NaCl transport stimulates prostaglandin release in cultured renal epithelial (MDCK) cells

Prostaglandins (PGs) can modulate a variety of renal functions, including Na+ and Cl- reabsorption. However, it is not known if a direct interdependence exists between PG synthesis and transport activity. The present study was done to find out whether or not the rate of NaCl transport has an influence on PG synthesis in renal tubular cells. For our studies we used cultures of so-called high-resistance MDCK cells, which were originally derived from canine kidney. This cell type has a loop diuretic- and ouabain-sensitive NaCl transport that can be enhanced by activation of the adenylate cyclase (AC). In MDCK cell cultures we found that each state of increased NaCl transport during stimulation of AC by either epinephrine (10(-6) M), isoprenaline (10(-5) M), or forskolin (10(-5) M) was accompanied by a twofold increase in PG release. During inhibition of NaCl transport by furosemide (10(-4) M) or ouabain (2 X 10(-4) M), stimulation of AC failed to increase PGE2 release, whereas basal PG production was not inhibited by either furosemide or ouabain. Furthermore, PG formation during activation of AC was dependent on the concentration of extracellular Na+, whereas PG formation in the absence of activators of AC was independent of extracellular Na+. These results suggest that increased NaCl transport stimulates PG formation in cultures of high-resistance MDCK cells

On the understanding of pulsations in the atmosphere of roAp stars: phase diversity and false nodes

Studies based on high-resolution spectroscopic data of rapidly oscillating Ap stars show a surprising diversity of pulsation behavior in the atmospheric layers, pointing, in particular, to the co-existence of running and standing waves. The correct interpretation of these data requires a careful modelling of pulsations in these magnetic stars. In light of this, in this work we present a theoretical analysis of pulsations in roAp stars, taking into account the direct influence of the magnetic field. We derive approximate analytical solutions for the displacement components parallel and perpendicular to the direction of the magnetic field, that are appropriate to the outermost layer. From these, we determine the expression for the theoretical radial velocity for an observer at a general position, and compute the corresponding pulsation amplitude and phase as function of height in the atmosphere. We show that the integral for the radial velocity has contributions from three different types of wave solutions, namely, running waves, evanescent waves, and standing waves of nearly constant amplitude. We then consider a number of case studies to illustrate the origin of the different pulsational behaviour that is found in the observations. Concerning pulsation amplitude, we find that it generally increases with atmospheric height. Pulsation phase, however, shows a diversity of behaviours, including phases that are constant, increasing, or decreasing with atmospheric height. Finally, we show that there are situations in which the pulsation amplitude goes through a zero, accompanied by a phase jumps of $\pi$, and argue that such behaviour does not correspond to a pulsation node in the outermost layers of the star, but rather to a visual effect, resulting from the observers inability to resolve the stellar surface.Comment: 21 pages, 25 figure

A Quantitative Non-radial Oscillation Model for the Subpulses in PSR B0943+10

In this paper, we analyze time series measurements of PSR B0943+10 and fit them with a non-radial oscillation model. The model we apply was first developed for total intensity measurements in an earlier paper, and expanded to encompass linear polarization in a companion paper to this one. We use PSR B0943+10 for the initial tests of our model because it has a simple geometry, it has been exhaustively studied in the literature, and its behavior is well-documented. As prelude to quantitative fitting, we have reanalyzed previously published archival data of PSR B0943+10 and uncovered subtle but significant behavior that is difficult to explain in the framework of the drifting spark model. Our fits of a non-radial oscillation model are able to successfully reproduce the observed behavior in this pulsar.Comment: 45 pages, 16 figures, accepted Ap

Microkernel security evaluation.

This thesis documents the successful development and testing of a more secure industrial control system field device architecture and software. The implementation of a secure field device has had limitations in the past due to a lack of secure operating system and guidelines. With the recent verification of OK Labs SEL4 microkernel, a verified operating system for such devices is possible, creating a possibility for a secure field device following open standards using known security protocols and low level memory and functionary isolation. The virtualized prototype makes use of common hardware and an existing secure field device architecture to implement a new level of security where the device is verified to function as expected. The experimental evaluation provides performance data which indicates the usefulness of the architecture in the field and security function integration testing to guarantee secure programs can be implemented on the device. Results of the devices functionality are hopeful, showing useful performance for many applications and further development as a fully functional secure field device

Co-habitation and Migration: Urban Design for Bird Migratory Pathways

Urban landscapes are intricate systems interacting throughout the globe. Over the past decades, urban development has widely sprawled and fragmented flyway systems and corridors. This has led to many changes in species composition and has even caused the extinction of some animals (Marzluff 1997). Recent studies have indicated that there exists a protective or restorative design to create stepping-stone connectivity in urban areas. This study looks to understanding potential benefits in urban biodiversity, animal species protection, and urban benefits of green roof designs

