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322 results on '"Aleman, I."'

67. Herschel Planetary Nebula Survey (HerPlaNS) First detection of OH+ in planetary nebulae.

Author

Aleman, I., Ueta, T., Ladjal, D., Exter, K. M., Kastner, J. H., Montez Jr., R., Tielens, A. G. G. M., Chu, Y.-H., Izumiura, H., McDonald, I., Sahai, R., Siódmiak, N., Szczerba, R., van Hoof, P. A. M., Villaver, E., Vlemmings, W., Wittkowski, M., and Zijlstra, A. A.

Subjects
*PLANETARY nebulae, *FAR infrared lasers, *PHOTODISSOCIATION, *CIRCUMSTELLAR matter, *ASTROCHEMISTRY
Abstract

Aims. We report the first detections of OH+ emission in planetary nebulae (PNe). Methods. As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed a line survey in these PNe over the entire spectral range between 51 μm and 672 μm to look for new detections. Results. The rotational emission lines of OH+ at 152.99, 290.20, 308.48, and 329.77 μm were detected in the spectra of three planetary nebulae: NGC 6445, NGC6720, and NGC 6781. Excitation temperatures and column densities derived from these lines are in the range of 27–47 K and 2 × 1010–4 × 1011 cm−2, respectively. Conclusions. In PNe, the OH+ rotational line emission appears to be produced in the photodissociation region (PDR) in these objects. The emission of OH+ is observed only in PNe with hot central stars (Teff > 100 000 K), suggesting that high-energy photons may play a role inOH+ formation and its line excitation in these objects, as seems to be the case for ultraluminous galaxies. [ABSTRACT FROM AUTHOR]

Published
2014
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68. The Herschel Planetary Nebula Survey (HerPlaNS) I. Data overview and analysis demonstration with NGC6781.

Author

Ueta, T., Ladjal, D., Exter, K. M., Otsuka, M., Szczerba, R., Siódmiak, N., Aleman, I., van Hoof, P. A. M., Kastner, J. H., Montez Jr., R., McDonald, I., Wittkowski, M., Sandin, C., Ramstedt, S., DeMarco, O., Villaver, E., Chu, Y.-H., Vlemmings, W., Izumiura, H., and Sahai, R.

Subjects
PLANETARY nebulae, ASTRONOMICAL surveys, DATA analysis, SPECTRAL energy distribution, INTERPLANETARY dust
Abstract

Context. This is the first of a series of investigations into far-IR characteristics of 11 planetary nebulae (PNe) under the Herschel Space Observatory open time 1 program, Herschel Planetary Nebula Survey (HerPlaNS). Aims. Using the HerPlaNS data set, we look into the PN energetics and variations of the physical conditions within the target nebulae. In the present work, we provide an overview of the survey, data acquisition and processing, and resulting data products. Methods. We performed (1) PACS/SPIRE broadband imaging to determine the spatial distribution of the cold dust component in the target PNe and (2) PACS/SPIRE spectral-energy-distribution and line spectroscopy to determine the spatial distribution of the gas component in the target PNe. Results. For the case of NGC 6781, the broadband maps confirm the nearly pole-on barrel structure of the amorphous carbon-rich dust shell and the surrounding halo having temperatures of 26−40K. The PACS/SPIRE multiposition spectra show spatial variations of far-IR lines that reflect the physical stratification of the nebula. We demonstrate that spatially resolved far-IR line diagnostics yield the (Te, ne) profiles, from which distributions of ionized, atomic, and molecular gases can be determined. Direct comparison of the dust and gas column mass maps constrained by the HerPlaNS data allows to construct an empirical gas-to-dust mass ratio map, which shows a range of ratios with the median of 195 ± 110. The present analysis yields estimates of the total mass of the shell to be 0.86 M⊙, consisting of 0.54 M⊙ of ionized gas, 0.12 M⊙ of atomic gas, 0.2 M⊙ of molecular gas, and 4 × 10−3 M⊙ of dust grains. These estimates also suggest that the central star of about 1.5M⊙ initial mass is terminating its PN evolution onto the white dwarf cooling track. Conclusions. The HerPlaNS data provide various diagnostics for both the dust and gas components in a spatially resolved manner. In the forthcoming papers of the HerPlaNS series we will explore the HerPlaNS data set fully for the entire sample of 11 PNe. [ABSTRACT FROM AUTHOR]

Published
2014
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92. Insulin-like growth factor-I stimulates dephosphorylation of ikappa B through the serine phosphatase calcineurin (protein phosphatase 2B).

