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PubMed2006

Local intrahepatic CD8+ T cell activation by a non-self-antigen results in full functional differentiation.

The response of T cells to liver Ags sometimes results in immune tolerance. This has been proposed to result from local, intrahepatic priming, while the expression of the same Ag in liver-draining lymph nodes is believed to result in effective immunity. We tested this model, using an exogenous model Ag expressed only in hepatocytes, due to infection with an adeno-associated virus vector. T cell activation was exclusively intrahepatic, yet in contrast to the predictions of the current model, this resulted in clonal expansion, IFN-gamma synthesis, and cytotoxic effector function. Local activation of naive CD8(+) T cells can therefore cause full CD8(+) T cell activation, and hepatocellular presentation cannot be used to explain the failure of CTL effector function against some liver pathogens such as hepatitis C.

Adoptive Transfer↗
PubMed2002

Application of information theory and extreme physical information to carcinogenesis.

Cellular information dynamics during somatic evolution of the malignant phenotypes are complex and poorly understood. Accumulating, random genetic mutations and, therefore, loss of genomic information appears necessary for carcinogenesis. However, additional control parameters can be inferred because unconstrained mutagenesis would ultimately produce cellular information degradation incompatible with life. Similarly, the stability of some genomic segments, such as those controlling proliferation and metabolism, indicates the presence of selective mutational constraints. By applying Information Theory and Extreme Physical Information (EPI) analysis, we demonstrate that the phenotypic characteristics and growth pattern of cancer populations are emergent properties resulting from the nonlinear dynamics of accumulating, random genetic mutations and tissue selection factors. Maximum quantitative loss of transgenerational information is demonstrated in genomic segments encoding negative or neutral evolutionary properties. This is most evident in the progressive dedifferentiation observed during carcinogenesis and may terminate in a differentiation "information catastrophe" producing decoherent cellular morphology and function. In contrast, microenvironmental selection pressures preserve genomic information controlling properties that confer selective growth advantages even in the presence of a high background mutation rate. Thus, phenotypic traits characteristically retained by tumor populations can be identified as critical selection parameters favoring clonal proliferation. The information model of carcinogenesis is tested by applying EPI analysis to predict tumor growth dynamics. We found that cellular proliferation attributable to information degradation will produce power law tumor growth with an exponent of 1.62. Data from six published studies that use sequential mammograms to measure the volume of small, untreated human breast cancers demonstrate power law tumor growth with a mean exponent value of 1.73 +/- 0.23. Other predictions including exponential growth of tumor cells in vitro are also supported by experimental observations. The nonlinear dynamics of stochastic information loss constrained by somatic evolution indicate that carcinogenesis will not be associated with any predictable, fixed sequence of genomic alterations. Rather, sporadic clinical cancers are emergent structures produced by multiple, fundamentally nondeterministic genetic pathways.

Animals↗
PubMed2003

In-depth analysis of molecular alterations within normal and tumour tissue from an entire bronchial tree.

Using laser capture microdissection (LCM), fluorescent microsatellite analysis and immunohistochemical analysis, we have constructed a detailed topographical molecular map of the entire bronchial tree surrounding a primary bronchial squamous carcinoma in order to establish the relationship between the molecular damage within the airway and that in the tumour itself. Allelic imbalance was analysed using markers on chromosomes 3, 9, 13 and 17. In addition, immunohistochemical analysis for p53 and cyclin D1 expression was performed. Analysis revealed allelic imbalance at several loci at the tumour site but also in 83% of the histologically normal airway specimens of the upper and lower lobes. The fractional allele loss (FAL) value was statistically higher (0.75+/-0.13) in the tumour site than in the distal site of the upper (0.42+/-0.09) and lower lobes (0.31+/-0.08). Immunohistochemical analysis revealed overexpression of p53 and cyclin D1 protein within histologically normal bronchial epithelium, thus confirming previous reports for their early involvement in lung tumour development. This is to date the largest in-depth study of allelic imbalance using LCM in a single individual. The patterns of allele-specific imbalance observed support a clonal or oligoclonal expansion model of outgrowths throughout the lung. The widespread incidence of genetic changes in the whole of lung most likely represents smoking-induced alterations and emphasize the complexity of the field cancerization concept. Our findings point to the need for in-depth studies of the whole bronchial tree tissue surrounding lung carcinomas, in order to identify the genetic changes that differentiate preneoplastic and neoplastic stages in lung carcinogenesis.

