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PubMed1996

Quantal Ca2+ release and inactivation in a model of the inositol 1,4,5-trisphosphate receptor involving transformation of the ligand by the receptor.

A model explaining quantal Ca2+ release as an intrinsic property of the inositol 1,4,5-triphosphate (IP3) receptor has been put forward. The model is based on the hypothesis that the IP3 receptor can catalyze a transformation of the IP3 molecule differing from its conventional metabolism. A simple kinetic mechanism is considered, in which IP3-induced Ca2+ channel opening is followed by the step of IP3 conversion and channel closure. Examination of the resulting mathematical model shows that it can reproduce well both partial release of stored Ca2+ and the same responsiveness to subsequent IP3 additions. On incorporation of an additional closed state of the channel, the model describes also a time-dependent channel inactivation at a high IP3 dose. Temperature sensitivity of the catalytic step accounts for the reported elimination of quantal responses and inactivation at low temperature. The transformation product is surmised to be a positional or stereo isomer of IP3.

Calcium↗
PubMed2006

Reductive dechlorination of 1,2,4-trichlorobenzene with palladized nanoscale Fe(zero-valent) particles supported on chitosan and silica.

In this study, nanoscale Pd-Fe particles, with diameters less than 100 nm, were synthesized and dispersed over the chitosan and silica supports. Three different Pd-Fe particles were synthesized, namely 0.1% Pd-Fe, 0.5% Pd-Fe and 1.0% Pd-Fe. SEM images confirmed that the Pd-Fe particles were dispersed over the surface of the supports while SEM-EDX confirmed evenly distribution of Pd over Fe(zero-valent). alpha-Fe(zero-valent) crystallites were identified by means of XRD and observed in TEM. Reductive dechlorinations of 1,2,4-trichlorobenzene (1,2,4-TCB) with the nanoscale Pd-Fe/chitosan and Pd-Fe/silica were carried out in the batch experiment system. Disappearance of the parent species and formation of the reaction intermediates and end product were monitored at discrete times. The results show that the nano-scale Pd-Fe particles were able to completely dechlorinate the chlorinated benzenes within a very short timescale. Complete dechlorinations of 1,2,4-TCB to benzene were achieved within 60 min with the 1.0% Pd-Fe/chitosan and within 100 min with the 1.0% Pd-Fe/silica. Reaction rates were observed to increase with increasing Pd content of the Pd-Fe/support. The reactions apparently followed pseudo-first-order kinetics with respect to the 1,2,4-TCB transformation. A kinetic model is constructed to fit the experimental results for the reactions, enabling identification of the major and minor dechlorination pathways of 1,2,4-TCB. The model suggests that the 1,2,4-TCB transformation mainly followed the primary pathway of direct reductive dechlorination to benzene and secondary pathway of sequential hydrogenolysis to 1,2-dichlorobenzene (1,2-DCB) and then chlorobenzene (CB) or benzene.

Chitosan↗
PubMed1998

Identification of patterns of neuronal connectivity--partial spectra, partial coherence, and neuronal interactions.

The cross-correlation histogram has provided the primary tool for inferring the structure of common inputs to pairs of neurones. While this technique has produced useful results it not clear how it may be extended to complex networks. In this report we introduce a linear model for point process systems. The finite Fourier transform of this model leads to a regression type analysis of the relations between spike trains. An advantage of this approach is that the full range of techniques for multivariate regression analyses becomes available for spike train analysis. The two main parameters used for the identification of neural networks are the coherence and partial coherences. The coherence defines a bounded measure of association between two spike trains and plays the role of a squared correlation coefficient defined at each frequency lambda. The partial coherences, analogous to the partial correlations of multiple regression analysis, allow an assessment of how any number of putative input processes may influence the relation between any two output processes. In many cases analytic solutions may be found for coherences and partial coherences for simple neural networks, and in combination with simulations may be used to test hypotheses concerning proposed networks inferred from spike train analyses.

Animals↗
PubMed1996

Dynamic behavior of lung parenchyma in shear.

