Energy-Momentum Distribution: Some Examples

In this paper, we elaborate the problem of energy-momentum in General Relativity with the help of some well-known solutions. In this connection, we use the prescriptions of Einstein, Landau-Lifshitz, Papapetrou and M\"{o}ller to compute the energy-momentum densities for four exact solutions of the Einstein field equations. We take the gravitational waves, special class of Ferrari-Ibanez degenerate solution, Senovilla-Vera dust solution and Wainwright-Marshman solution. It turns out that these prescriptions do provide consistent results for special class of Ferrari-Ibanez degenerate solution and Wainwright-Marshman solution but inconsistent results for gravitational waves and Senovilla-Vera dust solution.Comment: 20 pages, accepted for publication in Int. J. Mod. Phys.

Oxylipins in moss development and defense

Oxylipins are oxygenated fatty acids that participate in plant development and defense against pathogen infection, insects and wounding. Initial oxygenation of substrate fatty acids is mainly catalyzed by lipoxygenases and alpha-dioxygenases but can also take place non-enzymatically by autoxidation or singlet oxygen-dependent reactions. The resulting hydroperoxides are further metabolized by secondary enzymes to produce a large variety of compounds, including the hormone jasmonic acid and short-chain green leaf volatiles. In flowering plants, which lack arachidonic acid, oxylipins are produced mainly from oxidation of polyunsaturated C18 fatty acids, notably linolenic and linoleic acids. Algae and mosses in addition possess polyunsaturated C20 fatty acids including arachidonic and eicosapentaenoic acids, which can also be oxidized by lipoxygenases and transformed into bioactive compounds. Mosses are phylogenetically placed between unicellular green algae and flowering plants, allowing evolutionary studies of the different oxylipin pathways. During the last years the moss Physcomitrella patens has become an attractive model plant for understanding oxylipin biosynthesis and diversity. In addition to the advantageous evolutionary position, functional studies of the different oxylipin-forming enzymes can be performed in this moss by targeted gene disruption or single point mutations by means of homologous recombination. Biochemical characterization of several oxylipin-producing enzymes and oxylipin profiling in P. patens reveal the presence of a wider range of oxylipins compared to flowering plants, including C18 as well as C20-derived oxylipins. Surprisingly, one of the most active oxylipins in plants, jasmonic acid, is not synthesized in this moss. In this review we present an overview of oxylipins produced in mosses and discuss the current knowledge related to the involvement of oxylipin-producing enzymes and their products in moss development and defense

The role of vacuolar and secreted pathogenesis-related β (1-3)-glucanases and chitinases in the defence response of plants

Upon infection of a plant by a pathogen, a series of drastic metabolic changes occur within the plant. One characteristic feature of this defence response is the synthesis of the so-called pathogenesis-related (PR) proteins. We have studied the nature, structure, and subcellular localization of the different PR proteins upon salicylic acid treatment and Pseudomonas syringae infection of Nicotiana tabacum plants. In both test systems, we could demonstrate that the PR protein fraction of tobacco consists of at least 20 to 25 different proteins, including beta (1-3)-glucanases, chitinases, peroxidases, thaumatin-like proteins, the PR1 class proteins and a proteinase inhibitor-like protein. Moreover, several classes of these PR proteins segregate into specific vacuolar and secreted isoforms. Here, we present a model which could explain the role of the compartimentalized PR beta (1-3)-glucanases and chitinases within the regulation of the defence response

Delirio de parasitosis. A propósito de un caso.

Sin resumen

La situación asistencial de la provincia de Santa Cruz de Tenerife.

Los autores exponen la situación actual de asistencia psiquiátrica en la provincia de Santa Cruz de Tenerife. Se pone de manifiesto la falta de una coordinación entre los distintos dispositivos asistenci

La situación asistencial de la provincia de Santa Cruz de Tenerife.

Los autores exponen la situación actual de asistencia psiquiátrica en la provincia de Santa Cruz de Tenerife. Se pone de manifiesto la falta de una coordinación entre los distintos dispositivos asistenci

Delirio de parasitosis. A propósito de un caso.

Sin resumen

The Physcomitrella patens unique alpha-dioxygenase participates in both developmental processes and defense responses

[Background] Plant α-dioxygenases catalyze the incorporation of molecular oxygen into polyunsaturated fatty acids leading to the formation of oxylipins. In flowering plants, two main groups of α-DOXs have been described. While the α-DOX1 isoforms are mainly involved in defense responses against microbial infection and herbivores, the α-DOX2 isoforms are mostly related to development. To gain insight into the roles played by these enzymes during land plant evolution, we performed biochemical, genetic and molecular analyses to examine the function of the single copy moss Physcomitrella patens α-DOX (Ppα-DOX) in development and defense against pathogens.[Results] Recombinant Ppα-DOX protein catalyzed the conversion of fatty acids into 2-hydroperoxy derivatives with a substrate preference for α-linolenic, linoleic and palmitic acids. Ppα-DOX is expressed during development in tips of young protonemal filaments with maximum expression levels in mitotically active undifferentiated apical cells. In leafy gametophores, Ppα-DOX is expressed in auxin producing tissues, including rhizoid and axillary hairs. Ppα-DOX transcript levels and Ppα-DOX activity increased in moss tissues infected with Botrytis cinerea or treated with Pectobacterium carotovorum elicitors. In B. cinerea infected leaves, Ppα-DOX-GUS proteins accumulated in cells surrounding infected cells, suggesting a protective mechanism. Targeted disruption of Ppα-DOX did not cause a visible developmental alteration and did not compromise the defense response. However, overexpressing Ppα-DOX, or incubating wild-type tissues with Ppα-DOX-derived oxylipins, principally the aldehyde heptadecatrienal, resulted in smaller moss colonies with less protonemal tissues, due to a reduction of caulonemal filament growth and a reduction of chloronemal cell size compared with normal tissues. In addition, Ppα-DOX overexpression and treatments with Ppα-DOX-derived oxylipins reduced cellular damage caused by elicitors of P. carotovorum.[Conclusions] Our study shows that the unique α-DOX of the primitive land plant P. patens, although apparently not crucial, participates both in development and in the defense response against pathogens, suggesting that α-DOXs from flowering plants could have originated by duplication and successive functional diversification after the divergence from bryophytes.This work was supported by Agencia Nacional de Investigación e Innovación (ANII) [grants FCE2007_376, FCE2011_6095, fellowships BE_POS_2009_726 (A. Castro) and BE_POS_2010_2533 (L. Machado)], UdelaR Uruguay/CSIC Spain (Joint project), the Swedish Research Council, and Programa de Desarrollo de las Ciencias Básicas (PEDECIBA) Uruguay. The Ppα-DOX cDNA was obtained from the RIKEN Biological Research Center, Tsukuba, Japan