bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal Structure of Naphthalene Dioxygenase: Side-on Binding of Dioxygen to Iron
Authors: Karlsson Andreas , Parales Juanito V. , Parales Rebecca E. , Gibson David T. , Eklund Hans , Ramaswamy S.
Published: February 2003

Binding of oxygen to iron is exploited in several biological and chemical processes. Although computational and spectroscopic results have suggested side-on binding, only end-on binding of oxygen to iron has been observed in crystal structures. We have determined structures of naphthalene dioxygenase that show a molecular oxygen species bound to the mononuclear iron in a side-on fashion. In a complex with substrate and dioxygen, the dioxygen molecule is lined up for an attack on the double bond of the aromatic substrate. The structures reported here provide the basis for a reaction mechanism and for the high stereospecificity of the reaction catalyzed by naphthalene dioxygenase.
Toll Pathway-Dependent Blockade of CD4
+
CD25
+
T Cell-Mediated Suppression by Dendritic Cells
Authors: Pasare Chandrashekhar , Medzhitov Ruslan
Published: February 2003

Toll-like receptors (TLRs) control activation of adaptive immune responses by antigen-presenting cells (APCs). However, initiation of adaptive immune responses is also controlled by regulatory T cells (T
R
cells), which act to prevent activation of autoreactive T cells. Here we describe a second mechanism of immune induction by TLRs, which is independent of effects on costimulation. Microbial induction of the Toll pathway blocked the suppressive effect of CD4
+
CD25
+
T
R
cells, allowing activation of pathogen-specific adaptive immune responses. This block of suppressor activity was dependent in part on interleukin-6, which was induced by TLRs upon recognition of microbial products.
Single-Neuron Activity and Tissue Oxygenation in the Cerebral Cortex
Authors: Thompson Jeffrey K. , Peterson Matthew R. , Freeman Ralph D.
Published: February 2003

Blood oxygen level–dependent functional magnetic resonance imaging uses alterations in brain hemodynamics to infer changes in neural activity. Are these hemodynamic changes regulated at a spatial scale capable of resolving functional columns within the cerebral cortex? To address this question, we made simultaneous measurements of tissue oxygenation and single-cell neural activity within the visual cortex. Results showed that increases in neuronal spike rate were accompanied by immediate decreases in tissue oxygenation. We used this decrease in tissue oxygenation to predict the orientation selectivity and ocular dominance of neighboring neurons. Our results establish a coupling between neural activity and oxidative metabolism and suggest that high-resolution functional magnetic resonance imaging may be used to localize neural activity at a columnar level.
Taming of a Poison: Biosynthesis of the NiFe-Hydrogenase Cyanide Ligands
Authors: Reissmann Stefanie , Hochleitner Elisabeth , Wang Haofan , Paschos Athanasios , Lottspeich Friedrich , Glass Richard S. , Böck August
Published: February 2003

NiFe-hydrogenases have an Ni-Fe site in which the iron has one CO and two CN groups as ligands. Synthesis of the CN ligands requires the activity of two hydrogenase maturation proteins: HypF and HypE. HypF is a carbamoyltransferase that transfers the carbamoyl moiety of carbamoyladenylate to the COOH-terminal cysteine of HypE and thus forms an enzyme-thiocarbamate. HypE dehydrates the
S
-carbamoyl moiety in an adenosine triphosphate–dependent process to yield the enzyme thiocyanate. Chemical model reactions corroborate the feasibility of this unprecedented biosynthetic route and show that thiocyanates can donate CN to iron. This finding underscores a striking parallel between biochemistry and organometallic chemistry in the formation of an iron-cyano complex.
INTERPLANETARY AND SOLAR PLASMA PARAMETERS OF THE 14 JULY 2000 GROUND LEVEL ENHANCEMENT
Authors: AL-THOYAIB S. S.
Published: February 2003

The ground level enhancement (GLE) of 14 July 2000 observed in the cosmic ray intensity has been examined. The event was recorded only by neutron monitors. It has a complex intensity-time structure. The northern hemisphere stations (Thule, Goose Bay, and Oulu) recorded abrupt increases earlier by 10 minutes than those in the southern hemisphere. Due to the difference in sensitivity at rigidity less than ~3 GV, the considered detectors recorded different increases in count rates relative to galactic cosmic ray background. This paper presents the study of GLE associated with the X5.7 solar flare. The rapid change of arriving particles were anisotropic during the onset of the event; it become isotropic during the declining phase of the event, where only low energy protons remained. In addition, the observations of energetic solar particles and interplanetary parameters have been examined.
IP LOOKUP BY BINARY SEARCH ON PREFIX LENGTH
Authors: KIM KUN SUK , SAHNI SARTAJ
Published: February 2003

Waldvogel et al.9 have proposed a collection of hash tables (CHT) organization for an IP router table. Each hash table in the CHT contains prefixes of the same length together with markers for longer-length prefixes. IP lookup can be done with O( log ldist) hash-table searches, where ldist is the number of distinct prefix-lengths (also equal to the number of hash tables in the CHT). Srinivasan and Varghese8 have proposed the use of controlled prefix-expansion to reduce the value of ldist. The details of their algorithm to reduce the number of lengths are given in [7]. The complexity of this algorithm is O(nW2), where n is the number of prefixes, and W is the length of the longest prefix. The algorithm of [7] does not minimize the storage required by the prefixes and markers for the resulting set of prefixes. We develop an algorithm that minimizes storage requirement but takes O(nW3 + kW4) time, where k is the desired number of distinct lengths. Also, we propose improvements to the heuristic of [7].
ON LOCALITY OF DOMINATING SET IN AD HOC NETWORKS WITH SWITCH-ON/OFF OPERATIONS
Authors: WU JIE , DAI FEI
Published: February 2003

