Search PubMed⌕ Search

Biomedical subjects

Simon Eaton

Publications and source records attributed to Simon Eaton.

At least 19 recordsLinked to original sources
PubMed2006

Free radical scavenging inhibits STAT phosphorylation following in vivo ischemia/reperfusion injury.

The signal transducer and activator of transcription (STAT) family are latent transcription factors involved in a variety of signal transduction pathways, including cell death cascades. STAT1 has been shown to have a crucial role in regulating cardiac cell apoptosis in the myocardium exposed to ischemia/reperfusion (I/R) injury. The free radical scavenger, tempol, is known to have cardioprotective properties, although little is known about the molecular mechanism(s) by which it acts. In the present study, we assessed the levels of phosphorylated STAT1 and STAT3 and examined whether tempol was able to affect STAT activation after in vivo cardiac I/R injury. We observed a reperfusion time-dependent increase in the tyrosine phosphorylation of STAT1 and STAT3 at residues 701 and 705, respectively. Here we show for the first time that tempol dramatically reduced STAT1 and 3 phosphorylation. The reduction in STAT1 and 3 phosphorylation was accompanied by a concomitant decrease in cellular malondialdehyde (MDA) levels. To verify the role of STAT1 in modulating the cardioprotective effect of tempol, rats were injected with the STAT1 activator, IFN-gamma, and tempol during I/R injury. We found that the presence of IFN-gamma abrogated the protective effects of tempol, suggesting that the protective effects of tempol may partly operate by decreasing the phosphorylation of STAT1. This study demonstrates that careful dissection of the molecular mechanisms that underpin I/R injury may reveal cardioprotective targets for future therapy.

Animals↗
PubMed2006

An investigation of minimisation criteria.

BACKGROUND: Minimisation can be used within treatment trials to ensure that prognostic factors are evenly distributed between treatment groups. The technique is relatively straightforward to apply but does require running tallies of patient recruitments to be made and some simple calculations to be performed prior to each allocation. As computing facilities have become more widely available, minimisation has become a more feasible option for many. Although the technique has increased in popularity, the mode of application is often poorly reported and the choice of input parameters not justified in any logical way. METHODS: We developed an automated package for patient allocation which incorporated a simulation arm. We here demonstrate how simulation of data can help to determine the input parameters to be used in a subsequent application of minimisation. RESULTS: Several scenarios were simulated. Within the selected scenarios, increasing the number of factors did not substantially adversely affect the extent to which the treatment groups were balanced with respect to the prognostic factors. Weighting of the factors tended to improve the balance when factors had many categories with only a slight negative effect on the factors with fewer categories. When interactions between factors were included as minimisation factors, there was no major reduction in the balance overall. CONCLUSION: With the advent of widely available computing facilities, researchers can be better equipped to implement minimisation as a means of patient allocation. Simulations prior to study commencement can assist in the choice of minimisation parameters and can be used to justify those selections.

Age Distribution↗
PubMed2006

The biochemical basis of antioxidant therapy in critical illness.

During critical illness free radical production may increase as a result of, for example, sepsis or tissue trauma. In addition, because of a potential for increased losses, and the possibility of inadequate nutrition, the antioxidant defences of the body may become compromised. Thus, the delicate balance between free radicals and antioxidants may be disturbed. Various nutritional and pharmacological strategies to enhance antioxidant defences have been proposed, which aim either to maintain or enhance endogenous antioxidant stores or to provide alternative antioxidant agents. Trace elements and amino acids are particularly important, and their synergistic role in the maintenance of the body's antioxidant defence network will be discussed.

Antioxidants↗
PubMed2006

Selenium in critical illness.

PURPOSE OF REVIEW: Selenium is a trace element essential to human health. Critical illness is associated with the generation of oxygen free radicals resulting in a condition of oxidative stress. Supplementing critically ill patients with antioxidant nutrients may improve survival. Selenium levels can be low due to redistribution to high-priority organs and dilution associated with aggressive resuscitation of the patient. The purpose of this review is to investigate the benefit of selenium supplementation in critically ill patients. RECENT FINDINGS: Most of the selenium-supplementation trials were performed in relatively small patient populations presenting with trauma, sepsis, burns and adult respiratory distress syndrome. Widely varying doses of selenium of between 200 and 1000 microg were used, either alone or in combination with other antioxidants. Significant improvements have been demonstrated in length of hospital stay, rate of infection and need for haemodialysis in these patients. However, no trial has demonstrated a statistically significant improvement in mortality. Two recent meta-analyses suggest a trend towards reduced mortality with selenium supplementation. SUMMARY: Selenium, by supporting antioxidant function, may be associated with a reduction in mortality. To demonstrate this large, well-designed randomized trials are required.

