Coplas por las folias, y otras por el A, B, C. [Texto impreso]

Contiene: Glosas de un amante, que se despide de su dama, hechas por el A, B, C ; Respuesta de la Dama en las otras letras restantes del abecedario

Proceedings of the California Academy of Sciences, 4th series.

4th ser. v. 18 (1929-1930)

Melquisedec, sacerdote de el elyon Uma exegese de Gênesis 14,18-20

Neste estudo, que tem por base Gênesis 14,18-20, se discute a respeito de Melquisedec, o rei de Salém e seu deus el elyon , de quem é sacerdote (v.18). O texto é pós-exílico, sendo uma inserção ao capítulo 14, e reflete a história de Judá no período de sua restauração (séculos 6º a 4º a.C.), numa época em que o sacerdócio de Jerusalém assumiu gradativamente um poder sem precedentes em sua história, de maneira que o sumo-sacerdote acabou por se tornar uma autoridade civil. Melquisedec, que recebe o dízimo de Abrão, é uma imagem que evoca o poder do culto hierosolimitano na sociedade judaíta e seu alegado direito aos dízimos e ofertas oriundos do povo. Mas Melquisedec, usado num texto tardio, pertence a tradições anteriores ao exílio de Judá, segundo as quais o rei também desempenhava papel sacerdotal, como chefe religioso e intendente de Iahweh (Salmo 110). Essa dupla função foi um meio de legitimar as estruturas de poder caracterizadas por uma organização sóciopolítico- econômica que, em aspectos gerais, se ajusta ao conceito de modo de produção tributário. Assim, todo um discurso construído sobre a pessoa do rei e sobre outros aspectos ideológicos, tais quais a teologia de Sião (Salém), serviam de suporte para a manutenção do status quo. E em tal discurso coube o uso do universo simbólico da religião. Neste estudo, aventa-se a hipótese de que el elyon seja um nome composto, no qual subjazem el, que corresponde ao deus supremo do panteão cananeu (o ugarítico ilu), que tem como um de seus atributos o fato de haver gerado céus e terra (o que situa a tradição em concepções cosmogônicas médio-orientais arcaicas); e elyon, o qual parece esconder as características de outro deus, Ba al (Salmo 18, 7-17). Nota-se dessa maneira que o nome do deus de Melquisedec é a combinação sincrética de características de duas grandes divindades do panteão cananeu

Melquisedec, sacerdote de el elyon Uma exegese de Gênesis 14,18-20

Neste estudo, que tem por base Gênesis 14,18-20, se discute a respeito de Melquisedec, o rei de Salém e seu deus el elyon , de quem é sacerdote (v.18). O texto é pós-exílico, sendo uma inserção ao capítulo 14, e reflete a história de Judá no período de sua restauração (séculos 6º a 4º a.C.), numa época em que o sacerdócio de Jerusalém assumiu gradativamente um poder sem precedentes em sua história, de maneira que o sumo-sacerdote acabou por se tornar uma autoridade civil. Melquisedec, que recebe o dízimo de Abrão, é uma imagem que evoca o poder do culto hierosolimitano na sociedade judaíta e seu alegado direito aos dízimos e ofertas oriundos do povo. Mas Melquisedec, usado num texto tardio, pertence a tradições anteriores ao exílio de Judá, segundo as quais o rei também desempenhava papel sacerdotal, como chefe religioso e intendente de Iahweh (Salmo 110). Essa dupla função foi um meio de legitimar as estruturas de poder caracterizadas por uma organização sóciopolítico- econômica que, em aspectos gerais, se ajusta ao conceito de modo de produção tributário. Assim, todo um discurso construído sobre a pessoa do rei e sobre outros aspectos ideológicos, tais quais a teologia de Sião (Salém), serviam de suporte para a manutenção do status quo. E em tal discurso coube o uso do universo simbólico da religião. Neste estudo, aventa-se a hipótese de que el elyon seja um nome composto, no qual subjazem el, que corresponde ao deus supremo do panteão cananeu (o ugarítico ilu), que tem como um de seus atributos o fato de haver gerado céus e terra (o que situa a tradição em concepções cosmogônicas médio-orientais arcaicas); e elyon, o qual parece esconder as características de outro deus, Ba al (Salmo 18, 7-17). Nota-se dessa maneira que o nome do deus de Melquisedec é a combinação sincrética de características de duas grandes divindades do panteão cananeu

