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The indirect immunofluorescence assay (IIFA) on HEp-2 cells is widely used for detection of antinuclear antibodies (ANA). The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases. However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s). The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells. The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns. In the current paper, the ICAP consensus is presented on the clinical relevance of the 29 distinct HEp-2 IIFA patterns. This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing. The discussion includes how this information may benefit the clinicians in daily practice and how the knowledge can be used to further improve diagnostic and classification criteria.

The indirect immunofluorescence assay (IIFA) on HEp-2 cells is widely used for detection of antinuclear antibodies (ANA). The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases. However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s). The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells. The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns. In the current paper, the ICAP consensus is presented on the clinical relevance of the 29 distinct HEp-2 IIFA patterns. This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing. The discussion includes how this information may benefit the clinicians in daily practice and how the knowledge can be used to further improve diagnostic and classification criteria.

Soybean toxin (SBTX) is a protein isolated from soybean seeds and composed of two polypeptide subunits (17 and 27 kDa). SBTX has in vitro activity against phytopathogenic fungi such as Cercospora sojina, Aspergillus niger, and Penicillium herguei, and yeasts like Candida albicans, C. parapsilosis, Kluyveromyces marxiannus, and Pichia membranifaciens. The present study aimed to analyze in vitro whether SBTX causes any side effects on non-target bacterial and mammalian cells that could impede its potential use as a novel antifungal agent. SBTX at 100 mu g/mL and 200 mu g/mL did not hinder the growth of the bacteria Salmonella enterica (subspecies enterica serovar choleraesuis), Bacillus subtilis (subspecies spizizenii) and Staphylococcus aureus. Moreover, SBTX at concentrations up to 500 mu g/mL did not significantly affect the viability of erythrocytes, neutrophils, and human intestinal Caco-2 cells. To study whether SBTX could induce relevant alterations in gene expression, in vitro DNA microarray experiments were conducted in which differentiated Caco-2 cells were exposed for 24 h to 100 mu g/mL or 200 mu g/mL SBTX. SBTX up-regulated genes involved in cell cycle and immune response pathways, but downregulated genes that play a role in cholesterol biosynthesis and platelet degranulation pathways. Thus, although SBTX did not affect bacteria, nor induced cytotoxity in mammalian cells, it affected some biological pathways in the human Caco-2 cell line that warrants further investigation.

Deep understanding of tooth regeneration is hampered by the lack of lifelong replacing oral dentition in most conventional models. Here, we show that the bearded dragon, one of the rare vertebrate species with both polyphyodont and monophyodont teeth, constitutes a key model for filling this gap, allowing direct comparison of extreme dentition types. Our developmental and high-throughput transcriptomic data of microdissected dental cells unveils the critical importance of successional dental lamina patterning, in addition to maintenance, for vertebrate tooth renewal. This patterning process happens at various levels, including directional growth but also gene expression levels, dynamics, and regionalization, and involves a large number of yet uncharacterized dental genes. Furthermore, the alternative renewal mechanism of bearded dragon dentition, with dual location of slow-cycling cells, demonstrates the importance of cell migration and functional specialization of putative epithelial stem/progenitor niches in tissue regeneration, while expanding the diversity of dental replacement strategies in vertebrates., eLife digest All multicellular organisms, from lizards to humans, must be able to repair and regrow damaged tissue. This includes not only healing after an injury, but also replacing parts of the body that suffer wear and tear. For example, many animals shed and replace worn out teeth throughout their life, but the number of times this occurs varies greatly between species. Much of the understanding about how teeth grow and develop has come from researching mice. However, mice only develop one set of teeth, making them a poor ‘model’ for studying how species such as fish and reptiles can re-grow and replace their teeth. Recent studies of these species has shown that regenerating teeth relies on a specialised structure known as the dental lamina. In mice, the dental lamina forms but then quickly disappears, preventing new sets of teeth from developing. In most animals that regrow their teeth, however, the dental lamina keeps growing beyond the most recently produced tooth to create an area where its replacement will emerge. Now, Salomies et al. have identified other strategies involved in tooth replacement from studying the bearded dragon lizard, a rare example of an animal that continuously regenerates some, but not all, of its teeth. Analysing the cells in different parts of the re-growing teeth from bearded dragon lizards revealed new features of the dental lamina. Specifically, Salomies et al. found that a previously uncharacterized set of genes within the dental lamina could determine whether or not a tooth will be replaced. Further experiments using microscope imaging revealed that bearded dragon lizards use two distinct groups of stem cells – specialised cells that have the potential to develop into various cell types in the body – to re-grow their teeth. These experiments demonstrate how the bearded dragon lizard uses a previously unknown mechanism to regenerate its teeth, combining elements used by gecko lizards and sharks. These findings are an important step towards understanding the different strategies animals can use to maintain and regenerate their teeth. The knowledge gained could one day help design better therapies for patients suffering from inherited dental disorders or tooth loss.

