bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the ability of plants to alter the pH of the flooding medium as an early symptom of flooding stress in Helianthus annuus
Authors: Drakeford David R. , Reid David M.
Published: May 2008

Roots of sunflower plants (Helianthus annuus L.) were flooded in nutrient medium and nonflooded controls were continuously bathed with nutrient medium in a hydroponic system. The pH of the nutrient medium was measured over a period of days. Within 24 h the pH of the nutrient medium in the flooded treatments was 1 pH unit higher than that of the nonflooded treatments and remained higher over several days. Nonflooded plants were able to acidify the medium to a pH value of 4 but when flooded at this pH plants underwent a rapid "catastrophic death," different from normal senescence, in which the shoot dehydrated before chlorosis set in. This pH phenomenon is consistent with both an active acidification of the nutrient medium under nonstressed conditions and a passive drift to a pH dictated by the materials of the hydroponic system, under flooded conditions. It is postulated that flooding rapidly shuts down an acidification mechanism and that this may be symptomatic of early biophysical changes brought about by flooding.
The effect of increasing elevation on leaf cuticle thickness and cuticular transpiration in balsam fir
Authors: DeLucia Evan H. , Berlyn Graeme P.
Published: May 2008

First-year needles and stems of Abies balsamea were collected at the end of the growing season along an elevational gradient on Mt. Moosilauke, NH. Tissue was sampled from the base (732 m), midslope (1143 m), forest limit (1402 m), and tree line (1455 m). Mean cuticle thickness on the adaxial needle surface decreased with increasing elevation from 3.01 to 2.21 μm. A similar decline was observed for the cutinized cell wall at the lower three elevations. Associated with the decline in cuticular thickness was a 59.3% increase in the rate of cuticular water loss per gram dry weight from 732 to 1402 m. The amount of epicuticular wax and other features of leaf anatomy were also examined along the elevational gradient. The high rates of cuticular water loss in these subalpine trees increase the risk of desiccation damage at high elevations and support the concept that they can be a contributing factor in the formation of alpine tree line.
Studies on the Festuca ovina complex in the Canadian Cordillera
Authors: Pavlick Leon E.
Published: May 2008

Seven native taxa of the Festuca ovina complex are recognized for the Canadian Cordillera. Pseudoviviparous material from this region is different from F. vivipara (L.) Sm., and F. vivipara subsp. glabra Frederiksen is raised to the status of species, F. viviparoidea Krajina ex Pavlick. A new name, Festuca viviparoidea subsp. krajinae Pavlick, is proposed for the Canadian Cordillera plants. A new variety from British Columbia, Festuca saximontana Rydb. var. robertsiana Pavlick is described. The other taxa treated are F. saximontana Rydb. var. saximontana; F. saximontana var. purpusiana Frederiksen & Pavlick; F. brachyphylla Schult. & Schult.; F. baffinensis Polun.; and F. minutiflora Rydb., a species rarely collected in Canada. Distributions are given.
Competition for endogenous and exogenous nutrients between Sporobolomyces roseus and Cochliobolus sativus
Authors: Fokkema N. J.
Published: May 2008

Sporobolomyces roseus reduced conidial germination of Cochliobolus sativus on glass slides covered with a thin layer (0.1 mm) of water agar or Czapek Dox agar by ca. 60 and 99%, respectively. On wheat flag leaves S. roseus reduced conidial germination by ca. 15% but reduced germ tube length by ca. 48%. However, cell-free aqueous diffusates collected from water agar slides and leaves with and without S. roseus showed no differential effect on Co. sativus when bioassayed on water agar slides. Diffusates from Czapek Dox agar with S. roseus reduced conidial germination by 46% when compared with the nutrient-rich diffusate from Czapek Dox agar alone. Although this demonstrated the ability of the yeasts to reduce the amount of exogenous nutrients, this did not account for the 99% reduction found in the presence of S. roseus. When Co. sativus was separated from S. roseus on Czapek Dox agar by two layers of cellophane, the reduction was the same and maintained for at least 3 days. If Co. sativus was removed from S. roseus by transferring the upper cellophane sheet to a glass slide, germination was restored, indicating that the yeasts formed also a continuous drain of endogenous nutrients from the conidia. A steady supply of amino acids and (or) glucose to Czapek Dox agar slides with S. roseus and Co. sativus could only partially overcome the antagonistic interaction.
Changes in inorganic phosphate and seed germinability during afterripening of wild oats
Authors: Quick William A. , Hsiao Andrew I.
Published: May 2008

The period of afterripening required by dormant seeds of wild oat (Avena fatua L.) depends upon their genetic and environmental history. A steady increase was found in the level of inorganic phosphate (Pi) and germinability of dry mature caryopses of genetically dormant wild oat lines as afterripening progressed. There were no appreciable changes in Pi or in germinability of the companion seeds stored at −15 °C over the period of study. Secondary seeds were more dormant and had lower levels of Pi during afterripening than was the case with primary seeds. Storage at room temperature had little effect on Pi level of nondormant seed line. Results support the hypothesis that levels of endogenous Pi within the seed influence germinability.
Tactile synthesis and perceptual inverse problems seen from the viewpoint of contact mechanics
Authors: Wang Qi , Hayward Vincent
Published: May 2008

