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Biomedical subjects

R Thom

Publications and source records attributed to R Thom.

At least 19 recordsLinked to original sources
PubMed2003

Predicting iron status in low birthweight infants.

OBJECTIVE: To determine the iron status of a selected group of low birthweight infants at approximately 9 months of age, and examine the feasibility of predicting iron status by examining the history of supplementary iron intake. METHODS: All live low birthweight infants recorded in the Dunedin Hospital Queen Mary Maternity Unit birth register who reached 9 months of age between November 1995 and September 1996 were eligible to participate. Infants were categorized into 'high' or 'low' iron intake groups depending on their consumption of infant formula or medicinal iron for one month prior to the study, and their iron status compared. RESULTS: Eighty-one infants of 73 mothers, with an average age of 10 months (range 8-13 months), participated. Thirty-three per cent (n = 27) were iron deficient: 19% (n = 15) had latent iron deficiency and 15% (n = 12) had iron deficiency anaemia. Those with a 'low' iron intake were 13-fold more likely to be iron deficient than infants with a 'high' iron intake (95% confidence interval: 4.4-41.5). Screening for iron deficiency using categories based on supplementary iron intake had a positive predictive value of 66% and a negative predictive value of 88%. CONCLUSIONS: The risk of iron deficiency was considerably greater for infants who had not received supplementary iron daily over the course of the previous month. Current preventative methods for avoiding poor iron status in this group of high risk infants are not effective. Screening for iron deficiency in low birthweight infants on the basis of iron intake from infant formula or medicinal iron provides a useful method for identifying infants whose iron status should be investigated.

Anemia, Iron-Deficiency↗
PubMed2002

Hyperbaric oxygen and neutrophil accumulation/tissue damage during permanent focal cerebral ischaemia in rats.

The use of hyperbaric oxygenation (HBO) for the treatment of severe brain ischaemia remains controversial. The HBO may interfere with destructive neutrophil (PMN) infiltration following ischaemia/reperfusion. The effects of HBO on PMN accumulation and the area of ischaemic tissue damage were investigated in rats having permanent focal ischaemia (4 h). The right middle cerebral arteries of a group of Wistar rats were permanently occluded. The rats were then randomly divided into those ( n=7) to be treated with HBO at 2 atm for 230 min and those ( n=8) to breathe air at atmospheric pressure for an equivalent period. The HBO had no effect on permanent ischaemia, as there was no significant difference in the area of ischaemic tissue damage between HBO-treated [mean (SD)] [331 (88) mm(3)] and non-treated animals [322 (111) mm(3)]. Moreover, the increase in myeloperoxidase [5.4 (4.1) compared to 2.4 (1.2) pg x g(-1) wet weight of brain] was not significantly different. The results indicate that HBO did not reduce tissue damage during 4 h of permanent focal ischaemia.

Animals↗
PubMed2001

The structure of a zeta class glutathione S-transferase from Arabidopsis thaliana: characterisation of a GST with novel active-site architecture and a putative role in tyrosine catabolism.

The cis-trans isomerisation of maleylacetoacetate to fumarylacetoacetate is the penultimate step in the tyrosine/phenylalanine catabolic pathway and has recently been shown to be catalysed by glutathione S-transferase enzymes belonging to the zeta class. Given this primary metabolic role it is unsurprising that zeta class glutathione S-transferases are well conserved over a considerable period of evolution, being found in vertebrates, plants, insects and fungi. The structure of this glutathione S-transferase, cloned from Arabidopsis thaliana, has been solved by single isomorphous replacement with anomalous scattering and refined to a final crystallographic R-factor of 19.6% using data from 25.0 A to 1.65 A. The zeta class enzyme adopts the canonical glutathione S-transferase fold and forms a homodimer with each subunit consisting of 221 residues. In agreement with structures of glutathione S-transferases from the theta and phi classes, a serine residue (Ser17) is present in the active site, at a position that would allow it to stabilise the thiolate anion of glutathione. Site-directed mutagenesis of this residue confirms its importance in catalysis. In addition, the role of a highly conserved cysteine residue (Cys19) present in the active site of the zeta class glutathione S-transferase enzymes is discussed.

Amino Acid Sequence↗
PubMed2000

Effect of genotype on changes in intelligence quotient after dietary relaxation in phenylketonuria and hyperphenylalaninaemia.

BACKGROUND: Associations between genotype and intellectual outcome in patients with phenylketonuria are complicated because intelligence is influenced by many variables, including environmental factors and other genetic determinants. Intellectual changes with age, both on and after relaxation of diet, vary within the patient population. This study aims to determine whether a significant association exists between genotype and change in intelligence after relaxation of diet. METHODS: 125 patients with hyperphenylalaninaemia and phenylketonuria whose diet was relaxed after 8 years of age. Verbal, performance, and full scale intelligence quotients at 8, 14, and 18 years were expressed as standard deviation scores (IQ-SDS), and genotype as predicted residual enzyme activity (PRA) of phenylalanine hydroxylase. RESULTS: IQ-SDS at 8, 14, and 18 years were significantly below normal; no association was found between PRA and IQ-SDS. Significant reductions in verbal and full scale IQ-SDS occurred between 8 and 14 years and 8 and 18 years. There was a significant association between PRA and the reduction in verbal, performance, and full scale IQ between these years. Multiple regression analysis of 18 year results, using 8 year results as covariates, supported the association between PRA and IQ-SDS; after adjustment for phenylalanine control, both up to and after the age of 8 years, the full scale IQ-SDS at 14 and 18 years was 0.15 higher for each 10% increase in PRA. CONCLUSIONS: Genotype might be useful in predicting the likelihood of intellectual change in patients with hyperphenylalaninaemia and phenylketonuria whose diet is relaxed after the age of 8 years.

