Synthesis of porous emulsion-templated polymers using high internal phase CO2-in-water emulsions.

Highly porous emulsion-templated materials were synthesized by polymerization of concentrated CO(2)-in-water (C/W) emulsions. The method does not use any organic solvents, in either the synthesis or purification steps, and no solvent residues are left in the materials. It was found that the emulsion stability is strongly affected both by the nature of the surfactant and by the viscosity of the aqueous continuous phase. By optimizing these parameters, it was possible to generate a highly porous, low-density polyacrylamide material with a pore volume of 5.22 cm(3)/g, an average pore diameter of 9.72 microm, and a bulk density of 0.14 g/cm(3). We have broadened the scope of this approach significantly by identifying inexpensive hydrocarbon surfactants to stabilize the C/W emulsions (e.g., Tween 40) and by developing redox initiation routes that allow the synthesis to be carried out at modest temperatures and pressures (20 degrees C, 65 bar). We have also extended the method to the polymerization of monomers such as hydroxyethyl acrylate, which suggests that it is possible to prepare a range of solvent-free biomaterials by this route.

Confocal microscopy of a dense particle system.

We report experiments utilizing confocal microscopy to determine the position of cornflour starch granules in a paste, as a function of distance from a wall. The granules have an average diameter of 15 mum. If a solvent is chosen such as to approximately match the refractive index of the granules then images of them can be obtained to a depth of 120 mum, which is the limit imposed by the working distance of the x 40 oil immersion lens used in the experiment. An algorithm is presented which successfully identifies the particle centers in 3D. In addition to experiments on static systems we show how measurements of particle number density and velocity can be obtained from images of a system in pipe flow. We find that particles are depleted from the wall over a range of around 100 mum.

Collagen VII expression in human chronic wounds and scars.

Collagen VII is the major structural component of the anchoring fibrils that stabilize the cutaneous basement membrane on the dermis. Disruption and, more usually, destruction of the basement membrane are characteristic of wounds that are slow, or fail, to heal, such as chronic lower-limb or pressure ulcers. In this study, the expression of collagen VII was analysed in 28 human chronic cutaneous wounds or scars using a reverse transcription-polymerase chain reaction (RT-PCR) technique. Collagen VII expression was detected in 26 of these 28 cutaneous wounds, but not in two wounds, neither of which showed any clinical evidence of healing.

Basement-membrane stromal relationships: interactions between collagen fibrils and the lamina densa.

Collagens, the most abundant molecules in the extracellular space, predominantly form either fibrillar or sheet-like structures-the two major supramolecular conformations that maintain tissue integrity. In connective tissues, other than cartilage, collagen fibrils are mainly composed of collagens I, III, and V at different molecular ratios, exhibiting a D-periodic banding pattern, with diameters ranging from 30 to 150 nm, that can form a coarse network in the extracellular matrix in comparison with a fine meshwork of lamina densa. The lamina densa represents a stable sheet-like meshwork composed of collagen IV, laminin, nidogen, and perlecan compartmentalizing tissue from one another. We hypothesize that the interactions between collagen fibrils and the lamina densa are crucial for maintaining tissue-tissue interactions. A detailed analysis of these interactions forms the basis of this review article. Here, we demonstrate that there is a direct connection between collagen fibrils and the lamina densa and propose that collagen V may play a crucial role in this connection. Collagen V might also be involved in regulation of collagen fibril diameter and anchoring of epithelia to underlying connective tissues.

Isolated collagen IV retains the potential to form an 18-nm sided polygonal meshwork of the lamina densa.

Polygonal meshworks were revealed in the aggregates reconstituted from isolated collagen IV as well as in the lamina densa of mouse pancreas by the quick-freezing and deep-etching technique. Collagen IV solution with acetic acid from the bovine lens capsules and that isolated from the pepsin-solubilized fraction of human placenta reconstituted polygonal meshworks, which were dimensionally similar to the meshwork seen in the lamina densa of mouse pancreas. The average lengths between branching points in the lamina densa, and the meshworks of collagen IV derived from the bovine lens capsules and from the human placenta were 20.1 +/- 7.7 nm (mode = 18 nm), 21.6 +/- 11.3 nm (mode = 14 nm), and 21.6 +/- 9.0 nm (mode = 18 nm), respectively. These observations suggest that collagen IV can, in the absence of other macromolecules including laminins, comprise a skeletal meshwork similar in dimensions to that of the lamina densa.

