28 research outputs found
Effects of Acute Low-Intensity Cycling on Perceived Stress, Arousal, and Attention
Generally, acute bouts of aerobic exercise have been shown to enhance psychological measures of emotion, mood, and affect. Previous investigations suggest that perceived stress and arousal levels are especially influenced by exercise. Interestingly, very few studies have examined the influence of exercise on attention and whether changes in stress and arousal may augment adaptations in attentional orientation that are often required during exercise. Furthermore, very little is known about the timing of the effects of exercise on these psychological outcomes. PURPOSE: The primary purpose of this study was to examine the effects of low-intensity aerobic exercise on stress, arousal, and attention. A secondary aim was to evaluate the time-course effects of exercise on stress, arousal, and attention. METHODS: Twenty (Mage = 23.2 ± 3.1 years old) college-aged individuals were counterbalanced into low-intensity exercise (LI) and seated control (SC) conditions. During each condition, participants completed a 10-minute resting baseline period, 20 minutes of either sustained cycling or seated rest, and a 20-minute recovery period. Primary outcomes of stress, arousal, and attention were assessed at 10-minute intervals throughout each condition via a Visual Analog Scale for Stress (VAS-S), Felt Arousal Scale (FAS), and Attentional Focus Scale (AFS), respectively. RESULTS: For the VAS-S, a Time main effect was revealed, F(4,16) = 5.76, p = .005, suggesting general reductions in stress following both LI and SC conditions. A Time main effect was also found for the FAS, which was superseded by a Condition x Time interaction, F(4,16) = 3.08, p = .047, indicating a greater increase in arousal levels during the LI condition compared to the SC condition. Lastly, a Time main effect for the AFS was found, F(4,16) = 3.05, p = .049, indicating general shifts from internal to external focus during each condition. CONCLUSION: Taken together, the current results suggest that exercise at lower doses (i.e., low-intensity for 20 minutes) may have minimal influence on more complex psychological perceptions of stress and attention. These results may help us better understand the complicated interactions between common psychological measures used in exercise science research. Additionally, this study may aid in the development of appropriate exercise prescriptions for populations looking to specifically target stress, arousal, and attention
Stromal senescence establishes an immunosuppressive microenvironment that drives tumorigenesis
Age is a significant risk factor for the development of cancer. However, the mechanisms that drive age-related increases in cancer remain poorly understood. To determine if senescent stromal cells influence tumorigenesis, we develop a mouse model that mimics the aged skin microenvironment. Using this model, here we find that senescent stromal cells are sufficient to drive localized increases in suppressive myeloid cells that contributed to tumour promotion. Further, we find that the stromal-derived senescence-associated secretory phenotype factor interleukin-6 orchestrates both increases in suppressive myeloid cells and their ability to inhibit anti-tumour T-cell responses. Significantly, in aged, cancer-free individuals, we find similar increases in immune cells that also localize near senescent stromal cells. This work provides evidence that the accumulation of senescent stromal cells is sufficient to establish a tumour-permissive, chronic inflammatory microenvironment that can shelter incipient tumour cells, thus allowing them to proliferate and progress unabated by the immune system
Galaxy Pairs in the Sloan Digital Sky Survey - III: Evidence of Induced Star Formation from Optical Colours
We have assembled a large, high quality catalogue of galaxy colours from the
Sloan Digital Sky Survey Data Release 7, and have identified 21,347 galaxies in
pairs spanning a range of projected separations (r_p < 80 h_{70}^{-1} kpc),
relative velocities (\Delta v < 10,000 km/s, which includes projected pairs
that are essential for quality control), and stellar mass ratios (from 1:10 to
10:1). We find that the red fraction of galaxies in pairs is higher than that
of a control sample matched in stellar mass and redshift, and demonstrate that
this difference is likely due to the fact that galaxy pairs reside in higher
density environments than non-paired galaxies. We detect clear signs of