Dynamic shear properties of excised rabbit lungs were studied by measuring creep deformation after application of a step indentation force to the pleural surfaces by a rigid cylindrical punch. The punch diameter was 9.5 mm, and punch forces were 2,4, and 6 g. Measurements were made at lung volumes of 40, 60, and 90% of the total lung capacity before and after lavage with 3-dimethyl siloxane, which provided a constant surface tension of 16 dyn/cm at the alveolar surfaces. A power-law model was fitted to creep data and then transformed into the frequency (f) domain by using Laplace transforms. The optimum model parameters were used to calculate shear elastance (E mu), shear resistance (R mu), and shear hysteresivity (2 pi fR mu/E mu) between 0.01 and 2.0 Hz. It was found that E mu slightly increased and R mu decreased nearly hyperbolically with increasing f, both decreased with increasing indentation force, and both increased with increasing mean lung volume. Shear hysteresivity decreased sharply from 0.01 to 0.25 Hz and then assumed a nearly steady value that was an order of magnitude lower than the value reported previously for uniformly oscillated lungs. Changes in E mu and R mu after lavage were correlated with changes in transpulmonary pressure and not with changes in surface film properties. These results suggest that in the breathing range of frequencies 1) the energy loss of lung parenchyma is a much smaller fraction of the stored elastic energy in shear than in uniformly oscillated lungs and 2) transpulmonary pressure, not dynamic properties of surface film, is the primary determinant of lung dynamic properties in shear.

Animals↗
PubMed2005

[Expression of nuclear transcription factor kappaB in hamster buccal pouch carcinogenesis].

OBJECTIVE: To study the expression and significance of p65 which is an important subtype of nuclear transcription factor kappaB (NF-kappaB) and its inhibitory protein IkappaBalpha in malignant transformation of hamster buccal mucosa. METHODS: The animal model of malignant transformation in hamster buccal mucosa induced by DMBA (0.5%) was established. Twelve paired specimens including normal buccal mucosa, epithelial hyperplasia, epithelial dysplasia and squamous cell carcinoma (SCC) were subjected to Western blot for the analysis of p65. The expression of IkappaBalpha was observed in 22 normal buccal epithelia, 20 hyperplasia epithelia, 35 dysplasia epithelia and 23 SCC by immunohistochemical evaluation. RESULTS: In normal buccal epithelia and hyperplasia epithelia, the expression of p65 was not obvious, and there was no significant difference between them (P > 0.05). The expression of IkappaBalpha existed at large, but mostly localizing in cell cytoplasmic staining in the basal cell layer and bottom of spinocelluar layer. With the occurrence of epithelia dysplasia, the expression of p65 gradually increased, comparing with normal buccal epithelia and hyperplasia epithelia (P < 0.01). But the positive intensity of IkappaBalpha was dramatically decreased (P < 0.05). In SCC, p65 expressed at a higher level comparing with normal buccal mucosa and dysplasia (P < 0.01), while the staining of IkappaBalpha was feedbackly higher comparing with dysplasia (P < 0.01) and even with normal buccal mucosa (P < 0.01). CONCLUSION: NF-kappaB p65 is strongly activated in malignant transformation of hamster buccal mucosa. The abnormal expression of p65 and IkappaBalpha, especially the ascending expression of p65 as well as the descending expression of IkappaBalpha in dysplasia may be an early event during oral carcinogenesis, and can be used as biomarkers for supervising oral malignancy.

Animals↗
PubMed2001

Correlated hit probability and cell transformation in an effect-specific track length model applied to in vitro alpha irradiation.

In estimating the risk from low doses of alpha particles such as those emitted by radon progeny, it is important to consider the correlation between cellular inactivation and transformation that can exist at the cellular level. A phenomenological model of radiation-induced cellular inactivation and transformation at this level is presented here which incorporates aspects of a state vector model of radiation carcinogenesis and of correlated hit probabilities for inactivation and transformation. The general form of the model assumes that both inactivation and initial initiation damage are produced through the interaction of sublesions induced by radiation passing through cell nuclei, with the production of sublesions governed by hit probabilities and a characteristic probability-per-unit track length. The inactivation and initiation events are partially correlated through the use of hit probabilities. In addition, promotional events are incorporated for the case of cellular transformation based on a previously published state vector model. The model provides good fits to available data on the relationship between inactivation, transformation and LET for doses of alpha above 0.1 Gy in the range of LETs commonly produced by radon and progeny; by "good fits" we mean here the ability to yield the correct shapes of dose-response data using parameter values that vary smoothly with LET and using inactivation parameters that are applied consistently between inactivation and transformation assays. The resulting model correctly predicts recent findings indicating an increased transformation frequency per surviving cell when a population receives a distribution of hits compared to irradiation where all cells receive the same number of hits.

