The Effect of Single and Combined Heat and CO2 Stimuli at Different Ambient Temperatures on the Behavior of Two Plant-Parasitic Nematodes

Pratylenchus penetrans and Ditylenchus dipsaci were reared at 15-16 C, and their behavior towards single and combined heat and CO₂ stimuli was studied at ambient temperatures of 8.6 and 27.3 C. At the lower temperature, attractivity of the heat source was prevalent in both species, but CO₂ was also attractive. At the higher ambient temperature (27.3 C), the reaction to CO₂ was more positive and more rapid than to heat. In fact, at this temperature only D. dipsaci was attracted to the heat source, whereas P. penetrans did not react positively. The combined stimulation of heat and CO₂ caused D. dipsaci to aggregate more strongly than did a single stimulus; this applied to both ambient temperatures. For P. penetrans exposed to the low temperature (8.6 C), the combined stimuli were about as attractive as was the better of the single stimuli; i.e., heat. At the high temperature (27.3 C), the combined stimulation was less effective than the better of the single stimuli; i.e., CO₂. At this ambient temperature, the thermonegative reaction seems to dominate over the CO₂-positive one. The reaction of D. dipsaci was generally stronger in all experimental variants than that of P. penetrans. Insofar as temperature gradients play a role in locating host plant roots, their efficacy would seem to be restricted to a favorable temperature range. Within this range, combined heat and CO₂ stimuli might improve attractivity.     

Mechanistic insights into the superoxide–cytochrome c reaction by lysine surface scanning

This study summarizes results which have been obtained by a mutational study of human cytochrome c. The protein can be used as a recognition element in analytical assays and biosensors for superoxide radicals since ferricytochrome c reacts with superoxide to form ferrocytochrome c and oxygen. Here lysine mutagenesis of the distal surface (i.e., of exposed residues around the Met80 axial ligand) of human cytochrome c was pursued to evaluate the effect of the surface charges on the reaction rate with the superoxide anion radical and on the redox properties of the heme protein. The latter feature is particularly relevant when the protein is immobilized on a negatively charged self-assembled monolayer on an electrode to be used as a biosensor. The observed effects of the mutations are rationalized through structural investigations based on solution NMR spectroscopy and computational analysis of the surface electrostatics. The results suggest the presence of a specific path that guides superoxide toward an efficient reaction site. Localized positive charges at the rim of the entry channel are effective in increasing the reaction rate, whereas diffused positive charges or charges far from this area are not effective or are even detrimental, resulting in a misguided approach of the anion to the protein surface.     

Effect of temperature and pressure on the protonation of glycine

Flow calorimetry has been used to study the interaction of glycine with protons in water at temperatures of 298.15, 323.15, and 348.15 K and pressures up to 12.50 MPa. By combining the measured heat for glycine solutions titrated with NaOH with the heat of ionization for water, the enthalpy of protonation of glycine is obtained. The reaction is exothermic at all temperatures and pressures studied. The effect of pressure on the enthalpy of reaction is very small. The experimental heat data are analyzed to yield equilibrium constant (K), enthalpy change (ΔH), and entropy change (ΔS) values for the protonation reaction as a function of temperature. These values are compared with those reported previously at 298.15 K. The ΔH and ΔS values increase (become more positive), whereas log K values decrease, as temperature increases. The trends for ΔH and ΔS with temperature are opposite to those reported previously for the protonation of several alkanolamines. However, log K values for proton interaction with both glycine and the alkanolamines decrease with increasing temperature. The effect of the nitrogen atom substituent on log K for protonation of glycine and alkanolamines is discussed in terms of changes in long-range and short-range solvent effects. These effects are used to explain the difference in ΔH and ΔS trends between glycine protonation and those found earlier for alkanolamine protonation.     

Reaction of Oxyhemoglobin with Carbon Monoxide

The reaction of oxyhemoglobin and carbon monoxide was studied kinetically at pH 7.8 in a variety of suspending media. The dielectric constant of the suspending media, as well as the viscosity (and hence the Fick diffusion coefficients), was varied with the use of glycine, glycerol, and sucrose. The results showed that the reaction was unaltered by the various additions to the media, provided that the pO₂ and the concentration of carbon monoxide were held constant. Since the concentration of oxygen varies from medium to medium at constant pO₂ while the pCO varies at constant concentration of carbon monoxide, the differences in the reactions with oxygen and carbon monoxide were emphasized. The lack of variation of the rate constants with changes in dielectric constant can be interpreted as indicating that electrostatic effects are unimportant in this reaction.     

