173 research outputs found
Placental morphology and the cellular brain in mammalian evolution
A major focus of evolutionary neurobiology has been on whether different regions of the eutherian
brain evolve in concert, and how free the brain is to evolve independently of body plans. Since the
eutherian brain is loosely modularized, such that one region is rarely isolated for specialization at the
expense of others, but the design of modularization itself can be adapted by tweaking developmental
programs, the degree to which brain regions must evolve in concert and can evolve independently may
carry a deep phylogenetic signal. Using data collected from preserved brain tissue of 37 primate, 21
carnivore, and 15 other eutherian species (spanning 11 orders), I examined the phylogenetic level at
which the proliferation of neurons and glia in the primary visual cortex and hippocampus proper, as
well as granular layer volumes of the dentate gyrus and cerebellum, may be constrained by conserved
developmental programs. In doing so, I was able to test for cellular signatures of (1) evolutionary
changes in metabolic activity, (2) phylogenetic divergences, (3) specializations in behavior, and (4)
developmental constraints. The degree to which disparate brain regions evolve in concert is shown to
be generally conserved in Eutheria, although a derived ability to evolve regions independently is
observed along the primate lineage. Using a separate dataset on placental and life-histroy character
states, a comprehensive comparative phylogenetic approach was used to resolve relationships among
five aspects of placental structure and to identify syndromes of placental morphology with life-history
variables. My results support two discrete biological phenotypes of placental morphology and life-history,
which are shown to have an evolutionary affect on allocortical, but not neocortical, brain
organization. I have provided a new perspective on exploring how developmental constraints – acting
both within and without the brain – may affect brain organization at the cellular level, and the extent to
which those constraints have been adapted along certain eutherian lineages
Oceanographic results from the VERTEX 3 Particle Interceptor Trap Experiment off central Mexico,October-December,1982
In this report, we present oceanographic results from
VERTEX 3 Particle Interceptor Trap (PIT) experiment
conducted off the western-coast of Mexico during October to
November 1982. The oceanographic data presented here were
obtained during three cruise legs by Moss Landing Marine
Laboratory scientists aboard R/V Cayuse while the detailed
chemical studies were done by other scientists aboard R/V
Wecoma. Only the oceanographic data will be presented in
this report. (PDF contains 82 pages
RPANDA: an R package for macroevolutionary analyses on phylogenetic trees
A number of approaches for studying macroevolution using phylogenetic trees have been developed in the last few years. Here, we present RPANDA, an R package that implements model‐free and model‐based phylogenetic comparative methods for macroevolutionary analyses. The model‐free approaches implemented in RPANDA are recently developed approaches stemming from graph theory that allow summarizing the information contained in phylogenetic trees, computing distances between trees, and clustering them accordingly. They also allow identifying distinct branching patterns within single trees. RPANDA also implements likelihood‐based models for fitting various diversification models to phylogenetic trees. It includes birth–death models with i) constant, ii) time‐dependent and iii) environmental‐dependent speciation and extinction rates. It also includes models with equilibrium diversity derived from the coalescent process, as well as a likelihood‐based inference framework to fit the individual‐based model of Speciation by Genetic Differentiation, which is an extension of Hubbell's neutral theory of biodiversity. RPANDA can be used to (i) characterize trees by plotting their spectral density profiles (ii) compare trees and cluster them according to their similarities, (iii) identify and plot distinct branching patterns within trees, (iv) compare the fit of alternative diversification models to phylogenetic trees, (v) estimate rates of speciation and extinction, (vi) estimate and plot how these rates have varied with time and environmental variables and (vii) deduce and plot estimates of species richness through geological time. RPANDA provides investigators with a set of tools for exploring patterns in phylogenetic trees and fitting various models to these trees, thereby contributing to the ongoing development of phylogenetics in the life sciences
Characterization of Pfiesteria Ichthyocidal Activity
Letter to the Editor regarding article: Drgon, T., et al. 2005. Characterization of ichthyocidal activity of Pfiesteria piscicida: Dependence on the dinospore cell density. Appl. Environ. Microbiol. 71:519–52
A search for binary systems among the nearest L dwarfs
We have used the NICMOS NIC1 camera on the Hubble Space Telescope to obtain
high angular resolution images of 51 ultracool dwarfs in the immediate Solar
Neighbourhood. Nine systems are resolved as binary, with component separations
from 1.5 and 15 AU. All of the systems have components with similar
luminosities, and, consequently, high mass ratios, q > 0.8. Limiting analysis
to L dwarfs within 20 parsecs, the observed binary fraction is 12(+7/-3).
