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Biomedical subjects

A C Pollard

Publications and source records attributed to A C Pollard.

At least 19 recordsLinked to original sources
PubMed1997

Using metaphors to assess anticipatory perceptions of personal death.

The Revised Death Fantasy Scale (RDFS) is an 18-item measure based on metaphors of personal death. It was constructed to assess psychological aspects of contemplating personal death, at levels of awareness less conscious than those tapped by conventional self-report measures. It contains two subscales: Positive Metaphors and Negative Metaphors. In several studies the RDFS has shown evidence of reliability and validity. The scale may be potentially useful in health-related research and in the training and support of individuals whose work is related to death and dying.

Attitude to Death↗
PubMed1992

Improved performance in a prenatal screening programme for Down's syndrome incorporating serum-free hCG subunit analyses.

A prenatal screening programme for Down's syndrome potentially detecting 76 per cent of affected pregnancies in the South Australian general population at an amniocentesis rate of 3.9 per cent was designed following analysis of mid-trimester serum samples from 57 women who carried an affected fetus. This equates to one affected pregnancy being detected for 41 chromosomal analyses performed. For the experimental series, 75.4 per cent of affected pregnancies were detected, while 4.1 per cent of control specimens produced estimated risk odds consistent with further action. A maternal risk odds of birth of a Down's syndrome fetus of 1:420 was taken as the decision value, which is the prevalence of Down's syndrome births to 35-year-old mothers in South Australia. This screening performance was achieved by investigating combinations of serum analytes not previously reported and by refining the calculation of maternal risk odds to include selective weighting of indicator analytes. Combination of the measurements of free alpha-subunits and beta-subunits of chorionic gonadotrophin, alpha-fetoprotein, unconjugated oestriol, and placental lactogen was found to be most effective in indicating Down's syndrome fetuses. In all combinations of analytes tested, replacing the measurements of free alpha-subunits and free beta-subunits of chorionic gonadotrophin with the measurement of intact chorionic gonadotropin produced a less effective screen.

Adult↗
PubMed1991

Neonatal screening strategy for cystic fibrosis using immunoreactive trypsinogen and direct gene analysis.

OBJECTIVE: To assess the effectiveness of a two tier neonatal screening strategy for cystic fibrosis, which combines estimation of immunoreactive trypsinogen followed by direct gene analysis in dried blood spot samples collected at age 5 days. DESIGN: Prospective study of two tier screening strategy. The first tier of testing immunoreactive trypsinogen concentration was measured in dried blood spot samples from neonates aged 4-5 days. In the second tier direct gene analysis to detect cystic fibrosis mutations deltaF508 and deltaI506 was performed in those blood spot samples which produced the highest 1% of immunoreactive trypsinogen values. Direct gene analysis was also performed on blood spot samples from infants with suspected or confirmed meconium ileus, regardless of the immunoreactive trypsinogen value. SETTING: The South Australian Neonatal Screening Programme, operating from the department of chemical pathology at Adelaide Children's Hospital. Subjects--All 12,056 neonates born in South Australia between December 1989 and June 1990. No selection criteria were applied. INTERVENTIONS: All infants found to have two recognised cystic fibrosis mutations on direct gene analysis were referred directly for clinical management, and those with one recognised cystic fibrosis mutation were recalled for a sweat test; their families were given genetic counselling. MAIN OUTCOME MEASURES: Direct or exclusion of cystic fibrosis by sweat testing of neonates identified as being at high risk of cystic fibrosis on screening and of those at minimum risk but whose subsequent clinical history raised suspicion about the disease. RESULTS: Of the 12,056 infants screened, 11,907 (98.8%) were reported as "cystic fibrosis not indicated" on the basis of low immunoreactive trypsinogen values. Of the 148 (1.23%) infants with raised immunoreactive trypsinogen values and one (0.008%) with meconium ileus, 132 (1.09%) were reported as cystic fibrosis not indicated, four (0.033%) were identified as having cystic fibrosis, and 13 (0.108%) were recalled for sweat testing after direct gene analysis for the presence of the deltaF508 and deltaI506 cystic fibrosis mutations. No cases of affected infants are known to have been missed to date. CONCLUSION: The strategy of measurement of immunoreactive trypsinogen followed by direct gene analysis is a highly specific neonatal screen for cystic fibrosis, requiring only 2.8 families to be contacted for every case of cystic fibrosis diagnosed.

Cystic Fibrosis↗
PubMed1989

Cystic fibrosis: prenatal diagnosis and carrier detection by DNA analysis.

