Publications by authors named "Penny Johnson"

Article Synopsis
  • Andexanet alfa is a medication used to reverse the effects of FXa inhibitors like apixaban, but its impact on blood clotting and fibrinolysis hasn't been thoroughly studied.
  • In experiments with plasma and blood from healthy volunteers, increasing levels of apixaban were shown to slow down thrombin generation and thrombus formation, while the addition of GDXa (a modified FXa analog) helped counteract these effects.
  • Results suggested that GDXa can effectively reverse coagulation delays caused by apixaban, but its effect on fibrinolysis was limited, indicating that FXa still plays a role in generating plasmin despite apixaban's inhibition at high concentrations.
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Homeless people have complex problems. GP enhanced care (Pathway) has shown benefits. We performed a randomised, -parallel arm trial at two large inner city hospitals.

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Background: The epidermal growth factor receptor family is expressed in breast cancer, and agents targeting this pathway have single agent effects (e.g. traztuzumab).

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Low-trophic level species account for more than 30% of global fisheries production and contribute substantially to global food security. We used a range of ecosystem models to explore the effects of fishing low-trophic level species on marine ecosystems, including marine mammals and seabirds, and on other commercially important species. In five well-studied ecosystems, we found that fishing these species at conventional maximum sustainable yield (MSY) levels can have large impacts on other parts of the ecosystem, particularly when they constitute a high proportion of the biomass in the ecosystem or are highly connected in the food web.

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Background: Chemotherapy benefits relatively few patients with cutaneous melanoma. The assessment of tumour chemosensitivity by the ATP-based tumour chemosensitivity assay (ATP-TCA) has shown strong correlation with outcome in cutaneous melanoma, but requires fresh tissue and dedicated laboratory facilities.

Aim: To examine whether the results of the ATP-TCA correlate with the expression of genes known to be involved in resistance to chemotherapy, based on the hypothesis that the molecular basis of chemosensitivity lies within known drug resistance mechanisms.

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The metanephros is formed from the reciprocal inductive interaction of two precursor tissues, the metanephric mesenchyme (MM) and the ureteric bud (UB). The UB induces MM to condense and differentiate forming the glomerulus and renal tubules, whilst the MM induces the UB to differentiate into the collecting tubules of the mature nephron. Uninduced MM is considered the progenitor cell population of the developing metanephros because of its potential to differentiate into more renal cell types than the UB.

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Background: NSCLC exhibits considerable heterogeneity in its sensitivity to chemotherapy and similar heterogeneity is noted in vitro in a variety of model systems. This study has tested the hypothesis that the molecular basis of the observed in vitro chemosensitivity of NSCLC lies within the known resistance mechanisms inherent to these patients' tumors.

Methods: The chemosensitivity of a series of 49 NSCLC tumors was assessed using the ATP-based tumor chemosensitivity assay (ATP-TCA) and compared with quantitative expression of resistance genes measured by RT-PCR in a Taqman Array following extraction of RNA from formalin-fixed paraffin-embedded (FFPE) tissue.

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Embryonic stem (ES) cells are thought to have unique chromatin structures responsible for their capacity for self-renewal and pluripotency. To examine this possibility, we sought nuclear proteins in mouse ES cells that specifically bind to histones using a pull-down assay with synthetic peptides of histone H3 and H4 tail domain as baits. Nuclear proteins preferentially bound to the latter.

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Aim: To design and manufacture an investigational living skin graft replacement (ICX-SKN) that is able to incorporate into the host, providing healing by primary intent without the need for a second intervention.

Materials & Methods: The ICX-SKN skin graft replacement has been designed as an allogeneic dermal substitute comprising an extracellular matrix composed largely of human collagen and human dermal fibroblast cells (HDFs). ICX-SKN is first formed by casting a provisional matrix of fibrin, into which HDFs are seeded.

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Aim: To present the first human clinical data on an investigational living skin graft replacement that is being designed for application where tissue has been lost through surgery, disease or trauma.

Materials & Methods: The ICX-SKN skin graft replacement is composed of an autosynthesized human collagen-based extracellular matrix and human dermal fibroblasts. In a first study to examine integration and persistence, full-thickness excisional wounds were made in six healthy human female volunteers and the ICX-SKN skin graft replacement applied and dressed.

