1,028 research outputs found
Development of an improved gaseous oxygen impact test system Final report, 10 Jun. 1969 - 10 May 1970
Improved gaseous oxygen impact test system development and consultative service
sAC as a model for understanding the impact of endosymbiosis on cell signaling
AbstractAs signaling pathways evolve, selection for new functions guides the co-option of existing material. Major transitions in the history of life, including the evolution of eukaryotes and multicellularity, exemplify this process. These transitions provided both strong selection and a plenitude of available material for the evolution of signaling pathways. Mechanisms that evolved to mediate conflict during the evolution of eukaryotes may subsequently have been co-opted during the many independent derivations of multicellularity. The soluble adenylyl cyclase (sAC) signaling pathway illustrates this hypothesis. Class III adenylyl cyclases, which include sAC, are found in bacteria, including the Ī±-proteobacteria. These adenylyl cyclases are the only ones present in eukaryotes but appear to be absent in archaeans. This pattern suggests that the mitochondrial endosymbiosis brought sAC signaling to eukaryotes as part of an intact module. After transfer to the proto-nuclear genome, this module was then co-opted into numerous new functions. In the evolution of eukaryotes, sAC signaling may have mediated conflicts by maintaining metabolic homeostasis. In the evolution of multicellularity, in different lineages sAC may have been co-opted into parallel tasks originally related to conflict mediation. Elucidating the history of the sAC pathway may be relatively straightforward because it is ubiquitous and linked to near universal metabolic by-products (CO2/HCO3ā). Other signaling pathways (e.g., those involving STAT and VEGF) present a greater challenge but may suggest a complementary pattern. The impact of the mitochondrial endosymbiosis on cell signaling may thus have been profound. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease
A New Look at Some Old Animals
How the tiny marine animalTrichoplax adhaerens is related to other animals has long puzzled researchers studying the origin of metazoans. An ambitious "total evidence" study provides careful analysis of this question and reveals some surprises
Reactive Oxygen Species and the Regulation of Hyperproliferation in a Colonial Hydroid
Colonies of Podocoryna carnea circulate gastrovascular fluid
among polyps via tubelike stolons. At polyp-stolon junctions,
mitochondrion-rich cells in part regulate this gastrovascular
flow. During competition, colonies hyperproliferate nematocytes
and stolons; nematocysts are discharged until one colony
is killed. Hyperproliferation then ceases, and normal growth
resumes. Here, competing colonies were treated with azide,
which inhibits respiration and upregulates reactive oxygen species
(ROS). After the cessation of competition, azide-treated
colonies continued to hyperproliferate. In azide-treated competing
colonies, however, mitochondrion-rich cells were found
to produce similar amounts of ROS as those in untreated competing
colonies. Subsequent experiments showed that both
azide treatment and competition diminished the lumen widths
at polyp-stolon junctions, where mitochondrion-rich cells are
found. In competing colonies, these diminished widths may
also diminish the metabolic demand on these cells, causing
mitochondria to enter the resting state and emit more ROS.
Indeed, results with two fluorescent probes show that mitochondrion-
rich cells in competing colonies produce more ROS
than those in noncompeting colonies. In sum, these results
suggest that competition perturbs the usual activity of mitochondrion-
rich cells, altering their redox state and increasing
ROS formation. Via uncharacterized pathways, these ROS may
contribute to hyperproliferation
Competing risks after coronary bypass surgeryThe influence of death on reintervention
AbstractObjective: For groups of patients at high risk of death, such as older patients, the actual probability of experiencing a nonfatal event, such as reintervention, must be far smaller than the potential probability were there no attrition by death. Competing risks analysis quantifies the difference. Methods: Multivariable analyses were performed for the competing events death before reintervention, reoperation, and percutaneous transluminal coronary angioplasty in 2001 patients after bilateral internal thoracic artery grafting and in 8123 after single internal thoracic artery grafting. Follow-up was 9.7 Ā± 3.0 years and 10.8 Ā± 5.2 years in bilateral and single internal thoracic artery groups, respectively. Results: Patients receiving single grafts experienced shorter survival and more reinterventions (P < .0001). However, other risk factors for death included old age (P < .0001), but risk factors for reintervention included young age (P < .0001). This difference confounds interpretation of event-free survival that is clarified by competing risks analysis. Death reduced the potential benefit of bilateral internal thoracic artery grafting on reintervention by angioplasty from a median of 8.5% to 5.5% at 12 years and by reoperation from 9.3% to 6.8%, with progressively greater erosion of benefit from attrition by death as age increased. Competing risks simulation confirmed that young age was a true risk factor for reintervention, excluding the explanation that it reflected simply passive attrition by death as patients age. Conclusions: Even after accounting for attrition by interim deaths, bilateral versus single internal thoracic artery grafting and older age are associated with fewer reinterventions. However, in high-risk patients, its benefit on freedom from reintervention is eroded considerably by death. (J Thorac Cardiovasc Surg 2000;119:1221-32
Application of the ERTS system to the study of Wyoming resources with emphasis on the use of basic data products
