Computational Modelling of Water Transport in Hydrocolloid Wound Dressing, DuoDERMⓇ CGF, and Design Recommendations

Hydrocolloids, and further hydrogels, have arisen as attractive next-generation wound dressings because of their modularity and ability to retain moisture. Hydrocolloids, like DuoDERM Ⓡ CGF, are intended for partial and full thickness wounds. They may be used for minor burns, cuts, tears, abrasions, as well as lacerations, ulcers, and some traumatic or surgical wounds. A computational simulation of water transport in wounds with hydrocolloid dressings was implemented in order to understand the mechanisms of hydrocolloid wound dressings as they relate to water transport. The ideal dressing will maintain the wounded tissue at physiological water content levels while also retaining moisture within the dressing itself to promote re-epithelialization of tissue. This study aims to determine the effectiveness of current wound dressings with respect to retaining moisture and maintaining the skin at physiological levels of water content. This study further seeks to optimize current wound dressing design parameters in order to improve water retention above the wound bed and maintenance of physiological skin water content. To study the transfer of liquid water in skin and an example hydrocolloid wound dressing, a computational model was built in COMSOL Multiphysics Ⓡ Modeling Software using a multifrontal direct solver (MUMPS). This model primarily detailed water transport processes in the skin (stratum corneum, epidermis, and dermis) with an example hydrocolloid dressing DuoDERM Ⓡ CGF (hydrocolloid and polymeric barrier layer). The use of the model can be extended to larger or smaller wound areas as well as different types of hydrocolloid dressings. The parameters of the materials can be easily altered to fit new materials being simulated, however the model is only valid up to the time right before the hydrocolloid would start to degrade. The model considered the skin layers, wound surface, hydrocolloid, and polymeric barrier layer to be a 2D, axisymmetric cylinder. Water (mass) transport was considered diffusion in porous media in the skin and diffusion in the hydrocolloid and polymeric layers. The swelling effect, typical of hydrocolloids, was modeled using deforming geometry. After validating the model, an objective function was created in order to quantify the performance of the model based on its ability to maintain physiological water content in the skin as well as its ability to retain moisture in the hydrocolloid domain above the wound bed. Using this objective function, the material properties of the hydrocolloid dressing were altered in order to obtain an optimal solution, where the dressing would maintain an ideally moist environment. The results confirmed that the hydrocolloid wound dressing retains moisture but does not satisfactorily maintain wounded tissue near physiological levels of water content. The optimization suggested the variation of two hydrocolloid parameters, the diffusivity and the partitioning coefficient between the skin and hydrocolloid, in order to improve its performance. Lowering the diffusivity of the hydrocolloid resulted in a higher water concentration above the wound bed. Decreasing the partition coefficient (an effect observed by increasing the hydrophobicity of the hydrocolloid) reduced the flux of water from the wound to the dressing. The combined effect of a reduced diffusivity and partition coefficient allowed greater regions of the wound to retain physiological water content levels and improved water retention near the wound bed. These results will inform the design of future generations of wound dressings and elucidate difficulties in the use of hydrophilic wound dressings like hydrocolloids and hydrogels

The Development of Xenopus tropicalis Transgenic Lines and their Use in Studying Lens Developmental Timing in Living Embryos

The generation of reporter lines for observing lens differentiation in vivo demonstrates a new strategy for embryological manipulation and allows us to address a long-standing question concerning the timing of the onset of differentiation. Xenopus tropicalis was used to make GFP reporter lines with &#;1-crystallin promoter elements directing GFP expression within the early lens. X. tropicalis is a close relative of X. laevis that shares the same ease of tissue manipulation with the added benefits of a diploid genome and faster life cycle. The efficiency of the Xenopus transgenic technique was improved in order to generate greater numbers of normal, adult transgenic animals and to facilitate in vivo analysis of the crystallin promoter. This transgene is transmitted through the germline, providing an accurate and consistent way to monitor lens differentiation. This line permitted us to distinguish models for how the onset of differentiation is controlled: by a process intrinsic to differentiating tissue or one dependent on external cues. This experiment would not have been feasible without the sensitivity and accuracy provided by the in vivo reporter. We find that, in specified lens ectoderm transplanted from neural tube stage donors to younger neural-plate-stage hosts, the onset of differentiation, as measured by expression of the crystallin/GFP transgene, is delayed by an average of 4.4 hours. When specified lens ectoderm is explanted into culture, the delay was an average of 16.3 hours relative to control embryos. These data suggest that the onset of differentiation in specified ectoderm can be altered by the environment and imply that this onset is normally controlled by external cues rather than by an intrinsic mechanism