Summary Human RTEL1 is an essential, multifunctional helicase that maintains telomeres, regulates homologous recombination, and helps prevent bone marrow failure. Here, we show that RTEL1 also blocks trinucleotide repeat expansions, the causal mutation for 17 neurological diseases. Increased expansion frequencies of (CTG⋅CAG) repeats occurred in human cells following knockdown of RTEL1, but not the alternative helicase Fbh1, and purified RTEL1 efficiently unwound triplet repeat hairpins in vitro. The expansion-blocking activity of RTEL1 also required Rad18 and HLTF, homologs of yeast Rad18 and Rad5. These findings are reminiscent of budding yeast Srs2, which inhibits expansions, unwinds hairpins, and prevents triplet-repeat-induced chromosome fragility. Accordingly, we found expansions and fragility were suppressed in yeast srs2 mutants expressing RTEL1, but not Fbh1. We propose that RTEL1 serves as a human analog of Srs2 to inhibit (CTG⋅CAG) repeat expansions and fragility, likely by unwinding problematic hairpins.

The recent advent in single-molecule imaging and manipulation methods has made a significant impact on the understanding of molecular mechanisms underlying many essential cellular processes. Single-molecule techniques such as electron microscopy and DNA fiber assays have been employed to study the duplication of genome in eukaryotes. Here, we describe a single-molecule assay that allows replication of DNA attached to the functionalized surface of a microfluidic flow cell in a soluble Xenopus leavis egg extract replication system and subsequent visualization of replication products via fluorescence microscopy. We also explain a method for detection of replication proteins, through fluorescently labeled antibodies, on partially replicated DNA immobilized at both ends to the surface. (c) 2012 Elsevier Inc. All rights reserved.

Objectives: Brain single-photon emission computed tomography (SPECT) has been proposed as a potentially useful modality for the metabolic assessment of various brain tumors. Material and methods: In a 10-patient prospective pilot study we evaluated whether (99m)Tc-Tetrofosmin ((99m)Tc-TF) uptake correlates with glioma proliferative activity assessed by flow cytometric analysis. (99m)Tc-TF brain SPECT was performed shortly before surgical tumor excision. Results: Eight patients were diagnosed with glioblastoma multiform and 2 with anaplastic astrocytoma. All tumors were aneuploid. We found a significant positive linear correlation between 99mTc-TF uptake and percentage of tumor cells on the S-phase of the cell cycle (r=0.92, P=0.001). Conclusion: Initial evidence suggests that 99mTc-TF could provide a non-invasive indicator of glioma proliferative activity. (C) 2009 Elsevier B.V. All rights reserved. Clin Neurol Neurosurg