The analysis of restriction fragment length polymorphism (RFLP)s was used to detect 11 polymorphisms that are linked to cystic fibrosis in 42 Australian families with at least one child with cystic fibrosis. The data from all the families were fully informative in regard to the gene for cystic fibrosis (CF). Prenatal assessment was performed for 24 of these families: seven fetuses were assessed to be homozygous for cystic fibrosis, 13 fetuses were heterozygous and three fetuses were free of the CF gene. Of the seven pregnancies in which it was predicted that the infant would be affected by cystic fibrosis, two were continued electively; both have come to term and the infants each were shown to have cystic fibrosis at birth. Of the 17 pregnancies in which it was predicted that the infant would not be affected by cystic fibrosis, 13 have come to term and all the infants but one (who has not yet been followed-up) have been shown to be unaffected by cystic fibrosis at birth. The polymerase chain reaction has been used to amplify the CS.7 and KM.19 loci close to the CF gene. This procedure allows a polymorphic site in each locus to be analysed in a much shorter time (one or two days rather than 10 days) and allows the use of very small test-samples, such as dried blood on filter paper ("Guthrie blood spots"). Our observations confirm the results of overseas studies and indicate that these techniques are eminently useful for prenatal diagnosis and the detection of carriers in the vast majority of Australian families with cystic fibrosis.

Alleles↗
PubMed1989

A child with Refsum's disease: successful treatment with diet and plasma exchange.

A child with Refsum's disease presented with cardiac failure, marked muscle wasting, weakness and inco-ordination. Management with multiple plasma exchanges and dietary restriction of phytanic acid intake has reversed the disabling features of the disease, although levels still remain higher than target values. Low phytanic acid intake is being achieved by restriction of total fat to 10 to 12 g/day, while allowing free amounts of fruit and green vegetables.

Child↗
PubMed1987

Can head injury influence the site of demyelination in adrenoleukodystrophy?

Adrenoleukodystrophy is an inherited disorder, in which there is degeneration of white matter of the central nervous system. The disorder presents classically in males during the first decade, and although early clinical features may be asymmetrical, radiological and pathological features are essentially generalised. Two boys are reported with proven adrenoleukodystrophy, who at first had focal clinical and radiological features, with the foci in the region of local trauma. This raises the possibility that a local insult may have precipitated or hastened the degenerative process.

Adolescent↗
PubMed1986

Microvillar enzymes in amniotic fluid. Considerations for the prenatal diagnosis of cystic fibrosis.

The activity of gamma-glutamyl transpeptidase (GGT) and the proportion of alkaline phosphatase (ALP) activity that remains in cell-free amniotic fluid (AF) after inhibition by amino acids ("residual ALP activity") have been evaluated as possible prenatal diagnostic tests for cystic fibrosis. A total of 1511 AFs were examined. In 1435 "reference" AFs (excluding those from pregnancies with a known fetal abnormality and those with a known one in four risk of cystic fibrosis) at 14-24 weeks' gestation, the mean residual ALP activity in the presence of 2.5 mmol/L L-phenylalanine was 32% (median, 28%) and in 10.0 mmol/L L-homoarginine it was 70% (median, 72%). AFs were arbitrarily considered to be "abnormal" if the residual activity was greater than 50% in L-phenylalanine and less than 50% in L-homoarginine. An abnormal residual ALP activity pattern was found in nine of 27 pregnancies which resulted in a neural tube (or other developmental) defect and in five of the 10 pregnancies with a chromosomal abnormality; a further 23 (1.6%) abnormal patterns occurred in the 1435 reference AFs from pregnancies that were believed to have had a normal outcome. However, of an additional 23 AFs that were sampled at the 25th week of pregnancy or later, 13 had an abnormal residual activity pattern; the outcome at term in each case was normal. The residual activity of ALP in the presence of either inhibitor did not change with increasing gestational age. However, the absolute amount of ALP that was inhibited by L-phenylalanine (the so-called "phe-inhibitable activity") was greatest at 18 weeks. GGT activity decreased with increasing length of gestation. Of the AF samples from 16 pregnancies at one in four risk for cystic fibrosis that were obtained at 18 weeks' gestation, 11 AFs had a normal residual ALP activity pattern, normal GGT and normal phe-inhibitable ALP activity. Of these 11, five have come to term and the infants are not affected by cystic fibrosis. Three of the 16 AFs had an abnormal residual ALP activity pattern, low GGT and low phe-inhibitable ALP activity; these pregnancies were assessed to be affected by cystic fibrosis and termination was chosen in each case. The two remaining AFs had borderline, paradoxical GGT and residual ALP activity, and initially could not be classified clearly into either of the two groups; however, phe-inhibitable ALP activity was low in each. These pregnancies are continuing.

Alkaline Phosphatase↗
PubMed1985

Infantile Refsum's disease: a peroxisomal storage disorder?

An 18-month-old infant presented with a history of arrest of neurological development from the age of eight months, with progressive ataxia, deafness, retinitis pigmentosa and hepatomegaly. Biochemical investigations revealed an elevated plasma phytanic acid level and deficiency of phytanic acid oxidase in skin fibroblasts. Histopathological findings in a liver biopsy were similar to those reported in infantile phytanic acid storage disease. Unexpected findings were the presence of elevated levels of plasma pipecolic acid, and elevated plasma long-chain fatty acid ratios, biochemical findings previously considered to be diagnostic of Zellweger's hepato-cerebro-renal syndrome, and of adrenoleucodystrophy, respectively. Recent biochemical evidence suggests that this patient, and other similar cases that have recently come to our attention, may have a fundamental defect in the peroxisomal enzyme system.

