Degree Of Confluence Research Articles

Learning strategies and procrastination as a function of need satisfaction and autonomous motivation: A diary study

AbstractWithin the framework of Self‐Determination Theory (SDT), basic psychological need satisfaction predicts quality of motivation which in turn predicts study efforts. Although studies focusing on interpersonal differences have repeatedly shown this sequence of relations, only a few have examined its stability at the intra‐personal level. In this diary study, we recruited 141 university students (M age = 20.80, SD = 2.20 years) to investigate the degree of confluence among week‐to‐week need satisfaction, quality of motivation, learning strategies, and procrastination for four weeks. Multilevel structural equation modelling showed that need satisfaction covaried positively with autonomous motivation. In turn, week‐to‐week autonomous motivation predicted positively week‐to‐week critical thinking and effort regulation and negatively procrastination. These relations emerged even after controlling for gender, age, and study hours per week. Further, contextual autonomous motivation predicted higher mean levels of critical thinking and effort regulation and lower ones of procrastination. Interestingly, a cross‐level interaction supported the sensitivity hypothesis as the negative relation between need satisfaction and controlled motivation was only true among students who were high in contextual (pre‐diary assessed) controlled motivation. These findings highlight the importance of contextual motivation and the need to establish academic environments that consistently satisfy students' psychological needs, thus promoting the quality of motivation and adaptive learning strategies.

Refining Assignment of Runoff Control Targets with a Landscape Statistical Model: A Case Study in the Beijing Urban Sub-Center, China

Rapid urbanization has triggered large changes to both the urban landscape and the yield and degree of confluence of runoff. The annual runoff volume control rate (ARVCR) is the key target identified in sponge city overall planning and is based on local natural and social conditions. However, the large impact that landscape patterns have on the runoff process causes the capacity to implement the targets to differ between those patterns. Refinement of ARVCR targets based on landscape pattern indices is therefore needed. This study identified statistical relationships between landscape indices and runoff control targets in the delta pilot region of the Beijing urban sub-center and extended the statistical model to the Beijing urban sub-center, an area almost 20 times larger than the pilot region. Landscape factors were quantified based on their area, shape, and distribution. In the delta pilot region, the runoff control volume for each block was obtained from a simulation using the SWMM model, and the correlation between landscape indices and runoff control volume capacity in different functional land-use blocks was identified by multiple linear stepwise regression. Because the distributions of landscape indices were similar in the pilot delta area and the Beijing urban sub-center, the model could be extended to the much larger study area. The statistical model provided a runoff control scheme that produced a refined assignment of the total annual runoff control target and provided guidance that could be implemented in land-use planning.

Geospatial and fluvio-geomorphological investigation of confluence dynamics of river Raidak within Himalayan foreland basin, India

ABSTRACT Confluence of river channels plays a significant role in channel avulsion, flood plain evolution and dynamics of the fluvial system. The principal objectives of the present study are (i) to analyze the direction and degree of confluence shifting through the recent past (1955–2020) by applying geospatial techniques and (ii) to find out the probable causes of confluence dynamics of the Raidak river system within quaternary geological sites of a Himalayan foreland basin in West Bengal, India, applying fluvio-geomorphological and sedimentary bank facies. Modified Normalized Difference Water Index method is also used. The result shows that the Raidak-Sankosh confluence (RSC) shifted by 9.94 km of the total distance between 1955 and 2020, whereas Raidak-I-Torsa confluence (RTC) has shifted 4.29 km overall distance during the same period. Both confluences were shifted toward the south and south-east directions. Total erosion and accretion area at the proximity of RSC and RTC has been registered as 40.1 sq km and 47.57 sq km and 39.67 sq km and 37.99 sq km, respectively, for the 65-year period. The key factors of confluence dynamics are regular flood events and channel avulsion, non-cohesive bank materials and huge channel bed sedimentation with multiple bars.