Animals↗
PubMed1999

Planning and managing computerized order entry: a case study of IT-enabled organizational transformation.

This article uses a model for technology-enabled organizational transformation to analyze a case study of computerized order entry at a medium-sized, urban hospital. The hospital achieved initial goals for direct order entry by physicians and improvements in patient care and is now using the system to implement disease management policies. The authors use the model to examine decisions and actions that facilitated or constrained effective implementation of the system and discuss the model's implications for managing implementation of computerized order entry technologies in health care systems.

Decision Support Systems, Clinical↗
PubMed2000

Expression of transforming growth factor-beta1 and its receptors related to the ureteric fibrosis in a rat model of obstructive uropathy.

PURPOSE: Transforming growth factor (TGF-beta) is a multifunctional cytokine that may stimulate fibroblast proliferation and regulate the synthesis of matrix components. To elucidate the role of TGF-beta1 in the process of ureteric fibrosis in obstructive uropathy, we conducted this study. MATERIALS AND METHODS: The expression of TGF-beta1 and TGF-beta receptors I, II, III were studied in 54 rats by the method of immunohistochemistry. RESULTS: The degree of smooth muscle hypertrophy and serosa thickening aggravated gradually along the course of ureteric ligation. The expression of TGF-beta1 in the serosa layer was noticed from day 7 after ligation. The expression of TGF-beta1 and receptors in the serosa layer progressively increased during the period of ureteric obstruction, reached a peak on day 21 after ligation, and then declined. The expression of TGF-beta1 and TGF-beta receptors (II and III) in the serosa layer was correlated significantly (r = 0.8048 and 0.7974, respectively; p values both <0.0001). The expression of TGF-beta1 also correlated significantly with the thickening of serosa layer and the severity of hydroureter (r = 0.6921 and 0.5394, respectively; p values both <0.005). The expression of TGF-beta1 and TGF-beta receptors in the smooth muscle layer was transient and weak, and the expression of TGF-beta1 and TGF-beta receptors was accompanied with the fibrosis in the muscle layer. CONCLUSIONS: We conclude that TGF-beta1 might participate in the progression ofureteric fibrosis in obstructed ureters.

Animals↗
PubMed2002

A comparison of methods to handle skew distributed cost variables in the analysis of the resource consumption in schizophrenia treatment.

BACKGROUND: Transformation of the dependent cost variable is often used to solve the problems of heteroscedasticity and skewness in linear ordinary least square regression of health service cost data. However, transformation may cause difficulties in the interpretation of regression coefficients and the retransformation of predicted values. AIMS OF THE STUDY: The study compares the advantages and disadvantages of different methods to estimate regression based cost functions using data on the annual costs of schizophrenia treatment. METHODS: Annual costs of psychiatric service use and clinical and socio-demographic characteristics of the patients were assessed for a sample of 254 patients with a diagnosis of schizophrenia (ICD-10 F 20.0) living in Leipzig. The clinical characteristics of the participants were assessed by means of the BPRS 4.0, the GAF, and the CAN for service needs. Quality of life was measured by WHOQOL-BREF. A linear OLS regression model with non-parametric standard errors, a log-transformed OLS model and a generalized linear model with a log-link and a gamma distribution were used to estimate service costs. For the estimation of robust non-parametric standard errors, the variance estimator by White and a bootstrap estimator based on 2000 replications were employed. Models were evaluated by the comparison of the R2 and the root mean squared error (RMSE). RMSE of the log-transformed OLS model was computed with three different methods of bias-correction. The 95% confidence intervals for the differences between the RMSE were computed by means of bootstrapping. A split-sample-cross-validation procedure was used to forecast the costs for the one half of the sample on the basis of a regression equation computed for the other half of the sample. RESULTS: All three methods showed significant positive influences of psychiatric symptoms and met psychiatric service needs on service costs. Only the log- transformed OLS model showed a significant negative impact of age, and only the GLM shows a significant negative influences of employment status and partnership on costs. All three models provided a R2 of about.31. The Residuals of the linear OLS model revealed significant deviances from normality and homoscedasticity. The residuals of the log-transformed model are normally distributed but still heteroscedastic. The linear OLS model provided the lowest prediction error and the best forecast of the dependent cost variable. The log-transformed model provided the lowest RMSE if the heteroscedastic bias correction was used. The RMSE of the GLM with a log link and a gamma distribution was higher than those of the linear OLS model and the log-transformed OLS model. The difference between the RMSE of the linear OLS model and that of the log-transformed OLS model without bias correction was significant at the 95% level. As result of the cross-validation procedure, the linear OLS model provided the lowest RMSE followed by the log-transformed OLS model with a heteroscedastic bias correction. The GLM showed the weakest model fit again. None of the differences between the RMSE resulting form the cross- validation procedure were found to be significant. DISCUSSION: The comparison of the fit indices of the different regression models revealed that the linear OLS model provided a better fit than the log-transformed model and the GLM, but the differences between the models RMSE were not significant. Due to the small number of cases in the study the lack of significance does not sufficiently proof that the differences between the RSME for the different models are zero and the superiority of the linear OLS model can not be generalized. The lack of significant differences among the alternative estimators may reflect a lack of sample size adequate to detect important differences among the estimators employed. Further studies with larger case number are necessary to confirm the results. IMPLICATIONS: Specification of an adequate regression models requires a careful examination of the characteristics of the data. Estimation of standard errors and confidence intervals by nonparametric methods which are robust against deviations from the normal distribution and the homoscedasticity of residuals are suitable alternatives to the transformation of the skew distributed dependent variable. Further studies with more adequate case numbers are needed to confirm the results.