Immune modulation by parasitic nematodes

Almost 2 billion people world-wide are infected with parasitic helminths. These complex multicellular eukaryotic organisms are capable of establishing long-term infections even in the face of an intact immune response. Typically, in these settings regulatory components of the immune response, such as Foxp3+ T regulatory cells (Tregs), become dominant, limiting protective effector responses towards the parasite. Helminths are thought to have evolved mechanisms, including release of immunomodulatory molecules termed excretory-secretory products (ES), to sway the balance between the regulatory and effector arms of the immune response to favour their persistence. In this thesis both the development of a protective immune response toward, and the potential manipulation of the immune response by, the rodent gastrointestinal nematode Heligmosomoides polygyrus have been studied. Firstly, the effects of H. polygyrus ES (HES) on bone-marrow derived dendritic cells (DCs) were analysed. Although HES did not alter the phenotype of the DC it was found to be able to suppress the ability of the DC to respond to inflammatory stimuli. This activity was lost when HES was heat-inactivated (hiHES). After adoptive transfer, HES-pulsed DCs were able to induce a HESspecific T helper (Th)2-type response even if co-treated with an inflammatory stimulus. Th2-type responses are protective against H. polygyrus infection. Surprisingly, the ability of HES to generate a Th2-response in a co-treatment situation was not related to its anti-inflammatory properties; DCs co-treated with hiHES and an inflammatory stimulus were able to drive an equivalent Th2-response to HES in this situation. Next, making use of mouse strains with different susceptibility phenotypes to primary H. polygyrus infection, potential mechanisms of resistance were characterised. Development of granulomas in the gut wall were found to be associated with reduced worm burdens. Furthermore, in highly susceptible C57BL/6 mice, production of IL-23 was shown to be counter-regulatory to this process, as mice on the same background but deficient in this cytokine have increased numbers of granulomas and dramatically enhanced resistance. Susceptibility to H. polygyrus was also considered at the level of epigenetic regulation. A protein that binds specifically to methylated DNA, methyl-CpG binding domain protein (MBD)2, was found to affect the proportion of Foxp3+ Tregs within the CD4+ T cell population in vivo. Additionally, in vitro induction of Foxp3 in response to TGF-β was enhanced in MBD2-/- CD4+ T cells. MBD2-/- mice had a trend towards increased worm burdens when infected with H. polygyrus, suggesting that the difference in proportion of Tregs may limit generation of an effector response. Finally, the ability of HES to directly affect the regulatory arm of the immune response was focussed upon. It was found that HES was able to induce Foxp3 expression in naïve peripheral T cells, and that this was mediated by stimulation of the TGF-β pathway. The TGF-β mimic was of parasite origin as a pan-vertebrate TGF-β antibody was unable to block its effects but sera from H. polygyrus infected animals was competent to do this. Activity of this type was not limited to HES as ES from the ovine helminth Haemonchus contortus was found to have the same property. These data imply that some helminth parasites have evolved mechanisms to support generation of Foxp3+ Tregs, thus favouring the regulatory arm of the immune response and hence their own persistence

Wound Complications Following Resection of Adductor Compartment Tumours

Purpose Limb salvage surgery of soft tissue sarcomas is associated with both a risk of local recurrence and wound complications. Although the lower limb appears to be at greater risk of wound-related morbidity, few studies separate anatomical compartments. We believe that the adductor compartment of the thigh has a particularly high rate of complications and so performed a retrospective analysis of all soft tissue sarcomas arising in this region undergoing limb salvage

