Effect of deuterium oxide on the thermodynamic quantities associated with phase transitions of phosphatidylcholine bilayer membranes

The bilayer phase transitions of three kinds of phospholipids, dipalmitoylphosphatidylcholine (DPPC), distearoylphosphatidylcholine (DSPC) and dihexadecylphosphatidylcholine (DHPC), in deuterium oxide (D₂O) and hydrogen oxide (H₂O) were observed by differential scanning calorimetry (DSC) under ambient pressure and light-transmittance measurements under high pressure. The DSC measurements showed that the substitution of H₂O by D₂O affected the pretransition temperatures and the main-transition enthalpies of all PC bilayers. The temperature-pressure phase diagrams for these PC bilayer membranes in both solvents were constructed by use of the data of light-transmittance measurements. Regarding the main transition of all PC bilayer membranes, there was no appreciable difference between the transition temperatures in D₂O and H₂O under high pressure. On the other hand, the phase transitions among the gel phases including the pretransition were significantly affected by the solvent substitution. The thermodynamic quantities of phase transitions for the PC bilayer membranes were evaluated and the differences in thermodynamic properties by the water substitution were considered from the difference of interfacial-free energy per molecule in the bilayer in both solvents. It was proved that the substitution of H₂O by D₂O causes shrinkage of the molecular area of phospholipid at bilayer interface due to the difference in bond strength between deuterium and hydrogen bonds and produces the great influence on the bilayer phase with the smaller area. Further, the induction of bilayer interdigitation in D₂O turned out to need higher pressures than in H₂O.     

Brain kinin B1 receptor is upregulated by the oxidative stress and its activation leads to stereotypic nociceptive behavior in insulin-resistant rats

Kinin B1 receptor (B1R) is virtually absent under physiological condition, yet it is highly expressed in models of diabetes mellitus. This study aims at determining: (1) whether B1R is induced in the brain of insulin-resistant rat through the oxidative stress; (2) the consequence of B1R activation on stereotypic nocifensive behavior; (3) the role of downstream putative mediators in B1R-induced behavioral activity. Sprague-Dawley rats were fed with 10% d-glucose in their drinking water or tap water (controls) for 4 or 12 weeks, combined either with a standard chow diet or a diet enriched with α-lipoic acid (1 g/kg feed) for 4 weeks. The distribution and density of brain B1R binding sites were assessed by autoradiography. Behavioral activity evoked by i.c.v. injection of the B1R agonist Sar-[D-Phe⁸]-des-Arg⁹-BK (10 μg) was measured before and after i.c.v. treatments with selective antagonists (10 μg) for kinin B1 (R-715, SSR240612), tachykinin NK1 (RP-67580) and glutamate NMDA (DL-AP5) receptors or with the inhibitor of NOS (L-NNA). Results showed significant increases of B1R binding sites in various brain areas of glucose-fed rats that could be prevented by the diet containing α-lipoic acid. The B1R agonist elicited head scratching, grooming, sniffing, rearing, digging, licking, face washing, wet dog shake, teeth chattering and biting in glucose-fed rats, which were absent after treatment with α-lipoic acid or antagonists/inhibitors. Data suggest that kinin B1R is upregulated by the oxidative stress in the brain of insulin-resistant rats and its activation causes stereotypic nocifensive behavior through the release of substance P, glutamate and NO.     

Flux of reduced chemical constituents (Fe2+, Mn2+, NH inf4 sup+ and CH4) and sediment oxygen demand in Lake Erie

Sediment pore water concentrations of Fe²⁺, Mn²⁺, NH _inf4 ^sup+ and CH₄ were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4 mM m⁻² day⁻¹ (0.3 g m⁻² day⁻¹). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe²⁺ and CH₄. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe²⁺ and Mn²⁺ to as high as 26% for NH _inf4 ^sup+ , and 30% for CH₄. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this station.     

Studies on Leaf Surface Lipid of Tobacco I. Changes in Leaf Surface Lipid and Duvatrienediol during Growth,Senescence and Curing of Tobacco Leaves

Duvatrienediol is a diterpene specifically occurred in tobacco plants and thought to be a precursor of tobacco aroma. Green tobacco leaves contained 0.2~1% of duvatrienediol per dry weight and it was corresponded to 30~60% of leaf surface lipid. Leaves on upper stalk position contained more of leaf surface lipid and duvatrienediol. In leaves on each stalk position, leaf surface lipid and duvatrienediol contents increased with leaf growth and decreased by over-maturation. Production of leaf surface lipid and duvatrienediol was affected by soil conditions or applied amount of nitrogen fertilizer. Both leaf surface lipid and duvatrienediol were decreased during curing of tobacco leaves, but the change in the latter was more drastic. Comparing to leaf surface lipid, changes in cytoplasmic lipid were less during growth and senescence of tobacco leaves.     

