Mitochondrial bioenergetics and redox state are unaltered in Trypanosoma cruzi isolates with compromised mitochondrial complex I subunit genes

In trypanosomatids the involvement of mitochondrial complex I in NADH oxidation has long been debated. Here, we took advantage of natural Trypanosoma cruzi mutants which present conspicuous deletions in ND4, ND5 and ND7 genes coding for complex I subunits to further investigate its functionality. Mitochondrial bioenergetics of wild type and complex I mutants showed no significant differences in oxygen consumption or respiratory control ratios in the presence of NADH-linked substrates or FADH(2)-generating succinate. No correlation could be established between mitochondrial membrane potentials and ND deletions. Since release of reactive oxygen species occurs at complex I, we measured mitochondrial H(2)O(2) formation induced by different substrates. Significant differences not associated to ND deletions were observed among the parasite isolates, demonstrating that these mutations are not important for the control of oxidant production. Our data support the notion that complex I has a limited function in T. cruzi.

Protoporphyrin IX Nanoparticle Carrier: Preparation, Optical Properties, and Singlet Oxygen Generation

The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 mu s, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization.

Generation and suppression of singlet oxygen in hair by photosensitization of melanin

We have studied the spectroscopic properties of hair (white, blond, red, brown, and black) under illumination with visible light, giving special emphasis to the photoinduced generation of singlet oxygen ((1)O(2)). Irradiation of hair shafts (lambda(ex)>400 nm) changed their properties by degrading the melanin. Formation of C3 hydroperoxides in the melanin indol groups was proven by (1)H NMR. After 532-nm excitation, all hair shafts presented the characteristic (1)O(2) emission (lambda(em) = 1270 nm), whose intensity varied inversely with the melanin content. (1)O(2) lifetime was also shown to vary with hair type, being five times shorter in black hair than in blond hair, indicating the role of melanin as a (1)O(2) suppressor. Lifetime ranged from tenths of a nanosecond to a few microseconds, which is much shorter than the lifetime expected for (1)O(2) in the solvents in which the hair shafts were suspended, indicating that (1)O(2) is generated and suppressed inside the hair structure. Both eumelanin and pheomelanin were shown to produce and to suppress (1)O(2), with similar efficiencies. The higher amount of (1)O(2) generated in blond hair and its longer lifetime is compatible with the stronger damage that light exposure causes in blond hair. We propose a model to explain the formation and suppression of (1)O(2) in hair by photosensitization of melanin with visible light and the deleterious effects that an excess of visible light may cause in hair and skin. 2011 Published by Elsevier Inc.

Effects of a high fat diet on liver mitochondria: increased ATP-sensitive K(+) channel activity and reactive oxygen species generation

High fat diets are extensively associated with health complications within the spectrum of the metabolic syndrome. Some of the most prevalent of these pathologies, often observed early in the development of high-fat dietary complications, are non-alcoholic fatty liver diseases. Mitochondrial bioenergetics and redox state changes are also widely associated with alterations within the metabolic syndrome. We investigated the mitochondrial effects of a high fat diet leading to non-alcoholic fatty liver disease in mice. We found that the diet does not substantially alter respiratory rates, ADP/O ratios or membrane potentials of isolated liver mitochondria. However, H(2)O(2) release using different substrates and ATP-sensitive K(+) transport activities are increased in mitochondria from animals on high fat diets. The increase in H(2)O(2) release rates was observed with different respiratory substrates and was not altered by modulators of mitochondrial ATP-sensitive K(+) channels, indicating it was not related to an observed increase in K(+) transport. Altogether, we demonstrate that mitochondria from animals with diet-induced steatosis do not present significant bioenergetic changes, but display altered ion transport and increased oxidant generation. This is the first evidence, to our knowledge, that ATP-sensitive K(+) transport in mitochondria can be modulated by diet.

