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G Huxham

Publications and source records attributed to G Huxham.

5 recordsLinked to original sources
PubMed1999

UTP-preferring P2 receptor mediates inhibition of sodium transport in porcine thyroid epithelial cells.

1. The effects of adenosine 5'-triphosphate (ATP), uridine 5'-triphosphate (UTP) and analogues on forskolin-stimulated absorption of Na+ by porcine thyroid epithelial cells were analysed in cultures grown as confluent monolayers on permeable supports in Transwell Ussing chambers. 2. 85% of the forskolin (10 microM)-stimulated short-circuit current was inhibited by phenamil (1 microM), which is a selective antagonist for epithelial type Na+ channels. 3. Phenamil-sensitive current was inhibited in a dose dependent manner by nucleotides added to the apical compartment of Ussing chambers. In contrast, the phenamil-resistant current, previously shown to represent anion secretion, was unaffected by nucleotides. 4. The order of potency (with EC50 values given in microM) was UTP (0.08)>>ATP (6.3)=uridine 5'-diphosphate (UDP) (6. 6)>2methyl-thio-adenosine-5'-triphosphate (2MeSATP) (84.5)>adenosine 5'-diphosphate (ADP) (147.8)>alpha,beta-methylene ATP (>150)>>adenosine (>1000). 5. P2 receptors mediating inhibition of sodium absorption were present on the apical membrane of the cells since addition of UTP (1-1000 microM) to the basal compartment of the Ussing chambers had little effect while subsequent addition to the apical compartment produced a normal response. 6. Cibachron blue (Reactive blue 2) (1-100 microM), an antagonist at some P2 receptor subtypes, inhibited phenamil sensitive current in a dose dependent manner with half maximal inhibition occurring at 14.25 microM. 7. Suramin (100 microM), pyridoxalphosphate-6-azophenyl-2', 4'-disulphonic acid (PPADS) (100 microM) and pyridoxal 5'-phosphate (P5P) (100 microM) showed only slight competitive antagonism against the response to UTP. 8 These results indicate that a UTP-preferring P2 receptor located on the apical membrane of thyroid epithelial cells mediates inhibition of Na+ absorption.

Animals↗
PubMed1988

School results as predictors of medical school achievement.

In Queensland, scores in the final 2 years of secondary school scaled by an independent aptitude test are used to determine admission to tertiary education. The validity of this procedure for medical school enrollment has been investigated. Data were from four cohorts which entered the medical school to commence the course in each of the years 1975-1978, a total of 943 students. In addition to the school subject scores, overall order of merit scores and results of an independent aptitude test used to scale these scores were included with the predictors. Criteria were derived from the grades obtained in the 33 medical school subjects over the 6-year course, or from a broad pass/fail classification. We demonstrate that the school science subjects were of moderate value for prediction of preclinical achievement, but that school English was the most important predictor of performance in the clinical years, which is perhaps an indication of the value of communication skills.

Achievement↗
PubMed1984

Metabolic dependence of glycolytic enzyme binding in rat and sheep heart.

Perfused rat hearts show a markedly increased binding of phosphofructokinase and fructose-bisphosphate aldolase as a consequence of ischaemia, but little change in binding of pyruvate kinase, lactate dehydrogenase or glyceraldehyde-3-phosphate dehydrogenase. After 10 min ischaemia over one quarter of the phosphofructokinase and three quarters of the aldolase are bound. The effect of anoxia is less well marked in its influence on binding with only aldolase showing a significant increase in binding. These results suggest that one factor involved in the increased binding during ischaemia is the fall in pH of the heart. Binding studies with isolated myofibrils confirm that the affinity and stoichiometry of aldolase binding are considerably increased as the pH is lowered over a range comparable to that which occurs in ischaemic heart. The low level of binding of glyceraldehyde-3-phosphate dehydrogenase in perfused rat hearts correlates with the relatively low affinity of this enzyme for binding to rat or rabbit cardiac myofibrils. There are species differences in the enzyme binding response to ischaemia. Sheep hearts show rapid and large increases in the binding of glyceraldehyde-3-phosphate dehydrogenase in addition to changes in aldolase and phosphofructokinase binding. The greater binding of glyceraldehyde-3-phosphate dehydrogenase reflects the greater affinity of sheep cardiac myofibrils. It is suggested that the altered metabolic demands of ischaemia are satisfied by changes in glycolytic enzyme organisation as the enzymes shift from the soluble to the particulate phase of cardiac muscle.

Animals↗
PubMed1980

Criterion-based open book examinations in physiology.

Analysed data from ten consecutive physiology examinations for medical students at Aarhus University are presented. Each examination comprised one MCQ test and one short-answer test. For both written aids were allowed; both were dominated by items above the recall level. The mean test scores of both the MCQ and the short answer tests were slightly above their mean pass levels with coefficients of variation around seven. Large but similar pass rate fluctuations in both test were found, and about half of the non-passing students failed both tests. The MCQ minimum pass level, established by the Nedelsky principle, was more stable than the essay pass level. The Nedelsky values seem to compensate for a large part of the fluctuations in the difficulty level of various MCQ sets. Due to lack of comparable data it cannot be settled whether the pass rate fluctuations are excessive, nor whether standards fluctuate more than those at other institutes.

Denmark↗