The Relative Abundance of Desert Tortoises on the Nevada Test Site within Ecological Landform Units

Sign-survey transects were sampled in 1996 to better determine the relative abundance of desert tortoises on the Nevada Test Site (NTS). These transects were sampled within ecological land-form units (ELUs), which are small, ecologically homogeneous units of land. Two-hundred and six ELUs were sampled by walking 332 transects totaling 889 kilometers (km). These ELUs covered 528 km{sup 2}. Two-hundred and eight-one sign were counted. An average of 0.32 sign was found per km walked. Seventy percent of the area sampled had a very low abundance of tortoises, 29% had a low abundance, and 1% had a moderate abundance. A revised map of the relative abundance of desert tortoise on the NTS is presented. Within the 1,330 km{sup 2} of desert tortoise habitat on the NTS, 49% is classified as having no tortoises or a very low abundance, 18% has a low or moderate abundance, 12% is unclassified land being used by the Yucca Mountain Site Characterization Project, and the remaining 21% still has an unknown abundance of desert tortoises. Based on the results of this work, the amount of tortoise habitat previously classified as having an unknown or low-moderate abundance, and on which clearance surveys and on-site monitoring was required, has been reduced by 20%

A new Rothamsted long-term field experiment for the twenty-first century - principles and practice

Agriculture faces potentially competing societal demands to produce food, fiber and fuel while reducing negative environmental impacts and delivering regulating, supporting and cultural ecosystem services. This necessitates a new generation of long-term agricultural field experiments designed to study the behavior of contrasting cropping systems in terms of multiple outcomes. We document the principles and practices of a new long-term experiment of this type at Rothamsted, established at two contrasting sites in 2017 and 2018, and report initial yield data at the crop and system level. The objective of the Large-Scale Rotation Experiment was to establish gradients of system properties and outcomes to improve our fundamental understanding of UK cropping systems. It is composed of four management factors—phased rotations, cultivation (conventional vs reduced tillage), nutrition (additional organic amendment vs standard mineral fertilization) and crop protection (conventional vs smart crop protection). These factors were combined in a balanced design resulting in 24 emergent cropping systems at each site and can be analyzed at the level of the system or component management factors. We observed interactions between management factors and with the environment on crop yields, justifying the systems level, multi-site approach. Reduced tillage resulted in lower wheat yields but the effect varied with rotation, previous-crop and site. Organic amendments significantly increased spring barley yield by 8% on average though the effect again varied with site. The plowed cropping systems tended to produce higher caloric yield overall than systems under reduced tillage. Additional response variables are being monitored to study synergies and trade-offs with outcomes other than yield at the cropping system level. The experiment has been established as a long-term resource for inter-disciplinary research. By documenting the design process, we aim to facilitate the adoption of similar approaches to system-scale agricultural experimentation to inform the transition to more sustainable cropping systems

Photoperoxidation of a Diamino Zinc Porphyrazine to the seco-Zinc Porphyrazine: Suicide or Murder?