Adolescent↗
PubMed1996

Method for quantitative assessment of transformation of non-micellar cholesterol carriers in model bile systems.

Aggregation and fusion of non-micellar particulate species, such as unilamellar vesicle and phospholipid lamellae, are believed to precede the nucleation of cholesterol crystals in bile. However, little is known about the time sequence relationship between transformation of non-micellar particles and the initial appearance of cholesterol crystals, as no adequate technique is available for assessing such transformations quantitatively. We have developed a novel method for quantitatively estimating vesicle transformation in supersaturated model bile systems, using a spectrophotometric technique to determine the time sequence relationship between such transformations and cholesterol crystal nucleation. We also investigated the potency of a given effector substance on this transformation. This method permits simultaneous quantitative determination of vesicle aggregation and of cholesterol crystal growth. Maximal vesicular aggregation as determined from turbidity, coincided with initiation of cholesterol crystal nucleation. The addition of divalent cations, Ca2+ and Mg2+, to the model bile solutions promoted vesicle aggregation and cholesterol crystal nucleation and growth. In contrast, apolipoproteins A-1 and A-2 retarded such processes. These data were highly reproducible and reliable. The method described is easy to perform, provides reproducible results and permits the determination of the potency of effector substances on vesicle transformation and on the nucleation of cholesterol crystals.

Bile↗
PubMed2001

In vitro model of microglial deramification: ramified microglia transform into amoeboid phagocytes following addition of brain cell membranes to microglia-astrocyte cocultures.

Changes in the morphology of ramified microglia are a common feature in brain pathology and culminate in the appearance of small, rounded, microglia-derived phagocytes in the presence of neural debris. Here, we explored the effect of adding brain cell membranes on the morphology of alphaMbeta2-integrin (CD11b/CD18, CR3) positive microglia cultured on a confluent astrocyte substrate as an in vitro model of deramification. Addition of brain membranes led to a loss of microglial ramification, with full transformation to small, rounded, macrophages at 20-40 microg/ml. Time course studies showed a rapid response, with first effects at 1-3 hours, and full transformation at 24-48 hours. Removal of cell membranes and exchange of the culture medium led to a similarly rapid process of reramification. Comparison of cell membranes from different tissues at 20 microg/ml showed strong transforming effect for the brain, more moderate for kidney and liver, and very weak for spleen and skeletal muscle. Fluorescent labeling of brain membranes revealed uptake by almost all rounded macrophages, by a subpopulation of glial fibrillary acidic protein (GFAP)-positive astrocytes, but not by ramified microglia. Phagocytosis of inert fluorobeads did not lead to a transformation into macrophages but their phagocytosis was inhibited by brain membranes, pointing to a saturable uptake mechanism. In summary, addition of brain cell membranes and their phagocytosis leads to a rapid and reversible loss of ramification. The differences in transforming activity from different tissues and the absence of effect from phagocytosed fluorobeads suggest, however, the need for a second stimulus following the phagocytosis of cell debris.

Animals↗
PubMed1989

Overexpression of amyloid precursor protein A4 (beta-amyloid) immunoreactivity in genetically transformed cells: implications for a cellular model of Alzheimer amyloidosis.

