Imidazolate-bridged dicopper(II) and copper(II)–zinc(II) complexes of macrocyclic ligand with methylimidazol pendants: Model study of copper(II)–zinc(II) superoxide dismutase

Two new homo- and hetero-dinuclear complexes, [Cu₂L(im)](ClO₄)₃4H₂O (1) and [CuZnL(im)](ClO₄)₃4H₂O (2) (where Im=1H-1midazole and L = 3, 6, 9, 16, 19, 22-hexaaza-6, 19-bis(1H-imidazol-4-ylmethyl)tricycle[22, 2, 2, 2^11,14]triaconta-1, 11, 13, 24, 27, 29-hexaene) were synthesized and characterized as model compounds for the active site of copper(II)–zinc(II) superoxide dismutase (Cu₂Zn₂–SOD). X-ray crystal structure analysis revealed that the metal centers in both complexes exhibit distorted trigonal-bipyramid coordination geometry and the CuCu and CuZn distances are both 6.02 Å. Magnetic and ESR spectral measurements of 1 showed antiferromagnetic exchange interactions between the imidazolate-bridged Cu(II) ions. The ESR spectrum of 2 displays typical signals of mononuclear Cu(II) complex, demonstrating the formation of heterodinuclear complex 2 rather than a mixture of homodinuclear Cu(II)/Zn(II) complexes. pH-dependent ESR and UV–visible spectral measurements manifest that the imidazolate exists as a bridging ligand from pH 6 to 11 for both complexes. The IC₅₀ values of 1.96 and 1.57 μM [per Cu(II) ion] for 1 and 2 suggest that they are good models for the Cu₂Zn₂–SOD.     

Kinetics of ammonium, nitrate and phosphorus uptake by Canna indica and Schoenoplectus validus

Canna indica L. is an upright perennial rhizomatous herb, and Schoenoplectus validus (Vahl) A. Löve and D. Löve is a tall, perennial, herbaceous sedge. The nutrient uptake kinetics of C. indica and S. validus were investigated using the modified depletion method after plants were grown for 4 weeks in simulated secondary-treated wastewater. The maximum uptake rate (I_max) and Michaelis–Menten constant (K_m) were estimated by iterative curve fitting. The I_max for NH₄N (623 μmol g⁻¹ dry root weight h⁻¹) was significantly higher than that for NO₃N (338 μmol g⁻¹ dry root weight h⁻¹) in S. validus. In contrast, no difference was observed in C. indica. The I_max values for NO₃N and NH₄N were higher in S. validus than in C. indica. A significantly lower K_m was detected for NO₃N uptake in C. indica (385 μmol L⁻¹) compared to that in S. validus (1908 μmol L⁻¹). The I_max for PO₄P did not differ between the plant species. The K_m for PO₄P was significantly higher in C. indica (157 μmol L⁻¹) than in S. validus (60 μmol L⁻¹). In conclusion, we found that S. validus preferred NH₄N over NO₃N, had greater capacity for N uptake and higher affinity for PO₄P, but C. indica had greater affinity for NO₃N. Nutrient uptake capacity is likely related to habitat preference, and is influenced by the structure of roots and rhizomes.     

In vivo real-time measurement of superoxide anion radical with a novel electrochemical sensor

The dynamics of superoxide anion (O₂⁻) in vivo remain to be clarified because no appropriate method exists to directly and continuously monitor and evaluate O₂⁻ in vivo. Here, we establish an in vivo method using a novel electrochemical O₂⁻ sensor. O₂⁻ generated is measured as a current and evaluated as a quantified partial value of electricity (Q_part), which is calculated by integration of the difference between the baseline and the actual reacted current. The accuracy and efficacy of this method were confirmed by dose-dependent O₂⁻ generation in xanthine–xanthine oxidase in vitro in phosphate-buffered saline and human blood. It was then applied to endotoxemic rats in vivo. O₂⁻ current began to increase 1 h after lipopolysaccharide, and Q_part increased significantly for 6 h in endotoxemic rats, in comparison to sham-treated rats. These values were attenuated by superoxide dismutase. The generation and attenuation of O₂⁻ were indirectly confirmed by plasma lipid peroxidation with malondialdehyde, endothelial injury with soluble intercellular adhesion molecule-1, and microcirculatory dysfunction. This is a novel method for measuring O₂⁻ in vivo and could be used to monitor and treat the pathophysiology caused by excessive O₂⁻ generation in animals and humans.     