We report on the efficient photooxidation of hexapropyl bis(dimethylamino) zinc porphyrazine. The process is shown to be autocatalytic. The triplet state of the seco-ZnPz sensitizes the formation of excited-state singlet oxygen with a quantum yield of 0.54 and subsequent cleavage of the pyrrole double bond occurs to give the product, seco-zinc porphyrazine. The photophysics of the two porphyrazines is examined using absorption, emission, and transient absorption spectroscopy. The efficiency of production of singlet oxygen is monitored using the phosphorescence emission signature at 1270 nm. Introduction We reported recently the synthesis of porphyrazineoctamines by macrocyclization of diamino maleonitrile derivatives using magnesium propoxide in propanol. 1 During several Linstead macrocyclization 2 reactions of bis(dimethylamino)maleonitrile, we observed the formation of a minor side product, the secoporphyrazine 1 In this paper, we report the results from the photophysical studies of both the reactant, 2, and product, 4, and show that the full reaction mechanism of the photoperoxidation involves attack on the reactant by singlet oxygen that has been sensitized by the triplet state of the product. As a consequence, the kinetics of the process are shown to be autocatalytic where the reactant is removed at a rate that increases with the amount of product formed. Experimental Section Chemicals. The preparation, purification and characterization of ZnPz and seco-ZnPz have been described previously. Steady-State Absorption and Emission Measurements. Electronic absorption spectra were recorded on a dual beam UV/ vis spectrometer (Perkin-Elmer Lambda-2) with fixed 2 nm resolution. Fluorescence emission and excitation spectra were recorded on a spectrometer with xenon arc lamp excitation and a photon-counting detection system (Instruments SA Fluoromax). Fluorescence quantum yields were determined by the comparative method 7 using chlorophyll a in ether (φ F ) 0.32 ( 0.05) as the reference standard. To avoid unwanted reabsorption effects, all fluorescence measurements were recorded on solutions with Q-band absorbances of less than 0.1 in 1 cm path length cells. Time-Resolved Fluorescence Measurements. Fluorescence decays were recorded using a time-correlated single-photon counting spectrometer with pulsed laser excitation at an excitation wavelength, λ ex , of 670 nm, 10 ps pulse duration, and a repetition rate of 3.8 MHz. Fluorescence was detected perpendicular to the direction of excitation, dispersed through a subtractive dispersion monochromator, and subsequently detected by a microchannel plate photomultiplier tube that provided an overall time resolution of less than 100 ps. The decays were analyzed using a nonlinear, least-squares, iterative reconvolution procedure and stringent data fitting criteria. Results The electronic absorption spectrum of ZnPz 2 has a distinct Q-band at 600 nm (see A purified sample of ZnPz was dissolved in cyclohexane to a concentration of 1.07 × 10 -5 mol dm -3 , placed in a conventional 1 cm cuvette, and allowed to equilibrate with air at 295 K and an absorption spectrum was measured. The sample was irradiated with white light by placing it 30 cm in front of a 60 W tungsten filament lamp for 10 min. The sample was then returned to the spectrometer and a new spectrum was Photoperoxidation of a Diamino Zinc Porphyrazine J. Phys. Chem. A, Vol. 103, No. 22, 1999 4353 recorded. This process was then repeated until no further changes in the spectrum could be observed. The results from this study are shown in Before irradiation the emission shows one peak at 605 nm. A new peak at 708 nm grows in with irradiation, reaching a maximum after 20 min, as shown in the inset of Fluorescence decays of seco-ZnPz at various emission wavelengths were measured after irradiation and were adequately described by a biexponential function with decay times of 0.73 ns and 0.16 ns and contributions of 76.6% and 23.4%, respectively. A fresh sample of ZnPz in degassed toluene was prepared in order to record fluorescence emission and excitation spectra of the ZnPz, but no fluorescence was detected, although the 605 nm peak attributed to the octapropyl zinc porphyrazine was still evident. The fluorescence data for ZnPz and seco-ZnPz suggest that the major deactivation pathways for the excited state of each are nonradiative. The possibility that this is due to intersystem crossing to the triplet state was then investigated using kinetic and spectral transient absorption spectroscopy. Bleaching of the ground state population is clearly indicated by the depletion in the absorption cross section of the sample at 650 and 560 nm, corresponding to the Q-bands, and at 340 nm, corresponding to the Soret band. To this bleaching is added a broad triplet state (T 1 f T n ) absorption that is clearly observed in the region 390-520 nm, where little ground-state singlet (S 0 f S n ) absorption occurs. The extinction coefficient at the maximum in this range, 427 nm, was calculated to be 0.97 × 10 4 dm 3 mol -1 cm -1 and the quantum yield for triplet state formation, φ T , as 0.64 ( 0.06. A typical transient decay profile for air-free seco-ZnPz in this spectral region is shown in A sample of air-equilibrated seco-ZnPz in toluene solution was then investigated by observing the effect of the 3 O 2 on the transient absorption decay and also by detecting emission at 1270 nm, where singlet oxygen phosphoresces. The change in the transient decay rate of the seco-ZnPz was so dramatic as to be difficult to measure accurately. Conversely, characteristic singlet oxygen emission was readily observed indicating that the triplet state of the seco-ZnPz was efficiently quenched by the dissolved oxygen. The singlet oxygen emission decayed exponentially with a characteristic lifetime of 29 µs, as shown 4354 J. Phys. Chem. A, Vol. 103, No. 22, 1999 Montalban et al. in Analysis The absorption spectra, shown in parts a and j of The four molar decadic extinction coefficients are given in The functional form of these kinetic data is neither first nor second order, but is indicative of autocatalysis, where the product, seco-ZnPz, catalyzes the rate of photoperoxidation of the ZnPz. The rate law for the autocatalysis is given by (1) Photoperoxidation of a Diamino Zinc Porphyrazine J. Phys. Chem. A, Vol. 103, No. 22, 1999 4355 ZnPz] 0 ) 7 × 10 -9 mol dm -3 , and k ) 1.5 × 10 4 dm 3 mol -1 min -1 the data were satisfactorily modeled using eqs 4 and 5, the results of which are shown as the solid lines in To be consistent with the model, the concentration of singlet oxygen must be directly proportional to the concentration of seco-ZnPz such that the proportionality constant remains unchanged during the course of the reaction. These assumptions can be shown to be true (see appendix) if the following criteria are met. (1) Some minimal sensitization must first occur in order to initiate the photoperoxidation, but the rate of this process is rapidly exceeded by the seco-ZnPz. (2) The rate constant for the peroxidation process is very small with respect to the normal, unimolecular deactivation rate constants of the singlet oxygen. (3) The concentration of dissolved oxygen must be large with respect to the initial concentration of ZnPz, such that it remains effectively unchanged during the course of the photoperoxidation. In this case, the