Metadiscursive Markers and Text Genre: A Metareview

Given the interest in the study of metadiscourse as the communication of ideas and the way people use language in different communicative situations, this paper attempted to find the degree of confluence between metadiscourse markers from different studies and to show how patterns of metadiscourse analysis based on various written genres can be applied to a wider range. The mean values for the frequency of marker use and their respective deviations were determined by comparing a significant number of studies on metadiscourse elements. To ensure comparability, those following Hyland’s model were chosen. The units of analysis were grouped into two broad categories based on discursive characteristics: Academic genres (research articles, theses, and textbooks) and non-academic genres, which included documents ranging from newspaper editorials or opinion columns to Internet texts and other forms of digital communication. The results of our study highlight that the disparity in interactive markers between academic and non-academic texts is relatively small. This difference has been identified by previous studies, and it is confirmed herein that the difference may be related to the use of academic language, the topic, or the object of study. In contrast, the mean values of the interactive markers in non-academic texts are considerably higher than those in academic texts. At the same time, the texts seem to be organised along two axes (interactional and interactive) in distinct areas. Despite our initial assumptions that the data would be subject to individual variations, that differences would be found between different sections of the same genre within the same academic discipline, and that the results would vary if certain texts were added or excluded, we observed certain trends in the behaviour of the documents, although it prevailed that, within each category, the texts should be studied individually.

Perceiving Revelation Here and Now: Insights from Walter Ong and Hans Urs von Balthasar

AbstractThis essay argues that the research of Walter J. Ong, S.J. (d. 2003) is an important supplement for theological aesthetics, especially of the sort espoused by Hans Urs von Balthasar. Although Ong wrote relatively little theology proper, there is a surprising degree of confluence between Ong’s leading ideas in media/communication theory and Balthasar’s ideas about how our perception of beauty is of a piece with divine revelation. I relate their respective insights in three particular areas: (1) the phenomenology of spiritual perception; (2) the role of technology vis‐à‐vis revelation; and (3) the theology of the Word of God as word.

Dynamic Proteomics Reveals High Plasticity of Cellular Proteome: Growth-Related and Drug-Induced Changes in Cancer Cells are Comparable.

In chemical proteomics, the changes occurring in cellular proteomes upon drug treatment are used to identify the drug targets and the mechanism of action. However, proteomes of cultured cells undergo also natural alteration associated with changes in the media, attaining a degree of confluence as well as due to cell division and cell metabolism. These changes are implicitly assumed to be smaller in magnitude than the drug-induced changes that ultimately lead to cell demise. In this study, it is shown that growth-related proteome changes in the untreated control group are comparable in magnitude to drug-induced changes over the course of 48 h treatment. In two well-characterized cancer cell lines, growth-related effects assessed with deep proteomics analysis (10481 proteins quantified with at least two peptides) show common trends, the steady downregulation of cell division processes, and the upregulation of metabolism-related pathways. The magnitude of these variations, which are present even before reaching 100% confluence reveals unexpectedly high plasticity of the cellular proteome. This finding reinforces the need, generally accepted in theory but not always followed in practice, to use a time-matched control when measuring drug-induced proteome changes.

Tentacle structure in freshwater bryozoans.

Tentacles are the main food-gathering organs of bryozoans. The most common design is a hollow tube of extracellular matrix (ECM), covered with ten columns of epithelial cells on the outside, and a coelothelium on the inside. Nerves follow the ECM, going between the bases of some epidermal cells. The tentacle musculature includes two bundles formed by myoepithelial cells of the coelothelium. The tentacles of freshwater (phylactolaemate) bryozoans, however, differ somewhat in structure from those of marine bryozoans. Here, we describe the tentacles of three species of phylactolaemates, comparing them to gymnolaemates and stenolaemates. Phylactolaemate tentacles tend to be longer, and with more voluminous coeloms. The composition of the frontal cell row and the number of frontal nerves is variable in freshwater bryozoans, but constant in marine groups. Abfrontal cells form a continuous row in Phylactolaemata, but occur intermittently in other two classes. Phylactolaemata lack the microvillar cuticle reported in Gymnolaemata. Abfrontal sensory tufts are always composed of pairs of mono- and/or biciliated cells. This arrangement differs from individual abfrontal ciliary cells of other bryozoans: monociliated in Stenolaemata and monociliated and multiciliated ones in Gymnolaemata. In all three groups, however, ciliated abfrontal cells probably serve as mechanoreceptors. We confirm previously described phylactolemate traits: an unusual arrangement of two-layered coelothelium lining the lateral sides of the tentacle and oral slits in the intertentacular membrane. As previously reported, tentacle movements involved in feeding differ between bryozoan groups, with phylactolaemates tending to have slower movements than both gymnolaemates and stenolaemates, and a narrower behavioral repertoire than gymnolaemates. The morphological and ultrastructural differences between the freshwater species we studied and marine bryozoans may be related to these functional differences. Muscle organization, tentacle and coelom size, and degree of confluence between tentacle and lophophore coeloms probably account for much of the observed behavioral variability.