Aged↗
PubMed1990

Transformation of rabbit vascular smooth muscle cells by transfection with the early region of SV40 DNA.

Rabbit aortic smooth muscle cells (SMC) and Rb-1 cells, a continuous line of the same origin, were transformed by transfection with pSV3-neo DNA, a plasmid containing the SV40 early region linked to the neoR resistance gene. Transformed clones were selected in G418-containing medium at a rate of 10(-4) per cell. All transformed clones were immortalized and contained in the early passages two free recombined plasmids derived from pSV3-neo. At advanced passages pSV3-neo sequences were found integrated in the cellular genome. Transformed cells had an altered morphology and growth pattern that differed among clones. Some clones reached high density in low-serum medium. All the clones stained positively for the intranuclear T antigen. Some clones had distinct transcripts for the large T and small t antigens, while in others only larger or truncated transcripts were found. Alpha-actin filaments were visualized by immunofluorescent staining in all the clones, but Northern blot analysis revealed a significant reduction in transcripts for this actin. All the transformed clones accumulated, to a variable extent, cholesteryl esters after incubation with beta very low-density lipoprotein. Six of the eight transformed clones maintained a diploid chromosome number, but there was an increase in structural chromosome aberrations, predominantly dicentrics. Transfection of pSV3-neo into rabbit vascular SMCs is an efficient model for obtaining transformed clonal populations. These clones show some phenotypic changes that may be relevant to the study of atherogenesis.

Actins↗
PubMedDate not supplied

[Ontogeny-derived hematopoietic stem cells divide successively producing clones of differentiated hematopoietic cells].

Forty seven individual haemopoietic cell clones bearing unique radiation markers were studied in long-term bone marrow cultures. Throughout cultivation, clones appeared at different times, 1 to 12 weeks after explanation, survived during 1-10 weeks and markedly varied in size. Usually, the number of metaphases characteristic of an individual clone rapidly increased, achieved a maximum and declined. The cells of disappeared clones were never seen again. The experimental results provide further evidence for the model of haemopoiesis by clonal succession. The data obtained are discussed with respect to the functioning of haemopoietic stem cell population.

Animals↗
PubMed1987

Individual clones of hemopoietic cells in murine long-term bone marrow culture.

Forty-seven individual hemopoietic cell clones bearing unique radiation markers were studied in long-term bone marrow cultures. Throughout cultivation clones appeared at different times, from 1 to 12 weeks after explantation, survived during 1-10 more weeks, and were characterized by marked variability in size. Usually, the number of metaphases peculiar to an individual clone rapidly increased, achieved maximum, and then underwent a decline. Cells of reliably disappearing clones were never seen again. The experimental results provide further evidence for the model of hemopoiesis by clonal succession.

Animals↗
PubMed1997

Sjögren's syndrome. Controversies and progress.