A contact-mechanics analysis was used to explain a tactile illusion engendered by straining the fingertip skin tangentially in a progressive wave pattern resulting in the perception of a moving undulating surface. We derived the strain tensor field induced by a sinusoidal surface sliding on a finger as well as the field created by a tactile transducer array deforming the fingerpad skin by lateral traction. We found that the first field could be well approximated by the second. Our results have several implications. First, tactile displays using lateral skin deformation can generate tactile sensations similar to those using normal skin deformation. Second, a synthesis approach can achieve this result if some constraints on the design of tactile stimulators are met. Third, the mechanoreceptors embedded in the skin must respond to the deviatoric part of the strain tensor field and not to its volumetric part. Finally, many tactile stimuli might represent, for the brain, an inverse problem to be solved, such specific examples of “tactile metameres” are given.
Using haptic cues to aid nonvisual structure recognition
Authors: Jay Caroline , Stevens Robert , Hubbold Roger , Glencross Mashhuda
Published: May 2008

Retrieving information presented visually is difficult for visually disabled users. Current accessibility technologies, such as screen readers, fail to convey presentational layout or structure. Information presented in graphs or images is almost impossible to convey through speech alone. In this paper, we present the results of an experimental study investigating the role of touch (haptic) and auditory cues in aiding structure recognition when visual presentation is missing. We hypothesize that by guiding users toward nodes in a graph structure using force fields, users will find it easier to recognize overall structure. Nine participants were asked to explore simple 3D structures containing nodes (spheres or cubes) laid out in various spatial configurations and asked to identify the nodes and draw their overall structure. Various combinations of haptic and auditory feedback were explored. Our results demonstrate that haptic cues significantly helped participants to quickly recognize nodes and structure. Surprisingly, auditory cues alone did not speed up node recognition; however, when they were combined with haptics both node identification and structure recognition significantly improved. This result demonstrates that haptic feedback plays an important role in enabling people to recall spatial layout.
XML data exchange
Authors: Arenas Marcelo , Libkin Leonid
Published: May 2008

Data exchange is the problem of finding an instance of a target schema, given an instance of a source schema and a specification of the relationship between the source and the target. Theoretical foundations of data exchange have recently been investigated for relational data.

In this article, we start looking into the basic properties of XML data exchange, that is, restructuring of XML documents that conform to a source DTD under a target DTD, and answering queries written over the target schema. We define XML data exchange settings in which source-to-target dependencies refer to the hierarchical structure of the data. Combining DTDs and dependencies makes some XML data exchange settings inconsistent. We investigate the consistency problem and determine its exact complexity.

We then move to query answering, and prove a dichotomy theorem that classifies data exchange settings into those over which query answering is tractable, and those over which it is coNP-complete, depending on classes of regular expressions used in DTDs. Furthermore, for all tractable cases we give polynomial-time algorithms that compute target XML documents over which queries can be answered.
System-wide energy minimization for real-time tasks
Authors: Zhong Xiliang , Xu Cheng-Zhong
Published: May 2008

We present a dynamic voltage scaling (DVS) technique that minimizes system-wide energy consumption for both periodic and sporadic tasks. It is known that a system consists of processors and a number of other components. Energy-aware processors can be run in different speed levels; components like memory and I/O subsystems and network interface cards can be in a standby state when they are active, but idle. Processor energy optimization solutions are not necessarily efficient from the perspective of systems. Current system-wide energy optimization studies are often limited to periodic tasks with heuristics in getting approximated solutions. In this paper, we develop an exact dynamic programming algorithm for periodic tasks on processors with practical discrete speed levels. The algorithm determines the lower bound of energy expenditure in pseudopolynomial time. An approximation algorithm is proposed to provide performance guarantee with a given bound in polynomial running time. Because of their time efficiency, both the optimization and approximation algorithms can be adapted for online scheduling of sporadic tasks with irregular task releases. We prove that system-wide energy optimization for sporadic tasks is NP-hard in the strong sense. We develop (pseudo-) polynomial-time solutions by exploiting its inherent properties.
The security of the Fiat--Shamir scheme in the presence of transient hardware faults
Authors: Voyiatzis Artemios G. , Serpanos Dimitrios N.
Published: May 2008

Implementation cryptanalysis has emerged as a realistic threat for cryptographic systems. It consists of two classes of attacks: fault-injection and side-channel attacks. In this work, we examine the resistance of the Fiat--Shamir scheme to fault-injection attacks, since Fiat--Shamir is a popular scheme for “light” consumer devices, such as smartcards, in a wide range of consumer services. We prove that an existing attack, known as the Bellcore attack, is incomplete. We propose an extension to the protocol that proactively secures Fiat--Shamir systems from the Bellcore attack and we prove its strength. Finally, we introduce a new attack model, which, under stronger assumptions, can derive the secret keys from both the original Fiat--Shamir scheme as well as its proposed extension. Our approach demonstrates that countermeasures for implementation cryptanalysis must be carefully designed and that deployed systems must include appropriate protection mechanisms for all known attacks and be flexible enough to incorporate countermeasures for new ones.
Code compression for performance enhancement of variable-length embedded processors
Authors: Kumar Rajeev , Das Dipankar
Published: May 2008