apparent second-order rate constant is expected to be proportional to the light intensity and related to the ground-state oxygen concentration (see appendix). The initial concentration of seco-ZnPz, [seco-ZnPz] 0 , was determined to be 7 × 10 -9 mol dm -3 , a value that is 3 orders of magnitude smaller than that of the ZnPz starting material. The experiment was repeated twice more with the starting solution spiked with different amounts of seco-ZnPz. In both cases, the overall rate of reaction increased dramatically, although the derived second-order rate constant, k, was found to have a value within 10% of the value for the unspiked reaction. It is thus evident that the sensitizing properties of the seco-ZnPz product far exceed those of the ZnPz starting material. This conclusion is consistent with the results from the triplet state studies in which the quantum yield for triplet state formation, φ T , is 0.64 for the seco-ZnPz but immeasurable for the ZnPz. The rapid growth of the singlet oxygen signal, when examining air-equilibrated solutions of ZnPz, can similarly be attributed to the formation of seco-ZnPz which then catalyzes further production. The singlet oxygen phosphorescence signal decays at the same rate during the course of the photoperoxidation, which demonstrates that the rate constant for this chemical reaction is small with respect to the rate constants for the other excited-state deactivation mechanisms, as required by the second criterion listed above, for the autocatalysis kinetic mechanism. The final requirement, that the concentration of normal, triplet state oxygen remains unchanged, is also fulfilled as the initial concentration of ZnPz was 1.07 × 10 -5 mol dm -3 while that of dissolved oxygen in toluene at room temperature 13 is 200 times higher at 2 × 10 -3 mol dm -3 . The photoperoxidation of ZnPz to seco-ZnPz results from the attack on ZnPz by singlet oxygen that is sensitized by the triplet state of the seco-ZnPz product (vide supra). The concentration of ground-state oxygen remains unchanged during the chemical reaction and the rate constant for the photoperoxidation process is much smaller than all other excited-state deactivation mechanisms for singlet oxygen. These effects lead to a concentration of the reactive, singlet oxygen that is proportional to the concentration of the product, seco-ZnPz (eq A5) and hence an autocatalytic kinetic mechanism is observed. The rate constant, k, is independent of the initial concentrations of both ZnPz and seco-ZnPz, although it does depend on the light intensity and on [ 3 O 2 ], but this was not explored fully. Using the same irradiation conditions, the effect of solvent was very pronounced with noncoordinating solvents, such as toluene, cyclohexane, and dichloromethane behaving in a similar fashion. The use of pyridine as a coordinating solvent reduced the rate constant for the reaction by a factor of 20. This is consistent with our previous observation 4 that ZnPz appeared to be more stable in coordinating solvents. Discussion The photophysical data for ZnPz suggests that the dominant deactivation process for the first excited singlet state is neither fluorescence nor intersystem crossing and by the process of elimination it is probably direct internal conversion to the ground state, followed by vibrational relaxation. The seco-ZnPz is more interesting photophysically, exhibiting fluorescence as well as intersystem crossing (φ T ) 0.64) as the dominant deactivation pathway. The sensitivity of fluorescence spectroscopy enables the radiative process to be observed readily even though it is 200 times less efficient. Again internal conversion probably constitutes the remaining 36% of the deactivation mechanisms. The emission peak at 605 nm we assign to a small amount of octapropyl zinc porphyrazine not observable by electronic absorption or other techniques. The emission at 708 nm from the seco-ZnPz has a very low fluorescence quantum yield. It decays biexponentially, but both of the measured fluorescence decay times are relatively long, results that are consistent with long natural, radiative lifetimes. As a guide, the average lifetime of the emission of 0.6 ns can be combined with quantum yield to produce a natural radiative lifetime of 170 ns. This value is inconsistent with the very large extinction coefficient ( 648 ) 38 320) for the lowest energy Q-band of the seco-ZnPz, where the Strickler-Berg relationship 14 predicts a value closer to 2 Phys. Chem. A, Vol. 103, No. 22, 1999 Montalban et al. ns. It could, however, be due to emission emanating from a state of the seco-ZnPz that is lower in energy than the Q-band at 648 nm, but is not coupled radiatively with the ground state and does not appear in the absorption spectrum. This argument is consistent with the large Stokes shift between the lowest energy absorption band (648 nm) and the emission maximum at 708 nm. The production of singlet oxygen by seco-ZnPz must occur via the triplet state as the excited singlet state of seco-ZnPz is too short lived to interact with ground-state oxygen by diffusion. The quantum yield of singlet oxygen production is a combination of the intersystem crossing and sensitization by quenching. Since ZnPz has a low intersystem crossing quantum yield, the difficulty in measuring a singlet oxygen signal for ZnPz may not be due to inefficiency in the sensitization by the triplet state. The peroxidation process is, however, initiated. This may be an indication that sensitization by ZnPz is possible, but not easily measured, or that the process is initiated by the extremely small amount of octapropyl zinc porphyrazine that fluoresces at 605 nm. The efficiency of seco-ZnPz in promoting the sensitization is due to high yields of both intersystem crossing and quenching. The quantum yields for the two processes, φ T ) 0.64 and φ ∆ ) 0.54, respectively, indicate that quenching of the triplet state of seco-ZnPz by ground-state oxygen is indeed the major deactivation pathway. The high quantum yield of triplet state formation could be promoted by the two carbonyl groups on the seco-ZnPz, as this group is well-known to promote intersystem crossing. 15 Conclusion The photoperoxidation of ZnPz proceeds via the attack of 1 O 2 on a peripheral pyrrole ring to produce seco-ZnPz. Once initiated, the reaction accelerates due to more efficient sensitization of the oxygen by the photoproduct, seco-ZnPz. As a consequence, the reaction proceeds autocatalytically with a second-order rate constant, the magnitude of which depends on the light intensity and on the concentration of dissolved oxygen. The photophysical characterization of the seco-ZnPz reveals a low fluorescence quantum yield and a high intersystem quantum yield. The triplet state lifetime is long (τ ) 81 µs in the absence of oxygen), allowing for efficient interaction with dissolved 3 O 2 to produce the active 1 O 2 , with a quantum yield of 0.54. This high value explains the efficiency of the photoperoxidation and also the autocatalytic mechanism. The use of coordinating solvents, such as DMF and pyridine, prevents the photooxidation process by inhibiting the efficiency of photosensitization by the seco-ZnPz. The photosensitized production of 1 O 2 by seco-ZnPz is very efficient which would make this dye extremely phototoxic and confirms the overall photooxidation as murder and not suicide. Acknowledgment

