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Levels of insulin-like growth factor I (IGF-I), a neuroprotective hormone, decrease in serum during aging, whereas amyloid-[beta] (A[beta]), which is involved in the pathogenesis of Alzheimer disease, accumulates in the brain. High brain A[beta] levels are found at an early age in mutant mice with low circulating IGF-I, and A[beta] burden can be reduced in aging rats by increasing serum IGF-I. This opposing relationship between serum IGF-I and brain A[beta] levels reflects the ability of IGF-I to induce clearance of brain A[beta], probably by enhancing transport of A[beta] carrier proteins such as albumin and transthyretin into the brain. This effect is antagonized by tumor necrosis factor-[alpha], a pro-inflammatory cytokine putatively involved in dementia and aging. Because IGF-I treatment of mice overexpressing mutant amyloid markedly reduces their brain A[beta] burden, we consider that circulating IGF-I is a physiological regulator of brain amyloid levels with therapeutic potential., Author(s): E. Carro [1]; J.L. Trejo [1]; T. Gomez-Isla [2]; D. LeRoith [3]; I. Torres-Aleman (corresponding author) [1] Insulin and insulin-like growth factor I (IGF-I) are structurally related circulating hormones. [...]

We performed a detailed spectroscopic analysis of the fullerene C60-containing planetary nebula (PN) Lin49 in the Small Magellanic Cloud (SMC) using XSHOOTER at the European Southern Observatory Very Large Telescope and the Spitzer/Infrared Spectrograph instruments. We derived nebular abundances for nine elements. We used TLUSTY to derive photospheric parameters for the central star. Lin49 is C-rich and metal-deficient PN (Z ~ 0.0006). The nebular abundances are in good agreement with asymptotic giant branch nucleosynthesis models for stars with initial mass 1.25 M⊙ and metallicity Z = 0.001. Using the TLUSTY synthetic spectrum of the central star to define the heating and ionizing source, we constructed the photoionization model with CLOUDY that matches the observed spectral energy distribution (SED) and the line fluxes in the UV to far-IR wavelength ranges simultaneously. We could not fit the ~1-5 μm SED using a model with 0.005-0.1-μm-sized graphite grains and a constant hydrogen density shell owing to the prominent near-IR excess, while at other wavelengths the model fits the observed values reasonably well. We argue that the near-IR excess might indicate either (1) the presence of very small particles in the form of small carbon clusters, small graphite sheets, or fullerene precursors, or (2) the presence of a high-density structure surrounding the central star. We found that SMC C60 PNe show a near-IR excess component to lesser or greater degree. This suggests that these C60 PNe might maintain a structure nearby their central star. [ABSTRACT FROM AUTHOR]

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]

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]

We study the kinematics and excitation mechanisms of H2 and [Fe ii] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (0.8–2.4 μm) spectroscopy together with new photoionization models. H2 emission lines are systematically narrower than narrow-line region lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star-forming galaxies. The importance of the thermal excitation in star-forming galaxies may be associated with the presence of supernova remnants close to the region emitting H2 lines. This hypothesis is further supported by the similarity between vibrational and rotational temperatures of H2. We confirm that the diagram involving the line ratios H2 2.121 μm/Brγ and [Fe ii] 1.257 μm/Paβ is an efficient tool for separating emission-line objects according to their dominant types of activities. We suggest new limits to the line ratios in order to discriminate between the different types of nuclear activities. [ABSTRACT FROM AUTHOR]

Context. Detections of molecular lines, mainly from H2 and CO, reveal molecular material in planetary nebulae. Observations of a variety of molecules suggest that the molecular composition in these objects differs from that found in interstellar clouds or in circumstellar envelopes. The success of the models, which are mostly devoted to explain molecular densities in specific planetary nebulae, is still partial however. Aims. The present study aims at identifying the influence of stellar and nebular properties on the molecular composition of planetary nebulae by means of chemical models. A comparison of theoretical results with those derived from the observations may provide clues to the conditions that favor the presence of a particular molecule. Methods. A self-consistent photoionization numerical code was adapted to simulate cold molecular regions beyond the ionized zone. The code was used to obtain a grid of models and the resulting column densities are compared with those inferred from observations. Results. Our models show that the inclusion of an incident flux of X-rays is required to explain the molecular composition derived for planetary nebulae. We also obtain a more accurate relation for the N(CO)/N(H2) ratio in these objects. Molecular masses obtained by previous works in the literature were then recalculated, showing that these masses can be underestimated by up to three orders of magnitude. We conclude that the problem of the missing mass in planetary nebulae can be solved by a more accurate calculation of the molecular mass. [ABSTRACT FROM AUTHOR]