Adolescent↗
PubMed1999

Upregulation of connexin 26 is a feature of keratinocyte differentiation in hyperproliferative epidermis, vaginal epithelium, and buccal epithelium.

In epidermis, it has been suggested, intercellular communication through gap junctions is important in coordinating cell behavior. The connexins, may facilitate selective assembly or permeability of gap junctions, influencing the distribution of metabolites between cells. Using immunohistochemistry, we have compared the distribution of connexins 26 and 43 with that of proliferating cells (Ki67 labeling) in normal epidermis, hyperplastic epidermis (tape-stripped epidermis, psoriatic lesions, and viral warts), and vaginal and buccal epithelia. Connexin 43 was abundant in spinous layers of all epidermal specimens and in vaginal and buccal epithelia. Connexin 26 was absent from the interfollicular and interductal epidermis of normal hair-bearing skin, and nonlesional psoriatic epidermis but present at very low levels in plantar epidermis. Connexin 26 was prominent in lesional psoriatic epidermis and viral warts and in vaginal and buccal epithelia. In three independent experiments connexin 26 appeared in a patchy intercellular distribution in the basal epidermis within 24 h of tape stripping, proceeding to more extensive distribution in basal and suprabasal layers by 48 h. The increase in connexin 26 preceded that in cell proliferation. In vaginal epithelium, buccal epithelium, and viral warts connexin 26 was restricted mainly to suprabasal, nonproliferating cells. In psoriatic lesional epidermis connexin 26 was also located mainly in suprabasal, nonproliferating cells. Connexin 26 was present in a patchy distribution in the basal layer of psoriatic lesional epidermis, but double labeling for connexin 26 and Ki67 showed that many connexin 26 positive basal cells were nonproliferative, suggesting that connexin 26 may be related to differentiation rather than to proliferation. These observations would be consistent with a role for connexin 26 containing gap junctions during both early and later stages of keratinocyte differentiation in hyperplastic epidermis and in vaginal and buccal epithelia.

Cell Differentiation↗
PubMed1990

Surrogate materials for calibration and control: the use of latex particles as calibrants for red cell volume measurements.

Latex particles, including BCR Certified Reference Material CRM 166a, have important applications for checking linearity and for calibrating aperture-impedance instruments used to determine red-cell volumes. Studies performed on Coulter Counters, e.g. the ZBi/C1000, ZM/C256 and Model S Plus IV, using a series of three different mono-sized latex particles have shown linearity but non-zero intercepts. This emphasizes the importance of calibrating instruments at more than one point. Latex particles also have an important role in calibration of red-cell volume measurements provided that a relative latex: red-cell shape factor has been assigned when the instrument is calibrated with fresh blood. Such relative shape factors are independent of latex particle size but need to be specific for instrument type and probably also for the orifice and diluent to be used. Nevertheless latex calibrants can serve an important role in standardizing red-cell volume measurements.

Calibration↗
PubMed1985

Parents' understanding of coeliac disease and diet.

Parents of 50 children with coeliac disease were questioned about their knowledge of the disorder and the child's dietary compliance. Twenty of 50 parents admitted that compliance was less than strict. This correlated with poor knowledge of the disease which in turn was related to the family's social status. Membership of the Coeliac Society (23 of 50) correlated with both parental understanding and dietary compliance. Greater emphasis on dietary compliance and education of parents and patients is required.

Adolescent↗
PubMed1984

Protocol for evaluation of automated blood cell counters. International Committee for Standardization in Haematology (ICSH).

This protocol is proposed for the evaluation of automated blood cell counters to assess the performance, advantages and limitations of such instruments. It is based on the International Committee for Standardization in Haematology (ICSH) 'Protocol for type testing equipment and apparatus used for haematological analysis' (1978a) and the British Committee for Standardization in Haematology 'Guidelines for the evaluation of instruments used in haematology' (Shinton, England & Kennedy, 1982). The document has been prepared by the ICSH Panel on Cytometry after discussion with colleagues. This tentative protocol will be reviewed 1 year after publication, in accordance with the ICSH rules, before it is adopted as a definitive standard.

Blood Cell Count↗
PubMed1976

Cystic fibrosis: normal volumes of red cells. Model experiments on the pathomechanism of the disease.

Normal values of mean cell volume (M.C.V.) and of distribution of single cell volumes (S.C.V.) have been observed in erythrocytes of patients with cystic fibrosis using an electronical particle-volume analyzer (sheath flow detector). From these results a strong defect in red cell salt transport seems improbable. Valinomucin induces shrinking (by increase of K+ permeability) and gramicidin D induces swelling (by increase of Na+ permeability) of normal erythrocytes. Addition of C.F. sweat to normal erythrocytes induces no volume change. From this result no influence of the "C.F. factor" on passive ion permeability is concluded.

Cystic Fibrosis↗