Can sensation of cold hands predict Raynaud's phenomenon or paraesthesia?

Background: Raynaud's phenomenon and neurosensory symptoms are common after hand-arm vibration exposure. Knowledge of early signs of vibration injuries is needed. Aims: To investigate the risk of developing Raynaud's phenomenon and paraesthesia in relation to sensation of cold hands in a cohort of male employees at an engineering plant. Methods: We followed a cohort of male manual and office workers at an engineering plant in Sweden for 21 years. At baseline (1987 and 1992) and each follow-up (1992, 1997, 2002, 2008), we assessed sensation of cold, Raynaud's phenomenon and paraesthesia in the hands using questionnaires and measured vibration exposure. We calculated risk estimates with univariate and multiple logistic regression analyses and adjusted for vibration exposure and tobacco usage. Results: There were 241 study participants. During the study period, 21 individuals developed Raynaud's phenomenon and 43 developed paraesthesia. When adjusting the risk of developing Raynaud's phenomenon for vibration exposure and tobacco use, the odds ratios were between 6.0 and 6.3 (95% CI 2.2-17.0). We observed no increased risk for paraesthesia in relation to a sensation of cold hands. Conclusions: A sensation of cold hands was a risk factor for Raynaud's phenomenon. At the individual level, reporting a sensation of cold hands did not appear to be useful information to predict future development of Raynaud's phenomenon given a weak to moderate predictive value. For paraesthesia, the sensation of cold was not a risk factor and there was no predictive value at the individual level.

Differentiation of a fibrin gel encapsulated chondrogenic cell line.

Hyaline cartilage has very limited regenerative capacity following damage. Therefore engineered tissue substitutes have been the focus of much research. Our objective was to develop a fibrin-based scaffold as a cell delivery vehicle and template for hyaline cartilage regeneration, and compare its cellular properties against monolayer and pellet culture for chondrogenic cells. The chondrogenic precursor cell line, RCJ 3.1C5.18 (C5.18), was chosen as a test system for evaluating the effect of various culture conditions, including cell encapsulation, on articular chondrogenic cell differentiation. The C5.18 cells in monolayer showed elevated expression of collagen II, an articular chondrogenic marker, but also markers for fibrocartilage differentiation (collagen I and versican) when cultured with chondrogenic medium as compared to basic maintenance medium. Pellets of C5.18 cells cultured in chondrogenic medium were histologically more organized in structure than pellets cultured in control maintenance medium. The chondrogenic medium cultured pellets also secreted an extracellular matrix that was comprised of type II with very little type I collagen, indicating a trend towards a more hyaline-like cartilage. Moreover, when cultured in chondrogenic medium, fibrin-encapsulated C5.18 cells elaborated an extracellular matrix containing type II collagen, as well as aggrecan, which are both components of hyaline cartilage. This indicated a more articular-like chondrogenic differentiation for fibrin encapsulated C5.18 cells. The results of these experiments provide evidence that the C5.18 cell line can be used as a tool to evaluate potential scaffolds for articular cartilage tissue engineering.

Recruitment of multiple cell lines by collagen-synthetic copolymer matrices in corneal regeneration.

Collagen hydrogel matrices with high optical clarity have been developed from collagen I, cross-linked with a copolymer based on N-isopropylacrylamide, acrylic acid and acryloxysuccinimide. The controlled reaction of collagen amine groups with this copolymer under neutral pH and aqueous conditions gave robust, optically clear hydrogels and prevented the excessive collagen fibrillogenesis that can lead to collagen opacity. These sterile, non-cytotoxic hydrogels allowed epithelial cell overgrowth and both stromal cell and nerve neurite ingrowth from the host tissue. This regenerative ability appeared to result from the high glucose permeability, nanoporosity and the presence of cell adhesion factors, RGD in collagen and the laminin pentapeptide, YIGSR, grafted onto the copolymer. Under physiological conditions, optical clarity superior to the human cornea and tensile performance adequate for suturing were obtained from some formulations.

Bioactive hydrogel-filament scaffolds for nerve repair and regeneration.

The design of novel biomaterials is crucial for the advancement of tissue engineering in nerve regeneration. In this study we developed and evaluated novel biosynthetic scaffolds comprising collagen crosslinked with a terpolymer of poly(N-isopropylacrylamide) (PNiPAAm) as conduits for nerve growth. These collagen-terpolymer (collagen-TERP) scaffolds grafted with the laminin pentapeptide YIGSR were previously used as corneal substitutes in pigs and demonstrated enhanced nerve regeneration compared to allografts. The purpose of this project was to enhance neuronal growth on the collagen-TERP scaffolds through the incorporation of supporting fibers. Neuronal growth on these matrices was assessed in vitro using isolated dorsal root ganglia as a nerve source. Statistical significance was assessed using a one-way ANOVA. The incorporation of fibers into the collagen-TERP scaffolds produced a significant increase in neurite extension (p<0.05). The growth habit of the nerves varied with the type of fiber and included directional growth of the neurites along the surface of certain fiber types. Furthermore, the presence of fibers in the collagen-TERP scaffolds appeared to influence neurite morphology and function; neurites grown on fibers-incorporated collagen-TERP scaffolds expressed higher levels of Na channels compared to the scaffolds without fiber. Overall, our results suggest that incorporation of supporting fibers enhanced neurite outgrowth and that surface properties of the scaffold play an important role in promoting and guiding nerve regeneration. More importantly, this study demonstrates the potential value of tissue engineered collagen-TERP hybrid scaffolds as conduits in peripheral nerve repair.