Abstract: Peripheral and central diabetic neuropathies were studied in streptozotocin-diabetic rats, using behavioral, biochemical and electrophysiological techniques. Diabetic rats showed thermal hypoalgesia and decreasing motor nerve conduction velocity at 4 and 8 weeks of diabetes. In addition, amplitude of the evoked potential recorded in primary somatosensory cortex after stimulation of the sciatic nerve was markedly reduced at 8 weeks of diabetes. This decrease was accompanied by decreases in GluR2/3 AMPA receptor subunits. These changes seem to be specific to the somatosensory system and to originate in higher centers since they were not present in the hippocampus and were not observed at the level of gracilis nucleus. Insulin-like growth factor I (IGF-I) treatment reversed the reduced thermal sensitivity and peripheral nerve conduction velocity but did not reverse changes in the CNS, suggesting that once initiated, both anomalies may develop independently in this model of diabetic neuropathy. In conclusion, the results indicate that diabetes induces a wide spectrum of alterations in the central somatosensory system that are independent of the decreases in peripheral sensory transmission that could be responsible for the disturbances in somatosensory perception observed in diabetes. [Copyright &y& Elsevier]

Levels of insulin-like growth factor I (IGF-I), a neuroprotective hormone, decrease in serum during aging, whereas amyloid-β (Aβ), which is involved in the pathogenesis of Alzheimer disease, accumulates in the brain. High brain Aβ levels are found at an early age in mutant mice with low circulating IGF-I, and Aβ burden can be reduced in aging rats by increasing serum IGF-I. This opposing relationship between serum IGF-I and brain Aβ levels reflects the ability of IGF-I to induce clearance of brain Aβ, probably by enhancing transport of Aβ carrier proteins such as albumin and transthyretin into the brain. This effect is antagonized by tumor necrosis factor-α, a pro-inflammatory cytokine putatively involved in dementia and aging. Because IGF-I treatment of mice overexpressing mutant amyloid markedly reduces their brain Aβ burden, we consider that circulating IGF-I is a physiological regulator of brain amyloid levels with therapeutic potential. [ABSTRACT FROM AUTHOR]

Abstract Exogenous administration of insulin-like growth factor I (IGF-I) restores motor function in rats with neurotoxin-induced cerebellar deafferentation. We first determined that endogenous IGFs are directly involved in the recovery process because infusion of an IGF-I receptor antagonist into the lateral ventricle blocks gradual recovery of limb coordination that spontaneously occurs after partial deafferentation of the olivo-cerebellar circuitry. We then analysed mechanisms whereby exogenous IGF-I restores motor function in rats with complete damage of the olivo-cerebellar pathway. Treatment with IGF-I normalized several markers of cell function in the cerebellum, including calbindin, glutamate receptor 1 (GluR1), γ-aminobutyric acid (GABA) and glutamate, which are all depressed after 3-acetylpyridine (3AP)-induced deafferentation. IGF-I also promoted functional reinnervation of the cerebellar cortex by inferior olive (IO) axons. In the IO, increased expression of bax in neurons and bcl-X in astrocytes after 3AP was significantly reduced by IGF-I treatment. On the contrary, IGF-I prevented the decrease in poly-sialic-acid neural cell adhesion molecule (PSA-NCAM) and GAP-43 expression induced by 3AP in IO cells. IGF-I also significantly increased the number of neurons expressing bcl-2 in brainstem areas surrounding the IO. Altogether, these results indicate that subcutaneous IGF-I therapy promotes functional recovery of the olivo-cerebellar pathway by acting at two sites within this circuitry: (i) by modulating death- and plasticity-related proteins in IO neurons; and (ii) by impinging on homeostatic mechanisms leading to normalization of cell function in the cerebellum. These results provide insight into the neuroprotective actions of IGF-I and may be of practical consequence in the design of new therapeutic approaches for neurodegenerative diseases. [ABSTRACT FROM AUTHOR]