Reverse transcription-polymerase chain reaction detection of collagen transcripts in healing human wounds.

The aim of this study was to analyse the expression of COl1A1, COl1A2 and COl3A1 in 6 mm diameter punch biopsies obtained from human wounds. Total RNA was isolated from biopsies taken from Sacrococcygeal pilonidal sinus excision cavities at weekly intervals between surgery and clinical closure. cDNAs were generated from the RNA using reverse transcriptase and polymerase chain reaction (PCR) amplifications performed with oligonucleotide primer pairs specific for regions of the COl1A1, COl1A2 and COl3A1 genes. The expression of these three genes was demonstrated throughout the course of healing on 36 biopsies taken from nine patients between surgery and clinical closure. Amplification bands demonstrated on cDNAs generated from 6 mm diameter biopsies were comparable in intensity and specificity with those generated from 50 mg excised scar tissue and cultured fibroblasts. The RT-PCR technique described here allows the rapid 'routine' detection of specific gene expression in 6 mm biopsies obtained from healing wounds.

From the Journals.

Dermal collagens and skin ageing Leg ulcers and quality of life Pneumatic compression and ulcer healing Fibrin degradation and adhesion formation.

Review of classic research:Control of scarring.

The three critiques below discuss the influence of the following paper on wound care: Control of scarring in adult wounds by neutralising antibody to transforming growth factor-ß.

The complete cDNA derived sequence of the rat prolyl 4-hydroxylase alpha subunit.

A rat cDNA encoding the prolyl 4-hydroxylase alpha subunit (P4H alpha) was isolated and sequenced. The primary aa sequence deduced from the nucleotide sequence reveals a 534-aa protein that shows extensive aa identity with the human (88%) and chick (77%) P4H alpha.

The pathogenesis of hypertrophic/keloid scarring.

The formation of hypertrophic and keloid scars after cutaneous wounding is of particular relevance to the practice of maxillofacial surgery. This paper reviews current knowledge of the local and systemic factors underlying the formation of these scars and outlines the current and potential treatment modalities for these lesions.

From the Journals.

Wound care in patients with HIV The development of pressure sores Gene transcription factors.

Detection of sequence variants in the gene for human type II procollagen (COL2A1) by direct sequencing of polymerase chain reaction-amplified genomic DNA.

The direct sequencing of the human type II procollagen (COL2A1) gene from polymerase chain reaction (PCR)-amplified genomic DNA is described. Thirty-two regions of the COL2A1 gene were asymmetrically amplified with intron primers which were specifically chosen to amplify a region spanning 500 to 800 bp of sequence encoding one or more exons and their accompanying intervening sequences. Primers for dideoxynucleotide sequencing of the PCR products were then designed to provide complete exon sequence information and to insure that intron:exon splice junction sequence data would be obtained. Amplification and sequencing reactions were performed on an automated workstation to facilitate the handling of multiple DNA templates. The procedure allowed efficient sequencing of over 25,000 bp of each allele of the COL2A1 gene per diploid genome. We used this method for the comparative analyses of COL2A1 sequences in DNA isolated from the blood of 42 unrelated individuals and we identified 21 neutral sequence variants in the gene. The sequence variations were confirmed by independent assays, including restriction enzyme digestion. The sequence variants described here will be important for identifying haplotypes of the type II procollagen gene that will be useful in defining a genetic etiology for diseases of cartilaginous tissues.

Growth factors and extracellular matrix biosynthesis.

The second article in a series on the biology of wound healing looks at the regulatory mechanisms in the wound-healing process.

Reviews.

WOUND HEALING THE MANAGEMENT OF LEG ULCERS LEG ULCERS WOUND MANAGEMENT AND DRESSINGS.

Molecular components of the extracellular matrix.

The first article in a series on the biology of wound healing examines the role of the molecular components of the extracellular matrix.

Glycosylated haemoglobin by affinity chromatography in diabetic and non-diabetic children.

We have made an evaluation of glycosylated haemoglobin measurements by affinity chromatography in a paediatric population. Age-related reference values for non-diabetic infants and children are reported. A poor correlation (r = 0.24) was found between glycosylated haemoglobin values in 26 insulin-dependent diabetic children and the paediatrician's independent assessment of clinical control.