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Biomedical subjects

B M Hannigan

Publications and source records attributed to B M Hannigan.

At least 19 recordsLinked to original sources
PubMed1996

Reactive oxygen species inducible by low-intensity laser irradiation alter DNA synthesis in the haemopoietic cell line U937.

BACKGROUND AND OBJECTIVE: The purpose of this study was to evaluate the possible role of reactive oxygen species (ROS) in mediating previously recorded alterations in DNA synthesis, inducible by low-intensity laser irradiation (LILI), in the haemopoietic cell line U937. STUDY DESIGN/MATERIALS AND METHODS: The ability of LILI (660 nm, 12 mW, 5 kHz) to induce ROS from U937 cells was assessed spectrophotometrically at energy densities (E.D.) from 1.0 to 11.5 J/cm2. In order to assess whether laser-induced ROS could alter cellular proliferation DNA synthesis was measured post-irradiation, by the incorporation of tritiated thymidine (3H-TdR) into the cells in both the presence and absence of the antioxidant catalase (CAT). RESULTS: Detectable ROS were produced post-irradiation only from the differentiated form of the cell line. Analysis by Student's t-test for unrelated groups showed a significant difference, at E.D.s 2.9 and 8.6 J/cm2, in the extent of DNA synthesis occurring in cells irradiated in the presence of CAT or in its absence. CONCLUSION: These findings demonstrate that laser-inducible ROS can mediate laser's effects on this cell line.

Catalase↗
PubMed1996

Macrophages and apoptotic cells in human colorectal tumours.

The numerical relationship between tumour associated macrophages (TAM) and apoptotic cells in 12 human colorectal tumours was evaluated. TAM were labelled immunohistochemically and apoptotic cells were visualized by counterstaining with haematoxylin and eosin (H&E). The stereological techniques, Cavalieri's estimator of volume and the Disector were used to estimate both tumour volume and numerical density of both cell types. The occurrence of TAM per unit volume of tissue increased with increasing tumour volume to a maximum in a tumour of 110.5 cm3, after which numbers declined. Levels of apoptosis also increased with tumour volume though more erratically than levels of TAM and declined for tumour volumes greater than 80 cm3. This is the first report of an attempt to assess the relationship between apoptotic cells and TAM in human tumours.

Apoptosis↗
PubMed1996

The effects of copper deficiency on human lymphoid and myeloid cells: an in vitro model.

Cu has long been known to influence immune responses. An in vitro model system was established in which human myeloid (HL-60), B-lymphoid (Raji) and T-lymphoid (Molt-3) cell lines could be grown in culture media of varying Cu levels. Initially Cu was removed from the medium by dialysis of fetal calf serum against a metal-ion chelator, minor depletion of other trace metals being obviated by repletion with appropriate metal salts. The growth rate of HL-60 was significantly (P < 0.05) inhibited by 72 h Cu depletion. Molt-3 cells required a longer period, up to 144 h, in Cu-depleted medium before growth was impaired. Raji-cell growth was not affected. These results confirmed clinical observations that T-cell functions were more sensitive to Cu deprivation than B cells. Analysis of intracellular metal levels in Molt-3 cells showed that Cu levels had been significantly lowered (P < 0.05) although Ca2+ levels were raised. Intracellular activity of the antioxidant enzyme superoxide dismutase (EC 1.15.1.1) was significantly impaired (P < 0.05) in Molt-3 cells grown in Cu-depleted medium. Activity of the mitochondrial enzyme cytochrome c oxidase (EC 1.9.3.1) was also significantly impaired (P < 0.05) by Cu depletion. Each of these findings indicates an increase in the potential for cellular damage by reduced antioxidant activity, impairment of normal mitochondrial activity and excessive Ca2+ influx. A major consequence of the type of damage occurring under these circumstances is membrane disruption. This was confirmed by scanning electron microscopy of Molt-3 cells grown under varying Cu levels.

B-Lymphocytes↗
PubMed1995

Oxidant-induced stress response in lymphoid cells.

The stress response to reactive oxygen species is an important defence system which can reduce their potential to induce biomolecule damage. In this investigation the effect of exposing Molt-3 lymphoblastoid cells or peripheral blood lymphocytes to a non-toxic dose of hydrogen peroxide (10 microM) was studied. Cellular response to a subsequent high dose of hydrogen peroxide (100-200 microM) was assessed by measurement of growth, viability, proliferation and DNA damage (lymphocytes only) and intracellular activities of the enzymes, superoxide dismutase, glutathione peroxidase and catalase (Molt-3 only). The results indicate that pretreatment of lymphocytes with 10 microM hydrogen peroxide can elicit a response which is protective against DNA damage normally inducible in these cells by subsequent exposure to toxic doses of hydrogen peroxide. It appears from the results with Molt-3 cells that altered activities of glutathione peroxidase may contribute to this enhanced resistance to hydrogen peroxide.

Cell Division↗
PubMed1994

Diet and immune function.

Adequate human nutrition is essential to maintain all normal physiological functions including defence of the self. Controversy exists about the precise constituents of diets optimal for all stages in the human life-span. Dietary composition may also need to be altered under such stressful conditions as infection or recovery from major surgery. Understanding how specific nutrients can alter immune responses may add to the quality of human lives by minimising the impact of disease morbidity and mortality. Dietary modification also offers hope of new therapeutic regimens for human diseases.

Aging↗
PubMed1993

DNA damage in human T-lymphoblastoid cell line Molt-3 induced by reactive oxygen species.