Crystal and molecular structures of three 2-sulphur-substituted cyclohexanones studied by X-ray crystallography and by ab initio molecular orbital calculations

The conformational features of three 2-sulphur-substituted cyclohexanone derivatives, which differ in the number of sulphur-bound oxygen atoms, i.e. zero (I), one (II) and two (III), were investigated by single crystal X-ray crystallography and geometry optimized structures determined using Hartree-Fock method. In each of (I)-(III) an intramolecular S center dot center dot center dot O(carbonyl) interaction is found with the magnitude correlated with the oxidation state of the sulphur atom, i.e. 2.838(3) angstrom in (I) to 2.924(2) angstrom in (II) to 3.0973(18) angstrom in (III). There is an inverse relationship between the strength of this interaction and the magnitude of the carbonyl bond. The supramolecular aggregation patterns are primarily determined by C-H center dot center dot center dot O contacts and are similarly influenced by the number of oxygen atoms in the molecular structures. Thus, a supramolecular chain is found in the crystal structure of (I). With an additional oxygen atom available to participate in C-H center dot center dot center dot O interactions, as in (II), a two-dimensional array is found. Finally, a three-dimensional network is found for (III). Despite there being differences in conformations between the experimental structures and those calculated in the gas-phase, the S center dot center dot center dot O interactions persist. The presence of intermolecular C-H center dot center dot center dot O interactions involving the cyclohexanone-carbonyl group in the solid-state, disrupts the stabilising intramolecular C-H center dot center dot center dot O interaction in the energetically-favoured conformation. (I): C(12)H(13)NO(3)S, triclinic space group P (1) over bar with a = 5.392(3) angstrom b = 10.731(6) angstrom, c = 11.075(6) angstrom, alpha = 113.424(4)degrees, beta = 94.167(9)degrees, gamma = 98.444(6)degrees, V = 575.5(6) angstrom(3), Z = 2, R(1) = 0.052; (II): C(12)H(13)NO(4)S, monoclinic P2(1)/n, a = 7.3506(15) angstrom, b = 6.7814(14) angstrom, c = 23.479(5) angstrom, beta = 92.94(3)degrees, V = 1168.8(4) angstrom(3), Z = 4, R(1) = 0.046; (III): C(12)H(13)NO(5)S, monoclinic P2(1)/c, a = 5.5491(11) angstrom, b = 24.146(3) angstrom, c = 11.124(3) angstrom, beta = 114.590(10)degrees, V = 1355.3(5) angstrom(3), Z = 4, R(1) = 0.051.

Excited-state dynamics of polyfluorene derivatives in solution

The excited-state dynamics of two polyfluorene copolymers, one fully conjugated containing phenylene vinylene units alternated with 9,9`-dihexylfluorenyl groups and the other segmented by -(CH2)(8)- spacer, were studied in dilute solution of different solvents using a picosecond single-photon timing technique. The excited-state dynamics of the segmented copolymer follows the Forster resonant energy-transfer model which describes intrachain energy-transfer kinetics among random oriented chromophores. Energy transfer is confirmed by analysis of fluorescence anisotropy relaxation with the measurement of a short decay component of about 60 ps. The fluorescence decay surface of the fully conjugated copolymer is biexponential with decay times of about 470 and 900 ps, ascribed to deactivation of chain moieties containing trans and cis isomers already in a photostationary condition. Thus, energy transfer is very fast due to the conjugated nature and rigid-rod-like structure of this copolymer chain.

Dynamic whole system testing of combined renewable heating systems : the current state of the art

Objective: For the evaluation of the energetic performance of combined renewable heating systems that supply space heat and domestic hot water for single family houses, dynamic behaviour, component interactions, and control of the system play a crucial role and should be included in test methods. Methods: New dynamic whole system test methods were developed based on “hardware in the loop” concepts. Three similar approaches are described and their differences are discussed. The methods were applied for testing solar thermal systems in combination with fossil fuel boilers (heating oil and natural gas), biomass boilers, and/or heat pumps. Results: All three methods were able to show the performance of combined heating systems under transient operating conditions. The methods often detected unexpected behaviour of the tested system that cannot be detected based on steady state performance tests that are usually applied to single components. Conclusion: Further work will be needed to harmonize the different test methods in order to reach comparable results between the different laboratories. Practice implications: A harmonized approach for whole system tests may lead to new test standards and improve the accuracy of performance prediction as well as reduce the need for field tests.

