Biomedical subjects

K M McLean

Publications and source records attributed to K M McLean.

7 recordsLinked to original sources

PubMed2001

The architecture of a collagen coating on a synthetic polymer influences epithelial adhesion.

The current study sought to identify a collagen coating methodology for application to polymer surfaces that would provide for the development of adhesive structures responsible for the sustained adhesion of corneal epithelial tissue. We compared an uncoated microporous polycarbonate surface and equivalent surfaces coated with either covalently immobilized collagen I or chemically crosslinked collagen I gel in a corneal explant outgrowth assay over 21 days. Electron microscopy was used to examine the formation of hemidesmosomes, basal lamina, and anchoring fibrils at the tissue-polymer interface. The crosslinked collagen gel preparation supported the overlying epithelial tissue across the pore openings and allowed for the formation of identifiable basal lamina, hemidesmosomes, and anchoring fibrils between the epithelial tissue and the polymer surface. Hemidesmosomal plaque, but no basal lamina or anchoring fibril formation, occurred on the uncoated surface or on that coated with covalently immobilized collagen I. We propose that the collagen matrix provided by the crosslinked collagen gel was reorganized by the epithelial tissue and that this, combined with the secretion of ECM molecules, served to limit the diffusion of basement membrane components, which permitted an increase in the local concentration of these molecules, which favored the assembly of epithelial adhesive structures.

Animals↗

PubMed2001

XPS and surface-MALDI-MS characterisation of worn HEMA-based contact lenses.

XPS and MALDI-MS were used to analyse initial adsorption events in the fouling of HEMA-based contact lenses. All of the lenses tested accumulated tear film deposits within 10 min of wear. XPS indicated the presence of mainly proteinaceous deposits, with indications of some contributions by mucins or lipids on some lenses and the nature of the deposit being influenced by the lens chemistry. MALDI-MS detected the presence of surface-adsorbed species with molecular weights < 15 kDa. While lysozyme could be identified by comparison of MALDI-MS signals with known protein mass and assignments are suggested for some other signals, several other species, with MWs less than that of lysozyme, could not be identified as no ocular proteins with corresponding MWs had been reported in previous biochemical tear film analyses. These species, and others, were also detected in MALDI-MS analysis of reflex tear film, suggesting that the adsorbed unidentified species were not simply products of surface-induced dissociation of adsorbing higher-MW proteins. This short-term wear study detected rapid interface conversion and demonstrated the utility and surface sensitivity of XPS and MALDI-MS in characterising contact lens deposits at the initial stages when sub-monolayer adsorbed amounts are present on lenses.

Adsorption↗

PubMed2001

A review of the development of a synthetic corneal onlay for refractive correction.

A synthetic corneal onlay, or implantable contact lens, could obviate the need for spectacles or conventional contact lenses in patients who seek convenient, reversible correction of refractive error. Several research groups have attempted to develop such a product in the past but much of the data from these studies remains unpublished due to commercial interests. This article reviews relevant papers and patents in the corneal implant field and discusses our efforts to develop a synthetic corneal onlay using a perfluoropolyether-based polymer.

Animals↗

PubMed2000

Peptoid-containing collagen mimetics with cell binding activity.

Collagen mimetic peptides containing the peptoid residue Nleu (Goodman Bhumralkar, Jefferson, Kwak, Locardi. Biopolymers 1998;47:127-142) were tested for interactions with epithelial cells and fibroblasts. Molecules containing the sequence Gly-Pro-Nleu with a minimum of nine repeats showed cell binding activity. The activity of these molecules appeared to be conformationally sensitive, with the triple-helical form being preferred. When immobilized on a surface, the (Gly-Pro-Nleu)(10)-Gly-Pro-NH(2) sequence stimulated the attachment and growth of corneal epithelial cells and fibroblasts and the migration of epithelial tissue. The peptide sequence KDGEA inhibited cell attachment to the (Gly-Pro-Nleu)(10)-Gly-Pro-NH(2) sequence, suggesting that cell binding to this collagen mimetic involves the alpha2beta1 heterodimer integrin receptor. Interestingly, peptides containing the sequence (GlyNleu-Pro-)(10)-NH(2) did not have cell binding activity. The discovery that triple-helical peptides containing the Gly-Pro-Nleu sequences interact with cells opens up new opportunities in the design of collagen mimetic biomaterials.

Amino Acid Sequence↗

PubMed2000

Effect of porosity and surface hydrophilicity on migration of epithelial tissue over synthetic polymer.

The relative effects of porosity and surface chemistry on the migration of epithelial tissue over the surface of a polymer were determined in vitro. These studies compared nonporous polymers with those having 0.1-microm diameter track-etched pores and were conducted on polycarbonate and polyester. Epithelial tissue migration over the polymer surface was stimulated by the presence of these pores. The surface chemistries of the polymers were modified by deposition of various polymer films using radio frequency gas deposition, giving a range of surfaces that varied in air:water sessile contact angle (SCA) of between 26 and 100 degrees. Tissue migration on the nonporous surfaces was affected by the surface chemistry, being generally linear as a function of the SCA and higher on hydrophilic than on hydrophobic surfaces but reduced if the hydrophilic surface had a mobile chemistry. The effects of the 0.1-microm diameter pores and the surface hydrophilicity were additive with the maximal level of epithelial tissue migration occurring on a porous, hydrophilic polymer surface.

Animals↗

PubMed1992

Increased resistance to ionizing and ultraviolet radiation in Escherichia coli JM83 is associated with a chromosomal rearrangement.

Cells cope with radiation damage through several mechanisms: (1) increased DNA repair activity, (2) scavenging and inactivation of radiation-induced radical molecules, and (3) entry into a G0-like quiescent state. We have investigated a chromosomal rearrangement to elucidate further the molecular and genetic mechanisms underlying these phenomena. A mutant of Escherichia coli JM83 (phi 80dlacZ delta M15) was isolated that demonstrated significantly increased resistance to both ionizing and ultraviolet radiation. Surviving fractions of mutant and wild-type cells were measured following exposure to standardized doses of radiation. Increased radioresistance was directly related to a chromosomal alteration near the bacteriophage phi 80 attachment site (attB), as initially detected by the LacZ- phenotype of the isolate. Southern hybridization of chromosomal DNA from the mutant and wild-type E. coli JM83 strains indicated that a deletion had occurred. We propose that the deletion near the attB locus produces the radioresistant phenotype of the E. coli JM83 LacZ- mutant, perhaps through the alteration or inactivation of a gene or its controlling element(s).

Cell Survival↗

PubMed1987

Expression in Escherichia coli of a cloned crystal protein gene of Bacillus thuringiensis subsp. israelensis.

A ca. 10-kilobase (kb) HindIII fragment of plasmid DNA from Bacillus thuringiensis subsp. israelensis was cloned into plasmid pUC9 and transformed into Escherichia coli. Extracts of the recombinant strain contained a 27-kilodalton (kDa) peptide that reacted with antibodies to a 27-kDa peptide isolated from crystals produced by B. thuringiensis subsp. israelensis. Extracts of the recombinant strain were hemolytic and toxic to Aedes aegypti larvae. Full expression of the 27-kDa peptide required the presence of a ca. 0.8-kb region of DNA located 4 kb upstream from the structural gene; the 0.8-kb region could be present in cis or trans relative to the gene and apparently acted post-transcriptionally. Analysis of maxicells showed that the 10-kb insert also coded for peptides of 67, 20, and 16 kDa; data obtained with different subclones suggest that the 20-kDa peptide is encoded in the 0.8-kb DNA region.

Bacillus thuringiensis↗