Assessing p16 Status of Oropharyngeal Squamous Cell Carcinoma by Combined Assessment of the Number of Cells Stained and the Confluence of p16 Staining

Human papillomavirus-related oropharyngeal squamous cell carcinoma (OPSCC) has favorable prognosis relative to other head and neck squamous cell carcinomas. Criteria for predicting human papillomavirus status based upon p16 staining, including difficult cases with partial staining patterns, have been developed; however, clinical validation of these criteria and the clinical significance of partial p16 staining have not been reported. Eighty-one archival OPSCC cases were initially stained for p16 by immunohistochemistry with clone G175-405. The percentage of p16 cells and percentage of confluence of p16 cells were categorized as 25%, 26% to 75%, or >75%. Of all cases, 16 (20%) had partial p16 expression, with 26% to 75% p16 cells. Applying previously developed criteria of >75% p16 cells or >50% positive cells with >25% confluence, 48 (59%) patients were categorized p16 and demonstrated expected clinical characteristics and superior disease-free survival and overall survival (P<0.001) compared with p16 patients. By themselves, the partial staining patients had intermediate outcomes; however, separating the partial staining cases by degree of confluence showed that those with >75% confluence had superior disease-free survival (P=0.042). When the 16 original partial staining cases were re-stained with the alternative anti-p16 E6H4 clone, p16 status remained concordant for all cases, but only 3 of the 16 were interpreted as demonstrating partial staining. This report shows that the prevalence of partial p16 staining varies with the antibody utilized and clinically validates the application of a graded evaluation of both the number as well as confluence of positive cells for risk stratification of patients with OPSCC.

Reproducibility of scratch assays is affected by the initial degree of confluence: Experiments, modelling and model selection

Scratch assays are difficult to reproduce. Here we identify a previously overlooked source of variability which could partially explain this difficulty. We analyse a suite of scratch assays in which we vary the initial degree of confluence (initial cell density). Our results indicate that the rate of re-colonisation is very sensitive to the initial density. To quantify the relative roles of cell migration and proliferation, we calibrate the solution of the Fisher–Kolmogorov model to cell density profiles to provide estimates of the cell diffusivity, D, and the cell proliferation rate, λ. This procedure indicates that the estimates of D and λ are very sensitive to the initial density. This dependence suggests that the Fisher–Kolmogorov model does not accurately represent the details of the collective cell spreading process, since this model assumes that D and λ are constants that ought to be independent of the initial density. Since higher initial cell density leads to enhanced spreading, we also calibrate the solution of the Porous–Fisher model to the data as this model assumes that the cell flux is an increasing function of the cell density. Estimates of D and λ associated with the Porous–Fisher model are less sensitive to the initial density, suggesting that the Porous–Fisher model provides a better description of the experiments.

A review of factors associated with greater likelihood of suicide attempts and suicide deaths in bipolar disorder: Part II of a report of the International Society for Bipolar Disorders Task Force on Suicide in Bipolar Disorder.

Many factors influence the likelihood of suicide attempts or deaths in persons with bipolar disorder. One key aim of the International Society for Bipolar Disorders Task Force on Suicide was to summarize the available literature on the presence and magnitude of effect of these factors. A systematic review of studies published from 1 January 1980 to 30 May 2014 identified using keywords 'bipolar disorder' and 'suicide attempts or suicide'. This specific paper examined all reports on factors putatively associated with suicide attempts or suicide deaths in bipolar disorder samples. Factors were subcategorized into: (1) sociodemographics, (2) clinical characteristics of bipolar disorder, (3) comorbidities, and (4) other clinical variables. We identified 141 studies that examined how 20 specific factors influenced the likelihood of suicide attempts or deaths. While the level of evidence and degree of confluence varied across factors, there was at least one study that found an effect for each of the following factors: sex, age, race, marital status, religious affiliation, age of illness onset, duration of illness, bipolar disorder subtype, polarity of first episode, polarity of current/recent episode, predominant polarity, mood episode characteristics, psychosis, psychiatric comorbidity, personality characteristics, sexual dysfunction, first-degree family history of suicide or mood disorders, past suicide attempts, early life trauma, and psychosocial precipitants. There is a wealth of data on factors that influence the likelihood of suicide attempts and suicide deaths in people with bipolar disorder. Given the heterogeneity of study samples and designs, further research is needed to replicate and determine the magnitude of effect of most of these factors. This approach can ultimately lead to enhanced risk stratification for patients with bipolar disorder.

