Search PubMed⌕ Search

Biomedical subjects

D M Danks

Publications and source records attributed to D M Danks.

At least 163 records · Page 9Linked to original sources
PubMed1980

Reduced lysyl oxidase activity in skin fibroblasts from patients with Menkes' syndrome.

Lysyl oxidase activity against both collagen and elastin substrates has been examined in the culture medium of skin fibroblasts derived from unrelated patients with Menkes' syndrome and from control subjects. The medium of three Menkes' fibroblast lines showed 3--30% of the activity present in the medium of control fibroblasts, against a purified collagen substrate. Lysyl oxidase activity in the culture medium of two of the Menkes' fibroblast lines was also examined by using a crude aortic-elastin substrate and was similarly decreased in comparison with that in the medium of control fibroblasts. Lysyl oxidase activity in the medium of a fourth fibroblast line, derived from a foetus with Menkes' syndrome, was 42% of that in the medium of control fibroblasts derived from a 1-day-old baby against a collagen substrate, and 26% of that in control fibroblast medium against an elastin substrate. The copper content of the cell layers of the Menkes' fibroblast cultures was elevated in comparison with normal fibroblast cultures, as has previously been reported to be characteristic of such cells. It is suggested that the decrease in lysyl oxidase activity would help to explain the connective tissue defects observed in Menkes' syndrome, and that this reduction, in conjunction with the elevated concentrations of cellular copper, would support the hypothesis that a functional intracellular copper deficiency exists in Menkes' syndrome.

Adult↗
PubMed1980

Copper deficiency in humans.

Copper deficiency of nutritional origin has been recognized as an important part of complex nutritional problems in Peru, as an occasional even in premature babies in Western countries, and as a real hazard of over-zealous zinc therapy or of prolonged parenteral alimentation in children or adults. Anaemia, osteoporosis and scurvy-like bone changes are recognized in the deficiency, and they respond to copper. Copper intake is falling in western countries as a result of prepackaging of foods, and low-grade chronic deficiency may become a problem. The features seen in Menkes' syndrome suggest that human beings may be rather susceptible to the vascular and neurological effects of copper deficiency; these effects may be encountered as a consequence of prolonged mild copper deficiency. Measurement of the serum concentrations of caeruloplasmin before and after moderate copper repletion is suggested as a method of detecting mild copper deficiency.

Animals↗
PubMed1980

Genetics of mammalian phenylalanine hydroxylase system. IV. Evidence of phenylalanine hydroxylase in a cultured human hepatoma cell line.

We report here te identification of a cultured human hepatoma cell line which possesses an active phenylalanine hydroxylase system. Phenylalanine hydroxylation was established by growth of cells in a tyrosine-free medium and by the ability of a cell-free extract to convert [14C]phenylalanine to [14C]tyrosine in an enzyme assay system. This enzyme activity was abolished by the presence in the assay system of p-chlorophenylalanine but no significant effect on the activity was observed with 3-iodotyrosine and 6-fluorotryptophan. Use of antisera against pure monkey or human liver phenylalanine hydroxylase has detected a cross-reacting material in this cell line which is antigenically identical to the human liver enzyme. Phenylalanine hydroxylase purified from this cell line by affinity chromatography revealed a multimeric molecular weight (estimated 275,000) and subunit molecular weights (estimated 50,000 and 49,000) which are similar to those of phenylalanine hydroxylase purified from a normal human liver. This cell line should be a useful tool for the study of the human phenylalanine hydroxylase system.

Animals↗
PubMed1980

Altered copper metabolism in cultured cells from human Menkes' syndrome and mottled mouse mutants.

Cultured cells of a variety of different types from human Menkes' syndrome patients and brindled mouse mutants exhibit similarly altered responses to changes in extracellular copper concentration. This suggests that the mutations in the mouse and human are very similar and that mutant gene expression is occurring in many different tissues. Intracellular copper levels are markedly elevated in mutant cells in normal medium and in medium containing a hundred-fold higher copper. Some cell lines from heterozygotes possess elevated copper levels. Elevated extracellular copper and zinc are significantly more toxic to mutant cells. Mutant cells exhibit normal rates of uptake of copper-64 over a 10-min period but abnormally high accumulation over 24 hr and low rates of efflux. Menkes' fibroblasts become saturated with copper-64 at lower extracellular concentrations than for normal fibroblasts. These data support the idea of enhanced intracellular binding in mutant cells.

