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Biomedical subjects

R O'Neill

Publications and source records attributed to R O'Neill.

At least 37 records · Page 2Linked to original sources
PubMed1994

Differential production of TNF by Kupffer cells after phagocytosis of E. coli and C. albicans.

Tumor necrosis factor (TNF) of hepatic origin is thought to play a pivotal role early in the genesis of the septic shock syndrome, regardless of microbial etiology. To determine if production of TNF by Kupffer cells varies with microbial taxonomic class, we measured TNF secretory responses in primary cultures of rat Kupffer cells to numerically equivalent gram-negative bacterial or fungal phagocytic challenges. After a 30-min exposure to media, latex beads, soluble Escherichia coli lipopolysaccharide (LPS; serotype 055:B5), live or Formalin-fixed E. coli (serotype 055:B5), live or Formalin-fixed yeast-phase Candida albicans, or live hyphal-phase Candida, samples of culture supernatant were assessed at 30, 60, 120, and 240 min and at 24 h for TNF bioactivity by L929 cell cytotoxicity. Compared with media and latex bead controls, TNF levels progressively increased for up to 240 min after either LPS and equivalently in live E. coli or Formalin-fixed E. coli groups (P < 0.05). Formalin-fixed yeast-phase and live extracellular hyphal-phase C. albicans failed to stimulate production of TNF at any time point (6.9 +/- 0.7 and 8.7 +/- 0.4 U/ml, respectively, at t = 240 min; P < 0.05 vs. E. coli). In contrast, internalization of live yeast-phase C. albicans with subsequent hyphal formation and growth within Kupffer cells was accompanied by a rise in supernatant TNF levels (14.5 +/- 1.8 U/ml at t = 240 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Identification and characterization of a receptor for tissue ferritin on activated rat lipocytes.

Hepatic iron overload causes lipocyte activation with resultant fibrogenesis. This study examines whether rat lipocytes express ferritin receptors, which could be involved in paracellular iron movement and in cellular regulation. Lipocytes from normal rat liver were cultured on plastic and incubated with 125I-labeled rat liver ferritin (RLF) +/- a 100-fold excess of either unlabeled RLF or human heart ferritin, human liver ferritin, human recombinant H-ferritin, a mutant human recombinant L-ferritin, or a variety of nonspecific proteins. Specific binding sites for ferritin were demonstrated by displacement of 125I-RLF by RLF (64.5 +/- 4.3%) and by other ferritins (55-60%), but not by recombinant L-ferritin. Scatchard analysis demonstrated a single class of binding sites with a Kd of 5.1 +/- 2.9 x 10(-10) M, maximum binding capacity of 4.7 +/- 1.3 x 10(-12) M, and 5,000-10,000 receptor sites/cell. Ferritin receptor expression was observed only in activated lipocytes. Internalization of RLF was observed within 15 min using FITC-RLF and confocal microscopy. This study demonstrates that (a) activated lipocytes express a specific high affinity ferritin receptor; (b) the binding appears to be dependent on the H-ferritin subunit; and (c) lipocytes internalize ferritin. Expression of ferritin receptors in activated lipocytes suggests that the receptor may either be involved in the activation cascade or may be a marker of activation.

Actins↗
PubMed1993

Efficient enzymatic synthesis of the sialyl-Lewisx tetrasaccharide. A ligand for selectin-type adhesion molecules.

Sialyl-Lewisx (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc] has been identified as a ligand for E-selectin, P-selectin and recently also for L-selectin. We have synthesized the sialyl-Lewisx tetrasaccharide by total enzymatic synthesis from N-acetyllactosamine using a placental alpha 2-->3-sialyltransferase specific for type-2 chain acceptors, followed by a cloned human alpha 1-->3-fucosyltransferase (FucTV, the 'plasma-type' enzyme). This procedure resulted in the tetrasaccharide in a 61% overall yield.

Amino Sugars↗
PubMed1993

Hepatic mitochondrial energy production in rats with chronic iron overload.

