Toward Octavio Paz: A Reading of His Major Poems, 1957–1976

The undisputed intellectual leadership of Octavio Paz, not only in Mexico but throughout Spanish America, rests on achievements in the essay and in poetry. In the field of the essay, he is the author of more than twenty-five books on subjects whose diversity—esthetics, politics, surrealist art, the Mexican character, cultural anthropology, and Eastern philosophy, to cite only a few—is dazzling. In poetry, his creativity has increased in vigor over more than fifty years as he has explored the numerous possibilities open to Hispanic poets from many different sources. The bridge that joins the halves of his writing is a concern for language in general and for the poetic process in particular. Toward Octavio Paz defines this process of creation through a close examination of the books that represent the summit of the poet\u27s development, three long poems and three collections. It is intended for readers of varied poetic experience who are approaching Paz\u27s work for the first time. By studying the relationship of the parts of the poem, particularly structure and theme, Fein traces the poet\u27s growth through approaches to the reader, each embodied in a separate work. From the divided circularity of Piedra de sol through the intensification of the subject of Salamandra, the multiple meanings of Blanco, the polarities of Ladera este, and the literary solipsism of Pasado en claro, to the silences of Vuelta, Paz has shaped his audience\u27s responses to his work through suggestion rather than control. The result is not only a new poetry but a new receptivity. John M. Fein, professor of Romance languages at Duke University, is the author of Modemismo in Chilean Literature: The Second Period.https://uknowledge.uky.edu/upk_latin_american_literature/1004/thumbnail.jp

The Role of Inositol Phosphate Cascade in Visual Excitation of Invertebrate Microvillar Photoreceptors

The identity of the transmitter(s) involved in visual transduction in invertebrate microvillar photoreceptors remains unresolved. In this study, the role of inositol 1,4,5-trisphosphate (IP3) was examined in Limulus ventral photoreceptors by studying the effects on the light response of heparin and neomycin, agents that inhibit the production or action of IP3. Both heparin and neomycin reduce responses to brief flashes of light and the transient component of responses to steps of light, and also inhibit IP3-induced calcium release, indicating that IP3 plays a direct role in invertebrate visual excitation. The effects of BAPTA, a calcium buffer, were also examined and shown to be consistent with a role for IP3-mediated calcium release in visual excitation. However, all three agents fail to block the plateau component of the response to a step of light, indicating that a single pathway involving IP3 and calcium cannot solely be responsible for visual excitation in invertebrates. We suggest that the inositol phosphate cascade and a second parallel process that is not dependent on IP3 are involved in the production of the light response

Excitation of Limulus Photoreceptors by Hydrolysis-Resistant Analogs of cGMP and cAMP

cGMP was proposed to be the agent which directly opens the light-sensitive channel in Limulus ventral photoreceptors. However, the light-sensitive rhabdomeral-lobe (R-lobe) is not uniformly responsive to cGMP injection; that is, there are ‘hot spots’ of sensitivity. A potent phosphodiesterase which rapidly hydrolyses cGMP was suggested to explain the existence of these ‘hot spots’. To test this idea we injected ventral photoreceptors with hydrolysis-resistant cyclic nucleotide analogues. Whereas there can be a lack of a response to cGMP injection into the R-lobe, we find a reproducible depolarization upon R-lobe injection of hydrolysis-resistant cGMP analogues. Furthermore, the depolarization resulting from the injection of cGMP analogues does not require a rise in intracellular Ca2+, as it is not blocked by the Ca2+ buffer, BAPTA. Surprisingly, R-lobe injection of a hydrolysis-resistant cAMP analogue also depolarized ventral photoreceptors. Further work will be needed to resolve the role of cGMP in Limulus visual transduction