Diagnostic criteria for Sjögren's syndrome (SS) are required by both physicians and patients to (1) provide a rational basis for their symptoms, assess their prognosis, and guide therapy; (2) identify a group of patients who are most likely to share a common etiopathogenesis, in order to identify those genetic and environmental factors that are crucial in pathogenesis; (3) fill out the myriad medical insurance forms that require a diagnosis code; and (4) serve as a "shorthand" code that alerts specialists in different fields (oral medicine, ophthalmology, and a variety of specialists in internal medicine) to search for particular clinical problems found in the SS patient. The key question in this article is whether the term "Sjögren's syndrome" should apply to a rather restricted group of individuals (those with an autoimmune basis for exocrinopathy) or to a rather large group of individuals who share a similar symptom complex of dry eyes and mouth. Primary SS, as defined by San Diego criteria, is a systemic autoimmune disease that is characterized by keratoconjunctivitis sicca and xerostomia resulting from lymphocytic infiltrates of the lacrimal and salivary glands. The criteria for the diagnosis of SS continues to be controversial, leading to confusion in the clinical and research literature. It is important to distinguish SS (an idiopathic autoimmune process) from other processes including hepatitis C infection, retroviral infection, lymphoma, autonomic neuropathy, depression, primary fibromyalgia, and drug side effects that can result in sicca symptoms. Recent studies on pathogenesis of SS in human and animal models have examined the clonality of the T-cell infiltrates, the production of cytokines by lymphocytes and glandular epithelial cells, neuroendocrine and hormonal factors that affect glandular secretion, and the fine structure of antigens recognized by T cells and B cells. Studies in SS have allowed comparison of lymphocytes in blood and in the glandular tissue lesions; important differences in the gland microenvironment play an important role in the initiation and perpetuation of the autoimmune process. For example, apoptotic death depends on the balance of Fas, Fas ligand, nuclear factors (such as bcl-2, bax, and myc), cytokines, neuropeptides, and cell membrane interactions with extracellular matrix. Although increased rates of apoptosis may be present in the blood T cells of SS patients, some glandular T cells are resistant to apoptosis. Recent advances have led to improved understanding of signal transduction in response to cytokines and hormones that play a role in the local and systemic manifestations of SS.

Animals↗
PubMed1996

Improved models for pharmacological null experiments: calculation of drug efficacy at recombinant D1A dopamine receptors stably expressed in clonal cell lines.

Modern drug discovery demands accurate knowledge of the drug properties of affinity and efficacy at specific receptor proteins. Furthermore, drugs with well defined properties make better tools with which to explore and understand receptor regulation. The use of clonal cell lines stably expressing a given recombinant receptor may provide a highly useful model in which drug effects may be studied on one receptor subtype at a time. The present report was designed to evaluate the utility of a general method in which a clonal cell line stably expressing a recombinant D1A dopamine receptor was used as a model system for studying drug actions by null models. The null model for receptor occlusion (to calculate agonist Ka) and the null model for relative efficacy (to calculate test agonist affinity and epsilon r) were evaluated in these studies. To initiate these studies, rat C6 glioma cells that do not normally express DA receptors have been modified by stable transfection with the primate D1A DA receptor [Machida et al., 1992 (Molec. Pharmacol. 41: 652-659)] to a density of approximately equal to fmol/mg protein. The recombinant receptors show robust stimulation of cAMP in the stably transfected C6 cells. Calculation of agonist Ka from dose-response data requires that a portion of the cell's receptors be occluded in the absence of changes in post-receptor events leading to the response. Receptor reserve is typically reduced by alkylation, thereby lowering maximal response. Unfortunately, most of the currently available alkylating agents are not selective either for a particular receptor or for receptors vs other proteins within a signaling pathway. Short-term agonist treatment offers a possible complement to the use of non-selective or poorly characterized alkylating drugs for reducing maximum response in appropriate cell systems. The null method of receptor occlusion was used to determine the Ka for dopamine when maximum response was decreased by alkylation vs short-term agonist treatment. Direct non-linear curve fitting was used to analyze the data. In addition to DA, two other compounds were used to reduce receptor reserve to validate the method: fenoldopam (relatively high efficacy) and SKF38393 (low efficacy). Analyses indicated that the affinity of DA was similar whether calculated by alkylation (1.1 +/- 0.58 microM), 75 min DA treatment (0.57 +/- 0.16 microM) or 45 min treatment with DA (0.86 +/- 0.11 microM). Short-term agonist treatment experiments using multiple concentrations of DA, fenoldopam, or SKF38393 to decrease receptor reserve provided additional support for the validity of the Ka determinations using this procedure. Other experiments were conducted according to the null model for relative efficacy in which the affinity for DA is calculated by comparing the DA response before and after receptor occlusion, and the affinity and relative intrinsic efficacy of the test agonist are determined as a function of its actions relative to DA. We used the following four test drugs: + Br-APB, a novel agent with potential dopamine agonist properties, and three high-affinity DA agonists, fenoldopam, R-(-)-apomorphine (APO), and SKF38393. Intrinsic efficacy values relative to that of DA (1.0) were as follows: fenoldopam, 0.46 +/- 0.11; APO, 0.19 +/- 0.13; SKF38393, 0.07 +/- 0.01; and +Br-APB, 0.26 +/- 0.40. The agonist affinities (Ka) were: fenoldopam, 0.018 +/- 0.008 microM; APO, 0.80 +/- 0.18 microM; SKF38393, 0.16 +/- 0.04 microM; BR-APB, 0.43 +/- 0.29 microM; and DA, 0.58 +/- 0.17 microM. EC50/Ka ratios were consistent with relative intrinsic efficacies and Ka values were similar to KL values reported for membrane binding studies. Finally, Monte Carlo simulations were conducted to determine the precision of the parameter estimates...

