Management of growth failure and growth hormone deficiency after pediatric allogeneic HSCT: Endocrinologists are of importance for further guidelines and studies.

Growth failure (GF) is a frequent problem after pediatric allogeneic hematopoietic stem cell transplantation (HSCT). Growth hormone deficiency (GHD) occurs in 20 to 85%, but published data on the efficacy of growth hormone treatment (GHT) are conflicting. Currently, there are no recommendations on screening for and treatment of GHD after HSCT. We aimed to describe the management of endocrine follow-up (FU)and details of GHT within European Society for Blood and Marrow Transplantation (EBMT) centers.In a retrospective questionnaire study, all EBMT centers performing pediatric HSCT were invited. Results were evaluated in correlation with the structure of endocrine aftercare (HSCT-clinicians and endocrinologists).The majority of centers (80%) reported endocrine FU by an endocrinologist - either within the HSCT-center or in a separate endocrine clinic. Fifty-four percent reported FU outside of the HSCT-center. As diagnostic tests the insulin-like growth factor IGF-I and insulin-like growth factor binding protein IGFBP3, insulin tolerance test and arginine stimulation test were most frequently used. Sixty-four percent of centers performed GHT and endocrinologists were more likely to prescribe GH (74%) compared to HSCT-clinicians (33%). The most frequent indication for GHT was GHD in 60%, with a distinct different approach of endocrinologists in comparison with HSCT-clinicians.Our study reveals substantial variation in practice and emphasizes the need for endocrine aftercare performed by dedicated endocrinologists in close collaboration with the HSCT-center. Our results indicate that the management of GHT depends on the structure of endocrine aftercare, which is important for the future development and distribution of studies and guidelines.

Characterization and pro-inflammatory responses of spore and hyphae samples from various mold species.

Mold particles from Aspergillus fumigatus, Penicillium chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum have been linked to respiratory-related diseases. We characterized X-ray-inactivated spores and hyphae fragments from these species by number of particles, morphology, and mycotoxin, ß-glucan and protease content/activity. The pro-inflammatory properties of mold particles were examined in human bronchial epithelial cells (BEAS-2B) and THP-1 monocytes and phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1. Spores from P. chrysogenum and S. chartarum contained some hyphae fragments, whereas the other preparations contained either spores or hyphae. Each mold species produced mainly one gelatin-degrading protease that was either of the metallo- or serine type, while one remains unclassified. Mycotoxin levels were generally low. Detectable levels of ß-glucans were found mainly in hyphae particle preparations. PMA-differentiated THP-1 macrophages were by far the most sensitive model with effects in the order of 10 ng/cm2 . Hyphae preparations of A. fumigatus and P. chrysogenum were more potent than respective spore preparations, whereas the opposite seems to be true for A. versicolor and S. chartarum. Hyphae fragments of A. fumigatus, P. chrysogenum, and A. versicolor enhanced the release of metalloprotease (proMMP-9) most markedly. In conclusion, species, growth stage, and characteristics are all important factors for pro-inflammatory potential.

TACE/TGF-α/EGFR regulates CXCL8 in bronchial epithelial cells exposed to particulate matter components.