Efficient routing among a set of mobile hosts is one of the most important functions in ad hoc wireless networks. Routing based on a connected dominating set is a promising approach, where the search space for a route is reduced to the hosts in the set. A set is dominating if all the hosts in the system are either in the system are either in the set or neighbors of hosts in the set. In this paper, we first review a distributed formation of a connected dominating set called marking process and dominating-set-based routing. Then we propose several ways to reduce the size of the dominating set and study the locality of dominating set and study the locality of dominating set in ad hoc wireless networks with switch-on/off operations. Results show that the dominating set derived from the marking process exhibits good locality properties; i.e., the change of a host status, gateway (dominating) or non-gateway (dominated), affects only the status of hosts in a restricted vicinity. In addition, locality of host status updated is also verified through simulation.
IDENTIFYING FAULTY NODES IN WIRELESS SENSOR NETWORKS
Authors: Bordim Jacir L. , Hsu Frank , Nakano Koji
Published: February 2003

A Wireless Sensor Network (WSN) is a distributed system populated by a base station and a number of wireless sensor nodes. The main task of the sensor nodes in a WSN is to monitor the environment, collect data, and eventually transfer the sensed data to the base station. For reliable monitoring, the sensor nodes must be in close proximity to the physical events. The sensor nodes are tiny devices that operate on a frugal energy budget and may fail dua to, among other causes, power depletion, catastrophic events, and external damages. When the location and the state (faulty or fault-free) of each sensors in the network is known, the faulty sensors can be repaired/recharged or new sensors could be added to the affected areas so as to maintain accurate monitoring. The main contribution of this work is to provide energy-efficient means to identify the location of the faulty sensor nodes in the WSN. Consider a WSN populated by n wireless sensor nodes which are arranged in a two-dimensional grid of size [Formula: see text]. Let q and k denote the number of fault-free and faulty nodes in the WSN, respectively. The task of identifying the faulty nodes and reporting the location of these faulty sensors to the base station can be completed in O(α + r2) time slots and none of the sensors need to awake for more than O( log log α) time slots, where α = min (q,k) and r is the transmission range of the sensor nodes.
Wireless Sensor Networks with Energy Efficient Organization
Authors: Cardei Mihaela , MacCallum David , Cheng Maggie Xiaoyan , Min Manki , Jia Xiaohua , Li Deying , Du Ding-Zhu
Published: February 2003

A critical aspect of applications with wireless sensor networks is network lifetime. Battery-powered sensors are usable as long as they can communicate captured data to a processing node. Sensing and communications consume energy, therefore judicious power management and scheduling can effectively extend the operational time. One important class of wireless sensor applications of deployment of large number of sensors in an area for environmental monitoring. The data collected by the sensors is sent to a central node for processing. In this paper we propose an efficient method to achieve energy savings by organizing the sensor nodes into a maximum number of disjoint dominating sets (DDS) which are activated successively. Only the sensors from the active set are responsible for monitoring the target area and for disseminating the collected data. All other nodes are into a sleep mode, characterized by a low energy consumption. We define the maximum disjoint dominating sets problem and we design a heuristic that computes the sets. Theoretical analysis and performance evaluation results are presented to verify our approach.
k-DIAMETERS OF THE HYPER-L SHAPE TILE
Authors: HWANG F. K. , LIN B. C.
Published: February 2003

The triple-loop network associated with the hyper-L shape has been shown to have the best diameter among all triple-loop networks so far. In this paper we study the k- diameters of this network. In particular, we construct three node-disjoint shortest paths no longer than the diameter plus 2 for any pair of nodes.
PERFORMANCE EVALUATION OF ADAPTIVE MEDIA ACCESS CONTROL PROTOCOLS FOR PERVASIVE WIRELESS NETWORKS
Authors: LIM ALVIN , MOK KUI
Published: February 2003

As pervasive and high-density wireless networks become increasingly common, it is critical to address the problems of intermittent disconnection, high error rate and collision that cause degradation in the performance of wireless media access control protocols, such as slotted ALOHA Time Division Multiple Access (slotted ALOHA/TDMA) and Direct Sequence Code Division Multiple Access (DS/CDMA). We propose adaptive techniques for improving performance of media access protocols through awareness of the mobile communication environment. These techniques involve detection of intermittent disconnection, high error rates, and collisions. Upon detection and notification of these conditions by snooping devices, the media access control layer adapts its operation and synchronization accordingly to reduce delay and loss of bandwidth. Results from our simulation studies show that adaptive TDMA improves performance by as much as 12 times over basic TDMA and adaptive CDMA improves by as much as 4 times over basic CDMA in wireless network with high density cells. Overall, adaptive CDMA still performs better than adaptive TDMA by about 4 times.
A Quantified Sensitivity Measure for Multilayer Perceptron to Input Perturbation
Authors: Zeng Xiaoqin , Yeung Daniel S.
Published: February 2003