interaction-induced star formation within the blue galaxies in pairs, as
evidenced by a higher fraction of extremely blue galaxies, along with blueward
offsets between the colours of paired versus control galaxies. These signs are
strongest in close pairs (r_p < 30 h_{70}^{-1} kpc and \Delta v < 200 km/s),
diminish for more widely separated pairs (r_p > 60 h_{70}^{-1} kpc and \Delta v
< 200 km/s) and disappear for close projected pairs (r_p < 30 h_{70}^{-1} kpc
and \Delta v > 3000 km/s). These effects are also stronger in central (fibre)
colours than in global colours, and are found primarily in low- to
medium-density environments. Conversely, no such trends are seen in red
galaxies, apart from a small reddening at small separations which may result
from residual errors with photometry in crowded fields. When interpreted in
conjunction with a simple model of induced starbursts, these results are
consistent with a scenario in which close peri-centre passages trigger induced
star formation in the centres of galaxies which are sufficiently gas rich,
after which time the galaxies gradually redden as they separate and their
starbursts age.Comment: 17 pages. Accepted for publication in MNRA
What turns galaxies off? The different morphologies of star-forming and quiescent galaxies since z~2 from CANDELS
We use HST/WFC3 imaging from the CANDELS Multicycle Treasury Survey, in
conjunction with the Sloan Digital Sky Survey, to explore the evolution of
galactic structure for galaxies with stellar masses >3e10M_sun from z=2.2 to
the present epoch, a time span of 10Gyr. We explore the relationship between
rest-frame optical color, stellar mass, star formation activity and galaxy
structure. We confirm the dramatic increase from z=2.2 to the present day in
the number density of non-star-forming galaxies above 3e10M_sun reported by
others. We further find that the vast majority of these quiescent systems have
concentrated light profiles, as parametrized by the Sersic index, and the
population of concentrated galaxies grows similarly rapidly. We examine the
joint distribution of star formation activity, Sersic index, stellar mass,
inferred velocity dispersion, and stellar surface density. Quiescence
correlates poorly with stellar mass at all z<2.2. Quiescence correlates well
with Sersic index at all redshifts. Quiescence correlates well with `velocity
dispersion' and stellar surface density at z>1.3, and somewhat less well at
lower redshifts. Yet, there is significant scatter between quiescence and
galaxy structure: while the vast majority of quiescent galaxies have prominent
bulges, many of them have significant disks, and a number of bulge-dominated
galaxies have significant star formation. Noting the rarity of quiescent
galaxies without prominent bulges, we argue that a prominent bulge (and
perhaps, by association, a supermassive black hole) is an important condition
for quenching star formation on galactic scales over the last 10Gyr, in
qualitative agreement with the AGN feedback paradigm.Comment: The Astrophysical Journal, in press; 20 pages with 13 figure
A BODIPY-embedding miltefosine analog linked to cell-penetrating Tat(48-60) peptide favors intracellular delivery and visualization of the antiparasitic drug
Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.
Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field
The Evolution of Star Formation Histories of Quiescent Galaxies
Although there has been much progress in understanding how galaxies evolve,
we still do not understand how and when they stop forming stars and become
quiescent. We address this by applying our galaxy spectral energy distribution
models, which incorporate physically motivated star formation histories (SFHs)
from cosmological simulations, to a sample of quiescent galaxies at
. A total of 845 quiescent galaxies with multi-band photometry
spanning rest-frame ultraviolet through near-infrared wavelengths are selected
from the CANDELS dataset. We compute median SFHs of these galaxies in bins of
stellar mass and redshift. At all redshifts and stellar masses, the median SFHs
rise, reach a peak, and then decline to reach quiescence. At high redshift, we
find that the rise and decline are fast, as expected because the Universe is
young. At low redshift, the duration of these phases depends strongly on
stellar mass. Low-mass galaxies () grow on
average slowly, take a long time to reach their peak of star formation
( Gyr), and the declining phase is fast ( Gyr).