Production of superoxides and nitric oxide generation in haemocytes of mussel Mytilus galloprovincialis (Lmk.) after exposure to cadmium: A possible involvement of Na/H exchanger in the induction of cadmium toxic effects

The present study investigates cadmium (Cd) ability to enhance superoxides (O₂⁻) and nitric oxide (NO) production (as nitrites) in haemocytes of mussel Mytilus galloprovincialis as well as the possible involvement of Na⁺/H⁺ exchanger (NHE) in the induction of NADPH oxidase and NO synthase activity. PMA, a well-known PKC-mediated NADPH oxidase as well as NO synthase stimulator was also used, in order to verify Cd effects on both O₂⁻ and NO generation. According to the results of the present study, micromolar concentrations of Cd (0.05, 5, 10 and 50 μM) seemed to enhance O₂⁻ and NO generation in haemocytes of mussels. Moreover, O₂⁻ and NO generation in haemocytes exposed to Cd could be enhanced by its ability to induce reactive oxygen species (ROS) but respiratory burst activation as well. Inhibition of NO synthase with 10 μM l-NAME, significantly attenuated Cd ability to enhance O₂⁻ production and diminished NO generation, thus leading to the suggestion that Cd toxic effects, started at concentration of 50 μM, could enhance NADPH oxidase and NO synthase stimulation in haemocytes of mussels. NHE seems to play a regulatory role in the induction of either O₂⁻ or NO generation in haemocytes exposed to the metal, since its inhibition with the use of 10 μM EIPA significantly decrease both O₂⁻ and NO production. The involvement of NHE in the induction of O₂⁻ and NO generation, probably via PKC-mediated NADPH oxidase and NO synthase activation, is likely to be crucial to haemocytes exposed to heavy metals, such as Cd.     

CHMetal(II) axial interaction in planar complexes (metal = Cu, Pd) and implications for possible environmental effects of alkyl groups at biological copper sites

Intramolecular M(II)H–C interactions (M(II)=Cu(II), Pd(II)) involving a side chain alkyl group of planar d⁸ and d⁹ metal complexes of the N-alkyl (R) derivatives of N,N-bis(2-pyridylmethyl)amine with an N₃Cl donor set were established by structural and spectroscopic methods. The methyl group from the branched alkyl group (R = 2,2-dimethylpropyl and 2-methylbutyl) axially interacts with the metal ion with the MC and MH distances of 3.056(3)–3.352(9) and 2.317(1)–2.606(1) Å, respectively, and the M–H–C angles of 122.4–162.3°. The Cu(II) complexes showing the interaction have a higher redox potential as compared with those without it, and the ¹H NMR signals of the interacting methyl group in Pd(II) complexes shifted downfield relative to the ligand signals. Dependence of the downshift values on the dielectric constants of the solvents used indicated that the M(II)H–C interaction is mainly electrostatic in nature and may be regarded as a weak hydrogen bond. Implications for possible environmental effects of the leucine alkyl group at the type 1 Cu site of fungal laccase are also discussed.     

Nitrogen dioxide solubility and permeation in lipid membranes

Nitrogen dioxide (NO₂) is an important oxidant molecule in biology that is produced by several biological processes, and it is also an important air pollutant. It can oxidize proteins and lipids with important consequences on their biological functions. Despite its relevance, the interaction of NO₂ with the cell barrier, the lipid membrane, is poorly understood. For instance, can lipid membranes limit NO₂ diffusion? To estimate the permeability of lipid membranes to NO₂ it is necessary to learn more about its solubility in the lipid phase. However, experimental data on NO₂ solubility is very limited. To improve our knowledge on this matter, we used a mixed approach consisting in calculating the solubility of NO₂ and related diatomic and triatomic gases (NO, O₂, CO₂, etc.) in different solvents using quantum calculations and Tomasi’s Polarizable Continuum Model and validating and correcting these results using experimental data available for the related gases. This approach led to an estimated partition coefficient for NO₂ of 2.7 between n-octanol and water, and 1.5 between lipid membranes and water, meaning that NO₂ is a moderately hydrophobic molecule (less than NO, more than CO₂). Based on the solubility-diffusion permeability theory, the permeability coefficient was estimated to be 5 cm s⁻¹, up to 4000 times higher than that of peroxynitrous acid. It is concluded that lipid membranes are not significant barriers to NO₂ transport.     

