A hypothesis for thein vivo antioxidant action of salicyclic acid

This paper presents a new hypothesis for the physiological antioxidant action of salicylate. Current theories have focused on the radical scavenging nature of salicylate. This explanation may have limitations because it is unlikely that salicylate reaches the necessary concentrations to effectively prevent damage to cell components. We propose that salicylic acid decreases the flux of hydroxyl radicals through chelation, which causes a redox deactivation mechanism of iron Fenton reaction centers. This is due to voltammetric results which indicate that the iron-salicylate complex does not have the thermodynamic driving force to act as an effective Fenton reagent necessary for the production of damaging oxygen-containing radicals. Furthermore, despite the more facile thermodynamics associated with Fenton-type processes at acidic pH values, the complex maintains Fenton inactivity due to a pH-sensitive redox potential shift that follows asE _Fe[Sal] = 0.793 - (0.059 pH). This is important since inflammation sites are acidic relative to healthy tissue. This redox potential shift is unique to salicylates when compared with other common iron chelation agents such as EDTA. Further evidence for the lack of Fenton-type reactivity of the iron-salicylate complex is offered in the form of oxidation studies of calf thymus (CT) DNA by hydrogen peroxide. Salicylate prevents the iron-catalyzed oxidation of CT-DNA strands as indicated by the detection of the constituent bases by HPLC. However, salicylates were not able to prevent the copper-catalyzed oxidation of CT-DNA. These results are predicted by the cyclic voltammetry of copper-salicylate, which confirms that it is an effective Fenton-type catalyst, further adding to the proof that salicylate acts by redox deactivation of iron, not by hydroxyl radical scavenging. Finally, the iron-salicylate e.m.f. suggests that it may also act as a superoxide dismutase, which indicates another possible important antioxidant feature.     

Analysis of D2 d : a D-region class I gene

The mouse major histocompatibility complex is composed of several genes arranged into the K, D, Qa, and Tla regions. The D region of the BALB/c mouse includes genes D2 ^d , D3 ^d , and D4 ^d , in addition to H-2D ^d and H-2L ^d . We have determined the DNA sequence of the D2 ^d gene and compared it with the known sequences of several class I genes. The exon/intron structure of the D2 ^d gene is similar to other class I genes. It also contains similar 5 regulatory elements. A frameshift occurs in exon seven, resulting in a gene product with a truncated cytoplasmic tail. To examine the surface expression of the D2^d molecule, we generated an exon-shuffled construct containing the promoter and exons 1–3, encoding the signal peptide, 1, and 2 external domains of the D2 ^d gene linked to exons 4–8, encoding the 3, transmembrane and cytoplasmic domains, of the H-2D ^d gene. The construct was transfected into mouse L cells, and a protein was detected at the cell surface by a monoclonal antibody (mAb) specific for the 3 domain of H-2D^d, as well as by other class I-specific mAbs. Although D2^d is expressed at low levels, it may be a functional class I gene that most probably evolved from a Qa region gene.     

Survival of Microorganisms in a Rock Bed Under Conditions Simulating Solar Heat Storage

A laboratory-scale unit containing about 360 kg of washed river gravel was designed to [ill] the use of rocks for heat storage. The unit was operated under varying conditions of temperature, relative humidity, and the addition of volatile nutrients over a 4-month period. Effluent air and rock surfaces were monitored for the presence of microorganisms. After 2 weeks, virtually no microorganisms were detected in the effluent air except when dry soil or compost was added as the inoculum. A small number of heat-resistant bacteria, but no fungi, were found to survive on the rock surfaces. Microorganisms isolated were either sporeforming bacteria or actinomycetes closely resembling Thermoactinomyces vulgaris. Microbial colonization of rock beds used for solar heat storage does not appear likely under routine operation.     

Factors affecting anther culturability of recalcitrant barley genotypes

One major problem encountered with cereal anther culture is that some genotypes are low or non-responders to the technique. The objective of this study was to improve anther culture efficiency of recalcitrant barley (Hordeum vulgare L.) genotypes. Reciprocal F₁s between the two low responsive cultivars, Morex and Steptoe, were used. These were chosen because doubled haploids (DH) were required from these genotypes for the North American Barley Genome Mapping project. Ficoll 400 at 200 g l^–1 in the induction medium significantly increased green plant production compared to four other media formations containing different gelling/viscosity modifying agents. Cold pretreatment of donor spikes of 28 vs 14 d resulted in an increase in embryoid, total plant and green plant production. Anther culture response in these experiments was little influenced by donor plant growth conditions. Indole-3-acetic acid (1 mg l^–1) or 1-naphthaleneacetic acid (2 mg l^–1) in the induction medium did not affect anther culturability or plant regeneration. Based on this research, the negative genotypic effect for doubled haploid production could be diminished, which is desirable for practical application.Abbreviations BAP 6-benzylaminopurine - IAA Indole-3-acetic acid - LS Linsmaier & Skoog - NAA 1-naphthaleneacetic acid - DH doubled haploid     

Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff,Latvia

Luk?evi?s, E., Ahlberg, P.E., Stinkulis, ?., Vasi?kova, J. & Zupi??, I. 2011: Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff, Latvia. Lethaia, Vol. 45, pp. 356–370. The siliciclastic sequence of the Upper Devonian of Kurzeme, Western Latvia, is renowned for abundant vertebrate fossils, including the stem tetrapods Obruchevichthys gracilis and Ventastega curonica. During the first detailed taphonomic study of the vertebrate assemblage from the Ogre Formation cropping out at the Langsēde Cliff, Imula River, abundant vertebrate remains have been examined and identified as belonging to one psammosteid, two acanthodian and three sarcopterygian genera; the placoderm Bothriolepis maxima dominates the assemblage. Besides fully disarticulated placoderm and psammosteid plates, separate sarcopterygian scales and teeth, and acanthodian spines, partly articulated specimens including complete distal segments of Bothriolepis pectoral fins, Bothriolepis head shields and sarcopterygian lower jaws have been found. The size distribution of the placoderm bones demonstrates that the individuals within the assemblage are of approximately uniform age. Distinct zones have been traced within the horizontal distribution of the bones. These linear zones are almost perpendicular to the dominant dip azimuth of the cross‐beds and ripple‐laminae and most probably correspond to the depressions between subaqueous dunes. Concavity ratio varies significantly within the excavation area. The degree of fragmentation of the bones and disarticulation of the skeletons suggest that the carcasses were reworked and slightly transported before burial. Sedimentological data suggest deposition in a shallow marine environment under the influence of rapid currents. The fossiliferous bed consists of a basal bone conglomerate covered by a cross‐stratified sandstone with mud drapes, which is in turn overlain by ripple laminated sandstone, indicating the bones were buried by the gradual infilling of a tidal channel. All the Middle–Upper Devonian vertebrate bone‐beds from Latvia are associated with sandy to clayey deposits and have been formed in a sea‐coastal zone during rapid sedimentation episodes, but differ in fossil abundance and degree of preservation. □Agnathans, Devonian, facies analysis, fish, fossil assemblage, palaeoenvironment.     

A tree-based method for the rapid screening of chemical fingerprints

Background  

The fingerprint of a molecule is a bitstring based on its structure, constructed such that structurally similar molecules will have similar fingerprints. Molecular fingerprints can be used in an initial phase of drug development for identifying novel drug candidates by screening large databases for molecules with fingerprints similar to a query fingerprint.     

Barley necrotic locus nec1 encodes the cyclic nucleotide-gated ion channel 4 homologous to the Arabidopsis HLM1

Barley homolog of the Arabidopsis necrotic (disease lesion mimic) mutant HLM1 that encodes the cyclic nucleotide-gated ion channel 4 was cloned. Barley gene was mapped genetically to the known necrotic locus nec1 and subsequent sequence analysis identified mutations in five available nec1 alleles confirming barley homolog of Arabidopsis HLM1 as the NEC1 gene. Two fast neutron (FN) induced mutants had extensive deletions in the gene, while two previously described nec1 alleles had either a STOP codon in exon 1 or a MITE insertion in intron 2 which caused alternative splicing, frame shift and production of a predicted non-functional protein. The MITE insertion was consistent with the reported spontaneous origin of the nec1 Parkland allele. The third FN mutant had a point mutation in the coding sequence which resulted in an amino acid change in the conserved predicted cyclic nucleotide-gated ion channel pore region. The expression of two pathogenesis-related genes, HvPR-1a and β-1,3-glucanase, was elevated in two FN necrotic lines. Ten other members of the barley cyclic nucleotide-gated ion channel gene family were identified and their position on barley linkage map is reported. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Recrafting the neighbor-joining method

Background  

The neighbor-joining method by Saitou and Nei is a widely used method for constructing phylogenetic trees. The formulation of the method gives rise to a canonical Θ(n ³) algorithm upon which all existing implementations are based.