The sensitivity of a neural network's output to its input perturbation is an important issue with both theoretical and practical values. In this article, we propose an approach to quantify the sensitivity of the most popular and general feedforward network: multilayer perceptron (MLP). The sensitivity measure is defined as the mathematical expectation of output deviation due to expected input deviation with respect to overall input patterns in a continuous interval. Based on the structural characteristics of the MLP, a bottom-up approach is adopted. A single neuron is considered first, and algorithms with approximately derived analytical expressions that are functions of expected input deviation are given for the computation of its sensitivity. Then another algorithm is given to compute the sensitivity of the entire MLP network. Computer simulations are used to verify the derived theoretical formulas. The agreement between theoretical and experimental results is quite good. The sensitivity measure can be used to evaluate the MLP's performance.
Variational Mixture of Bayesian Independent Component Analyzers
Authors: Choudrey R. A. , Roberts S. J.
Published: February 2003

There has been growing interest in subspace data modeling over the past few years. Methods such as principal component analysis, factor analysis, and independent component analysis have gained in popularity and have found many applications in image modeling, signal processing, and data compression, to name just a few. As applications and computing power grow, more and more sophisticated analyses and meaningful representations are sought. Mixture modeling methods have been proposed for principal and factor analyzers that exploit local gaussian features in the subspace manifolds. Meaningful representations may be lost, however, if these local features are nongaussian or discontinuous. In this article, we propose extending the gaussian analyzers mixture model to an independent component analyzers mixture model. We employ recent developments in variational Bayesian inference and structure determination to construct a novel approach for modeling nongaussian, discontinuous manifolds. We automatically determine the local dimensionality of each manifold and use variational inference to calculate the optimum number of ICA components needed in our mixture model. We demonstrate our framework on complex synthetic data and illustrate its application to real data by decomposing functional magnetic resonance images into meaningful—and medically useful—features.
Linear Geometric ICA: Fundamentals and Algorithms
Authors: Theis Fabian J. , Jung Andreas , Puntonet Carlos G. , Lang Elmar W.
Published: February 2003

Geometric algorithms for linear independent component analysis (ICA) have recently received some attention due to their pictorial description and their relative ease of implementation. The geometric approach to ICA was proposed first by Puntonet and Prieto (1995). We will reconsider geometric ICA in a theoretic framework showing that fixed points of geometric ICA fulfill a geometric convergence condition (GCC), which the mixed images of the unit vectors satisfy too. This leads to a conjecture claiming that in the nongaussian unimodal symmetric case, there is only one stable fixed point, implying the uniqueness of geometric ICA after convergence. Guided by the principles of ordinary geometric ICA, we then present a new approach to linear geometric ICA based on histograms observing a considerable improvement in separation quality of different distributions and a sizable reduction in computational cost, by a factor of 100, compared to the ordinary geometric approach. Furthermore, we explore the accuracy of the algorithm depending on the number of samples and the choice of the mixing matrix, and compare geometric algorithms with classical ICA algorithms, namely, Extended Infomax and FastICA. Finally, we discuss the problem of high-dimensional data sets within the realm of geometrical ICA algorithms.
SMO Algorithm for Least-Squares SVM Formulations
Authors: Keerthi S. S. , Shevade S. K.
Published: February 2003

This article extends the well-known SMO algorithm of support vector machines (SVMs) to least-squares SVM formulations that include LS-SVM classification, kernel ridge regression, and a particular form of regularized kernel Fisher discriminant. The algorithm is shown to be asymptotically convergent. It is also extremely easy to implement. Computational experiments show that the algorithm is fast and scales efficiently (quadratically) as a function of the number of examples.
Pentagon surface wipe sampling health risk assessment
Authors: Gaborek Bonnie J , Mullikin James M , Pitrat Tony , Cummings Laurie , May Lisa M
Published: February 2003

Within hours after the terrorist attack on the Pentagon on September 11, 2001, an extensive sampling effort was initiated within the building to include surface wipe sampling for select coplanar polychlorinated biphenyls (PCBs), congeners of polychlorinated dibenzo(p)dioxins and dibenzofurans (dioxins/furans) and lead. A risk-based screening level method was utilized to determine the necessity of additional sampling and to assess the potential for emergency response crews, remediation crews, and returning Pentagon workers to have adverse health impact from exposure to the PCBs, dioxins/furans, and lead on nonporous surfaces. The screening level method included all exposure pathways: dermal absorption, incidental ingestion, and inhalation. Various U.S. Environmental Protection Agency (USEPA) guidance documents provided the basis for the method. The underlying assumptions were that the PCBs, dioxins/furans, and lead were contained in the dust or soot layer found on nonporous surfaces, that sampling results were representative of the surfaces from which they were taken, and that the analytical methods employed were able to detect 100% of these substances. A few of the limitations associated with this method included the lack of toxicity values for dermal absorption and the lack of accurate, discrete dermal-exposure values. Evaluation results indicated that additional sampling was not necessary and that concentrations of PCBs, dioxins/furans, and lead on nonporous surfaces were below levels expected to cause adverse health impacts to emergency response crews, remediation crews, and returning Pentagon workers.
A review of the effects of uranium and depleted uranium exposure on reproduction and fetal development
Authors: Arfsten Darryl P , Still Kenneth R , Ritchie Glenn D
Published: February 2003

