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Biomedical subjects

D M Danks

Publications and source records attributed to D M Danks.

At least 91 records · Page 5Linked to original sources
PubMed1988

Application of DNA-DNA hybridization of dual labeled probes to the detection of trisomy 21, monosomy 21, and sex determination.

Chromosomal aneuploidy is usually identified by cytogenetic methods. However, for some purposes it would be desirable to have an easier method of recognizing specific trisomies or monosomies. We have devised such an assay. It involves the simultaneous hybridization of two chromosome-specific DNA probes labeled with different isotopes (32P and 35S) to human chromosomal DNA immobilized on a nitrocellulose filter. The hybridization signals are then counted, and the dpm ratios between the two isotopes are determined. In this paper we show the application of this technique in sex determination, in the analysis of two human cell lines reported to have chromosome 21 monosomy, and, especially, in testing for Down syndrome.

Cell Line↗
PubMed1987

Mild Sanfilippo syndrome: a further cause of hyperactivity and behavioural disturbance.

Sanfilippo syndrome (mucopolysaccharidosis type III) usually presents with severe behavioural disturbance and it has characteristic features. The patient's condition follows a neurodegenerative course; death generally occurs in the second decade. Five patients, from three families, who presented with a mild variety of the syndrome are reported here. Four of the five patients did not show the usual somatic features, and none showed regression. It is important that clinicians be aware of this mild variant so that appropriate tests can be undertaken in retarded children and adults.

Adult↗
PubMed1987

Uptake and efflux of copper-64 in Menkes'-disease and normal continuous lymphoid cell lines.

The accumulation of copper over 2 h by normal lymphoid cells and those from Menkes'-disease patients (Menkes' cells) was found to be biphasic, with an initial phase of rapid uptake, an approach to steady state at around 40-60 min, followed by a further accumulation phase. The accumulation of copper was not diminished by the addition of a variety of metabolic inhibitors, suggesting that copper uptake is not an active process. The presence of carbonyl cyanide m-chlorophenylhydrazone in the culture medium stimulated the uptake and accumulation of copper in both normal and Menkes' cells to the same absolute level. This effect appeared to be specific for copper, since the accumulation of Zn and Cd was unaffected. Menkes' cells did not differ from normal in their initial rate of copper uptake. Analysis of the uptake curve suggested that the membrane transport of copper involves both passive and facilitated diffusion. Initial rate of efflux from the cells was approximated by two methods. Menkes' cells did not appear to be affected in this function. It seems likely that the basic defect in Menkes' disease involves a step in intracellular copper transport rather than the membrane transport of copper.

Antimetabolites↗
PubMed1987

Profound neurological illness, relieved by protein restriction, in a baby with a transient disturbance in the metabolism of ingested isoleucine.

An 8-month-old infant presented because of poor development followed by the acute onset of cortical blindness and a severe seizure disorder at the time of changing from breast to formula feeding. Metabolic investigations revealed an increased urinary excretion of 2-methyl-3-hydroxybutyric, methylmalonic and 2-ethylhydracrylic acids. The concentration of these compounds in urine was augmented by oral protein (5 g/kg per day) and isoleucine loading. A low protein diet (1.5 g/kg per day) produced a dramatic response with complete cessation of seizures and a marked improvement in vision and general development. After many months of low protein diet, the biochemical abnormalities were no longer detectable, even after protein loading. Extensive investigations have failed to reveal an intrinsic enzyme defect which would account for these clinical and biochemical findings. A toxic effect of a bacterial metabolite of isoleucine is proposed.

Amino Acid Metabolism, Inborn Errors↗
PubMed1987

Stability of protein and mRNA in human postmortem liver--analysis by two-dimensional gel electrophoresis.

The method of two-dimensional polyacrylamide gel electrophoresis has been used to investigate the post mortem stability of protein and mRNA in human liver. The electrophoretic mobility of proteins and of the in vitro translation products of the mRNA were found to be essentially unaffected by incubation of the liver at 37 degrees C for up to 2 h or at 4 degrees C for up to 16 h. This study indicates that the major protein and mRNA species in liver are stable enough following death to allow meaningful studies on tissue collected under standard autopsy conditions.

Adolescent↗
PubMed1987

Albumin has no role in the uptake of copper by human fibroblasts.

