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Biomedical subjects

A C Pollard

Publications and source records attributed to A C Pollard.

At least 37 records · Page 2Linked to original sources
PubMed1982

Enzymatic diagnosis of the mucopolysaccharidoses: experience of 96 cases diagnosed in a five-year period.

We assessed lysosomal exohydrolase activities in homogenates of cultured skin fibroblasts and peripheral blood leucocytes of approximately 550 patients referred from throughout Australasia and suspected of having a mucopolysaccharidosis. Of these, 96 patients from 80 families were diagnosed as being homozygous deficient for a particular lysosomal enzyme activity. Clinical phenotype varied considerably within each of the enzyme-deficient states. This did not correlate with the level of "residual" enzyme activity in leucocyte or fibroblast homogenates. It was not always possible to discriminate heterozygotes from normal controls by enzyme assay of leucocyte or fibroblast homogenates in this study of a large number of mucopolysaccharidoses Type II by means of a single hair root assay system.

Clinical Enzyme Tests↗
PubMed1982

Hepatic storage of bis(monoacylglycerol) phosphate without concomitant storage of sphingomyelin in a 72-year-old patient with a partial deficiency of sphingomyelinase.

A 72-year-old patient with marked splenomegaly and low sphingomyelinase (6% of lowest control value) in peripheral blood leukocytes is described. Much higher but variable residual sphingomyelinase activity was observed in cultured skin fibroblasts (40-67% of lowest control value); reduced activity was also found in a liver biopsy sample. Excess storage of sphingomyelin was not observed in a liver biopsy; instead, a lipid tentatively identified as bis(monoacylglycerol) phosphate was present in amounts at least 20 times greater than in age-matched control livers. The biochemical relationship of this patient to patients with sphingomyelin storage disease (Niemann-Pick disease) and phospholipidosis Type II is discussed.

Aged↗
PubMed1981

Combined analysis of acetylcholinesterase and alpha-fetoprotein improves the accuracy of antenatal diagnosis of neural-tube defects.

Acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and alpha-fetoprotein (AFP) were measured in 293 amniotic fluids from the second and third trimesters of pregnancy in a prospective study of their diagnostic value in the detection of neural-tube defects (NTD). In normal samples, the mean AChE and BChE concentrations were 3.0 u/L (SEM = 9.1 u/L) and 15.2 u/L (SEM = 1.2 u/L) in the second trimester, and 1.6 u/L (SEM = 0.1 u/L) and 7.8 u/L (SEM = 0.6 u/L) in the third trimester. AFP levels fell throughout the second trimester to unmeasurable levels in the third. AChE levels were markedly elevated in samples from NTD pregnancies at all gestational ages, and a cut-off level of the mean + 3 SD optimally separated normal from abnormal samples. This cut-off correctly predicted 10 of 11 fetuses with neural lesions; there were three false positive results. A similar cut-off for AFP predicted nine of 11 cases of neural lesion with two false positive results. For BChE, a cut off of 50 u/L predicted eight of 11 neural lesions with two false positive results. The specificity, sensitivity, and predictive value positive (PVP) were calculated for each test. The assays of AFP and AChE were useful when used individually (PVP congruent to 80%), but a Bayesian combination of these two tests produced a superior PVP (98%). Because the cost of AChE assay is low, and the test is so simple, it is suggested that an AChE analysis should be performed whenever an amniocentesis is requested for the diagnosis of NTD.

Acetylcholinesterase↗
PubMed1980

Enzymological diagnosis of a group of lysosomal storage diseases. Review of 5-year experience of 1600 patient-sample referrals.