Most of the work done in the field of code compression pertains to processors with fixed-length instruction encoding. The design of a code-compression scheme for variable-length instruction encodings poses newer design challenges. In this work, we first investigate the scope for code compression on variable-length instruction-set processors whose encodings are already optimized to a certain extent with respect to their usage. For such ISAs instruction boundaries are not known prior to decoding. Another challenging task of designing a code-compression scheme for such ISAs is designing the decompression hardware, which must decompress code postcache so that we gain in performance. We present two dictionary-based code compression schemes. The first algorithm uses a bit-vector; the second one uses reserved instructions to identify code words. We design additional logic for each of the schemes to decompress the code on-the-fly. We test the two algorithms with a variable-length RISC processor. We provide a detailed experimental analysis of the empirical results obtained by extensive simulation-based design space exploration for this system. The optimized decompressor can now execute compressed program faster than the native program. The experiments demonstrate reduction in code size (up to 30%), speed-up (up to 15%), and bus-switching activity (up to 20%). We also implement one decompressor in a hardware description language and synthesize it to illustrate the small overheads associated with the proposed approach.
CBS vision
Authors: Davison Chris
Published: May 2008

Seamus Blackley is head of the Games Department at Creative Artists Agency (CAA), where his role is to define and execute CAA's global strategy for representing many of the world's most respected and successful game creators. Under Blackley's leadership, the Games Department specializes in securing and negotiating game production deals with publishers, financiers, film and television studios, and networks, as well as building and advising development companies to give game designers greater creative and financial control. I interviewed Seamus in December 2007 to discuss physics, social networking, in-game advertising and convergence.
Announcements
Authors: Lee Newton
Published: May 2008

1. First announcement and call for papers for EuroITV 2008 --- July 3--4, 2008 --- Salzburg, Austria --- Sixth European Interactive TV Conference

2. Experimental Playground --- May 8--June 7 --- Sydney, Australia

3. GAME-ON North America 2008 --- August 13--15 , 2008 --- McGill University, Montreal, Canada

4. IADIS International Conference --- Gaming 2008: Design for engaging experience and social interaction --- Amsterdam, The Netherlands --- July 25--27, 2008

5. Immersive Virtual, Mixed, or Augmented Reality Art --- Call for Papers

6. Inclusive Interactive Television: Setting the Agenda for Innovative Research. One-Day Workshop --- In conjunction with EuroITV 2008 --- Salzburg, Austria

7. uxTV 2008 --- First International Conference on Designing Interactive User Experiences for TV and Video --- October 22--24, 2008
Anatomy of high-performance matrix multiplication
Authors: Goto Kazushige , Geijn Robert A. van de
Published: May 2008

We present the basic principles that underlie the high-performance implementation of the matrix-matrix multiplication that is part of the widely used GotoBLAS library. Design decisions are justified by successively refining a model of architectures with multilevel memories. A simple but effective algorithm for executing this operation results. Implementations on a broad selection of architectures are shown to achieve near-peak performance.
An event-driven method to simulate Filippov systems with accurate computing of sliding motions
Authors: Piiroinen Petri T. , Kuznetsov Yuri A.
Published: May 2008

This article describes how to use smooth solvers for simulation of a class of piecewise smooth systems of ordinary differential equations, called Filippov systems, with discontinuous vector fields. In these systems constrained motion along a discontinuity surface (so-called sliding) is possible and requires special treatment numerically. The introduced algorithms are based on an extension to Filippov's method to stabilise the sliding flow together with accurate detection of the entrance and exit of sliding regions. The methods are implemented in a general way in MATLAB and sufficient details are given to enable users to modify the code to run on arbitrary examples. Here, the method is used to compute the dynamics of three example systems, a dry-friction oscillator, a relay feedback system and a model of an oil well drill-string.
Cache efficient bidiagonalization using BLAS 2.5 operators
Authors: Howell Gary W. , Demmel James W. , Fulton Charles T. , Hammarling Sven , Marmol Karen
Published: May 2008

On cache based computer architectures using current standard algorithms, Householder bidiagonalization requires a significant portion of the execution time for computing matrix singular values and vectors. In this paper we reorganize the sequence of operations for Householder bidiagonalization of a general
m
×
n
matrix, so that two (_GEMV) vector-matrix multiplications can be done with one pass of the unreduced trailing part of the matrix through cache. Two new BLAS operations approximately cut in half the transfer of data from main memory to cache, reducing execution times by up to 25 per cent. We give detailed algorithm descriptions and compare timings with the current LAPACK bidiagonalization algorithm.
The role of operating systems in computer forensics
Authors: Huebner Ewa , Henskens Frans
Published: May 2008

Computer forensics is a multidisciplinary field concerned with the examination of computer systems which have been involved in criminal activity, either as an object or a tool of a crime. The aim of the investigator is to find information relevant to the case in question, as well as the chain of events leading to the creation of this information. In other words the questions to be answered are "What incriminating information is present in the system?" and "How did the incriminating information get there?"
A program behavior matching architecture for probabilistic file system forensics
Authors: Xia Ying , Fairbanks Kevin , Owen Henry
Published: May 2008

Even the most secure computing system can be successfully attacked by a sufficiently motivated entity. To investigate the means of entry, the victim machine will come under the scrutiny of forensic analysis tools. In this era where system compromises occur on a regular basis, the design and implementation of operating systems should consider the necessity of computer forensics. Additionally, forensics techniques should take advantage of existing system capabilities such as the journaling feature of the Ext3 file system. With our forensics enabling architecture, we provide a means of using the metadata inherent in the Ext3 file system to reconstruct probable sequences of events that occurred during the journaling process. The reconstruction procedure is achieved by generating program behavior signatures. These signatures allow forensic investigators to perform probabilistic analysis by using information theory models to extract a more significant set of data.
Reconstructing system state for intrusion analysis
Authors: Goel Ashvin , Farhadi Kamran , Po Kenneth , Feng Wu-chang
Published: May 2008

