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Biomedical subjects

P Gilson

Publications and source records attributed to P Gilson.

8 recordsLinked to original sources
PubMed2004

Hydrophilicity of 3-D biomaterials: the Washburn equation.

Characterisation and quantification of the surface energy of biomaterials used as tissue engineering scaffolds is important, but many of the techniques available to examine these properties are only applicable to smooth flat samples, not porous materials. This paper describes the application of the Washburn equation to measure the surface energy of a range of porous polyether polyurethane scaffolds with three test liquids; n-Hexane was used to measure a material constant, whilst ethanol and xylene were used to measure contact angles. The results show that the Washburn equation is not applicable in its current form, reasons for this could be that the voids in the materials are too wide for effective capillarity; absorption of the solvents into the polymer matrix may further complicate the measured imbibition profile. Another possible reason is the differences between the sizes of the interconnecting pores in scaffolds with varying void sizes; this could affect the capillary effect of the test liquids through the material. The repeatability of the results and the similar patterns observed with the different liquids suggest that if these issues could be quantified and incorporated into the Washburn equation, it may be possible to generate useful results for similar materials.

Absorption↗
PubMed2001

NaAGP4 is an arabinogalactan protein whose expression is suppressed by wounding and fungal infection in Nicotiana alata.

Arabinogalactan proteins (AGPs) are proteoglycans secreted by plant cells that have been implicated in plant growth and development. Most AGPs cloned to date possess highly labile glycosylphosphatidylinositol (GPI) lipid anchors. These anchors transiently attach AGPs to the plasma membrane before they are released into the cell wall following GPI anchor hydrolysis. We have isolated and partially sequenced the protein core of an AGP purified from styles of Nicotiana alata. The protein sequence data were utilised to clone the AGP's gene, NaAGP4. This AGP shares about 78% sequence identity with the tomato AGP LeAGP-1. RNA gel blot analyses of different plant organs indicate that NaAGP4 is expressed in the same tissues and at similar levels as LeAGP-1. Furthermore, NaAGP4 like LeAGP-1 is rapidly suppressed by tissue wounding and by pathogen infection. We believe NaAGP4 and LeAGP-1 are the first described examples of orthologous AGPs from different plant species. In contrast, another AGP from N. alata, NaAGP1, is comparatively unaffected by wounding and pathogen infection, although this AGP is expressed in similar tissues and at similar levels as NaAGP4.

Amino Acid Sequence↗
PubMed1995

The chlorarachniophyte: a cell with two different nuclei and two different telomeres.

Chlorarachniophyte algae contain a complex chloroplast derived from the endosymbiosis of a eukaryotic alga. The reduced nucleus of the endosymbiont, the nucleomorph, is located between the inner and outer pair of membranes surrounding the chloroplast. The nucleomorph of chlorarachniophytes has previously been demonstrated to contain at least three small linear chromosomes. Here we describe cloning the end of the smallest nucleomorph chromosome which is shown to carry a telomere consisting of a tandemly repeated 7 bp sequence, TCTAGGG. Using the telomere repeat as a probe, we show that nucleomorph telomeres display typical hetero-disperse size distribution. The nucleomorph is shown to contain only three chromosomes with a haploid genome size of just 380 kb. All six nucleomorph chromosome termini are identical with an rRNA cistron closely linked to the telomere. The nucleomorph chromosomes thus have relatively large inverted repeats at their ends. Chromosomes from the host nucleus are shown to have a different telomere repeat motif to that of the nucleomorph chromosomes.

Animals↗
PubMed1992

Hepatic perfusion index: a multicentre trial.

The reproducibility and accuracy of the hepatic perfusion index (HPI) was examined by consideration of in vitro and in vivo factors. A phantom was used to simulate liver blood flow and data acquired on nine gamma cameras. Dynamic hepatic scintigraphy was undertaken on 28 patients at two centres and values obtained for the HPI. Results from the phantom study showed good agreement between the nine cameras and also with the HPI values predicted from the measured phantom flow rates. The results of the patient study indicated a high degree of conformity between observers (r = 0.95, S.E = 0.03) but poorer correlation between the HPI values from the two centres (r = 0.67, S.E. = 0.09). These results imply that centres wishing to use HPI clinically should establish their own range of normality.

Blood Flow Velocity↗
PubMed1989

Limb volume measurements in peripheral arterial disease.

A simple method for measuring limb volumes of patients with peripheral arterial disease undergoing limb blood flow measurement is described. The device uses the change in surface level of water in a cylindrical reservoir to generate a voltage which is amplified and converted to a volume. The plethysmograph is stable and accurate over a wide range of limb volumes. For patients with leg ulcers or gangrene, where water immersion is not possible, a geometrical model has been developed which allows the volume to be calculated from a series of six external measurements. Comparison with measured volumes in 46 patients has shown this model to be accurate with a mean error of 3.3%. It provides a convenient alternative to direct measurement in these patients.

Blood Volume↗
PubMedDate not supplied

Preliminary characterisation of chlorarachniophyte mitochondrial DNA.

The division Chlorarachniophyte comprises amoeboflagellate protists with complex chloroplasts derived from the endosymbiosis of a eukaryotic alga. Analysis of chlorarachniophyte chromosomal DNAs by pulsed-field gel electrophoresis revealed an apparently linear 36-kb chromosome that could not be ascribed to either the host or endosymbiont nuclei. A single eubacterial-like small subunit ribosomal RNA gene is encoded on this chromosome and phylogenetic analyses places this gene within a clade of mitochondrial genes from other eukaryotes. High resolution in situ hybridization demonstrates that transcripts of the small subunit ribosomal RNA gene encoded by the 36-kb chromosome are exclusively located in the mitochondria. The 36-kb chromosome thus likely represents a linear mitochondrial genome. Small amounts of an apparently dimeric (72 kb) form are also detectable in pulsed-field gel electrophoresis.

Animals↗