3,685 research outputs found
Interactions between nutrition and gastrointestinal infections with parasitic nematodes in goats
Parasitic nematodes of the digestive tract remain one of the main constraints to goat production both in temperate and tropical
countries. The usual mode of control of these gastrointestinal nematodes (GIN) based on the repeated use of anthelmintics
is now strongly questioned because of the increasing development of resistance to these molecules. Among the alternative
methods to anthelmintics currently available, the manipulation of host nutrition in order to improve the host resistance and/or
resilience to parasitic infections seems to represent one of the most promising options to reduce the dependence on conventional
chemotherapy and to favour the sustainable control of gastro intestinal nematode infections. This paper will review the available
information on the interactions between nutrition and nematode parasitism in dairy or meat goats both in temperate and tropical
conditions. It will refer to quantitative aspects of the diet (influence of the protein and/or energy parts) as well as to qualitative
components (effects of plant secondary metabolites on worm biology) and will discuss the specificities of goats in regard of
theses interactions
Accretion properties of T Tauri stars in sigma Ori
Accretion disks around young stars evolve in time with time scales of few
million years. We present here a study of the accretion properties of a sample
of 35 stars in the ~3 million year old star-forming region sigma Ori. Of these,
31 are objects with evidence of disks, based on their IR excess emission. We
use near-IR hydrogen recombination lines (Pa_gamma) to measure their mass
accretion rate. We find that the accretion rates are significantly lower in
sigma Ori than in younger regions, such as rho-Oph, consistently with viscous
disk evolution. The He I 1.083 micron line is detected (either in absorption or
in emission) in 72% of the stars with disks, providing evidence of
accretion-powered activity also in very low accretors, where other accretion
indicators dissapear.Comment: Astronomy and Astrophysics, accepte
Intermittent voluntary wheel running promotes resilience to the negative consequences of repeated social defeat in mice
A novel approach to reduce the incidence of substance use disorders is to promote resilience to stress using environmental resources such as physical exercise. In the present study we test the hypothesis that Voluntary Wheel Running (VWR) during adolescence blocks the negative consequences of stress induced by intermittent repeated social defeat (IRSD). Four groups of adolescent male C57BL/6 mice were employed in the experiment; two groups were exposed to VWR (1 h, 3 days/week) from postnatal day (PND) 21 until the first social defeat (PND 47), while the remaining two groups did not have access to activity wheels (controls). On PND 47, 50, 53 and 56 mice, who had performed VWR, were exposed to an episode of social defeat by a resident aggressive mouse (VWR+IRSD group) or allowed to explore an empty cage (VWR+EXPL group). The same procedure was performed with control mice that had not undergone VWR (CONTROL+IRSD and CONTROL+EXPL groups). On PND 57, all the mice performed the Elevated Plus Maze (EPM), Hole-Board, Social Interaction, Tail Suspension and Splash tests. After an interval of 3 weeks, all mice underwent a conditioned place preference (CPP) procedure with 1 mg/kg of cocaine. Exposure to VWR prevented the negative consequences of social stress in the EPM, splash test and CPP, since the VWR+IRSD group did not display anxiety- or depression-like effects or the potentiation of cocaine reward observed in the Control+IRSD group. Our results support the idea that physical exercise promotes resilience to stress and represents an excellent target in drug abuse prevention. © 202
Resilience to the effects of social stress on vulnerability to developing drug addiction
We review the still scarce but growing literature on resilience to the effects of social stress on the rewarding properties of drugs of abuse. We define the concept of resilience and how it is applied to the field of drug addiction research. We also describe the internal and external protective factors associated with resilience, such as individual behavioral traits and social support. We then explain the physiological response to stress and how it is modulated by resilience factors. In the subsequent section, we describe the animal models commonly used in the study of resilience to social stress, and we focus on the effects of chronic social defeat (SD), a kind of stress induced by repeated experience of defeat in an agonistic encounter, on different animal behaviors (depression- and anxiety-like behavior, cognitive impairment and addiction-like symptoms). We then summarize the current knowledge on the neurobiological substrates of resilience derived from studies of resilience to the effects of chronic SD stress on depression- and anxiety-related behaviors in rodents. Finally, we focus on the limited studies carried out to explore resilience to the effects of SD stress on the rewarding properties of drugs of abuse, describing the current state of knowledge and suggesting future research directions
Brief maternal separation inoculates against the effects of social stress on depression-like behavior and cocaine reward in mice