Depleted uranium (DU) is used in armor-penetrating munitions, military vehicle armor, and aircraft, ship and missile counterweighting/ballasting, as well as in a number of other military and commercial applications. Recent combat applications of DU alloy [i.e., Persian Gulf War (PGW) and Kosovo peacekeeping objective] resulted in human acute exposure to DU dust, vapor or aerosol, as well as chronic exposure from tissue embedding of DU shrapnel fragments. DU alloy is 99.8% 238Uranium, and emits approximately 60% of the alpha, beta, and gamma radiation found in natural uranium (4.05×10-7 Ci/g DU alloy). DU is a heavy metal that is 160% more dense than lead and can remain within the body for many years and slowly solubilize. High levels of urinary uranium have been measured in PGW veterans 10 years after exposure to DU fragments and vapors. In rats, there is strong evidence of DU accumulation in tissues including testes, bone, kidneys, and brain. In vitro tests indicate that DU alloy may be both genotoxic and mutagenic, whereas a recent in vivo study suggests that tissue-embedded DU alloy may be carcinogenic in rats. There is limited available data for reproductive and teratological deficits from exposure to uranium per se, typically from oral, respiratory, or dermal exposure routes. Alternatively, there is no data available on the reproductive effects of DU embedded. This paper reviews published studies of reproductive toxicity in humans and animals from uranium or DU exposure, and discusses ongoing animal research to evaluate reproductive effects in male and female rats embedded with DU fragments, and possible consequences in F1 and F2 generations.
Indirect exposure assessment at the United States Environmental Protection Agency
Authors: Lorber Matthew
Published: February 2003

In the early 1980s, exposures and subsequent health impact assessments from contaminants emitted into the air from stationary sources focused on the inhalation pathway. This ‘direct’ pathway of exposure was thought to be the most critical pathway, as it is for many contaminants. However, by the latter 1980s, the focus at the Environmental Protection Agency (EPA) shifted to contaminants that would persist in the environment and could bioaccumulate up the food chain. Consumption of impacted food products, and other ‘indirect’ pathways of exposure, such as soil-related exposures, were shown to result in exposures that exceeded inhalation exposures by two to up to four orders of magnitude. A historical background of indirect exposure assessment at EPA is provided in this paper, followed by an overview of modeling methodologies commonly used in indirect exposure assessments. These methodologies are demonstrated on a contaminant of primary focus for indirect exposure impact, dioxins. Two examples are provided. In the first, an air-to-beef model validation exercise is described. In the second, an indirect exposure assessment on a municipal solid waste incinerator in Ohio conducted by the EPA is summarized. This incinerator emitted very large amounts of dioxin, more than any single source known to EPA. Models were used to predict the movement of dioxins from the stack to a nearby hypothetical farm, where individuals in the farm family were exposed to dioxins from consumption of home-produced beef and milk. The predicted lifetime cancer risk of 2.8×10 -4 based on these food pathways was used by EPA’s Region 5 to initiate regulatory activity on this incinerator.
Application of in vitro biotransformation data and pharmacokinetic modeling to risk assessment
Authors: Kedderis Gregory L , Lipscomb John C
Published: February 2003

The adverse biological effects of toxic substances are dependent upon the exposure concentration and the duration of exposure. Pharmacokinetic models can quantitatively relate the external concentration of a toxicant in the environment to the internal dose of the toxicant in the target tissues of an exposed organism. The exposure concentration of a toxic substance is usually not the same as the concentration of the active form of the toxicant that reaches the target tissues following absorption, distribution, and biotransformation of the parent toxicant. Biotransformation modulates the biological activity of chemicals through bioactivation and detoxication pathways. Many toxicants require biotransformation to exert their adverse biological effects. Considerable species differences in biotransformation and other pharmacokinetic processes can make extrapolation of toxicity data from laboratory animals to humans problematic. Additionally, interindividual differences in biotransformation among human populations with diverse genetics and lifestyles can lead to considerable variability in the bioactivation of toxic chemicals. Compartmental pharmacokinetic models of animals and humans are needed to understand the quantitative relationships between chemical exposure and target tissue dose as well as animal to human differences and interindividual differences in human populations. The data-based compartmental pharmacokinetic models widely used in clinical pharmacology have little utility for human health risk assessment because they cannot extrapolate across dose route or species. Physiologically based pharmacokinetic (PBPK) models allow such extrapolations because they are based on anatomy, physiology, and biochemistry. In PBPK models, the compartments represent organs or groups of organs and the flows between compartments are actual blood flows. The concentration of a toxicant in a target tissue is a function of the solubility of the toxicant in blood and tissues (partition coefficients), blood flow into the tissue, metabolism of the toxicant in the tissue, and blood flow out of the tissue. The appropriate degree of biochemical detail can be added to the PBPK models as needed. Comparison of model simulations with experimental data provides a means of hypothesis testing and model refinement. In vitro biotransformation data from studies with isolated liver cells or subcellular fractions from animals or humans can be extrapolated to the intact organism based upon protein content or cell number. In vitro biotransformation studies with human liver preparations can provide quantitative data on human interindividual differences in chemical bioactivation. These in vitro data must be integrated into physiological models to understand the true impact of interindividual differences in chemical biotransformation on the target organ bioactivation of chemical contaminants in air and drinking water.
Evaluation of immunotoxicity induced by single or concurrent exposure to N, N-diethyl-m-toluamide (DEET), pyridostigmine bromide (PYR), and JP-8 jet fuel
Authors: Peden-Adams Margie M , Eudaly Jackie , Eudaly Erin , Dudley Andrew , Zeigler Jessica , Lee Amanda , Robbs Jessica , Gilkeson Gary , Keil Deborah E
Published: February 2003

