Search PubMed⌕ Search

Biomedical subjects

E G Wright

Publications and source records attributed to E G Wright.

At least 55 records · Page 3Linked to original sources
PubMed1996

No association between p53 status and alpha-particle-induced chromosomal instability in human lymphoblastoid cells.

Previous work has demonstrated that alpha-particle irradiation of primary human bone marrow cells leads to the transmission of chromosomal instability in the descendants of the irradiated cell, although there is some interindividual variation. We have extended these studies to human EBV-transformed lymphoblastoid cell lines in order to establish an in vitro model system. The five cell lines analyzed, including one from a Fanconi anaemia patient, exhibited high levels of persistent chromatid aberrations up to approximately 40 cell generations after alpha-irradiation. The p53 status of the cell lines was defined according to whether cellular p53 levels were induced by irradiation, translocated to the nucleus and were able to bind a p53 DNA consensus recognition sequence in vitro. Together with the primary bone marrow cell studies, we conclude that alpha-particle induced chromosomal instability is independent of the p53 status of the cell as defined in these studies.

Alpha Particles↗
PubMed1996

Long-term in vivo transmission of alpha-particle-induced chromosomal instability in murine haemopoietic cells.

We have previously reported non-clonal cytogenetic aberrations in the clonal descendants of murine haemopoietic stem cells irradiated in vitro with alpha-particles. The data are consistent with a transmissible chromosomal instability induced in a stem cell resulting in a diversity of aberrations in its clonal progeny many cell divisions later. To determine whether this instability is transmissible in vivo, bone marrow cells obtained from the male mouse have been irradiated with alpha-particles in vitro and transplanted into female recipients. In the repopulated haemopoietic system we have observed persisting chromosomal instability up to 1 year post-transplantation. The findings demonstrate a long-lived effect of the alpha-particle-induced lesion in the donor repopulating stem cells.

Alpha Particles↗
PubMed1996

Radiation-induced genomic instability and persisting oxidative stress in primary bone marrow cultures.

There is accumulating evidence that cells exposed to low and often environmentally relevant doses of ionizing radiation survive the initial insult, but transmit genomic instability to their progeny. The underlying mechanism of radiation-induced genomic instability is unknown. We present bio-chemical evidence consistent with the hypothesis that enhanced and persistent oxy-radical activity may be responsible.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Differentiation and delayed cell death in embryonal stem cells exposed to low doses of ionising radiation.

Embryonal stem cells have been used to study the effects of environmentally relevant doses of radiation on cell death and differentation. The ES cells were found to have a greater than 60% chance of surviving the traversal of a single alpha-particle, the lowest possible dose of high linear energy transfer radiation a cell may receive. The ES cells appeared to possess the cell cycle checkpoints believed to prevent the transmission of the radiation damage. However, delayed effects were observed in the progeny. An increased incidence of apoptosis and haempoietic differentiation capacity was found to persist in the ES cell population over many cell divisions. Since both cell death and differentiation are known to play a key role in tissue kinetics, an ES cell model will provide a valuable and versatile cell system for studying the role of cell death and differentiation in the pathology of radiogenic diseases.

Journal Article↗
PubMed1995

Radiation-induced genomic instability: delayed cytogenetic aberrations and apoptosis in primary human bone marrow cells.

Transmissible chromosomal instability, characterized by non-clonal cytogenetic aberrations with a high frequency of chromatid-type aberrations together with a lower frequency of chromosome-type aberrations, has been demonstrated in the clonal descendants of human haemopoietic stem cells after alpha- but not X-irradiation. Comparable cytogenetic abnormalities have also been demonstrated in non-clonal cultures of alpha-irradiated primary human bone marrow, but a different pattern of delayed aberrations, mainly of chromosome-type, was found after X-irradiation in non-clonal cultures. In clonal analyses, delayed apoptotic cell death was evident after both X- and alpha-irradiation. It is suggested that the type of radiation exposure, the type of cell and its genetically determined susceptibility are factors that may influence the expression of delayed effects of radiation.

Alpha Particles↗
PubMed1994

Alpha-particle-induced chromosomal instability in human bone marrow cells.

alpha-particles, which are ionising radiation of high linear-energy-transfer emitted, for example, from radon or plutonium, pass through tissue as highly structured tracks. Single target cells in the path of the tracks might be damaged by even low-dose alpha-irradiation. We found non-clonal cytogenetic aberrations, characterised by a high frequency of chromatid aberrations with chromosome aberrations, in clonal descendants of haemopoietic stem cells after exposure to alpha-particles of bone marrow cells from two of four haematologically normal individuals (up to 25% abnormal metaphases). The data are consistent with a transmissible genetic instability induced in a stem cell resulting in a diversity of aberrations in its clonal progeny many cell divisions later.

