PubMed Health⌕ Search

Biomedical subjects

R Tilley

Publications and source records attributed to R Tilley.

11 recordsLinked to original sources
PubMed1997

Plasma hypoxanthine levels in ARDS: implications for oxidative stress, morbidity, and mortality.

Acute respiratory distress syndrome in adults (ARDS) carries a high mortality. Patients with ARDS experience severe oxidative stress from neutrophil activation, and from treatment with high inspired oxygen concentrations (F(I)O2). Oxidative stress arises from an increased generation of reactive oxygen species (ROS) which overwhelm existing antioxidant defenses. Patients who do not survive ARDS sustain much greater levels of oxidative molecular damage, suggesting that they are less able to protect themselves against increased oxidative stress. We measured plasma levels of pro-oxidant substrates for xanthine oxidase, namely hypoxanthine and xanthine, and correlated them with the loss of plasma protein thiol groups. All patients with ARDS had higher levels of hypoxanthine (37.48 +/- 3.1 microM in nonsurvivors, 15.24 +/- 2.09 microM in survivors) compared with patients undergoing pulmonary resection (9.22 +/- 1.89 microM), patients in intensive care with sepsis but no lung injury (1.12 +/- 0.69 microM) and normal healthy control subjects (1.43 +/- 0.38 microM). The difference in plasma hypoxanthine levels between survivors and nonsurvivors of ARDS was highly significant (p < 0.001) and showed a negative correlation with loss of protein thiol groups. Xanthine levels were also higher in patients with ARDS but were not significantly different between ARDS survivors and nonsurvivors. Nonsurvivors of ARDS appear to experience higher levels of oxidative stress and damage than do survivors.

APACHE↗
PubMed1993

An in vitro model of ovarian epithelial carcinogenesis: changes in cell-cell communication and adhesion occurring during neoplastic progression.

To investigate the cellular mechanisms of ovarian epithelial carcinogenesis, a series of progressively transformed rat ovarian surface epithelial (ROSE) cell lines were developed and studied. Transfection of primary ROSE cells and an immortalized ROSE line (ROSE 199) with the pSV3neo plasmid (SV40 T-antigen) yielded transformed lines which retained epithelial morphology. In vivo selection of these pSV3neo cell populations resulted in further phenotypic transformation. Transfection of ROSE 199 with pSV2neo/c-H-rasEJ (rasEJp21) resulted in a malignant line which appeared fibroblast-like and formed invasive sarcomas both in athymic mice and in immunocompetent rats. Gap junctional intercellular communication (GJIC) and cell-cell adhesion were studied in this series of ROSE lines. Both c-H-rasEJ-transformation and in vivo selection resulted in a significant reduction of GJIC between adjoining cells and a transition of in vitro migration as continuous epithelial sheets to the dissociation of individual cells. This apparent shift in cell adhesiveness was associated with reduced expression of the E-cadherin adhesion molecule. Our data suggest that neoplastic progression of the ovarian surface epithelium may be associated with concomitant reductions in GJIC, E-cadherin expression and functional adhesiveness.

Animals↗
PubMed1992

Enhanced unscheduled DNA synthesis by secondary cultures of lung cells established from calorically restricted aged rats.

Unscheduled DNA synthesis (UDS) induced by two exposure levels of ultraviolet light (UV) or two concentrations of methyl methane sulfonate (MMS) was evaluated in secondary cultures of lung fibroblasts established from weanling, 11-month-old and 31-month-old female Fischer 344 rats fed ad libitum (AL) or calorically restricted (CR) diets. [3H]Thymidine incorporation as a function of UDS was highest for weanling-derived cells treated with either UV or MMS, declining consistently with increased age between cells from weanling, 11-month-old and 31-month-old animals. [3H]Thymidine incorporation as a function of UDS in cells from 11-month-old AL vs. CR rats differed only at the highest UV exposure level. In contrast, cells derived from 31-month-old CR rats exhibited UDS levels which were at least twice as high at each UV treatment level as UDS levels of cells derived from the same age AL rats. Cells from both old AL and old CR rats were shown to initiate DNA excision repair at about the same rate. Cells from CR rats, however, repaired DNA damage at an accelerated rate and completed excision repair while repair in cells from AL animals was slower and apparently did not proceed to completion. Data from this study indicate that cells from young and old AL and CR animals initiate excision repair, but demonstrate an age-related loss of UV- or MMS-stimulated [3H]thymidine incorporation in cells derived from AL animals. Cells derived from CR animals did not exhibit that age-related loss of UDS activity; rather, they showed an enhanced UDS response to DNA damage and appeared to complete ligation as the final step in excision repair. The data suggest that caloric restriction of a cell donor animal not only delays the age-associated decrease in in vitro DNA excision repair capacity in cells from that animal, but may actually enhance repair capacity.

