Showing papers by "University of Oklahoma published in 2001"

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

The Relations of Regulation and Emotionality to Children's Externalizing and Internalizing Problem Behavior

Abstract: The purpose of this study was to examine the relation of different types of negative emotion and regulation and control to 55- to 97-month-olds' internalizing and externalizing problem behaviors. Parents and teachers provided information on children's (N = 214) adjustment, dispositional regulation and control, and emotion, and children's regulation was observed during several behavioral tasks. Internalizing was defined in two ways: as social withdrawal (to avoid overlap of items with measures of emotionality) or, more broadly, as anxiety, depression, and psychosomatic complaints. In general, children with externalizing problems, compared with children with internalizing problems and nondisordered children, were more prone to anger, impulsivity, and low regulation. Children with internalizing symptoms were prone to sadness, low attentional regulation, and low impulsivity. Relations between internalizing problems and emotionality were more frequent when the entire internalizing scale was used. Findings suggest that emotion and regulation are associated with adjustment in systematic ways and that there is an important difference between effortful control and less voluntary modes of control.

Catalysis Research of Relevance to Carbon Management: Progress, Challenges, and Opportunities

Abstract: There is increased recognition by the world’s scientific, industrial, and political communities that the concentrations of greenhouse gases in the earth’s atmosphere, particularly CO_2, are increasing. For example, recent studies of Antarctic ice cores to depths of over 3600 m, spanning over 420 000 years, indicate an 80 ppm increase in atmospheric CO_2 in the past 200 years (with most of this increase occurring in the past 50 years) compared to the previous 80 ppm increase that required 10 000 years.2 The 160 nation Framework Convention for Climate Change (FCCC) in Kyoto focused world attention on possible links between CO2 and future climate change and active discussion of these issues continues.3 In the United States, the PCAST report4 “Federal Energy Research and Development for the Challenges of the Twenty First Century” focused attention on the growing worldwide demand for energy and the need to move away from current fossil fuel utilization. According to the U.S. DOE Energy Information Administration,5 carbon emission from the transportation (air, ground, sea), industrial (heavy manufacturing, agriculture, construction, mining, chemicals, petroleum), buildings (internal heating, cooling, lighting), and electrical (power generation) sectors of the World economy amounted to ca. 1823 million metric tons (MMT) in 1990, with an estimated increase to 2466 MMT in 2008-2012 (Table 1).

Acclimatization of soil respiration to warming in a tall grass prairie

Abstract: The latest report by the Intergovernmental Panel on Climate Change (IPCC) predicts a 1.4–5.8 °C average increase in the global surface temperature over the period 1990 to 2100 (ref. 1). These estimates of future warming are greater than earlier projections, which is partly due to incorporation of a positive feedback. This feedback results from further release of greenhouse gases from terrestrial ecosystems in response to climatic warming2,3,4. The feedback mechanism is usually based on the assumption that observed sensitivity of soil respiration to temperature under current climate conditions would hold in a warmer climate5. However, this assumption has not been carefully examined. We have therefore conducted an experiment in a tall grass prairie ecosystem in the US Great Plains to study the response of soil respiration (the sum of root and heterotrophic respiration) to artificial warming of about 2 °C. Our observations indicate that the temperature sensitivity of soil respiration decreases—or acclimatizes—under warming and that the acclimatization is greater at high temperatures. This acclimatization of soil respiration to warming may therefore weaken the positive feedback between the terrestrial carbon cycle and climate.

Elevation gradients of species-density: historical and prospective views

Abstract: Studies of elevation clines in diversity and composition of ecological communities date back to the origins of biogeography. A modern resurgence of interests in these elevational clines is likely to contribute important insights for developing a more general theory of species diversity. In order to gain a more comprehensive understanding of geographical clines in diversity, the research programme for montane biogeography should include statistically rigorous tests of apparent patterns, comparisons of patterns among regions and taxonomic or ecological groups of species, and analyses of clines in environmental variables concurrent with biogeographical surveys. The conceptual framework for this research programme should be based on the assumption that elevational gradients in species diversity result from a combination of ecological and evolutionary processes, rather than the presumed independent effects of one overriding force. Given that montane ecosystems are hot spots of biological diversity, an expanded and integrated programme for biogeographic surveys in montane regions should provide valuable insights for conservation biologists.