Alpha Particles↗
PubMed1994

Interleukin 7-dependent B lymphocyte precursor cells are ultrasensitive to apoptosis.

We have compared the sensitivity of clonogenic interleukin 7 (IL-7)-dependent murine B cell precursors with that of clonogenic mature B cells and myeloid precursors to alpha-particles from plutonium-238 and X radiation. All three populations are relatively sensitive, but B cell precursors are ultrasensitive. This differential sensitivity is also observed with corticosteroid, etoposide, and cisplatin, all apoptosis-inducing drugs used in the treatment of leukemia and other cancers. Further, we show that x-rays and drugs induce the bulk of the B cell precursor population to undergo rapid apoptosis, despite the continued presence of IL-7. B cell precursors were found to express very low levels of BCL-2 protein compared with mature splenic B cells and their resistance to x-rays and corticosteroid could be enhanced by expression of a BCL-2 transgene. These data have important implications for normal lymphopoiesis and for the behavior of leukemic lymphoid precursor cells.

Alpha Particles↗
PubMed1994

Lethality and mutagenesis of B lymphocyte progenitor cells following exposure to alpha-particles and X-rays.

B lymphocyte precursor cells are the target cells for the major subtype of paediatric cancer, acute lymphoblastic leukaemia. Using a murine IL-7-dependent clonogenic assay for normal B cell precursors as a model, we have investigated the sensitivity of these cells versus other normal and leukaemic haemopoietic cells to alpha-particle radiation. We find that B cell precursors are remarkably susceptible to the lethal effects of alpha-particles and have a very low probability of surviving a single alpha-track. B cell precursors are also very sensitive to the lethal effects of low LET X-rays. The mutation frequency in a marker gene (HPRT) does not, however, appear to be greater in B cell precursors that survive X-radiation than in other haemopoietic cells.

Alpha Particles↗
PubMed1993

Inactivation of haemopoietic stem cells by slow alpha-particles.

Inactivation of murine haemopoietic stem cells, assayed as spleen colony-forming units (CFU-S), has been determined after in vitro irradiation under well defined conditions with small numbers (0.15-3) of alpha-particles of incident energy 3.3 MeV (LET 121 ke V microns-1). Exponential survival curves were obtained with inactivation dose coefficients of 1.83 +/- 0.11 and 1.63 +/- 0.06 Gy-1 for 8 and 12-day CFU-S, respectively, corresponding to inactivation cross sections of 35.6 +/- 2.1 and 31.7 +/- 1.2 microns2. The results indicate that these radiosensitive stem cells have a significant probability of surviving the passage of a single alpha-particle track, estimated at 8 and 18% per particle passage, respectively, if the cells have a diameter of 7 microns. However, this estimation is strongly dependent on the assumed diameter. Conversely, it is demonstrated that the cells cannot have mean geometric diameters of less than 6.7 +/- 0.2 and 6.4 +/- 0.1 microns, respectively. Associated experiments have shown that some cells from the irradiated population do survive to form colonies that express delayed non-clonal chromosome aberrations.

Alpha Particles↗
PubMed1993

Pre-irradiation of tissue culture flasks leads to diminished stem and progenitor cell production in long-term bone marrow cultures.

Empty plastic tissue culture flasks were exposed to X-irradiation doses of 0.3-10.0 Gy, prior to the establishment of long-term bone marrow cultures. During the course of a 10 week culture period, all irradiated plastic flasks exhibited a dramatic decrease in the number of both haemopoietic stem cells and myeloid progenitor cells, in the non-adherent layer, when compared with controls. This decrease was not due to a decrease in the number of non-adherent cells produced. Histological examination of non-adherent cells showed an increase in mature granulocytic cells with few blast cells. Morphologically, the adherent layers of irradiated flasks demonstrated a delay in appearance or absence of fat cell production. X-irradiation of glass tissue culture flasks had no deleterious effect.

Adipose Tissue↗
PubMed1993

Mixed colony formation in vitro by the heterogeneous compartment of multipotential progenitors in human bone marrow.