Characteristics and viral propagation properties of a new human diploid cell line, walvax-2, and its suitability as a candidate cell substrate for vaccine production

Human diploid cell strains (HDCSs), possessing identical chromosome sets known to be free of all known adventitious agents, are of great use in developing human vaccines. However it is extremely difficult to obtain qualified HDCSs that can satisfy the requirements for the mass production of vaccines. We have developed a new HDCS, Walvax-2, which we derived from the lung tissue of a 3-month-old fetus. We established primary, master and working cell banks successfully from reconstituted frozen cells. Observations during the concurrent propagation of Walvax-2 and MRC-5 cells revealed differences in terms of growth rate, cell viability and viral sensitivities. Specifically, Walvax-2 cells replicated more rapidly than MRC-5 cells, with Walvax-2 cells attaining the same degree of confluence in 48 hours as was reached by MRC-5 cells in 72 hours. Moreover, Walvax-2 cells attained 58 passages of cell doublings whereas MRC-5 reached 48 passages during this period. We also assessed the susceptibility of these cells to rabies, hepatitis A, and Varicella viruses. Analysis of virus titers showed the Walvax-2 cells to be equal or superior to MRC-5 cells for cultivating these viruses. Furthermore, in order to characterize the Walvax-2 cell banks, a series of tests including cell identification, chromosomal characterization, tumorigenicity, as well as tests for the presence of microbial agents, exogenous viruses, and retroviruses, were conducted according to standard international protocols. In conclusion, results from this study show that Walvax-2 cell banks are a promising cell substrate and could potentially be used for the manufacturing of HDCVs.

Selection and Tuning of a Fast and Simple Phase-Contrast Microscopy Image Segmentation Algorithm for Measuring Myoblast Growth Kinetics in an Automated Manner

Acquiring and processing phase-contrast microscopy images in wide-field long-term live-cell imaging and high-throughput screening applications is still a challenge as the methodology and algorithms used must be fast, simple to use and tune, and as minimally intrusive as possible. In this paper, we developed a simple and fast algorithm to compute the cell-covered surface (degree of confluence) in phase-contrast microscopy images. This segmentation algorithm is based on a range filter of a specified size, a minimum range threshold, and a minimum object size threshold. These parameters were adjusted in order to maximize the F-measure function on a calibration set of 200 hand-segmented images, and its performance was compared with other algorithms proposed in the literature. A set of one million images from 37 myoblast cell cultures under different conditions were processed to obtain their cell-covered surface against time. The data were used to fit exponential and logistic models, and the analysis showed a linear relationship between the kinetic parameters and passage number and highlighted the effect of culture medium quality on cell growth kinetics. This algorithm could be used for real-time monitoring of cell cultures and for high-throughput screening experiments upon adequate tuning.

Applying Quantitative Analysis Techniques to La flexió verbal en els dialectes catalans

Abstract The Majorcan dialectologist Antoni M. Alcover (1862–1932) was the first researcher to record information for use in the study of the conjugation of Catalan verbs. He compiled almost 500,000 verb forms corresponding to the complete conjugation of 75 verbs in 149 localities in the Catalan-speaking area. These data were published under the title “La flexió verbal en els dialectes catalans”. From 1999, work began to complete and computerize these materials in order to make them accessible to scholars in the field and to the public. These computer applications have a descriptive character: they show dialectal and subdialectal areas, and isoglosses, in a graphic form. However, it is also possible to use these materials from an interpretative point of view. The aim of this paper is to apply a suitable dialectometric analysis to the “Verbal flexion” materials, which can only be interpreted using quantitative analysis techniques. Taking multiple answers into account, we use the calculation of the Mean Degree of Confluence and we compare the results with the dialectometric analysis obtained applying Hans Goebl's methodology, which is based on the use of single answers.

The use of confluence stages does not decrease the overall variability in primary human osteoblasts but can give additional information on differentiation in vitro.

