J. E. Dyson

DNA aneuploidy in colorectal adenomas.

The frequency of DNA aneuploidy was investigated by flow cytometry in 156 colorectal adenomas including 56 associated with 36 synchronous adenocarcinomas. Nine of 156 adenomas (6%) were DNA aneuploid. DNA aneuploidy correlated with increasing size (P less than 0.005) and histopathological type P less than 0.05) but not with dysplasia. Adenomas in associated with a synchronous adenocarcinoma did not have an increased incidence of DNA aneuploidy. Adenocarcinomas found in association with adenomas tend to have a lower incidence of DNA aneuploidy then the generality of colorectal cancers.

Kinetic and physical studies of cell death induced by chemotherapeutic agents or hyperthermia.

The kinetics of three physical parameters: cell density, relative cytoplasmic viscosity and DNA stability to denaturation have been measured during the period preceding cell death induced by hyperthermia, methylprednisolone and a series of cancer chemotherapeutic agents. This series of measurements employed cultured human lymphoblastoid cells as an experimental system to establish the changes that can be observed in the early stages of cell death, prior to applying such measurements to tissue biopsies from solid human tumours. Cell death, induced by hyperthermia up to 43°C, methylprednisolone, vincristine, 5‐fluorouracil, BCNU and melphalan, showed essentially identical and reproducible changes corresponding to those which characterize programmed cell death (apoptosis). Such changes could also be observed following hyperthermia above 43°C, but reproducibility was poor and increasing damage to the cell membranes was evident. In cells treated with adriamycin or methotrexate, cell sub‐populations showing an increase in cell density were not detected. Measurements of DNA stability were readily performed by flow cytofluorometry thus allowing rapid quantitation of the fraction of cells in the early stages of cell death. Modified flow cytometric instrumentation would further allow measurement of cytoplastic viscosity as an additional parameter to indicate entry into programmed cell death. This suggests that these measurements could readily be applied to cell suspensions derived from tumour tissue biopsies for a more accurate assessment of tumour growth rate, and to allow monitoring of response to therapy in sequential tumour biopsies.

Is DNA aneuploidy a good prognostic indicator in patients with advanced colorectal cancer

There is increasing evidence that abnormalities of cellular DNA within primary tumours are of prognostic significance. Deviation from the normal diploid DNA content of tumour cells has been associated with a poorer prognosis in carcinomas of the breast (Friedlander et al., 1984a), ovary (Friedlander et al., 1984b) and colon (Wolley et al., 1982). However, in the more advanced stages of malignant disease the association between DNA aneuploidy and prognosis does not appear to be so prominent (Hedley et al., 1985). With the current resurgence of interest in various forms of therapy for liver metastases from primary colorectal cancer e.g. hepatic resection, regional or systemic chemotherapy, hepatic arterial ligation and hepatic irradiation, it is of importance to assess the various prognostic factors that may influence the natural history. Several workers have identified a variety of indices which may be of use in assessing survival or for stratification within controlled clinical trials (Goslin et al., 1982; Lahr et al., 1983; Finan et al., 1985). In order to assess the value of ploidy in patients with advanced colorectal disease, we have studied a series of patients presenting with synchronous hepatic metastases from primary colorectal cancer whose survival has been documented and in whom the primary tumour was suitable for measurement of DNA content. Ploidy has then been compared with other well recognised prognostic variables. From a retrospective study of 94 patients with colorectal cancer and synchronous hepatic metastases presenting to the two major teaching centres in Leeds over the period 1976-80,46 cases, in whom the primary tumour was suitable for cellular DNA measurement, were selected. Clinical details of these patients are included in Table I. A standard proforma was completed for each patient recording personal details, symptoms and physical signs referrable to both the primary lesion and distant metastases, the results of pre-operative

Flow cytofluorometric evidence for the differential radioresponsiveness of aneuploid and diploid cervix tumours

We are presently involved in a prospective study of the relationship between DNA content profiles, and their changes during treatment, determined by flow cytofluorometry, and patient prognosis and response to therapy for cancer of the uterine cervix. To date, 348 patients have been included in the study over a 54-month period. Data on these patients have shown that DNA aneuploid tumours are significantly more radioresponsive than diploid cervix tumours. Analysis of the data on 213 patients with a minimum follow-up time of 15 months has, however, failed to show an overall more favourable prognosis conferred by tumour DNA aneuploidy. Analysis of the relationship between clinical stage and disease state and tumour DNA ploidy, however, suggests that aneuploid tumours metastasize to distant sites at an earlier stage of the disease than diploid tumours and local recurrence rates for diploid tumours, in late stage disease, are double those for aneuploid tumours. Improved staining procedures, and instrument modification, has also shown that cervix tumour heterogeneity is of considerably greater frequency than at first appeared to be the case (approximately 75% of DNA aneuploid tumours show heterogeneity.