Airborne particulate matter (PM) may induce or exacerbate neutrophilic airway disease by triggering the release of inflammatory mediators, such as CXC chemokine ligand (CXCL)8, from the airway epithelium. It is still unclear which PM components are driving CXCL8 responses, as most candidates occur at low concentrations in the dusts. We therefore hypothesised that different PM constituents may contribute through common mechanisms to induce CXCL8. Human bronchial epithelial cells (BEAS-2B) were exposed to different PM components (Zn²âº/Fe²âº salts, 1-nitropyrene, lipopolysaccharide and diesel exhaust/mineral particles). Gene expression patterns were detected by real-time PCR array. CXCL8 responses were measured by real-time PCR and ELISA. CXCL8 regulation was assessed with a broad inhibitor panel and neutralising antibodies. Epidermal growth factor receptor (EGFR) phosphorylation was examined by immunoprecipitation and Western blotting. Component-induced gene expression was mainly linked to nuclear factor-κB, Ca²âº/protein kinase C, phospholipase C, low-density lipoprotein and mitogenic signalling. Many inhibitors attenuated CXCL8 release induced by all PM components, but to varying extents. However, EGFR inhibition strongly reduced CXCL8 release induced by all test compounds and selected compounds increased EGFR phosphorylation. Interference with transforming growth factor (TGF)-α or tumour necrosis factor-α-converting enzyme (TACE), which mediates TGF-α ectodomain shedding, also attenuated CXCL8 release. Different PM constituents induced CXCL8 partly through similar signalling pathways but the relative importance of the different pathways varied. However, TACE/TGF-α/EGFR signalling appears to be a convergent pathway regulating innate immune responses of airway epithelial cells upon exposure to multiple airborne pollutants.

Low levels of antibodies for the oral bacterium Tannerella forsythia predict cardiovascular disease mortality in men with myocardial infarction: A prospective cohort study.

Antibody levels to periodontal pathogens in prediction of cardiovascular disease (CVD) mortality were explored using data from a health survey in Oslo in 2000 (Oslo II-study) with 12 1/2 years follow-up. IgG antibodies to four common periodontal pathogens; Tannerella forsythia (TF), Porphyromonas gingivalis (PG), and Treponema denticola (TD) all termed collectively the "red complex", and Aggregatibacter actinomycetemcomitans(AA) were analysed. The study sample consisted of 1172 men drawn from a cohort of 6,530 men who participated in the Oslo II-study, where they provided information on medical and dental history. Of the study sample, 548 men had reported prior myocardial infarction (MI) at baseline whereas the remaining 624 men were randomly drawn from the ostensibly healthy participants for comparative analyses. Dental anamnestic information included tooth extractions and oral infections. An inverse relation was found for trend by the quartile risk level of TF predicting CVD mortality, p-value for trend = 0.017. Comparison of the first to fourth quartile of TF antibodies resulted in hazard ratio (HR) = 1.82, 95% confidence interval 1.12-2.94, p = 0.015, adjusted for age, education, diabetes, daily smoking, and systolic blood pressure. Specificity comparing decile 1 to deciles 2-10 of TF predicting mortality was 92.3%. We found an increased HR by low levels of antibodies to the bacterium T. forsythia predicting CVD mortality in a 12 ½ years follow-up in persons who had experienced an MI but not among non-MI men. This novel finding constitutes a plausible causal link between oral infections and CVD mortality.

Cytokine and chemokine expression patterns in lung epithelial cells exposed to components characteristic of particulate air pollution.

Airborne particulate matter (PM) has a complex composition, and the relative contribution of different compounds to PM-induced effects is only partly understood. The present study compared the capability of selected components commonly found in PM, to induce pro-inflammatory responses in lung epithelial cells. Ultrafine carbon black (ufCB), ZnCl(2), FeSO(4), 1-nitropyrene (1-NP), lipopolysaccharide (LPS), and crystalline silica (positive control) were screened for effects on the expression of 84 inflammation-related genes in the bronchial epithelial cell line, BEAS-2B. A total of 22 genes were up-regulated by one or more of the tested compounds, and 5 cytokine and 11 chemokine genes were selected for further studies. After 10h exposure, silica induced significantly increased expression of CCL20, CXCL1/-3/-8/-10/-11, lymphotoxin (LT)beta and interleukin (IL)-6; ufCB induced CXCL8/-10 and -11; ZnCl(2) induced CCL11/-20/-26, CXCL1/-5/-8/-14 and tumor necrosis factor (TNF)-alpha; FeSO(4) induced a weak up-regulation of CXCL8 and TNF-alpha; LPS induced CCL20, CXCL1/-5/-8/-10/-11, LTbeta and IL-6; and 1-NP induced expression of CCL20, CXCL1/-3/-8, TNF-alpha and IL-6. Despite obvious differences, all compounds induced response-patterns that correlated relatively well with that of silica, the positive control. The predominant response appeared to be increased gene expression of neutrophil-recruiting CXC-chemokines. CXCL8 was the only gene induced by all tested PM-components, the most up-regulated on average, and also dominating the gene-expression patterns induced by coarse PM. The data show quantitative, and to a certain extent qualitative differences in cytokine/chemokine gene-expression profiles of the compounds tested. However, there were also striking similarities in the response-patterns induced by these physically/chemically widely different compounds.