Animals↗
PubMed2002

Cyclic dynamics in simulated plant populations.

Despite the general interest in nonlinear dynamics in animal populations, plant populations are supposed to show a stable equilibrium that is attributed to fundamental differences compared with animals. Some studies find more complex dynamics, but empirical studies usually are too short and most modelling studies ignore important spatial aspects of local competition and establishment. Therefore, we used a spatially explicit individual-based model of a hypothetical, non-clonal perennial to explore which mechanisms might generate complex dynamics, i.e. cycles. The model is based on the field-of-neighbourhood approach that describes local competition and establishment in a phenomenological manner. We found cyclic population dynamics for a wide spectrum of model variants, provided that mortality is determined by local competition and recruitment is virtually completely suppressed within the zone of influence of established plants. This destabilizing effect of local processes within plant populations might have wide-ranging implications for the understanding of plant community dynamics and coexistence.

Ecosystem↗
PubMed2005

Ah receptor- and TCDD-mediated liver tumor promotion: clonal selection and expansion of cells evading growth arrest and apoptosis.

The Ah receptor (AhR) has been characterized as a ligand-activated transcription factor which belongs to the bHLH/PAS (basic helix-loop-helix/Per-Arnt-Sim) family of chemosensors. Transgenic mouse models revealed adaptive and developmental functions of the AhR in the absence of exogenous ligands. Use of persistent agonists such as dioxins including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds demonstrated that the AhR mediates a plethora of species- and tissue-dependent toxicities, including chloracne, wasting, teratogenicity, immunotoxicity, liver tumor promotion and carcinogenicity. However, molecular mechanisms underlying most aspects of these toxic responses as well as biological functions of the AhR are currently unknown. Previous studies of liver tumor promotion in the two-stage hepatocarcinogenesis model indicated that TCDD mediates clonal expansion of 'initiated' preneoplastic hepatocytes, identified as enzyme-altered foci (EAF) by inhibiting apoptosis and bypassing AhR-mediated growth arrest. In contrast, the Ah receptor has been shown in cell models to stimulate growth arrest and apoptosis. Possible underlying mechanisms of these AhR responses are discussed, including enhanced metabolism of retinoic acid which attenuates TGFbeta-mediated apoptosis and interaction of the Ah receptor with the hypophosphorylated retinoblastoma tumor suppressor protein. The discrepancy between in vivo findings in EAF and AhR functions may be solved by hypothesizing that sustained activation of the Ah receptor generates a strong selective pressure in liver treated with genotoxic carcinogens leading to selection and expansion of clones evading growth arrest and apoptosis. Models are discussed which may facilitate verification of this hypothesis.

Animals↗
PubMed1992

Distinct proliferative and differentiated stages of murine MC3T3-E1 cells in culture: an in vitro model of osteoblast development.