Animals↗
PubMed1980

Observations indicating the nature of the mutation in phenylketonuria.

Rabbit antiserum was prepared against purified normal human liver phenylalanine hydroxylase. This was used to test for cross-reacting material in crude extracts of livers from patients with classical phenylketonuria (PKU); the samples from patients were two livers obtained at autopsy and a needle biopsy core. None of these enzymically inactive livers contained detectable cross-reacting material capable of neutralizing antibody activity in double immunodiffusion and/or enzyme inhibition experiments. In an earlier study, no phenylalanine hydroxylase was found in the two autopsy PKU livers by an affinity chromatography method or by the use of a specific antiserum raised against purified monkey liver phenylalanine hydroxylase (Choo et al., 1979a). This evidence suggests that mutations in th PKU patients studied may be regulatory in nature.

Antigen-Antibody Complex↗
PubMed1980

Abnormal copper metabolism in cultured fibroblasts from patients with Wilson's disease.

Skin fibroblasts derived from patients with Wilson's disease have, under certain conditions, elevated concentrations of copper. However, the levels of intracellular copper varied from one experiment to another and the reason for this inconsistency has not yet been determined. 64Cu retention after 24 hours and its release in "chase" experiments was not abnormal, thus distinguishing these fibroblasts from Menkes' syndrome fibroblasts. The data provides evidence that the mutant gene responsible for Wilson's disease is expressed in fibroblasts under certain conditions.

Adolescent↗
PubMed1979

Dihydropteridine reductase deficiency diagnosis by assays on peripheral blood-cells.

Human peripheral lymphocytes, granulocytes, and platelets contain the enzyme dihydropteridine reductase. A simple procedure and assay for diagnosing dihydropteridine reductase on peripheral blood is described. In twelve controls the level of enzyme activity in a lymphocyte-platelet preparation was 29.5 +/- 4.8 (SD) nmol NADH oxidised/min/mg protein. Two heterozygotes for dihydropteridine reductase deficiency had activities of 6.4 and 10.3 nmol NADH oxidised/min/mg protein, respectively.

Blood Platelets↗
PubMed1979

Genetics of the mammalian phenylalanine hydroxylase system. Studies of human liver phenylalanine hydroxylase subunit structure and of mutations in phenylketonuria.

Phenylalanine hydroxylase was purified from crude extracts of human livers which show enzyme activity by usine two different methods: (a) affinity chromatography and (b) immunoprecipitation with an antiserum against highly purified monkey liver phenylalanine hydroxylase. Purified human liver phenylalanine hydroxylase has an estimated mol. wt. of 275 000, and subunit mol. wts. of approx. 50 000 and 49 000. These two molecular-weight forms are designated H and L subunits. On two-dimensional polyacrylamide gel under dissociating conditions, enzyme purified by the two methods revealed at least six subunit species, which were resolved into two size classes. Two of these species have a molecular weight corresponding to that of the H subunit, whereas the other four have a molecular weight corresponding to that of the L subunit. This evidence indicates that active phenylalanine hydroxylase purified from human liver is composed of a mixture of sununits which are different in charge and size. None of the subunit species could be detected in crude extracts of livers from two patients with classical phenylketonuria by either the affinity or the immunoprecipitation method. However, they were present in liver from a patient with malignant hyperphenylalaninaemia with normal activity of dihydropteridine reductase.

Adolescent↗
PubMed1979

Human dihydropteridine reductase: a method for the measurement of activity in cultured cells, and its application to malignant hyperphenylalaninemia.