Differential binding of cytokines to environmentally relevant particles: a possible source for misinterpretation of in vitro results?

Inflammation is considered as a key event in adverse health effects associated with exposure to ambient particulate matter. The inflammatory potential of particles is often compared using in vitro cell systems, where the particle-induced release of pro-inflammatory cytokines is measured. A major concern in these assays is the potential of particles to bind cytokines, which may lead to an underestimation of the inflammatory potential. We therefore investigated the cytokine binding to a selection of particle samples, including particles collected from outdoor sources (wood combustion, traffic) and particles commonly used to model environmental sources (ultrafine carbon black, diesel, quartz), for a range of pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6, IL-8). Furthermore, the influence of serum proteins and particle- and cytokine concentrations on the cytokine binding was studied. Cytokines primarily bound to carbonaceous particles (up to 85%), not to mineral particles. Furthermore, depending on the type of cytokine, the cytokine binding could be reduced partly or completely by adding serum proteins to the cell growth medium or particle suspensions. Based on these observations we recommend either to adjust culturing and exposure conditions to prevent cytokine binding, or to adjust the measured cytokine release by application of correction factors obtained from cytokine binding experiments.

Importance of size and composition of particles for effects on cells in vitro.

A primary goal of current research on particle-induced health effects is to reveal the critical characteristics that determine their biological effects. Experimental studies have shown that smaller particles induce stronger biological effects than larger particles of similar composition, due to their larger surface area to mass ratio. However, correlation for variations in surface area could not account for variation in biological reactivity among particles of differential composition. Hence, the importance of size and surface area does not override the importance of particle composition. Moreover, different particle characteristics appear to be involved in different biological effects in vitro. Our studies show that mineral particle-induced apoptosis mostly seems to depend on particle size, whereas composition and surface reactivity appeared to be most important for the proinflammatory potential of the particles. The ability of the particles to generate reactive oxygen species in vitro was not correlated with either inflammatory markers or apoptosis, suggesting that other mechanisms are at play. A single, specific component of the mineral particles, explaining the differences in response, has not been identified. In European-wide studies such as the Respiratory Allergy and Inflammation due to Air Pollution (RAIAP) study, particles have been sampled in different locations to study season- and site-dependent variations in responses particles, such as markers of inflammatory and allergic reactions in cells and animals. The data indicate that coarse particles can induce at least as strong inflammatory responses as fine particles. The allergic responses tended to be more associated with the organic fraction (PAH) of particles, whereas the inflammatory reactions seemed to be more associated with metals and endotoxin. Overall, coarse PM was found to have an inflammatory potential similar to fine PM on an equal mass basis. Even though one has to take into account different concentrations in ambient air as well as differences in respiratory system deposition of the size fractions, the potential of coarse particles to induce pulmonary effects should not be neglected.

Iron release and ROS generation from mineral particles are not related to cytokine release or apoptosis in exposed A549 cells.

