6,875 research outputs found
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Synapses appear on doublecortin-immunolabeled hilar basal dendrites of newborn dentate granule cells obtained from epileptic adult rats
The rationality of Sol manifolds
Let be the fundamental group of a manifold modeled on three
dimensional Sol geometry. We prove that has a finite index subgroup
which has a rational growth series with respect to a natural generating
set. We do this by enumerating by a regular language. However, in contrast
to most earlier proofs of this sort our regular language is not a language of
words in the generating set, but rather reflects a different geometric
structure in .Comment: 30 pages; author's name changed to agree with published version; to
appear in Journal of Algebr
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Newly generated dentate granule cells from epileptic rats exhibit elongated hilar basal dendrites that align along GFAP-immunolabeled processes.
Previous studies showed that neurogenesis occurs in the dentate gyrus of the adult rodent. Recent evidence suggests that the resulting newly born neurons integrate into pre-existing hippocampal circuitry. Newly born neurons in the developing and adult dentate gyrus exhibit a transient basal dendrite. In adult pilocarpine-induced epileptic rats, basal dendrites persist and are ectopically located in the hilus where they receive synaptic input from mossy fiber axons. We hypothesize that these hilar basal dendrites are derived from newly born neurons that are born after the pilocarpine-induced seizures. To test this hypothesis, the length of basal dendrites from epileptic rats was compared with that from control rats using doublecortin immunocytochemistry, which labels newly born neurons and their processes for up to 3 weeks after their genesis. The data on hilar basal dendrites in pilocarpine animals indicate that those from newly born neurons are significantly longer than those found in the control rats. We also demonstrate that 20% of newly born neurons in the epileptic rat have a basal dendrite that enters the hilus at an angle greater than 30 degrees from its cell body as compared with <2% in the control rats. Lastly, we provide evidence that the hilar basal dendrites in the epileptic rats are adjacent to glial fibrillary acidic protein-labeled astrocytic processes in the hilus and suggest that an ectopic glial scaffold in the hilus is involved with the formation of hilar basal dendrites. In conclusion, the data show that newly born neurons from epileptic rats have longer hilar basal dendrites and their formation might relate to gliosis which occurs as a result of hilar neuronal cell loss after status epilepticus
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Rapid astrocyte and microglial activation following pilocarpine-induced seizures in rats
Astrocyte and microglial activation occurs following seizures and plays a role in epileptogenesis. However, the precise temporal and spatial response to seizures has not been fully examined. The pilocarpine model of temporal lobe epilepsy was selected to examine glial changes following seizures because morphological changes in the hippocampus closely mimic the human condition. Astrocytic and microglial changes in the hippocampus were examined during the first 5 days after pilocarpine-induced seizures in rats by analyzing GFAP, Iba1 and S100B-immunolabeling in CA1, CA3, and the hilus. Also, 3-dimensional reconstructions of microglial cells from the hilus and granule cell layer were analyzed. Lastly, astrocyte hypertrophy was examined in the hilus using electron microscopy. At 1 day after seizures and continuing throughout the 5 days examined, hypertrophied Iba1-labeled microglial cells and glial fibrillary acidic protein (GFAP)-labeled astrocytes were observed. At 1 and 2 days after seizures, significantly greater Iba1 immunolabeling was observed in CA1, CA3, and the hilus. In addition, both the area of Iba1 labeled processes and the number of their endings were increased in the hilus beginning at 1 day after seizures. S100B-immunolabeling was significantly elevated in CA3 at 1 day, in CA3 and CA1 at 2 days, and in all three hippocampal regions at 3 days after seizures. Electron microscopy confirmed astrocytic hypertrophy and demonstrated astrocytic cell bodies in the location where glial endfeet normally appear on capillaries. The differential response patterns of astrocytes and microglial cells following pilocarpine-induced seizures may signify their detrimental role in neuroinflammation after seizures. © 2008 International League Against Epilepsy
Pattern of extinction of the woolly mammoth in Beringia.