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Background: Uveal melanoma arises in an immune-privileged site and can itself add to the immunosuppressive environment. Previous studies on cutaneous melanoma have shown the presence of tolerogenic dendritic cells (DCs), which could play an important role in the progression of the tumour.

Aim: To examine the presence and functional status of DCs in a small series of uveal melanomas.

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Background: Leukotrienes derived from the 5-lipoxygenase pathway are proinflammatory lipid mediators that possibly play a role in inflammatory bowel diseases. The expression of 5-lipoxygenase pathway proteins has not previously been examined in colonic mucosa in inflammatory bowel disease.

Results: Quantitative immunohistochemical analyses showed that, compared to those of the control subjects (n = 9), colonic biopsies from patients with active inflammatory bowel disease (n = 17) had 3- to 7-fold higher mean counts of cells expressing 5-lipoxygenase (P = 0.

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Background: COX-2 expression in tumour cells has been associated with poor prognosis in gastrointestinal and non-gastrointestinal cancers. The aim of our study was to test the hypothesis that higher levels of COX-2 expression are prognostically related to poor clinico-pathologic features in adenocarcinoma of the oesophagus.

Methods: We reviewed the records of 100 consecutive patients undergoing resection for adenocarcinoma of the oesophagus to collect data on T-stage, N-stage, tumour recurrence and survival.

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Background: Tumor resistance to chemotherapy may be present at the beginning of treatment, develop during treatment, or become apparent on re-treatment of the patient. The mechanisms involved are usually inferred from experiments with cell lines, as studies in tumor-derived cells are difficult. Studies of human tumors show that cells adapt to chemotherapy, but it has been largely assumed that clonal selection leads to the resistance of recurrent tumors.

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Immune avoidance mechanisms play a key role in the successful dissemination of melanoma. One mechanism whereby this could be achieved is by interfering with dendritic cell (DC) presentation of tumour-associated antigens to naïve T cells. In particular, immature DCs characterized by the absence of accessory molecules are known to be immunosuppressive and to be involved in the induction of tolerance.

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Background: Activation of the epidermal growth factor receptor (EGFR) triggers downstream signaling pathways that regulate many cellular processes involved in tumour survival and growth. Gefitinib ('Iressa') is an orally active tyrosine kinase inhibitor (TKI) targeted to the ATP-binding domain of EGFR (HER1; erbB1).

Methods: In this study we have used a standardised ATP-based tumour chemosensitivity assay (ATP-TCA) to measure the activity of gefitinib alone or in combination with different cytotoxic drugs (cisplatin, gemcitabine, oxaliplatin and treosulfan) against a variety of solid tumours (n = 86), including breast, colorectal, oesophageal and ovarian cancer, carcinoma of unknown primary site, cutaneous and uveal melanoma, non-small cell lung cancer (NSCLC) and sarcoma.

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The expression of P-glycoprotein (P-gp) has been demonstrated to confer resistance to several anticancer drugs, including anthracyclines, taxanes and vinca alkaloids. Tariquidar is a novel inhibitor of P-gp that has been shown to reverse resistance to cytotoxic drugs in tumor cell lines and mouse xenografts. We have used an ATP-based chemosensitivity assay (ATP-TCA) to compare the activity of cytotoxic drugs in combination with tariquidar against a variety of solid tumors (n = 37).

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Somatic cell reprogramming holds great promise for the development of novel cellular therapeutics. A number of sources of reprogramming potential have been identified, including oocytes, embryonic germ (EG) cells and embryonic stem (ES) cells. However, each of these sources of reprogramming factors is problematic, since they are either not freely available or have special growth requirements.

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The mechanisms by which the progression of eukaryotic replication forks is controlled after DNA damage are unclear. We have found that fork progression is slowed by cisplatin or UV treatment in intact vertebrate cells and in replication assays in vitro. Fork slowing is reduced or absent in irs1SF CHO cells and XRCC3(-/-) chicken DT40 cells, indicating that fork slowing is an active process that requires the homologous recombination protein XRCC3.

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Mucosal changes in inflammatory bowel disease (IBD) are characterized by ulcerative lesions accompanied by prominent cellular infiltrates in the bowel wall. Chemokines are chemotactic cytokines that are able to promote leukocyte migration to areas of inflammation and are also able to initiate cell activation events. They have recently been implicated in the pathophysiology of many disease states.

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