The enthalpy of oxidation of flavin mononucleotide

The oxidation enthalpy of reduced flavin mononucleotide at pH 7.0 in 0.2 m phosphate buffer has been studied by determining the heat associated with the reaction: FMNH₂ + 2 Fe(CN)^?3₆ ? FMN + 2 Fe(CN)^?4₆ + 2 H⁺. (a) (The quinone, semiquinone, and hydroquinone forms of FMN are represented as FMN, FMNH, and FMNH₂, respectively.) Calorimetric experiments were performed in a flow microcalorimeter which was modified to prevent sample contamination by oxygen. The enthalpy observed for reaction (a), after correction for dilution and buffer effects, was ?39.2 ± 0.4 kcal (mole FMNH₂)^?1 at 25 °C. The potential difference, ΔE′, developed by reaction (a) was determined potentiometrically and corresponded to a free energy change, ΔG′, of ?30.3 kcal (mole FMNH₂)^?1. The resulting entropy change, ΔS′, was thus calculated to be ?29.8 e.u. Reaction (a) was also studied at temperatures of 7 °C and 35.5 °C. ΔC_p′ for the reaction was calculated as ?155 ± 18 cal deg^?1 (mole FMNH₂)^?1 at 20 °C. ΔH′ for the reaction (b), FMNH₂ ? FMN + H₂, (b) was calculated as +14.2 ± 0.7 kcal mole^?1 at 25 °C, relative to the enthalpy of the hydrogen electrode being identically equal to zero at all values of pH and temperature. The free energy at pH 7.0 for reaction (b), calculated from the potential was found to be ?9.7 kcal mole^?1, which resulted in an entropy for reaction (b) of 80.2 e.u. A thermal titration of reaction (a) was used to calculate the thermodynamic parameters for the formation of semiquinone dimer according to the reaction FMNH₂ + FMN ? (·FMNH)₂. (c) The free energy, enthalpy, and entropy changes for reaction (c) were estimated to be ?6.1 kcal mole^?1, ?7 kcal mole^?1, and ?3 e.u., respectively.     

Ecophysiological response of native and invasive <Emphasis Type="Italic">Spartina</Emphasis> species to extreme temperature events in Mediterranean marshes

The recent IPCC WG2 5th Assessment Report (IPCC 2014), notes an increase in the frequency and duration of extreme climatic events, especially for the Mediterranean region. Together with climate change, the invasion of natural communities by non-indigenous species (NIS) constitutes a serious threat to biodiversity. One of these NIS is the American Spartina patens, now present in Western European marshes. The present study aims to understand the biochemical and photochemical responses of S. patens compared with S. maritima under extreme temperature events. Under normal and extreme heat conditions, S. patens had a higher photosynthetic efficiency (α), compared with cold wave events, where the native S. maritima was far more efficient. This reduced photosynthetic efficiency was mostly due to a decrease in the connectivity between photosystem II (PSII) antennae. This was accompanied by severe damage to the oxygen-evolving complex of PSII. On the other hand, S. patens oxygen evolving complexes (OECs) seem to be temperature insensitive. The light absorption capacity was maintained due to a higher net rate of reaction centre (RC) closure as a counteractive measure of the reduced number of RC, especially in S. maritima. The loss of connectivity between PSII antennae and damage in OECs under heat stress leads to a severe reduction in the maximum yield for photochemistry enhanced by the low probability of each absorbed quanta to produce electronic work. However, while S. maritima presents high energy losses under heat stress, S. patens developed efficient quenching mechanisms under thermal stress, through auroxanthin. In S. patens, cold wave-treated individuals also displayed a very active line of enzymatic defences for reactive oxygen species scavenging. In fact, only cold treated individuals of this species presented higher activities of anti-oxidant enzymes, revealing some degree of adaptation to this new environment. In contrast, in S. maritima the exposure to extreme heat periods led, in most cases, to a decrease in the enzymatic defences, leaving the cell prone to oxidative damage. In summary, S. patens appears to have a higher fitness for the incoming climatic scenarios, being more tolerant to heat stress, while S. maritima will have its photobiological fitness decreased. This will impose a shift in the salt marsh biodiversity, favouring the non-indigenous S. patens expansion.     