Mechanism of NaCl transport-stimulated prostaglandin formation in MDCK cells

Recently we have found that stimulation of NaCl transport in high-resistance MDCK cells enhances their prostaglandin formation. In the present study, we investigated the mechanisms by which prostaglandin formation could be linked to the ion transport in these cells. We found that stimulation of transport caused a transient stimulation of prostaglandin formation lasting 5-10 min. The rise in prostaglandin formation was paralleled by a rise of free intracellular arachidonic acid. Analysis of membrane lipids revealed that the rise of free arachidonic acid was paralleled by a loss of arachidonic acid from polyphosphoinositides. We failed to obtain indications for the stimulation of calcium-dependent phospholipase A2. However, we did obtain evidence that the incorporation of arachidonic acid into phospholipids was diminished during stimulation of ion transport, indicating a decreased rate of reesterification. Despite the fact that there was no significant fall in total cellular ATP on stimulation of ion transport, we found a high and transient rise of lactate production of the cells on stimulation of the ion transport indicating an alteration of the ADP/ATP ratio. Moreover, prostaglandin formation and lactate formation were linearly correlated in this situation. When glucose utilization was inhibited by mannoheptulose, the rise in lactate formation was abolished, whereas that of PG formation was unaltered, indicating that lactate formation and prostaglandin formation were not causally linked on stimulation of ion transport. Our results suggest that an increase in the rate of sodium chloride transport by MDCK cells stimulates formation by an inhibition of reesterification of free arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS

The NASA Astrophysics Data System: Data Holdings

Since its inception in 1993, the ADS Abstract Service has become an indispensable research tool for astronomers and astrophysicists worldwide. In those seven years, much effort has been directed toward improving both the quantity and the quality of references in the database. From the original database of approximately 160,000 astronomy abstracts, our dataset has grown almost tenfold to approximately 1.5 million references covering astronomy, astrophysics, planetary sciences, physics, optics, and engineering. We collect and standardize data from approximately 200 journals and present the resulting information in a uniform, coherent manner. With the cooperation of journal publishers worldwide, we have been able to place scans of full journal articles on-line back to the first volumes of many astronomical journals, and we are able to link to current version of articles, abstracts, and datasets for essentially all of the current astronomy literature. The trend toward electronic publishing in the field, the use of electronic submission of abstracts for journal articles and conference proceedings, and the increasingly prominent use of the World Wide Web to disseminate information have enabled the ADS to build a database unparalleled in other disciplines. The ADS can be accessed at http://adswww.harvard.eduComment: 24 pages, 1 figure, 6 tables, 3 appendice

Pharmacokinetics of recombinant human erythropoietin applied subcutaneously to children with chronic renal failure

The single-dose pharmacokinetics of recombinant human erythropoietin (rHuEPO) given SC was investigated in 20 patients aged 7-20 years at different stages of chronic renal failure. In a pilot study we confirmed the lower bioavailability of the drug in 2 children when given SC compared with the IV route (24% and 43%, respectively). Following administration of 4,000 units/m2, rHuEPO SC effective serum erythropoietin concentrations increased from a mean baseline level (+/- SD) of 23 +/- 13 units/l to a mean peak concentration of 265 +/- 123 units/l, which was reached after 14.3 +/- 9.4 h, followed by a slow decline until baseline values were attained at 72 h. Mean residence time was 30 +/- 9 h and mean elimination half-time 14.3 +/- 7 h. The single-dose kinetics of SC rHuEPO in children with different degrees of renal failure are comparable to those in adult patients. Possibly, the higher efficacy of SC rHuEPO in patients with renal anaemia compared with IV rHuEPO is related to its prolonged action

Role of protein kinase C in inhibition of renin release caused by vasoconstrictors

It was the aim of the present study to get insight into some of the intracellular mechanisms by which the vasoconstrictor hormones angiotensin II (ANG II), arginine vasopressin (AVP), and norepinephrine (NE) inhibit renin release from renal juxtaglomerular cells. To this end a primary cell culture from rat renal cortex was established that consisted of 50% juxtaglomerular cells. The cultured juxtaglomerular cells contained prominent renin granules closely resembling those in the intact kidney and responded to a number of stimuli of renin release. By using these cultures, we found that ANG II (10(-7) M), AVP (10(-6) M), and NE (10(-5) M) inhibited renin release and increased the calcium permeability of the plasma membrane of the cultured cells. Both the effects on renin release and on calcium permeability could be diminished or even be abolished by the calcium channel blocker verapamil (Vp) (10(-5) M). ANG II, AVP, and NE led to an increased formation of diacylglycerol (DAG), a well-known stimulator of protein kinase C (PKC). Moreover, a direct stimulation of PKC by 12-O-tetradecanoylphorbol-13-acetate (TPA) (10(-8)-10(-6) M) also inhibited renin release and increased the calcium permeability of the cell membrane. Similar to ANG II, AVP, and NE, the effects of TPA on calcium permeability and renin release could be diminished by Vp. In conclusion, these results point toward a common mechanism by which vasoconstrictors inhibit renin release from renal juxtaglomerular cells: ANG II, AVP, and NE activate a phospholipase C, which generates DAG.(ABSTRACT TRUNCATED AT 250 WORDS