Antioxidants↗
PubMed2006

Altered cleavage and localization of PINK1 to aggresomes in the presence of proteasomal stress.

Following our identification of PTEN-induced putative kinase 1 (PINK1) gene mutations in PARK6-linked Parkinson's disease (PD), we have recently reported that PINK1 protein localizes to Lewy bodies (LBs) in PD brains. We have used a cellular model system of LBs, namely induction of aggresomes, to determine how a mitochondrial protein, such as PINK1, can localize to aggregates. Using specific polyclonal antibodies, we firstly demonstrated that human PINK1 was cleaved and localized to mitochondria. We demonstrated that, on proteasome inhibition with MG-132, PINK1 and other mitochondrial proteins localized to aggresomes. Ultrastructural studies revealed that the mechanism was linked to the recruitment of intact mitochondria to the aggresome. Fractionation studies of lysates showed that PINK1 cleavage was enhanced by proteasomal stress in vitro and correlated with increased expression of the processed PINK1 protein in PD brain. These observations provide valuable insights into the mechanisms of LB formation in PD that should lead to a better understanding of PD pathogenesis.

Animals↗
PubMed2005

Prevalence of diabetes in rural Victoria.

AIMS: To compare the prevalence of diabetes in adults in small and medium sized towns in a part of rural Victoria MATERIALS AND METHODS: Participants were usual residents, aged >or=25 years, from randomly selected households in the crossroads undiagnosed disease study (CUDS: six small rural towns and their regional center in rural Victoria). Response rates to an initial census at the household and attendance at a subsequent biomedical examination involved were 70% and 61% (1454), respectively. All non-diabetic participants had an oral glucose tolerance test. RESULTS: Prevalence of diabetes, IGT, IFG were 7.3 (5.5-9.5)%, 6.9 (5.1-9.9)% and 3.2 (2.0-4.7)% respectively in the regional center and 8.9 (6.9-11.1)%, 4.9 (3.5-6.7)%, 3.0 (1.9-4.5)% in the Shire Capitals. Overall, 31/118 (26.3%) of those with diabetes were previously undiagnosed. Most (83.9%) of those with undiagnosed diabetes remembered having been screened for diabetes in the previous 2 years. Overall screening rates for diabetes were higher than across Victoria as a whole. CONCLUSIONS: The prevalence of diabetes has probably doubled over the last 15 years in this area. Undiagnosed diabetes is less common than expected, possibly as a result of a more vigorous approach to screening in general practice and in spite of the lower numbers of GPs in the area.

Adult↗
PubMed2005

The synthesis of internal standards for the quantitative determination of sphingolipids by tandem mass spectrometry.

Novel internal standards have been synthesised for the quantitative determination by tandem mass spectrometry (MS/MS) of the sphingolipids that accumulate in lysosomal storage diseases. The [d4]C16- and [d47]C24-isoforms of galactosylceramide (CMH), lactosylceramide (CDH), globotriaosylceramide (CTH), cerebroside sulphate, sphingomyelin and G(M1)-, G(M2)- and G(M3)-gangliosides were synthesised by the reaction of their lyso-forms with the acid chlorides of hexadecanoic 5,5,6,6-d4 acid ([d4]-palmitic acid) and tetracosanoic-d47 acid ([d47]-lignoceric acid), respectively. The acid chlorides were formed using oxalyl chloride. The structures of the internal standards were confirmed by MS/MS. The fragmentation pattern of each novel compound was similar to that of the corresponding natural form of the sphingolipid, making it a good internal standard for the quantitative determination of the natural sphingolipid by ESI-MS/MS. Characteristic product ions were identified for each compound.

Lysosomal Storage Diseases↗
PubMed2005

Hyperinsulinism of infancy associated with a novel splice site mutation in the SCHAD gene.