Conversely, high-mass galaxies () grow on
average fast ( Gyr), and, after reaching their peak, decrease the
star formation slowly ( Gyr). These findings are consistent with
galaxy stellar mass being a driving factor in determining how evolved galaxies
are, with high-mass galaxies being the most evolved at any time (i.e.,
downsizing). The different durations we observe in the declining phases also
suggest that low- and high-mass galaxies experience different quenching
mechanisms that operate on different timescales.Comment: 16 pages, 10 figures, resubmitted to ApJ after addressing the
Referee's comment
Listeria pathogenesis and molecular virulence determinants
The gram-positive bacterium Listeria monocytogenes is the causative agent of listeriosis, a highly fatal opportunistic foodborne infection. Pregnant women, neonates, the elderly, and debilitated or immunocompromised patients in general are predominantly affected, although the disease can also develop in normal individuals. Clinical manifestations of invasive listeriosis are usually severe and include abortion, sepsis, and meningoencephalitis. Listeriosis can also manifest as a febrile gastroenteritis syndrome. In addition to humans, L. monocytogenes affects many vertebrate species, including birds. Listeria ivanovii, a second pathogenic species of the genus, is specific for ruminants. Our current view of the pathophysiology of listeriosis derives largely from studies with the mouse infection model. Pathogenic listeriae enter the host primarily through the intestine. The liver is thought to be their first target organ after intestinal translocation. In the liver, listeriae actively multiply until the infection is controlled by a cell-mediated immune response. This initial, subclinical step of listeriosis is thought to be common due to the frequent presence of pathogenic L. monocytogenes in food. In normal indivuals, the continual exposure to listerial antigens probably contributes to the maintenance of anti-Listeria memory T cells. However, in debilitated and immunocompromised patients, the unrestricted proliferation of listeriae in the liver may result in prolonged low-level bacteremia, leading to invasion of the preferred secondary target organs (the brain and the gravid uterus) and to overt clinical disease. L. monocytogenes and L. ivanovii are facultative intracellular parasites able to survive in macrophages and to invade a variety of normally nonphagocytic cells, such as epithelial cells, hepatocytes, and endothelial cells. In all these cell types, pathogenic listeriae go through an intracellular life cycle involving early escape from the phagocytic vacuole, rapid intracytoplasmic multiplication, bacterially induced actin-based motility, and direct spread to neighboring cells, in which they reinitiate the cycle. In this way, listeriae disseminate in host tissues sheltered from the humoral arm of the immune system. Over the last 15 years, a number of virulence factors involved in key steps of this intracellular life cycle have been identified. This review describes in detail the molecular determinants of Listeria virulence and their mechanism of action and summarizes the current knowledge on the pathophysiology of listeriosis and the cell biology and host cell responses to Listeria infection. This article provides an updated perspective of the development of our understanding of Listeria pathogenesis from the first molecular genetic analyses of virulence mechanisms reported in 1985 until the start of the genomic era of Listeria research
Low-dose cyclosporin nephrotoxicity in the rat
The nephrotoxicity of cyclosporin (CsA) continues to be a clinical problem that detracts from its obvious benefits as an immunosuppressive agent. Animal models designed to study the problem have generally relied either on chronic administration of high doses of the drug or acute administration of single i.v. doses. The present study establishes a model of CsA nephrotoxicity using doses of the drug comparable to those used in man administered over a time period sufficient for haemodynamic and structural changes to become evident.
The technique used measures glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) by the plasma clearance of chromium EDTA and iodohippuran respectively. This has the advantage of allowing sequential measurements in individual animals.
Significant impairment of GFR was seen in animals treated intraperitoneally with doses of CsA as low as 5 mg/kg/day. CsA 7.5 mg/kg/day caused a significant reduction in ERPF, and at 10 mg/kg/day and greater filtration fraction also declined significantly. Detailed histological examination of the kidneys from these animals also revealed significant tubular dilatation at 10 mg/kg/day and above.
This model of CsA toxicity circumvents many of the problems associated with other models. The animals can be studied longitudinally and the period of administration has relevance to clinic practice. This work provides the basis for further studies which can closely mimic the clinical situation using doses similar to those used for human maintenance immunosuppression