Exposure to intermittent repeated social defeat (IRSD) increases the vulnerability of mice to the rewarding effects of cocaine in the conditioned place preference (CPP) paradigm. According to the “inoculation of stress” hypothesis, a brief period of maternal separation (MS) can provide protection against the negative effects of IRSD. The aim of the present study was to assess whether exposure to a brief episode of MS prevents the subsequent short-term effects of IRSD on depression- and anxiety-like behaviors and to explore its long-term effects on cocaine CPP in mice. Four groups of male C57BL/6 mice were employed; two groups were separated from their mother 6 h on postnatal day (PND) 9], while the other two groups were not (controls). On PND 47, 50, 53 and 56, mice that had experienced MS were exposed to social defeat in the cage of an aggressive resident mouse (MS + IRSD group) or were allowed to explore an empty cage (MS + EXPL group). The same procedure was performed with control mice that had not experienced MS (CONTROL + IRSD and CONTROL + EXPL groups). On PND57-58, all the mice performed the elevated plus maze and the hole-board, social interaction and splash tests. Three weeks after the last episode of defeat, all the mice underwent the CPP procedure with cocaine (1 mg/kg). Irrespective of whether or not MS had taken place, a reduction in open arms measures, dips, and social interaction was observed in mice that experienced IRSD. A higher latency of grooming and acquisition of cocaine-induced CPP were observed only in mice exposed to IRSD alone (CONTROL + IRSD). These results suggest that exposure to a brief episode of stress early in life increases the subsequent resilience of animals to the effects of social stress on vulnerability to cocaine. Copyright © 2022 Calpe-López, Martínez-Caballero, García-Pardo and Aguilar
Resilience to the short- and long-term behavioral effects of intermittent repeated social defeat in adolescent male mice
Background
Exposure to intermittent repeated social defeat (IRSD) increases the sensitivity of mice to the rewarding effects of cocaine in the conditioned place preference (CPP) paradigm. Some animals are resilient to this effect of IRSD, though research exploring this inconsistency in adolescent mice is scarce. Thus, our aim was to characterize the behavioral profile of mice exposed to IRSD during early adolescence and to explore a potential association with resilience to the short- and long-term effects of IRSD.
Methods
Thirty-six male C57BL/6 mice were exposed to IRSD during early adolescence (PND 27, 30, 33 and 36), while another 10 male mice did not undergo stress (controls). Defeated mice and controls then carried out the following battery of behavioral tests; the Elevated Plus Maze, Hole-Board and Social Interaction Test on PND 37, and the Tail Suspension and Splash tests on PND 38. Three weeks later, all the mice were submitted to the CPP paradigm with a low dose of cocaine (1.5 mg/kg).
Results
IRSD during early adolescence induced depressive-like behavior in the Social Interaction and Splash tests and increased the rewarding effects of cocaine. Mice with low levels of submissive behavior during episodes of defeat were resilient to the short- and long-term effects of IRSD. In addition, resilience to the short-term effects of IRSD on social interaction and grooming behavior predicted resilience to the long-term effects of IRSD on cocaine reward.
Conclusion
Our findings help to characterize the nature of resilience to the effects of social stress during adolescence
U-band study of the accretion properties in the sigma Ori star-forming region
This paper presents the results of an U band survey with FORS1/VLT of a large
area in the sigma Orionis star-forming region. We combine the U-band photometry
with literature data to compute accretion luminosity and mass accretion rates
from the U-band excess emission for all objects (187) detected by Spitzer in
the FORS1 field and classified by Hernandez et al. (2007) as likely members of
the cluster. The sample stars range in mass from ~0.06 to ~1.2 Msun; 72 of them
show evidence of disks and we measure mass accretion rates Macc between
<10^{-11} and few 10^{-9} Msun/yr, using the colors of the diskless stars as
photospheric templates. Our results confirm the dependence of Macc on the mass
of the central object, which is stronger for low-mass stars and flattens out
for masses larger than ~0.3 Msun; the spread of Macc for any value of the
stellar mass is ~2 orders of magnitude. We discuss the implications of these
results in the context of disk evolution models. Finally, we analyze the
relation between Macc and the excess emission in the Spitzer bands, and find
that at Macc ~10^{-10} Msun/yr the inner disks change from optically thin to
optically thick.Comment: 19 pages, 17 figures, accepted by A&
The bipolar outflow and disk of the brown dwarf ISO217
We show that the very young brown dwarf candidate ISO217 (M6.25) is driving
an intrinsically asymmetric bipolar outflow with a stronger and slightly faster
red-shifted component based on spectro-astrometry of forbidden [SII] emission
lines observed in UVES/VLT spectra taken in 2009. ISO217 is only one of a
handful of brown dwarfs and VLMS (M5-M8) for which an outflow has been detected
and that show that the T Tauri phase continues at the substellar limit. We