Approximately 5000 to 80000 of the US service personnel involved in the Persian Gulf War have complained of a variety of nonspecific symptoms since their return in 1991. These symptoms have been collectively labeled Gulf War Illness and include muscle fatigue, general malaise, myalgia, impaired cognition, ataxia, headaches, fever, joint pain, skin rash, gastrointestinal disturbances, sleep disturbances, and respiratory difficulties. Exposures of military and service personnel were diverse and included the prescribed anti-nerve gas agent pyridostigmine bromide (PYR), N,N-diethyl- m-toluamide (DEET) insect repellent, and environmental exposures to jet fuel. Thus, studies in our laboratory were undertaken to determine if concurrent exposure to these agents, singly or in combination, would contribute to significant alterations in immunological function and disease susceptibility. To assess immune status, eight-week old B6C3F1 female mice were exposed for 14 days to single compounds or tertiary mixtures of 15.5 mg/kg DEET, 2 mg/kg PYR, and 500 mg/kg JP-8 (termed low dose), or 31 mg/kg DEET, 5 mg/kg PYR, and 1000 mg/kg JP-8 (termed high dose). Immunosuppression was assessed 24 h after the last exposure. No remarkable alterations were evident in hematological parameters, spleen and thymus organ weight and total cellularity, natural killer (NK) cell activity, cytotoxic T-cell activity, or mitogen-induced lymphocyte proliferation after exposure to either single or tertiary mixtures at low or high doses. A few changes in CD4/CD8 flow cytometric lymphocyte subpopulations were detected after exposure to the tertiary mixture at the high dose. Delayed type hypersensitivity (DTH) was decreased by 88% after exposure to the high-dose mixture, and suppression of antibody-specific IgM immune responses (plaque-forming cell, PFC) occurred after exposure to all single and tertiary mixtures at both dose levels. In the PFC response, antagonism was apparent in the mixture, while coexposure to these agents resulted in a synergistic effect in the DTH response. Susceptibility to B16F10 tumor or Listeria monocytogenes challenge was not affected after single or tertiary exposures. These data suggest that combined exposure to DEET, PYR, and JP-8 does not profoundly alter many immunological endpoints, but does selectively target functional endpoints such as the PFC and DTH response. This should be considered when assessing human health risks in the military environment.
A spatially and bioenergetically explicit terrestrial ecological exposure model
Authors: Hope Bruce K
Published: February 2003

In typical exposure models, dose is a function of ingestion rate, which is a function of field metabolic rate and food energy availability. It is implicitly assumed that neither food energy nor ingestion rate is limited. This is unlikely to be true in the field. Poor habitat quality (expressed as limited or lacking food energy) or a physiologically limited maximum ingestion rate may collectively limit energy intake. A receptor may thus be as much at risk from lack of energy as from toxicant effects. To explore this possibility, an existing spatially explicit exposure model (SE3M) was enhanced to: 1) express ‘habitat quality’ in terms of gross energy available from a suite of habitat-specific food types, 2) track fulfillment of a receptor’s daily energy needs as it traverses habitat patches with varying gross energy levels, 3) link intake of contaminants to food consumed to meet daily energy needs, and 4) track contaminant doses and resulting tissue residue levels as a receptor moves through habitat patches with differing levels of contamination. A feedback term through which chemical stressors affect a receptor’s ability to intake and process energy was not considered at this time. The now spatially and energetically explicit exposure model, SE4M, provides a platform for exploring spatial and bioenergetic factors that may influence a receptor’s acquisition of energy and contaminant tissue residues as it moves through space and time. An application of this model would be to provide predictions of tissue residue levels that are accessible to calibration or validation with empirical field data.
Skp2 Protein Expression in Soft Tissue Sarcomas
Authors: Oliveira Andre M. , Okuno Scott H. , Nascimento Antonio G. , Lloyd Ricardo V.
Published: February 2003

Background: p45 S phase kinase-associated protein-2 (p45skp2), a member of the F-box family of proteins, is an important component of the Skp1-Cullin-F-box protein (SCF) ubiquitin-ligase complex (SCFskp2). The latter has been implicated in the ubiquitination and degradation of p27kip1 (p27) and G1-S cell cycle progression. The expression and prognostic role of Skp2 in a large series of soft tissue sarcomas has not been previously investigated.

Methods: Clinicopathologic features and immunohistochemical expression of Skp2, p27, and Ki-67 proteins were studied in 182 cases of soft tissue sarcomas (American Joint Committee on Cancer stages II and III). Survival analyses were performed using the Kaplan-Meier method and the Cox regression model.

Results: The male to female ratio was 1.2:1, and the median age at the diagnosis was 53 years. The tumors were predominantly located in the lower extremities (n = 163; 90%) and had a median size of 9 cm. High Skp2 expression (≥ 10% of the cells) was identified in 68 tumors (37%), and was correlated with high grade histology (P = .002) and Ki-67 proliferative index (r = 0.44; P < .0001), but not with p27 expression (r = −0.02; P = .80). By univariate analysis, high Skp2 expression was associated with decreased metastasis-free, disease-free, and overall survival. In a multivariate model, high Skp2 expression was an independent predictor for decreased local recurrence-free, disease-free, and overall survival.