Terahertz radiation driven chiral edge currents in graphene

We observe photocurrents induced in single layer graphene samples by illumination of the graphene edges with circularly polarized terahertz radiation at normal incidence. The photocurrent flows along the sample edges and forms a vortex. Its winding direction reverses by switching the light helicity from left- to right-handed. We demonstrate that the photocurrent stems from the sample edges, which reduce the spatial symmetry and result in an asymmetric scattering of carriers driven by the radiation electric field. The developed theory is in a good agreement with the experiment. We show that the edge photocurrents can be applied for determination of the conductivity type and the momentum scattering time of the charge carriers in the graphene edge vicinity.Comment: 4 pages, 4 figure, additional Supplemental Material (3 pages, 1 figure

Intrinsic Terahertz Plasmons and Magnetoplasmons in Large Scale Monolayer Graphene

We show that in graphene epitaxially grown on SiC the Drude absorption is transformed into a strong terahertz plasmonic peak due to natural nanoscale inhomogeneities, such as substrate terraces and wrinkles. The excitation of the plasmon modifies dramatically the magneto-optical response and in particular the Faraday rotation. This makes graphene a unique playground for plasmon-controlled magneto-optical phenomena thanks to a cyclotron mass 2 orders of magnitude smaller than in conventional plasmonic materials such as noble metals.Comment: to appear in Nano Letter

Human metapneumovirus induces more severe disease and stronger innate immune response in BALB/c mice as compared with respiratory syncytial virus

