Accumulation of Silicon in the Monocotyledons Deschampsia caespitosa, Festuca lemanil and Schoenus nigricans

Abstract: Conventional and analytical electron microscopy (EDX, ESI, EELS) were used to investigate the silicon accumulation, the chemical nature of the Si deposits and their formation in three species of monocotyledons. In Deschampsia , in particular parts of the outer epidermal cell wall silicon is accumulated as silicic acid. Electron dense, needle-shaped crystals in the vacuoles of epidermal cells and in the intercellular spaces were also identified as silicic acid. In xylem parenchyma cells, silicon is accumulated as SiO₂, which is formed from Sn silicate. In Festuca , crystal-like deposits of SiO₂ occur on the epidermal surface, in the epidermal and parenchyma cell walls, and in vacuoles of bundle sheath cells. Often the deposits disturb the cell walls and penetrate the envelope of plastids and mitochondria. The crystal-like SiO₂ deposits originate from Sn silicate. In the pericarp of ripe nuts of Schoenus , no stainable cell wall components are detected. The inner part of the pericarp consists of silicic acid, while in the outer regions small clusters of silicic acid are embedded in a matrix of SiO₂. The silicic acid deposits show an unusual, layered structure, typical for lepidoic silicic acids, which consist of two-dimensional crystals lying one above the other.     

First report of Phytopythium vexans causing the “Avocado sadness” in Michoacan,Mexico

Mexico is the main producer, consumer and exporter of avocado in the world, being Michoacan the main producer state contributing more than 80% of the national production. There are phytopathogens that decimate the production causing the death of the tree. Root samples were collected in avocado trees that showed the characteristic symptomatology of the disease known as avocado sadness, the sampling was carried out in four of the main avocado producing towns, in the state of Michoacan, Mexico. The isolation consisted in sowing root tissue in Petri dishes with V8^®-PARPH culture medium, subsequently they were identified morphologically and for species level it was determined by molecular biology, with the PCR-ITS technique. Pathogenicity tests were performed in triplicate with avocado seedlings with more than six leaves. After 24 hours, the inoculated plants expressed decay in the apical part, after 120 hours the leaves showed yellowing and after 15 days there was a generalized wilt on the stem and leaves, re-isolating the phytopathogen Phytopythium vexans. This study confirms the first report of the oomycete P. vexans affecting avocado trees in the most important producing region of the Mexican Republic.     

Phylogenetic analysis of the alpha-globin pseudogene-4 (Hba-ps4) locus in the house mouse species complex reveals a stepwise evolution of t haplotypes [published erratum appears in Mol Biol Evol 1994 Jan;11(1):158]

A parsimony analysis was performed on restriction sites at the Hba-ps4 pseudogene locus within one of four inversions associated with mouse t haplotypes. The results suggest that all t haplotypes form a monophyletic group and that the in (17)4 inversion originated before the radiation of the Mus musculus species complex but after the divergence of the lineages leading to M. spretus, M. abbotti, and M. hortulanus. A time frame based on the evolutionary rate of mouse pseudogenes places the origin of this t haplotype inversion at 1.5 Mya, or approximately 1.5 Myr after the origin of the more proximal t complex inversion, in (17)2. The accumulated evidence indicates that complete t haplotypes have been assembled in a stepwise manner, with each of these inversions occurring on separate chromosomal lineages and at different evolutionary times. In addition, the evolutionary relationships of pseudogene sequences resulting from genetic exchange between wild-type and t haplotype alleles were examined. Analysis of sequences from the 5' and 3' sides of a putative site of recombination resulted in cladograms with different topologies. The implications for hypotheses concerning the evolutionary forces acting on t haplotypes and their rapid propagation throughout worldwide populations of mice are discussed.      