Fatty acids play an important role in regulating insulin secretion, but the mechanisms are unclear. We report a case of a novel splice site mutation in the short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD) gene associated with hyperinsulinism. This mutation resulted in a nearly complete absence of immunoreactive protein and a decrease in fibroblast SCHAD activity.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2005

Total glutathione is not decreased in infants with necrotizing enterocolitis.

BACKGROUND: Glutathione (GSH) is the major intracellular antioxidant protecting against free radical-mediated damage. Oxidative stress is implicated in the pathogenesis of necrotizing enterocolitis (NEC), and damage could be enhanced by a relative deficiency of GSH. We hypothesized that infants with NEC would have lower levels of erythrocyte GSH when compared with controls. METHODS: Total erythrocyte GSH concentration (per gram of hemoglobin [g Hb]) was determined in blood samples from infants with NEC (n = 16) referred for surgical intervention. Nonseptic infants referred for other conditions (eg, patent ductus arteriosus ligation) served as controls (n = 10). RESULTS: Controls and infants with NEC were demographically similar. Mean erythrocyte GSH concentration in infants with NEC was 0.076 +/- 0.004 micromol/g Hb and in controls it was 0.078 +/- 0.005 micromol/g Hb (P = .73). There was no significant correlation between GSH concentration and weight, gestational age, or C-reactive protein levels. In infants with NEC, there was no difference in GSH levels between infants with stage 2 and stage 3 diseases nor between those who died and survived, but a trend toward lower GSH levels in infants with more extensive diseases exists. CONCLUSIONS: Total GSH levels are similar in infants with NEC and controls. It is possible that a relative rather than absolute deficiency of antioxidant compounds exists and may contribute to the development of NEC.

Birth Weight↗
PubMed2005

Inflammatory response in children after laparoscopic vs open Nissen fundoplication: randomized controlled trial.

UNLABELLED: We performed a randomized controlled trial to compare the inflammatory and immune responses to Nissen fundoplication in infants and children undergoing either open or laparoscopic surgery. METHODS: Forty children undergoing Nissen fundoplication were randomized to laparoscopy or open surgery using minimization with respect to age, neurologic status, and operating surgeon. Intraoperative and postoperative analgesias were standardized. Inflammatory markers (plasma malondialdehyde, nitrate plus nitrite level, and cytokines) and monocyte class II major histocompatibility complex expression were measured preoperatively, at end of surgery, 4, 24, and 48 hours postoperatively. Postoperative changes were compared between open and laparoscopic groups. RESULTS: There were no significant changes in circulating malondialdehyde, nitrates plus/ nitrite, interleukin-10, or tumor necrosis factor alpha in the postoperative period in either group. Interleukin-1 receptor antagonist (IL-1rA) and IL-6 were significantly increased in both groups, with a tendency for greater elevation of IL-1rA in the open group. Monocyte major histocompatibility complex expression fell significantly in both groups; however, this fall appeared to be slightly more marked in the open group. CONCLUSIONS: The postoperative cytokine response is similar in children undergoing open and laparoscopic Nissen fundoplication. This trial indicates that laparoscopy may partly reduce postoperative immune suppression.

Child↗
PubMed2005

P-selectin expression, neutrophil infiltration, and histologic injury in neonates with necrotizing enterocolitis.

BACKGROUND/PURPOSE: P-selectin promotes adherence of leukocytes to the endothelium in inflammatory processes. The aim of this study was to investigate the expression of P-selectin and its role in the development of inflammation in neonates with necrotizing enterocolitis (NEC). METHODS: Twenty-nine intestinal specimens from 13 neonates with NEC and 7 control neonates with congenital gastrointestinal abnormalities were studied. Histologic damage, immunohistochemical expression of P-selectin, and polymorphonuclear cell infiltrate were graded blindly. Mann-Whitney U and Spearman rank tests were used to compare grades. RESULTS: Expression of P-selectin was increased in NEC compared with controls in both medium-sized vessels (P = .03) and in the microcirculation (P = .03). P-selectin expression on medium-sized vessels correlated with the degree of histologic injury (P = .02, r = 0.425). P-selectin expression was greatest in areas of active inflammation but markedly lower in necrotic areas. The degree of polymorphonuclear cell infiltration strongly correlated with P-selectin expression on both medium-sized vessels (P = .004, r = 0.513) and the microcirculation (P = .001, r = 0.578). CONCLUSIONS: Expression of P-selectin is increased in medium-sized vessels and in the microcirculation in intestinal specimens of neonates with NEC compared with neonatal controls. Expression of P-selectin is associated with the recruitment of polymorphonuclear cells and the severity of histologic injury, although P-selectin expression is lost in necrotic tissue.

