827 research outputs found
Growth and development of larval bay scallops (Argopecten irradians) in response to early exposure to high CO2
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013Coastal
and
estuarine
environments
experience
large
variability
and
rapid
shifts
in
pCO2
levels.
Elevated
pCO2,
or
ocean
acidification,
often
negatively
affects
early
life
stages
of
calcifying
marine
invertebrates,
including
bivalves,
but
it
is
unclear
which
developmental
stage
is
most
sensitive.
I
hypothesized
that
initial
calcification
is
a
critical
stage
during
which
high
pCO2
exposure
has
severe
effects
on
larval
growth
and
development
of
bay
scallop
(Argopecten
irradians).
Using
five
experiments
varying
the
timing
of
exposure
of
embryonic
and
larval
bay
scallops
to
high
CO2,
this
thesis
identifies
two
distinct
stages
of
development
during
which
exposure
to
high
CO2/low
pH
causes
different
effects
on
bay
scallop
larvae.
I
show
that
any
exposure
to
high
CO2
consistently
reduces
survival
of
bay
scallop
larvae.
I
also
show
that
high
CO2
exposure
during
initial
calcification
(12-24
h
post-fertilization)
results
in
significantly
smaller
shells,
relative
to
ambient
conditions,
and
this
size
decrease
persists
through
the
first
week
of
development.
High
CO2
exposure
at
2-12
h
post-Â
fertilization
(pre-calcification),
does
not
impact
shell
size,
suggesting
that
the
CO2
impact
on
size
is
a
consequence
of
water
chemistry
during
calcification.
However,
high
CO2
exposure
prior
to
shell
formation
(2-12
h
post-fertilization)
causes
a
high
incidence
of
larval
shell
deformity,
regardless
of
CO2
conditions
during
initial
calcification.
This
impact
does
not
occur
in
response
to
high
CO2
exposure
after
the
2-12
h
period.
The
observations
of
two
critical
stages
in
early
development
has
implications
for
both
field
and
hatchery
populations.
If
field
populations
were
able
to
time
their
spawning
to
occur
during
the
night,
larvae
would
undergo
initial
calcification
during
the
daytime,
when
CO2
conditions
are
more
favorable,
resulting
in
larger
veliger
larvae.
Hatcheries
could
invest
minimal
resources
to
monitor
and
modify
water
chemistry
only
during
the
first
day
of
development
to
ensure
larva
are
exposed
to
favorable
conditions
during
that
critical
period.This
work
was
funded
by
a
National
Defense
Science
and
Engineering
Graduate
Fellowship
the
WHOI
Academic
Programs
Office;
NSF
grant
OCE-Â0326734
to
L.
Mullineaux,
H.
Caswell,
C.
Dibacco,
J.
Lerczak,
S.
Thorrold,
and
M.
Neubert;
a
Woods
Hole
Oceanographic
Institution
Interdisciplinary
Award
to
L.
Mullineaux
and
D.
McCorkle;
and
awards
to
L.
Mullineaux
and
M.
White,
to
D.
McCorkle,
and
to
A.
Cohen
and
D.
McCorkle
through
NOAA
Sea
Grant
#NA10OAR4170083.
White
received
additional
funding
from
WHOI’s
Coastal
Ocean
Institute
Student
Research
Funds
and
Woods
Hole
Sea
Grant
New
Initiative
Funds
Early exposure of bay scallops (Argopecten irradians) to high CO2 causes a decrease in larval shell growth
© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e61065, doi:10.1371/journal.pone.0061065.Ocean acidification, characterized by elevated pCO2 and the associated decreases in seawater pH and calcium carbonate saturation state (Ω), has a variable impact on the growth and survival of marine invertebrates. Larval stages are thought to be particularly vulnerable to environmental stressors, and negative impacts of ocean acidification have been seen on fertilization as well as on embryonic, larval, and juvenile development and growth of bivalve molluscs. We investigated the effects of high CO2 exposure (resulting in pH = 7.39, Ωar = 0.74) on the larvae of the bay scallop Argopecten irradians from 12 h to 7 d old, including a switch from high CO2 to ambient CO2 conditions (pH = 7.93, Ωar = 2.26) after 3 d, to assess the possibility of persistent effects of early exposure. The survival of larvae in the high CO2 treatment was consistently lower than the survival of larvae in ambient conditions, and was already significantly lower at 1 d. Likewise, the shell length of larvae in the high CO2 treatment was significantly smaller than larvae in the ambient conditions throughout the experiment and by 7 d, was reduced by 11.5%. This study also demonstrates that the size effects of short-term exposure to high CO2 are still detectable after 7 d of larval development; the shells of larvae exposed to high CO2 for the first 3 d of development and subsequently exposed to ambient CO2 were not significantly different in size at 3 and 7 d than the shells of larvae exposed to high CO2 throughout the experiment.This work was funded by a Woods Hole Oceanographic Institution Interdisciplinary Award to Mullineaux & McCorkle; and awards to Mullineaux & White, to McCorkle, and to Cohen & McCorkle through NOAA (National Oceanic and Admosphereic Administration) Sea Grant #NA10OAR4170083. White was funded through a National Defense Science and Engineering Graduate Fellowship through the American Society for Engineering Education
Community Science in Support of Ecosystem-Based Management: A Case Study from the Damariscotta River Estuary, Maine, USA
Coastal marine ecosystems are dynamic social-ecological systems (SESs) that support diverse ecosystem services and human activities. The complexity of SESs means that ecosystem-based approaches are increasingly used to support coastal marine ecosystem stewardship. We report how a community science program in Maine, USA offers a model of organizational innovation to expand capacities for shellfish research and management. Since 2019, we have collaborated with local students, shellfish harvesters, and others in data collection, interpretation, and application, contributing to local shellfish management and ecosystem sustainability. We demonstrate how community-based social and ecological research can build adaptive capacities by centering local knowledge; generating long-term and fine-scale datasets; supporting community-led management and civic engagement; and contributing to field methods that people with varied lived experiences and training can implement in a sustainable fashion. Our approach can be adapted to other contexts, particularly in data-limited SESs that are experiencing observable social and ecological change