Improved production of monoclonal antibodies through oxygen-limited cultivation of glycoengineered yeast

Glycoengineering technology can elucidate and exploit glycan related structure-function relationships for therapeutic proteins. Glycoengineered yeast has been established as a safe, robust, scalable, and economically viable expression platform. It has been found that specific productivity of antibodies in glycoengineered Pichia pastoris is a non-linear function of specific growth rate that is dictated by a limited methanol feed rate. The optimal carbon-limited cultivation requires an exponential methanol feed rate with an increasing biomass concentration and more significantly an increase in heat and mass transfer requirements that often become the limiting factor in scale-up. Both heat and mass transfer are stoichiometrically linked to the oxygen uptake rate. Consequently an oxygen-limited cultivation approach was evaluated to limit the oxygen uptake rate and ensure robust and reliable scale-up. The oxygen-limited process not only limited the maximum oxygen uptake rate (and consequently the required heat removal rate) in mut+ P. pastoris strains but also enabled extension of the induction phase leading to an increased antibody concentration (1.9 g L⁻¹ vs. 1.2 g L⁻¹), improved N-glycan composition and galactosylation, and reduced antibody fragmentation. Furthermore, the oxygen-limited process was successfully scaled to manufacturing pilot scale and thus presents a promising process option for the glycoengineered yeast protein expression platform.     

Excitonic connectivity between photosystem II units: what is it, and how to measure it?

In photosynthetic organisms, light energy is absorbed by a complex network of chromophores embedded in light-harvesting antenna complexes. In photosystem II (PSII), the excitation energy from the antenna is transferred very efficiently to an active reaction center (RC) (i.e., with oxidized primary quinone acceptor Q _A), where the photochemistry begins, leading to O₂ evolution, and reduction of plastoquinones. A very small part of the excitation energy is dissipated as fluorescence and heat. Measurements on chlorophyll (Chl) fluorescence and oxygen have shown that a nonlinear (hyperbolic) relationship exists between the fluorescence yield (Φ _F ) (or the oxygen emission yield, $ \Phi _{{{\text{O}}_{2} }} $ ) and the fraction of closed PSII RCs (i.e., with reduced Q _A). This nonlinearity is assumed to be related to the transfer of the excitation energy from a closed PSII RC to an open (active) PSII RC, a process called PSII excitonic connectivity by Joliot and Joliot (CR Acad Sci Paris 258: 4622–4625, 1964). Different theoretical approaches of the PSII excitonic connectivity, and experimental methods used to measure it, are discussed in this review. In addition, we present alternative explanations of the observed sigmoidicity of the fluorescence induction and oxygen evolution curves.     

Changes of the surface structure of corn stalk in the cooking process with active oxygen and MgO-based solid alkali as a pretreatment of its biomass conversion

This study presents a novel, efficient and environmentally friendly process for the cooking of corn stalk that uses active oxygen (O₂ and H₂O₂) and a recoverable solid alkali (MgO). The structural changes on the surface of corn stalk before and after cooking were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The results showed that lignin and extractives were effectively removed, especially those on the surface of corn stalk. Additionally, the changes included becoming fibrillar, the exposure of cellulose and hemi-cellulose and the pitting corrosion on the surface, etc. The results also showed that the removal reaction is from outside to inside, but the main reaction is possibly on the surface. Furthermore, the results of active oxygen cooking with a solid alkali are compared with those of alkaline cooking in the paper.     

