Ohio University Lancaster

Ever increasing use of engineered carbon nanoparticles in nanopharmacology for selective imaging, sensor or drug delivery systems has increased the potential for blood platelet-nanoparticle interactions. We studied the effects of engineered and combustion-derived carbon nanoparticles on human platelet aggregation in vitro and rat vascular thrombosis in vivo. Multiplewall (MWNT), singlewall (SWNT) nanotubes, C60 fullerenes (C60CS) and mixed carbon nanoparticles (MCN) (0.2-300 microg ml(-1)) were investigated. Nanoparticles were compared with standard urban particulate matter (SRM1648, average size 1.4 microm). Platelet function was studied using lumi aggregometry, phase-contrast, immunofluorescence and transmission electron microscopy, flow cytometry, zymography and pharmacological inhibitors of platelet aggregation. Vascular thrombosis was induced by ferric chloride and the rate of thrombosis was measured, in the presence of carbon particles, with an ultrasonic flow probe. Carbon particles, except C60CS, stimulated platelet aggregation (MCN>or=SWNT>MWNT>SRM1648) and accelerated the rate of vascular thrombosis in rat carotid arteries with a similar rank order of efficacy. All particles resulted in upregulation of GPIIb/IIIa in platelets. In contrast, particles differentially affected the release of platelet granules, as well as the activity of thromboxane-, ADP, matrix metalloproteinase- and protein kinase C-dependent pathways of aggregation. Furthermore, particle-induced aggregation was inhibited by prostacyclin and S-nitroso-glutathione, but not by aspirin. Thus, some carbon nanoparticles and microparticles have the ability to activate platelets and enhance vascular thrombosis. These observations are of importance for the pharmacological use of carbon nanoparticles and pathology of urban particulate matter.

A mechanistic model of uniform carbon dioxide (CO2) corrosion is presented that covers the following: electrochemical reactions at the steel surface, diffusion of species between the metal surface and the bulk including diffusion through porous surface films, migration due to establishment of potential gradients, and homogenous chemical reactions including precipitation of surface films. The model can predict the corrosion rate as well as the concentration and flux profiles for all species involved. Comparisons with laboratory experiments have revealed the strengths of the model such as its ability to assist in understanding complex processes taking place during corrosion in the presence of surface films.

OBJECTIVE: Scleroderma (systemic sclerosis; SSc) is an autoimmune disease characterized by vasculopathy and widespread organ fibrosis. Altered fibroblast function, both in vivo and in vitro, is well documented and illustrated by augmented synthesis and deposition of extracellular matrix proteins. We undertook this study to investigate the possibility that epigenetic mechanisms mediate the emergence and persistence of the altered SSc fibroblast phenotype. METHODS: The effects of DNA methyltransferase and histone deacetylase inhibitors on collagen expression and the level of epigenetic mediators in fibroblasts were examined. The effects of transient transfection of SSc fibroblasts with FLI1 gene and normal cells with FLI1 antisense construct on collagen expression were determined. The methylation status of the FLI1 promoter was tested in cultured cells and in SSc and normal skin biopsy specimens. RESULTS: Increased levels of epigenetic mediators in SSc fibroblasts were noted. The addition of epigenetic inhibitors to cell cultures normalized collagen expression in SSc fibroblasts. The augmented collagen synthesis by SSc fibroblasts was linked to epigenetic repression of the collagen suppressor gene FLI1. Heavy methylation of the CpG islands in the FLI1 promoter region was demonstrated in SSc fibroblasts and skin biopsy specimens. CONCLUSION: The results of this study indicate that epigenetic mechanisms may mediate the fibrotic manifestations of SSc. The signal transduction leading to the SSc fibrotic phenotype appears to converge on DNA methylation and histone deacetylation at the FLI1 gene.