Compromised proteasome degradation elevates neuronal nitric oxide synthase levels and induces apoptotic cell death

The significance of impairment of proteasome activity in PC12 cells was examined in connection with nitrative/nitrosative stress and apoptotic cell death. Treatment of differentiated PC12 cells with MG132, a proteasome inhibitor, elicited a dose- and time-dependent increase in neuronal nitric oxide synthase (nNOS) protein levels, decreased cell viability, and increased cytotoxicity. Viability and cytotoxicity were ameliorated by L-NAME (a broad NOS inhibitor). Nitric oxide/peroxynitrite formation was increased upon treatment of PC12 cells with MG132 and decreased upon treatment with the combination of MG132 and 7-NI (a specific inhibitor of nNOS). The decreases in cell viability appeared to be effected by an activation of JNK and its effect on mitochondrial Bcl-x_L phosphorylation. These effects are strengthened by the activation of caspase-9 along with increased caspase-3 activity upon treatment of PC12 cells with MG132. These results suggest that impairment of proteasome activity and consequent increases in nNOS levels lead to a nitrative stress that involves the coordinated response of JNK cytosolic signaling and mitochondrion-driven apoptotic pathways.     

Morphological changes induced in erythrocyte by amyloid beta peptide and glucose depletion: A combined atomic force microscopy and biochemical study

Circulating red blood cells (RBCs) undergo aging, a fundamental physiological phenomenon that regulates their turnover. We show that treatment with beta amyloid peptide 1–42 (Aβ) accelerates the occurrence of morphological and biochemical aging markers in human RBCs and influences the cell metabolism leading to intracellular ATP depletion. The morphological pattern has been monitored using Atomic Force Microscopy (AFM) imaging and measuring the RBCs' plasma membrane roughness employed as a morphological parameter capable to provide information on the structure and integrity of the membrane-skeleton. Results evidence that Aβ boosts the development of crenatures and proto-spicules simultaneously to acceleration in the weakening of the cell-cytoskeleton contacts and to the induction of peculiar nanoscale features on the cell membrane. Incubation in the presence of glucose can remove all but the latter Aβ-induced effects.Biochemical data demonstrate that contemporaneously to morphological and structural alterations, Aβ and glucose depletion trigger a complex signaling pathway involving caspase 3, protein kinase C (PKC) and nitric oxide derived metabolites.As a whole, the collected data revealed that, the damaging path induced by Aβ in RBC provide a sequence of morphological and functional intermediates following one another along RBC life span, including: (i) an acceleration in the development of shape alteration typically observed along the RBC's aging; (ii) the development of characteristic membrane features on the plasma membrane and (iii) triggering a complex signaling pathway involving caspase 3, PKC and nitric oxide derived metabolites.     

The effect of manganese oxides and manganese ion on growth and siderophore production by Azotobacter vinelandii

The addition of manganese oxides to iron-limited medium promoted the formation of the pyoverdin siderophore azotobactin by Azotobacter vinelandii. When active-MnO₂ was used, there was greatly decreased iron uptake into the cells, hyperproduction of azotobactin and the abiotic, chemical destruction or adsorbtion of the catechol siderophores azotochelin and aminochelin by this strong oxidizing agent. Although the iron content of the cells was the same as iron-limited cells, the growth of cells in medium with active-MnO₂ was increased 1.5- to 2.5-fold over iron-limited controls. This growth promotion was not caused by iron contaminating the oxide or by manganese solubilized from the oxide. Soluble 0.05–4 mm Mn²⁺ inhibited the growth of iron-limited cells and had a minimal effect on iron uptake, but caused hyperproduction of azotobactin. This later effect was caused by the inhibition of soluble ferric reductase, in a manner identical to that previously observed for Zn²⁺. These results suggest that active-MnO₂ may interfere with a surface-localized iron uptake site, possibly another ferric reductase. The reason for the growth promotion by active-MnO₂ remains unknown, but is most likely related to decreased oxygen toxicity.     