Tunable Internal and Surface Structures of the Bifunctional Oxygen Perovskite Catalysts

Perovskite oxide ceramics attracts significant attention as a strong candidate of bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalyst for the metal‐air batteries. Numerous approaches to the viability of bifunctional perovskite electrocatalyst represent that the electro­chemical performance is highly correlated with defect chemistry, surface structure, and overall polycrystalline perovskite structure. By making use of the intrinsic flexibility of internal structure and high nonstoichiometry in perovskite oxide, the heat treatment effect of the complex Ba_0.5Sr_0.5Co_xFe_1‐xO_3‐δ (x = 0.2 and 0.8) perovskites in argon atmosphere at 950 °C (Ar‐BSCF5582 and Ar‐BSCF5528) on the surface structure/defect chemistry and electrocatalytic performance is intensively investigated. Upon heat‐treatment in argon atmosphere, the amorphous thickness layer increases from ≈20 to 180–200 nm in BSCF5582, while there is little change in BSCF5528 with ≈20 nm. The electrocatalytic performance of BSCF5582 catalyst both in ORR and OER deteriorates seriously, while Ar‐BSCF5528 demonstrates a significant increase of electro­chemical performance in ORR. This study demonstrates that the electrochemical performances of a perovskite catalyst can be significantly determined by the simultaneous modification of both surface structure and internal defect chemistry, which are explained with transmission electron microscopy and atomic‐selective X‐ray absorption fine structure analyses, respectively.     

Reaction of oxygen with the respiratory chain in cells and tissues

This paper considers the way in which the oxygen reaction described by Dr. Nicholls and the ADP control reactions described by Dr. Racker could cooperate to establish a purposeful metabolic control phenomenon in vivo. This has required an examination of the kinetic properties of the respiratory chain with particular reference to methods for determinations of oxygen affinity (K_m). The constant parameter for tissue respiration is k ₁, the velocity constant for the reaction of oxygen with cytochrome oxidase. Not only is this quantity a constant for a particular tissue or mitochondria; it appears to vary little over a wide range of biological material, and for practical purposes a value of 5 x 10⁷ at 25° close to our original value (20) is found to apply with adequate accuracy for calculation of K_m for mammalia. The quantity which will depend upon the tissue and its metabolic state is the value of K_m itself, and K_m may be as large as 0.5 µM and may fall to 0.05 µM or less in resting, controlled, or inhibited states. The control characteristic for ADP may depend upon the electron flux due to the cytochrome chain (40); less ADP is required to activate the slower electron transport at lower temperatures than at higher temperatures. The affinity constants for ADP control appear to be less dependent upon substrate supplied to the system. The balance of ADP and oxygen control in vivo is amply demonstrated experimentally and is dependent on the oxygen concentration as follows. In the presence of excess oxygen, control may be due to the ADP or phosphate (or substrate), and the kinetics of oxygen utilization will be independent of the oxygen concentration. As the oxygen concentration is diminished, hemoglobin becomes disoxygenated, deep gradients of oxygen concentration develop in the tissue, and eventually cytochrome oxidase becomes partially and then completely reduced. DPN at this point will become reduced and the electron flow diminished. The rate of ATP production falls and energy conservation previously under the control of the ADP concentration will now be controlled by the diffusion of oxygen to the respiratory enzymes in the mitochondria. Under these conditions the rate of reaction of cytochrome oxidase with oxygen and the reaction of cytochromes with one another become of key importance. The rise of ADP and the depletion of energy reserves evoke glycolytic activity, and failure of biological function may result.     

Hemin-mediated para-hydroxylation of aniline: A potential model for oxygen activation and insertion reactions of mixed function oxidases

The activation of molecular oxygen by alkaline hemin (ferriprotoporphyrin IX) has been studied. In the presence of reductant nicotineamide adenine dinucleotide (NADH) or nicotineamide adenine dinucleotide phosphate (NADPH) and organic substrate, aniline, hemin activates oxygen to the hydroperoxide anion (HO₂^?) and subsequently mediates insertion of active oxygen into the benzene ring of the substrate to form p-aminophenol, with a high degree of regiospecificity. Oxygen activation does not occur in the absence of aniline. Stoichiometry of the reaction indicates that two electrons are required per molecule of oxygen activated or atom of oxygen inserted into the substrate aromatic ring system. Direct measurements of H₂O₂ and of the pK_a for maximum rate of p-aminophenol formation (11.7 ± 0.1) indicate participation of the hydroperoxide anion as the active oxygen species in the rate-determining step of the insertion reaction. Powerful scavengers of the hydroxyl radical (OH′) have little effect on the formation of H₂O₂ or p-aminophenol by the system. Superoxide dismutase (10^?7 mol dm^?3) inhibited both p-aminophenol and H₂O₂ formation, when added to the system immediately prior to initiation of the reaction. Studies involving N-phenylhydroxylamine indicate that aromatic ring hydroxylation is occurring directly and not by rearrangement of an N-hydroxylated intermediate. Implications of hemin-mediated hydroxylation reactions for those of enzymatic mixed function oxidase activity are discussed.     