The ratios of inclusive electron scattering cross sections of $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, and $^{56}\mathrm{Fe}$ to $^{3}\mathrm{He}$ have been measured at $1<{x}_{B}<3$. At ${Q}^{2}>1.4\text{ }\text{ }{\mathrm{GeV}}^{2}$, the ratios exhibit two separate plateaus, at $1.5<{x}_{B}<2$ and at ${x}_{B}>2.25$. This pattern is predicted by models that include 2- and 3-nucleon short-range correlations (SRC). Relative to $A=3$, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.1, and 4.4 times larger for $A=4$, 12, and 56. This is the first measurement of 3-nucleon SRC probabilities in nuclei.

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A theoretical carbon dioxide (CO2) corrosion model was used to conduct numerical experiments, which allowed total insight into the underlying physicochemical processes. The focus was on factors influencing protective iron carbonate film formation and the effect that these films have on the CO2 corrosion process. It was confirmed that high bulk pH, high temperature, high partial pressure of CO2, high Fe2+ concentration, and low velocity all lead to favorable conditions for protective iron carbonate film formation. The model can be used to identify threshold values of these parameters. Corrosion rate was not strongly correlated with protective film thickness. The so-called surface film “coverage” effect appeared to be more important. Corrosion rates decreased rapidly as the film density increased. It was shown that in the presence of dense films diffusion of dissolved CO2 through the film is the main mechanism of providing the reactants to the corrosion reaction at the metal surface. It was demonstrated that “detached” films have poor protective properties even when they are very dense. Serious errors in prediction/reasoning can be made by operating with bulk instead of surface water chemistry conditions. The former is made possible by using advanced models such as the one used in the present study.

High-statistics cross sections and recoil polarizations for the reactions $\ensuremath{\gamma}+p\ensuremath{\rightarrow}{K}^{+}+\ensuremath{\Lambda}$ and $\ensuremath{\gamma}+p\ensuremath{\rightarrow}{K}^{+}+{\ensuremath{\Sigma}}^{0}$ have been measured at CLAS for center-of-mass energies between 1.6 and $2.3\phantom{\rule{0.3em}{0ex}}\text{GeV}$. In the ${K}^{+}\ensuremath{\Lambda}$ channel we confirm a resonance-like structure near $W=1.9\phantom{\rule{0.3em}{0ex}}\text{GeV}$ at backward kaon angles. Our data show more complex $s$- and $u$- channel behavior than previously seen, since structure is also present at forward angles, but not at central angles. The position and width change with angle, indicating that more than one resonance is playing a role. Large positive $\ensuremath{\Lambda}$ polarization at backward angles, which is also energy dependent, is consistent with sizable $s$- or $u$-channel contributions. Presently available model calculations cannot explain these aspects of the data.

Photon attenuation in cardiac single photon emission computed tomography (SPECT) is a major factor contributing to the quantitative inaccuracy and the decrease in specificity of lesion detection. A measured map of the attenuation distribution was used in combination with iterative reconstruction algorithms to accurately compensate for the variable attenuation in the chest. The transmission and emission data were acquired simultaneously using a multidetector, fan-beam collimated SPECT system with a transmission line source (Tc-99m) precisely aligned at the focal line opposite one of the detectors and of a different energy than the emission source (Tl-201). The contamination of transmission data by the high-energy photopeaks of Tl-201 was removed based on measurements from emission-only acquisition detectors. An algorithm was derived to eliminate scatter of Tc-99m transmission photons into the lower-energy Tl-201 window of all three detectors. Results are given for both phantom and patient studies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

We have shown that the Na/K-ATPase and Src form a signaling receptor complex. Here we determined how alterations in the amount and properties of the Na/K-ATPase affect basal Src activity and ouabain-induced signal transduction. Several alpha1 subunit knockdown cell lines were generated by transfecting LLC-PK1 cells with a vector expressing alpha1-specific small interference RNA. Although the alpha1 knockdown resulted in significant decreases in Na/K-ATPase activity, it increased the basal Src activity and tyrosine phosphorylation of focal adhesion kinase, a Src effector. Concomitantly it also abolished ouabain-induced activation of Src and ERK1/2. When the knockdown cells were rescued by a rat alpha1, both Na/K-ATPase activity and the basal Src activity were restored. In addition, ouabain was able to stimulate Src and ERK1/2 in the rescued cells at a much higher concentration, consistent with the established differences in ouabain sensitivity between pig and rat alpha1. Finally both fluorescence resonance energy transfer analysis and co-immunoprecipitation assay indicated that the pumping-null rat alpha1 (D371E) mutant could also bind Src. Expression of this mutant restored the basal Src activity and focal adhesion kinase tyrosine phosphorylation. Taken together, the new findings suggest that LLC-PK1 cells contain a pool of Src-interacting Na/K-ATPase that not only regulates Src activity but also serves as a receptor for ouabain to activate protein kinases.