Lysosomal acid hydrolase activities have been measured in extracts of peripheral blood leucocytes of approximately 1600 patients referred from throughout Australia, each of whom was suspected of having a neurolipidosis. Assays for 12 different lysosomal enzymes were performed on each patient as a routine; ten assay systems were based on commercially available substrates, and four used radiolabelled glycosphingolipids prepared in our own laboratory. Of the 85 patients with positive results, 81 were diagnosed as being homozygous-deficient for a particular lysosomal enzyme. These patients comprised nine with GM1-gangliosidosis, 12 with GM2-gangliosidosis (11 of Tay-Sachs' disease and one of Sandhoff's disease), 18 with trihexosylceramide lipidosis (Fabry's disease), eight with beta-galactosylceramide lipidosis (Krabbe's disease), 14 with beta-glucosylceramide lipidosis (Gaucher's disease), two with sphingomyelin lipidosis (Niemann-Pick disease), 13 with metachromatic leucodystrophy and five with alpha-mannosidosis. In addition, four patients were diagnosed as being affected with mucolipidosis Type II (I-cell disease), based on elevated plasma lysosomal enzyme activities, making a total of 85 homozygous-affected patients. Clinically the patients showed wide phenotypic variability within each of the enzyme-deficient states, which did not appear to correlate with the level of "residual" enzyme activity in their leucocyte extracts.

Clinical Enzyme Tests↗
PubMed1980

The magnesium content of duodenal mucosa in man.

The magnesium content of duodenal mucosa was estimated in biopsy specimens from 50 patients, 43 of which had normal mucosal histopathology. There was no significant difference in the mean mucosal magnesium content of those speciments with normal and abnormal histopathology and overall the mean value was 30.9 mmol/kg dry weight of tissue, but there was a wide spread of values. The concentration of magnesium in plasma and duodenal fluid was also determined. There was no significant correlation between duodenal mucosal magnesium content and plasma magnesium concentration. However, there was a weak but statistically significant correlation between magnesium content in duodenal fluid and duodenal mucosa (r = 0.54, p less than 0.001).

Adolescent↗
PubMed1980

The effect of the interdependence of protein and bile salt concentrations on the measurement of cerebroside sulphate sulphatase activity in human leucocyte and fibroblast extracts.

The previously observed differences in properties of human leucocyte and fibroblast cerebroside sulphate sulphatase (cerebroside-3-sulphate 3-sulphohydrolase, EC 3.1.6.8) measured in vitro have been found to be due to subtle differences in incubation conditions. Maximum enzyme activity was observed with either crude sodium taurocholate or with pure sodium taurodeoxycholate. The optimum bile salt concentration of the enzyme in leucocyte or fibroblast extracts, but not the pure ox liver enzyme, was critically dependent on protein concentration. At low concentrations of the latter (less than 0.1 mg/ml), maximum activity was observed at taurocholate concentrations less than 0.5 mg/ml; at protein concentrations greater than 0.20 mg/ml substantially more bile acid (more than 1.3 mg/ml) was required to stimulate maximum activity. Addition of Triton X-100 or bovine serum albumin to the incubation mixtures increased the optimum taurocholate concentration. The dependence of the bile salt optimum on protein concentration appears to be related to the binding of the lipid substrate to membranous protein present in the tissue extracts. Release of the bound lipid is effected either by increasing the bile salt concentration or by adding Triton X-100. In the presence of excess bile salt human leucocyte, fibroblast and liver cerebroside sulphate sulphatase activity is stimulated by Triton at low protein concentrations; under identical conditions the pure or crude ox-liver enzyme is substatially inhibited. Our data also show that cerebroside sulphate sulphatase activity measured in extracts from leucocytes and fibroblasts, the tissues normally used to effect a diagnosis of metachromatic leucodystrophy, is the result of a complex interaction of bile salt, protein, Triton X-100 and probably the substrate itself. Any slight alteration in any of those factors, without a corresponding change in any or all of the others, can have a marked effect on the measured enzyme activity, and may lead to errors in the diagnosis of metachromatic leucodystrophy.

Animals↗
PubMed1979

Evaluation of a state-wide neonatal screening programme.