Author

Pons, S and Torres-Aleman, I

Abstract

Astrocytes represent the most abundant cell type of the adult nervous system. Under normal conditions, astrocytes participate in neuronal feeding and detoxification. However, following brain injury, local increases in inflammatory cytokines trigger a reactive phenotype in astrocytes during which these cells produce their own inflammatory cytokines and neurotoxic free radicals. Indeed, progression of this inflammatory reaction is responsible for most neurological damage associated with brain trauma. Insulin-like growth factor-I (IGF-I) protects neurons against a variety of brain pathologies associated with glial overproduction of proinflammatory cytokines. Here, we demonstrate that in astrocyte cultures IGF-I regulates NFkappaB, a transcription factor known to play a key role in the inflammatory reaction. IGF-I induces a site-specific dephosphorylation of IkappaBalpha (phospho-Ser(32)) in astrocytes. Moreover, IGF-I-mediated dephosphorylation of IkappaBalpha protects this molecule from tumor necrosis factor alpha (TNFalpha)-stimulated degradation; therefore, IGF-I also inhibits the nuclear translocation of NFkappaB (p65) induced by TNFalpha exposure. Finally, we show that dephosphorylation of IkappaBalpha by IGF-I pathways requires activation of calcineurin. Activation of this phosphatase is independent of phosphatidylinositol 3-kinase and mitogen-activated protein kinase. Thus, these data suggest that the therapeutic benefits associated with IGF-I treatment of brain injury are derived from both its positive effects on neuronal survival and inhibition of the glial inflammatory reaction.

Published
2000
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99. Inhibition of growth of a prolactin-secreting pituitary tumor in rats by analogs of luteinizing hormone-releasing hormone and somatostatin.

Author

de Quijada, M G, Redding, T W, Coy, D H, Torres-Aleman, I, and Schally, A V

Abstract

We investigated the effects of [D-Trp6]LH-RH [agonistic analog of luteinizing hormone-releasing hormone (LH-RH)], N-Ac-[D-p-Cl-Phe1,2,D-Trp3,D-Phe6,D-Ala10]LH-RH (antagonistic analog), and [D-5-methoxy-Trp8]somatostatin (somatostatin analog) on the growth of the prolactin and corticotropin-secreting pituitary tumor 7315a in female Buffalo rats. Chronic administration of [D-Trp6]LH-RH in a dose of 25 micrograms/day, starting 18 days after inoculation with the tumor, inhibited the growth of the pituitary tumor. Tumor weight and volume also were reduced when this agonist was administered 3 days after inoculation. The antagonistic LH-RH analog, injected in a dose of 50-100 micrograms for 14-24 days, also significantly inhibited the growth of pituitary tumor. Chronic administration of the somatostatin analog in a dose of 25 micrograms twice a day likewise decreased tumor weights in comparison with controls. The inhibition of pituitary tumor growth by LH-RH agonist, LH-RH antagonist, and somatostatin analog was accompanied by a decrease in serum prolactin levels. It was concluded that LH-RH agonist, LH-RH antagonist, and somatostatin analog can inhibit the growth of estrogen-dependent prolactin/corticotropin-secreting pituitary tumor in rats.

Published
1983
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100. The peripheral insulin-like growth factor system in amyotrophic lateral sclerosis and in multiple sclerosis

Author

Torres-Aleman, I., Barrios, V., and Berciano, J.

Abstract

A lack of trophic support may lead to degeneration of adult nerve cells. Several growth factors, including insulin-like growth factor I (IGF-I), control the survival of spinal motor neurons during development as well as after experimental injury. These neurons are selectively affected in patients with amyotrophic lateral sclerosis (ALS). Thus, we analyzes whether reduced levels of circulating IGF-I may be present in this disease. Significant increases were found in three of four of the main circulating IGF-binding proteins in ALS patients, whereas serum IGF-I and insulin levels were significantly reduced. On the contrary, multiple sclerosis patients did not show any significant change in the IGF-I trophic system even though oligodendrocytes are known targets of the trophic action of IGF-I. These results suggest an involvement of the peripheral IGF-I trophic system in ALS.

Published
1998

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