Properties of porcine and recombinant human collagen matrices for optically clear tissue engineering applications.

Porcine and recombinant human atelocollagen I solutions were cross-linked with a water soluble carbodiimide at various stoichiometries and collagen concentrations (5-20 w/w %). The resulting hydrogels were clear and, when used as cell growth matrices, allowed cell and nerve visualization in vitro and in vivo. We have previously reported that, after six months of implantation in pigs' and rabbits' corneas, these robust hydrogels allowed regeneration of host cells and nerves to give optically clear corneas with no detected loss in thickness, indicating stable engraftment. Here, the biocompatible hydrogel formulations leading to this novel in vivo performance were characterized for amine consumption, gel hydration, thermal properties, optical clarity, refractive index, nutrient diffusion, biodegradation, tensile measurements, and average pore diameters. Gels with excellent in vitro (epithelial overgrowth, neurite penetration) and in vivo performance (clarity, touch sensitivity regeneration) had 4-11 nm pores, yet had glucose and albumin diffusive coefficients similar to mammalian corneas and allowed neurite extension through the gels.

Analyses of volatile transformation products from additives in gamma-irradiated polyethylene packaging.

Thermal desorption, followed by gas chromatography (GC) with mass spectrometry (MS) detection, has been found to allow the rapid identification of volatile products resulting from the gamma-irradiation of stabilized, high density polyethylene packaging and pure stabilizers. The stabilizers were tris(2,4-di-tert.butylphenyl) phosphite, octadecyl beta-(2,6-di-tert.butylphenol)-propionate and 2,4-di-tert.butylphenol, the latter resulting from phosphite hydrolysis. Thermal desorption indicated the formation and release of tert.butylbenzenes, such as 1,3-di-tert.butylbenzene upon gamma-irradiation of the HDPE. From a comparison of the products from gamma-irradiation of additive-free polyethylene, of various pure stabilizers and of related compounds, the tert.butylbenzenes were confirmed to result from the irradiation of the phosphite stabilizer and its phosphate conversion product. Thermal desorption off-line, in which volatiles released by a sample are trapped in sorbents for subsequent desorption in the heated GC inlet, is found to be a fast, extremely sensitive method that can be used to guide and supplement analyses of compounds extracted by foodstuffs.

Phosphite additives and their transformation products in polyethylene packaging for gamma-irradiation.

Infrared (IR) spectroscopy has been used to identify and quantify the phosphite antioxidant, tris(2,4-di-tert.butylphenyl) phosphite, and its corresponding phosphate in high density polyethylene (HDPE) food trays, both in the original, commercial trays and also as a function of gamma-irradiation and post-irradiation, storage conditions. This direct method of inhibitor analysis complements time-consuming (some times non-quantitative) extraction methods, which for organo-phosphites are complicated by their facile conversion to phosphates by peroxidic impurities in the solvent. Because of the complete destruction of phosphite to give mainly phosphate at quite low gamma-irradiation doses (approximately 5 kGy) and phosphate formation during melt processing and radiation sterilization of these HDPE trays must take into account products from the irradiation of phosphate. Any residual phosphite is lost progressively in post-irradiation reactions, which are complex, producing a less than-quantitative yield of phosphate.

A photorefractive organically modified silica glass with high optical gain.

Photorefractive materials exhibit a spatial modulation of the refractive index due to redistribution of photogenerated charges in an optically nonlinear medium. As such, they have the ability to manipulate light and are potentially important for optical applications including image processing, optical storage, programmable optical interconnects and simulation of neural networks. Photorefractive materials are generally crystals, polymers and glasses with electro-optic or birefringent properties and noncentrosymmetric structure. Here we report the photorefractive effect in both non-centrosymmetric and centrosymmetric azo-dye-doped silica glasses, in which refractive index gratings that are spatially phase-shifted with respect to the incident light intensity pattern are observed. The effect results from a nonlocal response of the material to optical illumination, and enables the transfer of energy between two interfering light beams (asymmetric two-beam coupling). Although the writing time for the present grating is relatively slow, we have achieved a two-beam coupling optical gain of 188 cm(-1) in the centrosymmetric glasses, and a gain of 444 cm(-1) in the non-centrosymmetric structures. The latter are fabricated using a corona discharge process to induce a permanent arrangement of azo-dye chromophores.