A screening programme which was already established to detect phenylketonuria in the newborn period in South Australia was extended to include screening for galactosaemia, homocystinuria, hereditary tyrosinaemia, histidinaemia, maple syrup urine disease and severe alpha 1-antitrypsin deficiency for a trial period. Later, screening for hypothyroidism was introduced. Results suggest that screening for galactosaemia and hypothyroidism are useful additions to the programme. Screening for trrosinaemia and alpha 1-antitrypsin deficiency produced a high number of requests for repeat samples, causing anxiety and no positive benefit to patients. Homocystinuria, an eminently treatable condition, was not detected, nor was maple syrup urine disease, a much less readily treatable condition. Histidinaemia was detected only once. Screening for tyrosinaemia, alpha 1-antitrypsin deficiency, maple syrup urine disease and histidinaemia has been discontinued. Newborn screening in South Australia currently includes tests for phenylketonuria, hypothydroidism, galactosaemia and homocystinuria.

Amino Acid Metabolism, Inborn Errors↗
PubMed1979

Acetylcholinesterase in human amniotic fluid: An index of fetal neural development?

Acetylcholinesterase (AChE) activity was detected in amniotic fluid either sampled by amniocentesis at 14--23 weeks gestation or collected at normal parturition. Activity ranged from 0.2 to 8.9 u/l in the earlier samples and from 0.2 to 4.2 u/l in the later samples. Since the fetal but not the maternal serum contained AChE activity, we suggest that the AChE in the amniotic fluid is derived from the fetus. AChE is released from both neural and nonneural tissues, and the release of the enzyme from both sources may diminish as the nervous system matures. The amount of AChE found in amniotic fluid may be affected by abnormalities of the nervous system. Amniotic fluid from two fetuses with spina bifida contained AChE activity: one, with a gestational age of 21 weeks, was in the upper levels of the normal range (4.5 u/l), whereas the other, at 36 weeks, contained 1.9 times more activity than the next highest sample. In a 20-week fetus with anencephaly, the AChE activity in the amniotic fluid was increased 2.8-fold over the activity of the highest "normal" sample.

Acetylcholinesterase↗
PubMed1979

A rapid ultraviolet spectrophotometric procedure for the microdetermination of theophylline (1,3-dimethylxanthine) in plasma or serum.

An ultraviolet spectrophotometric procedure for the microdetermination of theophylline in plasma is described. Theophylline is extracted at pH 5 with chloroform. An aliquot of the solvent is shaken with molar hydrochloric acid and the absorbance of the acid layer determined at 267 nm. The resulting procedure is rapid, reliable, sensitive and virtually specific. It requires 250 microliters sample for a single estimation and has a detection threshold of less than 5 mumol/l.

Evaluation Studies as Topic↗
PubMed1978

Successful restoration of immunity in the DiGeorge syndrome with fetal thymic epithelial transplant.

A 13-month-old girl presented with right upper lobe pneumonia and hypocalcaemic seizures: investigations showed hypoparathyroidism and impaired cell-mediated immune responses. Other features of the DiGeorge syndrome included hypertelorism, short philtrum of the lip, right-sided aortic arch, and aberrant origin of the left subclavian artery. Successful restoration of the immunodeficiency was achieved by transplantation of fetal thymic epithelium.

DiGeorge Syndrome↗
PubMed1978

Gas--liquid chromatographic microdetermination of underivatized ethosuximide (alpha-ethyl-alpha-methyl succinimide) in plasma or serum.

A gas-liquid chromatographic procedure for the microdetermination of ethosuximide is described. Ethosuximide is extracted from acidified plasma or serum into chloroform containing an internal standard alpha,alpha-dimethyl-beta-methyl succinimide. Part of the initial chloroform extract is gently evaporated, the residue redissolved in n-heptane at 60 degrees C, and an aliquot analyzed by gas-liquid chromatography. The procedure is rapid, reliable, sensitive, and specific. It requires a 25--50 microliter sample for a single estimation, has a detection threshold of less than 10 micromol/liter, and is suitable for routine clinical use.

Chromatography, Gas↗