Study Design Prospective cohort study. Background While meeting objective criterion cutoffs is recommended prior to return to sports following anterior cruciate ligament (ACL) reconstruction, the number of young athletes who meet recommended cutoffs and the impact of cutoffs on longitudinal sports participation are unknown. Objectives To test the hypothesis that a higher proportion of young athletes who meet recommended cutoffs will maintain the same level of sports participation over the year following return-to-sport clearance compared to those who do not meet recommended cutoffs. Methods At the time of return-to-sport clearance, the International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC), quadriceps and hamstring strength limb symmetry index (LSI), and single-leg hop test LSI were assessed. Proportions of participants who met individual (IKDC score of 90 or greater; strength and hop test LSIs of 90% or greater) and combined cutoffs were calculated. Proportions of participants who continued at the same level of sports participation over the year following return-to-sport clearance (assessed using the Tegner activity scale) were compared between those who met and did not meet cutoffs. Results Participants included 115 young athletes (88 female). The proportions meeting individual cutoffs ranged from 43.5% to 78.3%. The proportions meeting cutoffs for all hop tests, all strength tests, and all combined measures were 53.0%, 27.8%, and 13.9%, respectively. A higher proportion of participants who met cutoffs for both strength tests maintained the same level of sports participation over the year following return-to-sport clearance than those who did not (81.3% versus 60.2%, P = .02). Conclusion The proportions of young athletes after ACL reconstruction recently cleared for return to sports who met the combined criterion cutoffs were low. Those who met the criterion cutoffs for both strength tests maintained the same level of sports participation at higher proportions than those who did not. Level of Evidence Prognosis, level 2b. J Orthop Sports Phys Ther 2017;47(11):825-833. Epub 7 Oct 2017. doi:10.2519/jospt.2017.7227.

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent $\mathrm{D}(\stackrel{\ensuremath{\rightarrow}}{e},{e}^{\ensuremath{'}}\ensuremath{\gamma})X$ cross section measured at ${Q}^{2}=1.9\text{ }\text{ }{\mathrm{GeV}}^{2}$ and ${x}_{B}=0.36$. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to ${E}_{q}$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

The moderating effects of need for achievement and need for independence on relationships between role ambiguity, role conflict, and job satisfaction were investigated. Subjects were 90 military and civil service personnel. Results indicated that need for achievement moderates relationships between intersender role conflict and satisfaction and between task ambiguity and satisfaction, while need for independence moderates the relationship between intersender conflict and satisfaction. In recent years a number of studies have explored relationships between role conflict and role ambiguity and worker attitudes and behavior (Greene & Organ, 1973; Johnson & Graen, 1973; Kahn, Wolfe, Quinn, Snoek, & Rosen thai, 1964; Lyons, 1971; Rizzo, House, & Lirtzman, 1970; Tosi, 1971). Only two of these studies, however, have examined the influence of individual differences on worker responses to role conflict and role ambiguity (Kahn et ah, 1964; Lyons, 1971). This study sought to obtain additional evidence on the influence of individual differences by examining the moderating effects of need for achievement and need for independence on relationships between role conflict, role ambiguity, and satisfaction.

We report results for the virtual photon asymmetry A1 on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton (NH315) and deuteron (ND315) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present Letter, we concentrate on our results for A1(x,Q2) and the related ratio g1/F1(x,Q2) in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer Q2 from 0.05 to 5.0(GeV/c)2 and in final-state invariant mass W up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong Q2-dependence of A1(x,Q2) for W below 2 GeV. At higher W, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but A1(x,Q2) is not strictly Q2-independent. We add significantly to the world data set at high x, up to x=0.6. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative d-quark polarization up to our highest x. This data set should improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.

