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Biomedical subjects

P J Sharpe

Publications and source records attributed to P J Sharpe.

14 recordsLinked to original sources
PubMed2007

Defining 'full-length' recombinant factor VIII: a comparative structural analysis.

Coagulation factor VIII (FVIII) is an important glycoprotein co-factor involved in haemostasis, functioning to accelerate activation of factor X by activated factor IX. Insertion of expression vectors containing the full-length cDNA sequence of human FVIII into mammalian cell lines results in the production of recombinant factor VIII (rFVIII), typically referred to as 'full-length' rFVIII (FLrFVIII). Both FLrFVIII and plasma-derived FVIII exist primarily as heterodimeric proteins, consisting of a heterogenous light and heavy chain. The objectives of this study were to compare the structural heterogeneity of high-purity FVIII preparations and further define the term 'full length' as it refers to rFVIII protein structure. Five commercially available FVIII concentrates were characterized based on SDS-PAGE, N-terminal sequencing, and peptide and domain mapping coupled to mass spectrometry. The major heavy chain species identified in FLrFVIII included various B-domain-truncated forms of FVIII, with the predominant species terminating at Arg(1313). This study demonstrates that the use of full-sequence FVIII cDNA for the production of rFVIII does not result in a homogeneous FLrFVIII protein product. Rather, commercially available FLrFVIII represents a heterogenous mixture of various B-domain-truncated forms of the molecule, with no evidence of a contiguous, intact B-domain.

Chromatography, High Pressure Liquid↗
PubMed1990

Ozone alters carbon allocation in loblolly pine: assessment with carbon-11 labeling.

Loblolly pine (Pinus taeda L.) seedlings were exposed to 0.120 micromol mol(-1) (ppm) ozone for 7 h per day, 5 days per week for 12 weeks. No visible damage resulted from this regime. A short-lived radioisotope of carbon ((11)C) was used to characterize changes in plant physiology caused by ozone, the first time this technique has been used for ozone exposure studies. In comparison to plants kept in charcoal-filtered air, pines exposed to ozone exhibited reductions in photosynthesis (16%), speed of phloem transport (11%), phloem photosynthate concentration (40%) and total carbon transport toward roots (45%). Photosynthate not transported to the roots appeared to accumulate in the stems. Primary branches of pines exposed to ozone were some 50-60% heavier than those of control pines. Ozone was thus shown to have a significant short-term impact on phloem transport processes that results in a shift in allocation of photosynthate favoring stems.

Journal Article↗
PubMed1985

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles.

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.

Biological Transport↗
PubMed1981

High-temperature Disruption of Guard Cells of Vicia faba: EFFECT ON STOMATAL APERTURE.

Increased variability in stomatal aperture at high temperatures can be attributed, in part, to the differential sensitivity of guard cells to thermal damage. Individual stomata become increasingly open at higher temperatures until guard cells are lethally damaged; at that temperature, apertures decrease. The extent of irreversible damage causing closure was estimated by K(+) uptake, neutral red accumulation, and visual scoring of chloroplasts.This study found that visual scoring of chloroplast disruption provided the best estimate of guard cell viability at high temperature. Removal of the damaged guard cells from the population sample resulted in a constant coefficient of variability for apertures over the temperature range 25 to 50 C.

Journal Article↗
PubMed1978

Toward the engineering of photosynthetic productivity.

This article is a review of progress towards a general quantitative theory of photosynthetic productivity or autotrophy in plants. It is not intended to be an exhaustive review, but rather a perspective of the autotrophic puzzle and current approaches to its solution. The review describes attempts to quantitatively describe a generalized plant based on theoretical expressions for its component parts. Particular emphasis has been placed on the source-transport-sink continuum. This continuum can be broken into five subsections: 1. Stomal mechanics and physiology 2. Photosynthesis (within chlorophyllous cells) 3. Mass and energy exchange between the leaf and environment 4. Phloem translocation 5. Sink metabolism models Progress towards the development of physiologically based models in each of the above areas is assessed, relying heavily on the approach and findings of the authors and their colleagues. The problems and possibilities inherent in attempting to couple these components into a generic model of productivity are discussed. Finally, the potential benefits and hazards of genetic engineering of plants are discussed, and weaknesses in the current approach are highlighted.

Biophysical Phenomena↗
PubMed1976

Concentration-dependent Unloading as a Necessary Assumption for a Closed Form Mathematical Model of Osmotically Driven Pressure Flow in Phloem.

Previous attempts to model steady state Münch pressure flow in phloem (Christy and Ferrier. [1973]. Plant Physiol. 52: 531-538; and Ferrier et al. [1974]. Plant Physiol. 54: 589-600) lack sufficient equations, and results were produced which do not represent correct mathematical solutions. Additional equations for the present closed form model were derived by assuming that unloading of a given solute is dependent upon the concentration of that solute in the sieve tube elements. Examples of linear and enzymic type unloading mechanisms are given, although other concentration-dependent mechanisms could be substituted. A method for a numerical solution is outlined, and proof of convergence is presented along with some representative data and the speed of computer calculations. The model provides the minimal set of equations for describing the Münch pressure flow hypothesis as it might operate in plants.

Journal Article↗