The generation of reactive oxygen species (ROS) by mineral particles is believed to be central to their toxicity and their ability to induce inflammation. Surface bound or soluble iron may contribute to the particle-effects by enhancing the ROS generation through the Fenton reaction. Nevertheless, the importance of ROS and transition metals to mineral particle-induced effects is still unclear and further investigations are needed. In the present study we have investigated different mineral particles for their total iron content, amount of soluble iron at pH 7.0 and 4.0, their ability to generate ROS in a cell-free environment, and their ability to induce cytokine release and apoptosis in a human alveolar epithelial cell line (A549). All the investigated parameters varied considerably between the different particles, with the exception of ability to induce apoptosis. Total iron content did not reflect the amount of soluble iron, and neither total nor soluble iron was correlated with ROS generation. Moreover, iron content and ROS was not correlated with the ability of particles to induce cytokine release or apoptosis. The present results suggest that there is no clear relationship between the particles iron content and ability to generate ROS. Moreover, neither iron content nor the ability to induce ROS generation appears to be a prerequisite for the inflammatory potential or cytotoxicity of mineral particles.

Changes in ploidy distributions in human liver carcinogenesis.

Cellular and nuclear DNA content was measured by flow cytometry and the fraction of binucleated cells by fluorescence microscopy in normal adult human livers, hepatocellular carcinomas, cirrhotic livers surrounding tumors, and in some benign liver conditions. In five normal livers about one-half of the hepatocytes were polyploid; the majority of these were binucleated tetraploids containing two diploid nuclei. Thus, polyploidization in human liver does not progress as far as, for example, in the rat, where 80%-90% of adult hepatocytes are polyploid, mostly with tetraploid or octoploid nuclei. In five human euploid hepatocellular carcinomas and one investigated case of focal nodular hyperplasia, the percentage of polyploid cells was significantly reduced. Four other carcinomas exhibited a prominent aneuploid (hypotetraploid) peak in addition to the diploid peak. An abnormally low fraction of binucleated cells was also indicated in these tumors. Liver tissue surrounding the tumors had a ploidy distribution similar to that of normal liver. The results suggest that, like in several models of experimental hepatocarcinogenesis, human hepatocellular tumor growth is associated with a decreased polyploidization tendency and a corresponding increase in diploid, divisional growth, which may give the tumors a growth advantage relative to the surrounding liver.

Particulate matter properties and health effects: consistency of epidemiological and toxicological studies.

Identifying the ambient particulate matter (PM) fractions or constituents, critically involved in eliciting adverse health effects, is crucial to the implementation of more cost-efficient abatement strategies to improve air quality. This review focuses on the importance of different particle properties for PM-induced effects, and whether there is consistency in the results from epidemiological and experimental studies. An evident problem for such comparisons is that epidemiological and experimental data on the effects of specific components of ambient PM are limited. Despite this, some conclusions can be drawn. With respect to the importance of the PM size-fractions, experimental and epidemiological studies are somewhat conflicting, but there seems to be a certain consistency in that the coarse fraction (PM10-2.5) has an effect that should not be neglected. Better exposure characterization may improve the consistency between the results from experimental and epidemiological studies, in particular for ultrafine particles. Experimental data indicate that surface area is an important metric, but composition may play an even greater role in eliciting effects. The consistency between epidemiological and experimental findings for specific PM-components appears most convincing for metals, which seem to be important for the development of both pulmonary and cardiovascular disease. Metals may also be involved in PM-induced allergic sensitization, but the epidemiological evidence for this is scarce. Soluble organic compounds appear to be implicated in PM-induced allergy and cancer, but the data from epidemiological studies are insufficient for any conclusions. The present review suggests that there may be a need for improvements in research designs. In particular, there is a need for better exposure assessments in epidemiological investigations, whereas experimental data would benefit from an improved comparability of studies. Combined experimental and epidemiological investigations may also help answer some of the unresolved issues.

Isolation of carcinogen-induced diploid rat hepatocytes by centrifugal elutriation.