The last decade has witnessed an explosion of ‘immigrant protests’, political mobilizations by irregular migrants and pro-migrant activists. This special issue on ‘immigrant protest’ has emerged in response to this rise in the visibility of immigrant protests, and its central aim is to contribute to the growing body of scholarship on migrant resistance movements and to consider the implications of these struggles for critical understandings of citizenship. This introduction maps out some of the central issues and themes emerging from the contributions to this issue, exploring the tensions between integrationist and autonomous approaches and theories of migrant activism and resistance and between migrant and activist strategies of invisibility and visibility. By bringing immigrant protests to the heart of debates about citizenship, we hope to further extend discussions about the limits and the possibilities of citizenship as the material and conceptual horizon of critical social analysis and political participation and practice today.

Research Article| September 01, 1980 Late Miocene marine carbon-isotopic shift and synchroneity of some phytoplanktonic biostratigraphic events B. U. Haq; B. U. Haq 1Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar T. R. Worsley; T. R. Worsley 2University of Ohio, Athens, Ohio 45701 Search for other works by this author on: GSW Google Scholar L H. Burckle; L H. Burckle 3Lamont-Doherty Geological Observatory, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar R. G. Douglas; R. G. Douglas 4University of Southern California, Los Angeles, California 90007 Search for other works by this author on: GSW Google Scholar L. D. Keigwin, Jr.; L. D. Keigwin, Jr. 5University of Rhode Island, Kingston, Rhode Island 02881 Search for other works by this author on: GSW Google Scholar N. D. Opdyke; N. D. Opdyke 6Lamont-Doherty Geological Observatory, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar S. M. Savin; S. M. Savin 7Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar M. A. Sommer, II; M. A. Sommer, II 8Florida State University, Tallahassee, Florida 32306 Search for other works by this author on: GSW Google Scholar E. Vincent; E. Vincent 9Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar F. Woodruff F. Woodruff 10University of Southern California, Los Angeles, California 90007 Search for other works by this author on: GSW Google Scholar Geology (1980) 8 (9): 427–431. https://doi.org/10.1130/0091-7613(1980)8<427:LMMCSA>2.0.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation B. U. Haq, T. R. Worsley, L H. Burckle, R. G. Douglas, L. D. Keigwin, N. D. Opdyke, S. M. Savin, M. A. Sommer, E. Vincent, F. Woodruff; Late Miocene marine carbon-isotopic shift and synchroneity of some phytoplanktonic biostratigraphic events. Geology 1980;; 8 (9): 427–431. doi: https://doi.org/10.1130/0091-7613(1980)8<427:LMMCSA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A search for stable-isotopic signals and biostratigraphic events in Deep Sea Drilling Project (DSDP) cores to improve chronologic resolution with an aim to reconstruct the paleoenvironment of the preglacial and postglacial Miocene oceans has led to the recognition of an apparently global decrease in the benthic foraminiferal δ 13C in the latest Miocene. This carbon-isotopic shift is consistently bracketed by the first evolutionary appearances of several taxa of phytoplankton the ages of which have been accurately estimated from paleomagnetically dated piston cores. The first appearance of nannofossils Amaurolithus primus and A. delicatus at 6.25 m.y. B.P. and the diatoms Thalassiosira praeconvexa and Nitzschia miocenica elongata at 6.10 and 6.00 m.y. B.P., respectively, and the carbon-isotopic shift itself (dated between 6.10 and 5.90 m.y. B.P.) provide convenient synchronous events to aid in the reconstruction of the late Miocene world ocean. Magnetostratigraphically estimated ages of other useful late Miocene nannofossil events include first appearances of Discoaster quinqueramus at 8.00 m.y. B.P., D. surculus at 6.40 m.y. B.P., Amaurolithus tricorniculatus s.s. at 5.70 m.y. B.P., A. amplificus at 5.65 m.y. B.P., and Ceratolithus acutus at 5.20 m.y. B.P., and the last appearances of D. quinqueramus at 5.45 m.y. B.P. and A. amplificus at 5.30 m.y. B.P. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Viroids are the smallest plant pathogens. These RNAs do not encode proteins and are not encapsidated, and yet they can replicate autonomously, move systemically, and cause diseases in infected plants. Notably, strains of a viroid with subtle differences in nucleotide sequences can cause dramatically different symptoms in infected plants. These features make viroids unique probes to investigate the role of a pathogenic RNA genome in triggering host responses. We conducted a comprehensive analysis of the differential gene expression patterns of tomato plants at various stages of infection by a mild and severe strain of Potato spindle tuber viroid (PSTVd). We also compared tomato gene expression altered by the PSTVd strains with that altered by Tobacco mosaic virus (TMV). Our analyses revealed that the two PSTVd strains altered expression of both common and unique tomato genes. These genes encode products involved in defense/stress response, cell wall structure, chloroplast function, protein metabolism, and other diverse functions. Five genes have unknown functions. Four genes are novel. The expression of some but not all of these genes was also altered by TMV infection. Our results indicate that viroids, although structurally simple, can trigger complex host responses. Further characterization of viroid-altered gene expression in a host plant should help understand viroid pathogenicity and, potentially, the mechanisms of RNA-mediated regulation of plant gene expression.