Supply chain collaboration and logistical service performance

Abstract: Collaboration with external supply chain entities influences increased internal collaboration, which in turn improves service performance. This relationship may be the key to helping managers understand how best to facilitate behavioral change. The implication is that collaborating with customers and suppliers is a first step toward effective collaboration within the firm.

Complete genome sequence of an M1 strain of Streptococcus pyogenes

Abstract: The 1,852,442-bp sequence of an M1 strain of Streptococcus pyogenes, a Gram-positive pathogen, has been determined and contains 1,752 predicted protein-encoding genes. Approximately one-third of these genes have no identifiable function, with the remainder falling into previously characterized categories of known microbial function. Consistent with the observation that S. pyogenes is responsible for a wider variety of human disease than any other bacterial species, more than 40 putative virulence-associated genes have been identified. Additional genes have been identified that encode proteins likely associated with microbial "molecular mimicry" of host characteristics and involved in rheumatic fever or acute glomerulonephritis. The complete or partial sequence of four different bacteriophage genomes is also present, with each containing genes for one or more previously undiscovered superantigen-like proteins. These prophage-associated genes encode at least six potential virulence factors, emphasizing the importance of bacteriophages in horizontal gene transfer and a possible mechanism for generating new strains with increased pathogenic potential.

From State to Market: A Survey of Empirical Studies on Privatization

Abstract: This study surveys the literature examining the privatization of state-owned enterprises(SOEs). We overview the history of privatization, the theoretical and empirical evidence on the relative performance of state owned and privately owned firms, the types of privatization, if and by how much has privatization improved the performance of former SOEs in both non-transition and transition countries, how investors in privatizations have fared, the impact of privatization on the development of capital markets and corporate governance. We concentrate on the empirical evidence on the effects of privatization on firm performance. In most setting privatization "works" in that the firms become more efficient, more profitable, financially healthier, and reward investors. While this holds in both transition and non-transition economies, there is more variation in transition economies. Especially in transition economies, the identity of the new owners and managers is important in determining post-privatization performance.

The functional role of burrowing bivalves in freshwater ecosystems

Abstract: 1. Freshwater systems are losing biodiversity at a rapid rate, yet we know little about the functional role of most of this biodiversity. The ecosystem roles of freshwater burrowing bivalves have been particularly understudied. Here we summarize what is known about the functional role of burrowing bivalves in the orders Unionoida and Veneroida in lakes and streams globally. 2. Bivalves filter phytoplankton, bacteria and particulate organic matter from the water column. Corbicula and sphaeriids also remove organic matter from the sediment by deposit feeding, as may some unionids. Filtration rate varies with bivalve species and size, temperature, particle size and concentration, and flow regime. 3. Bivalves affect nutrient dynamics in freshwater systems, through excretion as well as biodeposition of faeces and pseudofaeces. Excretion rates are both size and species dependent, are influenced by reproductive stage, and vary greatly with temperature and food availability. 4. Bioturbation of sediments through bivalve movements increases sediment water and oxygen content and releases nutrients from the sediment to the water column. The physical presence of bivalve shells creates habitat for epiphytic and epizoic organisms, and stabilizes sediment and provides refugia for benthic fauna. Biodeposition of faeces and pseudofaeces can alter the composition of benthic communities. 5. There is conflicting evidence concerning the role of resource limitation in structuring bivalve communities. Control by bivalves of primary production is most likely when their biomass is large relative to the water volume and where hydrologic residence time is long. Future studies should consider exactly what bivalves feed upon, whether feeding varies seasonally and with habitat, and whether significant overlap in diet occurs. In particular, we need a clearer picture of the importance of suspension versus deposit feeding and the potential advantages and tradeoffs between these two feeding modes. 6. In North America, native burrowing bivalves (Unionidae) are declining at a catastrophic rate. This significant loss of benthic biomass, coupled with the invasion of an exotic burrowing bivalve (Corbicula), may result in large alterations of ecosystem processes and functions.