Aging↗
PubMed1991

Rat ovarian granulosa cell culture: a model system for the study of cell-cell communication during multistep transformation.

A spontaneously immortalized clonal granulosa cell line (SIGC) derived from primary rat ovarian granulosa cell cultures was developed as a model system to explore the process of transformation using an epithelial cell type. SIGC has an epithelial morphology and grows in culture without undergoing luteinization. The cell line is thought to represent an intermediate step in carcinogenesis because it seems to grow indefinitely in culture but does not form clones in soft agar or tumors in nude mice. Indirect immunofluorescence and Western blot analysis verified the constitutive expression of the recessive oncogene product p53 in the cell line, thereby suggesting a possible mechanism of immortalization. Ultrastructural studies indicated that SIGC cells are characterized by an undifferentiated phenotype with prominent intermediate filaments, desmosomes, and gap junctions. The identification of cytokeratin by indirect immunofluorescence and Western blot analysis suggests that SIGC functions as an epithelial cell type. Functional studies of cell-cell communication by a dye transfer technique (fluorescence recovery after photobleaching) showed reduced communication compared to normal primary granulosa cells in culture. SIGC cells were transfected with early region genes of SV40 virus in an attempt to generate fully transformed cell lines. The resulting cell line SV-SIGC expressed T-antigen, was anchorage independent, formed tumors in nude mice, and had reduced intercellular communication as compared to SIGC cells. Explants from the tumors in nude mice were used to generate another cell line (T-SV-SIGC), which exhibited further reduction in both the incidence and the rate of communication. These results clearly demonstrated a progressive loss of functional communication during multistep transformation of an ovarian cell type. These data demonstrate that this assay system based on an epithelioid cell type can be used to study the relationship between intercellular communication and the multistep process of carcinogenesis.

Animals↗
PubMed1990

Mitogen-activation of spleen cells in aged animals is potentiated by dietary restriction: a preliminary report.

Dietary restriction has been reported to be associated with increased life span and increased DNA repair capacity in both male and female rats and mice. We examined dietary restriction effects on immune system function and prolongation of life span in specific pathogen free rats and mice. In this preliminary report the authors show that dietary restriction is correlated with a dramatic increase in the lifespan of both male and female rats and mice in a pathogen free environment, and in the capacity of cultured splenocytes from those animals to initiate blastogenesis in response to antigenic stimulation.

Aging↗
PubMed1989

Age-related changes in DNA polymerase alpha expression.

DNA polymerase alpha isozymes differing in specific activity and affinity of binding to DNA were purified from human fibroblasts derived from donors of different ages. Fetal-derived fibroblasts expressed a single, high-activity enzyme (A2), with high affinity of binding to DNA. Adult-derived fibroblasts exhibited two forms of DNA polymerase alpha, one identical to the fetal enzyme, and a second with about tenfold less activity showing low affinity of binding to DNA (A1). The ratio of DNA polymerase A2/A1 decreased dramatically with age, from 100% A2 in fetal-derived fibroblasts to about 94% A1 in fibroblasts derived from a 66-year-old donor. The DNA binding affinity of polymerase alpha A1 from adult-derived fibroblasts increased concomitant with a significant increase in activity when the enzyme was treated with phosphatidylinositol-4-monophosphate (PIP), or with inositol-1, 4-bisphosphate (I(1,4)P2). The enzyme reverted back to a less active form, with loss of the noncovalently bound I(1,4)P2, as a function of time. When permeabilized human fibroblasts with low DNA excision repair capacity were treated with 7,8-dihydrodiol-9,10-epoxybenzo(a)-pyrene (BPDE) in the presence of 32P-ATP, phosphatidylinositol, and cycloheximide, excision repair was initiated and 32P-labeled DNA polymerase alpha was recovered in the absence of de novo protein synthesis. DNA synthesis associated with either scheduled DNA synthesis or BPDE-initiated excision repair declined as a function of increased age in human cells. The data suggest that the decline in both DNA excision repair-associated and mitogen-activated DNA synthesis may be correlated with decreased total intracellular levels of DNA polymerase and with the decline in polymerase alpha activity as a function of age, that DNA repair-associated initiation of DNA synthesis in adult-derived cells may increase with activation of a pool of low activity DNA polymerase alpha, and that DNA polymerase alpha activity increases as a function of enzyme interaction with a component of the PI phosphorylation cascade.