Influence of environmental factors on reductive bioprecipitation of uranium by sulfate reducing bacteria

Microbial reduction of soluble uranyl [U (VI)] to insoluble uraninite by sulfate reducing bacteria (SRB) is a promising remediation strategy for uranium-contaminated groundwater. Effects of environmental factors, including pH and coexisting ions, on U (VI) bioreduction processes (UBP) remain unknown. Anaerobic batch experiments were performed to evaluate impact on UBP. Kinetic investigations with varied pH demonstrated that U (VI) was reduced mostly within 48 h. The bioprecipitation yields depended strongly on pH, increasing from 12.9% to 99.4% at pH 2.0 and 6.0, respectively. Sulfate concentration 4000 mg l⁻¹ did not affect UBP; however, sulfate concentration 5000 mg l⁻¹ significantly slowed UBP. Biogenic H₂S produced during sulfate reduction was not directly involved in UBP. At 20 mg l⁻¹ Zn or 10 mg l⁻¹ Cu, no UBP inhibition was observed and uraninite was detected in metal sulfide precipitate. However, 25 mg l⁻¹ Zn or 15 mg l⁻¹ Cu stopped UBP completely. Cu toxicity mechanism probably differed from Zn. The ability to reduce U (VI) was lost permanently with exposure to 15 mg l⁻¹ Cu, but not for Zn 25 mg l⁻¹. No uraninite could be detected before nitrate removal, suggesting nitrate strongly inhibited UBP, which may possibly be related to denitrification intermediates controlling the solution redox potential.     

Half-sandwich Ru[9]aneS3 complexes structurally similar to antitumor-active organometallic piano-stool compounds: Preparation, structural characterization and in vitro cytotoxic activity

The preparation, structural characterization, and chemical behavior in aqueous solution of a series of new Ru[9]aneS₃ half-sandwich complexes of the type [Ru([9]aneS₃)Cl(NN)][CF₃SO₃] and [Ru([9]aneS₃)(dmso-S)(NN)][CF₃SO₃]₂ (5–15, NN = substituted bpy or 2 × 1-methylimidazole) are described. The X-ray structures of [Ru([9]aneS₃)Cl(3,3′-H₂dcbpy)][CF₃SO₃] (9) (3,3′-H₂dcbpy = 3,3′-dicarboxy-2,2′-bipyridine), [Ru([9]aneS₃)Cl(4,4′-dmobpy)][CF₃SO₃] (13) (4,4′-dmobpy = 4,4′-dimethoxy-2,2′-bipyridine), and [Ru([9]aneS₃)Cl(1-MeIm)₂][CF₃SO₃] (15) (1-MeIm = 1-methylimidazole) were also determined. The new compounds are structurally similar to anticancer-active organometallic half-sandwich complexes of formula [Ru(η⁶-arene)Cl(NN)][PF₆]. Three chloro compounds (5, 9, 15) were tested in vitro for cytotoxic activity against two human cancer cell lines in comparison with the previously described [Ru([9]aneS₃)Cl(en)][CF₃SO₃] (1, en = ethylenediamine), [Ru([9]aneS₃)Cl(bpy)][CF₃SO₃] (2), and with their common dmso precursor [Ru([9]aneS₃)Cl(dmso-S)₂][CF₃SO₃] (3). Only the ethylenediamine complex 1 showed some antiproliferative activity, ca. one order of magnitude lower than the reference organometallic half-sandwich compound RM175 that contains biphenyl instead of [9]aneS₃. This compound was further tested against a panel of human cancer cell lines (including one resistant to cisplatin).     

