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Philip Thomas

Publications and source records attributed to Philip Thomas.

23 records · Page 2Linked to original sources
PubMed2003

Nucleoplasmic bridges are a sensitive measure of chromosome rearrangement in the cytokinesis-block micronucleus assay.

We have performed experiments using the WIL2-NS human B lymphoblastoid cell line and primary human lymphocytes to: (i). determine the importance of including measurements of nucleoplasmic bridges (NPB) in the cytokinesis-block micronucleus (CBMN) assay; (ii). provide evidence that NPB originate from dicentric chromosomes and centric ring chromosomes. In addition, we describe theoretical models that explain how dicentric chromosomes and centric ring chromosomes may result in the formation of NPB at anaphase. The results with WIL2-NS showed that it was possible to distinguish genotoxic effects induced by different oxidizing agents in terms of the NPB/micronucleus frequency ratio. The results with lymphocytes indicated a strong correlation: (i). between NPB, centric ring chromosomes and dicentric chromosomes in metaphases (r > 0.93, P < 0.0001); (ii). between micronuclei (MNi), acentric chromosome fragments and acentric ring chromosomes (r > 0.93, P < 0.0001). The dose-response curves with gamma-rays were very similar for NPB, ring chromosomes and dicentric chromosomes, as were the dose-response curves for MNi, acentric rings and fragments. However, not all acentric chromosomes and dicentric chromosomes/centric rings were converted to MNi and NPB respectively, depending on the dose of radiation. Preliminary data, using FISH, suggest that NPB often represent DNA from a structural rearrangement involving only one or two homologous chromosomes. The results from this study validate the inclusion of NPB in the CBMN assay which provides a valuable measure of chromosome breakage/rearrangement that was otherwise not available in the micronucleus assay. The CBMN assay allows NPB measurement to be achieved reliably because inhibition of cytokinesis prevents the loss of NPB that would otherwise occur if cells were allowed to divide.

Cell Division↗
PubMedDate not supplied

HEK293 cell line: a vehicle for the expression of recombinant proteins.

The HEK cell line has been extensively used as an expression tool for recombinant proteins since it was generated over 25 years ago. Although of epithelial origin, its biochemical machinery is capable of carrying out most of the post-translational folding and processing required to generate functional, mature protein from a wide spectrum of both mammalian and non-mammalian nucleic acids. Though popular as a transient expression system, this cell type has also seen wide use in stably transfected forms (i.e. transformed cells) to study a variety of cell-biological questions in neurobiology. The principal attributes which have made the HEK cell a popular choice among electrophysiologists to study isolated receptor channels include; its quick and easy reproduction and maintenance; amenability to transfection using a wide variety of methods; high efficiency of transfection and protein production; faithful translation and processing of proteins; and small cell size with minimal processes appropriate for voltage-clamp experimentation. These, and other attributes, also mean that complementary biochemical/cell biological evaluations of expressed proteins can be performed in concert with functional analyses to establish detailed pharmacological and biophysical profiles for the action of new drugs and their targets. The increased amount of sequence information available from the human genome has placed greater emphasis upon heterologous cell expression systems as targets for high throughput structure-function evaluation of novel drug targets and disease markers. Here we have highlighted some of the innate characteristics of the HEK cell in order that its suitability as a vehicle for the expression of a gene product can be assessed for particular needs. We have also detailed some of the standard methods used for transfection and obtaining functional data from electrophysiological recording techniques.

Cell Line↗
PubMedDate not supplied

Hearing voices: A phenomenological-hermeneutic approach.

The word "phenomenology" has a number of meanings. In this paper we briefly contrast the different meanings of the word in psychiatry and philosophy. We then consider the work of the philosophers Heidegger and Merleau-Ponty, as examples of what Hubert Dreyfus calls ontological phenomenology, in contrast to an epistemological approach. We present a brief outline of Merleau-Ponty's theory of embodiment, and contrast this with the dominant, epistemological (or Cartesian) view of experience. Through the example of a woman who experienced bereavement hallucinations, we try to show how this approach can open up a hermeneutic approach to the experience of hearing voices. An understanding of embodiment can help to counter reductionism, whether biological or social, and dualism (body/mind and mind/society). It is only when we consider the totality of human experience that we can understand its meaning. This has two main benefits. First, it legitimates the claims made by those who hear voices that their experiences are intrinsically meaningful. Second, it can provide a framework for those who work with voice hearers and who are interested in understanding these experiences. In this sense, phenomenology can become a valuable clinical tool.

Journal Article↗