Crystal structure of a thermostable type B DNA polymerase from Thermococcus gorgonarius

Most known archaeal DNA polymerases belong to the type B family, which also includes the DNA replication polymerases of eukaryotes, but maintain high fidelity at extreme conditions. We describe here the 2.5 Å resolution crystal structure of a DNA polymerase from the Archaea Thermococcus gorgonarius and identify structural features of the fold and the active site that are likely responsible for its thermostable function. Comparison with the mesophilic B type DNA polymerase gp43 of the bacteriophage RB69 highlights thermophilic adaptations, which include the presence of two disulfide bonds and an enhanced electrostatic complementarity at the DNA–protein interface. In contrast to gp43, several loops in the exonuclease and thumb domains are more closely packed; this apparently blocks primer binding to the exonuclease active site. A physiological role of this “closed” conformation is unknown but may represent a polymerase mode, in contrast to an editing mode with an open exonuclease site. This archaeal B DNA polymerase structure provides a starting point for structure-based design of polymerases or ligands with applications in biotechnology and the development of antiviral or anticancer agents.

The mechanism of proton pumping by cytochrome c oxidase

Cytochrome c oxidase catalyzes the reduction of oxygen to water that is accompanied by pumping of four protons across the mitochondrial or bacterial membrane. Triggered by the results of recent x-ray crystallographic analyses, published data concerning the coupling of individual electron transfer steps to proton pumping are reanalyzed: Conversion of the conventional oxoferryl intermediate F to the fully oxidized form O is connected to pumping of only one proton. Most likely one proton is already pumped during the double reduction of O, and only three protons during conversion of the “peroxy” forms P to O via the oxoferryl form F. Based on the available structural, spectroscopic, and mutagenesis data, a detailed mechanistic model, carefully considering electrostatic interactions, is presented. In this model, each of the four reductions of heme a during the catalytic cycle is coupled to the uptake of one proton via the D-pathway. These protons, but never more than two, are temporarily stored in the regions of the heme a and a3 propionates and are driven to the outside (“pumped”) by electrostatic repulsion from protons entering the active site during turnover. The first proton is pumped by uptake of one proton via the K-pathway during reduction, the second and third proton during the P → F transition when the D-pathway and the active site become directly connected, and the fourth one upon conversion of F to O. Atomic structures are assigned to each intermediate including F′ with an alternative route to O.

Proteinase inhibitors I and II from potatoes specifically block UV-induced activator protein-1 activation through a pathway that is independent of extracellular signal-regulated kinases, c-Jun N-terminal kinases, and P38 kinase

Solar UV irradiation is the causal factor for the increasing incidence of human skin carcinomas. The activation of the transcription factor activator protein-1 (AP-1) has been shown to be responsible for the tumor promoter action of UV light in mammalian cells. We demonstrate that proteinase inhibitor I (Inh I) and II (Inh II) from potato tubers, when applied to mouse epidermal JB6 cells, block UV-induced AP-1 activation. The inhibition appears to be specific for UV-induced signal transduction for AP-1 activation, because these inhibitors did not block UV-induced p53 activation nor did they exhibit any significant influence on epidermal growth factor-induced AP-1 transactivation. Furthermore, the inhibition of UV-induced AP-1 activity occurs through a pathway that is independent of extracellular signal-regulated kinases and c-Jun N-terminal kinases as well as P38 kinases. Considering the important role of AP-1 in tumor promotion, it is possible that blocking UV-induced AP-1 activity by Inh I or Inh II may be functionally linked to irradiation-induced cell transformation.