Enterocolitis, Necrotizing↗
PubMed2005

Moderate hypothermia protects against systemic oxidative stress in a rat model of intestinal ischemia and reperfusion injury.

Multisystem organ failure represents a major cause of mortality in intestinal ischemia and reperfusion (I/R), and oxidative stress plays a key role in its pathogenesis. Hypothermia is beneficial in I/R injury, but its effects on systemic oxidative stress have not been elucidated. The aim of this study was to evaluate the effects of moderate hypothermia on systemic oxidative stress after intestinal I/R injury. Anaesthetized adult rats (n = 10 per group) underwent 60 min of intestinal ischemia followed by 120 min of reperfusion or sham operation at normothermia (36 degrees C-38 degrees C) or moderate hypothermia (30 degrees C-32 degrees C). At sacrifice, ileum, liver, lungs, and kidneys were removed to determine the concentration of malondialdehyde (a marker of lipid peroxidation), reduced and oxidized glutathione (a major endogenous antioxidant), and glutathione redox state. Plasma malondialdehyde and nitrate plus nitrite (reflecting nitric oxide production) were also analyzed. A marked elevation of malondialdehyde was observed after I/R at normothermia in plasma, ileum, and lungs; however, hypothermia during I/R prevented this increase. I/R at normothermia caused a profound decrease in reduced glutathione and glutathione redox state in the ileum, but this was not observed in I/R at hypothermia. Interestingly, hypothermia increased glutathione content of control intestine. Nitric oxide production was increased only in normothermic I/R animals. Moderate hypothermia attenuates systemic oxidative stress associated with experimental intestinal I/R in an animal model by decreasing lipid peroxidation in plasma, ileum, lungs, and kidneys, by preventing the depletion of gut glutathione, and by reducing systemic nitric oxide production. However, whether these effects persist after rewarming is unknown.

Animals↗
PubMed2004

The cardioprotective effect of urocortin during ischaemia/reperfusion involves the prevention of mitochondrial damage.

We have previously shown, using Affymetrix gene chip technology, that urocortin induces the expression of several diverse genes in cardiac myocytes. An ATP sensitive inwardly rectifying potassium channel, Katp (Kir6.1), the enzyme calcium independent phospholipase A2 (iPLA2), and protein kinase C epsilon (PKCepsilon) and that these genes are involved in the cardioprotective mechanism of action of urocortin. Here we demonstrate that these gene products are localized to cardiac myocyte mitochondria and for the first time show that urocortin protects cardiac myocytes from ischaemia/reperfusion induced cell death by preventing mitochondrial damage. Using pharmacological agents to Katp channels and iPLA2 and synthetic peptide inhibitors of PKCepsilon, we go on to demonstrate that these three gene products are involved in the urocortin induced protection of cardiac myocyte mitochondria. These proteins may interact at the mitochondria to produce the protective effect.

Aldehydes↗
PubMed2004

Tyrosine nitration of carnitine palmitoyl transferase I during endotoxaemia in suckling rats.

Heart carnitine palmitoyl transferase I (CPTI) is inhibited in vivo during endotoxaemia and in vitro by peroxynitrite but the biochemical basis of this inhibition is not known. The aim of this study was to determine which isoform of CPT I is inhibited during endotoxaemia and whether the inhibition is due to increased tyrosine nitration. Cardiac mitochondria were isolated from endotoxaemic suckling rats. To determine whether M- or L-CPTI was inhibited, we carried out titrations with DNP-etomoxir-CoA. Slopes of the titration curves with DNP-etomoxir-CoA were no different between control and endotoxaemia, suggesting that M-CPTI was specifically inhibited. Immunoprecipitation was carried out using an anti-nitrotyrosine antibody. Immunoprecipitated proteins were identified by Western blotting with L- and M-CPTI specific antibodies. L-CPTI was nitrated both in control and in 2- and 6-h endotoxaemia mitochondria but there was no significant difference in the level of nitration. M-CPTI was also nitrated in control mitochondria but nitration was significantly increased at both 2- and 6-h endotoxaemia. Either 10 mM 3-nitrotyrosine plus 40 microg nitrated-albumin or 0.5 M dithionite, during immunoprecipitation, greatly decreased immunopositivity for M- and L-CPTI on WB. M-CPTI appears to be a novel target for peroxynitrite during endotoxaemia, which would alter myocardial substrate selection.