1. The kinetic, assay and culture variables involved in the determination of dihydropteridine reductase activity in human cultured cells have been investigated, and a modified assay is described which allows for accurate determination of activity. Unlike previously used assays, this assay utilizes saturating concentrations of substrates and its increased sensitivity allows for excellent replication on a smaller number of cells than was previously required. 2. The modified assay was used to investigate the levels of dihydropteridine reductase in patients with malignant hyperphenylalaninemia; results of assay for the enzyme in cultured cells from affected infants and parents are presented. These are compared with control data for dihydropteridine reductase activity in fibroblasts and continuous lymphoid cells from normal controls and phenylketonuric patients, in normal amniotic cells and in liver obtained at autopsy.

Amniotic Fluid↗
PubMed1979

Copper metabolism in mottled mouse mutants: copper concentrations in tissues during development.

The copper content of various organs of ;brindled' female heterozygotes and male mice affected by this X-linked mutation are documented at the last day of intrauterine development, at 1 day after birth and at 11 days of age. The findings indicate defective placental transfer of copper in utero, and an even more marked defect in intestinal absorption of copper after birth. In addition there is an abnormal distribution of copper among the tissues of the body once it is absorbed. The mutation produces abnormal accumulation of copper in kidney, in gut mucosa and in testis, whereas liver, brain, plasma and most other organs show diminished copper concentrations. The intestinal malabsorption of copper is accompanied by accumulation of abnormal amounts of the metal in the intestinal-mucosa cells. Copper concentrations in both mucosa and luminal contents rise progressively from duodenum to ileum. Defective upper-intestinal absorption, consequent progressive increase in luminal copper concentration and pinocytosis in the ileum would seem to explain the findings. Radioisotopic studies eliminated the possibility of excessive excretion of copper in bile or across the intestinal mucosa. Detailed comparison with findings in humans with Menkes' syndrome is difficult because of the different stages of development at which the studies have been performed, but the results seem in general to conform very satisfactorily. Those differences seen are probably explicable by known species differences. All the findings are in accord with a hypothesis that the basic defect involves accumulation and retention of copper in the cells of affected tissues such as kidney, gut mucosa and placenta.

Animals↗
PubMed1979

Copper metabolism in mottled mouse mutants: copper therapy of brindled (Mobr) mice.

Copper therapy was applied to brindled mouse mutants, which suffer from lethal hypocupraemia, by using cuprous and cupric solutions. The method of treatment was a single subcutaneous injection of 50 microgram of copper at 7 days of age. Early effects of the dose were: prevention of the tremors and spasms seen in untreated mutants, raising to normal and near-normal of caeruloplasmin oxidase and lysyl oxidase activities and pigmentation of skin and fur. Growth of mutants was retarded up to 23 days of age, but thereafter they rapidly gained weight to be nearly normal by 60 days of age. At 3 days after injection, copper concentrations in previously deficient mutant organs apart from liver were at least as much as those of treated normals, which had remained unchanged. Copper in mutant livers had increased only slightly in comparison with the normal control. A state of copper deficiency recurred in mutant tissues by 25 days after injection. A solution of Cu+, retained as such by an alkyl polyether, and sebacic acid resulted in greater growth rates after 23 days than did three other copper treatments. Cu+ may have resulted in an improved growth response owing to it being more readily metabolized than C12+. Delayed release of copper from the site of injection may have played an important role.

Animals↗
PubMed1979

Copper metabolism in mottled mouse mutants: distribution of 64Cu in brindled (Mobr) mice.

1. Duodenal injection of 64Cu in treated adult mutant mice (Mobr/y) revealed severe malabsorption of copper. In suckling mutants, malabsorption was less severe, owing to delayed absorption between 2 and 5 h after injection. Pinocytosis at the distal small intestine seems the likely explanation for this difference, and this is supported by results of ileal injection of radioisotope in the suckling mice. 2. The distribution of 64 Cu in various organs was measured in suckling normal, mutant and heterozygote mice and in adult normal and mutant mice during 48 h after intracardiac injection. Excessive accumulation of radioisotope was observed in most extrahepatic organs of mutant and heterozygote mice and was most pronounced in kidney. This could not be explained by initial copper deficiency. The livers of suckling mutant and heterozygote mice lost radioisotope rapidly after normal initial uptake. This pattern was not seen in adult mutants.

Animals↗