Conclusion: These results indicate that Skp2 expression is associated with cell proliferation and a worse prognosis in soft tissue sarcomas. The lack of an inverse correlation between Skp2 and p27 suggests that additional molecular events associated with either Skp2 expression or p27 proteolysis may be operating in these tumors.
Application of Breast Cancer Risk Prediction Models in Clinical Practice
Authors: Domchek Susan M. , Eisen Andrea , Calzone Kathleen , Stopfer Jill , Blackwood Anne , Weber Barbara L.
Published: February 2003

Breast cancer risk assessment provides an estimation of disease risk that can be used to guide management for women at all levels of risk. In addition, the likelihood that breast cancer risk is due to specific genetic susceptibility (such as BRCA1 or BRCA2 mutations) can be determined. Recent developments have reinforced the clinical importance of breast cancer risk assessment. Tamoxifen chemoprevention as well as prevention studies such as the Study of Tamoxifen and Raloxifene are available to women at increased risk of developing breast cancer. In addition, specific management strategies are now defined for BRCA1 and BRCA2 mutation carriers. Risk may be assessed as the likelihood of developing breast cancer (using risk assessment models) or as the likelihood of detecting a BRCA1 or BRCA2 mutation (using prior probability models). Each of the models has advantages and disadvantages, and all need to be interpreted in context. We review available risk assessment tools and discuss their application. As illustrated by clinical examples, optimal counseling may require the use of several models, as well as clinical judgment, to provide the most accurate and useful information to women and their families.
Nonadherence to Adjuvant Tamoxifen Therapy in Women With Primary Breast Cancer
Authors: Partridge Ann H. , Wang Philip S. , Winer Eric P. , Avorn Jerry
Published: February 2003

Purpose: Although clinical trials have clearly demonstrated the benefits of tamoxifen in women with primary breast cancer, little is known about how this drug is actually used in the general population. We sought to estimate adherence and predictors of nonadherence in women starting tamoxifen as adjuvant breast cancer therapy.

Patients and Methods: Subjects were age 18 years or older initiating tamoxifen for primary breast cancer and enrolled in New Jersey’s Medicaid or Pharmaceutical Assistance to the Aged and Disabled programs during the study period, from 1990 to 1996 (N = 2,378). Main outcome measures were number of days covered by filled prescriptions for tamoxifen in the first year of therapy with the 4 years after tamoxifen initiation for a subset; predictors of good versus poor adherence.

Results: Twenty-three percent of patients missed taking tamoxifen on more than one fifth of days studied, although on average, patients filled prescriptions for tamoxifen for 87% of their first year of treatment. The youngest, oldest, nonwhite, and mastectomy patients had significantly lower rates of adherence; patients who had seen an oncologist before taking tamoxifen had significantly higher rates of adherence. Overall adherence decreased to 50% by year 4 of therapy.

Conclusion: The mean level of adherence to tamoxifen is high compared with other chronic medications. However, nearly one fourth of patients may be at risk for inadequate clinical response because of poor adherence. Because of the efficacy of tamoxifen therapy in preventing recurrence and death in women with early-stage breast cancer, further efforts are necessary to identify and prevent suboptimal adherence.
Phase III Trial of Doxorubicin, Paclitaxel, and the Combination of Doxorubicin and Paclitaxel as Front-Line Chemotherapy for Metastatic Breast Cancer: An Intergroup Trial (E1193)
Authors: Sledge George W. , Neuberg Donna , Bernardo Patricia , Ingle James N. , Martino Silvana , Rowinsky Eric K. , Wood William C.
Published: February 2003

Purpose: Between February 1993 and September 1995, 739 patients with metastatic breast cancer were entered on an Intergroup trial (E1193) comparing doxorubicin (60 mg/m2), paclitaxel (175 mg/m2/24 h), and the combination of doxorubicin and paclitaxel (AT, 50 mg/m2 and 150 mg/m2/24 h, plus granulocyte colony-stimulating factor 5 mg/kg) as first-line therapy. Patients receiving single-agent doxorubicin or paclitaxel were crossed over to the other agent at time of progression.

Patients and Methods: Patients were well balanced for on-study characteristics.

Results: Responses (complete response and partial response) were seen in 36% of doxorubicin, 34% of paclitaxel, and 47% of AT patients (P = .84 for doxorubicin v paclitaxel, P = .007 for v AT, P = .004 for paclitaxel v AT). Median time to treatment failure (TTF) is 5.8, 6.0, and 8.0 months for doxorubicin, paclitaxel, and AT, respectively (P = .68 for doxorubicin v paclitaxel, P = .003 for doxorubicin v AT, P = .009 for paclitaxel v AT). Median survivals are 18.9 months for patients taking doxorubicin, 22.2 months for patients taking paclitaxel, and 22.0 months for patients taking AT (P = not significant). Responses were seen in 20% of patients crossing from doxorubicin → paclitaxel and 22% of patients crossing from paclitaxel → doxorubicin (P = not significant). Changes in global quality-of-life measurements from on-study to week 16 were similar in all three groups.

Conclusion: (1) doxorubicin and paclitaxel, in the doses used here, have equivalent activity; (2) the combination of AT results in superior overall response rates and time to TTF; and (3) despite these results, combination therapy with AT did not improve either survival or quality of life compared to sequential single-agent therapy.
Randomized Comparison of ABVD and MOPP/ABV Hybrid for the Treatment of Advanced Hodgkin’s Disease: Report of an Intergroup Trial
Authors: Duggan David B. , Petroni Gina R. , Johnson Jeffrey L. , Glick John H. , Fisher Richard I. , Connors Joseph M. , Canellos George P. , Peterson Bruce A.
Published: February 2003

Purpose: In a series of trials, doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) and mechlorethamine, vincristine, procarbazine, prednisone, doxorubicin, bleomycin, and vinblastine (MOPP/ABV) have been identified as effective treatments for Hodgkin’s disease. We compared these regimens as initial chemotherapy for Hodgkin’s disease.