measure a spatial extension of the outflow of +/-190mas (+/-30AU) and
velocities of +/-40-50kms/s. We show that the velocity asymmetry between both
lobes is variable on timescales of a few years and that the strong asymmetry of
a factor of 2 found in 2007 might be smaller than originally anticipated when
using a more realistic stellar rest-velocity. We also detect forbidden
[FeII]7155 emission, for which we propose as potential origin the hot inner
regions of the outflow. To understand the ISO217 system, we determine the disk
properties based on radiative transfer modeling of the SED. This disk model
agrees very well with Herschel/PACS data at 70mu. We find that the disk is
flared and intermediately inclined (~45deg). The total disk mass (4e-6 Msun) is
small compared to the accretion and outflow rate of ISO217 (~1e-10 Msun/yr). We
propose that this discrepancy can be explained by either a higher disk mass
than inferred from the model (strong undetected grain growth) and/or by an on
average lower accretion and outflow rate than the determined values. We show
that a disk inclination significantly exceeding 45deg, as suggested from Halpha
modeling and from both lobes of the outflow being visible, is inconsistent with
the SED data. Thus, despite its intermediate inclination angle, the disk of
this brown dwarf does not appear to obscure the red outflow component, which is
very rarely seen for T Tauri objects (only one other case).Comment: Accepted for publication at A&A; minor changes (language editing
Deep XMM-Newton observation of the Eta Chamaleontis cluster
The members of the Eta Chamaleontis cluster are in an evolutionary stage in
which disks are rapidly evolving. It also presents some peculiarities, such as
the large fraction of binaries and accretion disks, probably related with the
cluster formation process. Its proximity makes this stellar group an ideal
target for studying the relation between X-ray emission and those stellar
parameters. The main objective of this work is to determine general X-ray
properties of the cluster members in terms of coronal temperature, column
density, emission measure, X-ray luminosity and variability. We also aim to
establish the relation between the X-ray luminosity of these stars and other
stellar parameters, such as binarity and presence of accretion disks. A study
of flare energies for each flare event and their relation with some stellar
parameters is also performed. We used proprietary data from a deep XMM-Newton
observation pointed at the core of the Eta Chamaleontis cluster. Specific
software for the reduction of XMM-Newton data was used for the analysis of our
observation. For the detection of sources, we used the wavelet-based code
PWDetect. General coronal properties were derived from plasma model fitting. We
also determined variability of the Eta Chamaleontis members in the EPIC
field-of-view. A total of six flare-like events were clearly detected in five
different stars. For them, we derived coronal properties during the flare
events and pseudo-quiescent state separately. In our observations, stars that
underwent a flare event have higher X-ray luminosities in the pseudo-quiescent
state than cluster members with similar spectral type with no indications of
flaring, independently whether they have an accretion disk or not. Observed
flare energies are typical of both pre-main and main-sequence M stars. We
detected no difference between flare energies of stars with and without an
accretion disk.Comment: Accepted for publication in Astronomy and Astrophysics. 12 pages, 30
individual figure
Chicamocha Canyon Geopark project: A novel strategy for the socio-economic development of Santander (Colombia) through geoeducation, geotourism and geoconservation
The proposed Chicamocha Canyon Geopark project is starting its way for nomination as a UNESCO Global Geopark under the recognition of the Global Geoparks Network. This paper aims to present the justifications of establishing this geopark. It also assesses the potential role of a geopark figure in Santander as an urgent measure to promote the geoconservation of the Chicamocha Canyon territory. The success of this project will not only improve the living conditions of local communities, but also will be a reference model in terms of geological conservation at national and international level. The Chicamocha Canyon, where is proposed to develop this project, has a great potential for the development of the tourism industry due to climatic conditions of the region, besides possessing a rich cultural and natural heritage that needs to be enhanced and protected. Undoubtedly, this initiative should satisfy all the requirements to be a UNESCO Global Geopark, which include a delimited area that defines a territory, the occurrence of geological features of international importance with scientific, educational and aesthetic value, the presence of other types of heritage such as archaeological sites, as well as a proper access infrastructure that favors the socio-economic development of the region. In order to guarantee the successful consolidation of the proposed geopark within the defined territory, this initiative must count the strong support of the local communities and must involve stakeholders such as government authorities, academic and research institutions, and local businesses
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