The aim of the present study was to assess the influence of quercetine (QE) on liver regeneration after partial hepatectomy (PH) in rats. A total of 24 male Wistar albino rats were divided into three groups: sham-operated (SH), PH and PH+QE; each group contain 8 animals. The rats in QE-treated groups were given QE (15 mg/kg body weight) once a day i. p., for 7 days starting 3 days prior to hepatectomy operation. At 7 days after resection, liver samples were collected. The malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) levels were estimated in liver homogenates. Moreover, histopathological examination, mitotic index (MI), proliferating cell nuclear antigen labelling, proliferation index (PI), transferase-mediated dUTP nick end-labelling assay, apoptotic index (AI) were evaluated at 7 days after hepatectomy. As a result, QE significantly increased MI, PI, and significantly decreased AI in PH rats. Additionally, QE remarkably inhibited the elevation of MDA, restored impaired antioxidant SOD activity and GSH level, and also attenuated hepatic vacuolar degeneration and sinusoidal congestion. These results suggested that QE treatment had a beneficial effect on liver regenerative capacity of the remnant liver tissue after hepatectomy, probably due to its antioxidative, antiapoptotic and proliferative property.

Y.H. thanks Dr. Zhengding Su and Mr. Cheon-Gil Park for their help in experiments.; International audience; The Cip/Kip family of cyclin-dependent kinase (Cdk) inhibitors includes p21(Cip1) p27(Kip1) and d57(Kip2). Their kinase inhibitory activities are mediated by a homologous N-terminal kinaseinhibitory domain. The Cdk inhibitory activity and stability of p27 have been shown to be regulated by a two-step phosphorylation mechanism involving a tyrosine residue within the kinase inhibitory domain and a threonine residue within the flexible C-terminus. We show that these residues are conserved in p21 and p57, suggesting that a similar phosphorylation cascade regulates these Cdk inhibitors. However, the presence of a cyclin binding motif within its C-terminus alters the regulatory interplay between p21 and Cdk2/cyclin A, as well as its responses to tyrosine phosphorylation and altered p21:Cdk2/cyclin A stoichiometry. We also show that the Cip/Kip proteins can be phosphorylated in vitro by representatives of many non-receptor tyrosine kinase (NRTK) sub-families, suggesting that NRTKs may generally regulate the activity and stability of these Cdk inhibitors. Our results further suggest that the Cip/Kip proteins integrate signals from various NRTK pathways and cell cycle regulation

Heat-induced retrieval of antigens masked by formalin fixation in paraffin-embedded tissue is widely used in routine surgical pathology. Microwave heating at high temperature for a relatively short period has been tested extensively. Although good results for commonly used antibodies are obtained by optimizing heating conditions and retrieval solutions, a standard protocol for all antibodies is not yet available. Other problems encountered are affected morphology and loss of tissue attachment to the slides. In this study we elaborated a previously described retrieval method applying conventional heating at a lower temperature for a prolonged time. We tested 16 routinely used antibodies on formalin-fixed, paraffin-embedded tissues, which were stained after overnight heating at 80 degrees C in retrieval solutions varying in pH value. The results were compared with standard microwave heating in a solution of Tris-HCl plus urea pH 9.5. Maximal retrieval was obtained with 14 out of 16 antibodies by overnight heating at 80 degrees C in Tris buffer pH 9. Tissue morphology was well preserved. The results were slightly superior to those obtained with microwave retrieval in pH 9.5 Tris+urea buffer. Tn conclusion, overnight heating at 80 degrees C in Tris buffer pH 9 is a good alternative for retrieval of antigens and is easy to perform.

To validate the protein synthesis rate (PSR) measured in human brain tumors using L-[1-C-11]tyrosine (TYR) PET, the PSR was compared to histopathological parameters that reflect proliferation and protein synthesis. Methods: We studied 20 patients who had a brain biopsy and who also underwent a PET study with TYR. Paraffin sections were stained with the monoclonal antibody MIB 1, targeted against the core antigen Ki-67, and nucleolar organizer regions (NORs) were measured as argyrophilic NORs (AgNORs). The TYR uptake was measured by PET, and with a kinetic model, the PSR was determined. Results: PSR (nmol/ml/min) ranged from 0.44 to 1.99 (mean, 0.97), Ki-67 labeling indices (%) ranged from 0.9 to 33.5 (mean, 9.5) and AgNOR area (mm(2)/cm(2)) ranged from 0.13 to 0.85. No relationship was found between PSR and Ki-67 labeling index or AgNOR area. Conclusion: It seems that the PSR and proliferation, as measured by Ki-67, are independent processes. The role of the PSR is uncertain, but it is likely that it can be seen as a marker for the homeostasis of the cell.