The physiology of the human haemopoietic primitive progenitor populations can be studied in normal and disease states by clonal in vitro cultures in which the primitive progenitor cells proliferate and differentiate to form mixed colonies. For many applications it is essential that such assays detect a high proportion of primitive progenitor cells. We describe an in vitro assay which detects a high incidence of human CD34+ multipotential progenitor cells. Bone marrow mononuclear cells (MNC) or selected CD34+ cells were plated at low cell concentrations in semisolid agar cultures with synergizing growth factor combinations. The optimum growth factor combination of conditioned medium from Mia PaCa-2 cells (Mia-CM), recombinant granulocyte-macrophage colony-stimulating factor and recombinant stem cell factor (SCF) supported the formation of macroscopic (> or = mm) colonies (97% of which were multilineage), at an average incidence of 250/10(5) MNC. The colony-forming cells (human colony-forming unit, type A) detected, showed a low cycling status (7.3%) and the macroscopic colonies had a high replating efficiency (46%), reflecting their probable primitive nature. This assay should prove invaluable, for studies on the regulation of proliferation of the multipotential compartment and in studies involving the assessment of these cells in transplantation and neoplastic disease.

Antigens, CD↗
PubMed1992

Circulating stem cells in mice treated with cyclophosphamide.

Chemotherapy has been used clinically to mobilize hematopoietic progenitor cells into the peripheral blood so that they can be harvested for autologous transplantation. In humans, this is demonstrated by the presence of circulating granulocyte-macrophage colony-forming cells (CFU-GM) and CD34-positive cells, but it has not been possible to confirm the presence of marrow-repopulating stem cells. In this study, we treated mice with 200 mg/kg cyclophosphamide (CY) and measured the numbers of white blood cells, day 12 CFU-S (CFU-S12), and CFU-GM in the peripheral blood. There was a peak in the numbers of CFU-S12 and CFU-GM 8 days after treatment with cyclophosphamide. Peripheral blood cells taken at this time rescued lethally irradiated mice and engraftment of donor cells was confirmed after 140 days in sex mismatched recipients using a Y chromosome-specific probe. In vitro culture of the blood cells harvested after cyclophosphamide showed that they proliferated in suspension cultures for at least a year in the presence of interleukin-3. The cultured cells rapidly lost their abilities to rescue irradiated mice and to form colonies in vitro, but they did not become leukemic. Also, CY-treated mice were irradiated with a leukemogenic dose of x-rays to coincide with peak circulating cell numbers but these animals did not develop an excess of leukemias over mice given irradiation alone.

Animals↗
PubMed1992

Demonstration of stem cell inhibition and myeloprotective effects of SCI/rhMIP1 alpha in vivo.

The proliferative status of the stem cell compartment is thought to be controlled by both positive and negative regulators of proliferation. These regulators have obvious clinical potential in manipulating the integrity and proliferative status of the stem cell in vivo during patient treatment for neoplastic disease. We have tested the ability of the human recombinant homologue of murine macrophage inflammatory protein-1 alpha (rhMIP1 alpha) to suppress the proliferation of primitive murine progenitors in vitro and in vivo. This recombinant protein (stem cell inhibitor, similar to the human homologue of MIP 1 alpha, LD78) is active in a dose-dependent manner in vitro on CFU-S measured at day 12 and to a slightly lesser extent on the more mature CFU-S that are measured at day 8. SCI/rhMIP1 alpha is also active in vivo in two separate models of bone marrow regeneration in which the high proliferative status of the CFU-S compartment is reduced to the quiescent state with a single inoculation of SCI/rhMIP1 alpha. The inhibitory activity of the recombinant protein was then tested in a relevant therapeutic model in which the observed protection of part of the stem cell compartment is reflected by a significant improvement in the kinetics of neutrophil recovery. These results establish the feasibility of testing SCI/rhMIP1 alpha in a range of chemotherapy regimes as a preliminary to clinical trials to attempt to protect the stem cell compartment during treatment for neoplastic disease.

Animals↗
PubMed1992

Transmission of chromosomal instability after plutonium alpha-particle irradiation.

When investigating the biological effects of ionizing radiation on the haemopoietic system, a confounding problem lies in possible differences between the biological effects of sparsely ionizing, low linear energy transfer radiation such as X-, beta- or gamma-rays, and densely ionizing, high linear energy transfer radiation such as alpha-particles. To address this problem we have developed novel techniques for studying haemopoietic cells irradiated with environmentally relevant doses of alpha-particles from a plutonium-238 source. Using a clonogenic culture system, cytogenetic aberrations in individual colonies of haemopoietic cells derived from irradiated stem cells have been studied. Exposure to alpha-particles (but not X-rays) produced a high frequency of non-clonal aberrations in the clonal descendants, compatible with alpha-emitters inducing lesions in stem cells that result in the transmission of chromosomal instability to their progeny. Such unexpected instability may have important implications for radiation leukaemogenesis.

Alpha Particles↗