Synthesis and characterization of a crosslinked chitosan derivative with a complexing agent and its adsorption studies toward metal(II) ions

A new chitosan derivative has been synthesized by crosslinking a metal complexing agent, [6,6′-piperazine-1,4-diyldimethylenebis (4-methyl-2-formyl) phenol] (L), with chitosan (CTS). The resulting material (CCTSL) was characterized by elemental (CHN), spectral (FTIR and solid-state NMR), thermal (TGA and DTA), and structural (powder XRD and SEM) analyses. Adsorption experiments (pH dependency, kinetics, and equilibrium) of CCTSL toward various metal ions such as Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II) were carried out at 25 °C. The results showed that the adsorption was dependent on the pH of the solution, with a maximum capacity between pHs 6.5 and 8.5. The kinetics was evaluated by applying the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The maximum adsorption capacity was 1.21 mmol g⁻¹ for Cu(II) and the order of adsorption capacities for the metal(II) ions studied was found to be Cu(II) > Ni(II) > Cd(II)  Co(II)  Mn(II)  Fe(II)  Pb(II).     

Western equatorial Pacific planktic foraminiferal fluxes and assemblages during a La Niña year (1999)

A correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies. We studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time-series sediment trap deployments in the western equatorial Pacific under La Niña conditions from January to November 1999. Eleven species contributed about 90% of the total flux in all traps. Two sites (MT1, MT3) in the Western Pacific Warm Pool region (WPWP) were characterized by common occurrences of the species Globigerinoides ruber, Globigerinoides sacculifer, Globigerinoides tenellus, and Neogloboquadrina dutertrei. Site MT5 farther to the east in the equatorial upwelling region had common occurrences of Globigerina bulloides, Globigerinita glutinata, and Pulleniatina obliquiloculata. Very high abundances of G. bulloides and G. glutinata at MT5 indicate that equatorial upwelling (EU) occurred during the 1999 La Niña. The two western sites have similar assemblage compositions, but MT1 ( 135°E) has the highest fluxes (up to  3800 tests m^− 2 day^− 1), whereas MT3 ( 145° E) has fluxes below  2200 tests m^− 2 day^− 1. Relatively high fluxes (up to  3000 tests m^− 2 day^− 1) occur at site MT5 ( 176° E), where upwelling occurred.The differences in faunal composition in the WPWP and EU might be attributable to differences in the way in which nutrients are supplied to the phytoplankton: large amounts of suspended material are supplied to the WPWP by advection of waters passing through the coastal region of an archipelago, whereas upwelling of nutrient-rich waters enhances primary production in the EU. At the westernmost site in the WPWP, a peak in the G. bulloides flux coincided with southward flow of the New Guinea Coastal Current (NGCC) in late February, but the highest G. ruber flux coincided with northward flow of this current in late May. Thus, the differences in species dominance at this location may be caused by monsoon-driven variability in the flow direction of the NGGC.     

Protein kinase C-α negatively regulates EGF-induced PLC- activity through direct phosphorylation

Phospholipase C- is a PLC isozyme that contains a CDC25 homology domain and a pair of RA domains in addition to a conserved PLC catalytic domain. PLC- is activated by both growth factors and GPCR ligands in a distinct manner. Growth factors such as EGF stimulate PLC- in an RA2 domain-dependent manner through Ras and Rap. On the other hand, several GPCR ligands that are linked with Ga₁₂ or Ga₁₃ can activate PLC- by associating with GTP-RhoA. GTP-RhoA binds with the region in the PLC- Y domain. Gs-linked ligands such as PGE1 and adrenaline stimulate PLC- by cAMP-dependent activation of Epac and Rap2B. PLC- is important for cardiac development and function. In addition, several lines of evidence indicate that PLC- promotes cell growth in an activity-dependent or -independent manner. In particular, PLC--dependent suppression of EGF receptor downregulation contributes to its growth promoting activity. Proper regulation of PLC- activity is essential for preventing tumor formation. Our previous report indicated that EGF-dependent ubiquitination of PLC- is required for the control of PLC--dependent cell growth. Recently, we found that PLC- is phosphorylated by growth factor stimulation, and this is another mechanism of the negative regulation. PLC- is phosphorylated by PKC-α upon stimulation with growth factors such as EGF and PDGF. The EGF-induced phosphorylation of PLC- was abolished by PKC inhibitors and by the expression of the dominant negative mutant of PKC-α. Furthermore, PKC-α was found to phosphorylate PLC- directly in vitro, suggesting that PLC- is a substrate of PKC-α in cells. In addition, PLC- was co-immunoprecipitated with PKC-α in an EGF-dependent manner. Immunocytochemical studies showed that PLC- co-localized with PKC-α in the plasma membrane after EGF stimulation. In addition, inhibition of PKC activity enhanced PLC--mediated PIP₂ hydrolysis, suggesting that PKC-α negatively regulates PLC- activity. Taken together, these results suggest for the first time that PLC- is regulated by PKC-α-dependent phosphorylation.     