Age Factors↗
PubMed1985

Phytanic acid oxidase deficiency in childhood.

Tables 2 and 5 summarize the major clinical and biochemical findings in these patients. Cases 1 and 2 resemble clinically the previous cases of children reported as suffering from infantile phytanic acid storage disease, Zellweger's disease, or neonatal adrenoleucodystrophy. Cases 3 and 4 differ strikingly from these and from one another. Numerous questions remain unanswered, but it seems likely that these patients have in common defects in peroxisomal function which are related but not identical. Why some patients with phytanic acid oxidase deficiency do not have significant elevation of serum phytanic acid is not known. These results, however, make it clear that a normal serum phytanic acid level does not exclude phytanic acid oxidase deficiency. In children with a progressive neurological illness, with liver disease, retinal disease, unexplained neuropathy or deafness, detailed studies of fatty acid metabolism are indicated, including lipoproteins, serum phytanic acid, C26:C22 long-chain fatty acid ratios, serum pipecolic acid and phytanic acid oxidase levels. Electron microscopy of liver biopsy specimens should be considered. Phytanic acid oxidase may prove a useful marker for some of these illnesses, and its usefulness could extend to prenatal diagnosis and assist in genetic counselling.

Abnormalities, Multiple↗
PubMed1984

Prenatal diagnosis of lysosomal storage diseases. Review of experience in 145 patient referrals over a period of eight years.

Over the past eight years, 145 patients from Australia and New Zealand were referred to the Department of Chemical Pathology, The Adelaide Children's Hospital, for the prenatal assessment of a variety of lysosomal storage diseases. This group comprised 65 patients at risk for a glycosphingolipidosis, 50 for a mucopolysaccharidosis, five for mucolipidosis, 15 for glycogen storage disease, and 10 for cystinosis. In three cases, amniotic cells failed to establish in culture; in one of these cases, cell-free amniotic fluid was used to make the prenatal diagnosis; the fetus spontaneously aborted in another; only in one case could the prenatal assessment not be completed. Of the 143 cases of successful assessment, 40 fetuses (28%) were predicted to be homozygous affected by the disease for which they were at risk, and 38 pregnancies were subsequently terminated. Follow-up biochemical tests in the affected fetuses and in the newborn children were performed in 82% of cases and confirmed the prenatal assessment to have been correct in all cases. There were no known false positive or false negative diagnoses. It is concluded that the prenatal diagnosis of a range of lysosomal storage diseases can be performed accurately and reliably, provided that cultured amniotic cells are used for enzymatic assay and that a strict protocol, related to each individual prenatal assessment, is followed.

Amniocentesis↗
PubMed1984

Patterns of Refsum's disease. Phytanic acid oxidase deficiency.

Four children each exhibiting a profound deficiency of phytanic acid oxidase activity in cultured skin fibroblasts but with very different phenotypes, are described. A consistently raised plasma phytanic acid value, generally considered to be pathognomonic for Refsum's disease (phytanic acid oxidase deficiency), was observed in three of these children but not in the fourth, who also showed no evidence of accumulation of phytanic acid in liver or fat biopsies. Our data suggest that the clinical diagnosis of Refsum's disease in children is more difficult because the full spectrum of clinical features usually observed in adults with the disorder is not always present. Moreover, a failure to detect a raised plasma phytanic acid value may not necessarily indicate normal fibroblast phytanic acid oxidase activity.

Adult↗
PubMed1983

Adrenomyeloneuropathy--clinical and biochemical diagnosis.

Adrenomyeloneuropathy (AMN) is an X-linked storage disease of very-long-chain fatty acids that presents as primary adrenocortical failure combined with spastic paraparesis and peripheral neuropathy. This disorder was diagnosed in three unrelated adult males. Definitive diagnosis was made by finding elevated very-long-chain fatty acids in plasma and skin biopsy samples. Biochemical characterisation of this disease has elucidated its genetics, clarified its relationship with adrenoleukodystrophy of children and other phenotypic variants, and allowed heterozygote identification, accurate genetic counselling and prenatal diagnosis.

Addison Disease↗
PubMed1982

Micro-determination of clonazepam in plasma or serum by electron-capture gas-liquid chromatography.

A rapid method is described for the electron-capture gas chromatographic determination of clonazepam in plasma or serum using methyl-clonazepam as an internal standard. The analysis is performed isothermally on the silicone stationary phase SP-2510DA (Supelco). With this liquid phase, gas chromatographic properties are comparable to methods involving acid hydrolysis or derivatisation. A short pre-column containing another phase is added to enhance resolution. The method involves a single extraction, requires 100 microliter of sample and has a detection limit of 3 nmol/l. Response is linear at concentrations from 5--900 nmol/l and thus clonazepam analysis both during therapy and after overdosage is possible. Plasma and serum clonazepam levels are interchangeable.

Benzodiazepinones↗