Characterization of pericyte invasive responses and pericyte-induced vascular morphogenesis in 3D matrices : distinctions with vascular smooth muscle cells [abstract]

During vascular morphogenic events, mural cells are recruited to developing endothelial tubes to aid in stabilization and maturation of the new vessels. There are two known types of mural cells, pericytes and vascular smooth muscle cells (VSMCs). Their different locations within the vasculature (capillaries versus larger vessels, respectively) suggest that there may be distinct vessel recruitment mechanisms or factors, however, these issues remain unresolved. Platelet-derived growth factor (PDGF) is known to be released from endothelial cells during morphogenic events and has been shown to influence mural cell functions. In this study, we investigate the ability of PDGF isoforms to regulate pericyte versus VSMC invasive behaviors and recruitment to EC monolayers or developing vascular tubes

Un alga japonesa en la costa patagónica

En diciembre de 1992, a varios metros de profundidad y adheridos a los pilotes del muelle Almirante Storni de Puerto Madryn (Prov. Chubut, Argentina), se observaron algunos ejemplares de un alga de gran tamaño no registrada entre la flora marina argentina. Se trataba de Undaria pinnatifida, una especie originaria de las costas de Japón, que arribó presumiblemente en forma accidental, trasladada por barcos. Progresivamente esta especie se fue dispersando a lo largo de las costas de la Patagonia Argentina, con indeseables efectos ambientales, sociales y económicos. Se incluye información sobre las características del alga, su adaptación a diversas condiciones ambientales, su dispersión mundial, el impacto ambiental en la región, además de un glosario y lecturas sugeridas

The role of PDGF-BB, lysophospatidic acid, and proteolytic activity in the invasive behavior of human brain vascular pericytes [abstract]

Recruitment of pericytes is needed to stabilize new vessels formed during angiogenesis or vasculogenesis. Although important to the viability of the vessel, information on how the pericytes are recruited to blood vessels is lacking. It is believed that molecules produced by endothelial cells lining the blood vessel walls influence pericyte recruitment. Both the upward and downward invasion of human brain vascular pericytes (HBVPs) through 3D collagen gels was tested in the presence of different endothelial cell produced factors. Of the molecules tested, platelet-derived growth factor- (PDGF-BB) was found to be the most important in signaling HBVPs to invade in a 3D collagen matrix. Invasion can further be enhanced through synergism of PDGF-BB with lysophosphatidic acid (LPA), an activator of G protein signaling. When given together these two molecules increase invasion up to two times that of PDGF alone. The use of pertussis toxin, which blocks the activity of LPA, and recombinant soluble PDGF-receptor beta which traps and blocks PDGFBB, were able to significantly block invasion in response to PDGF and LPA and provide further support for their functional role in HBVP invasive behavior. Invasioncan also be blocked by using GM6001, a matrix metalloproteinase (MMP) inhibitor, demonstrating a requirement for MMP activity during this response. This work further elucidates mechanisms underlying how pericytes invade and migrate toward developing blood vessels to regulate capillary tube assembly and maturation in 3D extracellular matrix environments

Cosmological Evolution of a Purely Conical Codimension-2 Brane World

We study the cosmological evolution of isotropic matter on an infinitely thin conical codimension-two brane-world. Our analysis is based on the boundary dynamics of a six-dimensional model in the presence of an induced gravity term on the brane and a Gauss-Bonnet term in the bulk. With the assumption that the bulk contains only a cosmological constant Lambda_B, we find that the isotropic evolution of the brane-universe imposes a tuned relation between the energy density and the brane equation of state. The evolution of the system has fixed points (attractors), which correspond to a final state of radiation for Lambda_B=0 and to de Sitter state for Lambda_B>0. Furthermore, considering anisotropic matter on the brane, the tuning of the parameters is lifted, and new regions of the parametric space are available for the cosmological evolution of the brane-universe. The analysis of the dynamics of the system shows that, the isotropic fixed points remain attractors of the system, and for values of Lambda_B which give acceptable cosmological evolution of the equation of state, the line of isotropic tuning is a very weak attractor. The initial conditions, in this case, need to be fine tuned to have an evolution with acceptably small anisotropy.Comment: 20 pages, 4 figures, typo correcte