Fire effects on nitrogen pools and dynamics in terrestrial ecosystems: a meta-analysis

Abstract: A comprehensive and quantitative evaluation of the effects of fire on eco- system nitrogen (N) is urgently needed for directing future fire research and management. This study used a meta-analysis method to synthesize up to 185 data sets from 87 studies published from 1955 to 1999. Six N response variables related to fire were examined: fuel N amount (FNA) and concentration (FNC), soil N amount (SNA) and concentration (SNC), and soil ammonium (NH4 1 ) and nitrate (NO3 2 ) pools. When all comparisons (fire treatment vs. control) were considered together, fire significantly reduced FNA (58%), increased soil NH4 1 (94%) and NO3 2 (152%), and had no significant influences on FNC, SNA, and SNC. The responses of N to fire varied with different independent variables, which were vegetation type, fire type, fuel type, fuel consumption amount, fuel consumption percentage, time after fire, and soil sampling depth. The response of FNA to fire was significantly influenced by vegetation type, fuel type, and fuel consumption amount and percentage. The reduction in FNA was linearly correlated with fuel consumption percentage (r 2 5 0.978). The response of FNC to fire was only affected by fuel type. None of the seven independent variables had any effect on SNA. The responses of SNC, NH4 1 , and NO3 2 depend on soil sampling depth. The responses of both NH4 1 and NO3 2 to fire were significantly affected by fire type and time after fire but had different temporal patterns. The soil NH4 1 pool increased ap- proximately twofold immediately after fire, then gradually declined to the prefire level after one year. The fire-induced increase in the soil NO 3 2 pool was small (24%) immediately after fire, reached a maximum of approximately threefold of the prefire level within 0.5- 1 year after fire, and then declined. This study has identified the general patterns of the responses of ecosystem N that occur for several years after fire. A key research need relevant to fire management is to understand how the short-term responses of N to fire influence the function and structure of terrestrial ecosystems in the long term.

Facilitating Communication across Lines of Political Difference: The Role of Mass Media

Abstract: We use national survey data to examine the extent to which various sources of political information expose people to dissimilar political views. We hypothesize that the individual’s ability and desire to exercise selective exposure is a key factor in determining whether a given source produces exposure to dissimilar views. Although a lack of diverse perspectives is a common complaint against American news media, we find that individuals are exposed to far more dissimilar political views via news media than through interpersonal political discussants. The media advantage is rooted in the relative difficulty of selectively exposing oneself to those sources of information, as well as the lesser desire to do so, given the impersonal nature of mass media.

Disintegration of the scrophulariaceae.

Abstract: A molecular systematic study of Scrophulariaceae sensu lato using DNA sequences of three plastid genes (rbcL, ndhF, and rps2) revealed at least five distinct monophyletic groups. Thirty-nine genera representing 24 tribes of the Scrophulariaceae s.l. (sensu lato) were analyzed along with representatives of 15 other families of Lamiales. The Scrophulariaceae s.s. (sensu stricto) include part or all of tribes Aptosimeae, Hemimerideae, Leucophylleae, Manuleae, Selagineae, and Verbasceae (5 Scrophularieae) and the conventional families Buddlejaceae and Myoporaceae. Veronicaceae includes all or part of tribes Angelonieae, Antirrhineae, Cheloneae, Digitaleae, and Gratioleae and the conventional families Callitrichaceae, Globulariaceae, Hippuridaceae, and Plantaginaceae. The Orobanchaceae include tribes Buchnereae, Rhinantheae, and the conventional Orobanchaceae. All sampled members of Orobanchaceae are parasitic, except Lindenbergia, which is sister to the rest of the family. Family Calceolariaceae Olmstead is newly erected herein to recognize the phylogenetic distinctiveness of tribe Calceolarieae. The Calceolariaceae are close to the base of the Lamiales. The Stilbaceae are expanded by the inclusion of Halleria. Mimulus does not belong in any of these five groups.

Branching fraction and photon energy spectrum for b→sγ

Abstract: We have measured the branching fraction and photon energy spectrum for the radiative penguin process b-->s gamma. We find Beta(b-->s gamma) = (3.21+/-0.43+/-0.27(+0.18)(-0.10))x10(-4), where the errors are statistical, systematic, and from theory corrections. We obtain first and second moments of the photon energy spectrum above 2.0 GeV, = 2.346+/-0.032+/-0.011 GeV, and - (2) = 0.0226+/-0.0066+/-0.0020 GeV(2), where the errors are statistical and systematic. From the first moment, we obtain (in the modified minimal subtraction renormalization scheme, to order 1/M(3)(B) and beta(0)alpha(2)(s)) the heavy quark effective theory parameter Lambda = 0.35+/-0.08+/-0.10 GeV.