The Mahajanga Basin Project, initiated in 1993 and centered in Upper Cretaceous strata of northwestern Madagascar, has resulted in the discovery of some of the most complete, well-preserved, and significant specimens of Late Cretaceous vertebrate animals from the Southern Hemisphere and indeed the world. Among the most important finds are various specimens of crocodyliforms, non-avian dinosaurs, and mammals; these finds have the potential to provide key insights into the biogeographic and paleogeographic history of Gondwana. Madagascar has been physically isolated from Africa for over 160 million years and from all other major landmasses for more than 85 million years. The closest known relatives of many of the Late Cretaceous Malagasy taxa are penecontemporaneous forms from South America (primarily Argentina) and India, thus documenting a previously unrecognized high level of cosmopolitanism among Gondwanan vertebrates near the end of the Cretaceous. The family-level taxa that are shared among Madagascar, South America, and the Indian subcontinent are not known from penecontemporaneous horizons in mainland Africa, but it cannot yet be confidently determined if this is due to differential extinction, poor sampling, true absence (i.e., the taxa were never present on Africa), or some combination thereof. Nonetheless, currently available geologic and paleontologic data are most consistent with the Africa-first model, suggesting that Africa was the first of the major Gondwanan landmasses to be fully isolated prior to the Albian/Cenomanian boundary, and that its terrestrial vertebrate faunas became progressively more provincial during the Cretaceous, while those on other Gondwanan landmasses remained relatively cosmopolitan until the later stages of the Late Cretaceous.

Toll-like receptors (TLRs) initiate an innate immune response. TLR3 on dendritic cells recognize double-stranded (ds) RNA and then signal increases in cytokines and recognition molecules important for immune cell interactions. In this report, we demonstrate TLR3 mRNA and protein are expressed on Fisher rat thyroid cell line-5 (FRTL-5) thyroid cells and are functional because incubating cells with polyinosine-polycytidylic acid causes 1) transcriptional activation of both the nuclear factor kappaB (NF-kappaB)/Elk1 and interferon (IFN) regulatory factor-3/IFN-beta signal paths, 2) posttranscriptional activation of NF-kappaB and ERK1/2, and 3) increased IFN-beta mRNA. TLR3 can be overexpressed, along with dsRNA-dependent protein kinase, major histocompatibility complex-I or II, and IFN regulatory factor-1, by transfecting dsRNA into the cells, infection with Influenza A virus, or incubation with IFN-beta, but not by incubation with dsRNA or IFNgamma, or by dsDNA transfection. A methimazole (MMI) derivative, phenylmethimazole, to a significantly greater degree than MMI, prevents overexpression by inhibiting increased transcriptional activation of IRF-3 and of IFN-stimulated response elements, phosphorylation of signal transducers and activation of transcription (STAT-1), but not NF-kappaB activation. TLR3 can be functionally overexpressed in cultured human thyrocytes by dsRNA transfection or IFN-beta treatment. Immunohistochemical studies show that TLR3 protein is overexpressed in human thyrocytes surrounded by immune cells in 100% of patients with Hashimoto's thyroiditis examined, but not in normal or Graves' thyrocytes. We conclude that functional TLR3 are present on thyrocytes; TLR3 downstream signals can be overexpressed by pathogen-related stimuli; overexpression can be reversed by phenylmethimazole to a significantly greater extent than MMI by inhibiting only the IFN regulatory factor-3/IFN-beta/signal transducers and activation of transcription arm of the TLR3 signal system; and TLR3 overexpression can induce an innate immune response in thyrocytes, which may be important in the pathogenesis of Hashimoto's thyroiditis and in the immune cell infiltrates.