The analysis of a compromised system is a time-consuming and error-prone task today because commodity operating systems provide limited auditing facilities. We have been developing an operating-system level auditing system called Forensix that captures a high-resolution image of all system activities so that detailed analysis can be performed after an attack is detected. The challenge with this approach is that the large amount of audit data generated can overwhelm analysis tools. In this paper, we describe a technique that helps generate a time-line of the state of the system. This technique, based on preprocessing the audit log, simplifies the implementation of the analysis queries and enables running the analysis tools interactively on large data sets.
Software issues in digital forensics
Authors: McDonald J. Todd , Kim Yong C. , Yasinsac Alec
Published: May 2008

Whether we accept it or not, computer systems and the operating systems that direct them are at the heart of major forms of malicious activity. Criminals can use computers as the actual target of their malicious activity (stealing funds electronically from a bank) or use them to support the conduct of criminal activity in general (using a spreadsheet to track drug shipments). In either case, law enforcement needs the ability (when required) to collect evidence from such platforms in a reliable manner that preserves the fingerprints of criminal activity. Though such discussion touches on privacy issues and rules of legal veracity, we focus purely on technological support in this paper. Specifically, we examine and set forth principles of operating system (OS) design that may significantly increase the success of (future) forensic collection efforts. We lay out several OS design attributes that synergistically enhance forensics activities. Specifically, we pose the use of circuit encryption techniques to provide an additional layer of protection above hardware-enforced approaches. We conclude by providing an overarching framework to incorporate these enhancements within the context of OS design.
Remote detection of virtual machine monitors with fuzzy benchmarking
Authors: Franklin Jason , Luk Mark , McCune Jonathan M. , Seshadri Arvind , Perrig Adrian , van Doorn Leendert
Published: May 2008

We study the remote detection of virtual machine monitors (VMMs) across the Internet, and devise
fuzzy benchmarking
as an approach that can successfully detect the presence or absence of a VMM on a remote system.
Fuzzy benchmarking
works by making timing measurements of the execution time of particular code sequences executing on the remote system. The
fuzziness
comes from heuristics which we employ to learn characteristics of the remote system's hardware and VMM configuration. Our techniques are successful despite uncertainty about the remote machine's hardware configuration.
Passive network forensics
Authors: McHugh John , McLeod Ron , Nagaonkar Vagishwari
Published: May 2008

Passive monitoring of the data entering and leaving an enterprise network can support a number of forensic objectives. We have developed analysis techniques for NetFlow data that use behavioural identification and can confirm individual host roles and behaviours expressed as connection patterns. By looking at the way a given machine interacts with others, it is often possible to determine the role of the machine based solely on the network data. Host behaviours as characterized by NetFlow data are not stationary. Evolutionary changes occur as the result of new applications, computational and communications paradigms. Compromised machines often undergo changes in behaviour that range from subtle to dramatic. We use behavioural changes to identify role shifts and to trace the malicious or unintentional propagation of that change to other machines. Observed behavioural characteristics from over a year of traffic captures containing ordinary behaviours as well as a variety of compromises of interest are presented as examples for the forensics practitioner or researcher.
Chairs' report on Twenty-First ACM Symposium on Operating Systems Principles
Authors: Bressoud Thomas C. , Kaashoek M. Frans
Published: May 2008

The 21st ACM Symposium on Operating Systems Principles (SOSP 2007) was held at the Skamania Lodge in Stevenson, Washington, USA from October 14th to October 17th 2007. The conference site is located in the Columbia River Gorge National Scenic Area, a spectacular canyon along the border between Oregon and Washington States in the Pacific Northwest, where the Columbia River cuts through the Cascades mountain range. Delegates were treated to breathtaking views of the gorge and mountains from the lodge's rustic and warm common areas and the weather cooperated for the arrival and early parts of the conference, though the rains came in force in the latter part of the conference.
Report on the 2007 SOSP shadow program committee
Authors: Isaacs Rebecca
Published: May 2008

Since its recent establishment, the European chapter of SIGOPS (EuroSys) has initiatied a number of activities to "increase the visibility and quality of systems research in Europe". This report describes one such activity, a shadow program committee for SOSP that was open to junior systems researchers based anywhere in the world. Feedback from the participants confirms that the experience was worthwhile and enjoyable, and it is my belief that a shadow PC also has long term benefits for the wider systems research community, as explained further below.
Policies for the SIGOPS Hall of Fame Award
Authors: Mogul Jeffrey C.
Published: May 2008

The SIGOPS Hall of Fame Award was established in 2005 to recognize "the most influential Operating Systems papers" of the past. See http://www.sigops.org/awards/hall-of-fame.html for the Web page that describes the award.
Session scribe notes for Twenty-First ACM Symposium on Operating Systems Principles
Authors: Bressoud Thomas C.
Published: May 2008

