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1,131 results on '"Simpson, R. J."'

212. Problems: 10410-10416

Author

Schmidt, Frank, primary, Sinnamon, Gord, additional, Darling, Donald A., additional, Mocanu, Mirel, additional, Simpson, R. J., additional, Smyth, W. F., additional, Kitchen, Edward, additional, and Chen, Kwang-Wu, additional

Published
1994
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245. Immunolocalization of duodenal cytochrome B: a relationship with circulating markers of iron status.

Author

Li, A. C. Y., Warley, A., Thoree, V., Simpson, R. J., Mckie, A. T., Kodjabashia, K., Thompson, R. P. H., and Powell, J. J.

Subjects
CYTOCHROME b, IRON, FERRITIN, IMMUNOGOLD labeling, ELECTRON microscopy, IMMUNOHISTOCHEMISTRY, DUODENAL diseases, GENETIC markers
Abstract

Background The brush border ferric reductase (Dcytb) is critical for the absorption of dietary iron and appears to be expressed on the duodenal enterocyte brush border. The Dcytb expression is increased in severe iron-deficient anaemia, but the situation in a more typical mild iron deficiency is unclear. This study investigated Dcytb expression in patients with normal iron status or mild iron deficiency and its relationships with enterocyte iron status. Materials and methods Duodenal biopsy specimens and blood samples were obtained from 32 patients undergoing routine upper gastrointestinal endoscopy. Twenty-three specimens (six iron-deficient and 17 iron-replete) were processed for light-microscopy (LM) and for immunohistochemistry with antibodies against Dcytb and heavy/light chain ferritin subunits. The nine remaining biopsies (three iron-deficient and six iron-replete) were processed for electron microscopy (EM). Immunolocalization of Dcytb and intracellular ferritin was performed with appropriate primary antibodies followed by 10-nm gold conjugate labels. Results The LM process showed a strong negative correlation between immunolabelling intensity of Dcytb on the enterocyte brush border and serum iron saturation ( P < 0·001), but only a weak negative correlation between this antigen and haemoglobin ( P = 0·08) or serum ferritin concentrations ( P = 0·4). EM confirmed anti-Dcytb preferential labelling of microvilli rather than enterocyte cytoplasm ( P = 0·001), but preferential antiferritin labelling of cytoplasm ( P < 0·02). There was no correlation with enterocyte cytoplasmic ferritin labelling (i.e. enterocyte iron status and Dcytb expression). Conclusions Enterocyte Dcytb brush border expression is increased even in mild iron deficiency and may be related to serum iron saturation. The lack of correlation with enterocyte ferritin expression deserves further study with direct measurement of intracellular iron. [ABSTRACT FROM AUTHOR]

Published
2006
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246. Morphology and response of roots of pasture species to phosphorus and nitrogen nutrition.

Author

Hill, J. O., Simpson, R. J., Moore, A. D., and Chapman, D. F.

Subjects
*PLANT roots, *PLANT morphology, *PLANT growth, *PASTURE plants, *PLANT species, *PLANT nutrition, *NITROGEN in soils, *PHOSPHORUS in soils, *SOIL mineralogy
Abstract

The root morphology of ten temperate pasture species (four annual grasses, four perennial grasses and two annual dicots) was compared and their responses to P and N deficiency were characterised. Root morphologies differed markedly; some species had relatively fine and extensive root systems ( Vulpia spp., Holcus lanatus L. and Lolium rigidum Gaudin), whilst others had relatively thick and small root systems ( Trifolium subterraneum L. and Phalaris aquatica L.). Most species increased the proportion of dry matter allocated to the root system at low P and N, compared with that at optimal nutrient supply. Most species also decreased root diameter and increased specific root length in response to P deficiency. Only some of the species responded to N deficiency in this way. Root morphology was important for the acquisition of P, a nutrient for which supply to the plant depends on root exploration of soil and on diffusion to the root surface. Species with fine, extensive root systems had low external P requirements for maximum growth and those with thick, small root systems generally had high external P requirements. These intrinsic root characteristics were more important determinants of P requirement than changes in root morphology in response to P deficiency. Species with different N requirements could not be distinguished clearly by their root morphological attributes or their response to N deficiency, presumably because mass flow is relatively more important for N supply to roots in soil. [ABSTRACT FROM AUTHOR]

Published
2006
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