Fermentation characterization and flux analysis of recombinant strains of Clostridium acetobutylicum with an inactivated solR gene

The effect of solR inactivation on the metabolism of Clostridium acetobutylicum was examined using fermentation characterization and metabolic flux analysis. The solR-inactivated strain (SolRH) of this study had a higher rate of glucose utilization and produced higher solvent concentrations (by 25%, 14%, and 81%, respectively, for butanol, acetone, and ethanol) compared to the wild type. Strain SolRH(pTAAD), carrying a plasmid-encoded copy of the bifunctional alcohol/aldehyde dehydrogenase gene (aad) used in butanol production, produced even higher concentrations of solvents (by 21%, 45%, and 62%, respectively, for butanol, acetone, and ethanol) than strain SolRH. Clarithromycin used for strain SolRH maintenance during SolRH(pTAAD) fermentations did not alter product formation; however, tetracycline used for pTAAD maintenance resulted in 90% lower solvent production. Journal of Industrial Microbiology & Biotechnology (2001) 27, 322–328. Received 12 September 2000/ Accepted in revised form 21 July 2001     

Metal-sulfur dπ-pπ buffering of the oxidations of metal-thiolate complexes: Photoelectron spectroscopy of (η-C5H5)Fe(CO)2SR (SR = SCH3, SBu) and (η-C5H5)Re(NO)(PR3)SCH3 (PR3 = PPr3, PPh3)

The metal-sulfur bonding present in the transition metal-thiolate complexes CpFe(CO)₂SCH₃, CpFe(CO)₂S^tBu, CpRe(NO)(PⁱPr₃)SCH₃, and CpRe(NO)(PPh₃)SCH₃ (Cp = η⁵-C₅H₅) is investigated via gas-phase valence photoelectron spectroscopy. For all four complexes a strong dπ-pπ interaction exists between a filled predominantly metal d orbital of the [CpML₂]⁺ fragment and the purely sulfur 3pπ lone pair of the thiolate. This interaction results in the highest occupied molecular orbital having substantial M-S π^∗ antibonding character. In the case of CpFe(CO)₂SCH₃, the first (lowest energy) ionization is from the Fe-S π^∗ orbital, the next two ionizations are from predominantly metal d orbitals, and the fourth ionization is from the Fe-S π orbital. The pure sulfur pπ lone pair of the thiolate fragment is less stable than the filled metal d orbitals of the [CpFe(CO)₂]⁺ fragment, resulting in a Fe-S π^∗ combination that is higher in sulfur character than the Fe-S π combination. Interestingly, substitution of a tert-butyl group for the methyl group on the thiolate causes little shift in the first ionization, in contrast to the shift observed for related thiols. This is a consequence of the delocalization and electronic buffering provided by the Fe-S dπ-pπ interaction. For CpRe(NO)(PⁱPr₃)SCH₃ and CpRe(NO)(PPh₃)SCH₃, the strong acceptor ability of the nitrosyl ligand rotates the metal orbitals for optimum backbonding to the nitrosyl, and the thiolate rotates along with these orbitals to a different preferred orientation from that of the Fe complexes. The initial ionization is again the M-S π^∗ combination with mostly sulfur character, but now has considerable mixing among several of the valence orbitals. Because of the high sulfur character in the HOMO, ligand substitution on the metal also has a small effect on the ionization energy in comparison to the shifts observed for similar substitutions in other molecules. These experiments show that, contrary to the traditional interpretation of oxidation of metal complexes, removal of an electron from these metal-thiolate complexes is not well represented by an increase in the formal oxidation state of the metal, nor by simple oxidation of the sulfur, but instead is a variable mix of metal and sulfur content in the highest occupied orbital.     

Monthly day/night changes and seasonal daily rhythms of sexual steroids in Senegal sole (Solea senegalensis) under natural fluctuating or controlled environmental conditions

In this paper we attempted to investigate the existence of daily fluctuations on plasma sexual steroids (17beta-estradiol, E(2) and testosterone, T) in Senegal sole (Solea senegalensis) females. We described the monthly day/night concentrations and seasonal daily rhythms in animals reared under natural photo- and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 degrees C) for one year. Although no significant day/night differences were detected in monthly samplings, the existence of an annual rhythm of E(2) and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in March for both steroids (6.1+/-1.7 ng mL(-1) at mid-dark, MD and 4.0+/-0.6 ng mL(-1) at mid-light, ML for E2 and 1.4+/-0.4 ng mL(-1) at MD and 0.8+/-0.1 ng mL(-1) at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, the presence of daily oscillations was revealed. At the spring solstice (21st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E(2)) and at 21:08 h (T). In summer, autumn and winter no daily rhythms were observed due to the low steroid levels at those seasons. When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.     