We examine clonal murine calvarial MC3T3-E1 cells to determine if they exhibit a developmental sequence similar to osteoblasts in bone tissue, namely, proliferation of undifferentiated osteoblast precursors followed by postmitotic expression of differentiated osteoblast phenotype. During the initial phase of developmental (days 1-9 of culture), MC3T3-E1 cells actively replicate, as evidenced by the high rates of DNA synthesis and progressive increase in cell number, but maintain a fusiform appearance, fail to express alkaline phosphatase, and do not accumulate mineralized extracellular collagenous matrix, consistent with immature osteoblasts. By day 9 the cultures display cuboidal morphology, attain confluence, and undergo growth arrest. Downregulation of replication is associated with expression of osteoblast functions, including production of alkaline phosphatase, processing of procollagens to collagens, and incremental deposition of a collagenous extracellular matrix. Mineralization of extracellular matrix, which begins approximately 16 days after culture, marks the final phase of osteoblast phenotypic development. Expression of alkaline phosphatase and mineralization is time but not density dependent. Type I collagen synthesis and collagen accumulation are uncoupled in the developing osteoblast. Although collagen synthesis and message expression peaks at day 3 in immature cells, extracellular matrix accumulation is minimal. Instead, matrix accumulates maximally after 7 days of culture as collagen biosynthesis is diminishing. Thus, extracellular matrix formation is a function of mature osteoblasts. Ascorbate and beta-glycerol phosphate are both essential for the expression of osteoblast phenotype as assessed by alkaline phosphatase and mineralization of extracellular matrix. Ascorbate does not stimulate type I collagen gene expression in MC3T3-E1 cells, but it is absolutely required for deposition of collagen in the extracellular matrix. Ascorbate also induces alkaline phosphatase activity in mature cells but not in immature cells. beta-glycerol phosphate displays synergistic actions with ascorbate to further stimulate collagen accumulation and alkaline phosphatase activity in postmitotic, differentiated osteoblast-like cells. Mineralization of mature cultures requires the presence of beta-glycerol phosphate. Thus, MC3T3-E1 cells display a time-dependent and sequential expression of osteoblast characteristics analogous to in vivo bone formation. The developmental sequence associated with MC3T3-E1 differentiation should provide a useful model to study the signals that mediate the switch between proliferation and differentiation in bone cells, as well as provide a renewable culture system to examine the molecular mechanism of osteoblast maturation and the formation of bone-like extracellular matrix.

Alkaline Phosphatase↗
PubMedDate not supplied

Inhaled formaldehyde: exposure estimation, hazard characterization, and exposure-response analysis.

Formaldehyde has been assessed as a Priority Substance under the Canadian Environmental Protection Act. Probabilistic estimates of exposure of the general population in Canada to formaldehyde in ambient and indoor air are presented. Critical health effects include sensory irritation and the potential to induce tumors in the upper respiratory tract (the nasal region in rodents and potentially the lungs of humans). The majority of the general population is exposed to airborne concentrations of formaldehyde less than those typically associated with sensory irritation (i.e., 0.1 mg/m3). Based primarily upon data derived from laboratory studies, the inhalation of formaldehyde under conditions that induce cytotoxicity and sustained regenerative proliferation within the respiratory tract is considered to present a carcinogenic hazard to humans. At airborne levels for which the prevalence of sensory irritation is minimal (i.e., 0.1 mg/m3), risks of respiratory-tract cancers for the general population estimated on the basis of a biologically motivated case-specific model are exceedingly low. This biologically motivated case-specific model incorporates two-stage clonal expansion and is supported by dosimetry calculations from computational fluid dynamics analyses of formaldehyde flux in various regions of the nose and single-path modeling for the lower respiratory tract. The degree of confidence in the underlying database and uncertainties in estimates of exposure and in characterization of hazard and dose response are delineated.

Air Pollutants↗
PubMed1993

The fate of genetically marked human oral keratinocytes in vitro.

