMed1986

Biotin.

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Adult↗
PubMed1986

Anticonvulsive drugs and blood levels of lactate, pyruvate, and glucose in children with seizures.

Lactate, pyruvate, and glucose were determined in groups of 10 patients, each receiving single drug therapy for their seizure disorder with either phenytoin, valproic acid, carbamazepine, or phenobarbital, and in patients not taking medication. All drug levels were in their therapeutic ranges. The characteristics of the groups were similar, except for the phenytoin group being significantly older. No significant differences were found in glucose or pyruvate concentrations. However, patients on valproic acid had reduced lactate (p less than 0.05) and L/P ratios (p less than 0.05). The reduction in lactate in patients on valproate therapy may mask inborn errors of metabolism that normally result in an increase in blood lactate levels.

Anticonvulsants↗
PubMed1985

Biochemical observations on a case of hepatic fructose-1,6-diphosphatase deficiency.

A case of hepatic fructose-1,6-diphosphatase deficiency is described. She presented with congenital bilateral cataracts, failure to thrive, hypoglycaemia and hyperlactacidaemia. A liver biopsy revealed normal levels of gluconeogenic enzymes except fructose-1,6-diphosphatase which was present at 30% of the level of the lower control values. The residual activity had a normal affinity for fructose-1,6-diphosphate, a decreased sensitivity for inhibition by fructose-2,6-diphosphate and an increased resistance toward conversion to the AMP-insensitive form of the enzyme. As a result of this mutation, the residual FDPase will always be maintained in the AMP-inhibited form.

Adenosine Monophosphate↗
PubMed1985

Serum carnosinase deficiency: a non-disabling phenotype?

Serum carnosinase deficiency (McKusick 21220) is a rare condition, described in 13 cases. Ten additional individuals with serum carnosinase deficiency have been identified. All continued to excrete increased amounts of carnosine in their urine despite a meat-free diet for 3 days. Serum carnosinase activity ranged from 0-30% of normal. In four individuals a normal Km for carnosine of 0.12 mM was observed, while in five individuals an increased Km was found. Homocarnosine levels in CSF in three individuals ranged from 3.4 to 15 mM. Clinical symptoms in these individuals were as follows: attention deficit disorder: 4; non progressive developmental delay: 1; neurofibromatosis: 1; absences seizures: 1; severe, but non-progressive mental retardation, seizures and neurosensory hearing loss: 1; progressive childhood dementia; 1; clinically normal: 1. There was no correlation between severity and type of the neurological symptoms and residual serum carnosinase activity. Although a definite conclusion can only be made after a considerably higher number of individuals has been analyzed, the suspicion that serum carnosinase deficiency is unrelated to the neurological symptoms is strengthened by these observations. There may, however, be an association with a predisposition for mental deficiency.

Carnosine↗
PubMed1984

Gamma-glutamylornithine excretion in patients with hyperornithinemia.

Gamma-glutamylornithine has been identified in urine from patients with the HHH syndrome (hyperornithinemia, hyperammonemia and homocitrullinuria) and with gyrate atrophy associated with hyperornithinemia. The amount of gamma-glutamylornithine excreted was 10-15 times higher than that excreted in normal subjects. The level of excretion was comparable in the HHH syndrome subjects and the gyrate atrophy subjects despite the fact that the gyrate atrophy subjects excreted more ornithine. A 100 mg/kg oral challenge of ornithine increased the excretion of gamma-glutamylornithine by a factor of three. This increased excretion of gamma-glutamylornithine was observed in hyperornithinemia patients with different etiologies and is therefore presumably due to the hyperornithinemic state, per se, independent of the underlying defect.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

Reconstitution of ornithine transport in liposomes with Lubrol extracts of mitochondria.

The ornithine translocase of beef liver mitochondria was extracted with Lubrol WX and reconstituted in liposomes. The uptake of ornithine by the reconstituted vesicles followed Michaelis-Menten kinetics, and was dependent on the intraliposomal pH, the time of sonication of the reconstituted liposomes and the phospholipid to detergent ratio. It is concluded that the ornithine translocator can be reconstituted, which makes the purification of this translocator feasible.

Amino Acid Transport Systems, Basic↗
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↗