High Performance Flexible Supercapacitor Electrodes Composed of Ultralarge Graphene Sheets and Vanadium Dioxide

Little is known regarding the effect of the graphene lateral size on the electrochemical performance of hybrid graphene electrode. This work examines the electrochemical performance of a flexible hybrid supercapacitor electrode composed of ultralarge graphene oxide (UGO; mean lateral size of 47 ± 22 μm) and vanadium dioxide (VO₂) nanobelts, referring to a reference electrode composed of small scale graphene oxide (SGO; mean lateral size of 0.8 ± 0.5 μm) and VO₂.Thermal treatment converts UGO/VO₂ and SGO/VO₂ to URGO/VO₂ (denoted VURGO) and SRGO/VO₂ (denoted VSRGO) electrodes, respectively. The sheet resistance of the VURGO film (0.57 ± 0.03 kΩ sq.^–1) was two orders of magnitude lower than that of the VSRGO (55.74 ± 9.35 kΩ sq.^–1). The VURGO hybrid electrode showed a specific capacitance of 769 F g^?1, which was significantly better than the corresponding values for the VSRGO electrode (385 F/g). These results support the notion that the use of ultralarge graphene sheets (≈22 500 μm²) lowers the intersheet resistance due to the presence of fewer intersheet tunneling barriers. This article highlights the potential utility of URGO (as a conductive support) in hybrid electrode containing VO₂ nanobelts for high performance flexible hybrid supercapacitor.     

Production of endothelial nitric oxide synthase (eNOS) over-expressing piglets

Vascular function, vascular structure, and homeostasis are thought to be regulated in part by nitric oxide (NO) released by endothelial cell nitric oxide synthase (eNOS), and NO released by eNOS plays an important role in modulating metabolism of skeletal and cardiac muscle in health and disease. The pig is an optimal model for human diseases because of the large number of important similarities between the genomic, metabolic and cardiovascular systems of pigs and humans. To gain a better understanding of cardiovascular regulation by eNOS we produced pigs carrying an endogenous eNOS gene driven by a Tie-2 promoter and tagged with a V5 His tag. Nuclear transfer was conducted to create these animals and the effects of two different oocyte activation treatments and two different culture systems were examined. Donor cells were electrically fused to the recipient oocytes. Electrical fusion/activation (1 mM calcium in mannitol: Treatment 1) and electrical fusion (0.1 mM calcium in mannitol)/chemical activation (200 μM Thimerosal for 10 min followed by 8 mM DTT for 30 min: Treatment 2) were used. Embryos were surgically transferred to the oviducts of gilts that exhibited estrus on the day of fusion or the day of transfer. Two cloned transgenic piglets were born from Treatment 1 and low oxygen, and another two from Treatment 2 and normal oxygen. PCR, RT-PCR, Western blotting and immunohistochemistry confirmed that the pigs were transgenic, made message, made the fusion protein and that the fusion protein localized to the endothelial cells of placental vasculature from the conceptuses as did the endogenous eNOS. Thus both activation conditions and culture systems are compatible with development to term. These pigs will serve as the founders for a colony of miniature pigs that will help to elucidate the function of eNOS in regulating muscle metabolism and the cardiorespiratory system.     

N‐nitrosomelatonin enhances photic synchronization of mammalian circadian rhythms

Most physiological processes in mammals are synchronized to the daily light:dark cycle by a circadian clock located in the hypothalamic suprachiasmatic nucleus. Signal transduction of light‐induced phase advances of the clock is mediated through a neuronal nitric oxide synthase‐guanilyl cyclase pathway. We have employed a novel nitric oxide‐donor, N‐nitrosomelatonin, to enhance the photic synchronization of circadian rhythms in hamsters. The intraperitoneal administration of this drug before a sub‐saturating light pulse at circadian time 18 generated a twofold increase of locomotor rhythm phase‐advances, having no effect over saturating light pulses. This potentiation was also obtained even when inhibiting suprachiasmatic nitric oxide synthase activity. However, N‐nitrosomelatonin had no effect on light‐induced phase delays at circadian time 14. The photic‐enhancing effects were correlated with an increased suprachiasmatic immunoreactivity of FBJ murine osteosarcoma viral oncogene and period1. Moreover, in vivo nitric oxide release by N‐nitrosomelatonin was verified by measuring nitrate and nitrite levels in suprachiasmatic nuclei homogenates. The compound also accelerated resynchronization to an abrupt 6‐h advance in the light:dark cycle (but not resynchronization to a 6‐h delay). Here, we demonstrate the chronobiotic properties of N‐nitrosomelatonin, emphasizing the importance of nitric oxide‐mediated transduction for circadian phase advances.