Patients and Methods: Adult patients (N = 856) with advanced Hodgkin’s disease were randomly assigned to treatment with ABVD or MOPP/ABV. The major end points were failure-free and overall survival, life-threatening acute toxicities, and serious long-term toxicities, including cardiomyopathy, pulmonary toxicity, myelodysplastic syndromes (MDS), and secondary malignancies.

Results: The rates of complete remission (76% v 80%, P = .16), failure-free survival at 5 years (63% v 66%, P = .42), and overall survival at 5 years (82% v 81%, P = .82) were similar for ABVD and MOPP/ABV, respectively. Clinically significant acute pulmonary and hematologic toxicity were more common with MOPP/ABV (P = .060 and .001, respectively). There was no difference in cardiac toxicity. There were 24 deaths attributed to initial treatment: nine with ABVD and 15 with MOPP/ABV (P = .057). There have been 18 second malignancies associated with ABVD and 28 associated with MOPP/ABV (P = .13). Thirteen patients have developed MDS or acute leukemia: 11 were initially treated with MOPP/ABV, and two were initially treated with ABVD but subsequently received MOPP-containing regimens and radiotherapy before developing leukemia (P = .011).

Conclusion: ABVD and the MOPP/ABV hybrid are effective therapies for Hodgkin’s disease. MOPP/ABV is associated with a greater incidence of acute toxicity, MDS, and leukemia. ABVD should be considered the standard regimen for treatment of advanced Hodgkin’s disease.
Inducible Nitric Oxide Synthase Mediates Bone Loss in Ovariectomized Mice
Authors: Cuzzocrea Salvatore , Mazzon Emanuela , Dugo Laura , Genovese Tiziana , Di Paola Rosanna , Ruggeri Zaira , Vegeto Elisabetta , Caputi Achille P. , Van de Loo Fons A. J. , Puzzolo Domenico , Maggi Adriana
Published: February 2003

Several clinical studies have shown that bone loss may be attributed to osteoclast recruitment induced by mediators of inflammation. In different experimental paradigms we have recently demonstrated that estrogen exhibits antiinflammatory activity by preventing the induction of inducible nitric oxide synthase (iNOS) and other components of the inflammatory reaction. To verify whether this could explain the estrogen-dependent blockade of osteoporosis, we investigated the effect of ovariectomy in mice in which iNOS activity had been blunted by genetic or pharmacological manipulation. The consequences of iNOS blockade were evaluated initially on bone formation and resorption by histomorphometric analysis. The proximal tibiae of mice with iNOS genotypes revealed that 32 d after ovariectomy bone volume and bone formation rate were significantly decreased, and osteoclast surface was increased. Conversely, in iNOS knockout (iNOSKO) and wild-type (WT) mice treated with a specific inhibitor of iNOS, N-iminoethyl-l-lysine, ovariectomy did not result in bone depletion. In WT mice, ovariectomy also affected bone formation, as shown by a decreased mineral apposition rate. Also in this case, iNOS inactivation prevented the effect of ovariectomy. Immunocytochemical analysis showed that after ovariectomy iNOS protein accumulates in chondrocytes, and a significant increase in nitrotyrosine and poly(ADP-ribose) synthetase staining was observed in the femur metaphyses. The increase in nitrotyrosine and poly(ADP-ribose) synthetase formation induced by ovariectomy was significantly reduced in sections from iNOSKO mice. These data indicate that in WT mice the observed induction of iNOS has functional relevance, because it leads to overproduction of nitric oxide and accumulation of highly reactive molecules, triggering a local inflammatory reaction. These inflammatory foci attract cytokines, well known actors in the mechanism of osteoclastogenesis. In iNOSKO mice the measurements of IL-1β, IL-6, and TNFα plasma levels showed that ovariectomy fails to elicit the increase observed in WT animals and suggests that iNOS plays a primary role in the protective effects of estrogens. To further support this hypothesis, we show that estradiol-dependent activation of estrogen receptor-α blocks phorbol 12-acetate 13-myristate-induced transcription of iNOS promoter in transfected cells, thus demonstrating that the promoter of iNOS is under estrogen negative control.

Our findings point to a key role of iNOS in mediating the negative effects of estrogen depletion on bones and provide a novel mechanistic explanation for the effects of menopause in osteoporosis and possibly also in other diseases in which the inflammatory component is elevated.
Characterization of Heme Oxygenase 1 (Heat Shock Protein 32) Induction by Atrial Natriuretic Peptide in Human Endothelial Cells
Authors: Kiemer Alexandra K. , Bildner Nicole , Weber Nina C. , Vollmar Angelika M.
Published: February 2003