The majority of hepatocytes isolated from rats treated with carcinogens (diethylnitrosamine plus 2-acetylaminofluorene) were found to be diploid, whereas most of the hepatocytes from normal rats are tetraploid. The carcinogen-induced diploid hepatocytes were only one-half the size (protein content) of the tetraploid hepatocytes, and could therefore be separated from the latter by centrifugal elutriation. The elutriation technique thus makes it possible to isolate a relatively pure fraction of carcinogen-induced cells. The diploid cells had the same liver-specific enzymatic and functional properties as the tetraploid cells and were thus undoubtedly of hepatocytic origin.

Air pollution-related metals induce differential cytokine responses in bronchial epithelial cells.

Different transition metals have been shown to induce inflammatory responses in lung. We have compared eight different metal ions with regard to cytokine responses, cytotoxicity and signalling mechanisms in a human lung epithelial cell model (BEAS-2B). Among the metal ions tested, there were large differences with respect to pro-inflammatory potential. Exposure to Cd(2+), Zn(2+) and As(3+) induced CXCL8 and IL-6 release at concentrations below 100µM, and Mn(2+) and Ni(2+) at concentrations above 200µM. In contrast, VO4(3-), Cu(2+) and Fe(2+) did not induce any significant increase of these cytokines. An expression array of 20 inflammatory relevant genes also showed a marked up-regulation of CXCL10, IL-10, IL-13 and CSF2 by one or more of the metal ions. The most potent metals, Cd(2+), Zn(2+) and As(3+) induced highest levels of oxidative activity, and ROS appeared to be central in their CXCL8 and IL-6 responses. Activation of the MAPK p38 seemed to be a critical mediator. However, the NF-κB pathway appeared predominately to be involved only in Zn(2+)- and As(3+)-induced CXCL8 and IL-6 responses. Thus, the most potent metals Cd(2+), Zn(2+) and As(3+) seemed to induce a similar pattern for the cytokine responses, and with some exceptions, via similar signalling mechanisms.

Particulate matter air pollution components and risk for lung cancer.

BACKGROUND: Particulate matter (PM) air pollution is a human lung carcinogen; however, the components responsible have not been identified. We assessed the associations between PM components and lung cancer incidence. METHODS: We used data from 14 cohort studies in eight European countries. We geocoded baseline addresses and assessed air pollution with land-use regression models for eight elements (Cu, Fe, K, Ni, S, Si, V and Zn) in size fractions of PM2.5 and PM10. We used Cox regression models with adjustment for potential confounders for cohort-specific analyses and random effect models for meta-analysis. RESULTS: The 245,782 cohort members contributed 3,229,220 person-years at risk. During follow-up (mean, 13.1 years), 1878 incident cases of lung cancer were diagnosed. In the meta-analyses, elevated hazard ratios (HRs) for lung cancer were associated with all elements except V; none was statistically significant. In analyses restricted to participants who did not change residence during follow-up, statistically significant associations were found for PM2.5 Cu (HR, 1.25; 95% CI, 1.01-1.53 per 5 ng/m(3)), PM10 Zn (1.28; 1.02-1.59 per 20 ng/m(3)), PM10 S (1.58; 1.03-2.44 per 200 ng/m(3)), PM10 Ni (1.59; 1.12-2.26 per 2 ng/m(3)) and PM10 K (1.17; 1.02-1.33 per 100 ng/m(3)). In two-pollutant models, associations between PM10 and PM2.5 and lung cancer were largely explained by PM2.5 S. CONCLUSIONS: This study indicates that the association between PM in air pollution and lung cancer can be attributed to various PM components and sources. PM containing S and Ni might be particularly important.

Potential multiple functions of the v-myc oncogene within a single cell clone of OK10 retrovirus-transformed quail fibroblasts.

Propagation of in vitro transformed OK10 QDP 9c cells, cloned in soft agar, results in selective amplification of the OK10 pro-viral genome to yield a 12-fold increase in v-myc oncogene expression. In addition, increased v-myc oncogene dosage correlates with an increase of the proliferative potential of already transformed cells and relieves dependence on high serum concentrations for optimal cell growth. The increased rate of cell proliferation is reflected by a much more rapid progression through all parts of the cell cycle. These results suggest that the attainment of transformed status on one hand and progressive increase in growth factor independence for optimal cell proliferation on the other hand, may be initiated by different myc oncogene dosages within the OK10 QDP 9c cell clone.