International audience; Archaeal family-D DNA polymerase is inhibited by the presence of uracil in DNA template strands. When the enzyme encounters uracil, following three parameters change: DNA binding increases roughly 2-fold, the rate of polymerization slows by a factor of ≈ 5 and 3'-5' proof-reading exonuclease activity is stimulated by a factor of ≈ 2. Together these changes result in a significant decrease in polymerization activity and a reduction in net DNA synthesis. Pol D appears to interact with template strand uracil irrespective of its distance ahead of the replication fork. Polymerization does not stop at a defined location relative to uracil, rather a general decrease in DNA synthesis is observed. 'Trans' inhibition, the slowing of Pol D by uracil on a DNA strand not being replicated is also observed. It is proposed that Pol D is able to interact with uracil by looping out the single-stranded template, allowing simultaneous contact of both the base and the primer-template junction to give a polymerase-DNA complex with diminished extension ability.

Hepatitis B virus (HBV)- and hepatitis C virus (HCV)-related liver damage is linked to an increased risk of hepatocellular carcinoma, but the mechanisms underlying hepatitis C viral activity are not known. We therefore compared hepatocellular proliferative activity in chronic C virus-related hepatitis and in liver damage of other etiology. Hepatocyte proliferation rate was investigated in 56 patients with chronic hepatitis using the Ki67 MIB1 monoclonal antibody in archival material. According to etiology, the patients were subgrouped as follows: HCV (34), HBV (11), Alcohol (4), HCV + Alcohol (4), and Hemochromatosis (3). Proliferation rate was correlated with age, sex, etiology, disease activity, liver iron storage, free-radical production, and glutathione levels by regression and discriminant analysis. HCV-positive patients had significantly more MIB1-positive hepatocytes in the periportal area (P < .011) and in the low-proliferating perivenular area (zones 2 and 3) (P < .05). The number of MIB1-positive cells correlated directly with alanine transaminase (ALT) levels, Knodell index (KI), and, inversely, with iron saturation. By stepwise discriminant analysis, ALT levels and etiology were identified as single independent variables. These data suggest that HCV infection induces increased and abnormal hepatocyte proliferation, which might be related to the increased risk of hepatocellular carcinoma in patients with HCV-related liver damage.

International audience; Pyrococcus abyssi NucS is the founding member of a new family of structure-specific DNA endonucleases that interact with the replication clamp proliferating cell nuclear antigen (PCNA). Using a combination of small angle x-ray scattering and surface plasmon resonance analyses, we demonstrate the formation of a stable complex in solution, in which one molecule of the PabNucS homodimer binds to the outside surface of the PabPCNA homotrimer. Using fluorescent labels, PCNA is shown to increase the binding affinity of NucS toward single-strand/double-strand junctions on 5′ and 3′ flaps, as well as to modulate the cleavage specificity on the branched DNA structures. Our results indicate that the presence of a single major contact between the PabNucS and PabPCNA proteins, together with the complex-induced DNA bending, facilitate conformational flexibility required for specific cleavage at the single-strand/double-strand DNA junction. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.

Barrett's oesophagus or columnar epithelium-lined oesophagus is a condition due to chronic gastrooesophageal reflux. In addition to acid-peptic reflux, reflux of duodenal contents may have a role in its aetiology. The clinical importance of Barrett's oesophagus is the increased risk for development of oesophageal adenocarcinoma. Measures to prevent cancer development have so far been limited to regular screening and early oesophagectomy in the case of severe dysplasia or early cancer. Other modes of intervention, directed toward prevention of dysplasia and possibly regression of Barrett's epithelium, should be sought. Early markers of development toward dysplasia and cancer are necessary if we are to be able to evaluate such measures. Determination of epithelial cell proliferative activity has the potential to be such a marker. A study is now being performed to evaluate the effect of elimination of acid reflux on proliferative activity of Barrett's epithelium in conjunction with the effects of inflammation and development of dysplasia.