The following article is divided into nine sections, one for each of the sessions presented at SOSP 2007. For each session, two student volunteers took notes at the conference, capturing the questions and answers following each of the papers presented in that session. Note that the session order follows the program as given at the conference which, due to logistic necessity, differs slightly from the order in the proceedings.
Effect of low pH on single skeletal muscle myosin mechanics and kinetics
Authors: Debold E. P. , Beck S. E. , Warshaw D. M.
Published: May 2008

Acidosis (low pH) is the oldest putative agent of muscular fatigue, but the molecular mechanism underlying its depressive effect on muscular performance remains unresolved. Therefore, the effect of low pH on the molecular mechanics and kinetics of chicken skeletal muscle myosin was studied using in vitro motility (IVM) and single molecule laser trap assays. Decreasing pH from 7.4 to 6.4 at saturating ATP slowed actin filament velocity ( Vactin) in the IVM by 36%. Single molecule experiments, at 1 μM ATP, decreased the average unitary step size of myosin ( d) from 10 ± 2 nm (pH 7.4) to 2 ± 1 nm (pH 6.4). Individual binding events at low pH were consistent with the presence of a population of both productive (average d = 10 nm) and nonproductive (average d = 0 nm) actomyosin interactions. Raising the ATP concentration from 1 μM to 1 mM at pH 6.4 restored d (9 ± 3 nm), suggesting that the lifetime of the nonproductive interactions is solely dependent on the [ATP]. Vactin, however, was not restored by raising the [ATP] (1–10 mM) in the IVM assay, suggesting that low pH also prolongs actin strong binding ( ton). Measurement of ton as a function of the [ATP] in the single molecule assay suggested that acidosis prolongs ton by slowing the rate of ADP release. Thus, in a detachment limited model of motility (i.e., Vactin ∼ d/ ton), a slowed rate of ADP release and the presence of nonproductive actomyosin interactions could account for the acidosis-induced decrease in Vactin, suggesting a molecular explanation for this component of muscular fatigue.
Endothelial cell respiration is affected by the oxygen tension during shear exposure: role of mitochondrial peroxynitrite
Authors: Jones Charles I. , Han Zhaosheng , Presley Tennille , Varadharaj Saradhadevi , Zweier Jay L. , Ilangovan Govindasamy , Alevriadou B. Rita
Published: May 2008

Cultured vascular endothelial cell (EC) exposure to steady laminar shear stress results in peroxynitrite (ONOO−) formation intramitochondrially and inactivation of the electron transport chain. We examined whether the “hyperoxic state” of 21% O2, compared with more physiological O2 tensions (Po2), increases the shear-induced nitric oxide (NO) synthesis and mitochondrial superoxide (O2·−) generation leading to ONOO− formation and suppression of respiration. Electron paramagnetic resonance oximetry was used to measure O2 consumption rates of bovine aortic ECs sheared (10 dyn/cm2, 30 min) at 5%, 10%, or 21% O2 or left static at 5% or 21% O2. Respiration was inhibited to a greater extent when ECs were sheared at 21% O2 than at lower Po2 or left static at different Po2. Flow in the presence of an endothelial NO synthase (eNOS) inhibitor or a ONOO− scavenger abolished the inhibitory effect. EC transfection with an adenovirus that expresses manganese superoxide dismutase in mitochondria, and not a control virus, blocked the inhibitory effect. Intracellular and mitochondrial O2·− production was higher in ECs sheared at 21% than at 5% O2, as determined by dihydroethidium and MitoSOX red fluorescence, respectively, and the latter was, at least in part, NO-dependent. Accumulation of NO metabolites in media of ECs sheared at 21% O2 was modestly increased compared with ECs sheared at lower Po2, suggesting that eNOS activity may be higher at 21% O2. Hence, the hyperoxia of in vitro EC flow studies, via increased NO and mitochondrial O2·− production, leads to enhanced ONOO− formation intramitochondrially and suppression of respiration.
Hypercontractility and impaired sildenafil relaxations in the BKCachannel deletion model of erectile dysfunction
Authors: Werner Matthias E. , Meredith Andrea L. , Aldrich Richard W. , Nelson Mark T.
Published: May 2008

Erectile dysfunction (ED) can be elicited by a variety of pathogenic factors, particularly impaired formation of and responsiveness to nitric oxide (NO) and the downstream effectors soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase I (PKGI). One important target of PKGI in smooth muscle is the large-conductance, Ca2+-activated potassium (BKCa) channel. In our previous report ( 42 ), we demonstrated that deletion of the BKCachannel in mice induced force oscillations and led to reduced nerve-evoked relaxations and ED. In the current study, we used this ED model to explore the role of the BKCachannel in the NO/sGC/PKGI pathway. Electrical field stimulation (EFS)-induced contractions of corpus cavernosum smooth muscle strips were significantly enhanced in the absence of BKCachannel function. In strips precontracted with phenylephrine, EFS-induced relaxations were converted to contractions by inhibition of sGC, and this was further enhanced by loss of BK channel function. Sildenafil-induced relaxations were decreased to a similar extent by inhibition of sGC or BKCachannels. At concentrations >1 μM, sildenafil caused relaxations independent of inhibition of sGC or BKCachannels. Sildenafil did not affect the enhanced force oscillations that were induced by the loss of BKCachannel function. Yet, these oscillations could be completely eliminated by blocking L-type voltage-dependent Ca2+channels (VDCCs). These results suggest that therapeutically relevant concentrations of sildenafil act through cGMP and BKCachannels, and loss of BKCachannel function leads to hypercontractility, which depends on VDCCs and cannot be modified by the cGMP pathway.
Differential effects of maternal nutrient restriction through pregnancy on kidney development and later blood pressure control in the resulting offspring
Authors: Brennan K. A. , Kaufman S. , Reynolds S. W. , McCook B. T. , Kan G. , Christiaens I. , Symonds M. E. , Olson D. M.
Published: May 2008