BACKGROUND: Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are members of the Pneumovirinae subfamily of Paramyxoviridae and can cause severe respiratory disease, especially in infants and young children. Some differences in the clinical course of these infections have been described, but there are few comparative data on pathogenesis in humans and animal models. In this study, HMPV and RSV were compared for replication, pathogenesis and immune induction in BALB/c mice infected with equivalent inocula of either virus. METHODS: Viral titers in the lungs and in the nasal turbinates of mice were determined by plaque assay. Histopathological changes in the lungs as well as weight loss and levels of airway obstruction were monitored in the infected mice to record the severity of illness. Inflammatory cells recruited to the lungs were characterized by flow cytometry and by differential staining. In the case of natural killer cells, cytotoxic activity was also measured. Cytokine levels in the BAL were determined by cytometric bead array. RESULTS: RSV replicated to higher titers than HMPV in the lung and in the upper respiratory tract (URT), and virus elimination from the lungs was more rapid in HMPV-infected mice. Clinical illness as determined by airway obstruction, weight loss, and histopathology was significantly more severe after HMPV infection. A comparison of the cellular immune response revealed similar recruitment of T lymphocytes with a predominance of IFN-γ-producing CD8+ T cells. By contrast, there were obvious differences in the innate immune response. After HMPV infection, more neutrophils could be detected in the airways and there were more activated NK cells than in RSV-infected mice. This correlated with higher levels of IL-6, TNF-α and MCP-1. CONCLUSION: This study shows important differences in HMPV and RSV pathogenesis and suggests that the pronounced innate immune response observed after HMPV infection might be instrumental in the severe pathology

Risk stratification of Barrett's oesophagus using a non-endoscopic sampling method coupled with a biomarker panel: a cohort study

Background Barrett's oesophagus predisposes to adenocarcinoma. However, most patients with Barrett's oesophagus will not progress and endoscopic surveillance is invasive, expensive, and fraught by issues of sampling bias and the subjective assessment of dysplasia. We investigated whether a non-endoscopic device, the Cytosponge, could be coupled with clinical and molecular biomarkers to identify a group of patients with low risk of progression suitable for non-endoscopic follow-up. Methods In this multicentre cohort study (BEST2), patients with Barrett's oesophagus underwent the Cytosponge test before their surveillance endoscopy. We collected clinical and demographic data and tested Cytosponge samples for a molecular biomarker panel including three protein biomarkers (P53, c-Myc, and Aurora kinase A), two methylation markers (MYOD1 and RUNX3), glandular atypia, and TP53 mutation status. We used a multivariable logistic regression model to compute the conditional probability of dysplasia status. We selected a simple model with high classification accuracy and applied it to an independent validation cohort. The BEST2 study is registered with ISRCTN, number 12730505. Findings The discovery cohort consisted of 468 patients with Barrett's oesophagus and intestinal metaplasia. Of these, 376 had no dysplasia and 22 had high-grade dysplasia or intramucosal adenocarcinoma. In the discovery cohort, a model with high classification accuracy consisted of glandular atypia, P53 abnormality, and Aurora kinase A positivity, and the interaction of age, waist-to-hip ratio, and length of the Barrett's oesophagus segment. 162 (35%) of 468 of patients fell into the low-risk category and the probability of being a true non-dysplastic patient was 100% (99% CI 96–100) and the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 0% (0–4). 238 (51%) of participants were classified as of moderate risk; the probability of having high-grade dysplasia was 14% (9–21). 58 (12%) of participants were classified as high-risk; the probability of having non-dysplastic endoscopic biopsies was 13% (5–27), whereas the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 87% (73–95). In the validation cohort (65 patients), 51 were non-dysplastic and 14 had high-grade dysplasia. In this cohort, 25 (38%) of 65 patients were classified as being low-risk, and the probability of being non-dysplastic was 96·0% (99% CI 73·80–99·99). The moderate-risk group comprised 27 non-dysplastic and eight high-grade dysplasia cases, whereas the high-risk group (8% of the cohort) had no non-dysplastic cases and five patients with high-grade dysplasia. Interpretation A combination of biomarker assays from a single Cytosponge sample can be used to determine a group of patients at low risk of progression, for whom endoscopy could be avoided. This strategy could help to avoid overdiagnosis and overtreatment in patients with Barrett's oesophagus. Funding Cancer Research UK

Atomistic spin model simulations of magnetic nanomaterials

Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast laser-induced spin dynamics, exchange bias, and microstructural effects. Here we present the key methods used in atomistic spin models which are then applied to a range of magnetic problems. We detail the parallelization strategies used which enable the routine simulation of extended systems with full atomistic resolution

