1,000 research outputs found
Vasopressin potentiates corticotropin-releasing hormone-induced insulin release from mouse pancreatic ÎČ-cells
Arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) have both
been implicated in modulating insulin secretion from pancreatic
ÎČ-cells. In the present study, we investigated the insulin-secreting
activities of AVP and CRH in wild-type and AVP VIb receptor knockout mice. Both
neuropeptides stimulated insulin secretion from isolated mouse pancreatic
islets. The response of islets to CRH was increased fourfold by concomitant
incubation with a subthreshold dose of AVP that alone did not stimulate insulin
secretion. Activation of the endogenously expressed M3 receptor by the
cholinergic agonist carbachol also potentiated CRH-induced insulin secretion,
indicating that the phenomenon may be pathway specific (i.e.
Ca2+-phospholipase C) rather than agonist
specific. The protein kinase C (PKC) inhibitors Ro-31-8425 and
bisindolylmaleimide I attenuated the potentiating effect of AVP on
CRH-stimulated insulin secretion and blocked AVP-stimulated insulin secretion. A
possible interaction between the PKC and protein kinase A pathways was also
investigated. The phorbol ester phorbol myristate acetate (PMA) stimulated
insulin secretion, while the addition of both PMA and CRH enhanced insulin
secretion over that measured with either PMA or CRH alone. Additionally, no AVP
potentiation of CRH-stimulated insulin secretion was observed upon incubation in
Ca2+-free KrebsâRinger buffer.
Taken together, the present study suggests a possible synergism between AVP and
CRH to release insulin from pancreatic ÎČ-cells that relies at least in
part on activation of the PKC signaling pathway and is dependent on
extracellular Ca2+. This is the first example of
a possible interplay between the AVP and CRH systems outside of the
hypothalamicâpituitaryâadrenal axis
Ăinghald aĂ° fornu : fornleifarannsĂłknir 2003
No abstract available
A dwarf nova in the globular cluster M13
Dwarf novae in globular clusters seem to be rare with only 13 detections in
the 157 known Galactic globular clusters. We report the identification of a new
dwarf nova in M13, the 14th dwarf nova identified in a globular cluster to
date. Using the 2m Faulkes Telescope North, we conducted a search for stars in
M13 that show variability over a year (2005-2006) on timescales of days and
months. This led to the detection of one dwarf nova showing several outbursts.
A Chandra X-ray source is coincident with this dwarf nova and shows both a
spectrum and variability consistent with that expected from a dwarf nova, thus
supporting the identification. We searched for a counterpart in Hubble Space
Telescope ACS/WFC archived images and found at least 11 candidates, of which we
could characterize only the 7 brightest, including one with a 3 sigma H-alpha
excess and a faint blue star. The detection of one dwarf nova when more could
have been expected likely indicates that our knowledge of the global Galactic
population of cataclysmic variables is too limited. The proportion of dwarf
novae may be lower than found in catalogs, or they may have a much smaller duty
cycle in general as proposed by some population synthesis models and recent
observations in the field.Comment: Accepted for publication in ApJ, 12 pages, 12 figures, 5 tables (v2
contains corrections of the proofs
Characterization of the near-Earth Asteroid 2002NY40
In August 2002, the near-Earth asteroid 2002 NY40, made its closest approach
to the Earth. This provided an opportunity to study a near-Earth asteroid with
a variety of instruments. Several of the telescopes at the Maui Space
Surveillance System were trained at the asteroid and collected adaptive optics
images, photometry and spectroscopy. Analysis of the imagery reveals the
asteroid is triangular shaped with significant self-shadowing. The photometry
reveals a 20-hour period and the spectroscopy shows that the asteroid is a
Q-type
Comparing families of dynamic causal models
Mathematical models of scientific data can be formally compared using Bayesian model evidence. Previous applications in the biological sciences have mainly focussed on model selection in which one first selects the model with the highest evidence and then makes inferences based on the parameters of that model. This âbest modelâ approach is very useful but can become brittle if there are a large number of models to compare, and if different subjects use different models. To overcome this shortcoming we propose the combination of two further approaches: (i) family level inference and (ii) Bayesian model averaging within families. Family level inference removes uncertainty about aspects of model structure other than the characteristic of interest. For example: What are the inputs to the system? Is processing serial or parallel? Is it linear or nonlinear? Is it mediated by a single, crucial connection? We apply Bayesian model averaging within families to provide inferences about parameters that are independent of further assumptions about model structure. We illustrate the methods using Dynamic Causal Models of brain imaging data
Effects Of Length, Complexity, And Grammatical Correctness On Stuttering In Spanish-Speaking Preschool Children
Purpose: To explore the effects of utterance length, syntactic complexity, and grammatical correctness on stuttering in the spontaneous speech of young, monolingual Spanish-speaking children. Method: Spontaneous speech samples of 11 monolingual Spanish-speaking children who stuttered, ages 35 to 70 months, were examined. Mean number of syllables, total number of clauses, utterance complexity (i.e., containing no clauses, simple clauses, or subordinate and/or conjoined clauses), and grammatical correctness (i.e., the presence or absence of morphological and syntactical errors) in stuttered and fluent utterances were compared. Results: Findings revealed that stuttered utterances in Spanish tended to be longer and more often grammatically incorrect, and contain more clauses, including more subordinate and/or conjoined clauses. However, when controlling for the interrelatedness of syllable number and clause number and complexity, only utterance length and grammatical incorrectness were significant predictors of stuttering in the spontaneous speech of these Spanish-speaking children. Use of complex utterances did not appear to contribute to the prediction of stuttering when controlling for utterance length. Conclusions: Results from the present study were consistent with many earlier reports of English-speaking children. Both length and grammatical factors appear to affect stuttering in Spanish-speaking children. Grammatical errors, however, served as the greatest predictor of stuttering.Communication Sciences and Disorder
Effects of ecstasy/polydrug use on memory for associative information
Rationale
Associative learning underpins behaviours that are fundamental to the everyday functioning of the individual. Evidence pointing to learning deficits in recreational drug users merits further examination.