Extinction of the woolly mammoth in Beringia has long been subject to research and speculation. Here we use a new geo-referenced database of radiocarbon-dated evidence to show that mammoths were abundant in the open-habitat of Marine Isotope Stage 3 (âŒ45-30 ka). During the Last Glacial Maximum (âŒ25-20 ka), northern populations declined while those in interior Siberia increased. Northern mammoths increased after the glacial maximum, but declined at and after the Younger Dryas (âŒ12.9-11.5 ka). Remaining continental mammoths, now concentrated in the north, disappeared in the early Holocene with development of extensive peatlands, wet tundra, birch shrubland and coniferous forest. Long sympatry in Siberia suggests that humans may be best seen as a synergistic cofactor in that extirpation. The extinction of island populations occurred at âŒ4 ka. Mammoth extinction was not due to a single cause, but followed a long trajectory in concert with changes in climate, habitat and human presence
Optical von Neumann measurement
We present an optical scheme that realizes the standard von Neumann
measurement model, providing an indirect measurement of a quadrature of the
field with controllable Gaussian state-reduction. The scheme is made of simple
optical elements, as laser sources, beam splitters, and phase sensitive
amplifiers, along with a feedback mechanism that uses a Pockels cell. We show
that the von Neumann measurement is achieved without the need of working in a
ultra-short pulsed regime.Comment: One latex figure. Accepted on Phys. Lett.
Collapse to Black Holes in Brans-Dicke Theory: I. Horizon Boundary Conditions for Dynamical Spacetimes
We present a new numerical code that evolves a spherically symmetric
configuration of collisionless matter in the Brans-Dicke theory of gravitation.
In this theory the spacetime is dynamical even in spherical symmetry, where it
can contain gravitational radiation. Our code is capable of accurately tracking
collapse to a black hole in a dynamical spacetime arbitrarily far into the
future, without encountering either coordinate pathologies or spacetime
singularities. This is accomplished by truncating the spacetime at a spherical
surface inside the apparent horizon, and subsequently solving the evolution and
constraint equations only in the exterior region. We use our code to address a
number of long-standing theoretical questions about collapse to black holes in
Brans-Dicke theory.Comment: 46 pages including figures, uuencoded gz-compressed postscript,
Submitted to Phys Rev
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Toxo XV: A Congress at the Birthplace of Toxoplasma.
In this TrendsTalk article, the organizers of the 15th International Congress on Toxoplasma Biology and Toxoplasmosis, Professors Jorge Gomez Marin and Alejandra de-la-Torre, bring the highlights of this event and the key outcome from the inaugural workshop on the environmental transmission of Toxoplasma gondii organized by Doctors Aurélien DumÚtre and Karen Shapiro
Subspace hypercyclicity
A bounded linear operator T on Hilbert space is subspace-hypercyclic for a
subspace M if there exists a vector whose orbit under T intersects the subspace
in a relatively dense set. We construct examples to show that
subspace-hypercyclicity is interesting, including a nontrivial
subspace-hypercyclic operator that is not hypercyclic. There is a Kitai-like
criterion that implies subspace-hypercyclicity and although the spectrum of a
subspace-hypercyclic operator must intersect the unit circle, not every
component of the spectrum will do so. We show that, like hypercyclicity,
subspace-hypercyclicity is a strictly infinite-dimensional phenomenon.
Additionally, compact or hyponormal operators can never be
subspace-hypercyclic.Comment: 15 page
Descartes, corpuscles and reductionism : mechanism and systems in Descartes' physiology
I argue that Descartes explains physiology in terms of whole systems, and not in terms of the size, shape and motion of tiny corpuscles (corpuscular mechanics). It is a standard, entrenched view that Descartesâs proper means of explanation in the natural world is through strict reduction to corpuscular mechanics. This view is bolstered by a handful of corpuscular-mechanical explanations in Descartesâs physics, which have been taken to be representative of his treatment of all natural phenomena. However, Descartesâs explanations of the âprincipal partsâ of physiology do not follow the corpuscularâmechanical pattern. Des Chene (2001) has identified systems in Descartesâs account of physiology, but takes them ultimately to reduce down to the corpuscle level. I argue that they do not. Rather, Descartes maintains entire systems, with components selected from multiple levels of organisation, in order to construct more complete explanations than corpuscular mechanics alone would allow
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