Role of Bacteria in the Oxidation of Myoglobin

The addition to steaks of cell suspensions of a number of aerobic bacteria and of Saccharomyces cerevisiae greatly increased the rate of discoloration. Low inocula resulted in the more rapid appearance of the brown color of metmyoglobin, whereas high cell populations quickly produced the purple color of myoglobin. Sonically treated suspensions of Pseudomonas geniculata produced similar changes in surface color but less rapidly. No such effect was observed with Lactobacillus plantarum.

The visible changes in color were found to be associated with the oxygen demand of the surface tissue including, of course, the demand of any contaminating microorganisms. Inhibitors of respiratory activity inhibited the rate of discoloration under normal atmospheric conditions. However, when the oxygen level in the atmosphere was reduced, the inhibitors had no significant effect. In an oxygen-free atmosphere, the steak surfaces were the purple color of myoglobin; at 10 mm oxygen pressure, the pigment was oxidized to metmyoglobin and the surface was brown in color. No bacterial activity was necessary for pigment oxidation under low oxygen pressures.

Addition of dilute solutions of glucose oxidase resulted in rapid oxidation of the meat pigment to metmyoglobin both in extracts and on steak surfaces. More concentrated solutions resulted in further oxidation as evidenced by the appearance of a green color. Horseradish extract with a high peroxidase activity added with H₂O₂ resulted in rapid oxidation of the pigment but neither were very effective alone, although H₂O₂ did result in a browning reaction in aged steaks.

It is concluded that the primary role of the bacteria in meat discoloration is in the reduction of the oxygen tension in the surface tissue. The implications of the data are discussed and a possible mechanism of myoglobin oxidation is proposed.

     

Thermoregulatory responses to thermal stimulation of the preoptic anterior hypothalamus in the red fox (Vulpes vulpes)

The preoptic anterior hypothalamus (POAH) thermoregulatory controller can be characterized by two types of control, an adjustable setpoint temperature and changing POAH thermal sensitivity. Setpoint temperatures for shivering (T_shiver) and panting (T_pant) both increased with decreasing ambient temperature (T_a), and decreased with increasing T_a. The POAH controller is twice as sensitive to heating as to cooling. Metabolic rate (MR) increased during both heating and cooling of the POAH. Resting temperature of the POAH was lower than internal body temperature (T_b) at all temperatures. This indicates the presence of some form of brain cooling mechanism. Decreased T_b during POAH heating was a result of increased heat dissipation, while higher T_b during POAH cooling was a result of increased heat production and reduced heat dissipation. The surface temperature responses indicated that foxes can actively control heat flow from body surface. Such control can be achieved by increased peripheral blood flow and vasodilation during POAH heating, and reduced peripheral blood flow and vasoconstriction during POAH cooling. The observed surface temperature changes indicated that the thermoregulatory vasomotor responses can occur within l min following POAH heating or cooling. Such a degree of regulation can be achieved only by central neural control. Only surface regions covered with relatively short fur are used for heat dissipation. These thermoregulatory effective surface areas account for approximately 33% of the total body surface area, and include the area of the face, dorsal head, nose, pinna, lower legs, and paws.     

Alkali and oxygen-alkali treatment of D-arabino-hexosulose and O-β-D-glucopyranosyl-(1 → 4)-d-arabino-hexosulose.

Benzilic acid rearrangement of D-arabino-hexosulose (1) and O-β-D-glucopyranosyl-(1→4)-D-arabino-hexosulose (2) favours formation of mannonic acid and mannonic acid moieties, respectively. The results show that formation of aldonic acid end-groups via terminal aldosulose moieties is of little importance during oxygen-hydrogencarbonate treatment of (1→4)-linked polysaccharides. The major reaction of 1 in the absence of oxygen involves loss of C-1 as formic acid. The enediol intermediate gives rise to pentoses and pentuloses (degraded completely at high alkalinity), and 3-deoxypentonic acids. The yield of 3-deoxypentonic acids is decreased in the presence of oxygen, whereas that of arabinonic, erythronic, and glycolic acids is increased. The main reaction of 2 giving rise to aliphatic hydroxy acids is β-elimination of the glucose moiety, yielding a tricarbonyl intermediate (3) which, in sodium hydrogencarbonate, is decomposed mainly to 3,4-dihydroxybutanoic and glycolic acids. In sodium hydroxide, 3-deoxypentonic acids are among the major reaction products. In addition, a complex mixture of u.v.-absorbing solutes is formed, some of which are held irreversibly by anion exchangers.     