Antioxidant defences and homeostasis of reactive oxygen species in different human mitochondrial DNA-depleted cell lines

Three pairs of parental (ρ+) and established mitochondrial DNA depleted (ρ0) cells, derived from bone, lung and muscle were used to verify the influence of the nuclear background and the lack of efficient mitochondrial respiratory chain on antioxidant defences and homeostasis of intracellular reactive oxygen species (ROS). Mitochondrial DNA depletion significantly lowered glutathione reductase activity, glutathione (GSH) content, and consistently altered the GSH2 : oxidized glutathione ratio in all of the ρ0 cell lines, albeit to differing extents, indicating the most oxidized redox state in bone ρ0 cells. Activity, as well as gene expression and protein content, of superoxide dismutase showed a decrease in bone and muscle ρ0 cell lines but not in lung ρ0 cells. GSH peroxidase activity was four times higher in all three ρ0 cell lines in comparison to the parental ρ+, suggesting that this may be a necessary adaptation for survival without a functional respiratory chain. Taken together, these data suggest that the lack of respiratory chain prompts the cells to reduce their need for antioxidant defences in a tissue-specific manner, exposing them to a major risk of oxidative injury. In fact bone-derived ρ0 cells displayed the highest steady-state level of intracellular ROS (measured directly by 2',7'-dichlorofluorescin, or indirectly by aconitase activity) compared to all the other ρ+ and ρ0 cells, both in the presence or absence of glucose. Analysis of mitochondrial and cytosolic/iron regulatory protein-1 aconitase indicated that most ROS of bone ρ0 cells originate from sources other than mitochondria.

Dynamic output feedback control of single-link flexible manipulators

This paper presents an efficient technique to design dynamic feedback control scheme for single-link flexible manipulators.  A linear model can be derived for the robotic system using the assumed-mode method.  Conventional techniques such as pole-placement or LQR require physical measurements of all systme states,  posing a stringent requirement for its implementation.  To overcome this problem, a low-order state functional observer is proposed here for reconstruction of the state feedback control action.  The observer design involves solving an optimisation problem with the objective to generate a feedback gain that is as close as possible to that of the required feedback controller.  A condition for robust stability of the closed-loop system under the observer-based control scheme is given.  The attractive features of the propsed technique are the resulted functional state observer is of a very low order and it requires only sensor measurements of only the output- the tip position of the arm.

Incorporation of oxygen into the succinate co-product of iron(II) and 2-oxoglutarate dependent oxygenases from bacteria, plants and humans.

The ferrous iron and 2-oxoglutarate (2OG) dependent oxygenases catalyse two electron oxidation reactions by coupling the oxidation of substrate to the oxidative decarboxylation of 2OG, giving succinate and carbon dioxide coproducts. The evidence available on the level of incorporation of one atom from dioxygen into succinate is inconclusive. Here, we demonstrate that five members of the 2OG oxygenase family, AlkB from Escherichia coli, anthocyanidin synthase and flavonol synthase from Arabidopsis thaliana, and prolyl hydroxylase domain enzyme 2 and factor inhibiting hypoxia-inducible factor-1 from Homo sapiens all incorporate a single oxygen atom, almost exclusively derived from dioxygen, into the succinate co-product.