Sequential and coordinated action of phytochromes A and B during Arabidopsis stem growth revealed by kinetic analysis

Photoreceptor proteins of the phytochrome family mediate light-induced inhibition of stem (hypocotyl) elongation during the development of photoautotrophy in seedlings. Analyses of overt mutant phenotypes have established the importance of phytochromes A and B (phyA and phyB) in this developmental process, but kinetic information that would augment emerging molecular models of phytochrome signal transduction is absent. We have addressed this deficiency by genetically dissecting phytochrome-response kinetics, after having solved the technical issues that previously limited growth studies of small Arabidopsis seedlings. We show here, with resolution on the order of minutes, that phyA initiated hypocotyl growth inhibition upon the onset of continuous red light. This primary contribution of phyA began to decrease after 3 hr of irradiation, the same time at which immunochemically detectable phyA disappeared and an exclusively phyB-dependent phase of inhibition began. The sequential and coordinated actions of phyA and phyB in red light were not observed in far-red light, which inhibited growth persistently through an exclusively phyA-mediated pathway.

CD19 and CD22 expression reciprocally regulates tyrosine phosphorylation of Vav protein during B lymphocyte signaling

B cell development and humoral immune responses are controlled by signaling thresholds established through the B lymphocyte antigen receptor (BCR) complex. BCR signaling thresholds are differentially regulated by the CD22 and CD19 cell surface receptors in vivo. B cells from CD22-deficient mice exhibit characteristics of chronic stimulation and are hyper-responsive to BCR crosslinking with augmented intracellular Ca2+ responses. By contrast, B cells from CD19-deficient mice are hypo-responsive to transmembrane signals. To identify signaling molecules involved in the positive and negative regulation of signaling thresholds, the signal transduction pathways activated after BCR crosslinking were examined in CD22- and CD19-deficient B cells. These comparisons revealed that tyrosine phosphorylation of Vav protein was uniquely augmented after BCR or CD19 crosslinking in CD22-deficient B cells, yet was modest and transient after BCR crosslinking in CD19-deficient B cells. Ligation of CD19 and CD22 in vivo is likely to positively and negatively regulate BCR signaling, respectively, because CD19 crosslinking was more efficient than BCR crosslinking at inducing Vav phosphorylation. However, simultaneous crosslinking of CD19 with the BCR resulted in a substantial decrease in Vav phosphorylation when CD22 was expressed. Thus, the differential regulation of Vav tyrosine phosphorylation by CD19 and CD22 may provide a molecular mechanism for adjusting BCR signaling thresholds.

Effect of reduced myristoylated alanine-rich C kinase substrate expression on hippocampal mossy fiber development and spatial learning in mutant mice: Transgenic rescue and interactions with gene background

The myristoylated alanine-rich C kinase substrate (MARCKS) is a prominent protein kinase C (PKC) substrate in brain that is expressed highly in hippocampal granule cells and their axons, the mossy fibers. Here, we examined hippocampal infrapyramidal mossy fiber (IP-MF) limb length and spatial learning in heterozygous Macs mutant mice that exhibit an ≈50% reduction in MARCKS expression relative to wild-type controls. On a 129B6(N3) background, the Macs mutation produced IP-MF hyperplasia, a significant increase in hippocampal PKCɛ expression, and proficient spatial learning relative to wild-type controls. However, wild-type 129B6(N3) mice exhibited phenotypic characteristics resembling inbred 129Sv mice, including IP-MF hypoplasia relative to inbred C57BL/6J mice and impaired spatial-reversal learning, suggesting a significant contribution of 129Sv background genes to wild-type and possibly mutant phenotypes. Indeed, when these mice were backcrossed with inbred C57BL/6J mice for nine generations to reduce 129Sv background genes, the Macs mutation did not effect IP-MF length or hippocampal PKCɛ expression and impaired spatial learning relative to wild-type controls, which now showed proficient spatial learning. Moreover, in a different strain (B6SJL(N1), the Macs mutation also produced a significant impairment in spatial learning that was reversed by transgenic expression of MARCKS. Collectively, these data indicate that the heterozygous Macs mutation modifies the expression of linked 129Sv gene(s), affecting hippocampal mossy fiber development and spatial learning performance, and that MARCKS plays a significant role in spatial learning processes.