Examining the shareholder wealth effects of announcements of newly created CIO positions

Abstract: While information technology (IT) has been transforming the business landscape for a long time now, it is only recently that empirical evidence demonstrating the positive impact of IT on firm performance has begun to accumulate The strategic importance of a firm's IT capabilities is prompting an increasing number of companies to appoint chief information officers (CIOs) to effectively manage these assets Such moves are reflective of changes in top management thinking and policy regarding the role of IT and firms' approaches to IT governance This paper uses the event study methodology to examine market reactions to announcements of new CIO positions Findings strongly support the notion that, for firms competing in industries undergoing IT-driven transformation, announcements of newly created CIO positions do indeed provoke positive reactions from the marketplace

The Social Construction of an Imperative: Why Welfare Reform Happened in Denmark and the Netherlands but Not in Germany

Abstract: This article seeks to explain why Denmark and the Netherlands made dramatic progress reforming their welfare systems in the 1990s and why Germany had a relatively slow start. Some possible explanations found to be incomplete are institutional differences in welfare programs, the uniqueness of circumstances (for example, German unification), and the balance of political power in governing institutions. An important part of the puzzle is an increasing perception of the need to reform that was more widespread in Denmark and the Netherlands. The social construction of an imperative to reform in these countries generated a political consensus that was elusive in Germany but that may be developing under Gerhard Schroder's government.

Additional Evidence on Audit Report Lag

Abstract: The process for providing accounting information to the public has not changed much in the last century even though the extent of disclosure has increased signifi‐cantly. Sundem et al. (1996) suggest that the primary benefit of audited financial statements may not be decision usefulness but the discipline imposed by timely confirmation of previously available information. In general, the value of information from the audited financial statement will decline as the audit report lag (the time period between a company's fiscal year end and the date of the audit report) increases since competitively oriented users may obtain substitute sources of information. Furthermore, the literature on earnings quality and earnings management suggests that unexpected reporting delays may be associated with lower quality information. The purpose of this paper is to extend our understanding about the determinants of audit report lag using a proprietary database containing 226 audit engagements from an international public a...

The Complete Sequence of the Zebrafish (Danio rerio) Mitochondrial Genome and Evolutionary Patterns in Vertebrate Mitochondrial DNA

Abstract: We describe the complete sequence of the 16,596-nucleotide mitochondrial genome of the zebrafish (Danio rerio); contained are 13 protein genes, 22 tRNAs, 2 rRNAs, and a noncoding control region. Codon usage in protein genes is generally biased toward the available tRNA species but also reflects strand-specific nucleotide frequencies. For 19 of the 20 amino acids, the most frequently used codon ends in either A or C, with A preferred over C for fourfold degenerate codons (the lone exception was AUG: methionine). We show that rates of sequence evolution vary nearly as much within vertebrate classes as between them, yet nucleotide and amino acid composition show directional evolutionary trends, including marked differences between mammals and all other taxa. Birds showed similar compositional characteristics to the other nonmammalian taxa, indicating that the evolutionary trend in mammals is not solely due to metabolic rate and thermoregulatory factors. Complete mitochondrial genomes provide a large character base for phylogenetic analysis and may provide for robust estimates of phylogeny. Phylogenetic analysis of zebrafish and 35 other taxa based on all protein-coding genes produced trees largely, but not completely, consistent with conventional views of vertebrate evolution. It appears that even with such a large number of nucleotide characters (11,592), limited taxon sampling can lead to problems associated with extensive evolution on long phyletic branches.

Towards a more general species-area relationship : diversity on all islands, great and small

Abstract: Aim To demonstrate a new and more general model of the species–area relationship that builds on traditional models, but includes the provision that richness may vary independently of island area on relatively small islands (the small island effect). Location We analysed species–area patterns for a broad diversity of insular biotas from aquatic and terrestrial archipelagoes. Methods We used breakpoint or piecewise regression methods by adding an additional term (the breakpoint transformation) to traditional species–area models. The resultant, more general, species–area model has three readily interpretable, biologically relevant parameters: (1) the upper limit of the small island effect (SIE), (2) an estimate of richness for relatively small islands and (3) the slope of the species–area relationship (in semi-log or log–log space) for relatively large islands. Results The SIE, albeit of varying magnitude depending on the biotas in question, appeared to be a relatively common feature of the data sets we studied. The upper limit of the SIE tended to be highest for species groups with relatively high resource requirements and low dispersal abilities, and for biotas of more isolated archipelagoes. Main conclusions The breakpoint species–area model can be used to test for the significance, and to explore patterns of variation in small island effects, and to estimate slopes of the species–area (semi-log or log–log) relationship after adjusting for SIE. Moreover, the breakpoint species–area model can be expanded to investigate three fundamentally different realms of the species–area relationship: (1) small islands where species richness varies independent of area, but with idiosyncratic differences among islands and with catastrophic events such as hurricanes, (2) islands beyond the upper limit of SIE where richness varies in a more deterministic and predictable manner with island area and associated, ecological factors and (3) islands large enough to provide the internal geographical isolation (large rivers, mountains and other barriers within islands) necessary for in situ speciation.