Applying Bayesian analysis to our dataset, we derive a mass-ratio distribution
that peaks strongly at unity. Modelling the semi-major axis distribution as a
logarithmic Gaussian, the best fit is centered at log(a_0) = 0.8 AU (~6.3 AU),
with a (logarithmic) width of 0.3. The current data are consistent with an
overall binary frequency of ~24%.Comment: 29 pages, 4 tables, 8 figures; accepted for publication in A
Harmful algal blooms and eutrophication : examining linkages from selected coastal regions of the United States
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Harmful Algae 8 (2008): 39-53, doi:10.1016/j.hal.2008.08.017.Coastal waters of the United States (U.S.) are subject to many of the major harmful algal
bloom (HAB) poisoning syndromes and impacts. These include paralytic shellfish poisoning
(PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), ciguatera
fish poisoning (CFP) and various other HAB phenomena such as fish kills, loss of submerged
vegetation, shellfish mortalities, and widespread marine mammal mortalities. Here, the
occurrences of selected HABs in a selected set of regions are described in terms of their
relationship to eutrophication, illustrating a range of responses. Evidence suggestive of
changes in the frequency, extent or magnitude of HABs in these areas is explored in the
context of the nutrient sources underlying those blooms, both natural and anthropogenic. In
some regions of the U.S., the linkages between HABs and eutrophication are clear and well
documented, whereas in others, information is limited, thereby highlighting important areas
for further research.Support was provided through the Woods Hole Center for Oceans
and Human Health (to DMA), National Science Foundation (NSF) grants OCE-9808173 and
OCE-0430724 (to DMA), OCE-0234587 (to WPC), OCE04-32479 (to MLP), OCE-0138544
(to RMK), OCE-9981617 (to PMG); National Institute of Environmental Health Sciences
(NIEHS) grants P50ES012742-01 (to DMA) and P50ES012740 (to MLP); NOAA Grants
NA96OP0099 (to DMA), NA16OP1450 (to VLT), NA96P00084 (to GAV and CAH),
NA160C2936 and NA108H-C (to RMK), NA860P0493 and NA04NOS4780241 (to PMG),
NA04NOS4780239-02 (to RMK), NA06NOS4780245 (to DWT). Support was also provided from the West Coast Center for Oceans and Human Health (to VLT and WPC), USEPA
Grant CR826792-01-0 (to GAV and CAH), and the State of Florida Grant S7701617826 (to
GAV and CAH)
Synthesis and biological evaluation of [18F]tetrafluoroborate: a PET imaging agent for thyroid disease and reporter gene imaging of the sodium/iodide symporter
Knockdown of brain-derived neurotrophic factor in specific brain sites precipitates behaviors associated with depression and reduces neurogenesis
Depression has been associated with reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. In addition, animal studies suggest an association between reduced hippocampal neurogenesis and depressive-like behavior. These associations were predominantly established based on responses to antidepressant drugs and alterations in BDNF levels and neurogenesis in depressive patients or animal models for depressive behavior. Nevertheless, there is no direct evidence that the actual reduction of the BDNF protein in specific brain sites can induce depressive-like behaviors or affect neurogenesis in vivo. Using BDNF knockdown by RNA interference and lentiviral vectors injected into specific subregions of the hippocampus we show that a reduction in BDNF expression in the dentate gyrus, but not the CA3, reduces neurogenesis and affects behaviors associated with depression. Moreover, we show that BDNF has a critical function in neuronal differentiation, but not proliferation in vivo. Finally, we found that a specific BDNF knockdown in the ventral subiculum induces anhedonic-like behavior. These findings provide substantial support for the neurotrophic hypothesis of depression and specify anatomical and neurochemical targets for potential antidepressant interventions. Moreover, the specific effect of BDNF reduction on neuronal differentiation has broader implications for the study of neurodevelopment and neurodegenerative diseases
Carbon Nanotubes in Tissue Engineering
For their peculiar features carbon nanotubes (CNTs) are emerging in many areas of nanotechnology applications. CNT-based technology has been increasingly proposed for biomedical applications, to develop biomolecule nanocarriers, bionanosensors and smart material for tissue engineering purposes. In the following chapter this latter application will be explored, describing why CNTs can be considered an ideal material able to support and boost the growth and the proliferation of many kind of tissues
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Harmful algal blooms along the North American west coast region: History, trends, causes, and impacts
Along the Pacific coast of North America, from Alaska to Mexico, harmful algal blooms (HABs) have caused losses to natural resources and coastal economies, and have resulted in human sicknesses and deaths for decades. Recent reports indicate a possible increase in their prevalence and impacts of these events on living resources over the last 10–15 years. Two types of HABs pose the most significant threat to coastal ecosystems in this “west coast” region: dinoflagellates of the genera Alexandrium, Gymnodinium, and Pyrodinium that cause paralytic shellfish poisoning (PSP) and diatoms of the genus Pseudo-nitzschia that produce domoic acid (DA), the cause of amnesic shellfish poisoning (ASP) in humans. These species extend throughout the region, while problems from other HABs (e.g., fish kills linked to raphidophytes or Cochlodinium, macroalgal blooms related to invasive species, sea bird deaths caused by surfactant-like proteins produced by Akashiwo sanguinea, hepatotoxins from Microcystis, diarrhetic shellfish poisoning from Dinophysis, and dinoflagellate-produced yessotoxins) are less prevalent but potentially expanding. This paper presents the state-of-knowledge on HABs along the west coast as a step toward meeting the need for integration of HAB outreach, research, and management efforts.Keywords: Alexandrium, Harmful algal blooms, Pseudo-nitzschia, Domoic acid, Paralytic shellfish poisoning, Heterosigm
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