Evaluation of the effectiveness of play@home

To date there have been very few research trials or evaluations of the effectiveness of family-based Early Years interventions for physical activity promotion. Moreover, previous evaluations of many Early Years physical activity promotion intervention schemes have understandably focused on implementation processes, outputs (e.g. distribution, access to and uptake of programmes) and short-term outcomes (knowledge, skills, abilities) with, at this time, very little evaluation of their longer-term effectiveness. play@home is a physical activity promotion programme for children from birth to five years which promotes interaction and loving touch to encourage bonding between parent and child. The play@home programme has been developed on the philosophy that parents and carers are children's first educators. In this regard parents/carers are considered to have a crucial role to play in encouraging children to develop friendships and interact with situations outside the family home. The programme is not only about what parents/carers can do for children, but just as importantly, what parents/carers can do with their children. The play@home programme is designed to provide parents and carers with activity ideas for playing with their child from the earliest days. Resources are provided to parents, including three books for the target ages of 0-1 years, 1-3 years, and 3-5 years with inexpensive, easy-to-follow ideas and activities that assist parents with the challenges of parenthood and childcare. The books include activities for babies and children to stimulate their curiosity, imagination and creativity and influence overall development through play activities, movement to music and interaction with other children and adults. The resources are designed to (i) provide parents and carers with free information and guidance, (ii) encourage children's enjoyment of physical activity and play from an early age, (iii) encourage communication through talking and listening, (iv) develop body awareness and promote the development of physical movement, coordination and motor skills, (v) promote the value of social interaction and stimulus so that children learn to interact socially and communicate, and (vi) promote the value of physical touch and positive reassurance.sch_phypub2658pu

The Characterization of Ribosomal RNA Gene Chromatin from Physarum Polycephalum

We have isolated ribosomal RNA gene (rDNA) chromatin from Physarum polycephalum using a nucleolar isolation procedure that minimizes protein loss from chromatin and, subsequently, either agarose gel electrophoresis or metrizamide gradient centrifugation to purify this chromatin fraction (Amero, S. A., Ogle, R. C., Keating, J. L., Montoya, V. L., Murdoch, W. L., and Grainger, R. M. (1988) J. Biol. Chem. 263, 10725-10733). Metrizamide-purified rDNA chromatin obtained from nucleoli isolated according to the new procedure has a core histone/DNA ratio of 0.77:1. The major core histone classes comigrate electrophoretically with their nuclear counterparts on Triton-acid-urea/sodium dodecyl sulfate two-dimensional gels, although they may not possess the extent of secondary modification evident with the nuclear histones. This purified rDNA chromatin also possesses RNA polymerase I activity, and many other nonhistone proteins, including two very abundant proteins (26 and 38 kDa) that may be either ribonucleoproteins or nucleolar matrix proteins. Micrococcal nuclease digestion of the metrizamide-purified rDNA chromatin produces particles containing 145-base pair DNA fragments identical in length to those in total chromatin and which contain both transcribed and nontranscribed rDNA sequences. Some smaller fragments (30, 70, and 110 base pairs) are also seen, but their sequence content is not known. These particles sediment uniformly at 11 S in sucrose gradients containing 15 mM NaCl, and at 4-11 S in gradients containing 0.35 M NaCl. Particles enriched in gene or nontranscribed spacer sequences are not resolved in these sucrose gradients or in metrizamide gradients. Our findings suggest that the rDNA chromatin fraction we have identified contains transcriptionally active genes and that an organized, particle-containing structure exists in active rDNA chromatin