BACKGROUND: Iron overload results in impaired hepatic mitochondrial oxidative metabolism. The current experiments evaluated the effects of iron overload on enzyme activities in the mitochondrial electron transport chain, on hepatic adenine nucleotide levels, and on hepatocellular oxygen consumption. METHODS: Hepatic iron overload was produced in rats using dietary carbonyl iron. Hepatic adenine nucleotides were assessed after freeze-clamping, mitochondrial enzyme activities and oxygen consumption were measured in isolated mitochondria, and oxygen consumption in isolated hepatocytes was determined. RESULTS: At a mean hepatic iron concentration of 4630 micrograms/g, there were no changes in reduced nicotinamide adenine dinucleotide (NADH)-cytochrome c reductase activity (complex I-III), but there was a 35% reduction in succinate-cytochrome c reductase activity (complex II-III), and a 70% decrease in cytochrome c oxidase activity (complex IV). With mild iron loading (2060 micrograms/g), there was a 28% decrease in hepatic adenosine 5'-triphosphate (ATP) levels with no change in adenosine 5'-diphosphate (ADP) or adenosine 5'-monophosphate (AMP) levels, whereas, at a higher hepatic iron concentration (3170 micrograms/g), there was a 40% reduction in ATP levels, a 22% decrease in ADP levels, with no change in AMP levels. There was a 48% reduction in oxygen consumption in isolated iron-loaded hepatocytes. CONCLUSIONS: Chronic iron overload decreases hepatic mitochondrial cytochrome c oxidase activity, hepatocellular oxygen consumption, and hepatic ATP levels.

Adenosine Diphosphate↗
PubMed1991

Chronic dietary iron overload in rats results in impaired calcium sequestration by hepatic mitochondria and microsomes [corrected].

The purpose of these experiments was to determine whether chronic dietary iron overload causes impairment of hepatic mitochondrial and/or microsomal calcium sequestration. Experimental iron overload was produced by feeding three groups of rats a chow diet supplemented with 3.0% (wt/wt) carbonyl iron for up to 8 weeks achieving graded increases in hepatic iron concentrations ranging from 1360 to 3170 micrograms/g. At low levels of iron overload, there were no changes in mitochondrial oxidative metabolism or calcium sequestration, whereas at moderate and high degrees of iron loading, both of these parameters were significantly reduced. In contrast, there were significant decreases in microsomal cytochrome P450 levels and microsomal calcium sequestration at all three levels of iron loading. These abnormalities occurred at hepatic iron concentrations at which the authors have previously found evidence of hepatic organelle lipid peroxidation. These alterations in organelle calcium sequestration may impair intracellular calcium homeostasis in the liver and contribute to subsequent cellular injury.

Animals↗
PubMed1990

Hepatic mitochondrial malondialdehyde metabolism in rats with chronic iron overload.

Peroxidative decomposition of mitochondrial membrane phospholipids with subsequent mitochondrial dysfunction is a postulated mechanism of liver cell injury in parenchymal iron overload. Malondialdehyde is formed when polyunsaturated fatty acids of membrane phospholipids undergo peroxidative decomposition, and it is metabolized by aldehyde dehydrogenase. We studied mitochondrial metabolism of malondialdehyde in rats with chronic dietary iron overload. Hepatic malondialdehyde concentrations were significantly increased in iron-loaded livers, and mitochondrial respiratory control ratios using glutamate as a substrate were decreased by 47% largely owing to reductions in state 3 respiration. When exogenous malondialdehyde was added to mitochondrial fractions, there was significantly less metabolism of malondialdehyde in mitochondria of iron-loaded livers as compared with controls. In addition, there was a 28% decrease in mitochondrial aldehyde dehydrogenase in iron-loaded livers but no change in cytosolic aldehyde dehydrogenase. Increased hepatic malondialdehyde in chronic iron overload may result from a combination of increased production and decreased metabolism of malondialdehyde, both of which may be due to iron-induced mitochondrial lipid peroxidation.

Aldehyde Dehydrogenase↗
PubMed1990

Prevention of hepatocyte injury and lipid peroxidation by iron chelators and alpha-tocopherol in isolated iron-loaded rat hepatocytes.