In the course of studying the effect of reactive oxygen species such as superoxide anion (O2-), hydrogen peroxide (H2O2) on oxidant-sensitive human T-lymphoblastoid cell line Molt-3, O2- has been generated by the interaction of xanthine with xanthine oxidase (XOD). To confirm that H2O2 is a key intermediate for inducing DNA single-strand breaks in Molt-3 cells, studies have been carried out with pure H2O2. In the presence of xanthine + XOD or H2O2 the amount of DNA single-strand breaks has been found to increase as a function of the O2- and H2O2 concentration. Data from studies with antioxidants such as superoxide dismutase and catalase supports a mechanism of DNA damage dependent on the presence of H2O2 in Molt-3 cells. Molt-3 cells are CD4+ and sensitive to reactive oxygen stress and therefore, could be an ideal cell line for determining the relationship between oxidative stress and various diseases such as acquired immunodeficiency syndrome (AIDS).

CD4-Positive T-Lymphocytes↗
PubMed1993

Thymidine kinases: the enzymes and their clinical usefulness.

Thymidine kinases (TK) convert thymidine, or deoxythymidine (dT) to the respective monophosphate. TK occurs in many different procaryotic and eucaryotic species and different TK isoenzymes are found within the same eucaryotic cell. One isoenzyme (foetal, cytoplasmic, TK1) is associated with cell division while the other (adult, mitochondrial, TK2) is cell cycle independent. The relative isoenzyme activities in a tissue thus reflect the fraction of proliferating cells. The gene encoding TK1 has been cloned for many species and regulation of its expression is known to be complex. Increases in TK activity appear to correlate with the presence of human neoplasia and disease progression and regression have been reported to correlate with TK levels in many cancer types. TK estimations in human lymphoproliferative diseases have implicated this enzyme as an early marker of maldifferentiation. TK levels may also be increased in non-dividing mammalian cells infected with RNA or DNA viruses. Some virus encoded TK has been shown to differ biochemically, immunologically and in substrate specificity from the corresponding TK isoenzymes in target host cells thus facilitating the development of specific antiviral therapeutics. Further, TK1 in leukemic cells may differ biochemically from normal cellular TK1 such that tumor-specific TK may provide a target for tumor detection and therapy. TK quantitation has conventionally been performed in assays of enzyme activity using radiolabeled (3H or 125I) nucleoside substrates. The development of TK1-specific, non-radioisotope based immunoassays and the measurement of TK mRNA in tumour tissue using TK (DNA or RNA) probes may prove sufficiently valuable to be incorporated into the routine clinical management of human cancer.

Antiviral Agents↗
PubMed1992

DNA damage in mammalian cell lines with different antioxidant levels and DNA repair capacities.

A wide range of DNA damage is known to be caused by reactive oxygen species (ROS). Defence against the effects of such damage include damage prevention (e.g. antioxidant activity) and the removal of damaged moieties from DNA (DNA repair). Radiation (X-ray) sensitive murine lymphoma (LY) cells were seen to be more susceptible to ROS-induced damage than were radiation resistant cells. This difference was unlikely to be due to the marginally decreased DNA excision repair capacity of the sensitive cells. Radiation sensitive cells did, however, have lower endogenous antioxidant enzyme levels. Thus, the importance of assessing all levels of a cell's response to ROS, in determining the major factors leading to increased mutagen sensitivity, is emphasised.

Animals↗
PubMed1992

Tumour cell inhibition of macrophage cytokine activity.

Macrophages elaborate both effector and regulatory immune functions. It was hypothesised that tumours can exert a local alteration of macrophage function. Murine peritoneal macrophage-derived cytokines were assayed in the presence and absence of cells, cytosol fractions or conditioned media (TCCM) from established murine tumour lines. Interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha activities were significantly inhibited by tumour cells or their products, as were the corresponding recombinant human cytokines. Intracellular protein kinase C activation was also measured and was significantly inhibited by murine TCCM, thus suggesting one possible site of inhibitor action. Data analyses indicate that the inhibitory factor(s) is probably not an already well-characterised macrophage inhibitor.

Animals↗
PubMed1991

Programmed cell death (apoptosis) in lymphoid and myeloid cell lines during zinc deficiency.

Three human cell lines of lymphoid (Molt-3 and Raji) or myeloid (HL-60) origin were maintained in vitro under zinc-sufficient or zinc-deficient conditions. Under these conditions, cell proliferation, viability and mode of death (apoptotic or necrotic) were assessed. All three cell types decreased their proliferative capacity and viability under conditions of zinc deficiency. Cell death in the HL-60 and Raji cultures occurred primarily via apoptosis, while most cells in zinc-deficient Molt-3 cultures died via necrosis. Apoptosis in zinc-deficient cultures of HL-60 and Raji cells was characterized by a slow decline in culture viability as cells with condensed and fragmented nuclear DNA appeared. These morphological changes were accompanied by an increase in cell buoyant density, which allowed separation of viable apoptotic cells from their non-apoptotic counterparts by means of percoll stepdensity gradients. Necrosis in zinc-deficient Molt-3 cultures was characterized by rapid loss of cell culture viability as these cells underwent direct lysis. Intact necrotic cells were easily identified by the flocculated state of their chromatin as well as the decreased basophilia of their cytoplasm. Analysis of DNA from apoptotic HL-60 and Raji cells revealed that internucleosomal DNA degradation, indicative of endogenous endonuclease activation, had occurred, whereas the nuclear DNA of necrotic Molt-3 cells remained relatively unfragmented. The different modes of cell death evoked may reflect the relative sensitivities of cells of these lineages to zinc levels in vivo.

Cell Division↗