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Browsing Physiology publications by Author "Adams, Michael Brenton"
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Item Metadata only Actions of hypoxia on catecholamine synthetic enzyme mRNA expression before and after development of adrenal innervation in the sheep fetus(CAMBRIDGE UNIV PRESS, 2000) Adams, Michael Brenton; McMillen, Isabella CarolineItem Metadata only Catecholamines, enkephalins and the response of the fetal adrenal to hypoxaemia(1997) McMillen, Isabella Caroline; Simonetta, Giuseppe; Roberts, Michael Lawrence; Adams, Michael BrentonItem Metadata only Differential effects of increasing gestational age and placental restriction on tyrosine hydroxylase, phenylethanolamine N-methyltransferase, and proenkephalin A mRNA levels in the fetal sheep adrenal(1998) Adams, Michael Brenton; Phillips, Ian D.; Simonetta, G.; McMillen, Isabella CarolineWe have demonstrated that there are differential changes in the levels of tyrosine hydroxylase (TH), phenylethanolamine N-methyltransferase (PNMT), and proenkephalin A (Pro Enk A) mRNA in the fetal sheep adrenal during late gestation. Adrenal TH mRNA:18S rRNA ratios increased between gestational days 100 (0.98 ± 0.13; n = 6) and 125 (1.40 ± 0.15; n = 6) and then decreased, whereas adrenal PNMT mRNA:18S rRNA ratios increased regularly between gestational days 100 (0.08 ± 0.01) and 146 (0.17 ± 0.03). The ratio of adrenal Pro Enk A mRNA to 18S rRNA was higher at gestational day 125 (0.085 ± 0.005) than at either 80–100 days (0.038 ± 0.007) or 140–146 days of gestation (0.055 ± 0.013). In 12 ewes, the growth and development of the placenta were restricted (placental restriction group) from conception. The ratio of adrenal PNMT mRNA to 18S rRNA was significantly reduced in the placental restriction group of fetal sheep (0.003 ± 0.002) compared with controls (0.011 ± 0.002), and there was a significant correlation between the ratio of adrenal PNMT mRNA to 18S rRNA and the mean arterial Po2 (r = 0.88, p < 0.0005). In contrast, TH mRNA and Pro Enk mRNA were unaffected by placental restriction. Adrenaline and nonadrenaline syntheses are therefore differentially regulated in the adrenal during late gestation and in response to chronic intrauterine hypoxemia.Item Metadata only The non-neurogenic catecholamine response of the fetal adrenal to hypoxia is dependent on activation of voltage sensitive Ca2+ channels(1996) Adams, Michael Brenton; Simonetta, Giuseppe; McMillen, Isabella CarolineItem Metadata only Oxygen-sensing mechanisms are present in the chromaffin cells of the sheep adrenal medulla before birth(1998) Rychkov, Grigori; Adams, Michael Brenton; McMillen, Isabella Caroline; Roberts, Michael LawrenceItem Metadata only Tyrosine hydroxylase protein content in the medulla oblongata of the foetal sheep brain increases in response to acute but not chronic hypoxia(Elsevier, 2001) Adams, Michael Brenton; Brown, R. E.; Gibson, Catherine Sue; Coulter, Catherine Louise; McMillen, Isabella Caroline; School of Molecular and Biomedical Science : PhysiologyWe have investigated the effect of lowering foetal arterial PO2 either acutely or chronically on tyrosine hydroxylase (TH) protein content in the dorsal and ventral medullary regions of the brainstem of the sheep foetus during late gestation. TH protein content increased in both the dorsal and ventral medullary regions of the foetal brainstem after exposure to acute hypoxia when compared to normoxia. In contrast there was no increase in the TH protein content of either the dorsal or ventral medullary regions in the brainstem of foetal sheep which were chronically hypoxaemic throughout late gestation as a consequence of experimental restriction of placental growth. The differences between the TH responses to acute and chronic hypoxaemia in the foetal sheep brainstem may be important in the mediation of physiological adaptations to these intrauterine stimuli and for the generation of an appropriate physiological response to hypoxia in the newborn period.