Cell Survival↗
PubMed1984

Human T-cell leukemia virus (HTLV) in the United Kingdom.

Ten out of 26 leukaemic patients who had emigrated from the Caribbean region to the United Kingdom had adult T-cell leukaemia with associated serum antibodies to HTLV I. Antibodies to HTLV were also detected in sera from a small proportion of non-leukaemic Caribbean immigrants but not in any sera from other (non-ATL) T-cell leukaemias or a variety of control groups. The long period between immigration to the UK and diagnosis of leukaemia (up to 30 years) suggests that an extensive latent period in disease development may exist. Cell lines were isolated from two patients with HTLV antibody-positive ATL and were shown to be virus-positive by electron microscopy and immunofluorescence using antibodies to the p19 and p24 viral proteins. HTLV1 provirus integration and active transcription were demonstrated by Southern blotting of DNA and in situ hybridization respectively using molecularly cloned HTLV1 probes. Virus from one of these cell lines could be transmitted to normal T cells by co-cultivation.

Adolescent↗
PubMed1975

Decreased 3H-uridine incorporation and increased 3H-adenosine incorporation by HeLa cells exposed to autologous culture fluid.

Actively growing HeLa monolayer cultures briefly exposed to the culture fluids (CF) from confluent HeLa cultures and labeled simultaneously or subsequently, incorporated less 3H-uridine (3H-UR) but more 3H-adenosine (3H-AR) than control cultures similarly exposed to fresh medium and labeled. Exposure to CF inhibited the uptake as well as the incorporation of 3H-UR by cultures. The inhibition of 3H-UR incorporation by CF-exposed cultures could be reduced by increasing the concentration of 3H-UR in the labeling medium. Both the inhibition of 3H-UR incorporation and the stimulation of 3H-AR incorporation were prevented by washing the CF-treated cultures with phosphate buffered saline before labeling. Similarly, both effects could be producted in HeLa cultures exposed to fresh medium containing 1 X 10(-5) M uridine instead of to CF. Therefore, the observed effects of CF on label incorporation were probably due to the presence of uridine or a related compound, and the inhibition of 3H-UR incorporation resulted from reduced uptake of 3H-UR rather than from reduced RNA synthesis by exposed cells. The active agent in the CF, formed only when cultures were incubated at physiological temperatures, was not a product of medium decay. It was a cellular product formed equally well by cultures incubated in medium containing dialysed or whole serum.

Adenosine↗
PubMedDate not supplied

Effects of aging and dietary restriction on DNA polymerases: gene expression, enzyme fidelity, and DNA excision repair.

Hepatic DNA polymerases isolated from young and old C57BL/6N mice fed ad libitum or calorically restricted differed in chromatographic characteristics, binding affinity for DNA template-primer, specific activity, and fidelity of synthesis. DNA polymerase alpha total and specific activity declined slightly, while the nucleotide misincorporation frequency increased dramatically, with increased age of the donor animals. A positive correlation was observed between polymerase alpha specific activity and the affinity of enzyme binding to activated DNA template-primer. Both the age-associated decline in enzyme activity and the decrease in fidelity of synthesis were modified by dietary restriction, with higher specific activity levels and lower misincorporation frequencies for DNA polymerases from dietarily restricted animals compared with ad libitum animals of all ages. Fidelity of both DNA polymerase alpha and beta increased following treatment with the phosphoinositide hydrolysis product inositol-1,4-bisphosphate. The data suggest that dietary restriction could play an important role in decreasing the age-associated decline in function of physiological systems sensitive to decreased or defective DNA synthesis.

Aging↗