The mechanisms whereby maternal nutritional manipulation through pregnancy result in altered blood pressure in the offspring may include changes in fetal and newborn and adult renal prostaglandin (PG) synthesis, metabolism, and receptor expression. Since the postnatal effects of nutrient restriction on the renal PG synthesis and receptor system during nephrogenesis in conjunction with nephron numbers and blood pressure have not been evaluated in the rat, the present study examined the effect of reducing maternal food intake by 50% of ad libitum through pregnancy on young male rats. Six control-fed mothers and eight nutrient-restricted pregnant rats with single litter mates were used at each sampling time point, most of which occurred during nephrogenesis. Offspring of nutrient-restricted dams were lighter from birth to 3 days. This was accompanied by reduced PGE2, with smaller kidneys up to 14 days. Nutrient restriction also decreased mRNA expression of the PG synthesis enzyme, had little effect on the PG receptors, and increased mRNA expression of the degradation enzyme during nephrogenesis and the glucocorticoid receptor in the adult kidney. These mRNA changes were normally accompanied by similar changes in protein. Nephron number was also reduced from 7 days up to adulthood when blood pressure (measured by telemetry) did not increase as much as in control offspring during the dark, active period. In conclusion, maternal nutrient restriction suppressed renal PG concentrations in the offspring, and this was associated with suppressed kidney growth and development and decreased blood pressure.
Salmon calcitonin reduces food intake through changes in meal sizes in male rhesus monkeys
Authors: Bello Nicholas T. , Kemm Matthew H. , Moran Timothy H.
Published: May 2008

Amylinergic mechanisms are believed to be involved in the control of appetite. This study examined the effects of the amylin agonist, salmon calcitonin, on food intake and meal patterns in adult male rhesus monkeys. Fifteen minutes before the onset of their 6-h daily feeding period, monkeys received intramuscular injections of various doses of salmon calcitonin (0.032, 0.056, 0.1, 0.32, and 1 μg/kg) or saline. Salmon calcitonin dose dependently reduced total daily and hourly food intake, with significant decreases at the 0.1, 0.32, and 1 μg/kg doses. Daily food intake was reduced by ∼35%, 62%, and 96%, at these doses, respectively. An analysis of meal patterns revealed that size of the first meal was significantly reduced across the dose range of 0.056 to 1 μg/kg, while average meal size was reduced with the 0.32 and 1 μg/kg doses. Meal number was only affected at the 1 μg/kg dose. Repeated 5-day administration of the 0.1 μg/kg dose resulted in a reduction in daily food intake only on injection day 2, while significant reductions in food intake were observed on all five injection days with a 0.32 μg/kg dose. Daily food intake was also reduced for 1 day after the termination of the 5-day injections of the 0.32 μg/kg salmon calcitonin dose. These sustained reductions in intake were expressed through decreases in meal size. These data demonstrate that salmon calcitonin acutely and consistently decreases food intake mainly through reductions in meal sizes in nonhuman primates.
Immune-to-brain signaling and central prostaglandin E2synthesis in fasted rats with altered lipopolysaccharide-induced fever
Authors: Inoue Wataru , Somay Gokce , Poole Stephen , Luheshi Giamal N.
Published: May 2008

Acute starvation attenuates the fever response to pathogens in several mammalian species. The underlying mechanisms responsible for this effect are not fully understood but may involve a compromised immune and/or thermoregulatory function, both of which are prerequisites for fever generation. In the present study, we addressed whether the impaired innate immune response contributes to the reported attenuation of the fever response in fasted rats during LPS-induced inflammation. Animals fasted for 48 h exhibited a significant and progressive hypothermia prior to drug treatment. An intraperitoneal injection of LPS (100 μg/kg) resulted in a significantly attenuated fever in the fasted animals compared with the fed counterparts. This attenuation was accompanied by the diminution in the concentration of some [TNF and IL-1 receptor antagonist (RA)] but not all (IL-1β and IL-6) of the plasma cytokines normally elevated in association with the fever response. Nevertheless, fasting had no effect on the LPS-induced inflammatory responses at the level of the brain, as assessed by mRNA expressions of inhibitory factor(I)-κB, suppressor of cytokine signaling (SOCS3), IL-1β, cyclooxygenase (COX)-2, and microsomal PGE synthase (mPGES)-1 in the hypothalamus, as well as by PGE2elevations in the cerebrospinal fluid. In contrast, fasting significantly attenuated the fever response to central PGE2injection. These results show that fasting does not alter the febrigenic signaling from the periphery to the brain important for central PGE2synthesis but does affect thermoregulatory mechanisms downstream of and/or independent of central PGE2action.
Low salt intake increases adenosine type 1 receptor expression and function in the rat proximal tubule
Authors: Kulick Aaron , Panico Carolina , Gill Pritmohinder , Welch William J.
Published: May 2008

