Mortality risks in patients with constitutional autosomal chromosome deletions in Britain: a cohort study

Constitutional chromosome deletions result in wide ranging morbidity and often fatality. Information about risks and causes of death in these patients is important for counselling, and may illuminate the functions of the part of the chromosome deleted. There have been no cohort studies analysing mortality risks in persons with specific deletions compared with general population rates. We therefore conducted a cohort study following cause-specific mortality in 2,561 patients with autosomal chromosome deletions diagnosed by light microscopy or fluorescence in situ hybridisation at cytogenetic laboratories across Britain, 1965–2002. The commonest deletions were of 22q (544 patients), 15q (460) and 7q (210) and the least common 19q (0) and 20q (2). The prevalence of visible deletions of different chromosome arms was significantly inversely correlated with gene density of the arm (p < 0.001). Mortality was 11-fold raised in the cohort compared with the general population (standardised mortality ratio = 11.4 (95% confidence interval 10.0–12.8)), was significantly raised for each deletion with ≥25 subjects in the study, and had a lower confidence limit >10 for deletions of 1p, 1q, 3p, 4p, 5q and 22q. Overall, 29% of deaths were due to congenital anomalies; significantly raised mortality occurred also from many other causes, varying by chromosome and arm of deletion. The data imply that viability of foetuses with visible chromosome deletions may be inversely related to gene density, and that all visible and fluorescence in situ hybridisation-detectable deletions lead to much raised mortality, but the extent and causes of mortality vary according to the specific deletion. The UK Clinical Cytogenetics Group comprises: The above, plus Paul J Batstone (Inverness Genetics Laboratory), Thomas Spencer (NE London Regional Cytogenetics Laboratory, Great Ormond Street Hospital), Teresa Davies (Bristol Genetics Laboratory), Valerie Davison (Birmingham Genetics Laboratory), Zoe Docherty (SE Thames, Guy’s Hospital Genetics Laboratory), David P. Duckett (Leicestershire Genetics Centre), Margaret Fitchett (Oxford Genetics Laboratory), Alison Fordyce (MRC Human Genetics Unit, Edinburgh); Lorraine Gaunt (Manchester Genetics Laboratory), Elizabeth Grace (Edinburgh Genetics Laboratory), Peter Howard (Liverpool Genetics Laboratory), Gordon W. Lowther (Glasgow Genetics Laboratory), Christine Maliszewska (Dundee Genetics Laboratory), Edna L. Maltby (Sheffield Genetics Laboratory), Kevin P. Ocraft (Nottingham Genetics Laboratory); Selwyn Roberts (Wales Genetics Laboratory), Kim K. Smith (Cambridge Genetics Laboratory), Gordon S. Stephen (Aberdeen Genetics Laboratory), John W. Taylor (SW Thames, St George’s Hospital Genetics Laboratory), Catherine S. Waters (NW Thames, Northwick Park Hospital Genetics Laboratory), Jeffery Williams (Leeds Genetics Laboratory), John Wolstenholme (Newcastle Genetics Laboratory), Sheila Youings (Wessex Regional Genetics Laboratory).     

O(2)-sensing signal cascade: clamping of O(2) respiration, reduced ATP utilization, and inducible fumarate respiration

These studies explore the consequences of activating the prolyl hydroxylase (PHD) O(2)-sensing pathway in spontaneously twitching neonatal cardiomyocytes. Full activation of the PHD pathway was achieved using the broad-spectrum PHD inhibitor (PHI) dimethyloxaloylglycine (DMOG). PHI treatment of cardiomyocytes caused an 85% decrease in O(2) consumption and a 300% increase in lactic acid production under basal conditions. This indicates a approximately 75% decrease in ATP turnover rate, inasmuch as the increased ATP generation by glycolysis is inadequate to compensate for the lower respiration. To determine the extent to which decreased ATP turnover underlies the suppressed O(2) consumption, mitochondria were uncoupled with 2,4-dinitrophenol. We were surprised to find that 2,4-dinitrophenol failed to increase O(2) consumption by PHI-treated cells, indicating that electron transport chain activity, rather than ATP turnover rate, limits respiration in PHI-treated cardiomyocytes. Silencing of hypoxia-inducible factor-1alpha (HIF-1alpha) expression restored the ability of uncoupled PHI-treated myocytes to increase O(2) consumption; however, basal O(2) uptake rates remained low because of the unabated suppression of cellular ATP consumption. Thus it appears that respiration is actively "clamped" through an HIF-dependent mechanism, whereas HIF-independent mechanisms are responsible for downregulation of ATP consumption. In addition, we find that PHD pathway activation enables mitochondria to utilize fumarate as a terminal electron acceptor when cytochrome c oxidase is inactive. The source of fumarate for this unusual respiration is derived from aspartate via the purine nucleotide cycle. In sum, these studies show that the O(2)-sensing pathway is sufficient to actively "clamp" O(2) consumption and independently suppress cellular ATP consumption. The PHD pathway also enables the mitochondria to utilize fumarate for respiration.     