Analytical electron microscopy of combustion particles: a comparison of vehicle exhaust and residential wood smoke.

Particulate matter has been associated with a number of adverse health effects. Since combustion particles from vehicle exhaust and wood smoke are common constituents of ambient air, the morphology and elemental composition of particles from these two sources were analysed and compared using single particle analysis. Ambient air particles were collected in locations dominated by vehicle exhaust or residential wood smoke. To verify the source contributions to the ambient air samples, particles were collected directly from the combustion sources. All particulate samples were analysed on carbon extraction replica by transmission electron microscopy (TEM) and X-ray microanalysis (XRMA). The particles were classified into four groups based on morphology and elemental composition. Carbon aggregates were the only particles identified to originate from combustion sources and accounted for more than 88% of the particle numbers in the ambient air samples from both sources. The carbon aggregates were therefore further analysed with respect to morphology and elemental composition on germanium extraction replica. Carbon aggregates from vehicle exhaust were characterised by higher levels of Si and Ca compared to wood smoke aggregates that contained higher levels of K. The S content in aggregates from both sources was probably caused by interaction with gases in the air. Furthermore, the diameters of primary particles from vehicle exhaust were significantly smaller (27+/-7 nm) than the diameters for wood smoke (38+/-11 nm). The observed differences in elemental profiles and primary particle diameters for vehicle exhaust and wood smoke may influence the health effects caused by these particles.

Inflammatory markers in bronchoalveolar lavage fluid from human volunteers 2 hours after hydrogen fluoride exposure.

Fluoride has been in focus as a possible causal agent for respiratory symptoms amongst aluminium potroom workers for several decades. Previously, using bronchoalveolar lavage (BAL), we demonstrated airway inflammation in healthy volunteers 24 hours after exposure to hydrogen fluoride (HF). The objective of the present study was to examine early lung responses to HF exposure. Bronchoscopy with BAL was performed 2 hours after the end of 1-hour exposure to HE Significant reductions in the total cell number and the number of neutrophils and lymphocytes were observed in bronchoalveolar portion (BAP), whereas there were no significant changes in the bronchial portion (BP). Significantly decreased concentrations of beta2-MG, IL-6 and total protein were found in both BAP and BP. Additionally, IL-8 was significantly reduced in BP, and ICAM-1 and albumin were present in lower concentrations in BAP. Lung function measurements were not affected by HF exposure. These reported effects are presumably transitory, as many were not present in the airways 24 hours after a similar HF exposure.

Differential distribution of Met and epidermal growth factor receptor in normal and carcinogen-treated rat liver.

Transforming growth factor-alpha (TGF-alpha) and hepatocyte growth factor (HGF) are strong hepatocyte mitogens and important regulators of liver regeneration. The TGF-alpha receptor EGFr appears primarily to mediate a proliferative signal, whereas mitogenic, motogenic, and morphogenic effects have been attributed to activation of the HGF receptor Met. We have studied the localization of Met and EGFr in normal and carcinogen-treated rat livers. Oval cells and preneoplastic lesions were induced by diethylnitrosamine initiation, followed by promotion with 2-acetylaminofluorene combined with a partial hepatectomy. Different liver cell populations and their receptor expression were characterized by two-color immunofluorescence and confocal laser scanning microscopy. Hepatocytes were detected by keratin K8 staining, and oval cells and bile ducts were recognized by keratin K19 expression. Enzyme-altered preneoplastic lesions ere identified by expression of placental glutathione S-transferase (GST-pi). Staining for these cellular markers was combined with immunodetection of EGFr and Met. Normal liver exhibited strong staining for EGFr in hepatocytes, whereas blood vessels, bile ducts, and some sinusoidal cells were Met-positive. In carcinogen-treated livers, oval cells showed Met but not EGFr immunostaining. GST-pi-positive foci displayed EGFr immunostaining at a similar intensity as surrounding hepatocytes, whereas Met was not detected. Our data indicate that putative liver cells (oval cells) have a growth receptor phenotype similar to that of bile ducts, whereas preneoplastic live lesions appear hepatocyte-like. These results indicate that the preferential proliferation of preneoplastic liver lesions compared to surrounding hepatocytes is not associated with an altered EGFr or Met phenotype.