Intercomparison of global precipitation products : The third Precipitation Intercomparison Project (PIP-3)

Abstract: A set of global, monthly rainfall products has been intercompared to understand the quality and utility of the estimates. The products include 25 observational (satellite-based), four model and two climatological products. The results of the intercomparison indicate a very large range (factor of two or three) of values when all products are considered. The range of values is reduced considerably when the set of observational products is limited to those considered quasi-standard. The model products do significantly poorer in the tropics, but are competitive with satellite-based fields in mid-latitudes over land. Over ocean, products are compared to frequency of precipitation from ship observations. The evaluation of the observational products point to merged data products (including rain gauge information) as providing the overall best results.

Paroxetine in the treatment of chronic posttraumatic stress disorder: results of a placebo-controlled, flexible-dosage trial.

Abstract: BACKGROUND The objective of this double-blind, placebo-controlled study was to investigate the efficacy and safety of paroxetine in outpatients with posttraumatic stress disorder (PTSD) METHOD Male and female outpatients 18 years and older who met DSM-IV criteria for PTSD and had baseline scores of 50 or greater on the Clinician Administered PTSD Scale (CAPS-2) were randomly assigned to treatment with paroxetine (20-50 mg/day) or placebo for 12 weeks The primary efficacy variables were the change from baseline to the 12-week endpoint in the CAPS-2 total score and the proportion of responders on the Clinical Global Impressions-Global Improvement scale (CGI-1) Additional key outcome measures were the change from baseline in the reexperiencing, avoidance/ numbing, and hyperarousal scores of the CAPS-2 and in the total scores of the Treatment Outcome PTSD Scale and the patient-rated Davidson Trauma Scale and Sheehan Disability Scale (SDS) Depressive symptoms were assessed with the Montgomery-Asberg Depression Rating Scale The proportion of patients achieving response and remission was also determined RESULTS 307 patients constituted the intent-to-treat population At week 12, compared with the placebo group (N = 156), the paroxetine group (N = 151) showed significantly greater reduction of PTSD symptoms on both of the primary and all of the secondary outcome measures Significantly greater improvement on the CAPS-2 total score was observed for paroxetine compared with placebo from week 4 (p < 05), and significantly greater proportions of paroxetine-treated patients achieved response (p < 001) and remission (p = 008) by week 12 The improvement in PTSD symptoms was similar in male and female patients Functional improvement at the study endpoint was significantly greater (p < 05) in the paroxetine group in all 3 domains of the SDS (work, social life, family life) Treatment with paroxetine was well tolerated, with the frequency and type of adverse events recorded for the paroxetine group corresponding to the known safety profile of this medication CONCLUSION Paroxetine in doses of 20 to 50 mg once daily is effective as a treatment for chronic PTSD Improvement is obtained for all 3 symptom clusters (reexperiencing, avoidance/numbing, hyperarousal) and is associated with significant reduction in disability after 12 weeks of treatment

Anatomical Distribution and Cellular Basis for High Levels of Aromatase Activity in the Brain of Teleost Fish: Aromatase Enzyme and mRNA Expression Identify Glia as Source