Measuring ecosystem services from soil health. Vermont Payment for Ecosystem Services Technical Research Report #1
There are a multitude of approaches to evaluating soil health and the soil processes influenced by soil health. As the state of Vermont explores innovative programs that compensate farmers for soil health and associated ecosystem services, the selection of soil health indicators and quantification methods is a foundational first step that influences other aspects of program design. What is measured determines the ecosystem services that can be inferred, the accuracy of data that informs decisions, and programmatic transaction costs. Simply put, what is measured matters. The PES Working Group identified organic matter, bulk density, aggregate stability, greenhouse gas flux from the soil surface and soil biodiversity as the soil health indicators that would be most closely related to the desired ecosystem services, and contracted with UVM to provide more information on the measurement considerations for these indicators.
In this report, the available methods and costs of measurement for these soil health indicators are discussed in detail. In addition, modeling options are identified. Finally an index that could combine multiple soil health indicators is explored as an option. Overall, this foundational research identified the need for the PES program to integrate both soil health measurements with modeling to validate soil health. Costs for laboratory analysis and labor for these selected metrics were approximately $250 per field, and we identified three analytical laboratories that could provide the soil health analysis.
The contents of this report are intended to support decision-making on the part of the Vermont Soil Health and Payment for Ecosystem Services Working Group about what will be measured in a PES, but do not constrain the group from adding other metrics should they so desire. This decision must balance accuracy and complexity with the cost of measuring the best indicators of performance. These decisions are foundational to other aspects of PES program design
The Relationship Between Intermittent Limit Cycles and Postural Instability Associated with Parkinson’s Disease
Background: Many disease-specifc factors such as muscular weakness, increased muscle stiffness, varying postural strategies, and changes in postural refexes have been shown to lead to postural instability and fall risk in people with Parkinson’s disease (PD). Recently, analytical techniques, inspired by the dynamical systems perspective on movement control and coordination, have been used to examine the mechanisms underlying the dynamics of postural declines and the emergence of postural instabilities in people with PD. Methods: A wavelet-based technique was used to identify limit cycle oscillations (LCOs) in the anterior–posterior (AP) postural sway of people with mild PD (n = 10) compared to age-matched controls (n = 10). Participants stood on a foam and on a rigid surface while completing a dual task (speaking). Results: There was no signifcant difference in the root mean square of center of pressure between groups. Three out of 10 participants with PD demonstrated LCOs on the foam surface, while none in the control group demonstrated LCOs. An inverted pendulum model of bipedal stance was used to demonstrate that LCOs occur due to disease-specifc changes associated with PD: time-delay and neuromuscular feedback gain. Conclusion: Overall, the LCO analysis and mathematical model appear to capture the subtle postural instabilities associated with mild PD. In addition, these fndings provide insights into the mechanisms that lead to the emergence of unstable posture in patients with PD
Respiratory treatment history predicts suck pattern stability in preterm infants
Sensory deprivation and motor restriction associated with extensive oxygen therapy may lead to poor oromotor control in preterm infants. Non-nutritive suck is one of the first complex oromotor behaviors infants perform. This study determined the spatiotemporal variability of non-nutritive suck (NNS) pressure trajectories in three preterm groups with differing oxygen histories—one control group with minimal or no O2 therapy, and two Respiratory Distress Syndrome (RDS) groups with either a mild/moderate (RDS1) or moderate/severe (RDS2) O2 history. The Non-nutritive Suck Spatiotemporal Index (NNS STI) quantifies spatial and temporal variability across kinematic trajectories, and was calculated from digital representations of infants’ suck pressure signals. An ANCOVA revealed a significant effect for group (p \u3c .001) on the NNS STI measure, with RDS2 infants showing highly variable NNS patterning, and thus relatively underdeveloped suck. Extensive oxygen therapy, which alters the oral sensory environment and reduces motor experiences, disrupts the development of coordinated NNS in preterm infants
A Spatially Resolved Inner Hole in the Disk around GM Aurigae
We present 0.3 arcsec resolution observations of the disk around GM Aurigae
with the Submillimeter Array (SMA) at a wavelength of 860 um and with the
Plateau de Bure Interferometer at a wavelength of 1.3 mm. These observations
probe the distribution of disk material on spatial scales commensurate with the
size of the inner hole predicted by models of the spectral energy distribution.