The Purification of Ribosomal RNA Gene Chromatin from Physarum Polycephalum

We have undertaken the purification of ribosomal RNA gene (rDNA) chromatin from the slime mold Physarum polycephalum, in order to study its chromatin structure. In this organism rDNA exists in nucleoli as highly repeated minichromosomes, and one can obtain crude chromatin fractions highly enriched in rDNA from isolated nucleoli. We first developed a nucleolar isolation method utilizing polyamines as stabilization agents that results in a chromatin fraction containing far more protein than is obtained by the more commonly used divalent cation isolation methods. The latter method appears to result in extensive histone loss during chromatin isolations. Two methods were then used for purifying rDNA chromatin from nucleoli isolated by the polyamine procedure. We found that rDNA chromatin migrates as a single band in agarose gels, well separated from other components in the chromatin preparation. Although the utility of this technique is somewhat limited by low yields and by progressive stripping of protein from rDNA chromatin, it can provide useful information about rDNA chromatin protein composition. The application of this technique to the fractionation of gene and spacer chromatin fragments produced by restriction enzyme digestion is discussed. We also found that rDNA chromatin, if RNase-treated, bands discretely in metrizamide equilibrium density gradients with a density lighter than that of non-nucleolar chromatin. These characteristics suggest that we have identified a transcriptionally active rDNA chromatin fraction which possesses a lower protein to DNA ratio than does non-nucleolar chromatin. This technique yields sufficient purified rDNA chromatin for further biochemical studies and does not cause extensive protein stripping. The procedures developed here should be applicable to the analysis of a variety of chromatin fractions in other systems

Assessment of a Siloxane Poly(Urethane‐Urea) Elastomer Designed for Implantable Heart Valve Leaflets

Synthetic polymer leaflets in prosthetic cardiac valves hold the potential to reduce calcification and thrombus, while improving blood flow, durability, and device economics. A recently developed siloxane poly(urethane‐urea) (LifePolymer™, LP) exhibits properties essential for heart valve leaflets, including low dynamic modulus, high tensile strength, minimal creep, and excellent biostability. LP properties result from carefully designed “linked co‐macrodiol” chemistry that maximizes silicone content and virtual crosslinks between soft and hard phases. Characterization of multiple commercial batches demonstrates a robust synthesis process with minimal variation. Extensive ISO 10993‐based biocompatibility testing resulted in no observable toxicity or other adverse reactions. An ex vivo AV shunt thrombogenicity investigation revealed nearly undetectable levels of platelet attachment and thrombus formation on LP surfaces. Chronic ovine implantation of prototype heart valves with LP leaflets showed no differences in thrombogenicity or systemic tissue response when compared to a clinically standard tissue‐based valve. Toxicological risk assessment, based on extractables and leachables analysis of LP‐based heart valves, confirmed minimal toxicological risk. Lastly, 24‐week, strain‐accelerated in vivo LP biostability testing confirmed previous favorable in vitro biostability findings. These studies demonstrate that this newly developed elastomer exhibits ideal biomaterial properties for the flexible leaflets of a totally synthetic heart valve replacement

Prospective Study of Antibiotic Prophylaxis for Prostate Biopsy Involving >1100 Men

We aimed to compare infection rates for two 3-day antibiotic prophylaxis regimens for transrectal ultrasound-guided prostate biopsy (TRUSgbp) and demonstrate local microbiological trends. In 2008, 558 men and, in 2009, 625 men had TRUSgpb. Regimen 1 (2008) comprised 400 mg Ofloxacin immediately before biopsy and 200 mg 12-hourly for 3 days. Regimen 2 (2009) comprised Ofloxacin 200 mg 12-hourly for 3 days commencing 24 hours before biopsy. 20/558 (3.6%) men had febrile episodes with regimen 1 and 10/625 (1.6%) men with regimen 2 (P = 0.03). E. coli was the most frequently isolated organism. Overall, 7/13 (54%) of positive urine cultures were quinolone resistant and (5/13) 40% were multidrug resistant. Overall, 5/9 (56%) patients with septicaemia were quinolone resistant. All patients were sensitive to Meropenem. There was 1 (0.2%) death with regimen 1. Commencing Ofloxacin 24 hours before TRUSgpb reduced the incidence of febrile episodes significantly. We observed the emergence of quinolone and multidrug-resistant E. coli. Meropenem should be considered for unresolving sepsis