Thermal tolerance of contractile function in oxidative skeletal muscle: no protection by antioxidants and reduced tolerance with eicosanoid enzyme inhibition

Mechanisms for the loss of muscle contractile function in hyperthermia are poorly understood. This study identified the critical temperature, resulting in a loss of contractile function in isolated diaphragm (thermal tolerance), and then tested the hypotheses 1) that increased reactive oxygen species (ROS) production contributes to the loss of contractile function at this temperature, and 2) eicosanoid metabolism plays an important role in preservation of contractile function in hyperthermia. Contractile function and passive force were measured in rat diaphragm bundles during and after 30 min of exposure to 40, 41, 42 or 43 degrees C. Between 40 and 42 degrees C, there were no effects of hyperthermia, but at 43 degrees C, a significant loss of active force and an increase in passive force were observed. Inhibition of ROS with the antioxidants, Tiron or Trolox, did not inhibit the loss of contractile force at 43 degrees C. Furthermore, treatment with dithiothreitol, a thiol (-SH) reducing agent, did not reverse the effects of hyperthermia. A variety of global lipoxygenase (LOX) inhibitors further depressed force during 43 degrees C and caused a significant loss of thermal tolerance at 42 degrees C. Cyclooxygenase (COX) inhibitors also caused a loss of thermal tolerance at 42 degrees C. Blockage of phospholipase with phospholipase A(2) inhibitors, bromoenol lactone or arachidonyltrifluoromethyl ketone failed to significantly prevent the loss of force at 43 degrees C. Overall, these data suggest that ROS do not play an apparent role in the loss of contractile function during severe hyperthermia in diaphragm. However, functional LOX and COX enzyme activities appear to be necessary for maintaining normal force production in hyperthermia.     

Cumulative funnel plots for the early detection of interoperator variation: retrospective database analysis of observed versus predicted results of percutaneous coronary intervention

Objective To use funnel plots and cumulative funnel plots to compare in-hospital outcome data for operators undertaking percutaneous coronary interventions with predicted results derived from a validated risk score to allow for early detection of variation in performance.Design Analysis of prospectively collected data.Setting Tertiary centre NHS hospital in the north east of England.Participants Five cardiologists carrying out percutaneous coronary interventions between January 2003 and December 2006.Main outcome measures In-hospital major adverse cardiovascular and cerebrovascular events (in-hospital death, Q wave myocardial infarction, emergency coronary artery bypass graft surgery, and cerebrovascular accident) analysed against the logistic north west quality improvement programme predicted risk, for each operator. Results are displayed as funnel plots summarising overall performance for each operator and cumulative funnel plots for an individual operator’s performance on a case series basis.Results The funnel plots for 5198 patients undergoing percutaneous coronary interventions showed an average observed rate for major adverse cardiovascular and cerebrovascular events of 1.96% overall. This was below the predicted risk of 2.06% by the logistic north west quality improvement programme risk score. Rates of in-hospital major adverse cardiovascular and cerebrovascular events for all operators were within the 3σ upper control limit of 2.75% and 2σ upper warning limit of 2.49%.Conclusion The overall in-hospital major adverse cardiovascular and cerebrovascular events rates were under the predicted event rate. In-hospital rates after percutaneous coronary intervention procedure can be monitored successfully using funnel and cumulative funnel plots with 3σ control limits to display and publish each operator’s outcomes. The upper warning limit (2σ control limit) could be used for internal monitoring. The main advantage of these charts is their transparency, as they show observed and predicted events separately. By this approach individual operators can monitor their own performance, using the predicted risk for their patients but in a way that is compatible with benchmarking to colleagues, encapsulated by the funnel plot. This methodology is applicable regardless of variations in individual operator case volume and case mix.     

Seasonal dynamics of soil micronutrients in compost-amended bermudagrass turf

Compost application to turfgrasses can increase plant-available nutrient concentrations in soil and improve growth, but may alter micronutrient dynamics and increase leaching and runoff losses. The objectives of this study were to investigate the influence of compost on the seasonal dynamics of plant-available Mn, Fe, Cu, and Zn in soil after a single application to bermudagrass [Cynodon dactylon (L.) Pers.] turf. Extractable Mn increased from 270 to 670 mg kg(-1) and Cu from 0.36 to 9.89 mg kg(-1) from 0 to 29 months. In contrast, extractable Fe and Zn decreased by 52% and 57% during the same time period. Seasonal trends in extractable Mn and Cu were closely related to dissolved organic C (DOC), and appeared influenced by bermudagrass growth and dormancy patterns and subsequent impacts on DOC. Losses of Mn and Cu from the soil surface occurred after high levels of precipitation during winter dormancy but not during the growing season, while Fe and Zn exhibited an opposite pattern. Thus, seasonal variation of soil micronutrients was likely related to seasonal patterns of bermudagrass growth and dormancy and their effects on DOC, and precipitation events which probably leached DOC and complexed nutrients from surface soil. Composts only influenced the magnitude of changes in micronutrient concentrations, as similar seasonal trends occurred for both compost-amended and unamended soils.     