Decreased S-nitrosation of peptide thiols in the membrane interior

It has been proposed that autoxidation of nitric oxide (NO) stimulates S-nitrosation of thiols located in the hydrophobic milieu. We tested whether thiols located in hydrophobic membranes undergo enhanced S-nitrosation in the presence of NO/O₂. The transmembrane cysteinyl peptides C₄ (AcNH-KKACALA(LA)₆KK-CONH₂) and C₈ (AcNH-KKALALACALA(LA)₃KK-CONH₂) were incorporated into dilauroylphosphatidylcholine bilayers; their location in the membrane was determined by EPR spin labeling. The peptides, C₈ and C₄, and glutathione (GSH; 300 μM) were treated with a NO donor, DEA-NONOate, and nitrosothiol formation was determined under various O₂ levels. Surprisingly, the more hydrophobic cysteinyl peptide, C₈, did not yield any S-nitrosated product compared to GSH in the aqueous phase or C₄ peptide in the liposomes in the presence of NO/O₂. These data suggest that thiols located deeply in the hydrophobic core of the membrane may be less likely to undergo S-nitrosation in the presence of NO/O₂.     

Synthesis of novel ketoconazole derivatives as inhibitors of the human Pregnane X Receptor (PXR; NR1I2; also termed SXR, PAR)

PXR, pregnane X receptor, in its activated state, is a validated target for controlling certain drug–drug interactions in humans. In this context, there is a paucity of inhibitors directed toward activated PXR. Using prior observations with ketoconazole as a PXR inhibitor, the target compound 3 was synthesized from (s)-glycidol with overall 56% yield. (+)-Glycidol was reacted with 4-bromophenol and potassium carbonate in DMF to yield the ring opened compound 6. This was then heated to reflux in benzene along with 2′, 4′-difluoroacetophenone and catalytic amount of para-toluene sulfonic acid to yield 8. The resultant acetal 8 was then functionalized using Palladium chemistry to yield the target compound 3. The activity of the compound was compared with ketoconazole and UCL2158H. However, in contrast with ketoconazole (IC₅₀  0.020 μM; 100% inhibition), 3 has negligible effects on inhibition of microsomal CYP450 (maximum 20% inhibition) at concentrations >40 μM. In vitro, micromolar concentration of ketoconazole is toxic to passaged human cell lines, while 3 does not exhibit cytotoxicity up to concentrations 100 μM (viability >85%). This is the first demonstration of a chemical analog of a PXR inhibitor that retains activity against activated PXR. Furthermore, in contrast with ketoconazole, 3 is less toxic in human cell lines and has negligible CYP450 activity.     

The alpha-galactosyl derivatives of ganglioside GD(1b) are essential for the organization of lipid rafts in RBL-2H3 mast cells

Gangliosides are complex glycosphingolipids that are important in many biological processes. The present study investigated the role of gangliosides in the organization of lipid rafts in RBL-2H3 mast cells and in the modulation of mast cell degranulation via FcRI. The role of gangliosides was examined using two ganglioside deficient cell lines (B6A4A2III-E5 and B6A4C1III-D1) as well as the parent cell line (RBL-2H3). All three cell lines examined express FcRI, Lyn, Syk and LAT. However, only in RBL-2H3 cells were FcRI, LAT and α-galactosyl derivatives of ganglioside GD_1b mobilized to lipid raft domains following FcRI stimulation. The inhibition of glycosphingolipid synthesis in RBL-2H3 cells also resulted in a decrease in the release of β-hexosaminidase activity after FcRI activation. The two mutant cell lines have a reduced release of β-hexosaminidase activity after FcRI stimulation, but not after exposure to calcium ionophore. These results indicate that the α-galactosyl derivatives of ganglioside GD_1b are important in the initial events of FcRI signaling upstream of Ca²⁺ influx. Since the initial signaling events occur in lipid rafts and in the mutant cell lines the rafts are disorganized, these results also suggest that these gangliosides contribute to the correct assembly of lipid rafts and are essential for mast cell activation via FcRI.     