Effect of tri-iodothyronine on protein turnover in rat hepatocyte primary cultures.

The effect of tri-iodothyronine (T3) on protein turnover was studied using primary cultures of rat hepatocytes. Protein synthesis was significantly stimulated in cells cultured for 6 days in the presence of T3 (1 mumol/l). Protein secretion into the culture medium was not affected by the hormone. Breakdown of long-lived proteins, the bulk of cellular proteins which are preferentially degraded through the autophagic lysosomal pathway, was significantly stimulated by the hormone. It is concluded that T3 elicits a general stimulation of protein turnover in cultured hepatocytes.

Gene activation studied by immunological methods.

Gene activation can be studied at several levels: transcription (mRNA), translation (proteins), or phenotypical alterations (functional activity or morphology). These levels can be studied in situ or biochemically by the use of specific probes for normal or altered DNA, mRNA, or proteins. Immunological probes are potent tools for studies of alterations induced by xenobiotics in target organs. When the effects of xenobiotics are studied in whole tissue, the cellular heterogeneity of the organ must be taken into account. For this reason, combined in situ and biochemical techniques are necessary. Antibodies to normal or altered cellular constituents are used for identification, quantitation, and cellular localization of proteins and modified DNA. Many xenobiotics alter gene activation by interactions with DNA. After activation, 2-acetylaminofluorene (AAF) forms DNA adducts, which can be identified immunologically. Combined with bromodeoxyuridine (BrdU) pulse labeling, techniques have been developed to demonstrate reduced adduct concentrations in proliferating cells and preneoplastic foci in the livers of AAF-fed rats. Carcinogen-induced DNA modifications are implicated as a major mechanism of altered gene activation in neoplasia, leading to phenotypical alterations. Also, cellular differentiation may be affected by xenobiotics. Differentiation-associated markers can be used for studies of gene activation. In mouse skin, the keratins K1 and K10 are only expressed in suprabasal, differentiating cells. BrdU pulse chase experiments combined with double immunofluorescence have revealed that K1 and K10 are sequentially turned on 18 to 24 hr after DNA synthesis and are followed by suprabasal migration. After a single application of the tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA), cell migration starts directly after mitosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferation of diploid hepatocytes and nonparenchymal (oval) cells during rat-liver regeneration in the presence of 2-acetylaminofluorene.

Treatment of rats with the carcinogen 2-acetylaminofluorene (2-AAF) during liver regeneration (Solt-Farber protocol) induced a selective outgrowth of diploid, gamma-glutamyltranspeptidase (GGT)-positive hepatocytes (3-4 times increase) as well as of nonparenchymal (oval) liver cells. After cessation of treatment the oval cells rapidly disappeared, while the population of diploid, GGT-positive hepatocytes declined more slowly over the subsequent ten weeks. In animals pretreated with the initiating carcinogen diethylnitrosamine (DEN) a large fraction of the diploid, GGT-positive hepatocytes persisted. The results differ from those obtained with our standard, sequential treatment protocol (2-AAF given after completed regeneration), where there is no hyperproliferation of oval cells and where GGT-positive hepatocytes are found only in DEN-pretreated animals (Saeter et al, Carcinogenesis 9: 581-587, 1988). Different experimental models of liver carcinogenesis may thus present different patterns of liver cell proliferation, which should be taken into account when general hypotheses on the cellular origin of liver cancer are proposed.