The data clearly indicate a sharp decrease in millimeter optical depth at the
disk center, consistent with a deficit of material at distances less than ~20
AU from the star. We refine the accretion disk model of Calvet et al. (2005)
based on the unresolved spectral energy distribution (SED) and demonstrate that
it reproduces well the spatially resolved millimeter continuum data at both
available wavelengths. We also present complementary SMA observations of CO
J=3-2 and J=2-1 emission from the disk at 2" resolution. The observed CO
morphology is consistent with the continuum model prediction, with two
significant deviations: (1) the emission displays a larger CO J=3-2/J=2-1 line
ratio than predicted, which may indicate additional heating of gas in the upper
disk layers; and (2) the position angle of the kinematic rotation pattern
differs by 11 +/- 2 degrees from that measured at smaller scales from the dust
continuum, which may indicate the presence of a warp. We note that
photoevaporation, grain growth, and binarity are unlikely mechanisms for
inducing the observed sharp decrease in opacity or surface density at the disk
center. The inner hole plausibly results from the dynamical influence of a
planet on the disk material. Warping induced by a planet could also potentially
explain the difference in position angle between the continuum and CO data
sets.Comment: 12 pages, 6 figures, accepted for publication in Ap
The Role of the CD4 Receptor versus HIV Coreceptors in Envelope-Mediated Apoptosis in Peripheral Blood Mononuclear Cells
AbstractWe examined the role of CD4, CXCR4, and CCR5 in HIV envelope-mediated apoptosis by measuring the response of activated PBMCs to recombinant envelope proteins derived from CXCR4- and CCR5-utilizing viruses. Apoptosis of T cells was assessed by annexin-V staining and TdT-mediated dUTP-biotin nick-end labeling. Treatment of CCR5Δ32 homozygote PBMCs with a CCR5-specific envelope induced apoptosis in T cells, demonstrating that envelope–CD4 interactions are sufficient to induce apoptosis. However, a CXCR4-specific envelope induced higher levels of apoptosis than a CCR5-specific envelope, suggesting that envelope-mediated apoptosis can be enhanced by envelope–CXCR4 interactions. We conclude that envelope can induce apoptosis in T cells independently of the coreceptor specificity of a given envelope, or the expression profile of CXCR4 or CCR5 on a target cell. However, envelope–coreceptor interactions, and in particular, envelope–CXCR4 interactions, can contribute to this process
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A point mutation decouples the lipid transfer activities of microsomal triglyceride transfer protein.
Funder: G. Harold and Leila Y. Mathers Charitable Foundation; funder-id: http://dx.doi.org/10.13039/100001229Apolipoprotein B-containing lipoproteins (B-lps) are essential for the transport of hydrophobic dietary and endogenous lipids through the circulation in vertebrates. Zebrafish embryos produce large numbers of B-lps in the yolk syncytial layer (YSL) to move lipids from yolk to growing tissues. Disruptions in B-lp production perturb yolk morphology, readily allowing for visual identification of mutants with altered B-lp metabolism. Here we report the discovery of a missense mutation in microsomal triglyceride transfer protein (Mtp), a protein that is essential for B-lp production. This mutation of a conserved glycine residue to valine (zebrafish G863V, human G865V) reduces B-lp production and results in yolk opacity due to aberrant accumulation of cytoplasmic lipid droplets in the YSL. However, this phenotype is milder than that of the previously reported L475P stalactite (stl) mutation. MTP transfers lipids, including triglycerides and phospholipids, to apolipoprotein B in the ER for B-lp assembly. In vitro lipid transfer assays reveal that while both MTP mutations eliminate triglyceride transfer activity, the G863V mutant protein unexpectedly retains ~80% of phospholipid transfer activity. This residual phospholipid transfer activity of the G863V mttp mutant protein is sufficient to support the secretion of small B-lps, which prevents intestinal fat malabsorption and growth defects observed in the mttpstl/stl mutant zebrafish. Modeling based on the recent crystal structure of the heterodimeric human MTP complex suggests the G865V mutation may block triglyceride entry into the lipid-binding cavity. Together, these data argue that selective inhibition of MTP triglyceride transfer activity may be a feasible therapeutic approach to treat dyslipidemia and provide structural insight for drug design. These data also highlight the power of yolk transport studies to identify proteins critical for B-lp biology
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