Primary cultures of human osteoblast-like cells are frequently used to study osteoblast function. Due to inhomogeneous growth of primary osteoblasts in culture, it is of interest if the use of confluence stages for analysis would reduce the overall variability. Consequently, we have tested the influence of degree of confluence and passage number on the growth and differentiation of human primary osteoblast-like cells. Phenotypic features of primary human osteoblast-like cells were compared at four successive cell densities defined as stage of confluence I (50%), stage II (75%), stage III (100%) and stage IV (5 days post confluence). The stability of the system was also tested by comparing these observations obtained using cells from the 2nd and 4th passages. As a sign for further differentiation, the number of AP-positive cells increased with a decrease in proliferation. The secretion of procollagen-I decreased to 50% during culture while procollagen I mRNA doubled from proliferation to confluence. A constant activity of alkaline phosphatase, procollagen-I secretion and procollagen I gene expression over passages was seen together with a decrease in growth. The paper introduces a potential model of osteoblastic differentiation in vitro for human primary osteoblast-like cells. We were able to show an increasing differentiation with a decrease in proliferation and the stability of this differentiation behaviour over cell passages in this model, but we were not able to reduce the overall variability.

Effects of cell type and culture media on Interleukin-6 secretion in response to environmental particles

Cultured lung cells provide an alternative to animal exposures for comparing the effects of different types of air pollution particles. Studies of particulate matter in vitro have reported proinflammatory cytokine signaling in response to many types of environmental particles, but there have been few studies comparing identical treatments in multiple cell types or identical cells with alternative cell culture protocols. We compared soil-derived, diesel, coal fly ash, titanium dioxide, and kaolin particles along with soluble vanadium and lipopolysaccharide, applied to airway-derived cells grown in submerged culture. Cell types included A549, BEAS-2B, RAW 264.7, and primary macrophages. The cell culture models (specific combinations of cell types and culture conditions) were reproducibly different in the cytokine signaling responses to the suite of treatments. Further, Interleukin-6 (IL-6) response to the treatments changed when the same cells, BEAS-2B, were grown in KGM versus LHC-9 media or in media containing bovine serum. The effect of changing media composition was reversible over multiple changes of media type. Other variables tested included culture well size and degree of confluence. The observation that sensitivity of a cell type to environmental agonists can be manipulated by modifying culture conditions suggests a novel approach for studying biochemical mechanisms of particle toxicity.

Different expression role among glutamate transporters in rat retinal glial cells under various culture conditions

Using cultured rat retinal glial cells, the changes in the expression of glutamate transporters (GLTs) under such conditions as the degree of confluence of the cells, hypoxia, glutamate loading, and potassium loading, were assessed. After the retinal glial cells were isolated from 3-day-old Sprague–Dawley rats, GLAST, GLT-1, and EAAC1 mRNA expression was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and their protein expression was confirmed by Western blot analysis and immunostaining. Changes in the expression of the GLTs at 6 h after passage and at confluence, during culture in 5% oxygen, during glutamate loading and during potassium loading were assessed using real-time PCR. Although the GLAST mRNA expression was increased during glutamate and potassium loading, no changes in the expression were observed during hypoxia and at confluence. By contrast, the GLT-1 mRNA expression was increased during hypoxia and at confluence, but not during glutamate and potassium loading, and the EAAC1 mRNA expression was not changed only during glutamate loading. The expression of EAAC1 in the cultured retinal glial cells was confirmed. The expression of the GLTs varied according to the environment and the type of load suggests that the involvement of the GLTs in retinal physiology and pathology varies depending on the subtype.

Ciliary function of polycystins: a new model for cystogenesis.

Autosomal dominant polycystic kidney disease results from loss-of-function mutations in either polycystin-1 (Pc-1) or polycystin-2 (Pc-2). These transmembrane proteins directly interact through cytosolic domains of their C-termini. Pc-1 has been implicated in cell– extracellular matrix (ECM) interactions at focal adhesion contacts, but also in cell–cell interactions at tight junctions, adherens junctions and desmosomes [1]. Pc-2, located to the plasma membrane and/or to the endoplasmic reticulum [2,3], was shown to increase the intracytosolic calcium from both ER stocks and extracellular milieu [4]. The variability of polycystin localization within the cell may be explained by differences in antibody characteristics, cell type, degree of confluence, developmental stage, but also raises the hypothesis of multiple biological functions [1]. The large extracellular domain of Pc-1 is thought to transduce signals from the environment into the cells, through Pc-1-dependent signalling pathways and through activation of PC-2 calcium channel properties. However, the search for polycystin ligands and functions at sites of cell–cell or cell–ECM interactions has remained elusive to date. In fact, the first recently reported biological function of polycystins depends on an additional and unexpected polycystin subcellular localization—the renal primary cilia—and is triggered by an unexpected ligand, the urinary flow.