Chromium(III) complexes with 2-(2′-pyridyl)imidazole: Synthesis, crystal structure and magnetic properties

The preparation, crystal structure and variable temperature-magnetic investigation of three 2-(2′-pyridyl)imidazole-containing chromium(III) complexes of formula PPh₄[Cr(pyim)(C₂O₄)₂]·H₂O (1), AsPh₄[Cr(pyim)(C₂O₄)₂]·H₂O (2) and [Cr₂(pyim)₂(C₂O₄)₂(OH₂)₂]·2pyim · 6H₂O (3) [pyim = 2-(2′-pyridyl)imidazole, , and ] are reported herein. The isomorphous compounds are made up of discrete [Cr(pyim)(C₂O₄)₂]⁻ anions, cations [X = P (1) and As (2)] and uncoordinated water molecules. The chromium environment in 1 and 2 is distorted octahedral with Cr-N and Cr-O bond distances varying in the ranges 2.040(3)-2.101(3) and 1.941(3)-1.959(3) Å, respectively. The angle subtended by the chromium(III) ion by the two didentate oxalate ligands cover the range 82.49(12)-82.95(12)°, values which are somewhat greater than those concerning the chelating pyim molecule [77.94(13) (1) and 78.50(13)° (2)]. Complex 3 contains discrete centrosymmetric [Cr₂(pyim)₂(C₂O₄)₂(OH)₂] neutral units where the two chromium(III) ions are joined by a di-μ-hydroxo bridge, the oxalate and pyim groups acting as peripheral didentate ligands. Uncoordinated water and pyim molecules are also present in 3 and they contribute to the stabilization of its structure by extensive hydrogen bonding and π-π type interactions. The values of the intramolecular chromium-chromium separation and angle at the hydroxo bridge in 3 are 2.9908(12) Å and 99.60(16)°, respectively. Magnetic susceptibility measurements of 1-3 in the temperature range 1.9-300 K show the occurrence of weak inter- (1 and 2) and intramolecular (3) antiferromagnetic couplings. The magnetic properties of 3 have been interpreted in terms of a temperature-dependent exchange integral, small changes of the angle at the hydroxo bridge upon cooling being most likely responsible for this peculiar magnetic behavior.     

Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography

An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 ( 7.0–5.9 Ma). The Gurabo Formation spans Zones N18 and N19 ( 5.9–4.5 Ma). The Mao Formation is placed in Zone N19 ( 4.5–3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific–Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation ( 6.1 Ma) and in the middle Mao Formation ( 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity ( 4.8 Ma) and periods of upwelling ( 6.1and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity, and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes.     

Catalase activity and rhythmic patterns in mouse brain, kidney and liver

To protect tissues from damaging effects of reactive oxygen species (ROS), organisms possess enzymatic and non-enzymatic antioxidant systems. Cytosolic-enzyme catalase (CAT) is a component of the antioxidant defence system that reduces hydrogen peroxide (H₂O₂) to water (H₂O). The aim of this study was to assess the variation of antioxidant enzyme CAT activity in brain, kidney and liver of adult male mice according to tissue-specific and temporal patterns within a 24-h period (12:12 L/D). The CAT activity was assayed at 4-h intervals. The Cosinor test programme was used to detect and confirm the best corresponding rhythm. In liver, the circadian rhythm of CAT was associated with ultradian components. The prominent circadian rhythm (with a period τ = 24 h) showed a peak located at the middle of the dark phase, more precisely  17 HALO (Hours After Light Onset). In kidney, only a circadian rhythm of CAT was validated with a peak time located at  17 HALO. However, in brain, the time pattern of CAT activity showed two peak times at  1 and  17 HALO, illustrating the existence of an ultradian rhythm (with a period τ = 12 h). The results showed significant organ differences with the highest activity in liver, compared with kidney (− 89%) and brain (− 98%). This might be related to several factors such as their respective physiological function, the risk of exposure to oxidative damage and the balance between synthesis and degradation of proteins during “normal metabolism”. Moreover, CAT activity revealed differences in time-related changes across a 24-h period that were more obvious in peak levels between the three tissues.     