Science education in primary schools in a state of change

Through a longitudinal study of one teacher's science teaching practice set in the context of her base school, this thesis records the effects of the structural and policy changes that have occurred in Victorian education over the past 6-7 years - the 'Kennett era'. Initially, the purpose of the study was to investigate the teacher's practice with the view to improving it. For this, an action research approach was adopted. Across the year 1998, the teacher undertook an innovative science program with two grades, documenting the approach and outcomes. Several other teachers were involved in the project and their personal observations and comments were to form part of the data. This research project was set in the context of a single primary school and case study methodology was used to document the broader situational and daily influences which affected the teacher's practice. It was apparent soon after starting the action research that there were factors which did not allow for the development of the project along the intended lines. By the end of the project, the teacher felt that the action research had been distorted - specifically there had been no opportunity for critical reflection. The collaborative nature of the project did not seem to work. The teacher started to wonder just what had gone wrong. It was only after a break from the school environment that the teacher-researcher had the opportunity to really reflect on what had been happening in her teaching practice. This reflection took into account the huge amount of data generated from the context of the school but essentially reflected on the massive number of changes that were occurring in all schools. Several issues began to emerge which directly affected teaching practice and determined whether teachers had the opportunity to be self-reflective. These issues were identified as changes in curriculum and the teaching role, increased workload, changed power relations and changed security/morale on the professional context. This thesis investigates the structural and policy changes occurring in Victorian education by reference to documentation and the lived experiences of teachers. It studies how the emerging issues affect the practices of teachers, particularly the teacher-researcher. The case study has now evolved to take in the broader context of the policy and structural changes whilst the action research has expanded to look at the ability of a teacher to be self-reflective: a meta-action research perspective. In concluding, the teacher-researcher reflects on the significance of the research in light of the recent change in state government and the increased government importance placed on science education in the primary context.

A single-step synthesized cobalt-free barium ferrites-based composite cathode for intermediate temperature solid oxide fuel cells

Cobalt-free perovskite cathode with excellent oxygen reduction reaction (ORR) properties below 800 °C is a key material toward wide implementation of intermediate-temperature solid oxide fuel cells. This work reports the phase structure, microstructure and performance of such cathode based on the composite phases of triclinic Ba0.9Bi0.1FeO3-δ, cubic BaFeO3 and orthorhombic BaFe2O4 prepared by sol–gel route. The resultant barium ferrites composite cathode exhibits uniform particles, pores and elements distribution. In particular, favorable ORR properties of this cathode is demonstrated by very low interfacial resistance of only 0.036 and 0.072 Ω cm2 at 750 and 700 °C and maximum power density of 1295 and 840 mW cm−2 at 750 and 700 °C.

Multiple identification and risks : examination of peer factors across multiracial and single-race youth

Multiracial youth are thought to be more vulnerable to peer-related risk factors than are single-race youth. However, there have been surprisingly few well-designed studies on this topic. This study empirically investigated the extent to which multiracial youth are at higher risk for peer influenced problem behavior. Data are from a representative and longitudinal sample of youth from Washington State (N = 1,760, mean age = 14.13, 50.9% girls). Of those in the sample, 225 youth self-identified as multiracial (12.8%), 1,259 as White (71.5%), 152 as Latino (8.6%), and 124 as Asian American (7.1%). Results show that multiracial youth have higher rates of violence and alcohol use than Whites and more marijuana use than Asian Americans. Higher levels of socioeconomic disadvantage and single-parent family status partly explained the higher rates of problem behaviors among multiracial youth. Peer risk factors of substance-using or antisocial friends were higher for multiracial youth than Whites, even after socioeconomic variables were accounted for, demonstrating a higher rate of peer risks among multiracial youth. The number of substance-using friends was the most consistently significant correlate and predictor of problems and was highest among multiracial youth. However, interaction tests did not provide consistent evidence of a stronger influence of peer risks among multiracial youth. Findings underscore the importance of a differentiated understanding of vulnerability in order to better target prevention and intervention efforts as well as the need for further research that can help identify and explain the unique experiences and vulnerabilities of multiracial youth.

Oxygen dependence of metabolism and cellular adaptation in vertebrate muscles: a review

The key roles the cardiovascular system play in the complex distribution of blood, and consequently oxygen, have been extensively studied in vertebrates. Numerous studies have also revealed the complex and varied ways in which tissues cope with compromised oxygen supply. The links between these two processes are the subject of much current research. This article aims to review how blood supply influences tissue oxygenation and affects metabolism, and how this might have played a role in the evolution of the complex muscle arrangements which characterise vertebrates. Muscle tissue is the greatest proportion of body mass in most vertebrates and undergoes dramatic alterations in metabolism and associated oxygen flux. Special attention is given to the myotome of fishes, in which the partitioning of the fibre types contrasts with the mosaic arrangement of tetrapods. This gives us the opportunity to study pure whole vascularised muscle blocks, rather than single fibres, and further explore the interrelationship between oxygen supply and tissue energetics.