1,774 research outputs found
Evaluating techniques in tissue clarification using CLARITY imaging and investigating where sodium is sensed in the body
OBJECTIVE: Previous studies have shown the significant contribution of sympathoinhibition in response to sodium loading to prevent increases in mean arterial blood pressure in salt resistant phenotypes. It has also been shown that brain Gαi2 protein gated signal transduction plays a major role in this pathway, however, the specific mechanisms through which this pathway is activated remain less well understood. The purpose of this study was to elucidate the relative contribution of increased sodium in either the plasma or the cerebrospinal fluid (CSF) to the regulation of mean arterial pressure and natriuresis. Additionally we explored the potential for using the novel CLARITY Imaging technique to identify the relative activity of neurons in areas of the brain thought to play a major role in body fluid homeostasis in response to salt.
METHODS: Rats that were pre-treated with either scrambled or Gαi2 oligodeoxynucleotides (ODN), to selectively down regulate brain Gαi2 proteins, were challenged either peripherally or centrally with sodium. Upon sodium loading physiological parameters were measured for two hours after which the animal's brains were recovered for immunohistochemical (IHC) analysis of the paraventricular nucleus, a known regulatory center for body fluid homeostasis and blood pressure regulation.
Additionally we adapted a version of the published CLARITY Imaging protocols for optically clearing tissue through application of electrophoretic tissue clearing (ETC) to a larger rat model.
RESULTS: In scrambled ODN pre-treated rats we observed a temporary increase in MAP in response to both the peripheral and central sodium challenge. In the Gαi2 ODN pre-treated animals we saw some form of attenuation to this response in both studies, however, where in the peripheral challenge there was an increase in the amount of time that it took the rats to return to normotension with no alteration in natriuresis, in the central challenge there was a large attenuation in natriuresis with no differences in the time to return to baseline MAP. Our IHC analysis also showed a decrease in neuronal activation of paraventricular medial parvocellular neurons in Gαi2 pre-treated rats that were challenged peripherally vs their SCR pre-treated counterparts. No such difference was observed in either of the pre-treatment groups from the central sodium challenge study.
In the CLARITY study we found that it is possible to adapt the method for optically clearing tissue to the larger model, however, we encountered several issues related to tissue swelling and peripheral tissue damage.
CONCLUSION: Based on our current results it seems evident that there are at least two different mechanisms that activate the cardiovascular regulatory control centers in the brain that prevent long term increases in mean arterial pressure in response to increased salt. It also appears that these two different mechanisms are triggered either by increases in plasma or CSF salinity, though which of these two mechanisms may be directly responsible for the development of salt sensitive hypertension requires further investigation.
While we had some success at optically clearing larger tissue volumes through ETC, problems we encountered with maintaining tissue integrity for investigations of intact neural networks prevented us from applying this technique, in its current form, to our investigation of salt sensitive hypertension
Contractive projections and operator spaces
Parallel to the study of finite dimensional Banach spaces, there is a growing
interest in the corresponding local theory of operator spaces. We define a
family of Hilbertian operator spaces H_n^k,0< k < n+1, generalizing the row and
column Hilbert spaces R_n,C_n and show that an atomic subspace X of B(H) which
is the range of a contractive projection on B(H) is isometrically completely
contractive to a direct sum of the H_n^k and Cartan factors of types 1 to 4. In
particular, for finite dimensional X, this answers a question posed by Oikhberg
and Rosenthal. Explicit in the proof is a classification up to complete
isometry of atomic w*-closed JW*-triples without an infinite dimensional rank 1
w^*-closed idealComment: 40 pages, latex, the paper was submitted in October of 2000 and an
announcement with the same title appeared in C. R. Acad. Sci. Paris 331
(2000), 873-87
Operator space characterizations of C*-algebras and ternary rings
We prove that an operator space is completely isometric to a ternary ring of
operators if and only if the open unit balls of all of its matrix spaces are
bounded symmetric domains. From this we obtain an operator space
characterization of C*-algebras.Comment: 20 pages, latex, submitted in November 200
State spaces of JB*-triples
An atomic decomposition is proved for Banach spaces which satisfy some affine
geometric axioms compatible with notions from the quantum mechanical measuring
process. This is then applied to yield, under appropriate assumptions,
geometric characterizations, up to isometry, of the unit ball of the dual space
of a JB*-triple, and up to complete isometry, of one-sided ideals in
C*-algebras.Comment: 28 page
Noncommutative topology and Jordan operator algebras
Jordan operator algebras are norm-closed spaces of operators on a Hilbert
space with for all . We study noncommutative topology,
noncommutative peak sets and peak interpolation, and hereditary subalgebras of
Jordan operator algebras. We show that Jordan operator algebras present perhaps
the most general setting for a `full' noncommutative topology in the
C*-algebraic sense of Akemann, L. G. Brown, Pedersen, etc, and as modified for
not necessarily selfadjoint algebras by the authors with Read, Hay and other
coauthors. Our breakthrough relies in part on establishing several strong
variants of C*-algebraic results of Brown relating to hereditary subalgebras,
proximinality, deeper facts about for a left ideal in a C*-algebra,
noncommutative Urysohn lemmas, etc. We also prove several other approximation
results in -algebras and various subspaces of -algebras, related to
open and closed projections, and technical -algebraic results of Brown.Comment: Revision, many typos corrected and exposition improved in places.
Section 2 expanded with some applications of the main theorem of that sectio
Metric characterizations II
The present paper is a sequel to our paper "Metric characterization of
isometries and of unital operator spaces and systems". We characterize certain
common objects in the theory of operator spaces (unitaries, unital operator
spaces, operator systems, operator algebras, and so on), in terms which are
purely linear-metric, by which we mean that they only use the vector space
structure of the space and its matrix norms. In the last part we give some
characterizations of operator algebras (which are not linear-metric in our
strict sense described in the paper).Comment: Presented at the AMS/SAMS Satellite Conference on Abstract Analysis,
University of Pretoria, South Africa, 5-7 December 2011. Revision of
2/24/2012 (Examples after theorem 3.2 added
Open partial isometries and positivity in operator spaces
We study positivity in C*-modules and operator spaces using open tripotents,
and an ordered version of the `noncommutative Shilov boundary'. Because of
their independent interest, we also systematically study open tripotents and
their properties.Comment: To appea
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