Background: Atrial natriuretic peptide (ANP) is a cardiovascular hormone possessing antiinflammatory and cytoprotective potential. The aim of this study was to characterize induction of heme oxygenase (HO)-1 by ANP in human umbilical vein endothelial cells (HUVEC). Methods: HUVEC were treated with ANP, 8-bromo-cyclic GMP (cGMP), or cANF in the presence or absence of various inhibitors. HO-1 was determined by Western blot and RT-PCR, c-jun N-terminal kinase (JNK) and ERK by the use of phospho-specific antibodies. Activator protein (AP)-1 activation was assessed by gelshift assay. Reporter gene assays were performed using native or mutated AP-1 binding sites of the HO-1 promoter. TNF-α-induced cell death was investigated by Hoechst staining, fluorescence-activated cell sorting analysis, caspase-3-measurement, and 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide test. Results: ANP (10−9–10−6 mol/liter) induced the expression of HO-1 protein and mRNA. Induction was mediated via the guanylate-cyclase-coupled receptor because 8-Br-cGMP mimicked the effect of ANP, whereas the clearance receptor agonist cANF did not induce HO-1. Endogenously produced cGMP also induced HO-1 because phosphodiesterase inhibition markedly elevated HO-1. The lack of effect of the cGMP-dependent protein kinase inhibitor 8-(4-chlorophenylthio)guanosine-3′,5′-cyclic monophosphorothioate, Rp-isomer (Rp-8-pCT-cGMPS) suggested no involvement for this cGMP effector pathway in the signal transduction. ANP lead to activation of the transcription factor AP-1, and subsequently of JNK, as well as of ERK. Cotreatment of the cells with U0126 or SP600125, as well as reporter gene assays revealed the involvement of AP-1/JNK activation in HO-1 induction. Abrogation of HO-1 induction by PD-98059 showed also a role for ERK. Treatment of HUVEC with ANP did not protect from TNF-α-induced apoptosis. Conclusion: This work characterizes the induction of HO-1 by ANP in HUVEC, which is shown to be mediated via JNK/AP-1 and ERK pathways. ANP-induced HO-1 does not confer protection against TNF-α-induced apoptosis.
Elevated Levels of Epidermal Growth Factor Receptor/c-erbB2 Heterodimers Mediate an Autocrine Growth Regulatory Pathway in Tamoxifen-Resistant MCF-7 Cells
Authors: Knowlden Janice M. , Hutcheson Iain R. , Jones Helen E. , Madden Tracieann , Gee Julia M. W. , Harper Maureen E. , Barrow Denise , Wakeling Alan E. , Nicholson Robert I.
Published: February 2003

The development of acquired resistance to antihormonal agents in breast cancer is a major therapeutic problem. We have developed a tamoxifen-resistant (TAM-R) MCF-7 breast cancer cell line to investigate the mechanisms behind this condition. Both epidermal growth factor receptor (EGFR) and c-erbB2 mRNA and protein expression were increased in TAM-R compared with wild-type MCF-7 cells, whereas comparable levels of c-erbB3 mRNA and protein were expressed in both cell lines. Under basal conditions, phosphorylated EGFR/c-erbB2, EGFR/c-erbB3 but not c-erbB2/c-erbB3 receptor heterodimers were detected in TAM-R cells in association with increased levels of phosphorylated extracellular-signal regulated kinase 1/2 (ERK1/2). Both cell lines were capable of generating a range of EGFR-specific ligands and increased expression of transforming growth factor α was observed in TAM-R cells. Treatment of TAM-R cells with ZD1839 (Iressa) or trastuzumab (Herceptin) blocked c-erbB receptor heterodimer formation and phosphorylation, reduced ERK1/2 activity, and strongly inhibited cell growth. The MAPK kinase inhibitor PD098059 specifically reduced phosphorylated ERK1/2 levels and inhibited TAM-R growth. All three agents abolished ERK1/2 activity in wild-type cells but caused only small reductions in cell proliferation. These results demonstrate that TAM-R MCF-7 cell growth is mediated by the autocrine release and action of an EGFR-specific ligand inducing preferential EGFR/c-erbB2 dimerization and downstream activation of the ERK pathway.
Growth Hormone Action on Proliferation and Differentiation of Cerebral Cortical Cells from Fetal Rat
Authors: Ajo Rocío , Cacicedo Lucinda , Navarro Constanza , Sánchez-Franco Franco
Published: February 2003

To define the role of GH during central nervous system development, we performed studies in cultured rat cerebral cortical cells from 14- (E14) and 17-d-old embryos (E17). The expression of GH receptor, IGF-I receptor, and IGF-I mRNAs was confirmed. In E17, GH increased total cell number (3.9-fold), [3H]-thymidine incorporation (3.5-fold), proliferating cell nuclear antigen levels (2.5-fold), and bromodeoxyuridine (BrdU)-positive cells (2.5-fold). GH action on nestin/BrdUpositive cells was increased in E14 cells at 3 d in vitro (80-fold) but not at 7 d in vitro. In E14 cells, GH increased (9.5-fold) β-tubulin/BrdU cells. In E17 cells, GH induced neuronal differentiation, as indicated by the absence of β-tubulin/BrdU-positive cells and the 5.9-fold increment of β-tubulin protein, and increased glial fibrillary acidic protein/BrdU-positive cells (2.5-fold) and glial fibrillary acidic protein expression (4.5-fold). GH-induced proliferation and differentiation was blocked by IGF-I antiserum. GH increased IGF-binding protein-3 (IGFBP-3), IGF-I receptor protein and its phosphorylation. This study shows that GH promotes proliferation of neural precursors, neurogenesis, and gliogenesis during brain development. These responses are mediated by locally produced IGF-I. GH-induced IGFBP-3 may also have a role in these responses. Therefore, GH is able to activate the IGF-I/IGFBP-3 system in these cerebral cells and induce a physiological action of IGF-I.