Heat-shock proteins induce heavy-metal tolerance in higher plants

Cell cultures of Lycopersicon peruvianum L. stressed with CdSO₄ (10^–3M) show typical changes in the ultrastructure, starting with the plasmalemma and later on extending to the endoplasmic reticulum and the mitochondrial envelope. Part of the membrane material is extruded, with the formation of osmiophilic droplets which increase in size and number during the stress period. After 4 h, about 20 of the cells are dead. A short heat stress preceeding the heavy-metal stress induces a tolerance effect by preventing the membrane damage. The cells show a normal ultrastructure with one exception: cytoplasmic heat-shock granules are formed. This protective effect can be abolished by cycloheximide. Cadmium uptake is not markedly influenced by the heat stress. Cadmium is found together with sulfur in small deposits in the vacuoles of stressed cells. The precipitates contain an excess of sulfur, evidently due to the stress-induced formation of phytochelatins. The role in heavy-metal tolerance of heat-shock proteins in the plasmalemma (HSP70) and in cytoplasmic heat-stress granules (HSP17, HSP70) is discussed.Abbreviations EDX energy dispersive analysis of X-rays - ESI electron-spectroscopic imaging - HM heavy metal - HSG heat-stress granules - HSP heat-shock protein - MNDO modified neglect of diatomic overlap This work was supported by the Ministerium für Wissenschaft und Forschung des Landes Sachsen-Anhalt and the Deutsche Forschungsgemeinschaft.     

Ligand-mediated metal-metal interactions in (ν:ν-fulvalene) bis (dicarbonylcobalt) and rhodium complexes

Gas phase photoelectron spectroscopy (PES) is used to investigate the bonding and electronic structure in (fv) [M(CO)₂]₂ (fv = fulvalene, η⁵:η⁵-C₁₀H₈²⁻; M = Co, Rh). The results for these bimetallic complexes are also compared to those for the analogous monometallic complexes CpM(CO)₂ (Cp = η⁵−C₅H₅⁻; M = Co, Rh) which have been reported previously. The low valence ionization patterns observed for CpCo(CO)₂ and (fv)[Co(CO)₂]₂ are very similar, indicating that there is little electronic interaction between the two metals of the dicobalt complex. The spectrum of (fv)[Rh(CO)₂]₂ also is very similar to the spectrum of CpRh(CO)₂, except that the first metal ionizations in the bimetallic rhodium compound show a significant splitting (0.45 eV). This splitting is due to electronic interaction between the two metal centers which occurs via communication through the fulvalene π system. The differences in electronic structure are compared to the differences in electrochemical behavior of the Co and Rh fulvalene complexes.     

Insight into NSAID-induced membrane alterations, pathogenesis and therapeutics: characterization of interaction of NSAIDs with phosphatidylcholine

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most widely consumed pharmaceuticals, yet both the mechanisms involved in their therapeutic actions and side-effects, notably gastrointestinal (GI) ulceration/bleeding, have not been clearly defined. In this study, we have used a number of biochemical, structural, computational and biological systems including; Fourier Transform InfraRed (FTIR). Nuclear Magnetic Resonance (NMR) and Surface Plasmon Resonance (SPR) spectroscopy, and cell culture using a specific fluorescent membrane probe, to demonstrate that NSAIDs have a strong affinity to form ionic and hydrophobic associations with zwitterionic phospholipids, and specifically phosphatidylcholine (PC), that are reversible and non-covalent in nature. We propose that the pH-dependent partition of these potent anti-inflammatory drugs into the phospholipid bilayer, and possibly extracellular mono/multilayers present on the luminal interface of the mucus gel layer, may result in profound changes in the hydrophobicity, fluidity, permeability, biomechanical properties and stability of these membranes and barriers. These changes may not only provide an explanation of how NSAIDs induce surface injury to the GI mucosa as a component in the pathogenic mechanism leading to peptic ulceration and bleeding, but potentially an explanation for a number of (COX-independent) biological actions of this family of pharmaceuticals. This insight also has proven useful in the design and development of a novel class of PC-associated NSAIDs that have reduced GI toxicity while maintaining their essential therapeutic efficacy to inhibit pain and inflammation.