Objectives
A word pair learning task was administered to examine associative learning processes in ecstasy/polydrug users.
Methods
After assignment to either single or divided attention conditions, 44 ecstasy/polydrug users and 48 non-users were presented with 80 word pairs at encoding. Following this, four types of stimuli were presented at the recognition phase: the words as originally paired (old pairs), previously presented words in different pairings (conjunction pairs), old words paired with new words, and pairs of new words (not presented previously). The task was to identify which of the stimuli were intact old pairs.
Results
Ecstasy/ploydrug users produced significantly more false-positive responses overall compared to non-users. Increased long-term frequency of ecstasy use was positively associated with the propensity to produce false-positive responses. It was also associated with a more liberal signal detection theory decision criterion value. Measures of long term and recent cannabis use were also associated with these same word pair learning outcome measures. Conjunction word pairs, irrespective of drug use, generated the highest level of false-positive responses and significantly more false-positive responses were made in the divided attention condition compared to the single attention condition.
Conclusions
Overall, the results suggest that long-term ecstasy exposure may induce a deficit in associative learning and this may be in part a consequence of users adopting a more liberal decision criterion value
The type IIb SN 2008ax: spectral and light curve evolution
We present spectroscopy and photometry of the He-rich supernova (SN) 2008ax.
The early-time spectra show prominent P-Cygni H lines, which decrease with time
and disappear completely about two months after the explosion. In the same
period He I lines become the most prominent spectral features. SN 2008ax
displays the ordinary spectral evolution of a type IIb supernova. A stringent
pre-discovery limit constrains the time of the shock breakout of SN 2008ax to
within only a few hours. Its light curve, which peaks in the B band about 20
days after the explosion, strongly resembles that of other He-rich
core-collapse supernovae. The observed evolution of SN 2008ax is consistent
with the explosion of a young Wolf-Rayet (of WNL type) star, which had retained
a thin, low-mass shell of its original H envelope. The overall characteristics
of SN 2008ax are reminiscent of those of SN 1993J, except for a likely smaller
H mass. This may account for the findings that the progenitor of SN 2008ax was
a WNL star and not a K supergiant as in the case of SN 1993J, that a prominent
early-time peak is missing in the light curve of SN 2008ax, and that Halpha is
observed at higher velocities in SN 2008ax than in SN 1993J.Comment: 10 pages, including 8 figures and 4 tables. Accepted for publication
in MNRA
GĂĄsir in EyjafjörÄur: International Exchange and Local Economy in Medieval Iceland
The site of GĂĄsir in EyjafjörĂ°ur in northeast Iceland was excavated from 2001â2006, revealing details of one of the larger seasonal trading centers of medieval Iceland. Interdisciplinary investigations of the site have shed light upon the organization of the site and provided confirmation of documentary accounts of both prestige items (gyrfalcons, walrus ivory) and bulk goods (sulphur) concentrated for export. GĂĄsir was a major point of cultural contact as well as economic exchange between Icelanders and the world of medieval Europe, and the zooarchaeological analyses indicated a mix of foodways and the presence of exotic animals and a well-developed provisioning system, which supplied high-quality meat and fresh fish to the traders. The excavations demonstrated an unexpected regional-level economic impact of the seasonally occupied site on the surrounding rural countryside, and contribute to ongoing investigations of the extent and impact of overseas trade in medieval Iceland
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