1,861 research outputs found

    Increased body fluid purine levels during hypotensive events : Evidence for ATP degradation

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    Tissue ischemia leads to adenosine triphosphate (ATP) breakdown with elevation of body fluid ATP metabolites. This study tests the hypothesis that there is a direct relationship between periods of hypotension and body fluid uric acid and oxypurine levels in 19 prospectively studied patients. Significant elevations in urine oxypurine/creatinine clearance were found during periods of hypotension as compared with nonhypotensive periods (p <0.05). During severe episodes of hypotension, the serum urate level was significantly elevated as well (p <0.05). The increase in these body fluid products of ATP degradation may reflect cellular ischemia during hypotensive periods. There was a weak correlation (r = -0.31, p <0.001) between the systolic blood pressure and urine oxypurine/creatinine clearance. However, variability in the appearance of body fluid ATP breakdown products during episodes of hypotension suggests the interplay of multiple factors in the degradation of ATP. The use of ATP degradation products to quantitate the physiologic significance of clinical events remains tantalizing but not proved.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26423/1/0000510.pd

    Conditional statistics of passive-scalar mixing in a confined wake flow

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    Experimental results for conditional statistics in a confined turbulent wake were compared to the linear model and the transported probability density function (PDF) model for predicting the velocity conditioned on scalar mixture fraction and to a linear model for predicting the scalar mixture fraction conditioned on velocity. For velocity conditioned on scalar mixture fraction, the linear model was found to accurately predict the conditional transverse velocity, but for the conditional streamwise velocity, agreement between the experiments and the linear model was poor. The transverse conditional velocity was accurately predicted by the transported PDF model, but for the streamwise conditional velocity, a modified transported PDF model that incorporated two components of the scalar diffusivity tensor had to be used. Finally, it was found that a linear model for predicting the fluctuating scalar conditioned on velocity performed poorly due to the strongly non-Gaussian scalar PDF at the downstream locations investigated

    Osteogenic stimulatory conditions enhance growth and maturation of endothelial cell microvascular networks in culture with mesenchymal stem cells

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    To optimize culture conditions for in vitro prevascularization of tissue-engineered bone constructs, the development of organotypic blood vessels under osteogenic stimulatory conditions (OM) was investigated. Coculture of endothelial cells and mesenchymal stem cells was used to assess proangiogenic effects of mesenchymal stem cells on endothelial cells. Four different culture conditions were evaluated for their effect on development of microvascular endothelial cell networks. Mineralization, deposition of extracellular matrix, and perivascular gene expression were studied in OM. After 3 days, endothelial cells established elongated capillary-like networks, and upregulated expression of vascular markers was seen. After 15 days, all parameters evaluated were significantly increased for cultures in OM. Mature networks developed in OM presented lumens enveloped by basement membrane-like collagen IV, with obvious mineralization and upregulated perivascular gene expression from mesenchymal stem cells. Our results suggest osteogenic stimulatory conditions to be appropriate for in vitro development of vascularized bone implants for tissue engineering

    A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment

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    We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by the Palomar Transient Factory. PTF11qcj is located at a distance of dL ~ 124 Mpc. Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated supernova 1998bw (L_{5GHz} ~ 10^{29} erg/s/Hz). PTF11qcj is also detected in X-rays with the Chandra observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the supernova interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of ~10^{-4} Msun/yr x (v_w/1000 km/s), and a velocity of ~(0.3-0.5)c for the fastest moving ejecta (at ~10d after explosion). However, these estimates are derived assuming the simplest model of supernova ejecta interacting with a smooth circumstellar material characterized by radial power-law density profile, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio light curve shows deviations from such a simple model, as well as a re-brightening at late times. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). An IR light echo from pre-existing dust is in agreement with our infrared data. Our analysis of pre-explosion data from the Palomar Transient Factory suggests that a precursor eruption of absolute magnitude M_r ~ -13 mag may have occurred ~ 2.5 yr prior to the supernova explosion. Based on our panchromatic follow-up campaign, we conclude that PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.Comment: 43 pages, 15 figures; this version matches the one published in ApJ (includes minor changes that address the Referee's comments.

    Real-Time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey

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    The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 square degree field of view mounted on the 48-in Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the gamma-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts.Comment: ApJ, in press; all spectroscopic data available from the Weizmann Institute of Science Experimental Astrophysics Spectroscopy System (WISEASS; http://www.weizmann.ac.il/astrophysics/wiseass/

    Review of microdialysis in brain tumors, from concept to application: First Annual Carolyn Frye-Halloran Symposium

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    In individuals with brain tumors, pharmacodynamic and pharmacokinetic studies of therapeutic agents have historically used analyses of drug concentrations in serum or cerebrospinal fluid, which unfortunately do not necessarily reflect concentrations within the tumor and adjacent brain. This review article introduces to neurological and medical oncologists, as well as pharmacologists, the application of microdialysis in monitoring drug metabolism and delivery within the fluid of the interstitial space of brain tumor and its surroundings. Microdialysis samples soluble molecules from the extracellular fluid via a semipermeable membrane at the tip of a probe. In the past decade, it has been used predominantly in neurointensive care in the setting of brain trauma, vasospasm, epilepsy, and intracerebral hemorrhage. At the first Carolyn Frye-Halloran Symposium held at Massachusetts General Hospital in March 2002, the concept of microdialysis was extended to specifically address its possible use in treating brain tumor patients. In doing so we provide a rationale for the use of this technology by a National Cancer Institute consortium, New Approaches to Brain Tumor Therapy, to measure levels of drugs in brain tissue as part of phase 1 trials. Originally published Neuro-oncology, Vol. 6, No. 1, Jan 200