Adenosine mediates Na+reabsorption in the proximal tubule (PT) and other segments by activating adenosine type 1 receptors (A1-AR). We tested the hypothesis that A1-AR in the PT is regulated by salt intake and participates in the kidney adaptation to changes in salt intake. Absolute fluid reabsorption ( Jv) was measured by direct in vivo microperfusion and recollection in rats maintained on low (LS; 0.03% Na, wt/wt)-, normal (NS; 0.3% Na)-, and high-salt (HS; 3.0% Na) diets for 1 wk. The effect of microperfusion of BG9719 a highly selective inhibitor of A1-ARs or adenosine deaminase (AD), which metabolizes adenosine, was measured in each group. Jvwas higher in PT from LS rats (LA: 2.8 ± 0.2 vs. NS: 2.1 ± 0.2 nl·min−1·mm−1, P < 0.001). Jvin HS rats was not different from NS. BG9719 reduced Jvin LS rats by 66 ± 6% (LS: 2.8 ± 0.2 vs LS+CVT: 1.3 ± 0.3 nl·min−1·mm−1, P < 0.001), which was greater than its effect in NS (45 ± 4%) or HS (41 ± 4%) rats. AD reduced Jvsimilarly, suggesting that A1-ARs are activated by local production of adenosine. Expression of A1-AR mRNA and protein was higher ( P < 0.01) in microdissected PTs in LS rats compared with NS and HS. We conclude that A1-ARs in the PT are increased by low salt intake and that A1-AR participates in the increased PT reabsorption of solute and fluid in response to low salt intake.
Roles of PINCH-2 in regulation of glomerular cell shape change and fibronectin matrix deposition
Authors: Shi Xiaohua , Qu Hong , Kretzler Matthias , Wu Chuanyue
Published: May 2008

The PINCH-1-integrin-linked kinase (ILK)-α-parvin (PIP) complex plays important roles in the regulation of glomerular cell behavior, including podocyte shape change, apoptosis, and mesangial fibronectin matrix deposition. In this study, we show that PINCH-2, a protein that is structurally related to PINCH-1 but encoded by a different gene, is coexpressed with PINCH-1 in podocytes. Treatment of podocytes with transforming growth factor (TGF)-β1 elevated the level of PINCH-2, resulting in increased association of PINCH-2 with ILK and α-parvin and concomitant displacement of PINCH-1 from the PIP complex. To gain insights into the functional consequences of elevated PINCH-2 expression, we overexpressed PINCH-2 in podocytes by infection with an adenovirus encoding PINCH-2. Overexpression of PINCH-2 resulted in displacement of PINCH-1 from the PIP complex and compromised podocyte spreading. The PINCH-2-mediated displacement of PINCH-1, however, did not prompt apoptosis. Interestingly, the effect of PINCH-2 on podocyte spreading depends on differentiation status, as overexpression of PINCH-2 in podocytes that were not fully differentiated did not alter cell spreading. Finally, we show that overexpression of PINCH-2 in mesangial cells resulted in displacement of PINCH-1 from the PIP complex but impaired neither mesangial cell spreading nor fibronectin matrix deposition. These studies suggest that PINCH-2 can substitute for PINCH-1 in at least certain processes in glomerular cells (e.g., podocyte survival signaling and mesangial fibronectin matrix deposition), albeit that an aberrantly high level of PINCH-2 may contribute to TGF-β1-induced alteration in podocyte shape modulation.
A novel missense mutation in SLC34A3 that causes hereditary hypophosphatemic rickets with hypercalciuria in humans identifies threonine 137 as an important determinant of sodium-phosphate cotransport in NaPi-IIc
Authors: Jaureguiberry Graciana , Carpenter Thomas O. , Forman Stuart , Jüppner Harald , Bergwitz Clemens
Published: May 2008

The present study describes two novel compound heterozygous mutations, c.410C>T(p.T137M) (T137M) on the maternal and g.4225_50del on the paternal allele of SLC34A3, in a previously reported male with hereditary hypophosphatemic rickets with hypercalciuria (HHRH) and recurrent kidney stones (Chen C, Carpenter T, Steg N, Baron R, Anast C. Pediatrics 84: 276–280, 1989). For functional analysis in vitro, we generated expression plasmids encoding enhanced green fluorescence protein (EGFP) concatenated to the NH2terminus of wild-type or mutant human type IIc Na-Picotransporter (NaPi-IIc), i.e., EGFP-hNaPi-IIc, EGFP-[M137]hNaPi-IIc, or EGFP-[Stop446]hNaPi-IIc. The V446Stop mutant showed complete loss of expression and function when assayed for apical patch expression in opossum kidney (OK) cells and sodium-dependent33P uptake into Xenopus laevis oocytes. Conversely, EGFP-[M137]hNaPi-IIc was inserted into apical patches of OK cells and into oocyte membranes. However, when quantified by confocal microscopy, surface fluorescence was reduced to 40% compared with wild-type. After correction for surface expression, the rate of33P uptake by oocytes mediated by EGFP-[M137]hNaPi-IIc was decreased by an additional 60%. The resulting overall reduction of function of this NaPi-IIc mutant to 16%, taken together with complete loss of expression and function of g.4225_50del(V446Stop), thus appears to be sufficient to explain the phenotype in our patient. Furthermore, the stoichiometric ratio of22Na and33P uptake was increased to 7.1 ± 3.65 for EGFP-[M137]hNaPi-IIc compared with wild-type. Two-electrode studies indicate that EGFP-[M137]hNaPi-IIc is nonelectrogenic but displayed a significant phosphate-independent inward-rectified sodium current, which appears to be insensitive to phosphonoformic acid. M137 thus may uncouple sodium-phosphate cotransport, suggesting that this amino acid residue has an important functional role in human NaPi-IIc.
Decreased maximal heart rate with aging is related to reduced β-adrenergic responsiveness but is largely explained by a reduction in intrinsic heart rate
Authors: Christou Demetra D. , Seals Douglas R.
Published: May 2008

