Biomedical subjects

David P Jackson

Publications and source records attributed to David P Jackson.

5 recordsLinked to original sources

PubMed2004

Adhesion phenomena in ferrofluids.

One efficient way of determining the bond strength of adhesives is to measure the force or the work required to separate two surfaces bonded by a thin adhesive film. We consider the case in which the thin film is not a conventional adhesive material but a high viscosity ferrofluid confined between two narrowly spaced parallel flat plates subjected to an external magnetic field. Our theoretical results demonstrate that both the peak adhesive force and the separation energy are significantly influenced by the action and symmetry properties of the applied field. Specifically, we show that the adhesive strength of a ferrofluid is reduced if the applied magnetic field is perpendicular to the plates or if the applied field is in plane and exhibits azimuthal symmetry. Conversely, the adhesive strength can be either enhanced or reduced if the applied field is in plane and is directed radially outward. This establishes an interesting connection between adhesion and ferrohydrodynamic phenomena, allowing the control of important adhesive properties by magnetic means.

Journal Article↗

PubMed2004

Identification of proteins regulated by interferon-alpha in resistant and sensitive malignant melanoma cell lines.

Treatment of patients with malignant melanoma with interferon-alpha achieves a response in a small but significant subset of patients. Currently, although much is known about interferon biology, little is known about either the particular mechanisms of interferon-alpha activity that are crucial for response or why only some patients respond to interferon-alpha therapy. Two melanoma cell lines (MeWo and MM418) that are known to differ in their response to the antiproliferative activity of interferon-alpha, have been used as a model system to investigate interferon-alpha action. Using a proteomics approach based on two-dimensional polyacrylamide gel electrophoresis and mass spectrometry, several proteins induced in response to interferon-alpha have been identified. These include a number of gene products previously known to be type I interferon responsive (tryptophanyl tRNA synthetase, leucine aminopeptidase, ubiquitin cross-reactive protein, gelsolin, FUSE binding protein 2 and hPNPase) as well as a number of proteins not previously reported to be induced by type I interferon (cathepsin B, proteasomal activator 28alpha and alpha-SNAP). Although the proteins upregulated by interferon-alpha were common between the cell lines when examined at the level of Western blotting, the disparity in the basal level of cathepsin B was striking, raising the possibility that the higher level in MM418 may contribute to the sensitivity of this cell line to interferon-alpha treatment.

Blotting, Western↗

PubMed2003

Orientational preference and predictability in a symmetric arrangement of magnetic drops.

An investigation of a symmetrical arrangement of N quasi-two-dimensional magnetic domains in an external field is carried out. By minimizing the linearized interaction energy for this arrangement using a nearest-neighbor approximation, an orientationally preferred state of the system is found. This orientational preference leads to a large degree of predictability in the final patterns as demonstrated by some experiments using ferrofluids. The final state patterns are also investigated by carrying out a series of numerical simulations. These simulations exhibit a similar predictability and the final patterns bear a strong resemblance to those obtained experimentally.

Journal Article↗

PubMed2003

Controlling fingering instabilities in rotating ferrofluids.

We perform a detailed analytic and numerical study of the evolution of a ferrofluid drop confined to a rotating Hele-Shaw cell in the presence of an azimuthal magnetic field. Our results demonstrate that the centrifugally driven interfacial instabilities can be simply controlled with the use of a current-carrying wire. We compare an analytic linear analysis to our computational results and show that a number of observed features cannot be explained by linear theory alone, including a "diamond ring" instability that results when a droplet is nearly stabilized.

Journal Article↗

PubMed2003

The JAK/STAT pathway is not sufficient to sustain the antiproliferative response in an interferon-resistant human melanoma cell line.

The mechanism of resistance of malignant melanoma to treatment with interferon-alpha is unknown, and currently there is no reliable method of predicting response. Signalling via the JAK/STAT pathway is known to mediate many interferon-regulated events and has been implicated in mediating the antiproliferative response. The objective of this study was to determine whether defects in JAK/STAT signalling may be responsible for interferon resistance. The in vitro response to interferon was determined in a panel of established melanoma cell lines, and the components and functioning of the JAK/STAT pathway were examined in sensitive and resistant cell lines. Two melanoma cell lines, characterized as sensitive (MM418) and resistant (MeWo) to the antiproliferative effect of interferon, were both shown by Western blotting to possess all the protein components of the JAK/STAT pathway, and were shown to be capable of producing functional transcription factors using an electrophoretic mobility shift assay and a ribonuclease protection assay of known interferon-induced genes. In addition, both cell lines had intact antiviral and HLA upregulation responses. These data suggest that there is no defect in the JAK/STAT pathway per se in the MeWo cell line, and that the substantial resistance to interferon must be mediated through components either downstream or additional to this signalling pathway. Others have shown JAK/STAT defects to be responsible for interferon resistance in some melanoma cell lines. However, our results highlight the likely heterogeneity in the mechanisms leading to interferon resistance both in cell lines and tumours, and suggest that a clinical assay based on analysis of components of the JAK/STAT pathway may have only limited use as a predictor of interferon response.

Antineoplastic Agents↗