Biomedical subjects

Edward J Wood

Publications and source records attributed to Edward J Wood.

5 recordsLinked to original sources

PubMed2005

Involvement of protein kinase C in chitosan glutamate-mediated tight junction disruption.

Chitosan has been successfully used as an excipient for trans-epithelial drug delivery systems. It is known to transiently open intercellular tight junctions thus increasing the permeability of an epithelium. In order to investigate the possible role of protein kinases in trans-epithelial delivery, changes in trans-epithelial electrical resistance ('TEER') of epithelial (Caco-2) cell monolayers were assessed in response to chitosan glutamate treatment, in the presence and absence of specific protein kinase inhibitors. Changes in subcellular localisation of the tight junction protein ZO-1 observed by immunofluorescence and western blotting of cellular fractions were also assessed. Inhibition of protein kinase C (PKC), but not mitogen activated protein kinase (MAPK) was found to prevent the chitosan-mediated decrease in TEER, and changes in localisation of ZO-1. In order to determine which PKC isozymes were responsible for the chitosan-mediated tight junction disruption, the activation of the PKC isozymes alpha, beta and delta was investigated. A chitosan-mediated translocation of PKC alpha but not PKC beta or delta from the cytosol to the membrane fraction, indicative of PKC alpha activation was observed. Thus, treatment of Caco-2 cells with chitosan may result in the activation of PKC-dependent signal transduction pathways which affect tight junction integrity.

Animals↗

PubMed2004

Interference by anti-cancer chemotherapeutic agents in the MTT-tumor chemosensitivity assay.

BACKGROUND: One of the major goals of oncology is to predict the response of patients with cancer to chemotherapeutic agents by employing laboratory methods variously called 'tumor chemosensitivity assays', 'drug response assays', or 'drug sensitivity assays', in vitro. The MTT assay is one of the methods used to predict the drug response in malignancies. However, it may suffer from interference by the anticancer drugs with the MTT assay. METHODS: The MTT assay, a colorimetric viability assay, was checked in a cell-free system in terms of its possible chemical interactions with 22 different anticancer drugs. RESULTS: It was found that epirubicine, paclitaxel, doxetaxel, and cisplatin caused a relatively significant increase in absorbance values, resulting in the MTT assay giving rise to false results (untrue increase in viability) although most of the drugs tested did not seem to cause any significant change. CONCLUSIONS: It was concluded that before employing the MTT assay, drugs (or any kind of substances) to be included in the assay should be checked first in terms of possible chemical interactions with MTT, otherwise it may be impossible to evaluate the MTT viability assay results correctly.

Antineoplastic Agents↗

PubMed2004

Problem-based learning.

Problem-based learning has been used in medical school in a number of different countries around the world for over 50 years, with both undergraduate and graduate students. Instead of the traditional lectures, laboratory practical classes and tutorial system of education, students in small groups are presented with a problem that they must try to solve. They are assisted by a 'facilitator' who helps them formulate the problem and generally advises them but does not supply information. The students have to decide what information they need to solve the problem, find it and communicate it to the others in the group. At this stage a solution may be apparent, but several more group discussions to reformulate the problem followed by re-iterations of the information seeking process may be needed before a solution can be found. The theory is that because information is sought and presented in a relevant context, it is valued and is more likely to be remembered. At the end of the session student reflect on how they performed. Problem-based learning has been criticised from a number of points of view, especially that it does not present a coherent curriculum, the curriculum is not necessarily 'covered', and that in many medical schools the implementation has been less than optimal.

Curriculum↗

PubMed2002

Characterization of the living skin equivalent as a model of cutaneous re-epithelialization.

The living skin equivalent, a three-dimensional organotypic model, has been widely used to investigate many aspects of cutaneous biology. However, there are relatively few studies assessing how faithfully the skin equivalent reproduces normal skin biology. The skin equivalent was fabricated by seeding human epidermal keratinocytes onto the upper surface of a hydrated collagen lattice populated with human dermal fibroblasts and subsequently raised to the air-liquid interface where keratinocyte stratification and differentiation led to the formation of a tissue which showed many common morphological features to that of normal skin. Histology and immunohistochemical detection of keratinocyte integrins and matrix metalloproteinases (MMPs) were used as cytological markers to assess the accuracy of the model during cutaneous re-epithelialization. Analysis of expression of keratinocyte integrins revealed that whilst there were a number of similarities to normal skin, skin equivalent keratinocytes appeared to be 'activated' and hyper-proliferating. Wounding of the skin equivalent, by complete bisection, induced re-epithelialization from both wound edges within 8-12 h, which completely restored the epidermis within 4 days. This migration, like that in vivo, was associated with nascent expression of MMPs and upregulation of certain integrins. However, whilst integrin expression, was similar to in vivo re-epithelialization, there were subtle differences in the level of expression and distribution of certain integrins.

Humans↗

PubMed2002

The effect of chitin and chitosan on fibroblast-populated collagen lattice contraction.

The effects of chitin [(1-->4)-2-acetamido-2-deoxy-beta-D-glucan] and its partially deacetylated derivatives, chitosans, on the human dermal fibroblast-mediated contraction of collagen lattices were examined in vitro as a model for the contraction of cutaneous wounds in vivo. Chitosan CL313A, a short-chain-length 89% deacetylated chitosan chloride, inhibited fibroblast-populated collagen lattice (FPCL) contraction at higher initial concentrations (500 and 1,000 microg/ml) in FPCLs fabricated with responsive dermal fibroblasts, while in FPCLs containing non-responsive fibroblasts inhibition of contraction was reduced. The responsive and non-responsive phenotype of human dermal fibroblasts to treatment with chitosan CL313A has been reported previously by us. The inhibition of fibroblast-mediated collagen lattice contraction by chitosan appeared to be strongly correlated with whether the cells were responsive or non-responsive. The effect of chitin-50A on fibroblast-mediated collagen lattice contraction was also examined to investigate whether the level of deacetylation was important for its inhibitory effect on contraction. However, this had no effect on contraction at the concentrations tested, supporting previous work that only chitosan samples with higher levels of deacetylation showed any biological activity. This work indicates that highly deacetylated chitosan inhibits fibroblast-mediated contraction of collagen lattices and may therefore be useful as a therapeutic agent to reduce contraction and therefore scarring in wound healing in vivo.

Animals↗