Abstract: Although teleost fish have higher levels of brain aromatase activity than any other vertebrate group, its function remains speculative, and no study has identified its cellular basis. A previous study determined aromatase activity in a vocal fish, the plainfin midshipman ( Porichthys notatus ), and found highest levels in the telencephalon and lower levels in the sonic hindbrain, which was dimorphic between and within (males) sexes. We have now localized aromatase-containing cells in the midshipman brain both by immunocytochemistry using teleost-specific aromatase antibodies and by in situ hybridization using midshipman-specific aromatase probes. Aromatase-immuno-reactivity and mRNA hybridization signal are consistent with relative levels of aromatase activity in different brain regions: concentrated in the dimorphic sonic motor nucleus, in a band just beneath the periaqueductal gray in the midbrain, in ventricular regions in the hypothalamus, and highest levels in the telencephalon especially in preoptic and ventricular areas. Surprisingly, double-label immunofluorescence does not show aromatase-immunoreactive colocalization in neurons, but instead in radial glia throughout the brain. This is the first study to identify aromatase expression mostly, if not entirely, in glial cells under normal rather than brain injury-dependent conditions. The abundance of aromatase in teleosts may represent an adaptation linked to continual neurogenesis that is known to occur throughout an individual's lifetime among fishes. The localization of aromatase within the intersexually and intrasexually dimorphic vocal-motor circuit further implies a function in the expression of alternative male reproductive phenotypes and, more generally, the development of natural, individual variation of specific brain nuclei.

Distributed Hydrologic Modeling Using GIS

Abstract: Considering the spatial character of parameters and precipitation controlling hydrologic processes, it is not surprising that Geographic Information Systems (GIS) have become an integral part of hydrologic studies. The primary motivation for this book is to bring together the key ingredients necessary to use GIS to model hydrologic processes, i.e., the spatial and temporal distribution of the inputs and parameters controlling surface runoff. GIS maps describing topography, land use and cover, soils, rainfall, and meteorological variables may become model parameters or inputs in the simulation of hydrologic processes.

Theory of magnetic anisotropy in III 1 − x Mn x V ferromagnets

Abstract: We present a theory of magnetic anisotropy in ${\mathrm{III}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{V}$-diluted magnetic semiconductors with carrier-induced ferromagnetism. The theory is based on four- and six-band envelope function models for the valence-band holes and a mean-field treatment of their exchange interactions with ${\mathrm{Mn}}^{++}$ ions. We find that easy-axis reorientations can occur as a function of temperature, carrier density p, and strain. The magnetic anisotropy in strain-free samples is predicted to have a ${p}^{5/3}$ hole-density dependence at small p, a ${p}^{\ensuremath{-}1}$ dependence at large p, and remarkably large values at intermediate densities. An explicit expression, valid at small p, is given for the uniaxial contribution to the magnetic anisotropy due to unrelaxed epitaxial growth lattice-matching strains. Results of our numerical simulations are in agreement with magnetic anisotropy measurements on samples with both compressive and tensile strains. We predict that decreasing the hole density in current samples will lower the ferromagnetic transition temperature, but will increase the magnetic anisotropy energy and the coercivity.

Ductal Lavage for Detection of Cellular Atypia in Women at High Risk for Breast Cancer

Abstract: Background: Breast cancer originates in breast epithelium and is associated with progressive molecular and morphologic changes. Women with atypical breast ductal epithelial cells have an increased relative risk of breast cancer. In this study, ductal lavage, a new procedure for collecting ductal cells with a microcatheter, was compared with nipple aspiration with regard to safety, tolerability, and the ability to detect abnormal breast epithelial cells. Methods: Women at high risk for breast cancer who had nonsuspicious mammograms and clinical breast examinations underwent nipple aspiration followed by lavage of fluid-yielding ducts. All statistical tests were two-sided. Results: The 507 women enrolled included 291 (57%) with a history of breast cancer and 199 (39%) with a 5-year Gail risk for breast cancer of 1.7% or more. Nipple aspirate fluid (NAF) samples were evaluated cytologically for 417 women, and ductal lavage samples were evaluated for 383 women. Adequate samples for diagnosis were collected from 111 (27%) and 299 (78%) women, respectively. A median of 13500 epithelial cells per duct (range, 43-492 000 cells) was collected by ductal lavage compared with a median of 120 epithelial cells per breast (range, 10-74300) collected by nipple aspiration. For ductal lavage, 92 (24%) subjects had abnormal cells that were mildly (17%) or markedly (6%) atypical or malignant (<1%). For NAF, corresponding percentages were 6%, 3%, and fewer than 1 %. Ductal lavage detected abnormal intraductal breast cells 3.2 times more often than nipple aspiration (79 versus 25 breasts; McNemar's test, P<.001). No serious procedure-related adverse events were reported. Conclusions: Large numbers of ductal cells can be collected by ductal lavage to detect atypical cellular changes within the breast. Ductal lavage is a safe and well-tolerated procedure and is a more sensitive method of detecting cellular atypia than nipple aspiration.