Many potential users of ERTS data products and other aircraft and satellite imagery are limited to visual methods of analyses of these products. Illustrations are presented from Wyoming studies that have employed these standard data products for a variety of geologic and related studies. Possible economic applications of these studies are summarized. Studies include regional geologic mapping for updating and correcting existing maps and to supplement incomplete regional mapping; illustrations of the value of seasonal images in geologic mapping; specialized mapping of such features as sand dunes, playa lakes, lineaments, glacial features, regional facies changes, and their possible economic value; and multilevel sensing as an aid in mineral exploration. Examples of cooperative studies involving botanists, plant scientists, and geologists for the preparation of maps of surface resources that can be used by planners and for environmental impact studies are given
Physiological Characterization of Stolon Regression in a Colonial Hydroid
As with many colonial animals, hydractiniid hydroids display a range of morphological variation. Sheet-like forms exhibit feeding
polyps close together with short connecting stolons, whereas runner-like forms have more distant polyps and longer connecting
stolons. These morphological patterns are thought to derive from rates of stolon growth and polyp formation. Here, stolon
regression is identified and characterized as a potential process underlying this variation. Typically, regression can be observed
in a few stolons of a normally growing colony. For detailed studies, many stolons of a colony can be induced to regress by
pharmacological manipulations of reactive oxygen species (e.g. hydrogen peroxide) or reactive nitrogen species (e.g. nitric
oxide). The regression process begins with a cessation of gastrovascular flow to the distal part of the stolon. High levels of
endogenous H2O2 and NO then accumulate in the regressing stolon. Remarkably, exogenous treatments with either H2O2 or an NO
donor equivalently trigger endogenous formation of both H2O2 and NO. Cell death during regression is suggested by both
morphological features, detected by transmission electron microscopy, and DNA fragmentation, detected by TUNEL. Stolon
regression may occur when colonies detect environmental signals that favor continued growth in the same location rather than
outward growth
Association of educational status with heart rate recovery: a population-based propensity analysis
Redox Signaling in Colonial Hydroids: Many Pathways for Peroxide
Studies of mitochondrial redox signaling predict that
the colonial hydroids Eirene viridula and Podocoryna
carnea should respond to manipulations of reactive oxygen
species (ROS). Both species encrust surfaces with feeding
polyps connected by networks of stolons; P. carnea is more
āsheet-likeā with closely spaced polyps and short stolons,
while E. viridula is more ārunner-likeā with widely spaced
polyps and long stolons. Treatment with the chemical antioxidant
vitamin C diminishes ROS in mitochondrion-rich
epitheliomuscular cells (EMCs) and produces phenotypic
effects (sheet-like growth) similar to uncouplers of
oxidative phosphorylation. In peripheral stolon tips,
treatment with vitamin C triggers a dramatic increase of
ROS that is followed by tissue death and stolon regression.
The enzymatic anti-oxidant catalase is probably not taken
up by the colony but, rather, converts hydrogen peroxide
in the medium to water and oxygen. Exogenous catalase
does not affect ROS in mitochondrion-rich EMCs, but
does increase the amounts of ROS emitted from
peripheral stolons, resulting in rapid, runner-like growth.
Treatment with exogenous hydrogen peroxide increases
ROS levels in stolon tips and results in somewhat faster
colony growth. Finally, untreated colonies of E. viridula
exhibit higher levels of ROS in stolon tips than untreated
colonies of P. carnea. ROS may participate in a number of
putative signaling pathways: (1) high levels of ROS may
trigger cell and tissue death in peripheral stolon tips; (2)
more moderate levels of ROS in stolon tips may trigger
outward growth, inhibit branching and, possibly, mediate
the redox signaling of mitochondrion-rich EMCs; and (3)
ROS may have an extra-colony function, perhaps in
suppressing the growth of bacteria
Moving beyond the single disciplines: Building a scholarship of engagement that permeates higher education.
Communities face complex problems that are best addressed by integrating the perspectives of multiple disciplines, yet many forms of engaged scholarship remain disciplinarily specific. Universities struggle to bring together highly disparate disciplines linking knowledge with action to address community problems. Sustainability is an important example of a complex, urgent problem that is best addressed by integrating multiple disciplines. In the United States, a unique multi-year initiative, Maineās Sustainability Solutions Initiative (SSI), addresses sustainability problems by working across disciplines on engaged research. Scholars, representing multiple disciplines and most of the higher education institutions in the state, working with their community partners, are addressing sustainability problems related to landscape change, specifically urbanization, forest ecosystem management, and climate change. This initiative is composed of over two dozen interdisciplinary, engaged research projects that include diverse stakeholders (e.g., nongovernmental organizations, communities, policy organizations, and governmental leaders) as members of the research teams. Reflecting on the challenges of involving multiple disciplines in research projects, we discuss SSI as an exemplar of interdisciplinary, engaged campus initiatives. The scale and reach of the initiative (on-campus and statewide), the number of disciplines and stakeholders involved in the project, and the conversations around engaged scholarship occurring at the University of Maine capture the challenges and opportunities of moving the scholarship of engagement beyond the isolated work of individual disciplines
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