Guiding neutral atoms around curves with lithographically patterned current-carrying wires

Laser-cooled neutral atoms from a low-velocity atomic source are guided via a magnetic field generated between two parallel wires on a glass substrate. The atoms bend around three curves, each with a 15-cm radius of curvature, while traveling along a 10-cm-long track. A maximum flux of 2*10^6 atoms/sec is achieved with a current density of 3*10^4 A/cm^2 in the 100x100-micrometer-cross-section wires. The kinetic energy of the guided atoms in one transverse dimension is measured to be 42 microKelvin.Comment: 9 page

Cold atoms in videotape micro-traps

We describe an array of microscopic atom traps formed by a pattern of magnetisation on a piece of videotape. We describe the way in which cold atoms are loaded into one of these micro-traps and how the trapped atom cloud is used to explore the properties of the trap. Evaporative cooling in the micro-trap down to a temperature of 1 microkelvin allows us to probe the smoothness of the trapping potential and reveals some inhomogeneity produced by the magnetic film. We discuss future prospects for atom chips based on microscopic permanent-magnet structures.Comment: Submitted for EPJD topical issue "Atom chips: manipulating atoms and molecules with microfabricated structures

A Minimal Length from the Cutoff Modes in Asymptotically Safe Quantum Gravity

Within asymptotically safe Quantum Einstein Gravity (QEG), the quantum 4-sphere is discussed as a specific example of a fractal spacetime manifold. The relation between the infrared cutoff built into the effective average action and the corresponding coarse graining scale is investigated. Analyzing the properties of the pertinent cutoff modes, the possibility that QEG generates a minimal length scale dynamically is explored. While there exists no minimal proper length, the QEG sphere appears to be "fuzzy" in the sense that there is a minimal angular separation below which two points cannot be resolved by the cutoff modes.Comment: 26 pages, 1 figur

Volume Estimation of the Thalamus Using Freesurfer and Stereology: Consistency between Methods

Freely available automated MR image analysis techniques are being increasingly used to investigate neuroanatomical abnormalities in patients with neurological disorders. It is important to assess the specificity and validity of automated measurements of structure volumes with respect to reliable manual methods that rely on human anatomical expertise. The thalamus is widely investigated in many neurological and neuropsychiatric disorders using MRI, but thalamic volumes are notoriously difficult to quantify given the poor between-tissue contrast at the thalamic gray-white matter interface. In the present study we investigated the reliability of automatically determined thalamic volume measurements obtained using FreeSurfer software with respect to a manual stereological technique on 3D T1-weighted MR images obtained from a 3 T MR system. Further to demonstrating impressive consistency between stereological and FreeSurfer volume estimates of the thalamus in healthy subjects and neurological patients, we demonstrate that the extent of agreeability between stereology and FreeSurfer is equal to the agreeability between two human anatomists estimating thalamic volume using stereological methods. Using patients with juvenile myoclonic epilepsy as a model for thalamic atrophy, we also show that both automated and manual methods provide very similar ratios of thalamic volume loss in patients. This work promotes the use of FreeSurfer for reliable estimation of global volume in healthy and diseased thalami.</p

On the unique possibility to increase significantly the contrast of dark resonances on D1 line of 87^{87}Rb

We propose and study, theoretically and experimentally, a new scheme of excitation of a coherent population trapping resonance for D1 line of alakli atoms with nuclear spin $I=3/2$ by bichromatic linearly polarized light ({\em lin}$||${\em lin} field) at the conditions of spectral resolution of the excited state. The unique properties of this scheme result in a high contrast of dark resonance for D1 line of $^{87}$Rb.Comment: 9 pages, 7 figures. This material has been partially presented on ICONO-2005, 14 May 2005, St. Petersburg, Russia. v2 references added; text is changed a bi