The mechanism of copper uptake by cells has been the subject of controversy for some time. This paper examines the possibility of a role for albumin in the uptake of copper by fibroblasts. Although the cells could accumulate copper from a copper-albumin complex, there was no evidence for either copper-albumin or albumin receptors on the cell surface. The possibility of a surface exchange mechanism for copper was examined. While copper uptake showed saturation with increasing concentrations of labelled copper-albumin, adding unlabelled copper to the incubation medium did not inhibit uptake. Adding albumin or histidine to the copper-albumin complex resulted in an inhibition of copper uptake. The results can only be explained by the cell taking up free copper from the incubation medium, with the albumin then releasing its copper to maintain the equilibrium between free and bound metal. Since, in vivo there is essentially no free copper in serum, it is concluded that albumin is most unlikely to play a role in the uptake of copper by fibroblasts.

Albumins↗
PubMed1987

Nonketotic hyperglycinemia: analyses of glycine cleavage system in typical and atypical cases.

The molecular nature of the glycine cleavage system was investigated in eight patients with typical (neonatal) and two patients with atypical (late onset) nonketotic hyperglycinemia (NKH). The overall activity of the glycine cleavage system was found to be decreased in all of the liver and brain tissue studied, but it was undetectable or extremely low in typical NKH, whereas there was some residual activity in atypical NKH. Six patients with typical NKH had a specific defect in the P protein, and one a defect in the T protein; the activity of the T protein was defective in one patient with atypical NKH.

Amino Acid Oxidoreductases↗
PubMed1987

The mucopolysaccharidoses.

The experience of the Royal Children's Hospital in managing patients with mucopolysaccharidosis is discussed. All share the common feature of abnormal storage, within lysosomes, of partially degraded glycosaminoglycans, but different diseases within the group as a whole present different problems. The presentation, diagnosis and clinical outcome of 69 affected children are described.

Child↗
PubMed1987

Future developments in phenylketonuria.

Treatment of classical phenylketonuria (PKU) is very good, but problems still exist in regard to the duration of treatment and a means of ensuring that all women with PKU recommence dietary treatment before becoming pregnant. A 'one-shot' cure of the disease remains desirable and may become available in the more distant future by somatic cell gene therapy. Insertion of a normal gene or correction of the defective gene at the normal site in the chromosome and in liver cells is likely to be necessary both technically and ethically. Prevention by prenatal diagnosis is not widely accepted in Australia and is likely to have little effect on the frequency of the disease.

Female↗
PubMed1986

Comparisons of copper deficiency states in the murine mutants blotchy and brindled. Changes in copper-dependent enzyme activity in 13-day-old mice.

The activity of two copper-dependent enzymes, cytochrome c oxidase and copper, zinc-superoxide dismutase, was determined in six tissues of age-matched (13-day-old) copper-deficient mutant and normal mice. In the two mutants 'brindled' and 'blotchy', brain, heart and skeletal muscle had significant enzyme deficiencies. Cytochrome c oxidase was more severely affected than was superoxide dismutase. In these three tissues the degree of deficiency could be correlated with decreased copper concentration; however, enzyme activity was normal in liver, kidney and lung, despite abnormal copper concentrations in these tissues. In nutritionally copper-deficient mice, all six tissues showed decreased enzyme activity, which was most marked in brain, heart and skeletal muscle, the tissues which showed enzyme deficiencies in the mutants. Analysis in vitro of cytochrome c oxidase (temperature coefficient = 2) at a single temperature was found to underestimate the deficiency of this enzyme in hypothermic copper-deficient animals. Cytochrome c oxidase deficiency may therefore be sufficiently severe in vivo to account for the clinical manifestations of copper deficiency. An injection of copper (50 micrograms of Cu+) at 7 days increased cytochrome c oxidase activity by 13 days in all deficient tissues of brindled mice, and in brain and heart from blotchy mice. However, skeletal-muscle cytochrome c oxidase in blotchy mutants did not respond to copper injection. Cytochrome c oxidase activity increased to normal in all tissues of nutritionally copper-deficient mice after copper injection, except in the liver. Hepatic enzyme activity remained severely deficient despite a liver copper concentration three times that found in copper-replete controls. Superoxide dismutase activity did not increase with treatment in either mutant, but its activity was higher than control levels in nutritionally deficient mice after injection. This difference is probably due to sequestration of copper in mutant tissue such as kidney, but a defect in the copper transport pathway to superoxide dismutase cannot be excluded.

Animals↗
PubMed1986

A study of the role of metallothionein in the inherited copper toxicosis of dogs.