Fine structure characterization of amylopectins from grain amaranth starch

The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with α-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then β-amylase to remove all external chains, whereby the internal structure was obtained. The ,β-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC–PAD). The results showed that the domain fraction contained 2.2 clusters, and single clusters were composed of 13 chains. The ,β-limit dextrins of the clusters were further hydrolyzed with α-amylase to characterize their building block composition. The average DP of the branched blocks was 11 and they contained on average 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of 6 branched blocks, and the internal chain length between the blocks was 6.8.     

Synthesis and coordination of the bifunctionalized ylides Ph2P(CH2)n(Ph)2PCHCOOMe (n = 1, 2) and ketenylidene Ph2P(CH2)2(Ph)2PCCO to Pd and Pt complexes

In this paper it is reported the synthesis of the phosphonium salts [Ph₂P(CH₂)_n(Ph)₂PCH₂COOMe]Br (n = 1 (1), 2 (2)) and [Ph₂P(CH₂COOMe)(CH₂)_n(Ph)₂PCH₂COOMe]Br₂ (n = 3 (3)) derived from the reactions of the diphosphines dppm, dppe and dppp with methyl bromoacetate. By reaction of the monophosphonium salt of dppm and dppe with the strong base Na[N(SiMe₃)₂] the corresponding carbonyl stabilized ylides Ph₂P(CH₂)_n(Ph)₂PCHCOOMe (n = 1 (4), 2 (5)) were obtained. The Ph₂P(CH₂)₂(Ph)₂PCHCOOMe (5) ylide was reacted with Pd(II) and Pt(II) substrates. From these reactions were isolated exclusively complexes in which the ylide was chelated to the metal through the free phosphine group and the ylidic carbon atom. A further reaction of the Ph₂P(CH₂)₂(Ph)₂PCHCOOMe (5) ylide with 1.5 equiv. of Na[N(SiMe₃)₂] gives the bifunctionalized ketenylidene Ph₂P(CH₂)₂(Ph)₂PCCO (6) system. This cumulenic ylide reacts with Pt(II) complexes to form a chelated derivative in which IR and NMR spectra suggest the breaking of the CC bond of the -CCO group.     

Hydrogen peroxide- and nitric oxide-induced systemic antioxidant prime-like activity under NaCl-stress and stress-free conditions in citrus plants

We tested whether pre-treatments of roots with H₂O₂ (10 mM for 8 h) or sodium nitroprusside (SNP; 100 μM for 48 h), a donor of NO, could induce prime antioxidant defense responses in the leaves of citrus plants grown in the absence or presence of 150 mM NaCl for 16 d. Both root pre-treatments increased leaf superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) activities, and induced related-isoform(s) expression under non-NaCl-stress conditions. When followed by salinity, certain enzymatic activities also exhibited an up-regulation in response to H₂O₂ or SNP pre-exposure. An NaCl-stress-provoked decrease in the ascorbate redox state was partially prevented by both pre-treatments, whereas the glutathione redox state under normal and NaCl-stress conditions was increased by SNP. Real-time imaging of NO production was found in vascular tissues and epidermal cells. Furthermore, NaCl-induced inhibition in OH scavenging activity and promotion of OH-mediated DNA strand cleavage was partially prevented by SNP. Moreover, NaCl-dependent protein oxidation (carbonylation) was totally reversed by both pre-treatments as revealed by quantitative assay and protein blotting analysis. These results provide strong evidence that H₂O₂ and NO elicit long-lasting systemic primer-like antioxidant activity in citrus plants under physiological and NaCl-stress conditions.