These experiments were performed to characterize the relationship between lipid peroxidation and hepatocyte viability in iron overload. Hepatocytes were isolated from rats with chronic dietary iron overload and the effects of in vitro iron chelation on lipid peroxidation, cell viability and ultrastructure were studied over a 4-hr incubation period. Cell viability was significantly reduced at 3 and 4 hr in iron-loaded hepatocytes compared with controls and was preceded by an increase in iron-dependent lipid peroxidation. Similarly, extensive degenerative ultrastructural changes were observed in iron-loaded hepatocytes compared with controls after 4 hr of incubation. In vitro iron chelation with either deferoxamine or apotransferrin protected against lipid peroxidation, loss of viability and ultrastructural damage in iron-loaded hepatocytes. The addition of an antioxidant, alpha-tocopherol, also protected against lipid peroxidation and preserved cell viability over a 4-hr incubation. The protective effects of iron chelators and alpha-tocopherol support a strong association between iron-dependent lipid peroxidation and hepatocellular injury in iron overload.

Animals↗
PubMed1989

Effects of vitamin E deficiency on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload.

Peroxidative decomposition of organelle membrane phospholipids with subsequent organelle dysfunction is a postulated mechanism of liver cell injury in parenchymal iron overload. We studied the effects of different alpha-tocopherol concentrations on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload. There was no evidence of mitochondrial lipid peroxidation (conjugated dienes) or alteration in mitochondrial oxidative metabolism in alpha-tocopherol-deficient rats with normal hepatic iron levels. Significant reductions in mitochondrial respiratory control ratios and oxidative phosphorylation ratios were seen in association with increased conjugated dienes in all three groups of iron-loaded rats regardless of the alpha-tocopherol status (deficient, normal or excess); thus, the alpha-tocopherol deficiency associated with dietary iron overload in this experimental model is not responsible for the mitochondrial abnormalities observed. In addition, chronic parenteral administration of alpha-tocopherol to iron-loaded animals, which increased hepatic levels of this substance 3-fold, did not ameliorate the hepatic mitochondrial lipid peroxidation or the defects in mitochondrial oxidative metabolism resulting from iron overload.

Animals↗
PubMed1989

Analysis of Aprt deficient mutants of Friend erythroleukaemia cells.

Cytogenetic analysis of mutants of the Friend Erythroleukaemia cell line deficient in adenine phosphoribosyl transferase (Aprt) was undertaken to ascertain whether non-disjunctional events were involved in the production of this mutation. All mutant clones examined were found to carry two copies of chromosome 8, the chromosome to which Aprt maps. Since the two homologues are distinguishable by silver staining, it was also clear that no mutants contained two copies of one homologue having lost the other. Treatment of mutants with 5-azacytidine failed to reactivate the Aprt locus.

Adenine Phosphoribosyltransferase↗
PubMed1989

Sounds of silence--coping with hearing loss and loneliness.

The vast majority of people will suffer presbycusis during the aging process. This hearing loss has potential social consequences, which place these individuals at risk for loneliness. Nurses need to encourage thorough audiological examination and follow through on recommendations to improve hearing. The use of hearing aids needs to be encouraged. A suggested model of interaction among variables influencing loneliness identifies areas amenable to nursing intervention. Frequency of significant interaction and motivation to engage in interactions represent two important variables that influence loneliness.

Adaptation, Psychological↗
PubMed1986

Iron-induced peroxidative injury to isolated rat hepatic mitochondria.

Peroxidative injury to the mitochondrial inner membrane with resultant defects in oxidative metabolism may be partially responsible for hepatocellular injury in iron overload. We examined the effects of iron-induced lipid peroxidation in vitro on hepatic mitochondrial morphology and function and determined if various inhibitors of free-radical-mediated injury could be protective. Normal rat liver mitochondria were prepared by differential centrifugation and were incubated with 1, 2, and 3 microM Fe2+, NADPH, and with and without oxygen radical scavengers, iron chelators, and antioxidants. There was a direct linear relationship between the concentration of added iron and the degree of lipid peroxidation as measured by malondialdehyde (MDA) production (r = .85). With 3 microM Fe2+ there was a decrease in the respiratory control ratio (RCR) for all four substrates tested; this decrease in RCR was due to a decrease in the state 3 respiratory rate for all substrates, with no changes in the state 4 respiratory rate for glutamate, beta-hydroxybutyrate, or succinate. Oxygen radical scavengers failed to prevent iron-induced lipid peroxidation or to protect against associated mitochondrial dysfunction. Iron chelators and antioxidants prevented MDA formation and mitochondrial function was maintained. Iron-induced lipid peroxidation in vitro produces an irreversible inhibitory defect in mitochondrial electron transport that may be specific at complex IV (cytochrome oxidase).