Among the major obstacles to clarifying molecular mechanisms involved in amyloid metabolism in Alzheimer disease has been the unavailability of laboratory models for this uniquely human disorder. The present studies were aimed at establishing genetically engineered cell lines that overexpress amyloid immunoreactivity and that may be relevant to amyloid accumulation in the Alzheimer disease brain. We used cloned amyloid cDNA that contains a region encoding A4 (beta-polypeptide) amino acids along with recently developed tumor virus vectors derived from simian virus 40 to prepare transformed cells. After transient and permanent transfection, a variety of cell types overexpressed A4 immunoreactivity that was detected by highly specific monoclonal antibodies. We observed that the use of an amyloid subdomain containing the A4 region, but lacking the sequence of a Kunitz-type protease inhibitor found in amyloid precursor protein variants, was sufficient to obtain cells that overproduced an A4 epitope. The transformed cells were readily propagated in culture and may provide an experimental medium to elucidate aspects of the molecular pathogenesis of Alzheimer disease. The cellular models may also serve as tools for deriving potentially useful therapeutic agents.

Alzheimer Disease↗
PubMed1979

Mathematical models and the statistical analyses of cell transformation experiments.

Statistical methods are developed and applied to the fitting of the one-hit curves to chemically induced transformations in Syrian hamster colonies. Data from several experiments in two laboratories are shown to fit the model well at all but the highest doses of benzo(a)pyrene. The ratio of the estimated parameters of the one-hit curves ("transformicities") is proposed as a measure of the enhancement by X-irradiation. Statistical tests for possible nonrandom variation among dishes are developed for the situation where a sample of dishes is used to estimate the total number of surviving cells. The methods of fitting and estimation are also extended to this case. Further analyses exclude selection as an explanation for the observed increase in transformation frequency with increased carcinogen concentration. The reproducibility of the fit of the one-hit model and the radiation enhancement measures is ascribed to the uniqueness of this in vitro system in which the direct target cell-insult interaction is not modulated by host intervention.

Animals↗
PubMed1998

Disruption of redox homeostasis in the transforming growth factor-alpha/c-myc transgenic mouse model of accelerated hepatocarcinogenesis.

In previous studies we have demonstrated that transforming growth factor (TGF)-alpha/c-myc double transgenic mice exhibit an enhanced rate of cell proliferation, accumulate extensive DNA damage, and develop multiple liver tumors between 4 and 8 months of age. To clarify the biochemical events that may be responsible for the genotoxic and carcinogenic effects observed in this transgenic model, several parameters of redox homeostasis in the liver were examined prior to development of hepatic tumors. By 2 months of age, production of reactive oxygen species, determined by the peroxidation-sensitive fluorescent dye, 2',7'-dichlorofluorescin diacetate, was significantly elevated in TGF-alpha/c-myc transgenic hepatocytes versus either wild type or c-myc single transgenic cells, and occurred in parallel with an increase in lipid peroxidation. Concomitantly with a rise in oxidant levels, antioxidant defenses were decreased, including total glutathione content and the activity of glutathione peroxidase, whereas thioredoxin reductase activity was not changed. However, hepatic tumors which developed in TGF-alpha/c-myc mice exhibited an increase in thioredoxin reductase activity and a very low activity of glutathione peroxidase. Furthermore, specific deletions were detected in mtDNA as early as 5 weeks of age in the transgenic mice. These data provide experimental evidence that co-expression of TGF-alpha and c-myc transgenes in mouse liver promotes overproduction of reactive oxygen species and thus creates an oxidative stress environment. This phenomenon may account for the massive DNA damage and acceleration of hepatocarcinogenesis observed in the TGF-alpha/c-myc mouse model.

Animals↗
PubMed2005

Animal models for human T-lymphotropic virus type 1 (HTLV-1) infection and transformation.

Over the past 25 years, animal models of human T-lymphotropic virus type 1 (HTLV-1) infection and transformation have provided critical knowledge about viral and host factors in adult T-cell leukemia/lymphoma (ATL). The virus consistently infects rabbits, some non-human primates, and to a lesser extent rats. In addition to providing fundamental concepts in viral transmission and immune responses against HTLV-1 infection, these models have provided new information about the role of viral proteins in carcinogenesis. Mice and rats, in particular immunodeficient strains, are useful models to assess immunologic parameters mediating tumor outgrowth and therapeutic invention strategies against lymphoma. Genetically altered mice including both transgenic and knockout mice offer important models to test the role of specific viral and host genes in the development of HTLV-1-associated lymphoma. Novel approaches in genetic manipulation of both HTLV-1 and animal models are available to address the complex questions that remain about viral-mediated mechanisms of cell transformation and disease. Current progress in the understanding of the molecular events of HTLV-1 infection and transformation suggests that answers to these questions are approachable using animal models of HTLV-1-associated lymphoma.