Acyl Coenzyme A↗
PubMed2004

Melatonin protects from, but does not reverse, the effects of mediators of sepsis on liver bioenergetics.

BACKGROUND: Reactive oxygen species (ROS) have been reported to play a significant role in the pathogenesis of sepsis and liver dysfunction. In particular, neonates are at risk for sepsis and have less protection against oxidation. Melatonin has been reported to reduce the oxidative stress status in neonates with sepsis. Little is known about the effect of melatonin on liver bioenergetics. The aim of this study was to investigate the protective effect of melatonin on hepatocyte oxidative energy metabolism against hydrogen peroxide (H2O2), a free radical mediator of septic damage. METHODS: Hepatocytes were isolated from neonatal suckling rats (11-15 days old). The cells, respiring on palmitate, were exposed to H2O2 at the concentration of 2 mmol/l, melatonin alone at 1 micromol/l or 10 micromol/l, or H2O2 plus melatonin at each of the two concentrations. Oxygen consumption was measured polarographically. In subsequent experiments, melatonin was added after the hydrogen peroxide. RESULTS: Hydrogen peroxide significantly reduced hepatocyte oxygen consumption ( p<0.001), but melatonin added at the same time was able to prevent this effect ( p<0.001). However, melatonin at a low dose significantly inhibited hepatocyte oxygen consumption ( p<0.001), an effect which has not been previously described. When melatonin was added to cells after they had been exposed to hydrogen peroxide, a beneficial effect was not observed, indicating that melatonin is not able to reverse the effects of hydrogen peroxide. CONCLUSION: Melatonin has a protective effect on hepatocyte oxidative metabolism, improving mitochondrial function by counteracting oxidative stress.

Animals↗
PubMed2004

Heart energy metabolism after intestinal ischaemia and reperfusion.

BACKGROUND/PURPOSE: Multiple organ failure subsequent to intestinal ischaemia and reperfusion (I/R) includes cardiac failure, but little is known about heart energy metabolism in this setting. This study investigates the effects of intestinal I/R on heart energy metabolism and evaluates the effects of moderate hypothermia. METHODS: Adult rats underwent intestinal ischaemia for 60 minutes followed by 120 minutes of reperfusion. Animals were maintained at either normothermia (36 degrees to 38 degrees C) or moderate hypothermia (30 degrees to 32 degrees C). In experiment A, 2 groups were studied: (1) sham at normothermia; (2) I/R at normothermia. After death, the heart was removed. Cardiac phosphoenergetics were assessed by 31P magnetic resonance spectroscopy; data are expressed as micromoles per gram. In experiment B, 4 groups were studied: (1) sham at normothermia, (2) I/R at normothermia, (3) sham at hypothermia, (4) I/R at hypothermia. At the end of the experiment, the heart was harvested. The activity of carnitine palmitoyl transferase I (CPT I), an important enzyme in the control of fatty acid oxidation, was measured; data are expressed as nanomoles per minute per unit citrate synthase. Results are expressed as mean +/- SEM. RESULTS: In experiment A, there were no differences between the 2 study groups in cardiac phosphocreatine, inorganic phosphate, adenosine triphosphate (ATP), or in the ratio of inorganic phosphate to ATP. In experiment B, CPT I activity was decreased significantly after I/R at normothermia compared with normothermic sham, but this enzyme inhibition was prevented by hypothermia (3.9 +/- 0.2; v I/R). CONCLUSIONS: These results suggest that although cardiac ATP supply was maintained during intestinal I/R at normothermia, the balance of substrate utilisation was shifted from fatty acid oxidation to carbohydrate utilisation. However, moderate hypothermia modified these changes. The beneficial effect of moderate hypothermia on cardiac metabolism during intestinal I/R has potential clinical application in various surgical conditions.

Adenosine Triphosphate↗