The $\ensuremath{\gamma}d\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}\mathit{pn}$ reaction has been studied to search for the evidence of the ${\ensuremath{\Theta}}^{+}$ by detecting ${K}^{+}{K}^{\ensuremath{-}}$ pairs at forward angles. The Fermi-motion-corrected ${\mathit{nK}}^{+}$ invariant mass distribution shows a narrow peak at $1.524\ifmmode\pm\else\textpm\fi{}0.002+0.003$ GeV/${c}^{2}$. The statistical significance of the peak calculated from a shape analysis is 5.1 \ensuremath{\sigma}, and the differential cross section for the $\ensuremath{\gamma}n\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\Theta}}^{+}$ reaction is estimated to be $12\ifmmode\pm\else\textpm\fi{}2$ nb/sr in the photon energy range from 2.0 to 2.4 GeV in the LEPS angular range by assuming the isotropic production of the ${\ensuremath{\Theta}}^{+}$ in the $\ensuremath{\gamma}n$ center-of-mass system. The obtained results support the existence of the ${\ensuremath{\Theta}}^{+}$.

BACKGROUND: Deregulated cell cycle progression and loss of proliferation control are key properties of malignant cells. In previous studies, an interactive transcript abundance index (ITAI) comprising three cell cycle control genes, [MYC x E2F1]/p21 accurately distinguished normal from malignant bronchial epithelial cells (BEC), using a cut-off threshold of 7,000. This cut-off is represented by a line with a slope of 7,000 on a bivariate plot of p21 versus [MYC x E2F1], with malignant BEC above the line and normal BEC below the line. This study was an effort to better quantify, at the transcript abundance level, the difference between normal and malignant BEC. The hypothesis was tested that experimental elevation of p21 in a malignant BEC line would decrease the value of the [MYC x E2F1]/p21 ITAI to a level below this line, resulting in loss of immortality and limited cell population doubling capacity. In order to test the hypothesis, a p21 expression vector was transfected into the A549 human bronchogenic carcinoma cell line, which has low constitutive p21 TA expression relative to normal BEC. RESULTS: Following transfection of p21, four A549/p21 clones with stable two-fold up-regulated p21 expression were isolated and expanded. For each clone, the increase in p21 transcript abundance (TA) was associated with increased total p21 protein level, more than 5-fold reduction in E2F1 TA, and 10-fold reduction in the [MYC x E2F1]/p21 ITAI to a value below the cut-off threshold. These changes in regulation of cell cycle control genes were associated with restoration of cell proliferation control. Specifically, each transfectant was capable of only 15 population doublings compared with unlimited population doublings for parental A549. This change was associated with an approximate 2-fold increase in population doubling time to 38.4 hours (from 22.3 hrs), resumption of contact-inhibition, and reduced dividing cell fraction as measured by flow cytometric DNA analysis. CONCLUSION: These results, likely due to increased p21-mediated down-regulation of E2F1 TA at the G1/S phase transition, are consistent with our hypothesis. Specifically, they provide experimental confirmation that a line with slope of 7,000 on the p21 versus [MYC x E2F1] bivariate plot quantifies the difference between normal and malignant BEC at the level of transcript abundance.