Molecular Diversity of Rumen Methanogens from Sheep in Western Australia

The molecular diversity of rumen methanogens in sheep in Australia was investigated by using individual 16S rRNA gene libraries prepared from the rumen contents obtained from six merino sheep grazing pasture (326 clones), six sheep fed an oaten hay-based diet (275 clones), and five sheep fed a lucerne hay-based diet (132 clones). A total of 733 clones were examined, and the analysis revealed 65 phylotypes whose sequences (1,260 bp) were similar to those of cultivated methanogens belonging to the order Methanobacteriales. Pasture-grazed sheep had more methanogen diversity than sheep fed either the oaten hay or lucerne hay diet. Methanobrevibacter strains SM9, M6, and NT7 accounted for over 90% of the total number of clones identified. M6 was more prevalent in grazing sheep, and SM9, despite being found in 16 of the 17 sheep, was more prevalent in sheep fed the lucerne-based diet. Five new species were identified. Two of these species exhibited very little sequence similarity to any cultivated methanogens and were found eight times in two of the six sheep that were grazing pasture. These unique sequences appear to represent a novel group of rumen archaea that are atypical for the rumen environment.     

Conformational relaxation following hydride transfer plays a limiting role in dihydrofolate reductase catalysis

The catalytic cycle of an enzyme is frequently associated with conformational changes that may limit maximum catalytic throughput. In Escherichia coli dihydrofolate reductase, release of the tetrahydrofolate (THF) product is the rate-determining step under physiological conditions and is associated with an "occluded" to "closed" conformational change. In this study, we demonstrate that in dihydrofolate reductase the closed to occluded conformational change in the product ternary complex (E.THF.NADP (+)) also gates progression through the catalytic cycle. Using NMR relaxation dispersion, we have measured the temperature and pH dependence of microsecond to millisecond time scale backbone dynamics of the occluded E.THF.NADP (+) complex. Our studies indicate the presence of three independent dynamic regions, associated with the active-site loops, the cofactor binding cleft, and the C-terminus and an adjacent loop, which fluctuate into discrete conformational substates with different kinetic and thermodynamic parameters. The dynamics of the C-terminally associated region is pH-dependent (p K a < 6), but the dynamics of the active-site loops and cofactor binding cleft are pH-independent. The active-site loop dynamics access a closed conformation, and the accompanying closed to occluded rate constant is comparable to the maximum pH-independent hydride transfer rate constant. Together, these results strongly suggest that the closed to occluded conformational transition in the product ternary complex is a prerequisite for progression through the catalytic cycle and that the rate of this process places an effective limit on the maximum rate of the hydride transfer step.     

Antioxidant enzymes, free-radical damage, and response to paraquat in liver and kidney of long-living growth hormone receptor/binding protein gene-disrupted mice.

Numerous studies have shown that the lifespan can be extended by caloric restriction or by altering the growth hormone (GH)-insulin-like growth factor 1 signaling pathway. Both of these manipulations produce physiological alterations, such as increased insulin sensitivity, and reduced glucose levels and body size. However, it is difficult to evaluate whether these are merely correlates of delayed aging or whether they have a direct causal effect on lifespan. One parameter that has been demonstrated to have causal, positive effects on longevity in invertebrates is improved antioxidant defenses. We measured activities of antioxidant enzymes Cu/Zn superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and quantified free-radical damage by lipid peroxidation (LP) and protein oxidation (PO) measurements in liver and kidney tissues, and evaluated the response to paraquat-induced oxygen toxicity in the long-living GH receptor/binding protein gene knockout (GHR-KO) mouse. We found that in the kidney, SOD was lower and GPx was higher in GHR-KO mice, and LP was higher in female GHR-KO mice only. In the liver, female GHR-KO mice had lower GPx, while male GHR-KO mice had lower CAT and higher LP. GHR-KO males were also more susceptible to paraquat toxicity compared to females or normal males. We conclude that in long-living GHR-KO mice, GH-resistance does not confer longevity by improved free-radical scavenging in the liver and kidney, suggesting that greater free-radical defenses in other tissues, or altered glucose metabolism may have a more central role in extending the lifespan of these animals.