Depression and anxiety symptoms post-stroke/TIA:prevalence and associations in cross-sectional data from a regional stroke registry

BACKGROUND: Mood disorders are commonly seen in those with cerebrovascular disease. Literature to-date has tended to focus on depression and on patients with stroke, with relatively little known about post-stroke anxiety or mood disorder in those with transient ischaemic attack (TIA). We aimed to describe prevalence of depression and anxiety symptoms in stroke and TIA cohorts and to explore association with clinical and socio-demographic factors. METHODS: We used a city wide primary care stroke registry (Glasgow Local Enhanced Service for Stroke - LES). All community dwelling stroke-survivors were included. We described cross-sectional prevalence of depression and anxiety symptoms using the Hospital Anxiety and Depression Scale (HADS). Data on clinical and demographic details was collected and univariable and multivariable analyses performed to describe associations with HADS scores. We examined those with a diagnosis of 'stroke' and 'TIA' as separate cohorts. RESULTS: From 13,283 potentially eligible stroke patients in the registry, we had full HADS data on 4,079. Of the 3,584 potentially eligible TIA patients, we had full HADS data on 1,247 patients. Across the stroke cohort, 1181 (29%) had HADS anxiety scores suggestive of probable or possible anxiety; 993 (24%) for depression. For TIA patients, 361 (29%) had anxiety and 254 (21%) had depression. Independent predictors of both depression and anxiety symptoms were female sex, younger age and higher socioeconomic deprivation score (all p < 0.001). CONCLUSION: Using HADS, we found a high prevalence of anxiety and depression symptoms in a community-based cohort of patients with cerebrovascular disease

Epigenetic alterations differ in phenotypically distinct human neuroblastoma cell lines

<p>Abstract</p> <p>Background</p> <p>Epigenetic aberrations and a CpG island methylator phenotype have been shown to be associated with poor outcomes in children with neuroblastoma (NB). Seven cancer related genes (<it>THBS-1, CASP8, HIN-1, TIG-1, BLU, SPARC</it>, and <it>HIC-1</it>) that have been shown to have epigenetic changes in adult cancers and play important roles in the regulation of angiogenesis, tumor growth, and apoptosis were analyzed to investigate the role epigenetic alterations play in determining NB phenotype.</p> <p>Methods</p> <p>Two NB cell lines (tumorigenic LA1-55n and non-tumorigenic LA1-5s) that differ in their ability to form colonies in soft agar and tumors in nude mice were used. Quantitative RNA expression analyses were performed on seven genes in LA1-5s, LA1-55n and 5-Aza-dC treated LA1-55n NB cell lines. The methylation status around <it>THBS-1, HIN-1, TIG-1 </it>and <it>CASP8 </it>promoters was examined using methylation specific PCR. Chromatin immunoprecipitation assay was used to examine histone modifications along the <it>THBS-1 </it>promoter. Luciferase assay was used to determine <it>THBS-1 </it>promoter activity. Cell proliferation assay was used to examine the effect of 5-Aza-dC on NB cell growth. The soft agar assay was used to determine the tumorigenicity.</p> <p>Results</p> <p>Promoter methylation values for <it>THBS-1</it>, <it>HIN-1</it>, <it>TIG-1</it>, and <it>CASP8 </it>were higher in LA1-55n cells compared to LA1-5s cells. Consistent with the promoter methylation status, lower levels of gene expression were detected in the LA1-55n cells. Histone marks associated with repressive chromatin states (H3K9Me3, H3K27Me3, and H3K4Me3) were identified in the <it>THBS-1 </it>promoter region in the LA1-55n cells, but not the LA1-5s cells. In contrast, the three histone codes associated with an active chromatin state (acetyl H3, acetyl H4, and H3K4Me3) were present in the <it>THBS-1 </it>promoter region in LA1-5s cells, but not the LA1-55n cells, suggesting that an accessible chromatin structure is important for <it>THBS-1 </it>expression. We also show that 5-Aza-dC treatment of LA1-55n cells alters the DNA methylation status and the histone code in the <it>THBS-1 </it>promoter modifies cell morphology, and inhibits their ability to form colonies in soft agar.</p> <p>Conclusion</p> <p>Our results suggest that epigenetic aberrations contribute to NB phenotype, and that tumorigenic properties can be inhibited by reversing the epigenetic changes with 5-Aza-dC.</p