A decrease in maximal exercise heart rate (HRmax) is a key contributor to reductions in aerobic exercise capacity with aging. However, the mechanisms involved are incompletely understood. We sought to gain insight into the respective roles of intrinsic heart rate (HRint) and chronotropic β-adrenergic responsiveness in the reductions in HRmax with aging in healthy adults. HRmax (Balke treadmill protocol to exhaustion), HRint (HR during acute ganglionic blockade with intravenous trimethaphan), and chronotropic β-adrenergic responsiveness (increase in HR with incremental intravenous infusion of isoproterenol during ganglionic blockade) were determined in 15 older (65 ± 5 yr) and 15 young (25 ± 4 yr) healthy men. In the older men, HRmax was lower (162 ± 9 vs. 191 ± 11 beats/min, P < 0.0001) and was associated with a lower HRint (58 ± 7 vs. 83 ± 9 beats/min, P < 0.0001) and chronotropic β-adrenergic responsiveness (0.094 ± 0.036 vs. 0.154 ± 0.045 ΔHR/[isoproterenol]: P < 0.0001). Both HRint ( r = 0.87, P < 0.0001) and chronotropic β-adrenergic responsiveness ( r = 0.61, P < 0.0001) were positively related to HRmax. Accounting for the effects of HRint and chronotropic β-adrenergic responsiveness reduced the age-related difference in HRmax by 83%, rendering it statistically nonsignificant ( P = 0.2). Maximal oxygen consumption was lower in the older men (34.9 ± 8.1 vs. 48.6 ± 6.7 ml·kg−1·min−1, P < 0.0001) and was positively related to HRmax ( r = 0.62, P < 0.0001), HRint ( r = 0.51, P = 0.002), and chronotropic β-adrenergic responsiveness ( r = 0.47, P = 0.005). Our findings indicate that, together, reductions in HRint and chronotropic responsiveness to β-adrenergic stimulation largely explain decreases in HRmax with aging, with the reduction in HRint playing by far the greatest role.
Intrinsic and Extrinsic Light Responses in Melanopsin-Expressing Ganglion Cells During Mouse Development
Authors: Schmidt Tiffany M. , Taniguchi Kenichiro , Kofuji Paulo
Published: May 2008

Melanopsin (Opn4) is a photopigment found in a subset of retinal ganglion cells (RGCs) that project to various brain areas. These neurons are intrinsically photosensitive (ipRGCs) and are implicated in nonimage-forming responses to environmental light such as the pupillary light reflex and circadian entrainment. Recent evidence indicates that ipRGCs respond to light at birth, but questions remain as to whether and when they undergo significant functional changes. We used bacterial artificial chromosome transgenesis to engineer a mouse line in which enhanced green fluorescent protein (EGFP) is expressed under the control of the melanopsin promoter. Double immunolabeling for EGFP and melanopsin demonstrates their colocalization in ganglion cells of mutant mouse retinas. Electrophysiological recordings of ipRGCs in neonatal mice (postnatal day 0 [P0] to P7) demonstrated that these cells responded to light with small and sluggish depolarization. However, starting at P11 we observed ipRGCs that responded to light with a larger and faster onset (<1 s) and offset (<1 s) depolarization. These faster, larger depolarizations were observed in most ipRGCs by early adult ages. However, on application of a cocktail of synaptic blockers, we found that all cells responded to light with slow onset (>2.5 s) and offset (>10 s) depolarization, revealing the intrinsic, melanopsin-mediated light responses. The extrinsic, cone/rod influence on ipRGCs correlates with their extensive dendritic stratification in the inner plexiform layer. Collectively, these results demonstrate that ipRGCs make use of melanopsin for phototransduction before eye opening and that these cells further integrate signals derived from the outer retina as the retina matures.
Naso-Temporal Asymmetry for Signals Invisible to the Retinotectal Pathway
Authors: Bompas Aline , Sterling Thomas , Rafal Robert D. , Sumner Petroc
Published: May 2008

Monocular viewing conditions show an asymmetry between stimuli presented in the temporal and nasal visual fields in their efficiency for automatically triggering eye saccades and grasping attention. For instance, observers free to make a saccade to one of two stimuli presented together orient preferentially to the temporal stimulus. Such naso-temporal asymmetry (NTA) has been assumed to reflect the asymmetry in the retinotectal pathway to the superior colliculus. We tested this hypothesis using S cone stimuli, which are invisible to the magnocellular and retinotectal pathways. The observed NTA in choice saccades to bilateral stimuli was no less present for S cone stimuli than for luminance stimuli. Additionally, the amplitude of the NTA can be enhanced when S cone signals are added to luminance signals. These results suggest that behavioral NTA in humans is not diagnostic of retinotectal mediation. Furthermore, we found no asymmetries in latency, suggesting that the NTA in saccade choice does not originate simply from a bottom-up asymmetry in any low level visual pathways.