Animals↗
PubMed1997

Quantitative changes in cytoskeletal and nuclear actins during cellular transformation.

Actin, a highly conserved protein comprising cell stress fibers and other cellular structures, is found in both the cytoplasm and nucleus of cells and responds to both epigenetic signals and altered gene expression occurring during tumorigenesis. We have previously shown that changes in the cytoplasmic F- and G-actin ratios reflect bladder cancer risk. To determine whether nuclear actin is also altered and how nuclear and cytoplasmic actin alterations are interrelated in transformation, an in vitro model of carcinogen-induced transformation consisting of 2 human uroepithelial cell lines immortalized by infection with SV-40 was studied. One line, HUC-PC, is tumorigenic in nude mice after incubation with the carcinogen 4-ABP, the other, HUC-BC, is not. Cytoplasmic and nuclear F- and G-actin were determined by QFIA on individual cells using fluorochrome-labeled phallicidin and DNase, I, respectively. Before exposure to 4-ABP, the PC cells had lower cytoplasmic F-actin content, higher cytoplasmic G-actin content, but similar levels of nuclear G- and F-actin in comparison to the BC cells. After incubation with 4-ABP, F-actin decreased and G-actin increased in both cytoplasm and nuclei of PC cells and cytoplasmic F-actin fibers were lost, but only cytoplasmic actin was altered in the BC cells. Northern blot analysis showed the expression of the beta-actin gene was only approximately 20% lower in 4-ABP-treated PC cells than in untreated controls, indicating the cellular change in actin was attributed to a shift between F- and G-actin proteins rather than to net actin synthesis.

Actins↗
PubMed1989

Co-regulation of metastatic and transforming activity of normal and mutant ras genes.

We have analyzed the metastatic properties of NIH-3T3 cells transformed by H-ras activated through over-expression and/or mutation. Our results reveal that elevated expression of H-ras proto-oncogene can induce the complete metastatic phenotype. Cells transformed by the proto-oncogene have a lower metastatic potential than those transformed by a mutated ras gene. ras oncogenes activated through alterations in codon 12 which encode p21 molecules with impaired GTPase activity, or in codon 59 which produce p21 molecules that release bound guanine nucleotide faster, or in codon 61 which produce p21 having impaired GTPase activity and altered nucleotide release properties, are all able to induce the metastatic phenotype. Leucine-61-activated oncogenes with an additional mutation in codons 116, 117 or 119, resulting in a reduced affinity for guanine nucleotides, are also capable of inducing metastatic behavior. These data indicate that ras genes which are capable of transforming are also capable of inducing the full metastatic phenotype in NIH-3T3 cells. This suggests that both phenotypes are induced through an increase in p21-GTP concentration in ras-transformed cells. This established model for ras-mediated transformation can also explain the qualitative and quantitative regulation of metastatic behavior by ras.

Animals↗
PubMed2003

Introducing the emission process of hydrogen sulfide to a sewer process model (WATS).

Emission of hydrogen sulfide in sewer networks results in odor, health and corrosion problems. These problems generally occur when wastewater is transported under anaerobic and turbulent conditions. Studies on integrated aerobic/anaerobic processes in sewers have led to a conceptual sewer process model, WATS (Wastewater Aerobic/anaerobic Transformations in Sewers). The WATS model accounts for the carbon cycle, reaeration and sulfide formation. However, to handle odor, health and corrosion problems more efficiently, other aspects of the sulfur cycle need to be included. Emphasis in this study is on an extension of the WATS model in terms of hydrogen sulfide emission. A fundamental concept of this extended model is related to emission of the molecular form of hydrogen sulfide and thereby to pH of wastewater. An engineering application of the extended WATS model includes different scenarios of sewer performance concerning hydrogen sulfide emission under dissolved oxygen-limited conditions. By applying the extended WATS model, users can more realistically cope with the fate of hydrogen sulfide. Consequently, when dealing with the sulfur cycle, users need no longer be restricted to the sulfide formation process but can also take transfer of hydrogen sulfide across the air-water interface into account.

Bacteria, Aerobic↗