This work demonstrates the assembly of TiO 2 nanoparticles with attached DNA oligonucleotides into a 3D mesh structure by allowing base pairing between oligonucleotides. A change of the ratio of DNA oligonucleotide molecules and TiO 2 nanoparticles regulates the size of the mesh as characterized by UV-visible light spectra, transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. This type of 3D mesh, based on TiO 2-DNA oligonucleotide nanoconjugates, can be used for studies of nanoparticle assemblies in materials science, energy science related to dye-sensitized solar cells, environmental science as well as characterization of DNA interacting proteins in the field of molecular biology. As an example of one such assembly, proliferating cell nuclear antigen protein (PCNA) was cloned, its activity was verified, and the protein was purified, loaded onto double strand DNA oligonucleotide- TiO 2 nanoconjugates, and imaged by atomic force microscopy. This type of approach may be used to sample and perhaps quantify and/or extract specific cellular proteins from complex cellular protein mixtures based on their affinity for chosen DNA segments assembled into the 3D matrix.

DNA polymerase epsilon co-operates with polymerases alpha and delta in the replicative DNA synthesis of eukaryotic cells. We describe here a specific physical interaction between DNA polymerase epsilon and RNA polymerase II, evidenced by reciprocal immunoprecipitation experiments. The interacting RNA polymerase II was the hyperphosphorylated IIO form implicated in transcriptional elongation, as inferred from (a) its reduced electrophoretic mobility that was lost upon phosphatase treatment, (b) correlation of the interaction with phosphorylation of Ser5 of the C-terminal domain heptapeptide repeat, and (c) the ability of C-terminal domain kinase inhibitors to abolish it. Polymerase epsilon was also shown to UV crosslink specifically alpha-amanitin-sensitive transcripts, unlike DNA polymerase alpha that crosslinked only to RNA-primed nascent DNA. Immunofluorescence microscopy revealed partial colocalization of RNA polymerase IIO and DNA polymerase epsilon, and immunoelectron microscopy revealed RNA polymerase IIO and DNA polymerase epsilon in defined nuclear clusters at various cell cycle stages. The RNA polymerase IIO-DNA polymerase epsilon complex did not relocalize to specific sites of DNA damage after focal UV damage. Their interaction was also independent of active DNA synthesis or defined cell cycle stage.

The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication.

ATMACA, HASAN TARIK/0000-0001-8379-4114 WOS: 000238785600008 PubMed: 16841759 In this report, the late clinical, necropsy, and histopathological findings of idiopathic gastric stasis in an ostrich are described, with special attention to the proventriculus. An ostrich with clinical signs of gastric stasis was brought to our clinic in a state of impending death that could not be reversed with emergency medical care. At necropsy, the koilin layer of the gizzard was uneven without ulcerations. The proventriculus was distended with food items without impaction and mucosal lesions. None of the most typical aetiological factors including foreign objects, Macrorhabdus ornithogaster and parasitic infection with Libyostrongylus douglassii was present. Histologically, the proventriculus was characterised by hyperplastic mucosa with luminal buds and necrotic cells in the lumen. Immunochemistry for proliferating cell nuclear antigen ( PCNA) revealed a high rate of proliferation in epithelial cells of the glandular and mucosal lining in the proventriculus neighbouring the affected gizzard: approximately 88.6% of the cells were immunoreactive as compared to 34.4% of the cells in control ostriches used for comparison. In conclusion, in the absence of gizzard contraction, the mucosal lining of the proventriculus is hyperplastic with a high rate of proliferation that may help compensate the distension due to the accumulation of food items.