Animals↗
PubMed1985

Determination of alpha-tocopherol in rat liver by high-performance liquid chromatography utilizing ultraviolet detection.

A rapid, sensitive analytical procedure was developed to quantitate alpha-tocopherol in rat liver. Liver is homogenized in acetone, fractionated by reversed-phase high-performance liquid chromatography and alpha-tocopherol quantitated by monitoring the column effluent at 280 nm. A single analysis requires 18 min. The method is linear from 1.0 to greater than 30.0 micrograms alpha-tocopherol per g of liver (wet weight). The average relative standard deviation of the slope of the standard curve is 2.3% and the single-day coefficient of variation is 6.3%. The use of an acetone extraction, reversed-phase column chromatography and quantitation of alpha-tocopherol at 280 nm results in a sensitive and reproducible system for the determination of alpha-tocopherol concentrations in rat liver. Preliminary studies have shown the assay to be useful for investigation of the effects of age and diet on hepatic alpha-tocopherol concentration.

Aging↗
PubMed1983

Initiation of carcinogenesis dependence upon MNNG-induced release of the G1 block of density-inhibited Syrian hamster cells.

After N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment of density-inhibited postconfluent (DDIR) Syrian hamster embryo cell cultures, only a small population of the cells incorporate [3H]-thymidine within the next 10-20 h. The transformed colonies, observed subsequent to reseeding, are derived from the population incorporating [3H]-thymidine. This study demonstrates that MNNG-induced thymidine incorporation resulted from semiconservative DNA synthesis as analyzed by DNA density gradients. Furthermore, cell cycle distributions at selected times after treatment indicate that the MNNG-responsive population was released from the density-dependent G1 block, proceeded through S, and became blocked again at G2 or M. These results indicate that DNA synthesis is temporally related to an early step in carcinogenesis.

Animals↗
PubMed1982

Autonomic arousal, interpersonal climate, and orality.

Electrodermal responses in male subjects who gave at least four oral-dependent Rorschach responses (n = 15) or no more than two such responses (n = 19) were assessed both before and after the subjects had either a warm, friendly interaction or a cold, unfriendly interaction with a confederate. There were no group differences on initial baseline measurements. Following a 10-minute warm or cold interaction, there was significant three-way interaction (Period X Condition X Orality) in tonic conductance, p less than .003. Analysis of the three-way interaction produced one simple effect: Highly oral subjects responded differentially to warm or cold treatment by the confederate, p less than .018. Three groups--nonorals in either condition and orals in the condition--increased in physiological arousal over time. Only the highly oral subjects interacting with the warm confederate showed no such increase in arousal, presumably because the presence of a warm, interested other inhibits physiological activation.

Adult↗
PubMed1982

Neoplastic transformation of Syrian hamster embryo cells by bisulfite is accompanied with a decrease in the number of functioning replicons.

Bisulfite, a chemical that at neutral pH does no induce mutations at two loci in Chinese hamster V-79 cells, induces transformation of Syrian hamster embryo cells. Although bisulfite affects DNA metabolism, there was no evidence of bisulfite-induced DNA damage. Bisulfite induced no excision repair replication, caused no DNA strand breaks detectable in alkaline sucrose gradients, had no effect on the size distribution of DNA nascent daughter strands, and did not affect excision on post-replication repair of u.v.-induced damage. However, bisulfite did induce a dose-dependent decrease in the rate of DNA replication per cell, apparently due to a reduction in the number of functioning replicons. Since the data indicate that bisulfite causes no detectable DNA damage, it appears that bisulfite induces transformation by a non-mutagenic event that could involve the inhibition of semi-conservative DNA synthesis.

Animals↗