The fate of the progeny of human oral gingival keratinocytes was mapped in stratified epithelial tissues in vitro by following the expression of a marker gene in genetically related clones. Oral epithelial progenitor cells were genetically marked at high efficiency by transducing them with a retrovirus vector that carried the gene for a histochemically detectable product, Escherichia coli beta-galactosidase (beta-gal). These cells were then grown in submerged cultures and on collagen rafts at the air-liquid interface to demonstrate the distribution of genetically marked cells in a differentiating tissue in vitro. The dynamics of transduced cells showed that clonally related cells were arranged in discrete units of labelled cells and these clusters were defined as 'clonal proliferation units'. The size and configuration of these units were related to the proliferative potential and differentiating capacity of the cell that was initially transduced. This model demonstrates the relation between clonally related cells and tissue architecture for oral keratinocytes in vitro.

Cell Differentiation↗
PubMed1996

Human T-and B-cell functions in SCID-hu mice.

SCID mice transplanted with human fetal liver and thymus (SCID-hu Thy/Liv) provide a unique in-vivo model to study human T-cell development and clonal selection mechanisms. This SCID-hu mouse model can be adapted to study the role of thymic epithelial cells, or bone marrow-derived cells in transplantation tolerance. In addition, these mice have circulating human T cells, which mediate human allograft rejection in vivo. SCID-hu mice constructed with fetal bones and thymus (SCID-hu BM/Thy) have both circulating human T and B cells, and can be used to study human B-cell development and B-cell functions. In addition, human T-B-cell interactions resulting in human lg production and the modulating effects of cytokines and cytokine receptor antagonists on this process, can be monitored. Collectively, this information indicates that the SCID-hu mouse is a powerful and versatile model to study human immune responses in vivo.

Animals↗
PubMed2006

A model for the induction of chromosome aberrations through direct and bystander mechanisms.

A state vector model (SVM) for chromosome aberrations and neoplastic transformation has been adapted to describe detrimental bystander effects. The model describes initiation (formation of translocations) and promotion (clonal expansion and loss of contact inhibition of initiated cells). Additional terms either in the initiation model or in the rate of clonal expansion of initiated cells, describe detrimental bystander effects for chromosome aberrations as reported in the scientific literature. In the present study, the SVM with bystander effects is tested on a suitable dataset. In addition to the simulation of non-linear effects, a classical dataset for neoplastic transformation in C3H 10T1/2 cells after alpha particle irradiation is used to show that the model without bystander features can also describe LNT-like dose responses. A published model for bystander induced neoplastic transformation was adapted for chromosome aberration induction and used to compare the results obtained with the different models.

Animals↗
PubMed1989

Gastric small lymphocytic proliferation with immunoglobulin gene rearrangement in pseudolymphoma versus lymphoma.

The nature of gastric infiltrates consisting primarily of benign-appearing small lymphocytes is at present a controversial issue. Earlier reports of gastric lymphoma developing in gastric pseudolymphoma and more recent immunohistochemical studies demonstrating monoclonal B-cell populations in pseudolymphoma suggest that at least some cases represent low-grade lymphomas or clonal precursor lesions that may develop into lymphoma. Observations of a small lymphocytic infiltrate arising in the region of a gastric ulcer that lacked definitive morphologic evidence of malignancy (lymphoma) but was clearly a monoclonal B-cell proliferation by immunohistochemical and gene rearrangement studies support the notion that some gastric lymphoproliferative lesions that histologically have been called pseudolymphomas may include one or more clonal lymphoid expansions. A histopathologic/molecular model suggesting a potential pathway for the development of morphologically recognizable lymphoma from benign-appearing small lymphocytic infiltrates is presented, and the concept that for a variety of lymphoid proliferations clonality and malignancy may not be synonymous is discussed.

Aged↗
PubMed1980

Mathematical models of antibody response.

An antigen triggers the clonal expansion of B lymphocytes accompanied by antibody production. This paper presents and compares the basic ideas of three mathematical models of B cell differentiation and proliferation.

Antibody Formation↗