8] Determination of intracellular reactive oxygen species as function of cell density

Reactive oxygen species (ROS) such as superoxide (O 2 – ) hydrogen peroxide (H 2 O 2 ), and nitric oxide (NO), generated by activated phagocytes, are crucial for the immune response against pathogens. It has become evident that ROS, while responsible for indiscriminate oxidative cell damage when released in excess amounts, can also, at low concentrations and in very limited time frames, behave as fine modulators of important intracellular events, such as protein phosphorylation and gene transcription, through which the cell response to environmental stimuli is triggered. In view of these considerations, a protocol in which the intracellular production of oxygen species grown at different plating densities is evaluated in single cells by flow cytometry after cell loading with the peroxide-sensitive probe dichlorofluorescein diacetate (DCF-DA) and following rapid detachment from the substrate. A flow chart summarizing the basic protocol for determination of intracellular ROS at different plating densities is also presented. A method to evaluate the intracellular content of oxidants as a function of cell density—that is, in cells plated at different degree of confluence is developed. The method is based on the cytofluorimetric analysis of the oxidative modification of a widely used probe, dichlorofluorescein diacetate that gains a bright green fluorescence on interaction with hydrogen peroxide and organic peroxides.

A Biologically Based Model of Growth and Senescence of Syrian Hamster Embryo (SHE) Cells after Exposure to Arsenic

We modified the two-stage Moolgavkar-Venzon-Knudson (MVK) model for use with Syrian hamster embryo (SHE) cell neoplastic progression. Five phenotypic stages are proposed in this model: Normal cells can either become senescent or mutate into immortal cells followed by anchorage-independent growth and tumorigenic stages. The growth of normal SHE cells was controlled by their division, death, and senescence rates, and all senescent cells were converted from normal cells. In this report, we tested the modeling of cell kinetics of the first two phenotypic stages against experimental data evaluating the effects of arsenic on SHE cells. We assessed cell division and death rates using flow cytometry and correlated cell division rates to the degree of confluence of cell cultures. The mean cell death rate was approximately equal to 1% of the average division rate. Arsenic did not induce immortalization or further mutations of SHE cells at concentrations of 2 microM and below, and chromium (3.6 microM) and lead (100 microM) had similar negative results. However, the growth of SHE cells was inhibited by 5.4 microM arsenic after a 2-day exposure, with cells becoming senescent after only 16 population doublings. In contrast, normal cells and cells exposed to lower arsenic concentrations grew normally for at least 30 population doublings. The biologically based model successfully predicted the growth of normal and arsenic-treated cells, as well as the senescence rates. Mechanisms responsible for inducing cellular senescence in SHE cells exposed to arsenic may help explain the apparent inability of arsenic to induce neoplasia in experimental animals.

A biologically based model of growth and senescence of Syrian hamster embryo (SHE) cells after exposure to arsenic.

We modified the two-stage Moolgavkar-Venzon-Knudson (MVK) model for use with Syrian hamster embryo (SHE) cell neoplastic progression. Five phenotypic stages are proposed in this model: Normal cells can either become senescent or mutate into immortal cells followed by anchorage-independent growth and tumorigenic stages. The growth of normal SHE cells was controlled by their division, death, and senescence rates, and all senescent cells were converted from normal cells. In this report, we tested the modeling of cell kinetics of the first two phenotypic stages against experimental data evaluating the effects of arsenic on SHE cells. We assessed cell division and death rates using flow cytometry and correlated cell division rates to the degree of confluence of cell cultures. The mean cell death rate was approximately equal to 1% of the average division rate. Arsenic did not induce immortalization or further mutations of SHE cells at concentrations of 2 microM and below, and chromium (3.6 microM) and lead (100 microM) had similar negative results. However, the growth of SHE cells was inhibited by 5.4 microM arsenic after a 2-day exposure, with cells becoming senescent after only 16 population doublings. In contrast, normal cells and cells exposed to lower arsenic concentrations grew normally for at least 30 population doublings. The biologically based model successfully predicted the growth of normal and arsenic-treated cells, as well as the senescence rates. Mechanisms responsible for inducing cellular senescence in SHE cells exposed to arsenic may help explain the apparent inability of arsenic to induce neoplasia in experimental animals.