Heat-induced retrieval of antigens masked by formalin fixation in paraffin-embedded tissue is widely used in routine surgical pathology. Microwave heating at high temperature for a relatively short period has been tested extensively. Although good results for commonly used antibodies are obtained by optimizing heating conditions and retrieval solutions, a standard protocol for all antibodies is not yet available. Other problems encountered are affected morphology and loss of tissue attachment to the slides. In this study we elaborated a previously described retrieval method applying conventional heating at a lower temperature for a prolonged time. We tested 16 routinely used antibodies on formalin-fixed, paraffin-embedded tissues, which were stained after overnight heating at 80 degrees C in retrieval solutions varying in pH value. The results were compared with standard microwave heating in a solution of Tris-HCl plus urea pH 9.5. Maximal retrieval was obtained with 14 out of 16 antibodies by overnight heating at 80 degrees C in Tris buffer pH 9. Tissue morphology was well preserved. The results were slightly superior to those obtained with microwave retrieval in pH 9.5 Tris+urea buffer. Tn conclusion, overnight heating at 80 degrees C in Tris buffer pH 9 is a good alternative for retrieval of antigens and is easy to perform.

To validate the protein synthesis rate (PSR) measured in human brain tumors using L-[1-C-11]tyrosine (TYR) PET, the PSR was compared to histopathological parameters that reflect proliferation and protein synthesis. Methods: We studied 20 patients who had a brain biopsy and who also underwent a PET study with TYR. Paraffin sections were stained with the monoclonal antibody MIB 1, targeted against the core antigen Ki-67, and nucleolar organizer regions (NORs) were measured as argyrophilic NORs (AgNORs). The TYR uptake was measured by PET, and with a kinetic model, the PSR was determined. Results: PSR (nmol/ml/min) ranged from 0.44 to 1.99 (mean, 0.97), Ki-67 labeling indices (%) ranged from 0.9 to 33.5 (mean, 9.5) and AgNOR area (mm(2)/cm(2)) ranged from 0.13 to 0.85. No relationship was found between PSR and Ki-67 labeling index or AgNOR area. Conclusion: It seems that the PSR and proliferation, as measured by Ki-67, are independent processes. The role of the PSR is uncertain, but it is likely that it can be seen as a marker for the homeostasis of the cell.

International audience; Ubiquitin-binding domains (UBDs) provide specificity to the ubiquitin system, which is also involved in translesion synthesis (TLS) in eukaryotic cells. Upon DNA damage, the UBDs (UBM domains) of polymerase iota (Pol ι) interact with ubiquitinated proliferating cell nuclear antigen to regulate the interchange between processive DNA polymerases and TLS. We report a biophysical analysis and solution structures of the two conserved UBM domains located in the C-terminal tail of murine Pol ι in complex with ubiquitin. The 35-amino acid core folds into a helix-turn-helix motif, which belongs to a novel domain fold. Similar to other UBDs, UBMs bind to ubiquitin on the hydrophobic surface delineated by Leu-8, Ile-44, and Val-70, however, slightly shifted toward the C terminus. In addition, UBMs also use electrostatic interactions to stabilize binding. NMR and fluorescence spectroscopy measurements revealed that UBMs bind monoubiquitin, and Lys-63- but not Lys-48-linked chains. Importantly, these biophysical data are supported by functional studies. Indeed, yeast cells expressing ubiquitin mutants specifically defective for UBM binding are viable but sensitive to DNA damaging conditions that require TLS for repair.

Barrett's oesophagus or columnar epithelium-lined oesophagus is a condition due to chronic gastrooesophageal reflux. In addition to acid-peptic reflux, reflux of duodenal contents may have a role in its aetiology. The clinical importance of Barrett's oesophagus is the increased risk for development of oesophageal adenocarcinoma. Measures to prevent cancer development have so far been limited to regular screening and early oesophagectomy in the case of severe dysplasia or early cancer. Other modes of intervention, directed toward prevention of dysplasia and possibly regression of Barrett's epithelium, should be sought. Early markers of development toward dysplasia and cancer are necessary if we are to be able to evaluate such measures. Determination of epithelial cell proliferative activity has the potential to be such a marker. A study is now being performed to evaluate the effect of elimination of acid reflux on proliferative activity of Barrett's epithelium in conjunction with the effects of inflammation and development of dysplasia.