The role of metallothionein (MT) was assessed in the copper-loading disease prevalent in Bedlington terriers. Fractionation of tissue supernatants over Sephadex G-75 showed that most of the additional cytosolic copper present in liver tissue of these dogs was bound to MT, and that substantially more MT-bound copper could be solubilized by detergent plus mercaptoethanol. Zinc contents were only slightly raised, although most of the extra zinc was associated with a 4000-Mr ligand. Ion-exchange chromatography revealed two isoproteins, MT1 and MT2, in all the dog liver samples examined. In Bedlington terrier liver, copper associated with both isoproteins was increased, although the increase for MT2 was greater than for MT1. The content of MT protein was also raised, although cell-free translations and RNA blots of total liver RNA showed that this increase was not associated with a rise in MT mRNA. The significance of these results to the mechanism of copper accumulation in the Bedlington terrier disorder is discussed.

Animals↗
PubMed1986

Difficulties in assessing the effect of strychnine on the outcome of non-ketotic hyperglycinaemia. Observations on sisters with a mild T-protein defect.

Sisters with a mild variant of non-ketotic hyperglycinaemia resulting from a defect in the T-protein of the glycine cleavage system had different clinical outcomes. The older sister was ascertained at 6 months of age because of mental retardation. She received only brief treatment with sodium benzoate from 11-15 months and at 15 years of age is profoundly retarded and has epilepsy. The younger sister was diagnosed 36 h after birth, was treated with strychnine, sodium benzoate and arginine from the neonatal period and at 27 months of age is only moderately retarded and free of seizures. The possible role of strychnine in the improved outcome is discussed.

Adolescent↗
PubMed1986

X linked hydrocephalus: a survey of a 20 year period in Victoria, Australia.

This study ascertained 164 males with non-communicating hydrocephalus in live or stillborn patients in Victoria. Australia in 1962 to 1982, after excluding those cases secondary to brain malformations other than aqueduct stenosis. Ascertainment was considered near complete, especially for the period since 1974, but details of the aqueduct pathology were inadequate in half the cases. A total of 91 families was seen to record detailed family information. The overall incidence of primary non-communicating hydrocephalus was estimated to be 0.6 +/- 0.2 per 1000 live and stillbirths, with three-fifths of the cases male. Twelve patients were classified as having definite X linked hydrocephalus and 13 others as probable cases of this condition. Deformities of the thumbs (generally adduction deformity) were present in nearly half of these cases. The pyramids were absent from sections of the medulla whenever these were available. Four of five survivors had signs suggesting pyramidal tract lesions, compared to four of 25 surviving non-X linked cases. The intellectual outcome was notably poorer in the X linked cases. Poor school performance was also described in five of 19 mothers of X linked cases but in only one of 64 mothers of the remaining cases. Familial recurrence in the whole group of patients was almost confined to the X linked families. The exceptions were two families in whom autosomal recessive inheritance is possible. It is important to remember X linked hydrocephalus in genetic counselling. Examination of the thumbs, search for clinical signs of pyramidal tract lesions, and anatomical examination of the pyramids in medullary sections are all important, along with careful questioning for a history of affected maternal relatives. The presence of any of these features is grounds for counseling on the basis of X linked inheritance. An empirical figure was derived to use when counseling about a male with non-communicating hydrocephalus in whom there is no adequate information about the thumbs or the pyramids: a 4% recurrence risk in male sibs and 2% in females.

Australia↗
PubMed1986

Of mice and men, metals and mutations.

Several mutations affecting the transport of copper and zinc in humans and in mice have been discovered over the last 15 years, joining the long known disturbance of copper transport in Wilson's disease. Menkes' disease (classical and mild variant forms) and X linked Ehlers-Danlos syndrome (type IX, X linked cutis laxa) have features in common with one another and with the brindled (Mobr) and blotchy (Moblo) mouse mutants, respectively. There may be one allelic series of mutants in each species or two loci may be involved in each. The toxic milk mutant (tx) in the mouse may be homologous to Wilson's disease in man. The defect of intestinal absorption of zinc in acrodermatitis enteropathica has no homologue yet in the mouse. However, the lethal milk (lm) mutant in the mouse may be homologous to a condition of zinc deficiency described in a few breastfed, low birth weight infants. Many more genetic defects of transport of copper and of zinc may await discovery. Conversely, these mutants are valuable in elucidating the normal processes of copper and zinc transport.

Acrodermatitis↗