The turbulent destruction of clouds – I. A k–ε treatment of turbulence in 2D models of adiabatic shock–cloud interactions

The interaction of a shock with a cloud has been extensively studied in the literature, where the effects of magnetic fields, radiative cooling and thermal conduction have been considered. In many cases, the formation of fully developed turbulence has been prevented by the artificial viscosity inherent in hydrodynamical simulations. This problem is particularly severe in some recent simulations designed to investigate the interaction of a flow with multiple clouds, where the resolution of individual clouds is necessarily poor. Furthermore, the shocked flow interacting with the cloud has been assumed to be completely uniform in all previous single-cloud studies. In reality, the flow behind the shock is also likely to be turbulent, with non-uniform density, pressure and velocity structure created as the shock sweeps over inhomogeneities upstream of the cloud (as seen in recent multiple cloud simulations). To address these twin issues we use a subgrid compressible k–� turbulence model to estimate the properties of the turbulence generated in shock–cloud interactions and the resulting increase in the transport coefficients that the turbulence brings. A detailed comparison with the output from an inviscid hydrodynamical code puts these new results into context. Despite the above concerns, we find that cloud destruction in inviscid and k–� models occurs at roughly the same speed when the post-shock flow is smooth and when the density contrast between the cloud and intercloud medium, χ 100. However, there are increasing and significant differences as χ increases. The k–� models also demonstrate better convergence in resolution tests than inviscid models, a feature which is particularly useful for multiple-cloud simulations. Clouds which are over-run by a highly turbulent post-shock environment are destroyed significantly quicker as they are subject to strong ‘buffeting’ by the flow. The decreased lifetime and faster acceleration of the cloud material to the speed of the ambient flow leads to a reduction in the total amount of circulation (vorticity) generated in the interaction, so that the amount of vorticity may be self-limiting. Additional calculations with an inviscid code where the post-shock flow is given random, grid-scale, motions confirm the more rapid destruction of the cloud. Our results clearly show that turbulence plays an important role in shock–cloud interactions, and that environmental turbulence adds a new dimension to the parameter space which has hitherto been studied.

Quantitation by flow cytofluorometry of response of tumours of the uterine cervix to radiotherapy.

We are presently involved in a project to investigate the use of flow cytofluorometry in assessing, by means of serial biopsies, the response to radiotherapy of tumours of the uterine cervix. This technique enables changes in the DNA content profiles and content of proliferating cells in the tumour biopsies to be determined at intervals as therapy progresses. A means has been devised to quantitate the content of hyperdiploid cells, hypertetraploid cells, and dead and dying cells, by computer analysis of DNA vs. RNA scattergrams obtained by flow cytofluorometric analysis. Plotting of these parameters for the serial biopsies vs. time since start of tumour irradiation presents a graphical indication of the response of the tumour to irradiation. Over 100 patients (stage Ib and IIa) have been followed during intracavitary (Cathetron) therapy with parallel flow cytofluorometric analysis and histopathological assessment of serial biopsies. Patterns are beginning to emerge from these analyses which promise to indicate within 14-21 days and sometimes earlier the extent of radioresponsiveness of the tumour. These patterns may also be of assistance in planning modified dose fractionation schedules to obtain improved therapeutic ratios.

The evolution of mass loaded supernova remnants - I. Constant and Mach Number dependent mass injection rates

We describe the evolution of spherically symmetric supernova remnants in which mass addition takes place from embedded clouds. We derive simple approximations to the remnant evolution which can be used for investigating the generation of supernova induced phenomena such as galactic superwinds.

Flow cytofluorometric analysis of serial biopsies of tumours of the uterine cervix

The technique of flow cytofluorometry has been employed to assess, by means of cell suspensions prepared from serial biopsies, the radioresponsiveness of tumours of the uterine cervix. This enables DNA profiles and content of proliferating cells to be determined prior to treatment and during external beam and intracavitary therapy. Results show that elimination of hyperdiploid and hypertetraploid cells and reduction in the proliferating fraction of cells can readily be monitored by this method during therapy. This information, quickly available during treatment, may assist in estimating radioresponsiveness of the tumour and possible prognosis for the patient. Dose fractionation schedules may also be adjusted according to tumour response to therapy. Our results, however, show no relationship between histopathological classification of a tumour (WHO) and its ploidy state. The advanced stages of the disease (II and III) do, however, show an increased content of hypertetraploid cells in the tumour biopsies.

The modification by diffuse radiation of "cometary tail" formation behind globules

We study the evolution of a globule of neutral material immersed in the more tenuous hotter plasma of an H II region surrounding newly born OB stars. The neutral globule is illuminated by the direct ionizing radiation of OB stars, and by diffuse radiation emitted by recombination in the surrounding ionized gas. We perform 2D, time dependent axisymmetric hydrodynamic simulations, and find that, for values of the diffuse field of the order of 10% of the direct field, the evolution of the globule is completely different to its evolution when the diffuse field is neglected.

The effect of sodium butyrate on the growth characteristics of human cervix tumour cells

Sodium butyrate has been shown to affect cell proliferation, and, at concentrations above approximately 0.5 mM, to cause cell death in some tumour cell lines. When combined with cytotoxic drugs increase in chemosensitivity has been observed. We are presently carrying out a study of the combined effects of sodium butyrate and cytotoxic drugs on cultured cervix tumour cells. To provide a baseline for this study we have carried out a systematic investigation of the effects of sodium butyrate alone on the growth characteristics of cervix tumour cells cultured as multicell spheroids. This has shown that concentrations of n-butyrate of 0.005 mM to 0.50 mM decrease cell proliferation without inducing cell death, the effect increasing with increasing concentration. Butyrate concentrations greater than 0.50 mM cause cell death after a period of 5 to 15 days exposure, dependent on concentration. Concentrations of 0.010 mM and above cause fragmentation of, and increased cell shedding from, multicell spheroids, suggesting an effect on the cell surface. Concentrations of butyrate greater than 0.10 mM cause a considerable increase in the synthesis of cytokeratin, as shown by reaction with cytokeratin antibody. Correlated with this is a marked increase in cell size, concentrations of butyrate of 2.0 or 3.0 mM leading to an approximate doubling of cell diameter, followed by cell disintegration. The effects of butyrate less than 0.25 mM are readily reversible. At concentrations greater than 0.25 mM the effects are reversible up to a limit of about 7 to 20 days depending on concentration, even when cytokeratin synthesis has been induced.