Effect of Dinitrophenol on the Heats of Respiration of Germinating Seeds of Prosopis juliflora, Kochia scoparia, and Oxyria digyna

During a 36-hour period, the rate of absorption of oxygen, respiration quotient, and rate of evolution of heat have been measured using seeds of Prosopis juliflora, Kochia scoparia, and Oxyria digyna. The results obtained in pure water were compared with those obtained in dilute solutions of dinitrolphenol. The data appear to be reproducible to ± 10% at the end of the 36-hour period and are independent of the amount of seeds used, provided it was 0.05 g or less. For a given amount of oxygen absorbed, more heat was liberated when the seeds were in a dinitrophenol solution. The results permit an estimate to be made of the heat energy stored in oxidative phosphorylation.     

Effect of harvesting period on the nutritive value of rice grass (Echinochloa sp.) hay given as sole diet to lambs

Data regarding the influence of maturity within the vegetative stage of tropical grasses on forage quality are limited and conflicting. The change in chemical composition of rice grass (Echinochloa sp.) hay harvested at 32, 46, 72 and 90 days of regrowth, and its effect on intake, digestibility, ruminal fermentation, rumen microbial protein synthesis (Experiment 1) and splanchnic oxygen uptake (Experiment 2) by lambs was evaluated. Except intake of indigestible neutral detergent fibre (NDF) which was similar for all treatments, intake of all hay components and the apparent digestibility of dry matter, organic matter (OM), NDF, N, as well as OM and N true digestibility, N retention and rumen microbial protein synthesis decreased linearly (P < 0.05) with increased regrowth age. Rumen fluid pH, ammonia N and peptide concentrations were similar for all treatments while sugars and amino acid concentrations decreased linearly with increased regrowth age of rice grass (P < 0.05). Passage rate of particles through reticulum-rumen (PRrr) was quadratically related (P < 0.05) to regrowth age. The highest PRrr and, consequently, the lowest retention time in the reticulum-rumen were obtained at 72 days of regrowth. There was a quadratic effect (P < 0.05) on net portal-drained viscera (PDV) flux of oxygen and heat production, while OM intake, portal blood flow and heat production as proportion of digestible energy (DE) intake were not affected by the increased regrowth age of rice grass. The highest means of oxygen uptake and heat production by PDV tissues were in 72 days treatment. In the whole splanchnic metabolism assay neither hay intake nor blood flow, oxygen uptake or heat production were affected by forage regrowth age. In conclusion, the nutritive value of rice grass hay decreased as regrowth age increased from 32 to 90 days due to decrease both OM intake and digestibility.     

Bioenergetics for the growth of Staphylococcus lentus in biocompatible choline salts

Choline-based biocompatible salts were used as “nutrients” for the growth of Staphylococcus lentus bacteria. Increase in the growth rate of bacteria was observed, compared to conventional carbon sources. In the case of the ionic liquid, choline lactate, the increase was pronounced. Bacterial growth was correlated with power–time curve in an investigation monitored online by reaction calorimetry. From the power–time curve, three phases of the growth can be distinctly seen. Heat yield coefficients estimated for the growth of S. lentus were found to match well with those reported hitherto. A comparative study of heat yields (catabolic) between glucose and choline lactate revealed significant information; the heat yield due to choline lactate (Y _Q/S) consumption and oxygen (Y _Q/O) were 23.4 kJ/g and 435 kJ/mol and whereas that for glucose with oxygen were 9.6 kJ/g and 427 kJ/mol, respectively, showing clearly the preferential affinity of choline lactate by the bacteria rather than glucose. This study also established that the use of ionic liquids as nutrients can be monitored using bioreaction calorimetry.